Determining the filtration quality of different soil types using turbidity, bacterial content, and drainage ability for filtering greywater

Determining the filtration quality of different soil types using turbidity, bacterial content, and drainage ability for filtering greywater

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Determining the filtration quality of different soil types using turbidity, bacterial content, and drainage ability for filtering greywater
Translated Title:
Determinando la calidad de filtración de diferentes tipos de suelos usando turbiedad de contenido bacterial, yla abilidad de drenaje para filtrar aguas grises
Esclamado, Janelle Luz S
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Subjects / Keywords:
Grey water
Aguas grises
Filtration quality
Calidad de filtración
Soil types
Tipos de suelo
Books / Reports / Directories ( local )
Books / Reports / Directories ( local )



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M36-00457-ML-1063 ( USFLDC DOI )
m36.457-ml-1063 ( USFLDC Handle )

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Esclamado, Janelle Luz S.
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Determinando la calidad de filtracin de diferentes tipos de suelos usando turbiedad de contenido bacterial, yla abilidad de drenaje para filtrar aguas grises.
Determining the filtration quality of different soil types using turbidity, bacterial content, and drainage ability for filtering greywater.
g Otoo 2006/Fall 2006.
Books / Reports / Directories
2 local
Grey water
Aguas grises
Filtration quality
Calidad de filtracin
Soil types
Tipos de suelo
Scanned by Monteverde Institute.
The State of Water in Monteverde, Costa Rica: A Resource Inventory.
4 856


Greywater Filtration Esclamado 1 Determining the Filtration Quality of Different Soil Types Using Turbidity, Bacterial Content, and Drainage Ability for Filtering Greywater Janelle Luz S. Esclamado University of California, Irvine EAP Tropical Biology Program, Fall 2006 Abstract Greywater is wastewater produced by shower s and sinks and thus contains soaps, food particles, and bacteria. In the vast majority of Monteverde, greywater is disposed of onto the ground or streets, and is directed to the nearest stream. This wastewater may seep into the regional groundwater and can potentially transmit water-borne di seases. I investigated the filtration qualities of clay, organic soil, and gravel. Measuring the changes in bacterial count, turbidity, and the percentage of initial volume recovered, I determined the best soil for greywater filtration. In addition, I used my results to suggest an alternative media to be used in wastewater trench constructi on. I found that clay filtration produced the greatest reduction in bacteria and organic soil recovered the least amount of water. I did not find differences in the change of light absorbance of the water sa mples between soil types. I concluded that clays natural characteristics should be used as a small scale water filter where drainage is not an issue. I also concluded that gravel s hould remain the medium used in wastewater trench construction because of its drainage ab ilities, lack of ecological importance, and commercial availability. Resumen Agua gris es aguas residuales producidas por las duchas y los fregad eros y contiene as los jabones, las partculas del alimento, y la s bacterias. En la mayora extensa de Monteverde, el greywater se dispon e sobre la tierra o las calles, y se dirige a la corriente ms cercana. Estas aguas residuales pueden filtrar en la agua subterrnea regional y pueden potencialmente transmitir enfermedades flotantes. Investigu las calidades de la filtracin de la arcilla, del suelo orgnico, y de la grava. Midiendo los cambios en cuenta bacteriana, la turbiedad, y el porcentaje del volumen inicial me recuperaron determinaron el mejor suelo para la filtracin del greywater. Adems, utilic mis resultados para sugerir los medios alternativos que se utilizarn en la construccin del foso de la s aguas residuales. Encontr que la filtracin de la arcilla produjo la reduccin ms grande de bacterias y el suelo orgnico recuper la menos cantidad de agua. No encont r diferencias en el cambio de la absorbencia ligera del agua entre los tipos de l suelo. Conclu que las caractersticas naturales de la arcilla se deben utilizar como filtro del agua de la escala pequea donde no est una edicin el drenaje. Tambin conclu que la grava perman ece como el medio usado en la construccin del foso de las aguas residuales debido a sus capacidades del drenaje, la carencia de la importancia ecolgica, y la disponibilidad comercial.


Greywater Filtration Esclamado 2 Greywater is wastewater produced by shower s, baths and basins (55%), laundry (34%), and the kitchen (11%) (Dallas 2005). Greywa ter may contain soaps, detergents, food particles, grease, lint, hair, bacteria and traces of othe r household cleaning products. The presence of soaps, suspended matter such as organic matter, inorganic matter, plankton and other microscopic organisms causes a change in the waters clarity, namely its turbidity. Turbidity is an expression of the optical property that causes light to be scattered and absorbed rather than transmitted with no change in direction of flux level through the sample (Eaton 1995). The clarity of a natural bo dy of water is an important determinant of its condition because it could be an indicator of water quality. Untreat ed greywater thus got its name based on its turbid nature. Currently, domestic greywater is discharged from the house, untreated, into the streets and streams of Monteverde (Dal las 2005). Untreated greywate r can thus pose as a breeding ground for various pathogenic bacteria, parasites, and viruses which may lead to many health risks. Some waterborne pathoge nic diseases include ear infec tions, dysentery, typhoid fever, viral and bacterial gastroenteritis, and hepatitis A. Among others, E. coli is a bacteria usually found in household greywater. The presen ce of fecal coliforms, particularly E. coli indicate that there are mammal or bird feces in the water (Ludwig 2006). In most instances, coliforms themselves are not the cause of sickness, but th ey are easy to culture and their presence is used to indicate that other pathogenic organism s of fecal origin may be present. Though often harmless, E. coli can cause illness by infection of a bod ily cavity or by synthesis of a toxin which attacks the body (CDC 2006). Fecal colifor m bacteria may occur in ambient water as a result of the overflow of domestic sewage or nonpoint sources of human and animal waste. In Monteverde, little research has been done about the effects of soil as a filter for the treatment of wastewater with resp ect to turbidity and bacterial content. As for soils, clay is known to be very cohesive, have a large surf ace area-to-volume ratio, and to slow down the movement of water. Organic soil is very arid and permeable to air and water while gravel is loose and lacks cohesiveness. It is not yet known whether these soil characteristics play a role in affecting the turbidity or bact erial content for filtering wastewater. With this project I wanted to find out which so il best filters the disc harged greywater as it trickles towards the nearest stream in addition to discovering a better alternative for the current medium, gravel, used in wastewater trench construction. I investigated three different types of soil; clay, organic soil, and gravel. Clay has relatively small particles, organic has slightly bigger par ticles, and gravel has the biggest particles (Brady 1996). I also wanted to find out if particle size played a role in a soils filtration qualities. In this paper, I assessed the filtering qua lities of three different soil types by analyzing the change in bacterial count, and turbidity of the water after passing through each soil. I postulated that the soil with a finer texture a nd less pore space will serve as a better filter since the water would have to move thr ough a finer matrix which may remove more unsanitary debris (Brady 1996).


Greywater Filtration Esclamado 3 Materials and Methods Experiment Location I conducted this study at the Instituto Monteverde in M onteverde, Puntarenas, Costa Rica, from November 24 to December 3 of 2006. I collected the soils used for the project from the Gindon Maxon Farm. I collected th e greywater from the Estacin Biolgica Monteverde and from a reside nce in the Manakin neighborhood. Soil Characteristics and Preparation I collected three different types of soils: cla y, organic soil, and gravel Clay is a type of soil that has partic les smaller than 0.002 mm in diameter and a very large surface area-tovolume ratio, giving it a tremendous capacity to adsorb water and ot her substances on its surfaces (Brady 1996). Its large adsorptive surface area also causes clay particles to cohere together in a sticky, plastic mass that can be easily molded when wet (Brady 1996). Organic soils, also known as histosols, are far more pe rmeable to air and wate r with particles about 0.05mm in diameter (Brady 1996). Gravel has particles that are greater than 2 mm in diameter and display very little cohesion or aggr egation into the soil matrix (Brady 1996). In order to ensure homogenous trials, I sepa rately mixed each type of soil in a large container for 5 minutes. Then, to rid the soils of their natural bacterial content, I sterilized each type by heating them at 300 C for one hour (USDA 2000). Apparatus Sterilization and Setup To hold the soil, I sterilized 50cm long PV C pipes, that were 5.08cm in diameter, by pouring 100 C water through them in a bucket (U SDA 2000). For maximum sterilization of the insides of the pipes, I f illed them three-quarters of the height with water then turned over after 30 minutes and left to cool and dry. I sterilized funnels made from aluminum foil and 10cm x 10cm metal squares of window screen (1mm x 1mm grid) molded to the ends of the pipes were sterilized at 300 C for 30 minutes (USDA 2000). After sterilization, I secured the molded screens to the ends of the pipe. Then I filled each pipe with a different soil type and co mpacted them by hitting the pipe on the floor against sterile aluminum foil. I secured ster ile aluminum foil funnels to the end with the screen to direct the resulting sample into st erile collection cups. I then secured the pipes vertically to wooden stands. I re-hydrated the soils because they would have absorbed a ll of the greywater and nothing would have come out. Thus, I hydrated each soil-filled apparatus with 250mL of sterilized water and allowed the water to soak through fo r 12 hours. I then placed a column, weighing the respective masses of each 50cm soil-filled pi pe, on top of their respective soil samples after re-hydration in or der to standardize the degree of compactness amongst each soil type. I did this to recreate the natura l soil compaction of a typical home drainage system and came from the fact that 50cm is the standard dept h of drainage pipes used in construction. For each trial there was one pipe for clay so il, one pipe for organic soil, one pipe for gravel, and one pipe for a contro l which contained no soil. I se tup the pipes to perform three trials at a time. Therefore all materials were prepar ed for 12 pipes. In total, I ran six trials in two groups of three trials. For each group, I us ed greywater from different sources.


Greywater Filtration Esclamado 4 Greywater Collection At Estacin Biolgica Monteverde, I determin ed the location of the greywater outlet. I then collected a bucket full of greywater immediately after 30 students ate breakfast and washed their dishes. For the second set of trials, I obtained greywater from a residence in the Manakin neighborhood in Monteverde. I collected the water after the family had taken showers, washed their dishes from break fast, and washed a load of laundry. I sampled the greywater before being poured through the soil pipes as a pre-filtration sample. I then measured 500mL of greywate r for each pipe and poured greywater into the top end of the pipes, allowing the greywater to seep downwards. For each trial, I noted the initial and final volume of greywater that came out. After each trial, I took notice to which soil type was first to produce filtrated water in order to note which type drained water fastest. Analyzing the Samples To determine whether the soils filtered bacter ia, I analyzed the greywater samples before and after they had filtered through the soil. I collected each sample in a 100mL-sterile plastic cup and refrigerated it at 3 C in order to inhibit bacteria l growth (Ambient 2004). From each sample, I pipetted 1mL of filtered greywater onto a 3M E.coli /Coliform Count petrifilm then incubated for 24 hours at 37 C (3M Instruction Manual). The E.coli /Coliform Count petrifilm contains me dia for the growth of both E.coli and coliform. For that, I differentiated the bacterial growth using micr obiological indicators of the bacteria. Fecal coliform produces gas bubbles around its colonies, E.coli forms blue-colored colonies, and non-fecal coliform is the same as fecal colifo rm but does not produce gas around its colonies. After incubation, I counted the number of colony forming units per milliliter of filtered greywater (CFU/mL). If the petrifilm had no evid ence of colonies I did not consider that as zero colonies. Instead, I noted that there were less than two CFUs per milliliter (3M Instruction Manual). If there we re more than ten colonies in any square centimeter, then that samples petrifilm would be appointed as too numerous to be counted (TNC) (3M Instruction Manual). This indicated that there would be more than 220 colonies because the petrifilm has a total area of 20cm 2 (3M Instruction Manual). I also measured the light absorbance of each sample and directly correlated it with turbidity by using the Spectroni c 601 light spectrophotometer. I assumed that the light absorbance reading would indicate the amount of substances suspended in the sample and thus would give me an indicat ion of turbidity. Before obtai ning the readings of the water samples, I found out the wavelength at which the samples would absorb the most light. Generally, I found that clay had the lowest absorbance, organic soil had a moderate absorbance, and gravel had the highest absorban ce at all wavelengths. I did this by manually determining their individual peak wavelengths I found that all soil samples had a peak absorbance at 519nm and used th is wavelength to measure the ab sorbance for all samples. I used one milliliter of the resulting sample and pl aced it in a clean, dry cuvette to be placed in the spectrophotometer. Before each new sa mple, I zeroed the spectrophotometer with a blank cuvette of de-ionized water then inserted the sample. From this procedure, I obtained values in units of absorbance representing the amount of light being absorbed by the water sample.


Greywater Filtration Esclamado 5 Analyzing the Data Being that the colony counts for the petrif ilms did not produce actual numbers for those which had less than two CFUs per milliliter or for those wh ich were counted as TNC, I marked the counts with less than 2 CFUs per milliliter as zero and those with TNC as 220 CFUs per milliliter for statistical purposes. After counting the number of CFUs, I analyzed the differenc e between the types of soils using various indicators of wa ter quality. I calculat ed the percentage of initial volume of water recovered by dividing the final volume by the initial volume, and multiplied that value by 100. I applied this calculation to all trials. To calculate the change in light absorbance, I subtracted the light absorbance reading of th e pre-filtered sample from the final light absorbance reading for each sample. To calculate the change of CFUs per millimeter for E.coli fecal coliform, and total coliform, I subtra cted the initial grey water bacterial count from the final bacterial count per soil type. For my non-parametric data I used KruskalWallis tests in the statistical program JMP to find whether there was a statistical difference of the change they induced in light absorbance, ba cterial count, and percen tage of initial volume recovered, between the greywater filter ed by the different soil types. Results I found that organic soil had recovered an average of 74.67% of the initial greywater, gravel recovered an average of 62.59% of the initi al greywater, clay recovered an average of 38.4% of the initial greywater, and the control recovered 100% of the initial greywater (Fig. 1, Kruskal-Wallis=15.39, df=3, p = 0.0015). For the change in the number of fecal coli form, I found clay produced the greatest change (Fig. 2, Kruskal-Wallis=13.67, df=3, p = 0.0034). Clay also produced the greatest change in the number of total coliform (Fig. 2, Kruskal-Wallis=16.07, df=3, p=0.0011). For E.coli, however, organic soil produced the greatest change (Fig. 2, Kruskal-Wallis=9.51, df=3, p=0.02). I found no difference between the soils ability to significantly alter the waters turbidity (Fig. 3, f=1.42, df=3, df-error=19, p = .27). 62.59 74.67 38.4 100 0 20 40 60 80 100 120 Gravel Organic Clay Control Soil Type% Initial Volume Recovered Fig 1. Percent of initial vol ume recovered per soil type.


Greywater Filtration Esclamado 6 195.2 0 128.5 110.2 142 180.2 0 180.67 104.33 15.33 126.17 28.33-100 -50 0 50 100 150 200 250 Gravel Organic Clay Control Soil TypeChange in # of Bacteria (CFU/mL) Fecal coliform E. Coli Total Coliforms Fig 2. The change in number of greywater bacteria after soil filtration per soil type for the fecal coliform, E.coli, and total coliform. 0.438 0.129 0.4115 0.25 -0.2 0 0.2 0.4 0.6 0.8 1 Control Clay Organic Gravel Soil TypeChange in Light Absorbance Fig 3. Change in light absorbance produced by each soil.


Greywater Filtration Esclamado 7 Discussion The results indicate that orga nic soil drains water the fastes t, gravel drains moderately well, and clay has the worst drainage ability (Fig. 1). This is due to the extensive pore space in organic soil (Brady 1996). Studies have shown that the addition of organic matter makes any soil easier to work with and improves its drainage properties (Whiting 2005). Also, organic soil is not as dense as clay and theref ore does not possess th e ability to become very compact which may contribute to the ability of organic matter to drain water ea sily. It is suggested to add organic matter to minimize soil compaction in gardening (Whiting 2005). Gravel has a greater surface area because of the larger sizes particles making it more likely to catch water on it than organic soil, and thus drains more slowly (Ludwig 2006). The pres ence of clay in a soil gives it a fine texture and slows water and air movement (Brady 1996). As mentioned before, clay has a very large surface area-to-volume ratio, giving it a tremendous capacity to adsorb water and other substances on its surfaces (Brady 1996). The results showed that clay produced the gr eatest reduction in fecal coliform and total coliform (Fig. 2). The reason for this is that clay minerals all have a great affinity for water and have the ability to soak up i ons from a solution (USGS 2006). In addition, the property of clay minerals that causes ions in solution to be fixed on clay surfaces or within internal sites applies to all types of ions, including organic molecules like pesticides (USGS 2006). This allows clay to effectively remove and trap harmful molecules from the water. Similar to clay, organic soil matter has humus which is its colloidal fraction. The surface charges of humus, like those in clay, attract and hold both nutrien t ions and water molecules (Brady 1996). This helps explain why organic soil only had a s lightly greater change in E. coli than clay Gravel does not possess the ability to trap ions due to their loose natu re and lack of cohesiveness and was unable to reduce bacteria as well as clay or organic soil. The results showed that none of the soils produced a significan t difference in the greywaters light absorbance. A possible reason for this could be that miniscule soil sediment in the samples may have interfered with the spectr ophotometric readings. Th is can be especially true in the case of clay because its particles are extremely small. Taking drainage and bacterial removal into account, I consider gravel to be the most suitable medium to use in wastewater trench construction. Although orga nic soil had the best drainage capabilities, it plays an important role in the carbon cy cle, thus rapid extraction of it from nature for commercial pur poses would greatly affect all living organisms (Brady 1996). In effect, the important drainage char acteristic of gravel is its larg e grain size and not its chemical makeup. Thus gravel can easil y be bought from construction supply companies or made by crushing large rocks into much smaller sizes. As for clay, its drainage quali ties are lacking but it does excel in bacterial removal. Thus, I am suggesting that clay be used in a cont ext where time and drainage would not be an important factor but bacterial re moval is and clays attributes can be taken advantage of on a smaller scale than commercial drainage constructi on. The use of clay with this idea has already been implemented by such bodies as the Ceramic Water Filter Project who has developed a lowtech, low-cost, colloidal silve r-enhanced ceramic water filter that effectively eliminates approximately 99.88% of most water-born disease ag ents (Darby 2006). The utilization of clays natural characteristics has already begun to benef it those in undeveloped countries where potable water is inaccessible, thus leading to many waterborne diseases and has th e potential to aid in the purification of water throughout the world. I hope that this st udy can be a stepping stone to further investigation of economical alternatives for filtering wastewater and thus reduce the spread of pathogenic disease.


Greywater Filtration Esclamado 8 Acknowledgements I would like to thank both of my advisors Ramsa Chaves and Ruth Salas for guiding me throughout the entire process and its many revisions. I would also like to thank Erick McAdam and Carlos Alfonso Calvo for their contributions and insights, the Instituto Monteverde for allowing me to use their facilities, and the Estaci n Biolgica Monteverde staff for their help as well as the rest of the UC Education Abroad Program Staff. Literature Cited Ambient. 2004. Inhibitor of Bacterial Growthlow temp erature 13 December 2006. NTS/N%20FoodSafety-Part2-COLD.pdf Brady, N. C. and R.R. Weil. 1996. The Nature and Properties of Soils. Prentice Hall. New Jersey Centers for Disease Control and Prevention (CDC) 2006. Bacterial, Mycotic Diseases. 14 December 2006. Dallas, S. C. 2005. Reedbeds for the Treatment of Greywater as an Application of Ecological Sanitation in Rural Costa Rica, Central America. Darby, K. Filters. 2006. Potters for Peace. 7 December 2006 Eaton, A. D., Clesceri, L. S., and Greenberg, A. E. 1995. Standard Methods for the Examination of Water and Wastewater. 19: Prentice Hall. Maryland. Ludwig, Art. Grey Water. Oasis Design 2006. 6 December 2006 http://www.oasisdesign. net/greywater/index.htm Ludwig, Art. Fecal Coliform. Oasis Design 2006. 6 December 2006 ater/quality/coliform.htm United States Department of Agriculture (USDA). 2000. Instructions for Soil Importation and Soil Sterilization 13 December 2006. http://www.archaeology.hawa United States Geological Survey (USGS). 1999.Environmental Characteristics of Clays and Clay Mineral Deposits. 6 December 2006 Whiting.D, Wilson, C., Card, Soil Compaction. CSU Cooperative Extension-Horticulture 13 December 2005. Colorado State University. 6 December 2006.


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