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Girard, Joshua James.
Feasibility of wastewater reuse for fish production in small communities in a developing world setting
h [electronic resource] /
by Joshua James Girard.
[Tampa, Fla] :
b University of South Florida,
Title from PDF of title page.
Document formatted into pages; contains 123 pages.
(M.S.E.V.)--University of South Florida, 2011.
Includes bibliographical references.
Text (Electronic thesis) in PDF format.
ABSTRACT: Eradicating poverty, malnutrition, and the burden of disease have been included as three of the major issues facing the world. The United Nation member countries, having set forth the Millennium Development Goals, have committed themselves to solving these problems. Two major factors which affect solutions to these problems are increasing water stress and implementing improved sanitation. Integration of tilapia aquaculture and reuse of wastewater has been suggested as a solution which addresses both of these factors. The objective of this study is to examine the feasibility, and explore the benefits and drawbacks, to implementing small community wastewater fed (WWF) aquaculture systems in the developing world. The water quality characteristics of treated effluent from nine wastewater treatment (WWT) plants were compiled from other studies. The concentration of total nitrogen in the effluent and the flow rate were of most importance, as they were used to calculate the nitrogen loading at each WWT plant. The nitrogen loading was then used to estimate the total pond size which could be supported by each WWT plant, the expected yearly yield for tilapia, and the percentage of the population who would benefit from provision of protein associated with the integration a fish farming system with the WWT plant. Results show that WWF, semi-intensive tilapia culture can provide 10 grams per day of dietary protein for 11% 52% of the population of the communities in this study when integrated with a community managed wastewater treatment system. To assess potential risks to human health, associated with WWF aquaculture, the level of fecal coliform (FC) contamination was compared to the standard set by the World Health Organization; less than 105 FC per 100 mL for reuse in fish ponds. The level of FC contamination in the WWT plant effluents ranged from 653 to 1.78 105 FC per 100 mL, exceeding this standard. Given the context, the level of fecal coliforms should not rule out integrated reuse and aquaculture as an option. The nutrients found in wastewater are valuable resources in tilapia culture; therefore, allowing their persistence through treatment for reuse, while optimizing wastewater treatment technologies for pathogen removal is an appropriate solution for small communities in developing countries for reducing poverty, malnutrition, and disease burden of waterborne illnesses.
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Mihelcic, James R.
x Environmental Engineering Engineering, Agricultural
t USF Electronic Theses and Dissertations.
Feasibility of Wastew ater Reuse for Fish Production in Small Communities in a Developing World Setting by Joshua James Girard A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering D e partment of Civil & Environmental Engineering College of Engineering University of South Florida Major Professor: James R. Mihelcic, Ph.D. Maya Trotz, Ph.D. Fenda Akiwumi Ph.D. Date of Approval : March 27, 2011 Keywords: Developing Country, Aquaculture, Water Reuse, Sanitation, Tilapia Copyright 2011, Joshua James Girard
ACKNOWLEDGEMENTS I would like to thank the farming families of Kanona, Central Province, Zambia for welcoming me into their homes and families: Edinah Kulul a, David and Nelly Mulenga, Joseph and Rhoda Chilulwe, Eva Kulula. For their endless support while working together in Zambia: Julia Milliken, Mwengele Katongo, A lec Briemann, Cleopher Bweupe. I would also like to thank the University of South Florida and Michigan Technological University for providing this incredible opportunity through the Masters International Program. Finally, I thank D r. James Mihelcic for his inspiring vision of how engineers can shape the world.
i TABLE OF CONTENTS LIST OF TABLES .............................................................................................................. iii LIST OF FIGURES ............................................................................................................ v LIST OF EQUATIONS ..................................................................................................... v ii ABSTRACT ..................................................................................................................... viii INTRODUCTION ............................................................................................................... 1 Study Objective and Hypothesis ........................................................................... 2 PR EVIOUS RESEARCH ................................................................................................... 5 The Relationship of Aquaculture to the Millennium Development Goals ............... 5 Wastewater Fed Aquaculture ................................................................................ 7 Risks to Human Health in Wastewater Fed Aquaculture ..................................... 10 Studies on Wastewater Fed Aquaculture ............................................................ 18 Protein Requirements for Human Beings ............................................................ 19 FISH FARMING SYSTEMS ............................................................................................ 23 Semi -Intensive Tilapia Farming System Overview .............................................. 23 RAP Standard Pond ................................................................................ 2 4 Environmental Requirements .............................................................................. 30 The Bloom ........................................................................................................... 31 Supplemental Feeding ........................................................................................ 36 Farm Integration .................................................................................................. 38 Expected Yields ................................................................................................... 38 TREATMENT PLANT CHARACTERISTICS AND LOCATIONS OF CASE STUDIES USED TO PROVIDE WASTEWATER CHARACTERISTICS ................... 42 Sapecho .............................................................................................................. 44 San Antonio ......................................................................................................... 45 South Africa ......................................................................................................... 45 Tanzania .............................................................................................................. 45 Arizona ................................................................................................................ 46 Zimbabwe ............................................................................................................ 46 Honduras ............................................................................................................. 47 Argentina ............................................................................................................. 47
ii METHODS ...................................................................................................................... 48 Nitrogen Loading, Pond Area, and Evaporation .................................................. 49 Nitrogen in Human Urine ..................................................................................... 51 Expected Yields and Number of Diets Affected by Fish Ponds ........................... 52 RE SULTS ........................................................................................................................ 55 Nitrogen Loading, Pond Area, and Evaporation .................................................. 55 Expected Yields and Number of Diets Affected by Fish Ponds ........................... 60 Evaluating Other Environmental Requirements .................................................. 62 DISCUSSION AND CONCLUSIONS .............................................................................. 67 Discussion ........................................................................................................... 67 Future Research .................................................................................................. 69 Conclusion ........................................................................................................... 72 LIST OF REFERENCES ................................................................................................. 74 APPENDICES ................................................................................................................. 77 Appendix A: Summary of Water Recycling Guidelines and Mandatory Standards in the U.S. and Other Countries .................................... 78 Appendix B: Considerations for National Wastewater and Excreta Use Policies Presented in the WHO Report on Wastewater Reuse in Aquaculture ..................................................................... 79 Appendix C: Total Protein Supply by Continent and Major Food Group ............. 80 Appendix D: Characteristics of Commonly Cultured Tilapia Species in Zambia ............................................................................................ 81 Appendix E : Composition of Fertilizer Used in Semi -I ntensive Aquaculture ....... 84 Appendix F: Guide to Supplemental Feeding and Formulating Tilapia Feeds .............................................................................................. 87 Appendix G: Nutrients Found in Human Excrement ............................................ 96 Appendix H: Equation for the Modeling of Fecal Coliform Removal in Lagoons .......................................................................................... 97 Appendix I: World Health Organization Reported Safe Levels of Protein Intake for Adult Men and Women ................................................... 98 Appendix J: Concise Rural Aquaculture Promotion (RAP) Program Pond Construction Manual ....................................................................... 99 ABOUT THE AUTHOR ....................................................................................... End Page
iii LIST OF TABLES Table 1 Contribution of fisheries to the MDGs in Africa, r eprinted with permission from Simon Heck et al. (2007) ........................................................ 6 Table 2 Health-based targets for waste-fed aquaculture (WHO, 2006) ....................... 14 Table 3 Chronic criteria action levels for copper, zinc, and cadmium in freshwater at various levels of water hardness (US EPA, 2002b) ................. 18 Table 4 Treated wastewater characteristics for wastewater effluent entering farming system east of Kolkata, India (Bunting, 2006) ................................... 19 Table 5 Physical characteristics of a standard pond promoted by the Rural Aquaculture Promotion (RAP) program .......................................................... 27 Table 6 Environmental factors affecting tilapia growth and mortality (El -Sayed, 2006) ............................................................................................................... 31 Table 7 Yearly pond yields in weight of fish harvested for various semi intensive tilapia cultures .................................................................................. 40 Table 8 Flow rate and nitrogen concentration of wastewater at each case study location ............................................................................................................ 44 Table 9 Flow rate, nitrogen concentration, and nitrogen loading at each plant ............ 56 Table 10 Comparison of nitrogen loading in wastewater tr eatment plant effluent and nitrogen loading expected from human urine ......................................... 57 Table 11 Estimated total area of fish ponds at each wastewater treatment plant ........ 58 Table 12 Flow rate, estimated amount of water evaporated daily from pond system and percentage of flow l ost to evaporation ....................................... 59 Table 13 Expected aquaculture system yield, number of tilapia servings produced each year, and the percentage of the population affected by aquaculture integration .................................................................................. 61 Table 14 Wastewater characteristics which could affect tilapia growth at each wastewater treatment plant ........................................................................... 64
iv Table A Characteristics of reproduction, feeding, and markings for commonly cultured tilapia species in Zambia (Froese & Pauly,2010) ..................... ...... 81 Table B Supplement feeds: components and point values ......................................... 87 Table C Nutrients found in human feces and urine .................................................... 96
v LIST OF FIGURES Figure 1 Schematic showing the various products of aquaculture systems ................... 9 Figure 2 Global per capita supply of fish to global food supply (average 20032005) ............................................................................................................. 20 Figure 3 Global contribution of fish to animal protein supply (average 20032005) ............................................................................................................. 21 Figure 4 a) Schematic of a semi -intensive fish farming system showing a system of eight ponds and good placement within a stream valley, b) cross section of a valley utilized for a fish pond system ................................ 26 Figure 5 Cross section view of a Rural Aquaculture Promotion (RAP) standard pond ............................................................................................................... 28 Figure 6 Plan view of a Rural Aquaculture Promotion (RAP) standard pond showing typical layout of inlets, outlets, furrow, compost bin, and overall orientation in the valley ...................................................................... 29 Figure 7 Sch ematic showing various inputs for growth of phytoplankton to support the growth of fish .............................................................................. 33 Figure 8 Yields in metric tons per hec tare per year for various semi -intensive tilapia cultures (El -Sayed, 2006; Bweupe, 2011) .......................................... 39 Figure 9 Flowchart of calculations for nitrogen loading, estimated total pond area, amount of water evaporated, estimated yearly pond yield, number of tilapia servings, number of persons affected ................................ 48 Figure A Nile Tilapia Oreochromis niloticus ................................................................ 82 Figure B Redbreasted Bream Tilapia rendalli ............................................................. 82 Figure C Greenheaded Bream Oreochrom is macrochir .............................................. 83 Figure D Threespotted Bream Oreochromis andersonii ............................................... 83 Figure E Calculation for flow rate from a furrow ......................................................... 99 Figure F Measuring the slope of a valley .................................................................. 1 01 Figure G Methods for testing soil ............................................................................. 103 Figure H Schematic showing interior and exterior slopes of a RAP standard pond ......................................................................................... 1 06
vi Figure I Typical setup of an overflow pipe ................................................................. 1 07 Figure J Layout for staking of a fish pond and its inner box ..................................... 109 Figure K Photo of pond construction after completion of the inner box ..................... 110 Figure L Photo showing the completion of pond slope construction and leveling of dike walls ................................................................................... 110
vii LIST OF EQUATIONS Equation 1 Nitrogen loading ......................................................................................... 49 Equation 2 Nitrogen loading, Sapecho ......................................................................... 49 Equation 3 Pond area .................................................................................................. 50 Equation 4 Pond area, Sapecho .................................................................................. 50 Equation 5 Volume of water evaporated from a fish pond system ............................... 50 Equation 6 Volume of water evaporated from a fish pond system, Sapecho ............... 51 Equation 7 Nitrogen excreted in urine per day by a population ................................... 52 Equation 8 Nitrogen excreted in urine per day by a population, Sapecho ................... 52 Equation 9 Pond yield in metric tons of fish per year ................................................... 52 Equation 10 Pond yield in metric tons of fish per year, Sapecho ................................. 53 Equation 11 Servings of tilapia per year from yield ...................................................... 53 Equation 12 Servings of tilapia per year from yield, Sapecho ...................................... 53 Equation 13 Number of persons diets affected by integration of wastewater fed aquaculture .............................................................................................. 54 Equation 14 Number of persons diets affected by integration of wastewater fed aquaculture, Sapecho .............................................................................. 54 Equation A Estimation of fecal coliform removal in lagoons ...................................... 97
viii ABSTRACT Eradicating poverty, malnutrition, and the burden of disease have been included as three of the major issues facing the world. The United Nati on member countries, having set forth the Millennium Development Goals, have committed themselves to solving these problems. Two major factors which affect solutions to these problems are increasing water stress and implementing improved sanitation. Integr ation of tilapia aquaculture and reuse of wastewater has been suggested as a solution which addresses both of these factors. The objective of this study is to examine the feasibility, and explore the benefits and drawbacks, to implementing small community wastewater fed (WWF) aquaculture systems in the developing world. The water quality characteristics of treated effluent from nine wastewater treatment (WWT) plants were compiled from other studies. The concentration of total nitrogen in the effluent and the flow rate were of most importance, as they were used to calculate the nitrogen loading at each WWT plant. The nitrogen loading was then used to estimate the total pond size which could be supported by each WWT plant, the expected yearly yield for tilapi a, and the percentage of the population who would benefit from provision of protein associated with the integration a fish farming system with the WWT plant. Results show that WWF, semi -intensive tilapia culture can provide 10 grams per day of dietary protein for 11% 52% of the population of the communities in this study when integrated with a community managed wastewater treatment system. To assess potential risks to human health, associated with WWF aquaculture, the level of fecal coliform (FC) contami nation was compared to the standard set by the World Health Organization; less than 105 FC per 100 mL for reuse in fish ponds. The level of FC
ix contamination in the WWT plant effluents ranged from 653 to 1.78 105 FC per 100 mL, exceeding this standard. G iven the context, the level of fecal coliforms should not rule out integrated reuse and aquaculture as an option. The nutrients found in wastewater are valuable resources in tilapia culture; therefore, allowing their persistence through treatment for reuse, while optimizing wastewater treatment technologies for pathogen removal is an appropriate solution for small communities in developing countries for reducing poverty, malnutrition, and disease burden of waterborne illnesses.
1 INTRODUCTION At the turn of the millennium the 189 countries of the United Nation s (UN) made a commitment to the improvement of the lives of the worlds poor. The UN outlined eight goals to be reached by the year 2015. Among these eight Millennium Development Goals (MDG) the member states of the UN have dedicated themselves to the eradication of extreme poverty and hunger (Goal 1 ) and assurance of environmental sustainability (Goal 7 ) (UN, 2000) Aquaculture the farming of aquatic plants or animals, can play an important role in achieving both of these goals. It can also contribute indirectly to the achievement of the other goals : e.g., improving maternal and child health, combating diseases such as HIV/AIDS, and achieving universal primary education. Aquaculture has a long history in many parts of the world. In Zambia, extraction of fish from rivers and streams, even traditional methods of fish farming, are widely practiced. Generally, aquaculture in Zambia has been an extensive farming practice and most families keeping traditional style fish ponds have done so for subsistence. Increasing local demand has made catching, transporting, and selling of fish in urban areas a very important economic activity for many families. Export of fish and fish products accounts for over 25% of the total agricultural export in 14 African nations (Heck et al., 2007) By investing in aquaculture these countries can reduce poverty by adding jobs and grow ing their economies. Investment in aquac ulture can occur at all levels of the economy, from rural farmers to larger commercial farms In the same way that aquaculture can span all levels of economic development, it can also
2 be integrated with solutions used in other sectors. For example, this integration could combine irrigation systems and wastewater treatment (WWT) systems, or the nutrient rich effluents from fi sh ponds and vegetable crops which require nutrients and reliable irrigation. Aquaculture education can also be integrated into schoo l curriculums or financing programs for womens groups and co operatives The sections of MDG 1 seek to reduce poverty by increasing incomes, and decreasing unemployment (UN, 2000) Section C of MDG 1 focuses on hunger. Rural aquaculture promotion increases the capacity of rural farmers not only to increase their family income, but also to reliably produce a food like fish, which is rich in protein. Even if families do not use aquaculture for economic gain, the benefits of having a reliable source of protein will improve the familys health, helping to achieve Goal 1 There are many benefits of integrating aquaculture with other agricultural and environmental efforts. The integration of aquaculture into traditional farming practices such as keeping livestock and gardening, can raise the productivity per unit of land area by 28 percent (The World Fish Center, 2007) It is likely that integration could also yield similar results for water productivity. Aquaculture systems that reuse wastewater or pond effluents could help to reduce water stress. Study Objective and Hypothesis The objective of this study is to examine the feasibility and explore the benefits and drawbacks to implementing wastewater fed (WWF) aquaculture systems in the developing world. Some previous studies have investigated at wastewater agriculture and aquaculture as a productive treatment method (Edwards, 1992) However, a general approach to WWF agriculture lacks detail regarding the unique challenges and benefits of reusing wastewater for fish production. Other studies have approached WWF
3 aquaculture directly, foc usi ng on nutrient recovery, economic feasibility, or institutional support for WWF fish farming (Bunting, 2006; Mara et al., 1993) H owever, the most detailed of these studies focused on the theoretical renovation of a l arge wastewater treatment (WWT) plant serving an existing aquaculture system 550,000 cubic meters per day (Bunting, 2006) The studys author spent two years in Zambia as a Peace Corps volunteer, as part of the Masters International Program in Civil and Environmental Engineering ( http://cee.eng.usf.edu/peacecorps/ ) and the Rural Aquaculture Promotion (RAP) program He participated in nine weeks of cultural, language (Bemba), aquaculture, and HIV/AIDS training. Follow ing training he moved to his host community where he conducted farmer evaluations, fish farming workshops, farmer site visits, and community based HIV/AIDS education. His direct observation of fish farming practices in Zambia serve d as a basis for some assumptions made in this study and for recommendations made for future research. This study will use data obtained from various WWT plant case studies, within a developing world setting, to investigate the feasibility of integrating wastewater reuse with fish pond aquaculture that would support a portion of a communitys protein requirements The study will specifically examine whether the nutrient loading associated with effluent from small community wastewater treatment systems found in the developing wor ld is sufficient to support fish growth. The study will also address whether reusing treated wastewater effluent to produce fish results in the protection of human health. The study will assess the following two hypotheses :
4 1. Integrating fish aquacultur e with small WWT facilities will provide sufficient amounts of water and nutrients to farm fish and provide a significant amount of a communitys protein intake. 2. Wastewater from small scale WWT plants can be safely reused in fish pond aquaculture.
5 PREVIO US RESEARCH The Relationship of A quaculture to the Millennium Development Goals The integration of aquaculture into traditional farming practices can be used to directly address MDG Goals 1 and 7 set forth by the UN in 2000. The solutions which will achieve Goal 1 to eradicate extreme poverty and hunger, will involve aquaculture. Already fish products contribute substantially to the economies and diets of many communities in developing countries Current capture methods from fr eshwater have depleted natural supplies, and aquaculture could serve as a way to fill the existing gap between supply and demand (Heck et al., 2007). Growth of the industry coul d, especially among rural small scale farmers, engage these families in an economic sector which has great potential for growth. By promoting indigenous species and by integrating fish farming with WWT fish farming programs can also have a direct impact on achieving Goal 7 to ensure environmental sustainability. Natural fish stocks are already under gr eat stress from current demand (Heck et al., 2007) B y promoting semi -intensive aquaculture, some of this stress could be relieved, especially where natural stocks have collapsed or have been regulated. Integrated WWF aquaculture can play a role in reducing the number of people without access to improved sanitation. Increasing capacity to treat wastewater provides room for expansion of water treatment facilities that will be designed to supply water to reuse applications, especially if the WWT facilities have other benefits like food production and economic incentives (Bunting, 2006)
6 Table 1 summarizes these direct links to targets in MDG Goals 1 and 7 and the indirect benefits to all of the other Millennium Development Goals in Africa. The indirect benefits are generally related to the health benefits and increased income associated with families engaged in aquaculture. Table 1 Contribution of fisheries to the MDGs in Africa, reprinted with permission from Simon Heck et al. (2007) MDG Objectives Contribution of Fisheries and Aquaculture Goal 1 Eradicate extreme poverty and hunger Income to 10 million poor households through fish capture, processing, trade and allied industries Food security for 200 million poor, strengthened through affordable, high quality food Goal 2 Achieve universal primary education Indirect benefits through increased income for women and improved health of children Goal 3 Promote gender equality and empower women Women strongly engaged in artisanal processing and trade, gaining income and power Goal 4 Reduce child mortality Fish nutrients (such as fatty acids) improve neural development in the fetus and lower the risk of low birth weight, key factors in child mortality Child nutrition improved through supply of protein and minerals Goal 5 Improve maternal health Improved nutritional status of women Goal 6 Combat HIV and AIDS, malaria, and other diseases Fishing communities are among the hardest hit by HIV and AIDS; progress here is vital for combating the pandemic regionally Affordable proteins and micronutrients help mitigate the impacts of disease among the poor and are essential for the effective use of drugs Incomes form fisheries and aquaculture enable the poor and HIV and AIDS sufferers in particular to obtain badly needed nutrition and income and thus access further services
7 Table 1 (Continued) Goal 7 Ensure environmental sustainability Good fisheries gov ernance, such as through regulated small scale and large scale aquaculture can contribute to preserving biodiversity and fragile habitats throughout the continent Goal 8 Develop a global partnership for development Fish is the leading export commodity helping African nations to improve their trade balance, and offering opportunities for developed countries to promote and adopt good trading practices from the outset The Abuja Declaration on Sustainable Fisheries and Aquaculture in Africa and the pan-Afri can Fisheries and Aquaculture Program by the African Union are strengthening regional cooperation and international partnerships in science and capacity building Wastewater Fed Aquaculture Wastewater fed (WWF) aquaculture systems utilize wastewater to irrigate and supply nutrients to aquatic species. Junge (2001) view s WWF aquaculture as a part of an integrated method to treat wastewater to acceptable levels of coliforms and other requirements. This integration of wastewater treatment and productive aquaculture has been called a rational design by Bunting (2006) A rational design approach views water treatment and aquaculture as a single system to be optimized for maximum fish production and was tewater treatment. The use of wastewater in agriculture is not a new idea. Wastewater was used in 19th century Europe to irrigate crops at the periphery of the continents growing cities (Ensink and van der Hoek, 2007). This served not only to irrigate and fertilize crops, but also as an environmental buffer between the raw sewage and the bodies of water which the waste would otherwise be dumped. As the land became more coveted for other forms of
8 development, along with the invention of chemical fertilizer s and traditional WWT plants the practice was abandoned. Currently wastewater is reused for agriculture in developed and developing countries around the world. Specifically reuse for fish aquaculture is occurring on a rather large scale near Kolkata, Ind ia (Bunting, 2006) However, wastewater is also unintentionally reused from polluted surface waters where wastewater is released directly to surface waters (Edwards, 1992) As water stress becomes an increasingly important concern in many places, more people are exploring the option of WWF aquaculture as part of an integrated wastewater treatment and agricultural scheme (En sink 2007) Fish farming falls within the many options which exist for productive wastewater treatment designs. Other engineers and scientists have noted the wide range of aquaculture options which exist for the WWF aquaculture systems (Junge, 2001). Figure 1 presents these various aquaculture products :
9 Figure 1 Schematic showing the various products of aquaculture systems Adapted from (Junge, 2001) Wastewater treatment in developed countries has many varied obje ctives all aimed at protecting the well -being of a nations residents and the state of the environment. It has been suggested that the main goal for wastewater treatment in developing countries should be the removal of pathogens, since the disease burden for waterborne illness is the largest concern associated with wastewater (Oakley 2005) By combining this WWT priority with aquaculture, the nutrients and organic matter in wastewater can be viewed as a resource rather than a waste product to be treated (Cavallini, 1996) The financial Productive Aquaculture Food and Feed Products Non -Food Products Human Foods Animal Feeds Raw Materials Luxury Products Animals Plants Phytoplankton High protein floating plants Zooplankton Fibers for furniture Cellulose for paper Fertilizer Renewable energy sources Pearls Ornamental plants Ornamental fish Mussels Prawns Crayfish Fish Algae Water spinach Water chestnuts Water nuts Hydroponic vegetables and herbs
10 and health benefits (from increased protein supply) add to the incentives for building and maintaining wastewater treatment systems (Edwards, 1992) WFA sy stems can be separated into three groups: first, productive ponds receiving ra w wastewater; second, productive ponds receiving wastewater treated by primary treatment system; and productive ponds receiving wastewater treated for pathogens (Cavallini, 1996) This study focuses on the third group, productive ponds receiving wastewater treated for pathogens Due to the health risks of working directly with raw wastewater in fish ponds and the water quality targets proposed by the W orld Health Organization ( WHO ), direct use of raw wastewater is not considered. Since lagoon based systems are promoted for use in small communities in the developing world, the study focused on lagoon systems. Risks to Human Health in Wastewater F ed Aquaculture With increasing water stress around the globe, the interest for reuse of wastewater has garnered attention. Many uses for water do not require drinking water quality; for example: irrigation, toilet flushing, cleaning, industrial reuse and environmental enhancement (Jamwal and Mittal, 2010) The reuse of wastewater for production of food for humans poses obvious questions about the risk to human health. What quantities of pathogens should be tolerated for use in agriculture? What risks do these levels pose to those who work in waste water agriculture? How should the policies be enforced? Governments have taken various approaches to the regulations set to ensure that the reuse of wastewater is safe. A sample of these regulations for U S. s tates and other countries is presented in Appendix A. The approach taken to wastewater reuse varies greatly between developed and developing nations. The United States Environmental Protection Agency takes a conservative approach, stating that wastewater r euse should
11 pose no risk of infection (Ensink and van der Hoek, 2007) In contrast, institutions such as the International Water Management Institute, whose work focuses on poor communities in developing countries try to balance the benefits and risks of wastewater reuse. The WHO takes a stance somewhere between them requiring that there should be no additional cases of infection, but also recognizing that different countries face their own unique situation (Ensink and van der Hoek, 2007) In 2006, the WH O revised its guidelines on wastewater reuse. However it stood by its earlier guidelines for wastewater use in aquaculture. Some debate has occurred about the 2006 revision of the WHO guidelines for wastewater use in agriculture from those established in 1989. While some argue that relaxation of the WHO guidelines could send the wrong message to prac ti tioners and potentially increase disease risk. It is more likely recognition of the reality of wastewater reuse, especially in developing countries. Each country must take into account the current wastewater reuse practices in their country and asses what kind of policy is appropriate for their nation (WHO, 2006) A summary of these considerations is provided in Appendix B. The fact that the WHO has asked local governments to adopt guidelines which suit local conditions is paramount to finding solutions for the developing world. Diarrheal diseases already place an incredible burden on global health. As engineers we do not want to increase this burden. However, we must recognize that poor sanitation is the status quo in many communities. To deny access to wastewater because it does not meet requirements that have been deemed appropriate in the United States does not improve the overall situation of the people who choose to use that water. For many untreated wastewater is the only reliable source of water for irrigation (IWMI, 2006) and for far more polluted surface waters are the best option for irrigation. It is estimated that less
12 than 20% of wastewater is treated worldwide and 3.5 to 20 million hectares is irrigated with wastewater or waste contaminated river water (Scott et al., 2004; IWMI, 2006). This argument is not to be used as an excuse for designing systems that may increase health risks. Rather, l ooking at the current situation and finding a solution that will be economically, social, and environmentally sustainable is the ultimate goal. Currently, the WHO states that the geometric mean for fecal coliforms should be no gr eater than 1, 000 per 100 mL of wastewater for crops consumed uncooked. This was relaxed from a geometric mean of 100 colifor ms per 100 mL used previously (Ensink and van der Hoek, 2007) The WHO report also urges local governments to adopt guidelines which suit local conditions (Ensink and van der Hoek, 2007) It is important to consider health impacts of these systems especially the impacts on those who work at wastewater fed farming systems It is also important to consider the risk associated with consuming fish produced in these systems. In creating guidelines the WHO had few case studies to use in determining suggested guidelines for allowable levels of fecal coliforms and other contaminants, as there has been little study of wastewater fed aquaculture. The risks associated with WF F aquaculture can be divided into two categories: 1) those which may directly affect workers at the site and 2) those that may affect the consumers of the fish. Risks to the consumers of fish may be due to accumulation of pathogenic bacteria on the skin of fish, in their gills, and in the intestines. These risks may be increased if the fish live in a particularly stressful environment due to overstocking or low dissolved oxygen (WHO, 2006) Trematodes may also pose a health threat if host species, such as aquatic snails, are present in the system. Tests to verify the absence of trematode eggs should be conducted and proper pond maintenance should be followed to combat the survival of host species in the ponds The risks pos ed by microbial pathogens can generally be
13 avoided by proper cleaning of the fish gut and cooking. The community and workers should be aware of the risks associated with WWF aquaculture. For example, workers should wear shoes to avoid infection by hookworm and the community should not use the pond water for drinking or allow children to swim in the ponds (WHO, 2006) One approach for evaluating WWF aquaculture systems is to set guidelines based on health based targets. Health based targets suggested by the WHO are found in Table 2.
14 Table 2 Health-based targets for waste-fed aquaculture (WHO, 2006) Exposed Group Hazard Health-based target Health Protection Measure Consumers, workers and local communities Excreta -related pathogens 10-6 DALY Wastewater treatment Excreta treatment Health and hygiene promotion Chemotherapy and immunization Consumers Excreta -related pathogens 10-6 DALY Produce restriction Waste application/timing Depuration Food handling and preparation Produce washing/disinfection Cooking foods Food borne trematodes Absence of trematode infections Chemicals Tolerable daily intakes as specified by the Codex Alimentarius Commission Workers and Local Communities Excreta -related pathogens 10-6 DALY Access control Use of personal protective equipment Disease vector control Intermediate host control Access to safe drinking water and sanitation at aquacultural facilities and in local communities Reduced vector contact (insecticidetreated nets, repellents) Skin irritants Absence of skin disease Schistosomes Absence of schisto somiasis Vector -borne pathogens Absence of vector -borne disease These targets are based upon a standard metric of disease. For these targets DALYs are used. DALYs are disability adjusted life year s ; one DALY represents one year lost to
15 ill-health, disability or early loss of life. Using health-based targets can help policy makers and prac ti tioners to evaluate the risks associated with WWF aquaculture; however they can be difficult to apply when designing a WWF aquaculture system. Performance targets are simpler to use and should be used at threeto six -month intervals to evaluate the risk associated with consumption of fish which is always eaten cooked (WHO, 2006) However, few studies have been done that link expected DALYs to microbial performance targets for wastewaters intended for reuse in aquaculture. Based on limited information, the WHO has settled on a geometric mean of 104 fecal coliforms (FC) per 100 mL of fish pond water and less than one helminth egg per liter (arithmetic mean) (WHO, 2006) Influent to the pond may have a geometric mean of 105 FC U per 100 mL to take into account the effects of pathogen removal which occur in the fish pond once the wastewater enters the pond (WHO, 2006) This is consistent with the CEPIS report, studying WWF ponds in Peru, which concluded that effluents from wastewater stabilization ponds containing 105 FC U per 100 mL were appropriate for reuse in aquaculture (Cavallini, 1996) Other potentially hazardous constituents, chemicals such as mercury and pesticides are generally of little concern in WWF aquaculture. These toxins do have the potential to bioaccumulate. However, fish should be regularly harvested, so the period in which bioaccumulation may occur is relatively short. Therefore, the expectation is that levels of potential toxins would be low enough to be considered safe for human co nsumption (WHO, 2006) It should be noted that most studies, including this paper and the WHO report, do not addres s the reuse of industrial wastewaters for aquaculture. Due to the short grow out period for tilapia, four to six months, the accumulation of potentially harmful substances such as mercury, was not a major component of the RAP program. Since it was assumed that unless these substances are present in the
16 water at excessive concentrations, they would not be present in fish at harmful levels. Also the wastewater to be reused, from small community waste treatment systems, is assumed to come from domestic waste which is less likely to contain harmful toxins associated with industrial wastes. One study found that farmers seller s and consumers i n Ghana were unaware of the dangers of mercury contamination from local small scale mining (Tschakert, 2010) This suggests that local governments and aquaculture promotion programs should include educational components to create awareness of the dangers of mercury poisoning. The Tschakert study also found that fish from less contaminated waters had higher demand, so the threat to public health may be smaller than suggested by panicked messages about contamination at the mining sites. Phytoplankton accumulates heavy metals. How ever, the contaminants do not appear to be readily accumulated by fish that feed on the algae. (Edwards, 1992) However, other studies have found fish grown in treated wastew ater to exceed the WHO guidelines for safe consumption of fish (Bhattacharyya et al., 2010) The WHO guideline of 1.6 g per gram bodyweight (of person) per week for methylmercury is set to avoid potential harmful effects of a developing fetus. A person of 50 kg could consume up to 80 g of methylmercury a week without exceeding this limit (WHO, 2007) The main methods for removing heavy metals before reuse is to allow plankton to settle out into the sludge layer or use chemical methods such as precipitation. Once these compounds are in the pond heavy metal uptake by fish and plankton is influenced by their concentration and the pH of the water Lower pH has been shown to increase the accumulation of methylmercury in tilapia (Wang et al., 2010)
17 For reuse of domestic wastewater there is not much concern with contamination of heavy metals as compared to direct use of surface waters (Edwards, 1992) However if there is any potential that wastewater is mixed domestic and industrial testing and monitoring is essential to ensure there is no threat to public health. The United States Environmental Protection Agency (US EPA) has set action levels for the concentration of copper, zinc, and cadmium in water. These action levels are presented in Table 3. If the metal concentrations exceed these action levels for a given water hardness measures must be taken to ensure that the quality of fish is not harming the health of its consumers The fact that the action levels vary with water hardness shows that the threat posed by heavy metals and other chemicals depends very much on the other water chemistry factors, not solely on the compounds concentrations in water. Therefore, the negative effects of heavy metals and toxins on fish quality s hould be evaluated for each WWF aquaculture system
18 Table 3 Chronic criteria action levels for copper, zinc, and cadmium in freshwater at various levels of water hardness (US EPA, 2002b) Hardness (mg/L as CaCO3) 500 100 10 1 Copper ( g/L) 35 9 1.3 0.18 Zinc ( g/L) 460 120 17 2.4 Cadmium ( g/L) 0.75 0.25 0.049 0.01 Studies on Wastewater Fed Aquaculture Few studies have focused specifically on integrating wastewater reuse with fish farming in the developing world. Two studies identified from India (Bunting, 2006; Mara et al., 1993) use the existing large scal e WWT and fish farming system east of Kolkata as a starting point for their analysis. These studies present one perspective for designing a wastewater reuse and aquaculture system; however, they differ in focus from this study. The characteristics of the WWT system used in the Peru study (Cavallini, 1996) did not include data for the average flow rate or nitrogen concentration in the treated wastewater. Both of the India studies aimed to find the potential benefits of renovating the existing pond system, making it more productive and safer for workers and fish consumers. The ponds were mixed cultures of tilapia and carp. The entire system constitutes about 3,000 hectares of fish ponds fed by 555,000 cubic meters per day of treated wastewater. Wastewater characteristics for treated wastewater entering the pond are presented in Table 4 However, the actual level of fecal coliform (FC) contamination was not measured, but estimated using a model for FC removal.
19 Table 4 Treated wastewater characteristics for wastewater effluent entering farming system east of Kolkata, India (Bunting, 2006) Flow Rate 6,366 L/s Nitrogen Concentration 50 mg/L Fecal Col iforms per 100mL (estimated, not measured) 380 BOD Loading 6 kg/ha day The study in Peru (Cavallini, 1996) was an experimental fish farm studied over the course of two years. The study found that the dispersion flow model was appropriate for modeling the levels of bacteria in its s tabilization ponds and recommended that model be used when designing ponds to meet a permissible level of bacteria. It also supported the WHOs suggestions for guidelines of acceptable levels of fecal coliforms in pond influent and pond water based on the quality of fish harvested from the studys ponds It also suggested that aquaculture ponds operate with a loading of biochemical oxygen demand (BOD) of 10 to 20 kg per hectare per day. Protein Requirements for Human Beings According to a joint report by the WHO, FAO, and the United Nations University, an adult weighing 60 kilograms should consume 50 grams of protein a day. In some countries fish constitutes up to 70% of the animal protein consumed; i n Africa over 200 million people eat fish regularly (Heck et al., 2007) Figure 2 shows the per capita intake of fish in kilograms per year. As shown in Figure 3 fish accounts for more than 20% of animal protein in the diets of many African countries, yet the supply of fish is low compared to many countries in Europe, North America, and East and Southeast Asia.
20 This suggests that many countries, especially where protein consumption is low, have cultures which are already accus tomed to preparing and eating fish. Increasing the total dietary protein intake by increasing the supply of fish is an acceptable method for decreasing malnutrition. Figure 2 Global per capita supply of fish to global food supply (average 2003-2005) Reproduced with permission from the Food and Agriculture Organization of the United Nations (2009, p. 62)
21 Figure 3 Global c ontribution of fish to animal protein supply (average 2003-2005) Reproduced with permission from the Food and Agriculture Organization of the United Nations (2009, p. 62) However, there are other sources of dietary protein besides fish and meat. Africa consumes the least protein daily per capita, approximately 60 grams per day (FAO, 2009) ; Appendix C presents the total supply of dietary pr otein by food group across six world regions This actually meets the dietary guidelines for a 60 kilogram adult, but does not take into account the inequalities of protein consumption across the continent. The countries in which daily consumption of fish protein is greater than ten grams per person are coastal countries which have a long history of ocean fishing: e.g. Norway, Iceland, Japan, and the Philippines. Based on the data for current sources of protein for various world populations depicted in Figure 3 one would expect that fish would account for no more than 10 grams a day
22 in communities which introduce fish farming as part of a food security or economic development plan. A typical serving of fish according to the United States Department of Agri culture is 3 ounces or about 85 grams (USDA 2006) This is also about the size of one harvested fish in a Zambian fish farm
23 FISH FARMING SYSTEMS Semi -Intensive Tilapia Farming System Overview The Rural Aquaculture Promotion (RAP) program is a joint venture between the United States Peace Corps (PC) and the Zambian government. Rural Aquaculture Promotion (RAP) was developed in 1996 by Peace Corps Zambia in response to a request from the Department of Fisheries (DoF) for human resource assistan ce in the aquaculture sector. The purpose of RAP is to help rural families and groups to address their livelihood needs, including HIV/AIDS mitigation, by operating integrated aquaculture as small business ventures that are supported by effective fish far mer organizations (USDS, 2011). The project coordinators have developed various recommendations for the construction and management of semi -intensive tilapia farming systems. The RAP standard fish pond and farming strategy is intended for rural farming families and co-operatives of rural farmers in Zambia. Utilization of local resources is very important in this context since external inputs such as special digging tools, manufactured fertilizers, commercial feeds, fishing nets, and pipes can be relatively expensive and cost-ineffective. Most communities host three generations of RAP volunteers. The service of each volunteer builds upon the progress of the previous. Earlier volunteers focus on cultural acclimation of the host community to working with an Am erican and the goals of the PC and the RAP program. This is followed by the identification of project farmers who have ponds or would like to build ponds. This is followed by the construction of ponds teaching of basic management, stocking, and harvesting concepts. Marketing, business
24 management, co-operative development, and farm integration are introduced on demand and usually after a base of model farmers are identified with in the communities. RAP Standard Pond The RAP standard pond is the ideal pond for a beginning fish farmer. However, this pond design is by no means the only suitable pond, especially since every farmers situation differs Often the pond design is modified to accommodate the land and water supply. The RAP program also promotes three s pecies of native tilapia which are detailed in Appendix D Nile tilapia (Oreochromis niloticus ) is also included because it is the most commonly cultured type of tilapia worldwide (El -Sayed, 2006) However, it is now considered an invasive species in Zambia and it is no longer promoted by the Department of Fisheries. Tilapia is cultured in over 100 countries and the production of farmed tilapia nearly quadrupled between 1990 and 2002 from 383,654 metric tons to over 1.5 million metric tons (El -Sayed, 2006) Therefore, the study of semi -intensive tilapia culture will have widespread impact in an agricultural sector which is already experiencing enormous growth. Ideally, the pond is fed by a furrow. A furrow is a ditch which is often used in Zambia for irrigation and household water supply. A furrow begins where part or all of the flow of a stream has been dammed or diverted into a ditch which follows the contours of the stream valley. The furrow should be able to provide enough water to keep the pond or pond system full year round. This is especially important where infiltration through the pond bottom is high and where rainfall is very seasonal. For example, a farmer must be confident that during October, the end of the dry season, water flows in the stream. Otherwise seasonal farming or groundwater fed ponds may be more appropriate.
25 The site should also be close to the house to reduce the risk of theft and the amount of energy expended traveling to and from the pond. Often the compost and manure will be produced near the house; reducing the distance between the pond and these resources saves time and energy The soil should have a high-clay, low -sand content that does not allow for a large amount of inf iltration. There should be plenty of space for future expansion, since the family may want to add more ponds; some for household consumption, fingerlingproduction, or to sell to market. Fingerlings are young fish, 4 to 6 cm long, used to stock a pond. Figure 4 is a schematic showing an aerial and cross section view of a valley used for fish ponds. Figure 4a shows the furrow, diverted stream, and a system of eight ponds. Each pond has its own inlet to prevent contamination between ponds. Figure 4b is a cros s section of the valley. The ponds are built on the valleys slope because it is important that ponds can be gravity -drained so they can be easily harvested and dried between harvests. This draining process is important in maintaining the pond. This proces s includes the removal of trash fish, removal of settled organic matter, and ease of harvesting fish from an emptied pond. The ponds should also be high enough up the valley wall to prevent flood water from reaching the dike walls, which are shown in orange.
26 Figure 4 a) Schematic of a semi -intensive fish farming system showing a system of eight ponds and good placement within a stream valley, b) cross section of a valley utilized for a fish pond system The physical characteristics for a RAP standard pond are summarized in Table 5 Figure 3 shows a cross section and Figure 4 shows a plan view of a RAP standard pond. They also help to reduce the physical efforts exerted during the construction, management, and harvesting of the ponds. Traditional ponds often feature interior walls which have no slopes, just a vertical wal l face. This design does not benefit the fish and actually increases the amount of digging required during construction. Choosing a site with a a) b)
27 slope between 5% and 15% the amount of digging and soil movement is lower than on a valley wall with a much shal lower or steeper slope. Table 5 Physical c haracteristics of a standard pond promoted by the Rural Aquaculture Promotion (RAP) program Feature Dimension Rationale Inside Slopes 3:1 slope Provides location for breeding nests, creates thermocline (warmer water at shallow edges), easier to enter exit pond for maintenance/harvesting Pond Bottom Depth from 0.8m to 1.1m This creates a slight slope in the pond bottom which can help when draining the pond for harvests Outside Slopes 2:1, grass covered Provides structural strength, reduces erosion Overall Size 10m by 15m Larger ponds may be too large for a beginning farmer to manage and they require more resources; more small ponds allow for more combinations of production cycling; spreads disease risk over many ponds Compost Bins 10% of surface area Size and locations large enough to provide ample compost, prevents spreading out of compost on water surface which would block sunlight Inlet/Outlet Pipes 1 inlet, 1 outlet per 100m2 Inlet allows for the control of flow into the pond, outlets allow for overflow control, especially during heavy rains Pipe Screens At inlets and outlets Prevents trash fish from entering the pond from furrow at inlets and prevents fingerlings from exiting at outlets Wide walls 1m wide all around pond Ensures the structural strength of walls is sufficient, provides path for easy access around the entire pond during maintenance/harvesting
28 Figure 5 shows a typical cross section of a pond. The tops of the di ke walls and slopes are covered in grass, the maximum depth of the water is just over a meter, and the overall slope of the site is about 5 to 15%. 1m 10m 1m 1.1m 0.8m Figure 5 Cross section view of a Rural Aquaculture Promotion (RAP) standard pond
29 F igure 6 provides a plan view of a typical RAP standard pond. The furrow is on the upslope side of the pond. It also shows a typical layout for the inlet and outlet pipes, the outside slopes, and the compost bin. Outside slope Inlet Pipe Furrow Compost bin Outlet pipes VALLEY UPSLOPE F igure 6 Plan view of a Rural Aquaculture Promotion (RAP) standard pond showing typical layout of inlets, outlets, furrow, compost bin, and overall orientation in the valley
30 Environmental Requirements Studies have been conducted on the effects of various environmental factors on tilapia production. These studies provide useful insights into fish production, they are limited since factors such as temperature, pH, levels of dissolved oxygen, et cetera wor k together in ways that may limit or enhance growth and reproduction, or possibly even cause fatality. While Table 6 presents guidelines for important factors that could cause fatality or limit production, it is important to keep in mind that various factors may work together to cause undesired effects. Consider the following examples. If the temperature drops over the course of an evening by a few degrees then the fish will tolerate this change. However, if the temperature drops the same amount over a few minutes (perhaps during fingerling transport) than the temperature change could be fatal. Or if one study shows that a certain tilapia species can tolerate a NH3 concentration of 3.4 mg NH3 N/L then maybe the fish were only capable of tolerating this high concentration because they had been acclimatized to NH3 previously and the temperature and pH were in ranges which did not compound stress for the fish.
31 Table 6 Environmental factors affecting tilapia growth and mortality (El -Sayed, 2006) Factor Ideal Tolerable Notes Temperature 20C 35C 7C 10C to 40C 42C Greatly affects growth rates and reproduction Salinity Varies greatly between species; Oreochromis mossambicus, O. aureus, Tilapia zilii most tolerant; optimum limits for all species range from 0 0/00 to 19 0/00 Dissolved Oxygen Aeration not conclusively shown to increase growth rates 0.0 0.5 mg/L Affected by many factors such as photosynthesis, respiration, and diel fluctuation Ammonia Below 0.1 mg un-ionized ammonia (UIA) N/ L LC50 48 h: 2.5 6.6 mg UIA N/L un-ionized ammonia (UIA) is toxic to fish; level of toxicity depends on dissolved oxygen ( DO ), CO2, and pH; brief exposures of high concentration have little lasting effect on growth rates Nitrite Relatively nontoxic at low levels LC50 96 h: 4.4g fish: 81 mg/L 90.7g fish: 8 mg/ L Sustained high levels compromise immune systems, causing mortality; tolerance depends on fish size pH 3.5 5 (acidic lower limit range) 11 12 (alkalin e upper limit range) Adult fish more resistant to low pH, water pH greatly affect resistance to changes in DO Turbidity Below 75 NTU ; growth is inhibited for turbidities greater than 75 NTU Suspended matter which causes turbidity, reduces fertilizer effect, cause s water to acidif y, and inhibits light penetration; turbidity can be caused by rainwater runoff from dike walls, turbid source water, or re-suspension of particles from pond mud by water and fish movement The Bloom The most important concept which should be understood when farming fish is that pond fertilization and composting are not a direct feeding method for fish. The composting materials and fertilizer (often some kind of manure) is added to the pond to promote the
32 growth of algae. The resulting algal bloom is visible as a greenish color in the water colum n The bloom is actually microscopic plankton that use nutrients in the water and sunlight to grow. In turn these phytoplankton are fed on by the fish. The bloom is most important for fingerlings and other young fish since it makes up a large part of their diet. As they become larger the fish begin to feed more frequently on supplemental feeds which are fed directly to fish on the pond s surfa ce. The most important components in pond fertilization are the levels of carbon, nitrogen, and phosphorus supplied to the pond. Potassium is also important if there are very low potassium levels or the alkalinity of the water is low (El -Sayed, 2006) The optimal C:N:P ratio is 50:10:1. According to Edwards (2000) the average nutrient content for phytoplankton in fish ponds is 45-50% carbon, 8-10% nitrogen, and about 1% phosphorus As shown in Figure 7 the source of each of these components is a combination of the compost, ash, and manure. In the case of WWF aquaculture, wastewater will also provide carbon, nitrogen, and phosphorus. However, the carbon and phosphorous depending on the amount of suspended solids will likely come from compost materials, meaning that composting will remain an important part of pond maintenance.
33 Fish ponds can be optimized for fish reproduction ( ponds with mixed-sex cultures designated for the breeding of fingerlings ) or for fast growth of adult fish (all male cultures of a single generation fed with supplemental feeds ). These more intensive production methods often require greater skill and resources to change the sex of fish, and required coordinated harvests and stocking times However, a mixed population consisting of different generations is the norm for r ural fish production in Zambia. Figure 7 was developed by the author as a visual aid to assist farmers understanding of pond inputs, showing that most pond inputs, while essential for fish growth, are actually used to grow the algal bloom. Ash, manure, sunlight, and compost are related to various pond design features and management techniques promoted by the RAP extension agents Plankton/Bloom Ash pH P Manure N, P, K Sunlight energy Compost C, N, P, K Supplemental Feed protein, lipids, fiber Figure 7 Schematic showing various inputs for growth of phytoplankton to support the growth of fish
34 Adding ash to the pond is promoted in the program for predator control and promoting the growth of the algal bloom. It is sugges ted in the guide Fish Farming: Lessons on H ow to Keep Bream that one bucket of ash per 100 square meters be added each week to the pond (Ganther, 2003) Depending on the type of wood which is burned, ash can contain 25 to 45 percent calcium carbonate and is usually less than one percent phosphorus Adding ash to the pond increase s the pH and hardness of the water; therefore, the addition of ash is partic ularly important where soils that underlie the fish ponds are more acidic. This also increases the biological productivity of the water (Maar et al., 1966) An alkalinity which is greater than 20 mg/L as CaCO3 is required to make the addition of fertilizer effective (El -Sayed, 2006) Ash is found in most rural communities as a waste product from cooking using solid fuels As an alternative to using commercial lime, ash becomes a valuable resource in semi -intensive fish farming. Manure provides the main source of nitrogen, phosphorus and potassium (N, P, K). Appendix E provides the compositions (N, P, K ) of various pond fertilizers and compost materials which are commonly found on rural farms in Zambia. The main focus of fertilization and composting schemes are the amounts of nitrogen, phosphorus and carbon added to the pond as well as the ratio between these inputs (El -Sayed, 2006) Maintaining and adjusting fertilization and composting schemes are often the major focus of RAP in Zambia. Often the concept of fertilizing the pond is new to farmers, since traditional fish ponds were left untended and allowed to develop as a natural ecosystem, leaving the fish to fend for themselves. Learning to take ratios of the various fertilizers into consideration is a skill that is focused on with role-model farmers, and at first basic fertilization schemes are promoted, e.g. one 20 liter bucket of chicken manure each week for a 1.5 are pond. (One are is one one-hundredth of a hectare.)
35 Sunlight is also included in Figure 7 above (schematic of pond inputs for phytoplankton growth) so that farmers understand the importance of sunlight in the growth of fish. The bloom is made up of autotrophic organisms that depend on sunlight for growth. Growth of fish can be affected by a lack of sunlight during rainy seasons. By understanding the role of sunlight in the system, farmers are receptive to certain pond design features. The following design features and maintenance techniques can all be justified if one understands that phytoplankton in the pond require sunlight to grow: pond depth, ponds do not need to be more than one meter deep since light will not penetrate; location cleared of trees, trees must be cleared from the area to allow for maximum sun exposure; placing compost in a crib, compost materials are kept in a composting crib because if they float over the surface of the pond they shade the water and phytoplankton below; stocking rates based on surface area not volume, s tocking rates are based on the area exposed to light since this will dictate how much phytoplankton, and therefore fish, c an be supported. Compost is also a major source of carbon in the pond system. In Figure 7 above, i t is set in a larger circle to the side to emphasize its importance. Farmers often do not put enough compost in their ponds. It also differs from sunlight, ash, and manure because it is placed in the compost crib of the pond not applied directly into the pond. Although compost materials are often readily available to farmers in Zambia, under -c omposting is often an issue, and extra emphasis is placed on this component to encourage farmers. The compost is kept in compost cribs and should be kept full at all times. The decaying compost should be mixed daily to encourage decomposition and mixing into the pond water. Many plant by pro ducts and farm wastes are good composting materials, some of these are listed in Appendix E.
36 Fish production begins with the stocking of a pond with six -week -old fingerlings Tilapia fingerlings are typically 4 to 6 centimeters in length. This first generation will mature in about 6 months, having produced two generations of younger fish. When the third generation of fingerlings is 4 to 6 centimeters in length the pond is harvested. First and second generation fish are sold at market. The third generation fingerlings are kept in a 1 by 1 meter holding pond. The pond is drained during the harvesting process. The mud accumulated on the pond bottom is cleared from the pond and the empty pond is allowed to dry for two weeks. This process helps to prevent any fish, snail, or disease causing organisms from contaminating the next cycle of stocking and harvesting. The pond is refilled, and should be regenerated before stocking the pond with the fingerlings from the holding pond. The growth of fish is dependent on a proper supply of algae, as well as sufficient dissolved oxygen, proper water temperature, and supplemental feed. Supplemental feeding is especially important for larger fish after about 45 to 60 days from the initial pond stocking. After this time fish t end to rely less on the natural food supply ( i.e., algal bloom) and require supplemental feeds to grow larger and increase yield. The timing and formulation of supplemental feeds for semi -intensive tilapia farming is outlined in Appendix F Supplemental Feeding Young tilapia feed mainly on plankton (the pond algal bloom ) as they grow their bodies become capable of ingesting larger food and begin to require larger amounts of nutrients and resources to grow. Studies have been done to optimize processed fi sh feeds which are sold to intensive fish farming operations (El -Sayed, 2006) For smaller scale, semi -
37 intensive fish farming practices though, focus is placed on utilizing locally available resources. Feed composition, rate of application, and the start time for supplemental feeding have all been studied. However, there is not one single supplemental feeding scheme which will provide the best yields since yield can be affected by other factors including the fish species. One study presented in Tilapia Culture (El -Sayed, 2006) showed that natural food supply (plankton) was sufficient until the fish matured to about 100 to 150 grams. Beginning supplemental feeding before this point was a waste of r esources since it did not produce significantly larger fish. Also feeding until 50% satiation produced similar yields to feeding until 100% satiation, which shows that significant resources can be saved by feeding a smaller quantity (El -Sayed, 2006) Traditional fish farming practices in Zambia do not include feeding fish. Local farmers are often observed to comment Fish find their own food, why should I feed them? This concept is also reflected in local practices of allowing livestock to graze around the family farm to find food. So simply introducing the idea that feeding fish since they are trapped in the pond and unable to graze may be challenging. However, once the change is accepted farmers should focus on experimenti ng with different combinations of feeds. Finding a good combination of feeds is important since not all of the dietary needs can be met by simply adding maize meal. An exercise for combining different feeds to create a well -rounded diet that includes protein, carbohydrates, fiber, and lipids is presented in Appendix F
38 Farm Integration Farm integration and permaculture are components of many organizations agriculture programs in Zambia, including the United States Peace Corps. It is promoted as a way to gain benefits of synergistic farming practices including: saving time, labor, reducing water consumption, and utilizing farm waste. Farm integration does not focus simply on water and waste reuse. It takes a larger perspective of the farming system including the various roles of family members, spatial planning and farm layout, and permaculture techniques. Permaculture is a method of farming which plans for the highest yield of all farming products by minimizing labor, land area, and materials. Here are some examples of farm integration: Chicken cages built over a fish pond so that manure is dropped directly into the pond. 10 -15 chickens per are Utilizing nutrient-rich pond effluent to irrigate cash crops. Using brewery waste or maize bran in fish feeds. Organizing farm layout so that daily high intensity activities are located closer to the home, while semi -managed and agro-forestry areas are located farther from the home. Utilizing agro-forestry crops to improve soil, while harvesting leaves for animal fodder and fish feed. Expected Yields Yields from fish ponds vary widely. Depending on methods of pond fertilization, stocking densities, and temperature the yields have been observed to be less than one metric ton per hectare annually to over 12 metric tons as observed in a study in Thailand (El Sayed, 2006) Figure 8 shows results of expected yields of tilapia from various studies which varied in stocking rates and fertilization schemes.
39 Figure 8 Yields in metric tons per hectare per year for various semi -intensive tilapia cultures (El Sayed, 2006; Bweupe, 2011) Table 7 presents more details about the fertilization scheme and sexing of the fish in each study. All of the studies which observed yield greater than 6.4 metric tons per hectare per year, except one of the studies in the Philippines, were on fish cultures that had been sexed; i.e. only males were grown to harvest. Also the yield presented here for Zambia, 3.33 metric tons per hectare per year is based on actual farmer data provided from the RAP program. Traditional fish farming in Zambia does not involve fertil ization and supplemental feeding. So this yield captures drawbacks associated with improper harvesting schedules, poor fertilization, and lack of supplemental feeding. 0 2 4 6 8 10 12 14 Yield (MT/ha yr)Yield for various semi intensive tilapia culture systems
40 Table 7 Yearly pond y ields in weight of fish harvested for v arious semi intensive tilapia cultures Species Country Stocking Density (ha-1) Yield (Mt/ ha yr) Sex Stocking Rate (fingerlings/ m 2 ) Fertilization Scheme Tilapia Zambia 11, 000 3.33 mixed 1.1 Variousa O. n Honduras 10, 000 4.16 mixed 1 chicken manure 1000 kg/ha wkb O. n Honduras 10, 000 4.23 mixed 1 chicken manure 1000 kg/ha wkb O. n Panama 10, 000 4.35 mixed 1 chicken manure 1000 kg/ha wkb O. n Kenya 1 000 4.72 males 0.1 diammonium phosphate + urea, 20kg/ha wk b O. n Cameroon 7 600 4.8 mixed 0.76 dry cattle manure, 226 kg/ha wkb O. n Panama 10, 000 5.07 mixed 1 chicken manure 1000 kg/ha wkb O. n Thailand 20, 000 6.4 males 2 280 kg chicken manure + 56.3 kg urea + 17.5 kg TSP/ha wk b O. n Kenya 1 000 7.32 males 0.1 diammonium phosphate + urea, 20kg/ha wk b O. n Egypt 20, 000 7.4 males 2 chicken manure 1000 kg/ha wk for 60 days, 54.4 kg urea + 92.4 kg superphosp a hte/ ha wk a
41 Table 7 (Continued) O. n Philippines 40, 000 9.55 males 4 ammonium phosphate (28 kg N + 5.6 kg P)/ha wk b O. n Philippines 20, 000 10.51 mixed 2 chicken manure 500 kg/ha wkb O. n Peru 20, 000 11.24 males 2 c O. n Thailand 30, 000 13 males 3 urea + TSP; 28 kg N + 7 kg P / ha wkb O. niloticus a (Bweupe, 2011) b (El -Sayed, 2006) c (Cavallini, 1996) The average yield for all studies reported in Table 7 is 6.53 metric tons per year per hectare, while the median is 5.07. Based on this, the expected yield used in this study was 5 .0 metric tons per hectare per year. The average here is augmented by the high yields associate with single-sex cultures and fertilization schemes which utilized synthetic fertilizers. The median was chosen as a more conservative estimate based on the authors experience in Zambia. The Zambian scenario, while having the lowest yield, does capture many of the realistic challenges expected in adopting fish farming technology in a community for which it may be a novelty
42 TREATMENT PLANT CHARACTERISTICS AND LOCATIONS OF CASE STUDIES USED TO PROVIDE WASTEWATER CHARACTERISTICS The study uses results of effluent water quality obtained from community based wastewater treatment facilities located in Bolivia South Africa, Tanzania, Arizona, Zimbabwe, Honduras and Argentina. The w astewater characteristics are secondary data compiled from the various studies to offer a wider view of various loading and treatment plant scenarios than those used in previous aquaculture research (Bunting, 2006) The data from the WWT plants in Bolivia were collected by other University of South Florida researcher s, while the other data was collected by the authors of the studies cited in Table 8 All of the wastewater treatment systems utilize some combination of facultative lagoons and maturation lagoons to treat the wastewater In the United States these systems are no longer a top choice since it is difficult to meet the strict requirements set by the U.S. Environmen tal Protection Agency (EPA) (Oakley S. M., 2005) Removal of biochemical oxygen demand (BOD) can reach 95%, but total suspended solids (TSS) in effluent can reach 150 mg/L (US EPA, 2002 a ). Also, the performance of lagoons in cold climates can be compromised, which has lead to some states to prohibit discharge from lagoons during the winter (US EPA, 2002 a ). However, the systems are appropriate for communities in the developing world where the most pressing issues are those related to reducing and preventing the spread of waterborne infectious diseases and the climate is conducive to their operation (Oakley, 2005) It is also worth noting that many of the countries in which these WWT plants are located are countries which currently have low fish protein supplies, shown in Figure 3 of the
43 Protein Requirements for Human Beings section. The daily per capita supplies of dietary protein from fish are less than 2 gram per person per day in Bolivia, Zimbabwe, Honduras, and Argentina. Of the remaining developing countries Tanzania and South Africa have supplies between 2 and 4 grams per person per day. Table 8 provides data reported in various studies of the nine WWT plants used in this study. The approximate population for each community, the flow rate and nitrogen concentration for the wastewater effluents are given.
44 Table 8 Flow rate and nitrogen concentration of wastewater at each case study location Approximate Population Served Flow Rate (L/s) Nitrogen Concentration (mg N/L) Source Bolivia, Sapecho 1,160 0.77 33.6 Muga et al. 2009 Reents, 2011 Bolivia, San Antonio 777 0.82 22.4 Mihelcic et al., 2010 Reents, 2011 South Africa 9,788 23.1 11.9 Igbinosa and Okoh, 2009 Tanzania 6,500 9.7 58.4 Mbwele et al., 2003 Arizona 27,271 42.9 25.0 Gerk et al., 2001 Zimbabwe, Nemanwa 5,000 2.31 39.0 Nhapi et al., 2003 Zimbabwe, Gutu 10,000 4.63 39.0 Nhapi et al., 2003 Honduras 10,000 24.5 12.3 Oakley, 2010 Argentina 500,000 1,597 27.0 Mendoca, 2006 v ia Oakley, 2010 Sapecho Two community WWT plants in Bolivia were used in this study. Both have been well studied by a research group from the University of South Florida. The wastewater treatment plant in Sapecho serves a community of 1,168 residents as of 2010. The system has been design to treat up to 2.97 L/s The wastewater enters the system and passes through a grit removal chamber. It then passes into an upflow anaerobic sludge blanket (UASB) reactor Water continues into a series of two maturation lagoons and sludge is removed from the UASB reactor to two sludge drying beds (Muga et al., 2009)
45 The flow rate from the final maturation lagoon was reported to be 0.77 L/s and the total nitrogen concentration in the wastewater exiting the final lagoon was 33.6 mg N/L (Mihelcic et al., 2010) San Antonio The wastew ater treatment plant in San Antonio serves 777 residents as of 2010. The system has been design ed to treat up to 1.34 liters per second. The wastewater enters the system and passes through a grit removal chamber. It then passes into a facultative lagoon. Water continues into a series of two maturation lagoons (Mihelcic et al., 2010) The flow from the final maturation lagoon was reported to be 0.82 L/s and the total nitrogen concentration in the wastewater exiting the final lagoon was 22.4 mg N/L (Reents, 2011) South Africa The treatment facility near Alice, South Africa receives a mix of domestic, light industrial, and runoff wastewater and treats it using an activated sludge system (Igbinosa and Okoh, 2009) No additional information about the treatment facility was described. The measurements were taken for nitrate and nitrite were determined in the lab using t he standard photometric method and reported as averages for each of four seasons (Igbinosa and Okoh, 2009) The sum of the averages for nitrate and nitrite were used in this study 11.9 mg N/L The flow was reported in the Methods chapter as the average flow treated by the plant, 23.1 L/s Tanzania The treatment system in Tanzania handles wastewater m ainly from domestic sources for a population of about 6,000; although the system was designed to treat waste for a population of 2,000 to 5,000 people. The wastewater enters a primary facultative pond
46 and then splits into two parallel flows, each of which enters a series of two facultative ponds and finally a maturation pond (Mbwel et al., 2003) Sampling of the wastewater was performed once every two weeks over a period of six months. The samples were analyzed according to procedures described in Standard Methods for the Examination of Water and Wastewater (1995) Arizona This study examined the effectiveness of a constructed wetlands treatment facility. The main goal of the wetland was to reduce nitrogen content in the water so that it could be used as part of an aquifer recharge system. Influent to the wetlands is non-nitrified effluent from aerated treatment lagoons (Gerke et al., 2001) The characteristics of this non-nitrified effluent are used because the nitrogen in this effluent is valuable for reuse in aquaculture. The average daily effluent flow from the WWT plant was reported as 3 710 cubic meters per day Monthly average flows ranged from 3, 300 to 4, 500 cubic meters per day The average total nitrogen for WWT plant effluent was reported i n the M ethods chapter 25 mg N/L and the inflow of BOD was 50 mg/L. Zimbabwe In Zimbabwe two water reuse systems were analyzed. The system in Nemanwa and Gutu treated wastewater from populations of 5,000 and 10,000 people, respectively. The plant at Nemanwa w as report to treat a flow of 2.3 L/s, while the plant at Gutu treated 4.6 L/s. Both systems received mixed wastewaters of residential and commercial sources (Nhapi et al. 2003) At Gutu the untreated wastewater entered a primary treatment pond followed by two duckweed ponds in series and then a final maturation lagoon. The effluent
47 characteristics from this pond were used. At Nemanwa the untreated wastewater entered two anaerobic ponds followed by two duckweed ponds in series and finally a maturation lagoon. Water characteristics for the final effluent from this plant were not reported so the wastewater characteristics after the first duckweed pond were used. The authors used the micro-Kjeldahl method followed by distillation with sodium hydroxide and sodium thiosulphate solution to determine the total nitrogen concentration. The total concentrations for nitrogen in the wastewater at Gutu and Nemanwa, at the points described above, were both reported to be 39.0 mg N/L (Nhapi et al. 2003) Honduras The WWT plant in Tela, Honduras treats an average of 24.5 L/s se rv ing an estimated population of 10,000 people. The WWT plant consists of a facultative lagoon followed by t wo maturation lagoons in series. The mean effluent total nitrogen was reported as 12.3 mg N /L (Oakley 2010) Argentina The WWT plant in Mendoza, Argentina treats an average of 1,597 L/s serving an estimated population of half a million people. The mean effluent total nitrogen is 27 mg N/L The WWT plant consists of twelve batteries of one facultative followed by two maturation lagoons in series. The area of the entire lagoon system is 278 hectares (Medoca, 2006 via Oakley, 2011).
48 METHODS This chapter provides the rationale behind the assumptions used for the study calculations. The analysis perform ed in the study is summarized in Figure 9 Measured quantities are depicted in green (and described in Table 8 of the previous chapter ), while calculated values are shown in red. Flow Rate (L/s) Nitrogen Concentration Effluent (mg/L) Nitrogen Loading (kg N/day) Pond Area (ha) Yearly Servings (#) Number of Persons Diets Affected (per) Percent Diets Affected (%) Yield (Mt/yr) Population (persons) Volume of Water Evaporated (m3/day) Figure 9 Flowchart of calculations for nitrogen loading, estimated total pond area, amount of water evaporated, estimated yearly pond yield, number of tilapia servings, number of persons affected
49 Nitrogen L oading, Pond Area, and Evaporation As discussed earlier in this thesis, the rate of nitrogen loading is the most important design factor for an aquaculture system. The pond sizes are determined to provide a nitrogen loading rate of 4 k g N per hectare per day which was indicated by previous research to be the optimal nitrogen loading rate (El -Sayed, 2006; Bunting, 2006; Mara et al., 1993) First, the nitrogen loading, in kilograms N per day, was calculated for each plant using Equation 1, where Q is the flow rate in L/s and CN is the nitrogen concentration in mg N /L in the treatment plant effluent: Equation 1 Nitrogen loading = 86 400 10 Equation 2 p rovides an example calculation of nitrogen loading for the data obtained from the wastewater treatment effluent of Sapecho, Bolivia: Equation 2 Nitrogen loading, Sapecho = 86 400 10 = 0 77 33 6 86 400 10 = 2 24
50 Secondly, the total pond area of a fish farming system that can be supported by the calculated daily nitrogen loading from the plant is determined using Equation 3: Equation 3 Pond area = 4 Equation 4 is an example calculation for the expected fish pond area t hat could be supported from the wastewater effluent associated with the treatment plant in Sape cho, Bolivia: Equation 4 Pond area, Sapecho = 4 = 2 24 4 = 0 56 To evaluate whether the quantity of water is sufficient to keep ponds of the estimated size filled, the amount of water which would evaporate daily was calculated using Equation 5, where Revap, is the rate of evaporation. Two rates of evaporation where chosen to represent a range of range of climates, 3mm per day and 9mm per day. The value used in the Kolkata, India study, 5mm per day falls within this range. Equation 5 Volume of water evaporated from a fish pond system = 10 000 1 000
51 Equation 6 is an example calculation for the expected amount of evaporation occurring from a pond system associated with the treatment plant in Sapecho, Bolivia at a rate of 3mm per day : Equation 6 Volume of water evaporated from a fish pond system Sapecho V = 10 000 1 000 = 3 0 56 10 000 1 000 = 16 8 m day Nitrogen in Human Urine Nitrogen which enters a WWT system can be estimated based on the number of people it serves. Studies have found that people excrete betw een 2.7 and 4.5 kilograms of nitrogen each year in their feces and urine. Other characteristics of nutrient content in excrement are presented in Appendix G It is important to note that 81 90% of nitrogen excreted by humans is found in the urine (Kvarnstrm, 2006) Since a majority of the nitrogen associated with the feces would likely settle out as part of the sludge, only the portion of nitrogen associated with urine is used in this calculation, up to 4.0 kg nitrogen per person per year. The following calculation will estimate the amount of nitrogen one could expect to see entering the WWT plants in this study. Since the studies reported that nitrogen removal does occur in these treatment systems we would expect only a portion of this nitrogen to be represented in the nitrogen loading obtained from wastewater effluent that was calculated in the Nitrogen Loading section. The results for the amount of nitrogen excreted in urine will be compared to the nitrogen loadings calculated with the flow rates and WWT plant effluent concentrations of nitrogen to ensure that the wastewater nitrogen loadings are reasonable.
52 The amount of nitrogen (from urine) entering the WWT plants was calculated using Equation 7 : Equation 7 Nitrogen excreted in urine per day by a population = 4 0 1 365 Equation 8 is an example calculation for the amount of nitrogen in kilograms per day excreted by the population in Sapecho, Bolivia: Equation 8 Nitrogen excreted in urine per day by a population, Sapecho = 4 0 1 365 = 1 160 4 0 1 365 = 12 7 The results for nitrogen loading based on nitrogen found in human urine will be compared to the result for nitrogen loading based on the WWT plant effluents. Expected Yields and Number of Diets Affected by Fish Ponds Using the value of 5 Mt of fish per hectare per year determined in the Fish Farming Syste ms chapter, t he total expected fish yields in metric tons per year, for a pond system constructed at each of these plants was determined using Equation 9 : Equation 9 Pond y ield in metric tons of fish per year = 5 Equation 10 provides an example calculation for the expected fish yield for a pond system integrated with the wastewater treatment plant effluent from Sapecho, Bolivia:
53 Equation 10 Pond y ield in metric tons of fish per year Sapecho = 5 = 0 56 5 = 2 79 The total number of 85 gram servings of tilapia was also determined for the effluent from each treatment plant using Equation 11: Equation 11 Servings of tilapia per year from yield = 10 85 I n Equation 11, the value of 85 grams per serving was obtained from the United States Department of Agriculture (USDA, 2006) Equation 12 provides an example calculation for the number of 85 gram servings produced by fish ponds each year that is integrated with the wastewater effluent for the Sapecho treatment system: Equation 12 Servings of tilapia per year from yield, Sapecho = 10 85 = 2 79 10 85 = 33 000 Based on the rationale presented along with Figure 3 one person would reasonably add an average of 10 grams of protein from fish to their diet, or 3.65 kilograms of protein per
54 year However, these 10 grams of dietary protein do not correlate directly to 10 grams of harvested tilapia. All foods are made up of many different components. Therefore, we must know how much dietary protein is contained in tilapia. For every 85 gram serving of tilapia, 17 grams of protein are consumed (Fat Secret, 2011) Equation 13 was used to calculate the number of people who would be impacted by the installation of the fish ponds through access to greater amount of protein in their diet: Equation 13 Number of persons diets affected by integration of wastewater fed aquaculture = 1000 1 3 65 17 85 Equation 14 is an example calculation for the number of persons diets affected in Sapecho, Bolivia by the installati on of the fish ponds: Equation 14 Number of persons diets affected by integration of wastewater fed aquaculture, Sapecho = 1000 1 3 65 17 85 = 2 79 1000 1 3 65 17 85 = 153
55 RESULTS The feasibility of supporting fish farming from the treated wastewater effluent associated with nine geographically diverse treatment plants was analyzed in this study. The selected communities range in population from 777 people in San Antonio, Bolivia to half a million people served by the plant in Argentina. However, the average population of seven communities in this study other than Argentina is 8,800, reflecting the focus of this study on small scale WWT plants. The associated concentrations for total nitrogen in the treated effluent ranged from a low of 11.9 mg N/L at the South Africa plant to a high of 58.4 mg N/L at the plant in Tanzania. The flow rate at each plant was different and related to the population served. It ranged from a low of 0.77 L/s at the Sapecho, Bolivia plant to 1,597 L/s at the WWT plant in Argentina. Excluding the largest WWT plant (Argentina) the average flow rate for the other eight WWT plants is 13.6 L/s. Nitrogen Loading, Pond Area, and Evaporation Following the flow chart provided previously in Figure 9 of the Methods chapter the first calculation performed was the effluent nitrogen loading per day at each WWT plant. This was calculated from the flow rate, in L/s, and the total nitrogen concentration, in mg N/L. Thes e concentrations were measured in the effluent of the WWT facilities, where an aquaculture system would likely be integrated. Table 9 presents calculated results for nitrogen loading at each of the nine locations along with the measured flow rate and nitrogen concentration.
56 Table 9 Flow rate, nitrogen concentration, and nitrogen loading at each plant Flow Rate (L/s) Nitrogen Concentration (mg N/L) Nitrogen Loading (kg N /day ) Bolivia, Sapecho 0.77 33.6 2.24 Bolivia, San Antonio 0.82 22.4 1.59 South Africa 23.1 11.9 23.7 Tanzania 9.7 58.4 49.0 Arizona 42.9 25.0 92.8 Zimbabwe, Nemanwa 2.31 39.0 7.80 Zimbabwe, Gutu 4.63 39.0 15.6 Honduras 24.5 12.3 26.1 Argentina 1,597 27.0 3,730 The nitrogen loadings used in this study thus ranged from a low of 1.59 kg N /day at the San Antonio, Bolivia WWT plant, to a high of 3,730 kg N /day at the Argentina plant. Because the nitrogen concentrations in the treated effluents are of similar magnitude for all the plants, this large range of nitrogen loadings can be attributed mostly to the large range of flows amongst these plants. However, some variation can be attributed to the differences amongst nitrogen concentration. For example, if one compares the flow rate of the two Bolivian treatment plants it can be noted that while the flow rate at the Sapecho plant is lower than the San Antonio plant (0.77 L/s vs. 0.82 L/s), the nitrogen loading at the Sapecho plant is actually greater than at the San Antonio plant (2.24 kg N/L vs. 1.59 kg N/L). This is due to the higher total nitrogen concentration measured in the effluent at the Sapecho plant (33.6 mg N/L vs. 22.4 mg N/L). These results are now compared to the estimation for the nitrogen foun d in the urine of a population, calculated earlier using Equation 7 The nitrogen loading expected at each plant, based on reported values for nitrogen found in human urine, is provided in the
57 column labeled: Nurine. The nitrogen loading in the treated was tewater, calculated with the flow rate and nitrogen concentration, is given in the column labeled: NWW. These values are then compared in the final column labeled NWW/Nurine. Table 10 Comparison of nitrogen loading in wastewater treatment plant effluent and nitrogen loading expected from human urine Nurine (kg N/d ay ) NWW (kg N/d ay ) NWW/Nurine % Nitrogen Found in Wastewater vs. Estimated Nitrogen Found in Urine Bolivia, Sapecho 12.7 2.24 17.6% Bolivia, San Antonio 8.52 1.59 18.6% South Africa 107 23.7 22.1% Tanzania 71.2 49.0 68.8% Arizona 299 92.8 31.0% Zimbabwe, Nemanwa 54.8 7.80 14.2% Zimbabwe, Gutu 110 15.6 14.2% Honduras 110 26.1 23.8% Argentina 5,479 3,730 68.0% Some nitrogen which enters the WWT plant either settles out into the sludge, is converted to biomass which then settles, or is released to the air via denitrification. The results show that the amount of nitrogen measured in the WWT plant effluent as a percentage of the amount of nitrogen expected to be produced by the population ranges from a low of 14.2% at the Zimbabwe plants to a high of 68.8% at the Tanzania plant. This difference may be because the actual nitrogen removal varies at each plant,
58 affecting the effluent concentration of nitrogen. In addition, the type of populations served by the plants varies from entirely domestic in Bolivia to a more mixed domestic/commercial type in Tanzania. In addition, this analysis showed that the nitrogen loadings used in this research that were based on the measured WWT plant effluents appear reasonable because the amount of nitrogen found in the WWT plant effluent contains less nitrogen than the estimated amount of nitrogen produced by the population. The total area of fish ponds that could be integrated with each wastewater effluent stream was determined from the nitrogen loading rates specific to each WWT facility. The total number of fish pond hectares which could be supported in each community is provided i n Table 11. This area represents the total area of ponds, and does not directly imply the number of ponds. RAP standard ponds are generally 150 square meters, but each system could utilize ponds of various sizes to suit the landscape and development plan of each community. Table 11 Estimated total area of fish ponds at each wastewater treatment plant Estimated Total Pond Size (ha) Bolivia, Sapecho 0.56 Bolivia, San Antonio 0.40 South Africa 5.93 Tanzania 12.3 Arizona 23.2 Zimbabwe, Nemanwa 1.95 Zimbabwe, Gutu 3.90 Honduras 6.52 Argentina 932
59 To evaluate whether the quantity of water is sufficient to keep the pond system filled the amount of water which would evaporate from the ponds was calculated and compared with the flow rate of each WWT plant. The resulting estimation for total water evaporating for the pond system in cubic meters per day at rates of 3 mm per day and 9 mm per day are provided in Table 12, along with the flow rate for each WWT plant in cubic meter s per day. The range of percentages of the WWT plants flow rate which is estimated to be lost by evaporation is provided in the final column of Table 12. Table 12 Flow rate, estimated amount of water evaporated daily from pond sy stem and percentage of flow lost to evaporation Flow Rate (m3/day) Range of Volumes of Water Evaporating from Fish Pond System (m 3 /day) Range of Percentages of Flow Lost from Fish Ponds Through Evaporation Bolivia, Sapecho 66.5 16.8 50.3 25% 76% Bolivia, San Antonio 70.9 11.90 35.7 17% 50% South Africa 2,000 178 534 9% 27% Tanzania 840 368 1,100 44% 131% Arizona 3,710 696 2,090 19% 56% Zimbabwe, Nemanwa 200 58.5 176 29% 88% Zimbabwe, Gutu 400 117 351 29% 88% Honduras 2,121 196 587 9% 28% Argentina 138,000 27,900 83,800 20% 61% The estimated percentage of effluent water lost through evaporation from the pond surface ranges from 9 % at the Honduras WWT (rate of 3 mm per day) plant to 131 % at
60 the Tanzania WWT (rate of 9mm per day) plant. This is a reflection of the concentration of nitrogen in the treated wastewater effluent. For WWT plant with a high concentration of nitrogen in the wastewater effluent, such as Tanzania (58.4 mg N/L), the design is for a relatively larger pond system compared to a WWT plant with lower effluent concentrations of nitrogen, such as the plant in Honduras, (12.3 mg N/L). Expected Yields and Number of Diets Affected by Fish Ponds The expected yields for the fish ponds at each WWT plant are presented in Table 1 3 For each WWT plant the expected yield is given in metric tons produced each year. As shown in the flowchart in Figure 9 of the Methods chapter the expected yield is used to calculate the number of 85 gram tilapia servings and the number of persons whose diet could be affected by the integration of an aquaculture system. The results of those calculations are provided in Table 13 The expected yield ranges from a low of 1.98 metric tons of tilapia per year, at the San Antonio plant, to over 4,000 metric tons at the plant in Argentina. This is mainly a reflection of the differing sizes of those plants.
61 Table 13 Expected aquaculture system yield, number of tilapia servings produced each year, and the percentage of the population affected by aquaculture integration Yield (Mt/yr) Number of Servings (85g) of Tilapia (per year) Number of Person's Diets Affected (per year) Percent Population Affected by Aquaculture Integration Bolivia, Sapecho 2.79 32,900 153 13.2% Bolivia, San Antonio 1.98 23,300 109 14.0% South Africa 29.7 349,000 1,625 16.6% Tanzania 61.3 721,000 3,357 51.6% Arizona 116 1,360,000 6,353 23.3% Zimbabwe, Nemanwa 9.75 115,000 534 10.7% Zimbabwe, Gutu 19.5 230,000 1,068 10.7% Honduras 32.6 384,000 1,787 17.9% Argentina 4,660 54,800,000 255,205 51.0% The number of tilapia servings produced by this expected yield ranges 23,300 at the San Antonio plant to approximately 55 million servings at the Argentinean treatment plant. Similarly, the number of persons diets affected by this new supply of protein is presented and ranges from 109 in San Antonio to over a quarter -million in Argentina. The number of diets affected as a percentage of the populations served by each plant, ranges from a low of 10.7% at the Zimbabwean plants to a high of 51.6% at the Tanzania plant. The Tanzanian plant had the highest nitrogen concentration by far at 58.4 mg N/L. This high concentration accounts for the large pond area and hi gh yields
62 at this plant; therefore, the high concentration can also explain why a large portion of the population would be affected by the integration of an aquaculture system. Since the Zimbabwean plants do not have exceptionally low nitrogen concentrati on, 39.0 mg N/L, in their wastewater another factor must account for the low percentage of the population which could be affected. One explanation could be the low flow rate at these plants. The portion of the wastewater flow accounted for by one person at these plants is 40 liters per person per day At other plants it ranges from 57 L/per d ay to over 200 L/per d ay This low flow rate means causes low nitrogen loading, in turn lowering the area of ponds that could be supported by these WWT plants Evaluating Other Environmental Requirements Based on the environmental factors outlined in Table 6 of the Fish Farming Systems chapter Table 14 was compiled to compare the environmental limits or recommendations for tilapia farming to the actual measurements taken at the WWT plants. Not all studies provided detailed wastewater effluent measurements for each of the factors. For those plants that did report relevant data, the measurements are provided below alongside the limits or ideal factors Of the treatment plants which reported dissolved oxygen (DO) levels in the WWT plant effluents, nearly all are within and acceptable range for the growth of tilapia. Only the treatment plant effluent for the Nemanwa, Zimbabwe plant showed a DO level of zero for its l owest measurement. The mixing action of water entering the ponds and the production of oxygen by photosynthesis should produce a sufficient amount of oxygen to support the respiration of fish. The temperature of the wastewater effluent at the various plants ranges from 11 C in Arizona to 25 C in Gutu, Zimbabwe. Because some of the temperatures are lower than
63 the optimal range of 20 to 35 C, attention will need to be paid to the planning of reproduction. Since many tilapia species will not reproduce unless the water is greater than a certain temperature, stocking and harvesting will need to be seasonally planned so that reproduction coincides with the warmest part of the year. The temperature the wastewater effluents do not even approach the lethal limits for tilapia, less than 7 C or greater than 42 C.
64 Table 14 Wastewater characteristics which could affect tilapia growth at each wastewater treatment plant Boli via, Sapecho Bolivia, San Antonio South Africa Tanzania Arizona Zimbabwe Nemanwa Zimbabwe Gutu Limit/Ideal Dissolved Oxygen (mg/L) 7.7 9.6 4.2 5.4 8.9 0 13.1 2.9 11.7 0.0 0.5 Temperature (C) 22.5 22.0 15.2 24.7 11 16 14 26 13 25 20 35 Nitrite (mg N /L) 0.12 1.30 3.52 < 0.02 < 0.03 8 pH 7 6.93 6.10 7.03 9.2 6.8 8.0 7.1 8.1 4.3 11.5 Turbidity (NTU) 43.5 90.4 3.68 9.64 11 77 31 73 75 BOD Loading (kg/haday) 3.47 5.30 12.6 8.0 10 20 Fecal Coliforms (FCU/100mL) 1.785 1.215 653 105 Orthophosphate Loading (kg/haday) 0.41 0.50 0.11 1.6 1.5 0.51 1.0 0.51 1.0 2
65 A nitrite concentration of 8 mg N/L is 50% lethal at 96 hours for certain tilapias weighing more than 90. 7 grams (El -Sayed, 2006) The tolerance to nitrite increases for smaller fish. The highest reported level of nitrite was at the WWT plant in South Africa: 1.3 mg N/L This is well below the LC50 of 8 mg/L; therefore, nitrite entering the pond in treated wastewater is likely not of major concern. There is also no indication that the pH of wastewater entering the ponds should have a direct effect on the health of the fish. Tilapia tolerate a large pH range and all of the pH measurements recorded at the treatment plants (i.e., 6.1 to 9.2) fall within the tolerable limits for tilapia of 4.3 to 11.5 (El -Sayed, 2006) The turbidity of WWT effluents ranged from 3.7 NTU to 90.4 NTU. Excluding the one high value of 90.4 NTU reported at the San Antonio treatment plant in Bolivia all of these values fall below the turbidity limit of 75 NTU for good tilapia growth. It is likely that sedimentation that occurs in the fish ponds and this sedimentation of suspended solids from the wastewater stream into the pond would cause the turbidity of the pond water to be lower than that of the WWT plant effluent. The Cavallini study in Peru suggested BOD loading to the pond should be between 10 and 20 kilograms per hectare per day (Cavallini, 1996) The four WWT plants which reported BOD concentration in the WWT plant effluent resulted in BOD loadings ranging from 3.47 to 12.6 kilograms per hectare per day All of these BOD loadings fall within Cavallini s suggested range. Some of the studies reported the orthophosphate or total phosphorus concentration in the effluent. The phosphorus loading to the fish pond systems were determined and found to ranged from 0.11 kg P/ha d ay at the WWT plant in South Africa to 1.5 kg P/ha d ay at the WWT plant in Tanzania. One study suggested an application of 2.0 kg
66 P per hectare per day (El -Sayed, 2006) The pond bottom soil influences the amount of phosphorus available in pond water for plankton growth (El -Sayed, 2006) Because none of the WWT plants exceeded 2.0 kg P per hectare per day the ponds will likely require supplemental fertilization, especially with fertilizers/compost materials high in phosphorus : e.g. chicken or pig manure, soya or lantana leaves, or D -compound. Since the availability of phosphorus is affected by the acidity of the pond bottom, adding ash, can adjust the pond bottom pH, allowing the phosphorus to remain available for plankton growth. Of the wastewater treatment systems presented in this study, three reported fecal coliform counts in the WWT plant effluent. At the Bolivian WWT plants the number of fecal c oliforms per 100 mL was 1.78 105 and 1.21 105, at the Tanzania WWT plant it was 653. The two WWT plants in Bolivia do not meet the WHO standard of less than 105 for fish pond influent. Fecal coliform counts for WWT treatment plants in the United States range from 7.0 to 3.6 105, suggesting that the regulation could be met with lagoon style wastewater treatment (Crites & Tchobanoglous, 1998)
67 DISCUSSION AND CONCLUSIONS Discussion T his objective of this study was to evaluate the integration of small wastewater treatment facilities with aquaculture in a developing world setting to determine whether treated wastewater effluent can provide a sufficient amount of water and nutrients to farm fish and provide a significant amount of a communitys protein intake. The study evaluated data obtained from nine locations: two in Bolivia, one in South Africa, one in Tanzania, one in Arizona, two in Zimbabwe, one in Honduras, and one in Argentina. All of these locations utilize lagoon style treatment methods, which have been promoted for tropical locations in the developing world because of their simple design, low cost, and effectiveness at pathogen removal (Oakley 2005) The amount of nitrogen available for utilization in semi -intensive tilapia culture was determined to be sufficient to support fish pond systems at each of the WWT facilities. The total size of the resulting fish ponds ranged from about half a hectare to over 900 hectares, assumi ng that the fish ponds would require a nitrogen loading of 4 kg N/haday Estimations of the amount of evaporation from the fish pond systems were used to assess whether the flow was sufficient to maintain adequate water level in the ponds. This water l oss was estimated to range from 15% to 73%. For a WWT plant with a high concentration of nitrogen in the wastewater effluent, the size of the pond system designed should be carefully assessed. The system must be supported by a wastewater effluent flow rate large enough to account for water loss
68 through evaporation and subsurface infiltration based on the local condition of climate and soil type. Based on data for protein consumption and sources of dietary protein, the number of people who would have access to increased servings of protein through the integration of a tilapia farming system with the existing WWT plant effluent was determined for each of the study sites. The analysis showed that the integration of tilapia aquaculture with the existing WWT plant effluent could improve the diets of 11% to 52% of the persons served by the WWT plants. The average percentage of persons whose diets would be affected is 23%. For example, the city of Kolkata (India) has approximately 4.6 million residents (2001) and the current fish production of the Kolkata fish farms is 1,560 metric tons of fish annually (Bunting, 2006; Brinkhoff, 2011) This is enough fish to affect the diets of 12% of the citys population. Comparing the percentage of people who are affected by this existing integrated WWF aquaculture system shows that the amount of added protein is significant in all the communities studied. The aim of UN Millennium Development Goal 1 is to reduce by 50% the number of people l iving in extreme poverty and hunger by 2015. It is unlikely that the additional dietary protein produced by integrating a WWF aquaculture system would be evenly distributed among the population or benefits the neediest persons with in the population. Howe ver, if the neediest 23% (average number of diets affected) of the population of these communities experienced improvements to their diets, then significant progress towards achieving the MDGs could be made. By linking the benefits of aquaculture with wast ewater treatment a community may be inclined to support the construction and maintenance of wastewater treatment systems This is because the social and economic benefits of solely treating wastewater may not
69 be perceived as a large enough incentive. For example, at the treatment WWT plant in Tanzania, the lagoons had not been desludged in 16 years (Mbwele et al., 2003) The associated incentives of tilapia aquaculture could be very helpful in poorer communities, where a major problem was the inability or desire for beneficiaries of wastewater treatment to support the WWT technology (Edwards, 1992) The study found that the current level of fecal coliform contamination in wastewater effluent did not meet the WHO standard of 105 FCU per 100 mL. There are two options to deal with this shortcoming. Either the design of WWT lagoons could be adjusted to meet this target, or the target could be revised to allow for use of wastewaters which have a higher number of FC. To optimize lagoon treatment for pathogen removal the main mechanism for their removal must be considered. Natural die-off of pathogens, as well as predation, sedimentation, and adsorption occur in lagoons (Crites and Tchobanoglous, 1998) Models for the removal of fecal coliforms in lagoon systems are dependent on temperature of the water and the retention time of the lagoon (see Appendix H ). This suggests that increasing retention times during lagoon design could help in achieving greater removal of FC. It would also be i mportant that the systems are not under -designed for the amount of wastewater created by the community. Future Research Future studies should be done to assess the level of FC contamination in ponds which received WWT effluents containing greater than 105 FCU per 100 mL. The WHO already sets different standards for the wastewater intended for reuse in fish ponds and actual pond water itself: 104 FCU per 100 mL and 105 FCU per 100 mL, respectively (WHO, 2006) This differentiation is to account for the effects of pathogen removal which occurs within the fish pond. The removal mechanisms for maturation lagoons are also happening in fish ponds, hence the suggestion by some to use them as part of the
70 treatment phase (Cavallini, 1996) Even though the pond influent may not meet the current standard set by the WHO, the pond water itself could test to show less than 104 FCU per 100 mL: the standard level to protect the help of fish pond workers and cons umers. Since the specific standard for FC contamination by the WHO follows from its health based targets, which are measured in DALYs, it is possible that the current limits are stricter than necessary. By using WWT effluents in aquaculture or other agric ulture projects the prac ti tioners may be more aware of pr oper preparation of fish since it is directly related to known pathogens. The health impacts associated with fish grown in WWT plant effluents may be lower compared to indirect reuse ( releasing highl y contaminated wastewater to surface waters, which are then in turn used for agriculture or even drinking water supply ). This indirect reuse may present detachment in the perception of the users from the contamination source and the point of reuse, causing users to take fewer precautions to prevent waterborne disease. This reasoning might turn out to show a lower disease burden associated with direct wastewater reuse, even if it does not meet current standards suggested by the WHO. Further studies using thi s health based target perspective, especially at the national level as suggested by the WHO, would be required to determine if this is the case. Studies should be made to see if there are significantly higher numbers of helminth eggs in fish pond sediments from wastewater reuse systems as compared to surface water systems. No data was found for helminth egg contamination in the effluent of the WWT plants used in this study. The WHO requirement for helminth eggs found in wastewater intended for reuse is an arithmetic mean of less than one egg per liter or per gram total solids (WHO, 2006) Pond bottoms should have all muddy deposits removed after each harvest period. The pond bottom should then be allowed to dry and crack for two weeks.
71 Currently the RAP program suggests that this mud be spread in gardens to fertilize the soil. Using the results of these studies a proper disposal or reuse method for pond mud can be developed. Following the RAP suggestion to reuse pond mud for gardening, RAP also suggests using pond effluents to irrigate vegetable crops. This leads to the question of how to treat fish pond effluent. In Zambia, regulating fish pond effluents is not of concern. It is assumed that the density of farmers who dischar ge effluent to local streams is so low that it is unlikely to have major impacts. This does not mean that it should not be a concern for the Department of Fisheries in Zambia. As aquaculture expands with demand the nutrient-rich effluents from fish ponds c ould pose a threat to waterways as it has in other countries (El -Sayed, 2006) Field studies on systems such as those proposed in this study should be conducted to characterize the effluents of semi -intensive tilapia productio n. If these effluents are of very high-strength or are discharged in such a quantity that they may compromise the quality of local waterways, farmers in Zambia and the agencies required to regulate the quality of waterways will be forced to implement polic ies mitigate the effects of aquaculture. For now farm integration is promoted as a way to capture the nutrients in fish ponds effluents. Farmers divert discharges from directly entering streams and lakes for irrigation in garden for cash crops such as cabb ages and tomatoes. The effectiveness of this practice for protecting surface water from high nutrient loading should be investigated. Other wastewater polishing treatments could also be implemented for nutrient removal if this practice is not sufficient. These treatments could be biological treatments such as duckweed ponds, maturation lagoons and WWT wetlands.
72 Studies on the social acceptance of fish produced in wastewater fed ponds should be done in the countries where WWF aquaculture systems are promoted to evaluate the acceptance of fish produced in treated wastewater. For example, i n a report about wastewater fed aquaculture in Lima, Peru the authors found that there was complete acceptance for the fish produced in wastewater fed ponds, even when the consumers knew where the product came from (Cavallini, 1996) The existence of the wastewater fed fishponds outside of Kolkata, India (the largest in the world) (Cavallini, 1996) indicates that acceptance of fish produced in ponds fed with wastewater effluent may be generally acceptable in an area where demand for cheap protein is high and the use of wastewater in agriculture already exists. However, a major loss in capital, time, and labor could occur if the market for WWF aquaculture product is not studied before the implementation of these systems. Conclusion This study has shown that small lagoon based WWT plants in the developing world can provide enough water and nutrients for an integrated WWF aquaculture system. It has also been shown that other wastewater characteristics important for the health of tilapia, such as the concentration of dissolved oxygen, temperature, nitrite concentration, and pH do not appear to pose any risk to the health of the fish. However, phosphorus loading from the WWT plants does not appear to be sufficient because the phosphorus loading from treated wastewater did not exceed 2.0 kg P/ha day. Therefore, addition of compost to the fish ponds should focus on provision of phosphorus. Conservative estimates obtained from this study suggest that the productivity of these WWF fish ponds would affect on average 23% of the population of these communities served by the wastewater treatment systems. Estimations for the amount of protein produced by
73 this integrated farming technique should be able to play an important role in the achievement of the Millennium D evelopment Goals. This study has shown that reuse of WWT plant effluents will require more effective removal of fecal co liforms in order to meet standards set by the WHO. However, given the context, the level of fecal coliforms in these treated wastewaters should not rule out WWF aquaculture as an option for small communities in developing countries to reduce poverty, malnutrition, and disease burden of waterborne illnesses.
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75 Heck, S., Bn, C., & Reyes -Gaskin, R. (2007). Investing in African fisheries; building links to the Millenium Development Goals. Fi sh and Fisheries, 8, 211-226. Igbinosa, E. O., & Okoh, A. (2009). Impact of discharge wastewater effluents on the physio-chemical qualities of a receiving watershed in a typical rural area. International Journal of Environmental Science and Technology, 6 (2), 175-182. (IWMI) International Water Management Institute. (n.d.). Recycling Realities: Managing Health Risks to Make Wastewater an Asset. Retrieved October 2010, from International Water Management Institute: http://www.iwmi.cgiar.org/ Publications/Water_Policy_Briefs/PDF/wpb17.pdf Jamwal, P., & Mittal, A. (2010). Reuse of treated sewage in Delhi city: Microbial evaluation of STPs and reuse options. Resources, Conservation and Recycling, 54, 211-221. Junge, R. (2001, August 23). Retrieved September 2010, from Institut fr Umwelt und Natrliche Ressourcen: www.hortikultur.ch/pub/files/89.pdf Kvarnstrm, E. E. -O. (2006). Urine Diversion One Step Towards Sustainable Sanitation. Stockholm, Sweden: Stockholm Environment Institute. Maar, A., Mortimer, M., & Van der Lingen, I. (1966). Fish Culture in Central East Africa. Rome, Italy: Food and Agriculture Association of the United Nations. Mara, D., Edwards, P., Clark, D., & Mills, S. (1993). A Rational Approach to the Design of Wastewater -Fed Fishponds. Water Research, 27 (12), 1797-1799. Mbwele, L., Rubindamayugi, M., Kivaisi, A., & Dalhammar, G. (2003). Performance of a small wastewater stabilisation pond system in a tropical climate in Dar Es Salaam, Tanzania. Water Science and Technology, 48 (11 -12), 187-191. Mihelcic, J. R. et al. (2010). Sustainable Water Management Research Experience in Bolivia: Influence of a Dynamic World on Technological and Societal Solutions. Via e -mail Mihelcic, J. R. on 25 October, 2010. Muga, H., Mihelcic, J. R., Reents, N., Gemi o, G., & Morales, S. (2009). Performance of Lagoon Wastewater Treatment System in Sapecho, Bolivia. Via e -mail Mihelcic, J. R. on 25 October, 2010. Nhapi, I., Dalu, J., Ndamba, J., Siebel, M., & Gijzen, H. (2003). An evaluation of duckweed-based pond systems as an alternative option for decentralised treatment and reuse of wastewater in Zimbabwe. Water Science and Technology, 48 (2), 323-330. Oakley, S. (2010). Via e-mail Oakley, S. M. on 10 February, 2010. Oakley, S. M. (2005). The Need for Wastewater Treatment in Latin America: A Case Study of the Use of Wastewater Stabilization Ponds in Honduras. Small Flows Quarterly, 6 (2), 36 -51. Reents, N. (2011, January). Via e-mail Reents, Nathan on 10 February, 2010.
76 The World Fish Center. (2007). The Millennium Development Goals: Fishing for a Future. Retrieved from Brochure No. 1709, October 2011 http://www.worldfishcenter.org/v2/files/MDG%20brochure %2072dpi.pdf Tschakert, P. (2010). Mercury in fish: a critical examination of gold mining and human c onsumption in Ghana. International Journal of Environment and Pollution, 41 (3 -4), 214-228. (UN) United Nations General Assembly. (2000). United Nation Millennium Declaration. Retrieved October 2010, from http://www.un.org/millennium/ declaration/ares552e.pdf (USDA) United States Department of Agriculture Food and Nutrition Service. (2006). How Much Do You Eat? Retrieved November 2011, from http://www.fns.usda.gov/tn/Resources/howmuch.pdf (US EPA) United States Environmental Protection Agency. (2002a). Wastewater Technology Factsheet: Facultative Lagoons. Retrieved December 2011, from http://water.epa.gov/scitech/wastetech/upload/ 2002_10_15_mtb_ faclagon.pdf (US EPA) United States Environmental Protection Agency. (2002b). National Recommended Water Quality Criteria: 2002. Washington, D.C., USA: Office of Water, EPA -822-R -02-047. (USDS) United States Department of State. (2011). Embassy of the United States Lusaka, Zambia. Retrieved February 2011, from Rural Aquaculture Promotion Project: http://zambia.usembassy.gov/zambia/rapp.html Wang, R., Wong, M.-H., & Wang, W.-X. (2010). Mercury exposure in the freshwater tilapia Oreochromis niloticus. Environmental Pollution, 158, 2694-2701. (WHO) World Health Organization. (2006). Guidelines for the Safe Use of Wastewater, Excreta and Greywater. Volume 3: Wastewater and Excreta Use in Aquaculture. Geneva: World Health Organization. (WHO) World Health Organization. (2007). Exposure to mercury: A major public health concern. Geneva, Switzerland: WHO. (WHO; FAO) World Heal th Organization, Food and Aquaculture Organization of the United Nations; United Nations University. (2007). Protein and Amino Acid Requirements in Human Nutrition. Geneva: World Health Organization.
77 APPE NDICES
78 Appendix A: Summary of Water R ecycling G uidelines and M andatory Standards in the U.S. and Other C ountries Many countries have set guidelines or mandatory performance targets for the treatment of wastewater intended for reuse. The following table presents some of these guidelines (g) an d mandatory performance targets (m). (US EPA, 2002) Country/ Region Fecal Colifroms (CFU/100 mL) Helminth Eggs BOD5 (ppm) Turbidity (NTU) Total Suspended Solids (ppm) pH Chlorine Residual (ppm) Arizona < 1 1 4.5 9 California 2 Cyrpus 50 10 10 France <1,000 <1 Florida 25 for any sample 75% (m) 20 (m) 5 (m) Germany 100 (g) 20 (g) 1 2 (m) 30 6 9 Japan 10 (m) 10 (m) 5 (m) 6 9 (m) Israel 15 15 0.5 South Africa 0 (g) US EPA 14 for any sample, 0 for 90% (g) 10 (g) 2 (g) 6 9 (g) 1 (g)
79 Appendix B: Considerations for National Wastewater and Excreta Use P olicies Presented in the WHO Report on Wastewater Reuse in A quaculture Policy priorities for each country are necessarily different to reflect local conditions. National policy on the use of wastewater and excreta in aquaculture needs to consider various issues, including: the health implications of wastewater and excreta use in aquaculture (requirement for a health impact assessment prior to large scale project implementation and setting of appropriate standards and regulations water scarcity the amount of wastewater and excreta generated now and in the future the locations where excreta are generated the acceptability of wastewater and excreta use in aquaculture the extent and types of wastewater and excreta use currently practiced the ability to effectively treat wastewater and excreta and implement other health protection measures downstream impacts if wastewater and excreta are not used for aquaculture number of people dependent upon wastewater and excreta use in aquaculture for their livelihoods trade implications of exporting fish or plants produced with wastewater and excreta Reproduced from the World Health Organization (WHO, 2006)
80 Appendix C : Total Protein Supply by Continent and Major Food G roup Reproduced with permission from the Food and Agriculture Organization of the United Nations ( 2009, p. 63)
81 Appendix D : Characteristics of Commonly Cultured Tilapia S pecies in Zambia Table A Characteristics of reproduction, feeding, and markings for commonly cultured tilapia species in Zambia (Froese & Pauly, 2010) Species Reproduction Feeding Markings/Notes Nile Tilapia Oreochromis niloticus Female mouthbrooder Shallow nests All: phytoplankton, algae Adults: plants Young: Tilapia spot 3 anal spines Vertical stripes throughout caudal fin Dark spot on gill cover Redbrested Bream Tilapia rendalli Both parents guard nest More eggs are laid than mouthbrooders Substrate spawner Young: plankton Adults: wide range including plants, algae, insects, crustaceans Red breast 3 to 5 vertical bars on body Tilapia spot Shallow head Greenheaded Bream Oreochromis macrochir Volcano shaped mound with concave top Female mouthbrooder All: detritus, algae, diatoms Young: invertebrates, zooplankton Fairly plain greenish-gray body Red eye Speckling on body Threespotted Bream Oreochromis andersonii Female mouthbrooder Saucer -shaped nests, paternal care after hatching All: detritus, diatoms, zooplankton Adults: insects, invertebrates Three dark spots on sides of body Red edge on dorsal and caudal fin Dark spot on gill cover
82 Appendix D Continued Figure A Nile Tilapia Oreochromis niloticus Figure B Redbreasted Bream Tilapia rendalli
83 Appendix D Continued Figure C Greenheaded Bream Oreochromis macrochir Figure D Threespotted Bream Oreochromis andersonii
84 Appendix E: Composition of Fertilizer Used in Semi-I ntensive A quaculture MANURE Nitrogen (N) Ph osphorus (P) Potassium (K) % pts. % pts. % pts. C:N ratio cow 1.91 5 0.56 3 1.4 2 19 sheep 1.87 5 0.79 4 0.92 2 29 goat 1.5 5 0.72 4 1.38 2 pig 2.8 7 1.36 5 1.18 2 13 chicken 3.77 8 1.89 6 1.76 3 9 duck 2.15 7 1.13 5 1.15 2 10 rabbit 1.72 5 1.3 4 1.08 1 bat 10 10 4 6 2.5 2 ASH Nitrogen (N) Phosphorus (P) Potassium (K) % pts. % pts. % pts. C:N ratio banana fodder 3 6 10 maize cobs 2 6 50 20 maize stalks 0.3 2 0.13 3 0.33 2 groundnut shells 2 4 5 orange/lemon peels 2 6 8 cucumber skins 1 5 2 wood ifimuti 3 1.8 6 5 8 peapods 2 4 8 grass 2 3 3 charcoal (from brazier) 2 4 5 WASTES Nitrogen (N) Phosphorus (P) Potassium (K) % pts. % pts. % pts. C:N ratio banana peels 1 5 10 cassava peels 1 2 1 sweet potato peels 1 2 4
85 Appendix E Continued bone meal 3 5 1 coffee grounds 1.79 2 0.12 1 1.8 2 eggshells 1 1 1 feathers 5 0 0 fish bones 2 5 2 groundnut shells 3 3 2 soya meal 7 1 2.28 0 1.02 1 blood 2 5 2 ground/dried fish 2 5 2 maize cobs 0 1 10 groundnut hulls 0.59 5 4 1 soya oil cakes 6.95 5 2.88 3 1.02 1 LEAVES AND STEMS Nitrogen (N) Phosphorus (P) Potassium (K) % pts. % pts. % pts. C:N ratio cowpea fodder 3 2 2 maize stalks 0.3 1 0.13 2 0.33 1 55 maize straw 0.59 1 0.31 2 1.31 2 55 rice straw 0.58 1 0.1 1 1.38 2 105 rice husks 1 1 0 soya straw 0.59 1 2 1 19 soya leaves 1.3 2 11 0 32 groundnut leaves 2.8 2 0.2 2 1 groundnut straw 1 2 1 tobacco leaves 5 2 1 tobacco stems/stalks 4 1 6 banana leaves 1 5 8 banana stalks 1 4 8
86 Appendix E Continued g rass 0.41 1 0.03 0 0.26 1 20 green weeds 2.45 4 3 3 13 leucaena 2.45 6 0.07 3 2 sugar cane hulls 0.35 1 0.04 1 0.5 1 116 senna 10 4 2 blackjack 6 5 6 beans leaves 2 2 1 sweet potato leaves 1 2 1 pigeon pea 1 2 3 lantanna 8 6 8 tomato leaves 1 1 1 sunflower leaves 1 2 1 velvet beans leaves 4 2 2 COMMERCIAL FERTILIZERS Nitrogen (N) Phosphorus (P) Potassium (K) % pts. % pts. % pts. C:N ratio D Compound 10 15 20 25 10 15 Ammonium Nitrate 34 20 0 0 0 0 Urea 46 30 0 0 0 0
87 Appendix F : Guide to Supplemental Feeding and Formulating Tilapia Feeds Table B provides many resources which are locally available in Zambia. Often these are plants, tree leaves, farm wastes, and kitchen wastes that can be obtained for free. Formulating fish feeds for semi -intensive fish farming system is never an exact science, but having a set of guidelines can help while experimenting with different feed combinations. The four main components of fish feeds are carbohydrates, fiber, protein, and lipids. At the ver y end of the table, point requirements are listed depending on the age of the fish, the farmer selects the total point values for each of the four components. The farmer then combines various available resources to meet these values as closely as possible. The point values are based on the weight of the substance. Therefore, if one kilogram of termites is used in the feed, then one kilogram of fresh cassava leaves should be used (unless the substance is stated as dried). When adding equal parts by weight, the point values for each can be added together to evaluate the ratio of different feed components. Examples are given after the table to demonstrate this process. Table B Supplement feeds: components and point values CEREALS AND GRAINS Protein Carbohydrates Fiber Lipids % points % points % points % points sorghum (grain) 10.6 8 71.4 50 1.9 1 3 2 sorghum (bran) 7.8 5 65.7 48 7.6 5 4.8 3 maize (meal) 9.6 6 70.8 50 2 1 3.9 2 maize (bran) 2.1 1 57.8 42 36.5 25 0.8 0 millet (grain) 11.2 8 64.6 48 6.3 5 3.9 2 millet (hulls) 4.8 3 41.2 30 38.3 30 1.3 1
88 Appendix F Continued Table B Continued wheat (grain) 12 10 70 50 2.5 2 1.7 1 wheat (bran) 14.7 11 53.5 40 9.9 6 4 2 rice (mill sweepings) 8 8 40 30 32 10 5 6 rice (bran) 11 6 43 30 14 24 10 3 ROOT CROPS AND PRODUCTS Protein Carbohydrates Fiber Lipids % points % points % points % points sweet potato (fresh tuber) 1.5 1 25.6 20 0.8 0 0.3 1 sweet potato (dried tuber) 4.2 3 74.9 55 4.2 1 0.7 5 sweet potato peelings 0.7 0 10.2 6 0.1 5 0.2 6 cassava (fresh tuber) 0.9 0 30.9 20 1 2 0.2 2 cassava (dried tuber / meal) 2.1 1 77.9 55 3.8 1 0.5 2 cassava peelings 1.6 1 20.1 15 4.4 2 0.4 5 Irish potato (fresh tuber) 1 1 17.7 12 3 3 INSECTS AND ANIMAL PRODUCTS Protein Carbohydrates Fiber Lipids % points % points % points % points blood meal 81.5 60 1.6 1 0.7 0 1 1 waste fish 67 50 14.9 10 1 1 9.1 5 termites 15 40 10 5 6 locusts 30 5 2 2 earthworm 50.2 35 5 1 1.4 2 maggot 48.7 35 12 5 5 2 8.1 5 crab meal 50 35 10 3 5 3 frog (pieces) 30 5 2 4
89 Appendix F Continued Table B Continued OIL SEEDS/CAKES AND BEANS Protein Carbohydrates Fiber Lipids % points % points % points % points coffee meal 10 8 48.6 35 25 18 15 10 cowpea bean 23 15 67 50 6 4 5 3 velvet beans 3.4 2 7.2 5 5.8 4 0.5 0 groundnut (seed) 28.4 20 15.9 10 2.2 1 45 30 groundnut (shells) 6.2 4 21.4 15 54.3 40 1.6 1 groundnut oil cakes 46.2 35 24.8 18 7.5 5 6.7 5 sunflower (seed) 25.7 20 16.3 12 5 3 44 30 sunflower (hulls) 9.8 8 38.1 25 36.4 25 1.7 1 sunflower head and seed 13.1 10 32.8 25 23.4 15 13 8 sunflower oil cakes 37.1 28 27.2 20 12.7 8 9.3 6 soya (seed) 37.8 28 25.6 20 4.9 3 18 12 soya (hull) 9.8 6 38.1 30 36.4 26 1.7 1 soya oil cake 41.6 30 30.1 22 5.9 4 5.3 4 soya (meal) 35 25 20 4 2 pigeon pea 20 15 58 40 7 5 2 1 WASTES Protein Carbohydrates Fiber Lipids % points % points % points % points beer waste 22 15 20 6.75 10 3.96 5 leftovers (nshima) 1 30 5 5
90 Appendix F Continued Table B Continued LEAVES Protein Carbohydrates Fiber Lipids % points % points % points % points cassava leaves 25 20 7.7 5 2.1 2 0.8 0 leucaena(soaked and dried) 29.1 22 20 12.6 10 6.2 5 soya leaves 4.7 3 5.7 4 1.1 1 0.6 0 pumpkin leaves 5 5 2 0 beans leaves 3 4 1 0 cabbage 1.7 3 4 2 0 sweet potato leaves 2 10 8 2 0 blackjack 8 8 2 0 pawpaw leaves 10 5 1 0 groundnut leaves 3 4 1 0 rape 3 2 5 2 0 okra 2 1 6 4 1 1 0 0 squash leaves 2 4 1 0 cocoyam leaves 2 4 1 0 chinese cabbage 3 5 2 0 FRUITS Protein Carbohydrates Fiber Lipids % points % points % points % points avacado 10 15 2 15 banana 2 15 3 2 pawpaw 1 2 4 0 mango 2 2 5 0 guava 2 2 4 0 impundu 1 1 3 0 imfungo 1 1 3 0
91 Appendix F Continued Table B Continued PLANKTON Protein Carbohydrates Fiber Lipids % points % points % points % points phytoplankton 20 15 20 10 5 zooplankton 65 45 20 5 5 FEED REQUIREMENTS FOR TILAPIA Size Approximate age % Protein %Carb % Fiber % Lipids 0 -0.5g 0-2 weeks 50 25 8 10 0.5-1.0g 2-6 weeks 35-40 25 8 10 10-35g 2-3 months 30-35 25 8 to 10 6 to 10 35g-adult 3 mts adult 25-30 25 8 to 10 6 POINT REQUIREMENTS Size Age Protein Carbohydrate Fiber Lipids 0 -0.5g 0-2 weeks 100 45 15 15 0.5-1.0g 2-6 weeks 120 70 25 25 10-35g 2-3 months 130 90 45 45 35g-adult 3 mts adult 170 130 60 40
92 Appendix F Continued Ba Chilufya is feeding his fish which are 2-3 months old maize meal, sweet potato leaves, and beer waste. Are these feeds adequate? For fish that are 2-3 months old, our goals are: Goals: Protein 130, Carbohydrates 90, Fiber 45, Lipids 45 His feeds have the following point values: Maize meal : Protein 6, Carbohydrates 50, Fiber 1, Lipids 2 Sweet potato leaves : Protein 10, Carbohydrates 8, Fiber 2, Lipids 0 Beer waste: Protein 15, C arbohydrates 20, Fiber 10, Lipids 5 Total: Protein 31, Carbohydrates 78, Fiber 13, Lipids 7 You can see that these feeds do not meet the necessary ratios. Ba Chilufya is close for carbohydrates but he needs to look for more fiber lipids and a lot more protein. If his pond is well fertilized, we can add phytoplankton and zooplankton: Previous total : Protein 31 Carbohydrates 78, Fiber 13, Lipids 7 Phytoplankton: Protein 15, Carbohydrates 20, Fiber 10, Lipids 5 Z ooplankton : Protein 45, C arbohydrates 20, Fiber 5 Lipids 5 Total: Protein 60, Carbohydrates 118, Fiber 28, Lipids 17 You can see that this still does not meet our goals. He has too much carbohydrates and not enough protein, fiber, or lipids Ba Chilufya should look for feeds that have these thi ngs (especially protein ).
93 Appendix F Continued Ba Kabaso has fish that are 2-6 weeks old. He is feeding them termites, sunflower oil cakes, cassava leaves, and pigeon pea. Are his feeds adequate? For fish that are 2-6 weeks old, our goals are: Goals: Protein 120, Carbohydrates 70, Fiber 25, Lipids 25 His feeds have the following point values: Termites : Protein 40, Carbohydrates 10, Fiber 5 Lipids 6 Sunflower oil cakes : Protein 28, C arbohydrates 20, Fiber 8 Lipids 6 Cassava leaves : Protein 20, Carbohydrates 5, Fiber 2 Lipids 0 Pigeon pea: Protein 15, C arbohydrates 40, Fiber 5 Lipids 1 Total: Protein 103, Carbohydrates 75, Fiber 20, Lipids 13 You can see that, although not perfect, these feeds come close to the necessary ratios. If we were to add plankton to the feeds, Ba Kabaso would be doing quite well: Previous total: Protein 103, C arbohydrates 75, Fiber 20, Lipids 13 Phytoplankton: Protein 15, Carbohydrates 20, Fiber 10, Lipids 5 Z ooplankton : P rotein 45, C arbohydrates 20, Fiber 5 Lipids 5 Total: Protein 163, Carbohydrates 115, Fiber 35 Lipids 23 Here, Ba Kabaso has more than enough of everything except lipids. He could probably even remove one of the feeds, like pigeon pea, to bring the numbers closer to the proper ratios: Previo us total : Protein 163 Carbohydrates 115, Fiber 35, 23 Removing pigeon pea: Protein -15, Carbohydrates -40, Fiber -20, Lipids 1 Total: Protein 148, C arbohydrates 75, Fiber 15, Lipids 22 These totals are a bit closer to our goals.
94 Appendix F Continued Ba Mumba has fish that are 0-2 weeks old. He is feeding them millet (grain), cassava peelings, mangos, and pumpkin leaves. His pond is poorly fertilized and has very little plankton. Are his feeds adequate? For fish that are 0-2 weeks old, our goals are: Goals: Protein 100, Carbohydrates 45, Fiber 15, Lipids 15 His feeds have the following point values: Millet (grain) : Protein 8 C arbohydrates 48, Fiber 5 Lipids 2 Cassava peelings : Protein 1 C arbohydrates 15, Fiber 2 Lipids 5 Mangos : Protein 2 Carbohydrates 2 Fiber 5 Lipids 0 Pumpkin leaves : Protein 5 Carbohydrates 5 Fiber 2 Lipids 0 Total: Protein 16, C arbohydrates 70, Fiber 14, Lipids 7 Because his pond is poorly fertilized and has very little plankton, we should not allow Ba Mumba to claim the points from plankton. You can see here that Ba Mumba is not even close to reaching the ratios needed for his fish to grow properly. He has too many carbohydrates but is very much short on protein and lipids He needs to improve his managem ent to get a good plankton bloom and look for foods with more protein.
95 Appendix F Continued Ba Bunda has fish that are more than 3 months old. He is feeding them termites, soya meal, leucaena leaves, sunflower seeds, rice bran, and avocados. His pond is very well fertilized and has an excellent plankton bloom. Are his feeds adequate? For fish that are 3 months old, our goals are: Goals: Protein 170, Carbohydrates 130, Fiber 60 Lipids 40 His feeds have the following point values: Soya oil cakes : Protein 30, Carbohydrates 22, Fiber 4 Lipids 4 Leucaena leaves : Protein 22, Carbohydrates 20, Fiber 10, Lipids 5 Sunflower seed: Protein 20, Carbohydrates 12 Lipids 3 Fiber 30 Rice bran: Protein 6 Carbohydrates 30, Fiber 24 Lipids 3 Avocados : Protein 10, Carbohydrates 15, Fiber 2 Lipids 15 Phytoplankton: Protein 15, Carbohydrates 20, Fiber 10, Lipids 5 Z ooplankton : Protein 45, C arbohydrates 20, Fiber 5 Lipids 5 Total: Protein 148, Carbohydrates 139, Fiber 58 Lipids 57 Because his pond is very well fertilized and has a lot of plankton, we should include the points for plankton. You can see here that Ba Bunda is doing very well in his ratios. He is just a bit short on protein but all of the other nutrients are close to their goals. His fish should grow very nicely and he will have a successful harvest.
96 Appendix G : Nutrients Found in Human E xcrement Table C characterizes nutrients typically found in the urine and feces of humans. Table C Nutrients found in human feces and urine Nutrient Urine (kg/per yr) Feces (kg/per yr) Total (kg/per yr) % of Nutrient Found in Urine Nitrogen 4.0 0.5 4.5 89% Phosphorus 0.4 0.2 0.6 67% Potassium 0.9 0.3 1.2 75% Source: Swedish data (Drangert, 1998:161) Nitrogen 2.4 0.3 2.7 2.7 3.9 81 89% Phosphorus 0.2 0.37 0.1 0.2 0.3 0.57 65 67% Source: (Kvarnstrom et al., 2006:3)
97 Appendix H : Equation for the Modeling of Fecal Coliform Removal in Lagoons Modeling of fecal coliform removal in lagoons and fish ponds was performed in the study of the Kolkata wetlands study (Bunting, 2006) The removal was dependent on the temperature and the retention time of the lagoons Equation A where Np is the fecal coliforms (per 100 mL) in fishpond; Ni the fecal coliforms (per 100 mL) in untreated wastewater; kT the rate constant for fecal coliforms removal (per day); a the anaerobic retention time (day-1); f the facultative retention time (day-1); p the fish pond retention time (day-1) (Bunting, 2006) : Equation A Estimation of fecal coliform removal in lagoons = 1 ( 1 + ) 1 + 1 + = 2 6 (1 19 ) Longer retention times and higher temperatures reduce the number of fecal coliforms expected in the fish pond.
98 Appendix I : World Health Organization Reported Safe Levels of Protein Intake for Adult Men and Women Body Weight (kg) Safe Level (g/kg day )b 40 33 45 37 50 42 55 46 60 50 65 54 70 58 75 62 80 66 a all ages >18 years b 0.83 g/kg per day of protein with a protein digestibility -corrected amino acid score value of 1.0 Reproduced with permission from the World Health Organization (WHO; FAO, 2007, pp. 243)
99 Appendix J: Concise Rural Aquaculture Promotion (RAP) Program Pond C onstruction M anual Site Selection Water The most important factor in choosing a site for a fish pond is water supply. The most ideal source of water will be from a furrow. The furrow should have a flow that is able to sustain the level of water in the pond even during the driest months of the year. Generally farmers will know their land well enough to make this judgment on their own. However, measurements can be made during the driest month to conclude whether the furrow can support a pond or system of multiple ponds. To ensure that one pond can be filled the flow rate of the furrow should be at least 5 liters per minute per are1 Example: 10 22 60 = 27 3 Fill a large bucket, timing how long it takes to fill. Then calculate the flow rate using the following equation. ( ) ( ) 60 = Figure E Calculation for flow rate from a furrow 1 are 100 meters square a 1.5 are pond is 10 by 15 meters
100 Appendix J Continued You m ust also consider the quality of the water. If the water is potentially contaminated by upstream farming practices then communication between the farmers will be important. The downstream farmer will have to manage the flow of water into the pond to prevent harming the fish. For example, if the upstream farmer will be spraying pesticides on his crops, than the downstream farmer will want to consider blocking the flow into the pond for a period of time after the spraying. The farmer will also want to ensure that they have the rights to use the water for farming practices. Water disputes are a common problem in Zambia. Local methods of ensuring that the farmer will have continued rights to using the water should be pursued before the pond is built. The farmer should also maintain a good relationship with other stakeholders in the water source to reduce the possibility of sabotage due to jealousy. Slope The slope of the land at the site should be between 2 and 15 percent. This will ensure that the pond is drainable for harvesting. If the land is flat the pond will not be able to drain. If land is too steep the pond will require too much digging and be difficult to construct. The following illustrations show a method for measuring and calculating the slope of the land.
101 Appendix J Continued Tools: two large sticks about 2 meters long 10 meters of string measuring tape line level Technique: 1. Tie one end of the twine to one of the sticks. 2. Have one person hold this stick vertical. 3. A second person should walk down the slop of the land and pull the string taught. Ensure that vegetation does is cleared away from the string so there is a good reading. 4. A third person should mount the line level in the middle of the string and have the second person adjust the height of the string until it is level. 5. The third person should measure the height of the string from the ground at both ends of the string. These are A and B as shown in the picture. Calculation: = 10 100 % Example: = 1 6 7 10 100% = 9 % Figure F Measuring the slope of a valley
102 Appendix J Continued Soil Having the proper type of soil will keep the pond from leaking too much. If the pond is built on very sandy or rocky soil then water seepage out of the pond will require continuous filling of the pond which is not ideal. Rocky soil is also difficult to dig in. Soil that is high in clay content is best. To check the soil texture and rate of seepage the two following methods can be used.
103 Appendix J Continued Ball Test: 1. Dig to the layer of soil below the top soil. 2. Wet the soil. 3. Collect a piece of soil and form a ball. 4. If you can toss the ball into the air and catch it then the soil has a sufficient amount of clay. If the ball breaks apart then the soil may be too sandy. Hole Test: 1. Dig a one-meter deep hole in the ground at the site. 2. Fill this hole with water. 3. Allow the water to go down then refill it. 4. Repeat this filling three times. 5. If the hole seems hold water well after this process than the site is likely a good location for a pond. Figure G Methods for testing soil
104 Appendix J Continued Vegetation The pond should be located in a place where it can have direct sunlight all day. If the site requires that you clear many trees this is work which could be avoided by choosing a site that is already in an open area. Also tree roots may be difficult to remove. If they rot there is a risk that leaks could form in the pond bottom or dike walls. Planning Farmers fields are often located far from their homes. The RAP standard encourages farmers to locate their pond within a 10 to 15 minute walk from the home. This reduces the risk of theft and makes it easier for the family to visit the pond daily for maintenance and monitoring. The farmer should consider whether they would like to add more ponds in the future. If so the location should be able to accommodate future constructions. Family and farm integration is an important part of rural aquaculture extension in Zambia. A good example of pond integration would be use pond effluent to irrigate and fertiliz e vegetable gardens. This type of integration should be considered when locating the pond. If it is placed as high as possible on the valley wall then the effluents could be easily directed into a vegetable garden. Pond Design The pond design promoted by the Zambian Department of Fisheries has specific features which they have deemed optimal for fish production in rural Zambia. These features are called the rural aquaculture project standard, or RAP standard. Many of these features are different from traditional ponds found throughout the country.
105 Appendix J Continued Slopes Traditional ponds walls are dug vertically into the ground. The RAP standard pond has inner and outer dike walls that are sloped. The slopes on the inside of the pond are used as breeding locations. The slope also creates a varying depth of water across the pond. This allows for the formation of a thermocline. Along the pond edges the water will be warmer; at the center of the pond the water will be cooler. This helps the fish to find an optimal temperature, especially during the cooler months. The slopes on the inside and outside of the dike walls ensure the strength of the walls, which is especially important during heavy rainfall. The slopes also make the pond easier to harvest since one can simply walk from the top of the wall into the pond. Having slopes also makes the pond safer since children are not likely to fall into the water or of the outside edge of the wall.
106 Appendix J Continued The following illustration describes the R AP standard slope for inner and outer dike walls. Inner dike wall: Outer dike wall: Figure H Schematic showing interior and exterior slopes of a RAP standard pond Inlets and Outlets The most common inlets and outlets for ponds are recycled pipes. Since pipes can sometimes be difficult to find in the rural setting other methods may need to be improvised for controlling the entrance and exit of water from the pond. 2 meters 1 meter 3 meters 1 meter
107 Appendix J Continued Inlet pipes are important because they allow the farmer to control the flow of water into the pond. The exit or overflow pipes prevent water from spilling over the top of the dike walls. This is especially important during heavy rainfall events when water running over the top of the wall could erode the wall, compromising its strength and possibly leading to its collapse and the loss of fish. If pipes are used the framer may want to add a hard surface to buffer the flow of water, preventing erosion of the dike wall. The pipes should also be screened to prevent trash fish from entering the pond, or good fish from exiting the pond. A pond generally has one inlet. However, the number of overflow pipes is based on the size of the pond. For each are the pond s hould have one overflow pipe. A 10 x 15 meter pond is 1.5 ares and would require to pipes to ensure that enough water could exit in a heavy rain event. These overflow pipes should be buried 30 centimeters below the top of the dike wall. This way water can never reach the top of the wall. This buffer zone is called the freeboard. Freeboard: 30 cm Stones to prevent erosion Figure I Typical setup of an overflow pipe
108 Appendix J Continued Size The size of the pond depends on the resources available and the amount of time the farmer can dedicate to maintaining. Some farmers have constructed a pond of one hectare. However, new farmers are recommended to start with a 10 meter by 15 meter pond. This allows the farmer to gauge how much time and the amount of resources they will require to maintain the pond. Smaller ponds also reduce the risks associated with disease and theft. If a disease enters the pond or somebody poisons the fish in the pond, the loss associated with one 1.5 are pond is much less than a 100 are pond. Pond Measurement and Construction The following steps outline the process for constructing a RAP standard fish pond. Cl ear the site of debris and large trees. Stake the four corners of the pond. After this stake the four outside corners of the dike walls. Determine height of dike walls with level. Choose the height just above the earth at the highest corner. Then using a line level tie the string from corner to corner so that the height of the dike wall on the inner perimeter can by visualized and used as a guide for wall construction.
109 Appendix J Continued The inner box must be determined. Using the RAP standard slopes, two corners of the inner box will be 3.3 meters (1.1m 3 slope) from the up-slope corners. The other two will be 3.9 meters (1.3m 3 slope) from the down-slope corners. This is shown in Figure J : Remove the top soil from the entire construction area. Determine the depth which must be dug out at each corner of the inner box. Begin by digging the inner box. Figure K shows progress after having completed this step. stake 3.3 m 3.3 m 3.3 m 3.3 m Inner Box 3.9 m 3.9 m 3.9 m 3.9 m Figure J Layout for staking of a fish pond and its i nner box
110 Appendix J Continued Figure K Photo of pond construction after completion of the inner box After completing the inner box, soil is removed to form the inner pond slopes. This soil is used to build the dike walls. For every 30 cm of wall constructi on, the soil must be compacted. Figure L Photo showing the completion of pond slope construction and leveling of dike walls
111 Appendix J Continued Figure L shows the completion of the dike walls. The inner slopes and walls must be well compacted. Place the inlet and outlet pipes in the dike walls. Build compost bins. Screen the inlet and outlet pipes. Plant grass on the top and outside slopes of the dike walls. Pond Management Basic pond management was taught as the 7-1 -2 method of pond maintenance. This helps to remind farmers that there are seven, one, and two tasks to be performed each day, week, and month respectively. Daily 1. Feed and observe fish. 2. Clear frog eggs and check for predators. 3. Stir compost and remove twigs and sticks. 4. Speeds the release of compost nutrients into the water. 5. Check water level. 6. Check walls for leaks. 7. Check the furrow for blockages. 8. Clear pipes and screens. Weekly 1. Fill compost. Monthly 1. Cut grass on dikes and around pond. Remove grass form inside pond.
ABOUT THE AUTHOR Joshua Girard is a graduate student in the Department of Civil and Environmental Engineering at the University of South Florida (Class 2011). As a Masters International student his academic interests include the many environmental engineering chall enges facing the developing world. His course of study has included a range of topics from conventional water/wastewater treatment, air quality, sociology of the environment, general sustainability, and appropriate technology. From July 2008 to April 2010, Joshua served as a Rural Aquaculture Extension agent with the United States Peace Corps in Zambia. He participated in nine weeks of cultural, language (Bemba), aquaculture, and HIV/AIDS training. Following training he moved to his host community where he conducted farmer evaluations, fish farming workshops, farmer site visits, and community based HIV/AIDS education. Joshua grew up in southern Maine, USA. He completed his Bachelor of Science in M echanical Engineering at Boston University in 2007. He has studied abroad in Germany in 2005, where he began learning German. Outside of engineering and academics his interests include traveling, gardening, and current events. He would like to return to Zambia in the future to work in fields relating to aquaculture, transportation, or water/sanitation, incorporating his passion for people and the environment through sustainable technologies.