Research On Formation Of Disinfection Byproducts From Different Algal Organic Matters By Ozone And Activated Carbon Process

Taihu Lake is one of the most important drinking water sources in the Yangtze River Delta.In recent years,frequent human activities lead to more than a decade of cyanobacteria outbreaks,water quality deterioration and serious organic matters pollution.Thus,the harm caused by excessive algae can not be ignored.Chlorine disinfection is an effective measure to ensure water safety and prevent the spread of various infectious diseases.However,the residual organic matters in water can react with disinfectant to generate disinfection byproducts(DBPs).These DBPs have been proved to be carcinogenic,teratogenic and mutagenic to human's health.When algae bloom breaks out,algae would release a large amount of algae organic matter(AOM),including extracellular organic matter(EOM)and intracellular organic matter(IOM).Both EOM and IOM are important precursors of DBPs.In order to ensure the safety of drinking water,it is particularly important to do some researches related to the source of DBPs' precursors,occurrence and and control of DBPs.In this paper,the formation and the removal of DBPs during different drinking water treatment processes(including pre-ozonation,coagulatiion-sedimentation-sand filtration,post-ozonation,and biological activated carbon filtration)was studied.Moreover,the EOM and IOM of dominant algae species(Microcystis aeruginosa,Pseudanabaena sp.and Chlorella sp.)were selected as the precursors of DBPs.The formation of DBPs and impact factors by these EOM and IOM of three algae species after ozonation process and ozone combined with biological activated carbon advanced treatment process were investigated.The main conclusions were as follows:(1)The DBPs' precursors could be effectively removed after pre-ozonation process,conventional treatment process(coagulatiion-sedimentation-sand filtration)and ozone combined with biological activated carbon(O3-BAC)in a Drinking Water Treatment Plant of Taihu Lake.The removal efficiencies of Trihalomethanes(THMs)?Haloacetic acids(HAAs)?Haloacetonitriles(HANs)?Haloketones(HKs)?Chloral hydrate(CH)and Trichloronitromethane(TCNM)were 60.62%,36.64%,71.80%,70.55%,84.36%,and 93.75%,respectively.(2)The dosage of ozone,pH and bromine ion concentration had significant impacts on the formation of DBPs by EOM and IOM of three algae speices after ozonation process.The IOM of three algae species had greater formation potential of DBPs than EOM.Also,the EOM and IOM of Microcystis aeruginosa and Chlorella sp.showed greater formation potential of DBPs than that of Pseudanabaena sp..When the ozone dosage was 1.5 mg/L,the total amount of target DBPs generated by EOM and IOM of three algae species was the least after ozonation process.As pH was acidic,the total amount of target DBPs generated by EOM and IOM of three algae species was the least after ozonation process.The formation of Br-THMs increased with the increase of bromine ion concentration.(3)The filtration rate,pH and bromine ion concentration had significant impacts on the formation of DBPs by EOM and IOM of three algae speices after O3-BAC process.Slowing down the filtration rate and lowering the pH contributed to the reduction of formation of DBPs by EOM and IOM of three algae speices after O3-BAC process.The biological carbon filtration could effectively reduce the precursors of THMs of EOM and IOM of three algae speices.But it would not reduce the bromine substitution factor of THMs.