| Pollutants in drinking water sources and a series of harmful substances produced in water treatment process have seriously endangered human' s health,so more and more people paid attention to drinking water safety,in which disinfection by-products have also been widely concerned.Natural organic matter and bromide ion are important precursors of disinfection by-products,and coagulation is one of the best methods to control natural organic matter,so it's significant to study the effect of coagulation process on distribution of disinfection by-products and removal of their precursors.In this paper,polyaluminium chloride was used as coagulant,which is the most commonly used in China,to study effect of coagulation on the formation of chlorinated disinfection byproducts from different humus,effect of coagulation on the formation of brominated disinfection by-products in bromide-containing water,and effect of different natural organic compounds on the formation of disinfection by-products after coagulation.The results are instructive for controlling disinfection by-products by optimized coagulation.The results showed that humic acid was much more easily removed by coagulation than fulvic acid.With increase of PAC dosage,removal effect of coagulation on humus was increased first and then stabilized.For humic acid,removal rate of HAAFP/DOC was up to 53%and THMFP/DOC was up to 45%.There was less impact of coagulation on conventional DBPFP/DOC.Basically,there was no effect of coagulation on CHFP/DOC;dichloroacetonitrile is only from fluvic acid,and removal rate of DCANFP/DOC by coagulation was up to 24%.For bromide-containing water,with increase of bromine ion concentration in raw water,haloacetic acids,trihalomethanes,dihaloacetonitriles were transformed from chlorinated disinfection by-product to brominated,while haloacetic acid formation potential was reduced,trihalomethane and dihaloacetonitrile formation potential were increased.When bromine ion concentration in raw water reached 600 ?g/L,brominated disinfection by-products began to be dominated.After coagulation,for the three types of disinfection by-products,the total formation potential didn't change a lot with varying bromide ion concentration,but bromide incorporation factor was higher after coagulation,when bromide ion concentration reached 300 ?g/L,bromide incorporation factor increased most,and brominated disinfection by-products began to be dominated,but total bromine concentration of disinfection by-products was lower after coagulation.pH value of coagulation process had little effect on removal of disinfection byproducts for bromide-containing water.Effect of different natural organic compounds on the formation of disinfection by-products after coagulation was also studied.It was found that the higher humic acid concentration,the higher removal rates of DOC and SUVA.Different proportions of humic acid and fulvic acid always had positive effect on reduction of SUVA by coagulation,but this effect was not abvious on DOC.For disinfection by-products formation potential,different proportions of humic acid and fulvic acid can promote reduction of haloacetic acid formation potential by coagulation,but the effect on trihalomethane was not obvious. |
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