ANALYSIS OF PUBLIC DRINKING WATER QUALITY ALONG WATER DISTRIBUTION SYSTEMS IN ADDIS ABABA CITY

Abstract

In this study, the impact of physical parameters and
disinfection on the availability of bacteria in treated water delivered to Addis
Ababa residents was assessed. Thirty-four water samples were purposively
collected from different points and physico-chemical and bacteriological
parameters were analyzed following standard methods. The results showed
that all physico-chemical parameters analyzed were in the standard ranges of
the World Health Organization (WHO) and Ethiopian National Standards
(ENS) whereas residual chlorine (0.2–0.7 mg/l) were not within the limit set
by WHO and ENS at a few sampling points. Regarding bacteriological
parameters, significant number of coliforms (TC (3–299 CFU/100 ml) and
FC (2–36 CFU/100 ml) and HPC (26–308 CFU/ml) were detected at all
sampling sites although residual chlorine was maintained. Moreover, HPC
was significant positive correlation with TC (r = 0.934 at P value of 0.01 and
r = 0.599, at P value of 0.05) and FC (r = 0.614 and a significant negative
correlation with RCl (r = -0.620 at P value and r = -0.792 both at P
value=0.01). On the other hand, TC and FC had a significant positive
correlation with each other (r = 0.643 and r = 0.811 both at P =0.01) and
significant negative correlation with RCl (r = -0.638 and r = -0.614) and (r = -
0.545 and r = -0.094), respectively. The study indicated that residual chlorine
in some sample sites might not be efficient in killing microbes and there
might be regrowth of microbes along the various distribution systems in the
supply lines.