| Summary: | 碩士 === 臺灣大學 === 環境衛生研究所 === 96 === Due to the requirement of 0.2 mg/L residual chlorine in the distribution systems, chlorination is the main disinfection method for waterworks in Taiwan. It has the advantages of low cost, effectiveness for inactivation of a wide range of pathogens, and a matured technology with extensive successful records. However, chlorination also produces disinfection by-products (DBPs) such as Trihalomethanes (THMs) and Haloacetic acids (HAAs), these DBPs could cause adverse health effects.
After treatment, the tap water was transported to the households through the drinking water distribution system. Due to the complex pipe lines and the long residence time in the distribution systems, the residual chlorine in finished water may degraded. Meanwhile, the microorganisms will regrowth and the biofilms will accrue on the pipe walls, this may cause further deterioration of finished water quality.
The objective of this research is to investigate the relationship among the concentrations of residual chlorine, the microorganisms and the disinfection by-product in distribution systems. The results will be helpful to elucidate the influence of residual chlorine on the microorganism regrowth and DBPs degradations in distribution systems.
The results indicated the residual chlorine was decreased gradually after its residence in the distribution system. In the meanwhile the microorganism grew again, the THMs concentration were increase and the HAAs were degraded due to the biodegradation. Besides, the biodegradation rates of HAAs decreased as the number of halogen atoms increased. In warmer water and in the absence of enough residual chlorine, a large portion of dihalogenated HAA species degraded due to biodegradation. However, the rates of biodegradation are lower for trihalogenated HAAs.
|
|---|
