Surveillance of water quality to ensure microbiological safety is a vital public health function to prevent water borne diseases. Bacterial total coliform and Escherichia coli ( E. coli) examination provide indication of the hygienic condition of drinking water and are major tools in the assessment of the health risk borne by pathogen in water. Unfortunately, there is insufficient information on the total coliform and E. coli amounts in the common drinking water sources in Mbarara Municipality, Uganda despite the eminent anthropogenic sources of contamination. Hence the study established the sanitary risk and quantified the total coliform and E. coli load in selected drinking water sources in Mbarara Municipality, Uganda. A total of 70 water samples were collected from selected boreholes, springs, wells and rainwater in Nyamitanga, Kamukuzi and Kakoba divisions of Mbarara municipality. The water samples were analysed for total coliform and E. coli abundance using the American Public Health Association (APHA) standard method. The total coliform and Escherichia coli counts were compared with the World Health Organization (WHO) drinking water standard guidelines. The findings indicate that all the studied groundwater sources (boreholes, springs and wells) in Mbarara Municipality were not compliant to either both or one of the WHO total coliform (<10 CFU/100 ml) and E. coli (0 CFU/100 ml) criteria for drinking water hence they are unsuitable for drinking without treatment e.g. boiling etc. Only rainwater collected from Mbarara University of Science and Technology met the WHO total coliform and E. coli criteria for drinking water thus is suitable for drinking without any treatment. There is a strong linkage between bacterial (total coliforms and E. coli) water quality and water source sanitation, as well as the proximity of latrines, animal farms and landfills around the water sources. Mbarara municipal council should therefore ensure effective and regular operation and maintenance of the drinking water sources through the adoption and promotion of appropriate water safety plans.
Water is an essential element of life on planet Earth and about 75% of the earth’s surface is covered by it [
Waterborne diseases and death continue to be a worldwide burden in both developed and developing countries, the heaviest being diarrhoeal diseases. In Uganda, waterborne diseases have been found to be among the major public health problems [
The prevalence of waterborne diseases in Uganda is also attributed to poor hygiene and environmental sanitation including inadequate supply of safe water [
In Mbarara district, most rural people get water mainly from borehole (95%), protected spring (98%), rainwater (96%) and less from tap water (19%) while only 47.5% of the total population in Mbarara Municipality can afford piped water. The remaining 52.5% of the population in the municipality use unprotected groundwater water sources like boreholes, springs, wells and rainwater etc to access drinking water [
The Water borne diseases could be prevented by adopting water safety plans which include locating latrines and other point sources of potential faecal contamination sufficiently far (beyond 30 metres) from groundwater sources used for drinking purposes to ensure that the risk of pathogen survival is very low. Demarcating protection zones clearly and restricting anthropogenic activities (e.g., dumping of toxic waste, the discharge of undesirable effluents and the use of agricultural fertilizers and pesticides) that may affect water quality [
Bacterial total coliform and Escherichia coli (E. coli) examination provide indication of the hygienic condition of drinking water and are major tools in the assessment of the health risk borne by pathogen in water. Unfortunately, there is insufficient information on the total coliform and E. coli amounts in the common drinking water sources in Mbarara Municipality, Uganda despite the eminent sources of contamination. Hence the study established the sanitary risk and quantified the total coliform and E. coli load in selected drinking water sources in Mbarara Municipality, Uganda.
Mbarara municipality is densely populated with population of 194,973 people [
A cross-sectional sanitary assessment was carried out in each of the selected drinking water sources to identify the risks for contamination with faecal bacterial organisms similar to what [
shes, Kampala city, Uganda. The assessment adapted the standardised procedure which involved completing a ten-point standardised data form with a set of questions having a yes and no options for designated risks [
Water samples were collected from the selected water sources from January, 2016 to May, 2016. All water samples were collected and preserved following the Standard methods for Examination of water and wastewater [
Water samples that were not immediately analysed for bacteriological parameters (total coliforms, Escherichia coli), were preserved in a refrigerator at temperatures below 4˚C to slow down the chemical reactions in the water [
The Most Probable Number (MPN) method [
Five tubes containing double strength MacConkey broth (10 ml) were each inoculated with a sub water sample (10 ml) from the same water sample. Using a sterile pipette, five tubes containing single strength MacConkey broth (5 ml) were each inoculated with a sub water sample (5 ml) from the same water sample. To other five tubes containing single strength MacConkey broth (5 ml), a sub water sample (1 ml) was inoculated into each tube using a sterile pipette. The tubes were closed and shook to distribute the sample uniformly throughout the medium and to ensure that the Durham tube inside had no air. The tubes were then incubated at 35˚C for 24 hours. The above procedure was done to each of the water samples collected. After 24 hours the incubated tubes were examined for gas production and lactose fermentation. The tubes that showed production of gas and acid were isolated, recorded and considered positive for total coliforms. The MPN of total coliform was read off from the Standard MPN table.
From each of the positive tubes for total coliforms, a sample (1 ml) was removed and inoculated into MacConkey broth single strength (5 ml) and incubated at 44.5˚C for 48 hours. The tubes were examined for gas production and acid production. The positive tubes were isolated and were taken as positive for faecal coliforms. Using a sterile inoculating loop, cultures in the tubes positive for faecal coliforms were inoculated on MacConkey Agar and sub cultured at 37˚C for 24 hours. The sub cultures were examined for the growth of E. coli colonies. The positive colonies were inoculated using a sterile loop into different tubes containing tryptone water and incubated at 37˚C for 24 hours. To each tube of tryptone water Kovac’s reagent (0.1 mL) were added and mixed gently. The presence of Indole was indicated by a red colour in the Kovacs reagent, forming a film over the aqueous phase of the medium. Presence of Indole, growth, and gas production showed the presence of E. coli which was later confirmed using the IMViC reactions.
The most probable number of E. coli in each samples was determined by recording down the tubes positive for E. coli in a sample with respect to the different amounts of the sub samples that were inoculated for total coliforms (10, 5 and 1 ml) and the MPN of E. coli was read off from the Standard MPN table.
The descriptive statistics (range, mean, standard deviation, coefficient of variation) of the MPN total coliform and E. coli counts of the water samples were tabulated. The total coliform and E. coli counts in the water sources were compared with the WHO drinking water standards. Mean differences of the total coliform and E. coli counts between water sources were compared using one- way ANOVA (F) test. The relationship between bacterial counts with sanitary risk score, proximity of latrines and landfills and physico-chemical parameters [
Sanitary inspection is a vital tool in assessing risks of the bacterial contamination of water sources including spring water [
All the six groundwater sources studied faced some risk of contamination with bacterial faecal organisms. The qualitative aggregate risk scores ranged from medium to high. Three of the water sources had a medium risk score (31% - 50%) and three had a high risk score (51% - 80%) as shown in
Water source | Risk observed | Percent risk score | Qualitative risk profile |
---|---|---|---|
Borehole (Nyam. S. S) | 3, 5, 6, 9, 10 | 50 | Medium |
Borehole (Shud. S. S) | 3, 4, 5, 6, 9, 10 | 60 | High |
Spring (Kisw) | 3, 5, 6, 7, 10 | 50 | Medium |
Spring (Kise) | 3, 5, 7, 9, 10 | 50 | Medium |
Well (Kise) | 3, 5, 6, 7, 9, 10 | 60 | High |
S. well (Nyam) | 3, 4, 5, 6, 7, 9, 10 | 70 | High |
Nyam. S. S: Nyamitanga Secondary School; Shud. S. S: Shuhaddea Secondary School; Kisw: Kiswahili; Kise: Kisenyi; S. well: Shallow well; Nyam: Nyamitanga. Key to risks observed: 1 = Water source unprotected; 2 = Masonry protecting water source faulty; 3 = Backfill area eroded; 4 = Spilt water floods collection area; 5 = Perimeter fence absent; 6 = Animals have access within radius 10 m of water source; 7 = Pit-latrine uphill and/or within 30 m of water source; 8 = Surface water collects upstream of water source; 9 = Diversion ditch above water source absent/non-functional; 10 = Other pollution sources uphill of water source e.g., solid waste dumps, faeces, stagnant water, and drainage channels.
was no water source with a very high (81% to 100%) or no (0%) risk score. The common risks identified were access by animals within a radius 10 m of water source, presence of pit latrines within a radius of 30 metres from the water source, eroded backfill area, existence of pollution sources e.g. as solid wastes, lack of protective measures like fencing of the water source, and having diversion ditches. The risk assessment was not done for direct rainfall water which is not a groundwater source and thus it was assumed to have no eminent bacterial contamination source hence used as a control.
Sanitary risk assessment of the drinking water sources showed that shallow well at Nyamitanga and well in Kisenyi both had high bacterial contamination risk while springs at Kiswahili and Kisenyi had medium contamination risk. [
Total coliforms include bacteria which are found in the soil, water and animal or human wastes [
Mean total coliforms and E. coli counts significantly (p < 0.05) varied among the selected water sources.
The highest mean total coliform and E. coli counts were recorded in the shallow well at Nyamitanga i.e. S. well (Nyam.) followed by the well in Kisenyi i.e., Well (Kise). The spring in Kisenyi i.e. Spring (Kise) had the third highest E. coli counts while borehole in Nyamitanga secondary school i.e. Borehole (Nyam. S. S) recorded the third highest mean total coliform counts as detailed in
Boreholes in Nyamitanga and Shuhaddea secondary schools, well in Kisenyi and shallow well in Nyamitanga had mean total coliform bacterial count beyond the World Health Organization [
Water source (n = 10) | Borehole, Nyam. S. S | Borehole, Shud. S. S | Spring (Kisw) | Spring (Kise) | Well (Kise) | S. well (Nyam) | Rain, MUST | p-value (F test) | WHO (1993) standard | |
---|---|---|---|---|---|---|---|---|---|---|
Total coliforms (CFU/100 ml) | Range | 109 - 177 | 25 - 63 | 0 - 12 | 0 - 20 | 130 - 920 | 240 - 1600 | 0 - 5 | ||
Mean | 145.00 | 44.60 | 4.00 | 9.50 | 320.20 | 807.40 | 1.30 | 0.00 | 10 | |
SD | 23.71 | 11.29 | 4.32 | 6.74 | 239.56 | 579.23 | 1.64 | |||
% CV | 16.35 | 25.31 | 108.00 | 70.95 | 74.82 | 71.74 | 126.15 | |||
E. coli (CFU/100 ml) | Range | 0 - 0 | 0 - 6 | 0 - 7 | 0 - 12 | 2 - 25 | 11 - 43 | 0 - 0 | ||
Mean | 0.00 | 2.40 | 1.20 | 3.40 | 11.60 | 20.90 | 0.00 | 0.00 | 0 | |
SD | 0.00 | 2.41 | 2.57 | 4.20 | 6.28 | 10.62 | 0.00 | |||
% CV | 0.00 | 100.42 | 214.20 | 123.53 | 54.14 | 50.81 | 0.00 | |||
Proximity (m)* | Animal farms | - | 23 | - | - | 2 | - | |||
Latrine | 37 | 53 | 17 | 4 | 20 | 2 | ||||
Landfills | 12 | 33 | 58 | 11 | 12 | 7 | ||||
Municipal waste | - | - | 4 | - | 26 | - |
SD: standard deviation; % CV: percent of coefficient of variation; Nyam. S. S: Nyamitanga Secondary School; Shud. S. S: Shuhaddea Secondary School; Kisw: Kiswahili; Kise: Kisenyi; Nyam: Nyamitanga; S. well: Shallow well; MUST: Mbarara University of Science and Technology; -: represents no anthropogenic activity; * [
However, total coliform in the springs in Kiswahili and Kisenyi and the rainwater in Mbarara University of Science and Technology were below 10 CFU/100 ml. [
Borehole in Shuhaddea Secondary School springs in Kiswahili and Kisenyi, Shallow well in Nyamitanga and well in Kisenyi had E. coli beyond the World Health Organization [
Overall mean E. coli was the highest in Shallow well in Nyamitanga followed by well in Kisenyi (
The variations of the total coliforms and E. coli counts among the selected water sources are related to the bacterial contamination risks posed to the various water sources. Pearson correlation coefficient (n = 6) showed significant (p < 0.05) strong positive correlations between the sanitary risk scores for the groundwater sources and the mean total coliform and E. coli counts (r = 0.862, and r = 0.888, respectively). This significant strong positive correlation proved the reliability of the use of sanitary scores for preliminary risk assessment of contamination of water sources with faecal bacterial organisms. [
The proximity of the water sources to human and animal faecal sources as well as landfills [
The location of a latrine uphill within 10 m showed the greatest positive association with contamination in Mbale, Uganda [
Furthermore, sampling of the water in the present study was done between January to May 2016 which coincided with the rain season of Mbarara district and this could have accounted for the high total coliform and E. coli counts in some of the water sources. According to [
The relatively high mean total coliforms and E. coli in well at Kisenyi could also be attributed to the poor sanitation in Kisenyi due to its slum nature [
E. coli presence in springs in Kiswahili and Kisenyi and the borehole in Shuhaddea secondary school agrees with the findings of [
Rainwater from Mbarara University of Science and Technology which was collected from direct rainfall after an hour of downpour recorded no E. coli counts. This could mainly be attributed to improved hygiene in the university environment and hence no E. coli ended into surrounding atmosphere of the university with either soil or particulate matter. Additionally, the toilet facilities at the university are improved with no spills of faecal materials into the environment. Furthermore there were also no animal farms in the university compound. However the minute abundance of total coliforms in the rainwater could have emanated from windblown soil particles into the atmosphere. According to [
The correlation analysis (n = 70) indicated that total coliform and E. coli were significantly (p < 0.05) positively correlated with pH (r = 0.483, and r = 0.525, respectively), and negatively correlated with dissolved oxygen (DO) (r = −0.267, and r = −0.247, respectively). There was insignificant (p > 0.05) correlation of total coliform and E. coli with other physico-chemical parameters (temperature, biological oxygen demand, total hardness, electrical conductivity and total dissolved solids). Early studies have reported E. coli growth and replication to be influenced by physico-chemical parameters like pH and many others [
The significant positive correlation between E. coli abundance and pH is most likely due to the fact that E. coli survives well in environments with pH ranging between 5.5 and 8.5. Within this range increase in pH causes an increase in growth and replication of E. coli hence the positive correlation. [
The sanitary risk assessment score is a reliable tool for predicting the possible levels of bacterial contamination of drinking water sources in Mbarara municipality.
The results indicated that there is a strong linkage between microbiological (total coliforms and E. coli) water quality and water source sanitation, as well as the proximity of latrines, animal farms and landfills around the water sources.
All the studied groundwater sources (boreholes, springs and wells) in Mbarara Municipality were not compliant to either both or one of the WHO total coliform and E. coli criteria for drinking water hence they are unsuitable for drinking without treatment e.g. boiling etc.
Only rainwater collected from Mbarara University of Science and Technology met the WHO total coliform and E. coli criteria for drinking water thus is suitable for drinking without any treatment.
Mbarara municipal council should therefore ensure that pit latrines and animal farms are not located within WHO recommended minimum proximity of 30 m to the groundwater sources (boreholes, springs and wells).
Mbarara municipal council should also ensure effective and regular operation and maintenance of the drinking water sources through the adoption and promotion of appropriate Water Safety Plans.
The authors wish to thank the entire Department of Biology of Mbarara University of Science and Technology for the support and guidance they offered during the entire research and preparation of the paper.
Lukubye, B. and Andama, M. (2017) Bacterial Analysis of Selected Drinking Water Sources in Mbarara Municipality, Uganda. Journal of Water Re- source and Protection, 9, 999-1013. https://doi.org/10.4236/jwarp.2017.98066