Study on Bacteria in Water and Biofilm of a Pilot Distribution Networks

In order to study the bacteria status in 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. PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) was applied to reveal bacteria diversity in 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. Bacteria diversity showed by PCR-DGGE indicated even at the same sampling time there are more kinds of bacteria in biofilm sample than in water sample.