A microbiological and parasitological study of drinking water from point-of-use taps and wastewater from adjacent open ditches in Addis Ketema and Akaki/Kality sub-cities, Addis Ababa, Ethiopia

Abstract

Wastewater drained through open ditches poses a threat of contamination to households and drinking water distribution lines. This study assessed the bacterial and parasite load of drinking water and wastewater. A total of 205 drinking water and wastewater samples were aseptically collected from three woredas each of Addis Ketema and Akaki/Kality sub-citiesand analyzed for enteric pathogens, total aerobic mesophilic bacteria, enterobacteria, total coliforms,and protozoan and helminth parasites using standard microbiological and parasitological techniques. Wastewater samples from both sub-cities had mean counts of aerobic mesophilic bacteria, enterobacteria and total coliforms above log 6 cfu/ml (CV, <10%). Counts of enterobacteria and total coliform from drinking water in both sub-cities were beyond permissible levels (>log 2 cfu/ml). Mean counts (log cfu/ml) of aerobic mesophilic bacteria, enterobacteria, and coliforms in drinking water showed significant difference at P=0.013 (CI: -0.82722, 0.27937); P<0.001 (CI: -1.797, -3.358) and P<0.001 (CI: -2.289, -0.759] between the two sub-cities, respectively. From surface wastewater samples, only the total coliform counts showed a significant difference with p=0.008 (-1.149, 0.003), however, there was no significant difference in mean counts of aerobic mesophilic bacteria p=0.764 (-0.022, 0.434) and enterobacteria 0.115 (-0.311, 0.363) between sub-cities.  No Salmonella or Shigella were encountered.Various non-lactose fermenting Gram negative bacteria, mainly diminated by Proteus Spp., Pseudomonas aeruginosa,  and Alcaligenes faecalis were isolated from wastewater in both sub-cities. Protozoan and helminth parasites in wastewater and drinking water samples were mainly dominated by Giardia lamblia, Taenia spp, and Ascaris lumbricoides. In conclusion, drinking water in the study sub-cities was contaminated with various opportunistic pathogens and disease causing parasites. Thus, households in the study sub-cities should treat drinking water before consumption. Responsible authorities should check the integrity of drinking water distribution lines periodically.