Study On The Chlorinated Disinfection By-products Of The Raw Water From Water Plants In Fuzhou

Currently, chlorination is the most widely used disinfection process of the water plants in China, which can guarantee the biological security of drinking water. However, various types of disinfection by-products(DBPs), most of which may lead to carcinogenesis, teratogenesis and mutagenesis, would be formed during the chlorination, and the danger to human health has caused widespread concern. The raw water of three main water plants of Fuzhou was selected as the study object, the change tendency of the formation potential of DBPs such as trihalomethanes, haloacetic acids and trichloroaldehyde with month was studied in this paper. Using the raw water of the Western Water Plant, the value of pH, temperature and the concentration of the chlorine on the formation of the trichloroaldehyde were discussed. In addition, the raw water of Southeast and the Eastern Water Plants was selected as the experimental water, the natural organic matters(NOM) was isolated and fractionated by using resin, and the formation potential of the trihalomethanes by chlorination were studied. The improvement measures were proposed for the water plants of Fuzhou in order to control the DBPs based on the previous research data and conclusions.The monthly concentration variation of the formation potential of DBPs showed as follows, the total trihalomethane formation potential (TTHMFP) of Western Water Plant was ranging from47.46μg/L(January) to95.11μg/L(May), the Eastern Water Plant was from43.93μg/L(December) to166.64μg/L(August) and the Southeast Water Plant was from8.69μg/L(April) to217.13μg/L(Septmber) respectively. The maximum value of the total haloacetic acids formation potential (THAAFP) of Western and Southeast Water Plants exist in January and December respectively, and the concentration were417.3ng/L and435.1μg/L respectively. The highest concentration of Eastern Water Plant appeared in August and the concentration was446μg/L. Dichloroacetic acid formation potential (DCAAFP) was generally higher than the trichloroacetic acid formation potential (TCAAFP).As the chlorination results shown, the highest concentration of trichloroaldehyde of both water from Western and Southeast Water Plants appeared on September and the concentrations were16.6μg/L,23.5μg/L respectively, which would exceed the limiting concentration of the drinking water standards. The water quality and the treatment process would influence the formation of the trichloroaldehyde. Trichloroaldehyde had the largest formation potential while pH in the neutral condition, higher or lower the temperature would not have benefit on the trichloroaldehyde formation. It was weak positive correlation with residual chlorine concentration.The HPIM took the main part of the DOC in the raw water of the Southeast and the Eastern Water Plants. In the Eastern Water Plant, the HPIM and the HPON took51.06%and28.18%, respectively. The main parts of the DOC of the Southeast Water Plant were HPIM and WHOA, and the percentage were44.50%and24.65%, respectively. As the results of the different composition chlorination experiment shown that the HPON had the highest trihalomethane formation potential, and the HPOA had the largest specific trihalomethane formation potential.The control suggestions of DBPs for the three typical water plants were given. It was recommended that, the chlorine point for chlorination before filtration in Western Water Plant might be moved ahead and another chlorination point might be added in the clear water tank in order to meet the requirement of residual chlorine of the standard, and the advanced treatment processes such as activated carbon adsorption would be built in the Eastern Water Plant in order to remove hydrophilic organic. The pre-chlorination process of Southeast Water Plant should synthetically considere the influence factors such as the value of ammonia nitrogen, residual chlorine concentration, climate and the temperature before implemented.