Effects of chlorine level on the growth of biofilm in drinking water pipes

Abstract

Three analogous laboratory-scale water pipe systems were constructed to study the effects of three chlorine levels of finished water on the growth of biofilm. The experimental results indicated that the heterotrophic plate counts (HPCs) of biofilm for chlorine-free water were approximately 2 and 3 orders of magnitude higher than those for low-chlorine water (0.3-0.5 mg/l Cl2) and high-chlorine water (1.2-1.5 mg/l Cl2), respectively. The difference in HPCs between low-chlorine water and high-chlorine water was below 1 order. Average biofilm formation rates are 325 ATP pg/cm2 per day for chlorine-free water, 159 ATP pg/cm2 per day for low-chlorine water and 118 ATP pg/cm2 per day for high-chlorine water. Scanning electron microscope (SEM) observation showed that bacterial species separated from the biofilm were more complex than from the finished water. The Gram-negative bacteria were dominant.

Persistence and Decontamination of Bacillus atrophaeus subsp. globigii Spores on Corroded Iron in a Model Drinking Water System

“…Even if pathogen density in the water column were low enough that infection of consumers did not occur, uncertainty surrounding the fate of injected pathogens present in the pipe material and biofilm would assuredly reduce the number of people utilizing municipal potable water. Therefore, understanding how long allochthonous pathogens survive in biofilm and/or pipe material under oligotrophic drinking water conditions, and decontamination of that material, is an important research topic.It is well known that biofilm-associated microorganisms survive longer in the presence of disinfectants than planktonic organisms (8,(20)(21)(22)34). However, information on persistence of microbiological agents in water distribution system pipe material is limited.…”

“…It is well known that biofilm-associated microorganisms survive longer in the presence of disinfectants than planktonic organisms (8,(20)(21)(22)34). However, information on persistence of microbiological agents in water distribution system pipe material is limited.…”

Review of chloramine decay models in drinking water system

“…114 It has been found that bacteria grown on iron pipe surface is more resistant to free chlorine compared to that grown in PVC, copper or galvanized surfaces. 33,115 The pipe materials leaching into water through corrosion can also significantly affect the chloramine decay. The effect of pipe materials on chloramine decay largely depends on the water quality and corrosion intensity.…”