Bacteria Detection in Drinking Water and Biofilm Samples of an Experimental Distribution Networks

In order to study the bacteria status in bulk water and biofilm and better understand the mechanism of second pollution in distribution networks, a pilot distribution networks was built. Different methods, such as heterotrophic plate counts (HPC), acidine orange direct count (AODC), direct viable counts-nalidixic acid (DVC-N.A.) and direct viable counts-5-cyano-2, 3-ditolyl tetrazolium chloride (DVC-CTC) were compared to get a practicable method to detect bacteria in drinking water. Growth status of biofilm on pipe wall was observed by electron microscope. API was used to identify representative bacteria in bulk water and biofilm samples. The results showed that direct viable counts method, such as DVC-N.A. and DVC-CTC could reflect the real state of bacteria in drinking water, and is more suitable for numerating viable bacteria in drinking water. Most bacterium in drinking water and biofilms samples identified by API are conditioned pathogens.