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Household water treatment systems: A solution to the production of safe

drinking 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:

Household

Treatment

Systems

Safe drinking water

Filters

Water-borne disease

a b s t r a c t

Oneof the United Nations Millennium Development Goals is to reduce to half by 2015 thenumber of peo-

ple, worldwide, wholack access to safe water. Dueto the numerous deaths andillnesses causedby water-

borne pathogens, various household water treatment devices and safe storage technologies have been

developed to treat and manage water at the household level. The new approaches that are continually

being 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 household

treatment 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 three

filters were manufactured in a Tshwane University of Technology workshop, using modified designs

reported in literature. The SIPP filter is a product of the Tshwane University of Technology. The perfor-

manceof the four filters was evaluated in terms of flowrate, 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 rates

obtained during the study 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, respectively). Using standard methods, the results of the preliminary

laboratory and field studies with spiked and environmental water samples indicated that all filters

decreased 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 for

magnesium (2656%). A higher performance in chemical contaminant removal was noted with the BF.

For pathogenic bacteria, themean percentage removals rangedbetween 97%and 100%. Although the con-

centrations of most chemical parameters were within therecommended limits in rawsurface water, poor

removal 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 (99100%) and the lowest by the BF

(2045%) and the BSF (2060%). Extensive experimental studies with various types of raw surface water

will 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.

2011 Elsevier Ltd. All rights reserved.

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 still

do not have access to safe potable water. A large percentage of

these people are from the developing world, especially in the rural

areas and low-income communities (WHO/UNICEF, 2006; WHO,

2007). Small communities face the greatest difficulty in receiving

water 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 inadequate

management as well as violations of drinking water standards

are 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).

Physics and Chemistry of the Earth 36 (2011) 11201128

Contents lists available at SciVerse ScienceDirect

Physics and Chemistry of the Earth

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / p c e

http://dx.doi.org/10.1016/j.pce.2011.07.078mailto:mombamnb@tut.ac.zahttp://dx.doi.org/10.1016/j.pce.2011.07.078http://www.sciencedirect.com/science/journal/14747065http://www.elsevier.com/locate/pcehttp://www.elsevier.com/locate/pcehttp://www.sciencedirect.com/science/journal/14747065http://dx.doi.org/10.1016/j.pce.2011.07.078mailto:mombamnb@tut.ac.zahttp://dx.doi.org/10.1016/j.pce.2011.07.078

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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 various

waterborne infectious diseases affecting numerous communities,

particularly those in rural and indigenous areas (Venter, 2000;

Murcott, 2006; Momba, 2009) and consequently an estimated

five million people lose their lives due to water-related disease

each 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 and

human enteritis (Okoh et al., 2007; Leonard et al., 2003; Venter,

2000). The most common cause of illness and deaths in the

developing world is a watery diarrhoea called cholera (Clasen

et al., 2006) caused by a bacterial pathogen classified as Vibrio

cholerae (Shultz et al., 2009).

Between August 2008 and January 2009 there was an outbreak

of cholera in Southern Africa. The cases of cholera reported in Zim-

babwe, Mozambique, Zambia and South Africa were estimated at

353300, 10006, 1759 and 1608, respectively (OCHA, 2009). It has

been well documented that immunocompromised people, babies

and the elderly are the most susceptible to bacterial infections

and it is therefore crucial that these people have access to good

quality water on a daily basis (Momba et al., 2008).

Drinking water contains not only microbial contaminants, but

also chemical contaminants that range from organic to inorganic

compounds. Examples of organic chemicals that can be toxic are

the polychlorinated and polybrominated biphenyls (PCBs and

PBBs) as well as benzenes. Symptoms of acute toxicity can include

diarrhoea, nausea, convulsions, blurred vision, and difficulty in

breathing. Organic pollutants may also cause arteriosclerosis, heart

diseases, hypertension, emphysema, bronchitis, and kidney and li-

ver dysfunction (Leivadara et al., 2008). Inorganic chemicals are

also associated with health problems once they enter the human

system. 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 such

as 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 to

improve the quality and safety of water for drinking in situations

where there is no safe centrally treated water supply or where

the treated water supply system has been compromised. The most

appropriate technology will depend on the situation, the quality of

the 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 the

availability of personnel to provide the necessary training and

monitoring for the technology to be successfully implemented.There is a growing body of literature on household water

treatment and safe storage (HWTSS). Recent studies have shown

that simple and relatively inexpensive home water treatment

and storage methods can result in substantial improvements in

the microbial quality of drinking water and reduced risks of

illness and death, even in the absence of improved sanitation

(Sobsey, 2002; Murcott, 2006; Stauber et al., 2006; Clasen and

Boisson, 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 and

iodine), filtration, distillation, reverse osmosis, solar disinfectant

and water purifiers, have been reported to decrease endemic diar-

rhoea caused by waterborne pathogens and to improve the

microbial and chemical quality of drinking water (Sobsey, 2002;Stauber et al., 2006; Murcott, 2006).

In this study, we evaluate the performance of four household

water 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 porous

pot filter (SIPP). The biosand filter developed by Dr. Manz of the

University of Calgary in the early 1990s (Legge, 1996; Samaritans

Purse, 2001) is a modification of slow sand filtration technology

and has been reported to be effective in removing microorganisms

such 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 of

microorganisms to produce safe water (Earwaker, 2006). The most

important process in the BSF occurs in a biological layer called the

Shmutzdecke, which develops on the surface of the uppermost

layer of sand that is responsible for the removal of microorganisms

(AWWA, 1991). The bucket filter is a rapid sand filter that consists

of one thick layer of fine sandand a thinner layer of gravel (Sobsey,

2002). Rapid sand filtration (filtration rate of 520 m/h) is typically

efficient for the removal of large pathogens such as Giardia cysts,

Cryptosporidium cysts, helminths and 5090% of bacteria (Sobsey,

2002). The candle filter consists of one or more candle-shaped

ceramic filters with two chambers (Nath et al., 2006) and has been

reported 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 that

is usually mixed with materials such as sawdust or wheat flour to

improve porosity (Dies, 2003 andVan Halem, 2006). They have

microscale pores that are effective in removing bacteria from water

(Clasen and Boisson, 2006). The pore sizes of ceramic filters are

usually 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 in

a receptacle. Rawwater is poured into the pot and is slowly filtered

into the receptacle through pores in the ceramic element. This pot

is 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 a

mixture of colloidal silver and water for disinfection purposes. A

well-known and widely used CSF is the Potter for peace, which con-

tains 7 l of water and has the capacity to produce 13 l of water per

hour (Lantagne, 2001).

Although various systems and devices have been extensively re-

ported in the literature, little is known locally about the existing

options and how to assist local communities in making informed

choices on whether a particular system or unit will be appropriate

to 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 provide

some guidance on both the selection and use of these units under

local conditions. This preliminary study reports on the perfor-

mance of the four filters in terms of flow rate, physicochemical

contaminants (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 Technology

workshop with some modifications from the designs available in

literature. 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 Water

Research Group. Fig. 1 illustrates the schematic diagrams of the

four filters used during the study period. Prior to use, all the buck-

ets, sand, gravel and zeolites used for the construction of filter

units were washed thoroughly using tap water and rinsed several

times with distilled water, and then placed in a laminar flow for

sterilisation under UV light for 48 h.

2.1.1. Biosand filter

The biosand filter was made from a 25 l bucket, 41 cm high,

gravel (particle size: 57 mm), sand (particle size: 0.95 mm and

0.3 mm) and zeolites (particle size: 3 mm). A 20 mm hole-saw

was used to open a hole in the middle of the bucket that was to

be packed with the filter media. A thread tape was wound around

the tap. The tap was then placed in the drilled hole. Two elbows

were used; one connected the tap to the pipe that was parallel to

the edge of the bucket. This pipe was connected to the other, using

the second elbow. This pipe was parallel to the base of the bucket.

Foam was put into this pipe to prevent the media from moving

through the pipe (Fig. 1A). The gravel, sand, and zeolites were then

packed in layers. The first layer from the bottom was the gravel,

followed by the second layer of sand particles (0.95 mm). Each of

these 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 fine

sand (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 filters

usually have three layers of filter media. The zeolites formed the

fourth layer in the BSF for this study. Natural zeolites have been

shown to have high removal efficiency of chemical contaminants

and indicator bacteria in waste water (Widiastuti et al., 2008;

Misaelides, 2011). Zeolites are readily available in South Africa

and are inexpensive and may therefore be affordable to rural com-

munities. A plastic drum ranging between 90 and 250 l is normally

used for the BSF construction. In this project, a 25 l plastic bucket

was used to ensure that the filter could occupy a small space in

the kitchen and is easily transported if necessary. Prior to use,

the filter unit was again cleaned by flushing with water until the

turbidity of the filtered water was lower than 1 NTU after

measurement.

2.1.2. Development of the biological layer

The 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 filtered

until it reached the 5 cm mark above the sand bed layer. The bio-

logical layer was allowed to develop over a week. The water was

tested for bacteria, protozoa and viruses prior to filtering, using

standard methods (APHA, 2001).

2.1.3. Protection of biological layer

A diffuser plate was made to help reduce disturbance of the top

layer and damage to the biological plate.The plate achieves this by

distributing the fall of the water over the whole filter surface. For

this study, the diffusion plate was made from the plastic lid of a

25 l bucket. The edge of this lid was cut off to ensure that the plate

fits 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 apart

in a circular pattern. The plate rests on three PVC tubes that are

embedded 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 was

prepared by drilling small holes in the bottom of one of the bucket.

This bucket was filled with a 2 cm layer of gravel (57 mm) and a

5 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 filtered

water drained. To ensure that the lid remained intact with the bot-

tom, PVC glue was used. The tap in this system was placed in the

bottom bucket, which served as the collecting water container.

Prior to use, the filter unit was again cleaned by flushing with

water until the turbidity of the filtered water was lower than 1

NTU after measurement.

2.3. Ceramic candle filter

The CCF consisted of a dome-shaped candle filter, a spigot, two

buckets (one for filtration and one for collection of filtrate) and a

cloth that covered the candle to reduce contamination. The two

buckets were stacked on top of each other; a hole was drilled from

the base of the top bucket through the lid of the bottom bucket

(Fig. 1C). The dome-shaped candle was fitted in the top bucket

and screwed to the lid of the bottom bucket. The spigot was placed

in 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 second

container (the bottom bucket). Pathogens and suspended material

are removed from the water through a combination of biological

and physical processes.

2.4. Silver-impregnated porous pot filter

The SIPP filter is a TUT Water Research Group product, made

from brownish clay and impregnated with silver nitrate prior to

firing (Fig. 1D). This causes it to be different from other docu-

mented silver-impregnated colloidal silver pots that are coated

with silver after firing the clay pot.

2.5. Flow rate analysis

2.5.1. Flow measurement

The flow rate was measured by recording the volume of filtered

water that was collected at intervals of 1 h. This was done for five

consecutive 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 not

replenished. On days two and three the filters were constantly

replenished (that is, the filters were always filled to the maximum

volume 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 to

drip into the beaker for a specified time (1 min). The volume of

water collected in the beaker was compared to the time it took

for the water to be filtered. The flow rate was then calculated as

follows:

Flow rate per hour volume filter=elapsed time 1

2.6. Test water sources and analysis of contaminants

Synthetic and environmental samples were used to evaluate the

performance of each filter unit in removing or reducing the

chemical and bacterial contaminants. The water quality variables

used 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 samples

Stock solutions of each contaminant of interest were prepared

using standard methods. Calculations were made prior to spiking

each 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 microbial

contaminants of interest.Table 1illustrates various chemical con-

taminants spiked into sterile deionised water samples. A calibra-

tion curve for each chemical contaminant was drawn as log

concentrations versus potential differences from standards. The

concentrations of the chemical contaminants were then deter-

mined before and after passing through the filter units using the

standard 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 from

the Council for Scientific and Industrial Research (CSIR, Pretoria)

bacterial stock cultures. These strains were confirmed by cultural

tests according to standard methods, using selective media (APHA,2001).

To obtain the initial concentrations that were spiked into the

deionised water samples, one loop of each enteric pathogenic bac-

terium was grown in Nutrient Broth (Merck, South Africa) in a

100 ml Erlenmeyer flask. The flasks were incubated in a shaking

incubator at 37 1 C for 5 1 h and at 100 10 rpm (Scientific

Model 353, Lasec South Africa). The concentrations were deter-

mined by using the spread plate technique, after samples had been

serially diluted in 9 ml of sterile 0.9% w/v NaCl. The plates were

incubated at 37 C for 24 h. The resulting colonies were counted

to express the bacterial concentrations as CFU/ml. Aliquots of over-

night culture corresponding to 105 CFU/ml of each test bacteria

were inoculated into 20 l final volumes of sterile deionised water.

The spiked water samples were shaken vigorously several times

before passing 10 ml through each filter unit. The concentrations

of bacteria before and after filtration were quantified by the mem-

brane filtration method, using selective agar plates, as described in

the standard methods (APHA, 2001).

2.6.2. Environmental water samples

Surface water samples were obtained from the Wallmansthal

Waterworks, which are under the management of the Magalies

Water Board, Pretoria, South Africa. Samples were collected from

the point of abstraction in clean and 50 l sterile plastic barrels.

Prior to use, these containers were placed under a laminar flow

cabinet 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 water

samples were determined using standard methods (APHA, 2001).

Samples were also analysed for pathogenic E. coli spp., Salmonella

spp., Shigella spp. and Vibrio spp., using standard methods and

selective media (APHA, 2001). Five purified colonies of the pre-

Table 1

Chemical contaminants dissolved in 20 l of deionised water.

Chemical

contaminants

Quantity and type of chemical

used (g)

Required

concentration (g/l)

Magnesium 122.7 g MgCl2 0.4 g/l

Calcium 7.484 g CaCO3 0.006 g/l

Iron 0.115 g Fe2O3 0.0001 g/l

Phosphate 3.281 g KH2PO 4 0.08 g/l

Nitrate 53.712 g KNO3 1.0 g/l

Fluoride 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 for

identification.

3. Results and discussion

3.1. Flow rate analysis

The average flow rates obtained for each filter unit during the

study 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 for

CCF, while CAWST (2008) recommends a flow rate of 150 l/h for

BSF. Silver-incorporated porous pots normally have flow rates

ranging 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 studies

with 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, which

also related to the type of test water source and to the filter unit.

The most efficiently removed chemical contaminant in spiked

water was fluoride (99.9%) and this was noted in all the filter sys-

tems. The poorest removal efficiency was observed for magnesium

(2656%) (Fig. 2orTable 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 significant

impact on physiological activities involving bone formation, nerve

integrity as well as transformation (Galvin, 1996; Hoko, 2008). The

CCF achieved the highest percentage reduction of iron (95.2%) of

the four filters. The CCF evaluated in this study had a carbon fibre

blanket with pore size of 0.2 lm and the ceramic component of the

filter was 0.5lm. Activated carbon filters have been found by

Modin et al. (2011) to be effective in removing more than 90% of

iron, which is similar to the results obtained in this study. Of the

four 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 2

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

Chemical/parameter Filter name Bef ore filtration (mg/l) Af ter filtration (mg/l) % Removal SANS 241 (2006)limit (mg/l)

Fluorides CCF 100.0

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Pittman, 2007). Clays such as kaolinite, illite and montmorillonite

have been found to remove arsenic from contaminated water (Pra-

sad, 1994; Manning and Goldberg, 1997a,b).Achak et al. (2009) re-

ported 8199% nitrate reduction by sand filters and proposed that

total 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 most

efficient 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 in

raw surface water were within the limits set in the national guide-

lines (DWAF, 1996; SANS 241, 2006), poor removal efficiencies

were recorded for all filters, with the poorest reduction noted with

fluoride (1648%). No iron and arsenic were detected in surface

water samples. Higher performance in the removal of chlorophyll

a was especially noted with the BF (97.8%), followed by the CCF

unit (91.1%) (Table 3or Fig. 3). Overall, the outcomes of this part

of the study revealed that higher removal efficiencies of chemical

contaminants were observed in synthetic water samples compared

to environmental water samples. This could be due to the fact that

no other parameters in synthetic water samples interfered with

the chemical compounds spiked in deionised water. In contrast

to the environmental water samples, the chemical compounds of

interest 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 surface

water, but was only able to remove 16% of fluorides from the same

water sample (Table 3, Fig. 3). Magnesium was also poorly re-

moved by three filters (

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3.3. Turbidity reduction

Table 4 summarises the average levels of turbidity in surface

water 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

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reductions ofVibriospp. from this water source (Tables 8). Overall,

with the exception of the SIPP filter unit that produced drinking

water of a high quality, results obtained after filtration of surface

water by other filter units showed lower log reductions (which

ranged between 0.10 and 1.22; Table 8) than those stated by pre-

vious investigators (Sobsey et al., 2008). The log reduction of 2.5

forE. 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 removal

efficiency of this filter unit can be attributed to the silver coated

onto the pot before firing. Silver is known to have bactericidal

properties and has a history of being used as a disinfectant (Lanta-

gne, 2001; Oyanedel-Craver and Smit, 2008; Nagarajan and

Jaiprakashnarain, 2009). Despite the improvement of drinking

water quality when using BSF, BF and CCF, there is still a need

for the disinfection of the filtered water.

4. Conclusion and recommendations

The outcomes of this preliminary investigation showed that all

filters decreased the concentrations of chemical and microbial con-

taminants from test water sources. Higher removal efficiencies of

chemical contaminants were observed in synthetic water com-

pared to the environmental water sources. Although the CCF was

more effective in reducing turbidity, at a rate up to 95%, none of

the four filters achieved the limits set by the SANS 24 (

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