CHAPTER FIVE
5.0 Discussion
An acceptable pH for drinking water is between pH 6.5 to pH 8.5, recommended by WHO as a guideline value and in the absence of a distribution system acceptable range may be broader. However, the water samples examined in this study were within the acceptable pH range. For the presumptive coliforms test, the WHO guideline for both treated and untreated water samples is 0/100 ml (WHO, 2009), but in an occasional untreated water sample 3 coliform/100 ml are allowed on the condition that these would not be found in consecutive water samples (WHO, 2010).The coliform group as an indicator bacteria are used to evaluate the portability of drinking water and the presence of any coliform organisms is an indication of a contaminated source, inadequate treatment or post treatment contamination (Mark and Gordon, 2007).
In unpiped water supplies, sometimes up to 10 coliforms/l00 ml are allowed but they should not occur repeatedly; if occurrence is frequent and sanitary protection cannot be improved, an alternative source must be found if possible (WHO, 2010). In this study, 70% of the untreated and 30% of the treated water samples were positive for MPN, showing a high contamination and risk to public health. The detection of faecal (thermotolerant) coliform organisms provide definite evidence of faecal pollution (WHO, 2009) and they were found in 30% of the positive samples. Search for Streptococcus faecalis is not carried out routinely. Its main value is when doubt is expressed that large numbers of irregular types of coliforms found in a sample of water are of faecal origin. Confirmation of faecal pollution would then rely on finding Streptococcus faecalis in the water. Since they survive longer in water than coliform bacteria they should be referred as indicator of faecal pollution in water and shellfish. In the present study they were found only in 22% of the water samples examined. The main value of colony counts lies in the comparison of results obtained from regular samples from the same supply so that any significant change from the normal range in a particular location can be detected (WHO, 2009). As the Standard Plate Counting (SPC) in most of the untreated water samples was very high, it is therefore desirable to disinfect all supplies of drinking water before distribution. Supplies derived from protected sources which are distributed without disinfection should be similar in quality to that of disinfected drinking water. Where it is impracticable to supply water to consumers through a piped distribution network and where untreated sources such as wells, bore-holes and springs which may be naturally pure must be used, considerable reliance should be placed on sanitary examination and not exclusively on the results of bacteriological examination (Feacham, 2010). The high percentage of E. coli (30%) provides a definite evidence of faecal pollution in water. Staphylococcus aureus (13%) which is relatively recently accepted as indicator organisms in food and water, provides a useful indication that faecal contamination has occurred in water. Pseudomonas spp. are common inhabitant of soil and water carried in small numbers in the faeces of man and animals. These were isolated in about 9% samples and are of public health importance as some species cause a variety of suppurative infections in man. Enterotoxigenic strains of pseudomonas spp. alongwith other species of Enterobacter, Klebsiella and Acinetobacter have been isolated from cases of infantile diarrhoea in Addis Ababa during surveys in 1974 and 1977 (Back et al., 2007). Enterotoxigenic species of proteus with other enterotoxigenic bacteria have also been reported in a study on food and water from an Ethiopian community (Jiwa et al., 2011). Environmental bacteria include Acinetobacter spp., and Bacillus spp. which are usually found in soil. Presence of such high bacterial counts and presence of faecal coliforms and other indicator organisms as Streptococcus faecalis, Staphylococcus aureus indicate inadequate treatment, post treatment contamination and contaminated water sources. Coliform count showed a relatively high degree of contamination of water from the untreated source and a reduced degree from the treated source. In the three study areas, water from the river showed more contamination with Elemere having the highest level of coliform density of 22.1×106, followed by Asomu with 19.4×106 and Malete (13.6×106). This could be because of the nature of its use such as washing, fishing and irrigation. However, open defecation is the leading cause of the high amount of coliform present in these water bodies. Dams also showed a high coliform density with Asomu (17.4×106) having the highest volume of contaminant. This was closely followed by Elemere with a density of 13.7×106 and Malete with 9.3×106. Certain treated water also contained coliform, this could be because of contamination of water when stored in the reservoir. Therefore, everything possible should be done to prevent pollution of drinking water, special attention being given to safe disposal of excreta and prompt prevention of open defecation. Nevertheless, the significance of routes of transmission other than drinking water should not be underestimated, as the provision of a safe potable water supply by itself will not necessarily prevent infection without accompanying improvement in sanitation and personal habits. Education in simple hygiene is also essential.
