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Household water treatment systems: A solution to the production of safedrinking water by the low-income communities of Southern Africa

J.K. Mwabi a, F.E. Adeyemo a, T.O. Mahlangu b, B.B. Mamba b, B.M. Brouckaert c, C.D. Swartz c,G. Offringa d, L. Mpenyana-Monyatsi a, M.N.B. Momba a,⇑a Department of Environmental, Water and Earth Science, Tshwane University of Technology, 175 Nelson Mandela Drive, Pretoria 0001, South Africab Department of Chemical Technology, University of Johannesburg, PO Box 17011, Doornfontein 2028, South Africac School of Chemical Engineering, Pollution Research Group, University of KwaZulu-Natal, Durban, South Africad Ikusasa Water Management, Fish Eagle Park, Unit 1, Old Paardevlei Road, Somerset West, South Africa

a r t i c l e i n f o

Article history:Available online 26 August 2011

Keywords:HouseholdTreatmentSystemsSafe drinking waterFiltersWater-borne disease

a b s t r a c t

One of the United Nations Millennium Development Goals is to reduce to half by 2015 the number of peo-ple, worldwide, who lack access to safe water. Due to the numerous deaths and illnesses caused by water-borne pathogens, various household water treatment devices and safe storage technologies have beendeveloped to treat and manage water at the household level. The new approaches that are continuallybeing examined need to be durable, lower in overall cost and more effective in the removal of the con-taminants. In this study, an extensive literature survey was conducted to regroup various householdtreatment devices that are suitable for the inexpensive treatment of water on a household basis. The sur-vey has resulted in the selection of four household treatment devices: the biosand filter (BSF), bucket fil-ter (BF), ceramic candle filter (CCF) and the silver-impregnated porous pot filter (SIPP). The first threefilters were manufactured in a Tshwane University of Technology workshop, using modified designsreported in literature. The SIPP filter is a product of the Tshwane University of Technology. The perfor-mance of the four filters was evaluated in terms of flow rate, physicochemical contaminant (turbidity, flu-orides, phosphates, chlorophyll a, magnesium, calcium and nitrates) and microbial contaminant(Escherichia coli, Vibrio cholerae, Salmonella typhimurium, Shigella dysenteriae) removals. The flow ratesobtained during the study period were within the recommended limits (171 l/h, 167 l/h, 6.4 l/h and3.5 l/h for the BSF, BF, CCF and SIPP, respectively). Using standard methods, the results of the preliminarylaboratory and field studies with spiked and environmental water samples indicated that all filtersdecreased the concentrations of contaminants in test water sources. The most efficiently removed chem-ical contaminant in spiked water was fluoride (99.9%) and the poorest removal efficiency was noted formagnesium (26–56%). A higher performance in chemical contaminant removal was noted with the BF.For pathogenic bacteria, the mean percentage removals ranged between 97% and 100%. Although the con-centrations of most chemical parameters were within the recommended limits in raw surface water, poorremoval efficiencies were recorded for all filters, with the poorest reduction noted with fluorides (16–48%). The average turbidity removals from surface water ranged between 90% and 95% for all filters.The highest bacterial removal efficiency was recorded by the SIPP (99–100%) and the lowest by the BF(20–45%) and the BSF (20–60%). Extensive experimental studies with various types of raw surface waterwill still determine the long-term performance of each filter, as well as the filters that can be recom-mended to the communities for household treatment of drinking water.

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1. Introduction

The most important aspect in improving the health of the peo-ple is to provide communities with safe and clean water. In this,the 21st century, an estimated 1.1 billion people worldwide stilldo not have access to safe potable water. A large percentage of

these people are from the developing world, especially in the ruralareas and low-income communities (WHO/UNICEF, 2006; WHO,2007). Small communities face the greatest difficulty in receivingwater of an adequate quality and quantity because they lack expe-rienced water managers to maintain and upgrade their water sup-ply facilities. Interruptions in water services due to inadequatemanagement as well as violations of drinking water standardsare causing the consumers to be at risk of waterborne diseases,

1474-7065/$ - see front matter � 2011 Elsevier Ltd. All rights reserved.doi:10.1016/j.pce.2011.07.078

⇑ Corresponding author. Tel.: +27 1232 6365.E-mail address: mombamnb@tut.ac.za (M.N.B. Momba).

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even from treated water supplies (MacKintosh and Colvin, 2003;Momba et al., 2005, 2006).

Several studies have shown that water is a source of variouswaterborne infectious diseases affecting numerous communities,particularly those in rural and indigenous areas (Venter, 2000;Murcott, 2006; Momba, 2009) and consequently an estimatedfive million people lose their lives due to water-related diseaseeach year (Pritchard et al., 2009; Baumgartner et al., 2007). Bac-terial pathogens in water tend to cause gastrointestinal infec-tions such as diarrhoea, dysentery, typhoid shigellosis andhuman enteritis (Okoh et al., 2007; Leonard et al., 2003; Venter,2000). The most common cause of illness and deaths in thedeveloping world is a watery diarrhoea called cholera (Clasenet al., 2006) caused by a bacterial pathogen classified as Vibriocholerae (Shultz et al., 2009).

Between August 2008 and January 2009 there was an outbreakof cholera in Southern Africa. The cases of cholera reported in Zim-babwe, Mozambique, Zambia and South Africa were estimated at353300, 10006, 1759 and 1608, respectively (OCHA, 2009). It hasbeen well documented that immunocompromised people, babiesand the elderly are the most susceptible to bacterial infectionsand it is therefore crucial that these people have access to goodquality water on a daily basis (Momba et al., 2008).

Drinking water contains not only microbial contaminants, butalso chemical contaminants that range from organic to inorganiccompounds. Examples of organic chemicals that can be toxic arethe polychlorinated and polybrominated biphenyls (PCBs andPBBs) as well as benzenes. Symptoms of acute toxicity can includediarrhoea, nausea, convulsions, blurred vision, and difficulty inbreathing. Organic pollutants may also cause arteriosclerosis, heartdiseases, hypertension, emphysema, bronchitis, and kidney and li-ver dysfunction (Leivadara et al., 2008). Inorganic chemicals arealso associated with health problems once they enter the humansystem. Nitrates accumulate in the blood stream and result in met-hemoglobinemia, of which a conspicuous symptom is a bluish skin.High concentrations of phosphate can cause health problems suchas kidney damage and osteoporosis (Rose et al., 1996). Other chem-ical contaminants such as chloride, magnesium, iron, aluminium,copper, arsenic and lead can also be present in drinking water.These contaminants pose public health risks at high concentrations(DWAF, 1996).

Point-of-use or household treatment methods can be used toimprove the quality and safety of water for drinking in situationswhere there is no safe centrally treated water supply or wherethe treated water supply system has been compromised. The mostappropriate technology will depend on the situation, the quality ofthe raw water, the availability of the required materials and equip-ment, the time frame in which it is to be used, the customs, pref-erences and education levels of the local population and theavailability of personnel to provide the necessary training andmonitoring for the technology to be successfully implemented.

There is a growing body of literature on household watertreatment and safe storage (HWTSS). Recent studies have shownthat simple and relatively inexpensive home water treatmentand storage methods can result in substantial improvements inthe microbial quality of drinking water and reduced risks ofillness and death, even in the absence of improved sanitation(Sobsey, 2002; Murcott, 2006; Stauber et al., 2006; Clasen andBoisson, 2006; Van Halem et al., 2009; Lantagne and Clasen,2009). Various water treatment devices and safe storage technol-ogies, such as the use of disinfectants (such as chlorine andiodine), filtration, distillation, reverse osmosis, solar disinfectantand water purifiers, have been reported to decrease endemic diar-rhoea caused by waterborne pathogens and to improve themicrobial and chemical quality of drinking water (Sobsey, 2002;Stauber et al., 2006; Murcott, 2006).

In this study, we evaluate the performance of four householdwater treatment systems (HWTS) in removing bacterial and chem-ical contaminants: the biosand filter (BSF), the bucket filter (BF),the ceramic candle filter (CCF) and the silver-impregnated porouspot filter (SIPP). The biosand filter developed by Dr. Manz of theUniversity of Calgary in the early 1990s (Legge, 1996; Samaritans’Purse, 2001) is a modification of slow sand filtration technologyand has been reported to be effective in removing microorganismssuch as bacteria, viruses and protozoa, and chemicals such as iron,manganese and sulphur from water (Cawst, 2008). The biosand fil-ter differs from a simple sand filter in its ability to perform multi-ple functions as a single unit. This filter combines settlement,straining, filtration, removal of chemicals as well as removal ofmicroorganisms to produce safe water (Earwaker, 2006). The mostimportant process in the BSF occurs in a biological layer called theShmutzdecke, which develops on the surface of the uppermostlayer of sand that is responsible for the removal of microorganisms(AWWA, 1991). The bucket filter is a rapid sand filter that consistsof one thick layer of fine sand and a thinner layer of gravel (Sobsey,2002). Rapid sand filtration (filtration rate of 5–20 m/h) is typicallyefficient for the removal of large pathogens such as Giardia cysts,Cryptosporidium cysts, helminths and 50–90% of bacteria (Sobsey,2002). The candle filter consists of one or more candle-shapedceramic filters with two chambers (Nath et al., 2006) and has beenreported to effectively remove turbidity, iron, coliform contami-nants and Escherichia coli from water (Clasen and Boisson, 2006;Lantagne and Clasen, 2009). Ceramic filters are made from clay thatis usually mixed with materials such as sawdust or wheat flour toimprove porosity (Dies, 2003 and Van Halem, 2006). They havemicroscale pores that are effective in removing bacteria from water(Clasen and Boisson, 2006). The pore sizes of ceramic filters areusually between 0.2 and 1 lm and these are able to remove bacte-ria and protozoa. The colloidal silver-impregnated ceramic filter(CSF) consists of a pot-like shaped filter element that is placed ina receptacle. Raw water is poured into the pot and is slowly filteredinto the receptacle through pores in the ceramic element. This potis made from a mixture of clay, sawdust and water, which ispressed into a pot shape with a press mould (Van Halem et al.,2009). When the pot is fired, the sawdust combusts and this cre-ates the pores in the pot. After cooling, the pot is coated with amixture of colloidal silver and water for disinfection purposes. Awell-known and widely used CSF is the Potter for peace, which con-tains 7 l of water and has the capacity to produce 1–3 l of water perhour (Lantagne, 2001).

Although various systems and devices have been extensively re-ported in the literature, little is known locally about the existingoptions and how to assist local communities in making informedchoices on whether a particular system or unit will be appropriateto their situation, or which unit should be selected. A need there-fore exists to source and investigate appropriate units and to deter-mine their efficiency in contaminant removal under localconditions as well as their potential sustainability, and to providesome guidance on both the selection and use of these units underlocal conditions. This preliminary study reports on the perfor-mance of the four filters in terms of flow rate, physicochemicalcontaminants (turbidity, fluorides, phosphates, chlorophyll a, mag-nesium, calcium and nitrates) and microbial contaminant (E. coli, V.cholerae, Salmonella typhimurium, Shigella dysenteriae) removals.

2. Materials and methods

2.1. Design and construction of filters

The devices used in this study were selected according to theirease of use, accessibility locally and low cost. The plastic BSF and

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the BF were manufactured in a Tshwane University of Technologyworkshop with some modifications from the designs available inliterature. The ‘‘Just Water’’ ceramic gravity filter (CCF) was do-nated by Headstream Water Holdings SA (Pty) (Ltd.) (Reg No.2008/01 5564/0)7 and the SIPP filter is a product of the TUT WaterResearch Group. Fig. 1 illustrates the schematic diagrams of thefour filters used during the study period. Prior to use, all the buck-ets, sand, gravel and zeolites used for the construction of filterunits were washed thoroughly using tap water and rinsed severaltimes with distilled water, and then placed in a laminar flow forsterilisation under UV light for 48 h.

2.1.1. Biosand filterThe biosand filter was made from a 25 l bucket, 41 cm high,

gravel (particle size: 5–7 mm), sand (particle size: 0.95 mm and0.3 mm) and zeolites (particle size: 3 mm). A 20 mm hole-sawwas used to open a hole in the middle of the bucket that was tobe packed with the filter media. A thread tape was wound aroundthe tap. The tap was then placed in the drilled hole. Two elbowswere used; one connected the tap to the pipe that was parallel tothe edge of the bucket. This pipe was connected to the other, usingthe second elbow. This pipe was parallel to the base of the bucket.Foam was put into this pipe to prevent the media from movingthrough the pipe (Fig. 1A). The gravel, sand, and zeolites were thenpacked in layers. The first layer from the bottom was the gravel,followed by the second layer of sand particles (0.95 mm). Each ofthese layers was packed up to 5 cm. The third layer of zeolites(3 mm) was 2.5 cm thick. The last layer consisted of the very finesand (0.3 mm) and was 2.5 cm thick. The biosand filter was con-structed following the guidelines of CAWST.org and Biosand fil-ter.org, with slight modifications. Conventional slow sand filtersusually have three layers of filter media. The zeolites formed the

fourth layer in the BSF for this study. Natural zeolites have beenshown to have high removal efficiency of chemical contaminantsand indicator bacteria in waste water (Widiastuti et al., 2008;Misaelides, 2011). Zeolites are readily available in South Africaand are inexpensive and may therefore be affordable to rural com-munities. A plastic drum ranging between 90 and 250 l is normallyused for the BSF construction. In this project, a 25 l plastic bucketwas used to ensure that the filter could occupy a small space inthe kitchen and is easily transported if necessary. Prior to use,the filter unit was again cleaned by flushing with water until theturbidity of the filtered water was lower than 1 NTU aftermeasurement.

2.1.2. Development of the biological layerThe biological layer was developed by filtering 20 l of surface

water which was obtained from the Daspoort Wastewater Treat-ment Plant located in Pretoria, South Africa. The water was filtereduntil it reached the 5 cm mark above the sand bed layer. The bio-logical layer was allowed to develop over a week. The water wastested for bacteria, protozoa and viruses prior to filtering, usingstandard methods (APHA, 2001).

2.1.3. Protection of biological layerA diffuser plate was made to help reduce disturbance of the top

layer and damage to the biological plate. The plate achieves this bydistributing the fall of the water over the whole filter surface. Forthis study, the diffusion plate was made from the plastic lid of a25 l bucket. The edge of this lid was cut off to ensure that the platefits tightly against the inner wall of the filer so that it would be se-cure. Perforations (2 mm) were drilled into the plate 1.5 cm apartin a circular pattern. The plate rests on three PVC tubes that areembedded into the top layer of sand, above the resting water level.

Fig. 1. Schematic diagrams of BSF (A), BF (B), CCF (C) and SIPP filter (D).

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2.2. Bucket filter

The BF system consisted of two 25 l buckets. The filter unit wasprepared by drilling small holes in the bottom of one of the bucket.This bucket was filled with a 2 cm layer of gravel (5–7 mm) and a5 cm layer of fine sand (0.3 mm) which served as the filter (Fig. 1B).It was suspended above the second bucket into which the filteredwater drained. To ensure that the lid remained intact with the bot-tom, PVC glue was used. The tap in this system was placed in thebottom bucket, which served as the collecting water container.Prior to use, the filter unit was again cleaned by flushing withwater until the turbidity of the filtered water was lower than 1NTU after measurement.

2.3. Ceramic candle filter

The CCF consisted of a dome-shaped candle filter, a spigot, twobuckets (one for filtration and one for collection of filtrate) and acloth that covered the candle to reduce contamination. The twobuckets were stacked on top of each other; a hole was drilled fromthe base of the top bucket through the lid of the bottom bucket(Fig. 1C). The dome-shaped candle was fitted in the top bucketand screwed to the lid of the bottom bucket. The spigot was placedin the bottom bucket. This is where water is drawn for consump-tion. Water poured into the top bucket with the pot filter perco-lates through the pot material, and is collected in a secondcontainer (the bottom bucket). Pathogens and suspended materialare removed from the water through a combination of biologicaland physical processes.

2.4. Silver-impregnated porous pot filter

The SIPP filter is a TUT Water Research Group product, madefrom brownish clay and impregnated with silver nitrate prior tofiring (Fig. 1D). This causes it to be different from other docu-mented silver-impregnated colloidal silver pots that are coatedwith silver after firing the clay pot.

2.5. Flow rate analysis

2.5.1. Flow measurementThe flow rate was measured by recording the volume of filtered

water that was collected at intervals of 1 h. This was done for fiveconsecutive hours and the volumes were recorded. The flow mea-surement was repeated three times over 3 days for the silver-impregnated pot filter (SIPP) and the ceramic candle filter (CCF).On day one, 10 l of water was passed through the filters and notreplenished. On days two and three the filters were constantlyreplenished (that is, the filters were always filled to the maximumvolume they are able to contain).

To determine the flow rate of the bucket filter and the biosandfilter, a beaker was placed under the filter spigot to allow water todrip into the beaker for a specified time (1 min). The volume ofwater collected in the beaker was compared to the time it tookfor the water to be filtered. The flow rate was then calculated asfollows:

Flow rate per hour ¼ volume filter=elapsed time ð1Þ

2.6. Test water sources and analysis of contaminants

Synthetic and environmental samples were used to evaluate theperformance of each filter unit in removing or reducing thechemical and bacterial contaminants. The water quality variablesused to measure the environmental health risk during this studywere the SANS 241 (2006) and the South African Water Quality

Guidelines (DWAF, 1996). For each type of test water, the experi-mental study was repeated three times.

2.6.1. Synthetic water samplesStock solutions of each contaminant of interest were prepared

using standard methods. Calculations were made prior to spikingeach contaminant into the water to ensure that the required con-centrations were obtained. For each filter unit, 20 l of sterile deion-ised water was spiked with the chemical and microbialcontaminants of interest. Table 1 illustrates various chemical con-taminants spiked into sterile deionised water samples. A calibra-tion curve for each chemical contaminant was drawn as logconcentrations versus potential differences from standards. Theconcentrations of the chemical contaminants were then deter-mined before and after passing through the filter units using thestandard methods (APHA, 2001).

Pathogenic S. typhimurium (ATCC 14028) and E. coli O157:H7(ATCC 43895) were obtained from the American Type Culture Col-lection (Rockville, MD. T) and V. cholerae and S. dysenteriae fromthe Council for Scientific and Industrial Research (CSIR, Pretoria)bacterial stock cultures. These strains were confirmed by culturaltests according to standard methods, using selective media (APHA,2001).

To obtain the initial concentrations that were spiked into thedeionised water samples, one loop of each enteric pathogenic bac-terium was grown in Nutrient Broth (Merck, South Africa) in a100 ml Erlenmeyer flask. The flasks were incubated in a shakingincubator at 37 ± 1 �C for 5 ± 1 h and at 100 ± 10 rpm (ScientificModel 353, Lasec South Africa). The concentrations were deter-mined by using the spread plate technique, after samples had beenserially diluted in 9 ml of sterile 0.9% w/v NaCl. The plates wereincubated at 37 �C for 24 h. The resulting colonies were countedto express the bacterial concentrations as CFU/ml. Aliquots of over-night culture corresponding to 105 CFU/ml of each test bacteriawere inoculated into 20 l final volumes of sterile deionised water.The spiked water samples were shaken vigorously several timesbefore passing 10 ml through each filter unit. The concentrationsof bacteria before and after filtration were quantified by the mem-brane filtration method, using selective agar plates, as described inthe standard methods (APHA, 2001).

2.6.2. Environmental water samplesSurface water samples were obtained from the Wallmansthal

Waterworks, which are under the management of the MagaliesWater Board, Pretoria, South Africa. Samples were collected fromthe point of abstraction in clean and 50 l sterile plastic barrels.Prior to use, these containers were placed under a laminar flowcabinet fitted with an ultraviolet irradiation system. The concen-trations of fluoride, iron, arsenic, magnesium, calcium, nitrate,phosphate, chlorophyll a and the level of turbidity in the watersamples were determined using standard methods (APHA, 2001).Samples were also analysed for pathogenic E. coli spp., Salmonellaspp., Shigella spp. and Vibrio spp., using standard methods andselective media (APHA, 2001). Five purified colonies of the pre-

Table 1Chemical contaminants dissolved in 20 l of deionised water.

Chemicalcontaminants

Quantity and type of chemicalused (g)

Requiredconcentration (g/l)

Magnesium 122.7 g MgCl2 0.4 g/lCalcium 7.484 g CaCO3 0.006 g/lIron 0.115 g Fe2O3 0.0001 g/lPhosphate 3.281 g KH2PO 4 0.08 g/lNitrate 53.712 g KNO3 1.0 g/lFluoride 0.977 g NaF 0.01 g/l

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sumed E. coli, Salmonella, Shigella and Vibrio spp. were randomly se-lected and subjected to biochemical tests and the API 20 E kit foridentification.

3. Results and discussion

3.1. Flow rate analysis

The average flow rates obtained for each filter unit during thestudy period were within the recommended limits (171 l/h,167 l/h, 6.4 l/h and 3.5 l/h for the BSF, BF, CCF and SIPP, respec-tively). For a good performance by the filters, Brown and Sobsey(2006) recommend flow rates ranging between 1 and 11 l/h forCCF, while CAWST (2008) recommends a flow rate of 150 l/h forBSF. Silver-incorporated porous pots normally have flow ratesranging between 1 and 3 l/h (Van Halem et al., 2009).

3.2. Removal of chemical contaminants

Using standard methods, the results of the preliminary studieswith spiked (Tables 1 and 2, Figs. 2 and 3) and environmental

water (Table 2) samples indicated that all filters decreased the con-centrations of the chemical contaminants in the test water sources,although there were variations in the removal efficiency, whichalso related to the type of test water source and to the filter unit.The most efficiently removed chemical contaminant in spikedwater was fluoride (99.9%) and this was noted in all the filter sys-tems. The poorest removal efficiency was observed for magnesium(26–56%) (Fig. 2 or Table 2). After the filtration of synthetic water,the removal of calcium was found to be most efficient in the BSF(90.6%). The removal of high calcium concentrations is important,as calcium contributes to hardness of water and has a significantimpact on physiological activities involving bone formation, nerveintegrity as well as transformation (Galvin, 1996; Hoko, 2008). TheCCF achieved the highest percentage reduction of iron (95.2%) ofthe four filters. The CCF evaluated in this study had a carbon fibreblanket with pore size of 0.2 lm and the ceramic component of thefilter was 0.5 lm. Activated carbon filters have been found byModin et al. (2011) to be effective in removing more than 90% ofiron, which is similar to the results obtained in this study. Of thefour filters, the SIPP achieved the highest percentage arsenic reduc-tion (97.4%). This finding supports the hypothesis that clay miner-als adsorb cationic, anionic and neutral metal species (Mohan and

Fig. 2. Chemical contaminant removal efficiencies from synthetic water.

Table 2Concentrations of chemical contaminants in the synthetic water sample before and after filtration.

Chemical/parameter Filter name Before filtration (mg/l) After filtration (mg/l) % Removal SANS 241 (2006) limit (mg/l)

Fluorides CCF 100.0 <1.00 99.9 <1BF 100.0 <1.00 99.9 <1SIPP 100.0 <1.00 99.9 <1BSF 100.0 <1.00 99.9 <1

Calcium CCF 49.57 10.99 77.8 <150BF 49.57 14.13 71.5 <150SIPP 49.57 10.30 79.2 <150BSF 49.57 2.97 90.6 <150

Iron CCF 0.03 <0.01 95.2 <0.2BF 0.03 <0.01 75.3 <0.2SIPP 0.03 <0.01 54.9 <0.2BSF 0.03 <0.01 64.2 <0.2

Magnesium CCF 414.38 305.95 26.6 <70BF 414.38 179.14 56.8 <70SIPP 414.38 250.08 39.6 <70BSF 414.38 237.03 57.2 <70

Nitrates CCF 970 155 84.0 <10BF 970 51 94.7 <10SIPP 970 600 38.1 <10BSF 970 789.58 18.6 <10

Phosphates CCF 75.10 53.15 24.0 Not availableBF 75.10 34.05 51.3 Not availableSIPP 75.10 21.10 69.8 Not availableBSF 75.10 45.59 39.3 Not available

Arsenic CCF 10.27 6.59 35.8 <10BF 10.27 7.41 27.9 <10SIPP 10.27 0.27 97.4 <10BSF 10.27 3.12 68.9 <10

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Pittman, 2007). Clays such as kaolinite, illite and montmorillonitehave been found to remove arsenic from contaminated water (Pra-sad, 1994; Manning and Goldberg, 1997a,b). Achak et al. (2009) re-ported 81–99% nitrate reduction by sand filters and proposed thattotal nitrate removal was through anaerobic denitrifying microor-ganisms when the filter was supplied by water. This finding is sim-ilar to the results of this study that show (Table 3) that the mostefficient removal of nitrates was achieved by the BF (94.7%) andalso explain the process by which the BF removes nitrates.

Although the concentrations of most chemical parameters inraw surface water were within the limits set in the national guide-lines (DWAF, 1996; SANS 241, 2006), poor removal efficiencieswere recorded for all filters, with the poorest reduction noted withfluoride (16–48%). No iron and arsenic were detected in surfacewater samples. Higher performance in the removal of chlorophylla was especially noted with the BF (97.8%), followed by the CCF

unit (91.1%) (Table 3 or Fig. 3). Overall, the outcomes of this partof the study revealed that higher removal efficiencies of chemicalcontaminants were observed in synthetic water samples comparedto environmental water samples. This could be due to the fact thatno other parameters in synthetic water samples interfered withthe chemical compounds spiked in deionised water. In contrastto the environmental water samples, the chemical compounds ofinterest could be surrounded by other contaminants that mightinterfere in the treatment of this type of source water. Neverthe-less, the SIPP filter, for example, removed 72% of nitrates in surfacewater, but was only able to remove 16% of fluorides from the samewater sample (Table 3, Fig. 3). Magnesium was also poorly re-moved by three filters (<50% removal), but the biosand filter wasable to remove 57% Mg from the environmental water. This meansthat different filters could be selected by the homeowners for theremoval of different or specific contaminants of interest.

Fig. 3. Chemical contaminant removal efficiencies from surface high-turbidity water.

Table 3Concentrations of chemical contaminants in the surface water sample before and after filtration.

Chemical name Filter name Before filtration (mg/l) After filtration (mg/l) % Removal SANS 241 (2006) limit (mg/l)

Fluorides BSF 0.32 0.24 25.7 <1BF 0.32 0.17 46.7 <1CCF 0.32 0.23 28.0 <1SIPP 0.32 0.27 16.7 <1

Iron CCF ND ND N/A <0.2SIPP ND ND N/A <0.2BF ND ND N/A <0.2BSF ND ND N/A <0.2

Magnesium CCF 10.61 10.32 2.7 <70SIPP 10.61 6.24 41.2 <70BF 10.61 7.47 29.6 <70BSF 10.61 4.57 56.9 <70

Calcium CCF 382.6 233.2 39.0 <150SIPP 382.6 264.1 35.7 <150BF 382.6 382.6 100 <150BSF 382.6 258.5 32.4 <150

Arsenic CCF ND ND N/A <10SIPP ND ND N/A <10BF ND ND N/A <10BSF ND ND N/A <10

Nitrates SIPP 1.00 0.28 72.0 <10CCF 1.00 0.94 6.0 <10BF 1.00 0.36 64.0 <10BSF 1.00 0.76 24.0 <10

Phosphates CCF 7.64 5.30 30.6 Not availableBSF 7.64 2.58 66.2 Not availableBF 7.64 4.26 44.2 Not availableSIPP 7.64 2.82 63.1 Not available

Chlorophyll a CCF 72.1 6.4 91.1 Not availableSIPP 72.1 40.1 44.4 Not availableBF 72.1 1.6 97.8 Not availableBSF 72.1 27.2 62.2 Not available

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3.3. Turbidity reduction

Table 4 summarises the average levels of turbidity in surfacewater samples before and after treatment and also the perfor-mance of each filter unit. Although, the levels of turbidity in fil-tered water exceeded the recommended limit (which is <1 NTU)(DWAF, 1996; SANS 241, 2006), the removal efficiency of the fourfilter units was at P90%. The highest turbidity removal perfor-mance of 95% was noted with the CCF, followed by the SIPP filter(94%). Turbidity is caused by the presence of suspended matter,which usually consists of a mixture of inorganic matter, such asclay and soil particles, and organic matter. The latter can includeboth living matter (such as microorganisms) and non-living matter(DWAF, 1996). High turbidity in filtered water is therefore a matterof concern, as this indicates the presence of suspended organicmaterial, which promotes the growth of microorganisms, espe-cially during the storage of drinking water at the dwelling (Mombaand Notshe, 2003). Drinking-water turbidity, a measure of thecloudiness of the water, is commonly used as a proxy measurefor the risk of microbial contamination and the effectiveness ofthe treatment of public drinking water (EPA, 1984). Several studieshave shown a correlation between turbidity levels and microbialcontamination of raw and treated water (LeChevallier et al.,1991; Clark et al., 1992; LeChevallier and Norton, 1993) and afew documented waterborne disease outbreaks were associatedwith increased turbidity levels (Mackenzie et al., 1994; Schwartzet al., 2000).

3.4. Removal of bacterial contaminants

As indicated in Table 5, all four filter systems were able to de-crease the concentrations of pathogenic bacteria in spiked andenvironmental water samples. However, this bacterial reductionwas characterised by variations in the performance of the four fil-ters and depended on the target organisms (Tables 5 and 6). Withthe exception of the SIPP filter, which effectively removed V. chol-erae at 100% from spiked water, the log reduction of pathogenicbacteria ranged between 1.7 and 3.5logs for all the filter units (Ta-ble 6). Removals of bacteria by the biosand filter (BSF) have beenreported to range between 1 and 3log reductions (Sobsey et al.,

2008). The results obtained from spiked water (Tables 5 and 6)supported those obtained by Sobsey and co-workers (2008), asthe BSF removed P2log each test bacteria. The percentage removalof pathogenic bacteria by the BSF ranged between 98% and 100%,which was within the removal rates of 81–100% stated by previousinvestigators (Kaiser et al., 2002; Stauber et al., 2006; Baumgartneret al., 2007).

Compared to spiked water samples, raw surface water sampleshad lower concentrations of target potential pathogenic bacteria(Tables 7 and 8). Nevertheless, presumptive E. coli (960 CFU/100 ml) was found to be present at the highest concentrationand Vibrio spp. (4 CFU/100 ml) at the lowest concentration, com-pared to other presumptive target bacteria present in the surfacewater source (Table 7).

The SIPP filter unit removed presumptive Vibrio spp. (3log CFU/100 ml), Salmonella spp. (3log CFU/100 ml) and presumptive Shi-gella spp. (2log CFU/100 ml) at 100% and presumptive E. coli at99% (2.5log CFU/100 ml) from surface water (Table 8). These re-sults are similar to data published by other investigators, whichhave shown reductions of E. coli by ceramic silver pot filters torange between 2 and 7logs (Lantagne, 2001; Campbell, 2005;Van Halem, 2006). Findings reported by Clasen and Boisson(2006) have shown ceramic candle filters to be bacteriologicallyeffective by removing faecal bacteria at a rate up to 99.99% (4 logCFU/100 ml).

The CCF system also removed presumptive Vibrio spp. at a sim-ilar rate (100%) as the SIPP filter unit, while the BSF, BF and CCFunits showed a similar performance of 93% for the removal of pre-sumptive Shigella spp. from the surface water source (Table 8).However, both the BF and BSF units exhibited extremely poor

Table 4Turbidity removal efficiency in environmental surface water.

Filters Turbidity beforefiltration (NTU)

Turbidity afterfiltration (NTU)

Percentageremoval (%)

BSF 89.19 5.75 93.6BF 89.19 8.89 90CCF 89.19 4.45 95SIPP 89.19 5.26 94

Table 5Concentrations of bacterial contaminants in the synthetic water sample before andafter filtration.

Filter E. coli 0157:H7 V. cholerae S. typhimurium S. dystenteriae

Bacterial concentrations (CFU/100 ml) before filtrationBSF 1.89 � 105 2.23 � 105 1.27 � 105 1.25 � 105

BF 2.92 � 105 1.78 � 105 2.15 � 105 1.84 � 105

CCF 1.40 � 105 1.82 � 105 1.68 � 105 1.54 � 105

SIPP 1.20 � 105 1.92 � 105 1.70 � 105 1.66 � 105

Bacterial concentrations (CFU/100 ml) after filtrationBSF 1.86 � 103 2.21 � 103 1.26 � 103 3.00 � 102

BF 2.83 � 103 2.61 � 103 2.11 � 103 3.80 � 103

CCF 4.75 � 102 2.10 � 103 1.65 � 103 1.04 � 102

SIPP 1.19 � 102 0 1.67 � 102 5.80 � 101

Table 6Log10 bacterial reduction and percentage bacterial removal after filtration of spikedwater samples.

Filter E. coli 0157:H7 V. cholerae S. typhimurium S. dystenteriae

Log reduction (% removal) of bacteriaBSF 2.0 (98) 2.0 (99) 2.0 (98) 2.6 (99)BF 2.0 (97) 1.8 (98) 2.0 (98) 1.7 (99)CCF 2.5 (98) 2.0 (99) 2.0 (98) 3.2 (99)SIPP 3.0 (99) 5 (100) 3.0 (99) 3.5 (99)

Table 7Bacterial concentration of surface water (89.2 NTU) before and after filtration.

PresumptiveE. coli

PresumptiveVibrio spp.

PresumptiveSalmonella spp.

PresumptiveShigella spp.

Bacterial concentrations (CFU/100 ml) before filtration960 5 780 230

Bacterial concentrations (CFU/100 ml) of surface water (89.19 NTU) afterfiltration

BSF 440 4 313 17BF 550 4 440 15CCF 136 0 109 14SIPP 3 0 0 0

Table 8Log reduction and percentage removal of bacteria from surface water samples.

Filters PresumptiveE. coli

PresumptiveVibrio spp.

PresumptiveSalmonella spp.

PresumptiveShigella spp.

Log reduction (% removal) of bacteria from high-turbidity surface waterBSF 0.34 (54) 0.10 (20) 0.40 (60) 1.10 (93)BF 0.24 (43) 0.10 (20) 0.25 (44) 1.20 (93)CCF 0.85 (85) 0.70 (100) 0.85 (86) 1.22 (93)SIPP 2.50 (99) 0.70 (100) 2.89 (100) 2.36 (100)

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reductions of Vibrio spp. from this water source (Tables 8). Overall,with the exception of the SIPP filter unit that produced drinkingwater of a high quality, results obtained after filtration of surfacewater by other filter units showed lower log reductions (whichranged between 0.10 and 1.22; Table 8) than those stated by pre-vious investigators (Sobsey et al., 2008). The log reduction of 2.5for E. coli concurred with those found in most studies (log reduc-tion ranging between 2 and 3) for silver-impregnated pot filters(Duke et al., 2006; Fahlin, 2003; Campbell, 2005). The high removalefficiency of this filter unit can be attributed to the silver coatedonto the pot before firing. Silver is known to have bactericidalproperties and has a history of being used as a disinfectant (Lanta-gne, 2001; Oyanedel-Craver and Smit, 2008; Nagarajan andJaiprakashnarain, 2009). Despite the improvement of drinkingwater quality when using BSF, BF and CCF, there is still a needfor the disinfection of the filtered water.

4. Conclusion and recommendations

The outcomes of this preliminary investigation showed that allfilters decreased the concentrations of chemical and microbial con-taminants from test water sources. Higher removal efficiencies ofchemical contaminants were observed in synthetic water com-pared to the environmental water sources. Although the CCF wasmore effective in reducing turbidity, at a rate up to 95%, none ofthe four filters achieved the limits set by the SANS 24 (<1 NTU).Compared to other filter units, the SIPP filter was found to be moreeffective in removing nitrate from the environmental water. The BFunit was found to be the most effective filter in removing thechemical contaminants from both synthetic and environmentalwater. This filter showed the poorest performance in bacterial re-moval and the SIPP filter unit was found to be the most effectivefilter for producing bacteriologically safe drinking water. Furtherstudies are currently being conducted to determine the patternsin chemical and bacterial contaminant removal efficiency of eachfilter with short-term and long-term use. The relationship betweenthe flow rate and turbidity when removing bacteria is also underinvestigation. Extensive experimental studies with various typesof water sources will therefore determine the long-term perfor-mance of each filter and the best filter will be recommended tothe communities for the household treatment of drinking water.

Acknowledgement

Our appreciation is expressed to the Water Research Commis-sion of South Africa for funding this research.

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