Abstract:
Globally, at least 2 billion people are forced to use drinking water source contaminated with
faeces. Drinking Water Distribution System (DWDS) function as microbiological and physicochemical
reactors which interact with drinking water and, in turn, impact upon the quality of
water supplied to customers. The presence of biofilms in the drinking water distribution system
may play a role in the presence of potential pathogens in drinking water supply. Biofilm in
DWDS causes fouling of filtration membranes, impairs taste, degrade quality of drinking water
and transmits harmful pathogens. Disinfection along with filtration helps to remove pathogens
and suspended particles. The water filtration plants have different stages with varying media
and pore size to remove all insoluble suspended particles and organic substances as well as
taste and odor. The UV sterilizer in the last stage, sterilizes water by scrambling microbial
DNA, thus provides absolutely safe water for drinking and cooking. The aim of this study was
to monitor the changes in physicochemical and biofilms related to pre and post filtration plants
by evaluating polyvinyl chloride (PVC) pipe coupons. The physicochemical and microbial
parameters of drinking water in pre and post filtration plants were evaluated in this research.
Water samples were collected from water tanks and filtration plants of NUST to monitor the
microbial parameters following standard protocols for coliforms, E. coli and total viable count
at 37 °C. The heterotrophic plate counts were determined for both the planktonic and biofilm
phases of water samples. Scanning Electron Microscopy (SEM) images were captured to
evaluate the surface topography of biofilm formed in the pre and post filtration plants and
revealed that structure of biofilm alters drastically after passing through filtration process. A total of 16 strains of bacteria were isolated from 15 sampling points employing biochemical and morphological tests.
