Research On Removal Of Disinfection Byproducts Precursors By Ozone-biological Activated Carbon Process

Huaihe River Watershed as water source waterhas faced many problems in recent years,such as increase of trace organic pollutants,seasonal algae outbreaks,and excessive odorous substancescaused by algae metabolism,which leads to increase of disinfection by-products precursors and the need to optimize the water treatment process to remove disinfection by-product precursors,reduce disinfection byproducts result from disinfection process,toensure safety of drinking water quality.In this paper,removal characteristics of the precursors of disinfection by-products were studied by using the ozone-biological activated carbon process(O3-BAC)of Tongyu River and Yanlong Lake(water source from MangsheRiver)as raw water.Based on the analysis of raw water quality,this paper studied the removal of pollutants by different pretreatment methods and the optimized operation of ozone-biologically active carbon units for pollutants removal.Main conclusions were as followed:Main pollutants of Tongyu River,Yanlong Lake and Mangshe River were permanganate index and ammonia nitrogen,and the permanganate index of three water sources was more than 4mg/L.Range of ammonia nitrogen in MangsheRiver,Yanlong Lake and Tongyu River was 0.18-1.02mg/L,0.17-0.36mg/L and 0.30-1.5mg/L respectively,and concentration of ammonia nitrogen would increase in summer,exceeding the surface water environmental quality standard II type of water requirements of 0.5mg/L,indicating that the source of water belonged to the micro-polluted water.Geosmin(GSM)and 2-methyli-sobomeol(2-MIB)in the three water sources were investigated.Results showed that in addition to the high concentration of GSM in Tongyu River(reaching 17ng/L)in March,In the other months,the concentrations of 2-MIB in the three water sources were fluctuating(3-9ng/L),and the concentrations of 2-MIB in the Yanlong Lakeincreased to 115ng/L,123ng/L,155ng/L.Proportion of trichloromethane formation potential(TCMFP)in raw water was the highest among total trihalomethanes formation potential(THMFP),and the fluctuation range of TCMFP was between 58.58 and 295.11?g/L.The proportion of trichloroacetic acid formation potential TCAAFP was the highest in the total haloacetic acid formation potential(HAAFP),and the range of TCAAFP fluctuated between 28.75-333.45?g/L.Removal efficiency of turbidity,UV254,CODMn and TOC was betterbothby the sand filter and bio-enhanced filter column,however,the removal of ammonia nitrogen efficiency was not high,and the removal efficiency of ammonia nitrogen was 49.2%and 53.5%respectively.Removal efficiency of TCMFP?BDCMFP in the THMFP and MCAAFP in the HAAFP had a certain removal efficiency by two columns,while there was almost no effect onthe other several disinfection by-product precursors.Biological contact oxidation tank selection(1-1.2):1 gas to water ratio can achieve better ammonianitrogen removal rate underthe premise of low energy consumption.Biological contact oxidation tank + conventional treatment process had a certain removal effect onTCMFP,BDCMFP in THMFP and DCAAFP,TCAAFP in HAAFP,however,there was almost no effect on DBCMFP in THMFP and MCAAFP,MBAAFP,DBAAFP in HAAFP,even lead to the increase of TBMFP concentration.Optimal pre-ozone dosage was 1 mg/L,and removal rate of pollutant CODMn was the highest,reaching 59.7%,60.10%respectively by pre-ozonation +conventional process(sand filter and bio-enhanced filter column).The cumulative removal rates of THMFP were 54.01%,57.7%,and HAAFP were 73.06%,76.69%respectively by two columns.Optimal post ozone unit ozone dosage was 2mg/L and ozone contact residence time was 60min.Removal efficiency of TCMFP,BDCMFP,CDBMFP in THMFP,and MBAAFP,TCAAFP in HAAFP was better,there was almost no effect on DBCMFP in THMFP and MCAAFP,MBAAFP,DBAAFP in HAAFP,and removal rate of THMFP,HAAFP was 59.56%,43.81%respectively.Optimal filtration rate of CODMnremoval was 4.24m/h,and removal efficiency of TCMFP,BDCMFP in THMFP and DCAAFP,TCAAFP in HAAFP was the better.There was no removal effect on DBCMFP in THMFP and MCAAFP,MBAAFP,DBAAFP in HAAFP,and THMFP,HAAFP was 45.3%and 41.3%respectively.In contrast to the removal of disinfection by-products precursors in the above water treatment processes,O3-BAC can effectively remove the precursors of disinfection by-products,decrease generation of disinfection by-product,to endure the safety of drinking water quality.