| Summary: | 碩士 === 國立屏東科技大學 === 環境工程與科學系 === 94 === The eastern water supply plants in Taiwan mostly located near coastal area. The bromide (Br-) in water directly affects the formation of disinfection by-products (DBPs) with the addition of chlorine for disinfection process. The primary compound is brominated THMs. Total trihalomethanes (TTHMs) will exceed the standard of drinking water quality due to the effects of bromide, humic acid, water temperature, pH, reaction time, etc. Therefore this study is going to establish an index based on bromide to forecast and to control the amount of THMs’ production.
The objective of this research is to study the bromide concentration on the variation of THM’s production and to establish the curves predicting the production pattern of brominated THM’s under different operation conditions such as concentration of humic acid (0.5～6.0 mg/L), reaction time (0～26 hrs), pH (4～9) and water temperature (5～35℃).
The background concentrations of Br- and humic acid in the raw water and purified water of treatment plants located in eastern coast of Taiwan were surveyed first. Then the model solutions of various concentrations of Br- and humic acid were prepared to study effects of reaction time, water temperature, pH on the production of THMs. Furthermore the tables and diagrams based on the effects of operation parameters on THMs’ production were generated.
The results from the tables of THMs’ largest production showed that bromodichloromethane (CHCl2Br) decreased with the increase of Br-. The Br- concentration at the reflection points were 0.3 mg/L and 0.3 ~ 0.5 mg/L for bromodichloromethane and dibromochloromethane, respectively. Bromoform (CHBr3) increased while chloroform (CHCl3) decreased with the increase of bromide (Br-). Chloroform was not detected when the concentration of bromide (Br-) was greater than 1.0 mg/L.
The results of simulation of season’s variation with water temperatures showed that the amounts of THMs’ production increased approximately 3.33% with 1℃ increase of the water temperature that fairly matched the analytical data of TTHMs in water collected from the treatment plants. The reaction time for maximum amount of TTHMs’ production was 12 hours. The amounts of TTHMs increased with the concentration of humic acid but not significantly influenced by pH because the pH of drinking water is between 7.0～8.5.
The concentration ranges of forecast curves of maximum TTHMs’ production established in this research were 0.10 to 1.00 mg/L for bromide (Br-), 0.50 to 6.00 mg/L for humic acid, respectively. Other operational parameters were as followed: chlorine addition was less than 2.2mg/L, water temperature was controlled at 25℃and reaction time was set at 12 hours.
Keywords: Bromide (Br-), total trihalomethanes (TTHMs), bromoform (CHBr3), humic acid (HA), chloroform(CHCl3)
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