Microbial Community Structure and Diversity in Drinking Water Supply, Distribution Systems as Well as Household Point of Use Site in Addis Ababa City, Ethiopia
Authors: Atanfu Bayable , Desta Adey , Assefa Fassil 
Published: January 2021

Abstract
BackgroundUnderstanding ecology of microbiomes in drinking water distribution systems is the most important notion in delivering safe drinking water. Despite cultivation-based methods routinelyemployed in monitoring drinking water quality, cultivation of specific indicator organisms alone is not always guarantee for assuring safe drinking water delivery. The presence of complex microbiomes in drinking water distribution systems affects treatment effectiveness leading to poor quality water which as a result affects health of human and animals. Drinking water treatment and distribution systems harbor various microbiota despite efforts made in improving water infrastructures and several waterborne diseases become serious problems in the water industry, specially, in developing Countries. Intermittent water supply, long-time of water storage, low water pressure in distribution systems, storage tankers and pipes as well as contaminated source water are among many of the factors responsible for low drinking water quality which in turn affecting health of people. The aim of this study was to explore microbial diversity and structure in water samples collected from source water, treated water, reservoirs, and several household points of use locations (taps). High throughput Illumina sequencing technology was employed by targeting V4 region of 16S rRNA following Illumina protocol to analyze the community structure of bacteria. ResultsThe core dominating taxa were Proteobacteria followed by Firmicutes, Bacteroidetes and Actinobacteria. Gamma proteobacteria were dominant among other Proteobacterial classes across all sampling points. Opportunistic bacterial genera such as Pseudomonas, Legionella, Klebsiella, Escherichia, Actinobacteria, as well as eukaryotic microbes like Cryptosporidium, Hartmanella, Acanthamoeba, Aspergillus, and Candida were also the abundant taxa found alongthe distribution systems. The shift in microbial community structure from source to point of uselocations were influenced by factors such as residual free chlorine, intermittent water supply andlong-time storage at the household. The shift in microbial community structure from source to point of use locations were influenced by factors such as residual free chlorine, intermittent water supply and long-time storage at the household.ConclusionsThe complex microbiota which was present in different sample sites receiving treated water from the two treatment plants (Legedadi and Gefersa) starting from source water to household point of consumption across the distribution systems in Addis Ababa brings drinking water quality problem which further causes significant health problems to both human and animal health. Treatment ineffectiveness, disinfection inefficiency, poor maintenance actions, leakage of sewage and other domestic wastes are few among many other factors responsible for degraded drinking water quality in this study putting health at high risk which, this, leads to morbidity and mortality. Findings of this research provide important and bassline information to understand the microbial profiles of drinking water along source water and distribution systems.