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PHYSICO-CHEMICAL AND MICROBIOLOGICAL STUDIES OF DRINKING WATER FROM MAURITIUS


Anjelee Ragoobur, Minu Gupta Bhowon, and Sabina Jhaumeer Laulloo*
Department of Chemistry, Faculty of Science, University of Mauritius, Reduit, Mauritius

ABSTRACT

Access to safe drinking water is a fundamental requirement for good health and is also a human right. The monitoring of water supplies for the detection of faecal pollution is an important aspect for the detection of pathogenic bacteria, responsible for diseases such as gastroenteritis, cholera and bacillary dysentery thus representing serious health hazards. Most drinking water suppliers rely on faecal indicators, such as the well-established Escherichia coli (E. coli) or the total coliform enumeration. In the present study, the physico-chemical parameters (pH, turbidity and conductivity) and the enumeration of the micro-organisms, E. coli, total coliform and clostridium perfringens were carried out in raw, filtered and treated water samples over a period of five months (August–December 2014) at three different stations. Filtration of water caused a considerable decrease on turbidity (about 55%) except at Station 3, where the treated water was mixed with raw water coming from a borehole. After filtration and chlorination the water samples tested were found to be free from the indicator organisms (coliform organisms and presumptive E. coli). However, the presence of clostridium perfringens were detected and enumerated in chlorinated water samples (0–3 CFU) for the samples collected during drought season. Therefore, treatment of water samples with chlorine can eliminate the coliform bacteria, but the more resistant pathogens are not eliminated completely Hence, clostridium perfringens could be used as an additional bio-indicator to assess faecal pollution and to monitor the treatment of drinking water more efficiently.
Key words- drinking water, E. coli, coliform organisms, clostridium

INTRODUCTION

Water is the most important natural resource for the sustenance of life. Two thirds of the earth surface is covered with water, but only one percent is fresh water available for drinking purposes. In developing countries, many people are struggling to get access to clean and safe drinking water. About 1.1 billion people in the world do not have access to safe drinking water1; two and a half billion people do not have proper sanitation and t 1.5 million children death has been reported each year from diarrheal diseases2.

Water borne diseases account for about one third of intestinal infections worldwide and are responsible for 40% of deaths3-6. Ideally, all water intended for drinking should be free from pathogens and if not properly treated and monitored, will represent a very serious health hazard. The danger is often compounded by the fact that even water which appears to be clear may be contaminated with several pathogenic microorganisms. The direct measurement of pathogens is complex, but water testing often uses the presence of coliforms including Escherichia coli (E. coli) as an indicator of contamination7. Additionally, these indicator organisms are easily, cheaply and reliably detected in water samples1,2,8,9.

The most widely adopted procedures for detecting and enumerating coliform organisms and presumptive E coli are the Most Probable Number and membrane filtration techniques10. The Multiple Tube Technique11 and the Defined Substrate Technology are variations of the MPN method12,13.

Fig. 1: Map of Mauritius showing the location of the three stations
Clostridium perfringens are spore forming gram-positive, sulphite reducing anaerobic bacteria, and is another group of micro-organism that are considered as a reliable indicator for monitoring sanitary quality of water. Clostridium spores are resistant to high temperatures and the spores can persist for long periods in water supplies where anaerobic conditions exist. The presence of Clostridium perfringens in treated water is an indication of faecal pollution14-16.
Objective
In Mauritius, the Central Water Authority has the sole responsibility of providing safe drinking water and the prime concern is to safeguard water quality against health risks associated with the presence of pathogenic organisms. The main objectives of the present work are:
• To determine the physico-chemical parameters on different types of water samples (Raw, filtered and chlorinated)
• To monitor the presence of coliform organisms, presumptive E. coli and Clostrium perfringens on the water samples.
• To confirm the efficiency of treatment processes of water.
MATERIALS AND METHOD

Chemicals
Mac Conkey Broth (purple) CM 0505 (CM 5a), Brilliant Green Broth, Tryptone water, EC Broth, and Membrane clostridium Perfringens (m-CP) agar base make Oxoid were obtained from Basingstoke Hampshire, England. Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Staphylococcus aureus ATCC 6538, Enterobacter aerogenes ATCC 13048, and Clostridium sporogenes ATCC 13124 make Oxoid were obtained from Remel Incorporation, England. Kovac’s Reagent for indoles make Fluka were was obtained from Sigma-Aldrich Chemie, England. D-Cycloserine – SR0188E were obtained from Oxoid Ltd England.
Glassware
All glassware that used were of grade A and was certified in conformity to norm ISO 8350:2007. The glassware’s were cleaned, rinsed with double-distilled water and oven dried at 105C.
Stations
For this study, three different water Stations (Fig 1) were selected.

Station 1: La Marie Treatment Plant, found in the central part of Mauritius, receives raw water from Mare-aux-Vacoas impounding reservoir. The Treatment Plant uses two types of conventional treatment: Slow sand filtration and use of aluminium sulphate for flocculation. The filtered water is then chlorinated.

Station 2: Cote D’Or reservoir, also found in the central region draws water from river Terre Rouge. The raw water is filtered under pressure and then chlorinated.

Station 3: Plaine des Papayes reservoir, located in the northern region of the island, receives raw water from Morcellement St André borehole. The water is filtered by pressure filter and chlorinated. The treated water is then mixed with raw water from Nicolière Reservoir.

Samples
Water samples were collected from the three stations for the period of August to December 2014. The physico-chemical (pH, turbidity and conductivity) and bacteriological parameters of the water samples were monitored on a monthly basis. Samples of water were collected in 100ml sterile bottles. In case of treated water, 0.1ml of fresh sodium thiosulphate (1.8%w/v) was added to neutralize the free and combined residual chlorine of the water, thus eliminating the effect of chlorine on bacteria. All samples were transported to the laboratory in insulated ice-box that was chilled with frozen refrigerant packs to maintain the temperature below 10oC. All the samples were analysed in triplicate.
Physico-Chemical Parameters
Determination of pH
The pH of the water samples was determined using a pH meter (Metler Toledo). The apparatus was calibrated using buffer solutions of pH 4 ± 0.02 and 7 ± 0.02 prior to measurement. All the pH values were recorded to two decimal place.

Determination of Turbidity
The turbidity of the water samples was determined using a Turbidimeter (Lovibond). The apparatus was calibrated using standard formazin solution of 10NTU, 20NTU and 50NTU. All the turbidity values were recorded to two decimal place. An Analytical Quality Control standard of 10 NTU was used to validate the data.

Determination of Conductivity
The conductivity of the water samples was determined using a conductivity meter (Metler Toledo). The apparatus was calibrated using standard solution (NaCl) of 1413 µs/cm. An Analytical Quality Control standard of 84µs/cm was used to validate the data.
Bacteriological analyses
Detection of Coliform Organisms
The ISO 9308-2:1990- first edition11, method was used to detect and enumerate Coliform Organisms and Presumptive E. coli. The double strength broth solution was prepared by dissolving 80g of Mac Conkey powder in 1000ml of double distilled water which was diluted twice to obtain the single strength broth. 50ml and 10ml of Mac Conkey at double strength concentration and 5ml volumes at single strength concentration were dispensed in bottles and test-tubes of appropriate volumes. An inverted Durham tube was introduced in all the individual tubes in such a way that no air bubbles remained trap. The test tubes were capped and sterilized by autoclaving (Pressure of 1.2bar at 121oC for 15 minutes).

The water sample was mixed thoroughly and was inoculated under aseptic conditions. Using heat sterilized pipettes, one 50ml volume and five 10ml volume of water were transferred to tubes of corresponding volumes of double strength medium. Five 1ml volumes of water were dispensed into tubes containing 5ml of single strength medium. The tubes were then incubated at 37 ± 0.5oC for 24-48 h. Tubes showing a yellow colour change in the medium and presence of gas in the Durham tubes were considered as positive presumptive test for Coliform Organisms. Tubes in which there was no gas production or colour change were incubated again for further 24 h.
Quality control was performed for each batch of samples analysed. A positive and a negative control for Mac Conkey Broth were inoculated to confirm the selectiveness of the medium. The negative control used was Staphylococcus aureus ATCC 6538 and the positive used was Escherichia coli ATCC 25922.
Confirmation of Coliform Organisms and Enumeration of Coliform Organisms17
The medium was prepared by dissolving 40g of Brilliant Green Broth powder in1000ml of double distilled water. 5ml of the broth were dispensed in test-tubes of appropriate volumes and an inverted Durham tube was introduced in all the individual tubes in such a way that no air bubbles remained trap. The test tubes were capped and sterilized by autoclaving (Pressure of 1.2 bar at 121oC for 15 minutes).
Subcultures from positive tubes obtained from the presumptive tests of coliforms were transferred to tubes containing Brilliant Green Broth. The tubes were incubated at 37 ± 0.5oC. After 24 h incubation, tubes showing the presence of gas in the Durham tubes were considered as positive for Coliform Organisms. The tubes that did not show presence of gas were incubated again for further 24 h. Hence, the number of positive tubes was counted and the Most Probable Number (MPN) of Coliform Organisms in 100ml of sample was determined by reference to statistical tables.
Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 was inoculated as positive and negative control respectively to confirm the selectiveness of Brilliant Green Bile Broth.

Confirmation of Presumptive Escherichia Coli
37g of Escherichia coli Broth (EC Broth) powder was dissolved in 1000ml of double distilled water. 5ml of EC Broth were dispensed in test-tubes of width 16mm. 15g of Tryptone powder was dissolved in 1000ml of double distilled water. 5ml of Tryptone water were dispensed in test-tubes. Subcultures from positive tubes of presumptive coliform organisms were simultaneously transferred to tubes containing EC broth and Tryptone water and the tubes were then incubated at 44 ± 0.25oC for 24 h. A few drops of Kovacs reagent were added and a pink colour developed in the reagent layer was considered as positive. The number of positive tubes was counted and the Most Probable Number (MPN) of presumptive E. coli in 100ml of sample was determined statistically.
Quality control was performed for each batch of samples inoculated to ensure the selectiveness of the medium. Escherichia coli ATCC 25922 was used as positive control while Staphylococcus aureus ATCC 25923 was used as negative control for EC Broth. A positive (Escherichia coli ATCC 25922) and a negative control (Enterobacter Aerogenes ATCC 13048) for Tryptone water were inoculated to confirm the selectiveness of the medium.
Detection and Enumeration of Clostridium perfrigens
The Membrane Filtration method was used to process water samples for Clostridium Perfringens enumeration18. 35.55g of m-CP agar was dissolved in 500ml of double distilled water, sterilized and cooled to about 50oC, in which D-cycloserine was added. The mixture was poured in sterile petri dishes. 100ml of sample was filtered using 0.45mm cellulose acetate filter and then placed grid-side upwards on the m-CP agar. The petri dish was incubated for 24 h at 44 ± 1oC. After incubation, all plates having opaque yellow colonies were exposed to ammonium hydroxide vapours. Colonies that turn pink or red after exposure were counted positive for Clostridium perfringens.
Quality control was performed for each batch of water samples analysed. A positive (Clostridium perfringens ATCC 13124) and a negative control (Escherichia coli ATCC 25922) for m-CP agar were inoculated to confirm the selectiveness of the medium.
RESULTS AND DISCUSSION
Sites
Samples were collected from three different stations, La Marie Treatment Plant (Station 1), Cote D’Or reservoir (Station 2) and Plaine des Papayes reservoir (Station 3) (Fig.1). These three stations were chosen since the raw water undergoes different type of treatment in these Stations.

Fig. 2: Colonies of Clostridium perfringens on m-CP agar in (a) Raw water (b) Water treated with alum; (c) chlorinated (treated) water at Station 1.

Physico-chemical Parameters
Physico-chemical tests such as pH, turbidity and conductivity were performed on all the different water samples (raw, filtered & treated).
pH measurements
pH is regarded as one of the most important operational water-quality parameters and has to be controlled at the different stages of water treatment to ensure satisfactory water clarification and disinfection. For effective disinfection with chlorine, the pH should preferably be less than 8. The pH of the water entering the distribution system must be controlled to minimize the corrosion of water mains and pipes in household water systems. Failure to do so can result in the contamination of drinking-water
Table 1: Physico-chemical Parameters of stations 1-3 for the period August –December 2014
Parameters Station water sample August September October November December Permissible limits

pH 1 Raw 6.90 ± 0.02 6.94 ± 0.06 6.79 ± 0.04 6.94 ± 0.02 6.84 ± 0.11

6.5-8.5
Filtered with Alum 6.06 ± 0.01 6.37 ± 0.05 6.35 ± 0.02 6.34 ± 0.02 6.27 ± 0.03
Filtered (slow sand) 7.50 ± 0.06 7.26 ± 0.06 7.27 ± 0.04 7.37 ± 0.12 7.57 ± 0.25
Treated 6.35 ± 0.06 6.68 ± 0.15 6.73 ± 0.32 6.67 ± 0.10 6.56 ± 0.21
2 Raw 6.87 ± 0.03 6.78 ± 0.04 6.78 ± 0.10 6.84 ± 0.08 6.86 ± 0.02
Filtered 6.84 ± 0.08 6.74 ± 0.05 6.85 ± 0.01 6.79 ± 0.08 6.77 ± 0.30
Treated 6.72 ± 0.07 6.87 ± 0.02 6.78 ± 0.04 6.80 ± 0.06 6.86 ± 0.01
3 Raw 7.68 ± 0.15 7.57 ± 0.04 7.71 ± 0.10 7.67 ± 0.16 7.49 ± 0.02
Filtered 7.72 ± 0.81 7.55 ± 0.05 7.71 ± 0.78 7.66 ± 0.14 7.52 ± 0.30
Treated 7.17 ± 0.03 6.87 ± 0.02 6.85 ± 0.02 6.80 ± 0.06 6.86 ± 0.01

Turbidity 1 Raw 3.58 ± 0.37 3.60 ± 0.04 5.63 ± 0.12 5.63 ± 0.85 4.89 ± 0.13

5 NTU
Filtered with Alum 1.58 ± 0.51 1.81 ± 0.03 2.28 ± 0.07 2.13 ± 0.73 2.93 ± 0.82
Filtered (slow sand) 1.40 ± 0.05 1.62 ± 0.11 2.11 ± 0.12 2.02 ± 0.18 2.25 ± 0.14
Treated 1.96 ± 0.20 2.89 ± 0.03 4.15 ± 0.08 4.18 ± 0.86 3.95 ± 0.84
2 Raw 2.42 ± 0.03 5.63 ± 0.11 2.80 ± 0.05 2.23 ± 0.08 2.35 ± 0.05
Filtered 1.11 ± 0.13 2.37 ± 0.23 1.45 ± 0.76 1.28 ± 0.29 0.92 ± 0.13
Treated 1.24 ± 0.10 2.12 ± 0.12 1.59 ± 0.10 2.82 ± 0.19 2.18 ± 0.21
3 Raw 3.80 ± 0.20 4.10 ± 0.10 3.97 ± 0.23 4.34 ± 0.29 4.58 ± 0.32
Filtered 3.78 ± 0.18 4.17 ± 0.23 3.90 ± 0.70 4.25 ± 0.19 4.43 ± 0.19
Treated 1.57 ± 0.18 2.12 ± 0.12 2.80 ± 0.35 2.82 ± 0.19 2.18 ± 0.21

Conductivity 1 Raw 77.87 ± 2.48 75.26 ± 0.75 71.30 ± 1.10 59.00 ± 0.00 64.00 ± 3.45

2000 µs/cm
Filtered with Alum 65.33 ± 3.65 65.20 ± 0.56 60.67 ± 0.17 64.27 ± 0.12 66.70 ± 0.25
Filtered (slow sand) 108.2 ± 0.55 109.0 ± 1.00 98.77 ± 1.27 107.2 ± 0.67 102.6 ± 0.32
Treated 64.90 ± 0.00 65.90 ± 0.30 63.70 ± 0.03 62.79 ± 2.01 61.06 ± 0.25
2 Raw 108.6 ± 0.95 110.4 ± 2.01 109.2 ± 2.20 110.3 ± 3.30 109.0 ± 0.74
Filtered 110.5 ± 1.76 110.5 ± 1.43 111.2 ± 0.91 109.4 ± 2.15 110.2 ±.0.46
Treated 103.5 ± 2.10 100.8 ± 1.70 108.5 ± 0.10 99.53 ± 5.41 92.33 ± 0.47
3 Raw 97.00 ± 3.46 110.4 ± 2.01 100.4 ± 3.43 110.3 ± 3.30 109.0 ± 0.74
Filtered 110.4 ± 3.43 110.5 ± 1.43 98.76 ± 0.60 110.2 ± 0.46 107.2 ±.0.56
Treated 207.3 ± 3.05 228.0 ± 6.27 215.5 ± 6.24 253.0 ± 7.41 248.3 ± 6.47

and in adverse effects on its taste, odour, and appearance. The optimum pH will vary in different supplies according to the composition of the water and the nature of the construction materials used in the distribution system, but is often in the range 6.5–8.5. Extreme pH values can result from accidental spills, treatment breakdowns, and insufficiently cured cement mortar pipe linings.

Given the influence of acidity or alkalinity can have on bacterial populations, the pH of the various samples of raw, filtered and treated water was measured. Table 1 and Fig. 1 depict the results of pH measurements of water samples (raw, filtered and treated). At Station 1, lower pH values were observed after filtration with aluminium sulphate. This may be due to the acidic nature of the coagulant while when the raw water was filtered using slow sand filtration, higher values for pH were observed due to the alkaline nature of substances like CaCO3, Ca(OH)2 and CaO present in the sand of the filtration beds. For Station 2, there was no significant variation in the pH values for the raw, filtered and treated water since raw water was filtered under high pressure using no chemical treatment. For Station 3, a lower value for pH (6.80 to 7.17) was observed for treated water as compared to the raw or filtered (7.49 to 7.72). The low pH obtained for the treated water was due to the mixing of the two waters (surface water and borehole water). However, it should be mentioned that the pH was within the permissible limit set by Environmental Protection Act, 2002 for drinking water standards.
Turbidity
Turbidity is the measurement of cloudiness of water and is caused by suspended or dissolved particles or sediment. Turbidity has an esthetic impact on the water quality. It is essential to eliminate the turbidity of water in order to effectively disinfect it for drinking purposes as well as improving esthetic impact on water quality. The turbidity is measured based on the amount of light scattered by the water and the unit of measurement is a Nephelometric Turbidity Unit (NTU) (Table 1, Fig. 2)

Over the period of study (five months), an increase in the turbidity of raw water (3.6 to 5.6 NTU) was observed at Station 1, from October to November 2014. This increase was due to a considerable decrease in the volume of water of the impounding reservoir, as there was no heavy rainfall in that region. Also, this increase was due to the mixing of raw water from another source. The two other Stations did not have a considerable change in the turbidity values during the five months of study.
Filtration of raw water reduces the level of turbidity to about 50-60 %. However, this was not noted at Station 3, as the filtered water is mixed with untreated raw water coming from another impounding reservoir
Conductivity
Conductivity is a measure of the water’s ionic activity and content. The conductivity of raw, filtered and treated water is summarized in Table 1 and Fig. 3. The higher values of conductivity observed for filtered water after slow sand filtration may be due to the alkaline nature of sand. The decrease in the conductivity values for treated water may be due to the addition of lime before chlorination. No significant variation in conductivity was observed for Station 2. A higher conductivity was obtained for treated water samples at Station 3 and this was due to the mixing of treated water with borehole water. It is known that borehole water is generally rich in ions.

Bacteriological analyses
For the past decades, the standard faecal indicator bacteria, E. coli and the total coliform organisms have been used as indicator organisms to monitor the efficiency of treatment processes and the quality of treated water to drinking water norms7. Several studies have demonstrated the inadequacy of coliform organisms to detect the presence of pathogens in water bodies19.
In the present study, bacteriological analyses of coliform organisms, presumptive E. coli and Clostridium perfringens were performed on all the water samples collected.
Coliform Organisms and E. coli
The raw water samples of the three different Stations were found to contain a large numbers of coliform indicator organisms in the range of 600 and 8400 MPN of bacteria (Table 2). A larger population of bacteria could be detected during the warmer months of October, November and December as high temperature favours multiplication of bacteria. Filtration helped in the removal of indicator microorganisms as the number of bacteria was found to reduce considerably after the different method of filtration. No coliform organisms or Presumptive E. coli bacteria were detected in treated water at Station 1, indicating that the treatment of the water effectively controlled any contamination. However, at Station 2, indicator organisms were detected in treated water for the month of November where a MPN of 41.33

Table 2: Bacteriological analyses of samples collected from the stations 1-3
Parameters
(units) Treatment Plant water sample August September October November December Permissible limits

Coliform Organisms
(MPN)

1 Raw 1883 ± 758 5750 ± 1991 8366 ± 548 8400 ± 645 8200 ±537

0 /100ml

Filtered with Alum 57.61 ± 6.35 47.67 ± 10.97 115.0 ± 39.84 138.0 ± 39.83 126.0 ± 34.5
Filtered (slow sand) 160.0 ± 0.00 138.0 ± 39.82 167.3 ± 10.00 149.0 ± 20.80 167.0 ±10.00
Treated

2 Raw 1516 ± 284.3 1566 ± 217 5750 ± 1992 8366 ±548.48 8000 ± 0.00
Filtered 92.00 ± 4.00 126.0 ± 10.00 181.0 ± 3.00 174.33 ± 11.55 138.0 ± 39.84
Treated

3 Raw 2400 ± 0.00 2600 ± 200 3133 ± 1270 3266 ± 115 3433 ± 207
Filtered 173.7 ± 10.97 114.7 ± 39.26 107.7 ± 11.54 174.3 ± 11.55 138.0 ± 39.84
Treated

Presumptive
E.coli
(MPN)

1 Raw 600 ± 200 1883 ± 758 5750 ± 1991 6900 ± 195.8 5710 ± 1991

0 /100ml

Filtered with Alum 17.00 ± 5.00 41.30 ± 10.97 41.33 ± 10.97 54.00 ± 1.00 47.00 ± 10.00
Filtered (slow sand) 5.00 ± 0.00 24.00 ± 0.00 79.33 ± 21.90 41.30 ± 10.96 79.33 ± 21.93
Treated

2 Raw 666.7 ± 115.5 733.3 ± 115.5 1116 ± 548 2100 ± 100 2300 ± 200
Filtered 54.00 ± 5.00 63.00 ± 54.00 1610 ± 4.00 174.33 ± 11.50 54.00 ± 39.84
Treated

3 Raw 666.7 ± 115.5 733.3 ± 115.5 1883 ± 758.3 5750 ± 199.9 4866 ± 461.9
Filtered 115.0 ± 39.84 102.3 ± 54.24 150.1 ± 50.81 41.33 ± 10.97 66.67 ± 21.94
Treated

Clostridium Perfringens
(CFU)

1 Raw 10.00 ± 0.00 8.00 ± 0.00 11.00 ± 0.00 12.00 ± 0.00 11.00 ± 0.00

0 /100ml

Filtered with Alum 4.00 ± 0.00 4.00 ± 0.00 5.00 ± 0.00 6.00 ± 0.00 4.00 ± 0.00
Filtered (slow sand) 5.00 ± 0.00 3.00 ± 0.00 6.00 ± 0.00 8.00 ± 0.00 5.00 ± 0.00
Treated 0.00 ± 0.00 0.00 ± 0.00 2.00 ± 0.00 1.00 ± 0.00 0.00 ± 0.00

2 Raw 8.00 ± 0.00 10.00 ± 0.00 10.00 ± 0.00 13.00 ± 0.00 14.00 ± 0.00
Filtered 3.00 ± 0.00 5.00 ± 0.00 6.00 ± 0.00 8.00 ± 0.00 5.00 ± 0.00
Treated 0.00 ± 0.00 0.00 ± 0.00 0.00 ± 0.00 1.00 ± 0.00 0.00 ± 0.00

3 Raw 4.00 ± 0.00 6.00 ± 0.00 5.00 ± 0.00 6.00 ± 0.00 6.00 ± 0.00
Filtered 3.00 ± 0.00 5.00 ± 0.00 4.00 ± 0.00 5.00 ± 0.00 5.00 ± 0.00
Treated 0.00 ± 0.00 1.00 ± 0.00 2.00 ± 0.00 0.00 ± 0.00 3.00 ± 0.00

was obtained for coliform organisms and a MPN of 21.33 for presumptive E. coli. At the Station 3, coliform organisms and presumptive E. coli were detected in treated water. This may be due to untreated water coming directly from other impounding reservoir.

Clostridium perfringens
Colonies of Clostridium Perfringens were enumerated in raw water samples ranging from 4 to 14 CFU. Filtration helped in the removal of Clostridium Perfringens. In some samples of treated water, Clostridium Perfringens colonies were observed thus indicating that these microorganisms resisted the disinfection by chlorine. The number of colonies in treated water ranged from 0 to 3 CFU (Fig. 2). This is in line to what has been reported by Fujioka 1998 that some bacteria have been recovered from chlorinated water.

Statistical correlation
A correlation of turbidity and Clostridium perfringens in treated water was determined within the three Stations. It was observed that there is a strong positive correlation of turbidity with Clostridium perfringens at Station 1 (r = 0.63) and Station 2 (r = 0.77). However at Station 3, there was a weak positive correlation (r = 0.17).
CONCLUSION
In this study we were able to show that treatments such as filtration ensure a reduction in the level of organic and particulate matter hence reducing turbidity of the water. Also, it was found that although chlorination eliminates conventional microorganisms (coliform bacteria and E. coli), still the more resistant bacteria, Clostridium perfringens were not affected completely during drought. This confirms that the concept of water potability does not depend only on indicator organisms but also on pathogens as they can become health threats. Thus the detection of Clostridium perfringens in water samples can reveal the possible presence of waterborne pathogens and efficacy of treatment processes. Therefore, it would be worthwhile to include Clostridium perfringens in the monitoring of water quality in order to ensure that the community receives potable water free from pathogens. Nevertheless with the increase in population and consequent environment pollution, threats from other water-borne pathogens such as Cryptosporidium and Giardia should not be disregarded. Consequently the monitoring of bacterial water quality and efficacy of treatment processes should be an ongoing process.
REFERENCES
1) Odonkor T and Ampofo K: Escherichia coli as an indicator of bacteriological quality of water: an overview. Microbiology Research 2013; 4:5-10.
2) Cabral PSJ: Water microbiology, bacterial pathogens and water. International Journal of Environmental Research and Public Health 2010; 7(10):3657-3703.
3) Hunter PR, Abdelrahman SH, Antni-Agyei P, Awuah E, Chapell E, Dalsgaard A, Ensink J and Potgeiter N: Research needs assessment to strengthen capacity in water sanitation research in Africa. Health Research Policy and Systems 2014;12:1-8.
4) Edberg SC, Rice EW, Karlin RJ and Allen MJ: Escherichia coli: the best biological drinking water indicator for public health protection. Journal of Applied Microbiology 2000;88:106S-116S.
5) Edge TA, Khan UH, Bouchard R, Guo J, Hill S, Locas A, Moore L, Neumann N, Nowak E, Payment P, Yang R, Yerubandi R and Watson S: Occurrence of waterborne pathogens and Escherichia coli at offshore drinking water intakes in lake Ontario. Applied and Environmental Microbiology 2013; 79:5799-5813.
6) Herwaldt BL, Graun GF, Strokes SL and Julranek K: Waterborne disease outbreaks, 1989 – 1990. Morbid Mortal Weekly Report 1991; 40:1-21.
7) Vierheilig J, Frick C, Mayer RE, Kirschner AKT, Reischer GH, Derx J, Mach RL, Sommer R and Farnleitner AH: Clostridium perfringens is not suitable for the indication of fecal pollution from ruminant wildlife but is associated with excreta from nonherbivorous animals and human sewage. Applied and Environmental Microbiology 2013; 79: 5089-5092.
8) Ashbolt NJ, Grabow W, Snozzi M: WHO water series, London, IWA publishing 2001:289-315.
9) Naidoo S and Olaniran AO: Treated wastewater effluent as a source of microbial pollution of surface water resources. International Journal of Environmental Research and Public Health 2014; 11:249-270.
10) Rompre A, Servais P, Baudat J, De Roubin MR and Laurent P: Detection and enumeration of coliforms in drinking water, current methods and emerging approaches. Journal of Microbiological Methods 2002; 49(1):31-54.
11) ISO 9308-2: Water Quality – Detection and enumeration of coliform organisms, thermos-tolerant coliform organisms and presumptive Escherichia coli, multiple tube (Most Probable Number) method 1990.
12) Edberg CS, Allen JM and Smith DB: Defined substrate technology method for rapid and specific simultaneous enumeration of total coliforms and Escherichia coli from water. Collaborative Study Journal-Association of Official Analytical Chemists 1991; 74(3):526-529.
13) Cowburn JK, Goodall T, Fricker EJ, Walter KS and Fricker CR: A preliminary study of the use of colilert for water quality monitoring. Letters in Applied Microbiology 1991;19:50-52.
14) Health Protection England: The characteristics, diagnosis and epidemiology of Clostridium perfringens 2008.
15) World Health Organisation: Guidelines for drinking water quality, Third Edition, 2008; 1: 120-124.
16) Siegrist I: Clostridium perfringens, their properties and their detection. AnalytiX 2011; 10(4): 1-5.
17) ISO 9308–2: Water quality – Enumeration of Escherichia coli and coliform bacteria – Part 2: Most Probable Number 2012.
18) ISO 9308 – 1: Enumeration of Escherichia coli and coliform bacteria – part 2: Membrane filtration method for waters with low bacterial background flora 2014.
19) Tyagi VK, Chopra AK, Kazmi AA and Kumar A: Alternative microbial indicators of faecal pollution: current perspective. Journal of Environmental Health 2006; 3:205-216.
20) Fujioka RS and Shizumura KL: Clostridium perfringens, a reliable indicator of stream water quality. Water Pollution Control 1985; 57(10): 986-992.