Bacteriological and physicochemical quality of drinking water in Kobo town , Northern Ethiopia

Despite drinking water supply in Kobo town is from a borehole through pipes, a high incidence of waterborne diseases are frequently reported. Hence, this study aimed to assess the bacteriological and physicochemical drinking water quality in Kobo town. One hundred and twenty water samples were collected from four sampling sites (the source, reservoir, taps, and households’ containers) from February to April 2020. Total and fecal coliforms were counted from the water samples using membrane filtration while selected physicochemical parameters were determined using standard methods. The mean counts of total and fecal coliforms ranged from 3.9 to 22.9 and 1 to 13.6 CFU/100 mL, respectively. Hence, all water samples did not satisfy the WHO guidelines and national standards. There were statistically significant differences in the coliform counts between the different sampling sites, and the counts were significantly higher in the taps and households’ containers compared to the counts in the source and reservoir (p< 0.05). All physicochemical parameters, except for temperature, were within the recommended acceptable limits. High coliform count in the water system demands proper maintenance of the distribution line and good hygiene practices at household level to improve the microbiological quality of drinking water in Kobo town.


INTRODUCTION
Delivering adequate and potable water to all citizens is among the top priorities of governments in all nations. Scientific information about drinking water quality from different settings is vital in tackling water-related problems.
The two principal activities in water quality assessment are observational techniques (sanitary survey and qualitative visual inspection) and water quality analysis (both biological and physicochemical). If carefully applied, sanitary inspection (SI) tools well complement water quality test results for a comprehensive management of drinking water systems (Kelly et al. ). SI helps identify potential risks, provide information on possible causes of both past and future pollution and actions necessary to manage future water quality. Bacterial pathogens are commonly used biological parameters, and selected physicochemical parameters can be included depending on the specific objective of a study.
While the number of different pathogens can be large in a contaminated water sample, load of pathogens from fecal contamination is usually too small to detect. It is, therefore, difficult and even unsafe to test for pathogens in a large number of water samples. Alternatively, pathogens can be quantified indirectly by testing for an 'indicator' organism such as coliform bacteria. The quantification of coliform bacteria has thus been serving as indirect evidence for quantitatively estimating pathogenic bacteria in drinking water samples (Bartram & Balance ; WHO b).
Coliform bacteria originate from the same sources as pathogenic bacteria do. They are relatively easy to identify, are usually present in larger numbers than the pathogens, and respond to the environment and water treatment similarly to many pathogens (Bartram & Balance ). As a result, counting coliform bacteria has been a standard method to estimate the load of pathogenic bacteria in a sample. Total coliforms include bacteria that are found in the soil as well as in human or animal waste. Fecal coliforms, on the other hand, are members of the total coliforms that are considered to be present specifically in the gut and feces of warm-blooded animals. Because the origins of fecal coliforms are more specific than the origins of the more general total coliform group of bacteria, they are considered a more accurate indication of animal or human waste than the total coliforms. World Health Organization (WHO) guidelines as well as Ethiopian standards for drinking water quality do not allow any detection of coliforms in 100 mL of drinking water. Even though a high count of total coliforms may not directly indicate pathogenic bacteria contamination, this at least shows that chlorination has not been properly done, which in turn, could lead to bacterial contamination of drinking water. However, a high count of fecal coliforms is direct evidence for fecal contamination (WHO b).
Several studies on the bacteriological quality of drinking water have been conducted in many locations in Ethiopia. () reported that 82.1-86.8% of drinking water in Wogera town was contaminated with fecal coliforms. However, no study has ever been conducted in the Kobo area.
The majority of the population in Kobo town (7,000 of 85,000 households) obtains drinking water from a borehole through pipes. The remaining 1,500 households obtain drinking water directly from another well by hand pumping.
According to official reports from the health sector of the town, water-associated diseases were among the top ten causes of illness in the community. For instance, 5,864 people in 2017 and 6,037 people in 2018 were sick from waterborne diseases such as diarrhea, amoebiasis, or other intestinal bacterial pathogens. The recent quarterly report (from July to September 2019) showed that 1,620 children under the age of five were affected by waterborne diseases.
The overall aim of this study was thus to gain insight into the possible health risks due to drinking water quality deterioration in Kobo town, with the following specific objectives: water quality evaluation against guidelines and standards and assessment of possible risks based on sanitary surveys.

Study area description
This study was conducted in Kobo town, Kobo district, northeast Ethiopia (Figure 1). This town is situated some 570 km northeast of Addis Ababa, the capital city of Ethiopia. The

Study design
A cross-sectional study was conducted to evaluate the microbiological and physicochemical quality of drinking water in Kobo town from February to April 2020. Four out of five kebeles (the smallest administration level), which obtained tap water piped from the borehole, were included in the study. One kebele was excluded from the study as it was located a little farther from the others and the residents used hand dug well water for drinking. Before sample collection for water quality analysis, sanitary assessment was conducted at the source, reservoir and 364 households, which were selected through systematic random sampling technique. Next, 30 households who used taps were selected (sub-sampled) again through systematic random sampling technique. Then, water samples from the source, reservoir, and the 30 households (both from their taps and water containers) were collected for bacteriological and physicochemical analyses.
Sanitary assessment of drinking water from source to the household level Prior to water quality analysis, assessment of the sanitary status of the drinking water source, reservoir, and distribution lines was carried out through visual inspection following recommendations in WHO/UNICEF ().
Structured questionnaires were used to obtain information on the sanitary condition at the household level that may affect drinking water quality. The questionnaires were first developed in English and translated into Amharic (a local language) and then the responses were translated back into English. Three hundred and sixty-four households, including the 30 households chosen for water quality analyses, were selected through systematic random technique from four kebeles in the study area for the preliminary assessment of the risk factors for water contamination.
The sample size (n ¼ 364) was determined using single population proportion formula for cross-sectional surveys (i.e., n ¼ z 2 p(1 À p) Bacteriological quality analysis of the water samples Coliform count was performed using membrane filtration technique following procedures described in APHA ().
The absorbent pads were aseptically placed into Petri plates and saturated with Lauryl Sulphate Broth (HiMedia). A 100-mL water sample was filtered through a 0.45-μm membrane filter (HACH company), and the filter papers were put onto the absorbent pad. The plates were then incubated at 37 C and 44 C for 24 hours for total coliforms and thermotolerant coliform count, respectively. After 24 hours of incubation, colonies with yellow color were counted and recorded.

Determination of physicochemical parameters
Basic physiochemical parameters in the water samples were measured following standard methods described in APHA (). Temperature (using Bio abron student mercury thermometer), pH (using Wagtech pH meter, model CP 1000 Singapore), turbidity (using Wagtech turbidity meter model Wag-WT 302, Singapore) and conductivity (using TDS/Conductivity meter, Wagtech 534000, Singapore) were measured in situ. Residual chlorine and nitrite were determined by photometric methods using Palintest Photometer 7100 (Wagtech, Thatcham, UK).

Data analysis
Data were analyzed using SPSS statistical software (version 23  (Table 2). Generally, mean pH, temperature, turbidity, and nitrite showed an increasing pattern from Thirty out of the 364 households were selected for water quality analysis, and to find out the association between the risk factors listed in Supplementary Material data 3 with the level of water contamination. However, the association using chi-square test was not analyzed, because the expected value of the number of sample observations in each level of the variable was less than 5. As a result, only description statistics were employed.
Most of the respondents (86.7%) from the 30 households were females; between 41 and 60 years old (86.7%); cannot WHO guidelines or Ethiopian standards are for pH 6.5-8.5, temperature 15, turbidity 5, conductivity 1,000, and nitrite 3.  Generally, drinking water at the household level (both in taps and water containers) were found to be highly contaminated with coliforms compared to the source and the reservoir (Table 1). This result is in agreement with previous reports from Boloso Sore District in southern Ethiopia  In this study, high coliform counts in the water system can also be accounted for by the inadequate chlorination ( hold level were more contaminated compared to that of the source. In addition, drinking water at the household level was found to be more contaminated by coliforms compared to water from taps due to poor sanitation and hygienic practice (Tabor et al. ).

Physicochemical quality of drinking water in Kobo town
Generally, the Kobo town drinking water system can be considered safe with regard to the documented physicochemical water quality parameters. However, the temperature of drinking water samples was higher than the permissible limit, and this can be conducive for the proliferation of aerobic mesophilic bacteria, and in turn, may contribute to the high microbial count observed. In fact, in several studies elsewhere in Ethiopia, temperature records have been where pollution level was very low. This could mean that it might not be due to some problem related to water pollution or might not produce a serious problem by itself.
Rather, the temperature limit value in the tropics may need a revision.

CONCLUSIONS
Microbial drinking water quality in Kobo town fails to comply with WHO guidelines and national standards. The presence of the high counts of the coliform bacteria observed suggested that the drinking water pollution in Kobo town is likely a threat to public health. This study also confirmed that there were poor sanitation and water handling practices in the community. The most probable risk factors for water quality deterioration include unhygienic water handling practices at the household level and poor environmental conditions around the source, reservoir, and distribution line. The town administration, health and water offices should take immediate actions including preventing human activities and waste disposal around the water source and the reservoir, as well as regular inspection and maintenance of the distribution lines. In addition, educational campaigns on environmental sanitation and hygienic practices are of paramount importance in raising public awareness in Kobo town, thereby reducing the impact of water-related health burdens among the community.