Study On The Removal Characteristics Of Algal Disinfection By-product Precursors By UV/persulfate

In recent years,with the development of industry and agriculture,the discharge of waste water increases,different degrees of eutrophication have appeared in lakes,reservoirs and other water sources,phytoplankton such as algae proliferate in the water,and algae metabolism produces a large number of algal derived organic matter(AOM).AOM produces disinfection by-products(DBPs)in the disinfection process,which threatens the safety of human drinking water,removing AOM from water becomes an urgent problem to be solved.In this thesis,the degradation of DBPS precursors in AOM was studied by ultraviolet/persulfate(UV/PS)advanced oxidation technology.First compares the verdigris microcystin algae,red algae blooms fish and chlorella DBPs formation ability,the results show that verdigris microcystin algae DBPs formation ability is stronger,and then studied the patina of algae AOM of molecular weight and feeling of water-based and DBPs formation characteristics of each part,the results show that verdigris microcystin algae AOM is given priority to with small molecular weight and hydrophilic components,<1kDa small molecular components and hydrophobic components of Chloromethane formation potential(TCMFP),dichloroacetic acid formation potential(DCAAFP)and dichloroacetonitrile formation potential(DCANFP)were larger.AOM contains fulvic acid,humic acid,fluorescent protein I,fluorescent protein Ⅱ and soluble microbial degradation products.The hydrophilic,transitional hydrophilic and hydrophobic components all contain fulvic acid,humic acid and soluble microbial degradation products,and the hydrophobic components also contain more fluorescent protein Ⅰ,fluorescent protein Ⅱ.Then the effect of Br-concentration and DOC concentration on DBPS generation was studied.It was found that adding Br-to AOM could generate more brominated disinfection by-products(Br-DBPs)in the chlorination process.The yield of DBPS increased with the increase of Br-concentration and DOC concentration.The degradation effects of UV,PS and UV/PS combined processes on DBPS precursors from algae were compared.The results showed that although UV and PS alone had a certain degradation effect on DBPS precursors,they were not as good as UV/PS process.When the UV dose was 800 mJ/cm2 and the PS dosage was 5mmol/L,the removal rates of TCMFP,DCAAFP and DCANFP of AOM reached 34.7%,74.6%and 86.6%.BBD response surface method was used to model the removal rates of TCMFP and DCANFP by AOM concentration,PS dosage and UV dose.DCANFP and TCMFP removal rate models were well fitted.The optimal removal conditions of DCANFP were as follows:AOM concentration lmg/L,PS dosage 5mmol/L,UV dose 772.07 mJ/cm2.The optimal removal conditions of TCMFP were as follows:AOM concentration lmg/L,PS dosage 5mmol/L,UV dose 800mJ/cm2.The degradation effects of UV/H2O2 and UV/PS on reservoir water were compared.When the dosage of H2O2 and PS was 0.294mmol/L,the degradation effect of UV/PS was obviously better.The results showed that Cl-,NO3-and HCO3-had certain inhibitory effects on the degradation of AOM by UV/PS,which resulted in the increase of TCMFP,DCAAFP and DCANFP.The degradation of AOM by UV/PS under acidic and neutral conditions is better than that under alkaline conditions.Comparing the changes of different molecular weight components of AOM before and after the reaction,it can be seen that the degradation ability of UV/PS to macromolecular components is stronger,but the degradation ability to small molecules is weaker.By comparing the hydrophilic and hydrophobic components of AOM before and after the reaction,UV/PS had the best degradation effect on hydrophobic components.Three-dimensional fluorescence analysis showed that the contents of fulvic acid,humic acid,fluorescent protein Ⅰ,fluorescent protein Ⅱ and soluble microbial degradation products in AOM decreased after the reaction.When PS dosage was 3mmol/L and UV dosage was 800mJ/cm2,only soluble microbial degradation products were left in AOM.LC-OCD analysis showed that biopolymers were the main components in AOM.After UV/PS degradation,biopolymers and humic acids with higher molecular weight in AOM would be converted into humic acid degradation products and low molecular neutral organic compounds.