Factors affecting bacterial growth in drinking water distribution system.

OBJECTIVE To define the influence of some parameters, including assimilable organic carbon (AOC), chloramine residual, etc. on the bacterial growth in drinking water distribution systems. METHODS Three typical water treatment plants in a northern city (City T) of China and their corresponding distribution systems were investigated. Some parameters of the water samples, such as heterotrophic plate content (HPC), AOC, COD(Mn), TOC, and phosphate were measured. RESULTS The AOC in most water samples were more than 100 microg/L, or even more than 200 microg/L in some cases. The HPC in distribution systems increased significantly with the decrease of residual chlorine. When the residual chlorine was less than 0.1 mg/L, the magnitude order of HPC was 10(4) CFU/mL; when it was 0.5-0.7 mg/L, the HPC was about 500 CFU/mL. CONCLUSION For controlling the biostability of drinking water, the controlling of AOC and residual chlorine should be considered simultaneously. The influence of phosphors on the AOC tests of water is not significant. Phosphors may not be the limiting nutrient in the water distribution systems.