Effect of Pre-chlorination on Algae as Precursors for Disinfection By-products
Date Issued
2006
Date
2006
Author(s)
Chiu, Chao-An
DOI
zh-TW
Abstract
Water treatment plants generally use chlorine as disinfectant to ensure the safety and health of drinking water. Besides, chlorine is also used as pre-oxidant when there is high level of organic matter in raw water, called pre-chlorination. Pre-chlorination could decompose a part of contaminants, like ammonia nitrogen and TOC, to alleviate the load of treatment units and diminish the operation cost of waterworks .It is a common process of water treatment in Taiwan.
However, pre-chlorination might bring certain problems when dealing with anthropogenic pollutants. Reactions between pre-chlorination and algae from eutrophic water would increase the content of precursors of disinfection by-products (DBPs) in treated water and raise the risk of public health hazard.
This study focus on the effects after pre-chlorination and the fate of algal cells and extracellular products (ECPs) in water treatment processes. Various kinds of simulation water samples with Microcystis aeruginosa (a species of blue-green algae) were used to proceed water treatment processes, including coagulation, flocuulation, settling, and filtration. Besides pre-chlorination, the contribution of cells and ECPs as DBPs precursors, cultivating temperature, competition between Br- and Cl-, formation of trihalomethanes(THMs) and haloacetic acids(HAAs) would also be discussed in the study.
The results show that the oxidation of pre-chlorination did increase the content of DBPs precursors in treated water after filtration. These precursors were released into water because the breaking of algae cells. According to some literatures, many extracellular and intracellular products of Microcystis aeruginosa belong to aliphatic precursors so that Br- would increase the DBPs formation for 1~2 times. The aliphatic precursors tended to form Br-DBPs because of steric hindrance limit. Moreover, the algae cultivated in low temperature condition could resist the oxidation of pre-chlorination and release less precursors into water.
Furthermore, this study also collected the raw water from two water treatment plants in Kinmen to proceed the water treatment processes. The results of DBPs analysis could not be inferred by the outcome from simulating experiments because the concentration of non-algal organic matter was too high. However, the treated water with pre-chlorination process revealed higher DBPs concentration than that one without pre-chlorination process, in both two plants.
Subjects
前加氯
優養化
銅綠微囊藻
連續型培養
消毒副產物
Pre-chlorination
Eutrophication
Microcystis aeruginosa
Chemostat
Disinfection by-products
Type
thesis
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