Study On The Characteristics Of Algal-nitrogenous Organic Matters And Its Formation Potential Of Disinfection By-products

Algal nitrogenous organic matters are important precursors of nitrogenous disinfection byproducts(N-DBPs)in effluent of drinking water plants.The increasingly serious eutrophication leads to an increase in the frequency of algal blooms,thereby increasing the content of nitrogenous organic matter in water bodies.The changes in the composition,structure and characteristics of algal organic matter during the outbreak and decline of algal bloom have an important impact on the N-DBPs formation.In this study,the cyanobacteria(Microcystis aeruginosa,Cylindrotheca)and green algae(Chlorella,Scenedesmus obliquus and Scenedesmus)commonly found in natural waters were used as the research objects to investigate their conditions in different habitats.The change rule of nitrogen-containing organic matter in algae source under different conditions(bloom outbreak conditions,nutrient deficiency,low temperature stress,hydrogen peroxide stress,etc.)was studied,and the effect of nitrogencontaining organic matter change in algae sourct on the formation of nitrogen-containing disinfection by-products was explored.The main research results are as follows:(1)Under the condition of algal bloom,algal species have significant influence on the characteristics of algal organic matter.Among the four typical blue and green algae,the dissolved extracellular organic matter(dEOM)of Cylindrotheca contained the most tryptophan,tyrosine protein substances and macromolecular organic nitrogen.The dEOM of Cylindrotheca also had the highest haloacetonitrile(HANs)generation potertial.The bound extracellular organic matter(bEOM)of Chlorella contains less fluorescent tryptophan,tyrosine protein substances and macromolecular organic nitrogen.The bEOM of Chlorella has the lowest HANs generation potential.The content of macromolecular organic nitrogen and the HANs generation potential in the dEOM of Microcystis aeruginosa the lowest.There were more fluorescent tryptophan,tyrosine protein substances and macromolecular organic nitrogen in the intracellular Organic Matter(IOM)of Scenedesmus,and its IOM had the highest generation potential of HANs.(2)During the vertical migration of algae,the characteristics of nitrogen-containing organic matter in algae changed under the synergistic effect of water temperature and light conditions.Microcystis aeruginosa and Scenedesmus obliquus had lower contents of small molecular organic nitrogen in the extracellular organic matter(EOM)when they were in the middle and bottom water bodies,and higher content in Scenedesmus obliquus.After the middle or bottom layer was restored to the surface water body,Microcystis aeruginosa exhibited a compensatory growth phenomenon.The macromolecular and small molecular organic nitrogen contents of its EOM were higher than those of the control group,and the small molecular organic nitrogen contents in the IOM were increased.Correspondingly,the production potential of haloacetamide(HAcAms)in EOM and IOM of Microcystis aeruginosa was also higher than that in the control group.(3)The lack of nitrogen and phosphorus nutrients will lead to the decrease of the content of small molecular organic nitrogen in the EOM of Microcystis aeruginosa.The greater the stress level,the less the release of dissolved organic nitrogen,and the lower the generation potential of HAcAms.The contents of macromolecular organic nitrogen in bEOM of Microcystis aeruginosa and Cylindrotheca were significantly increased under hydrogen peroxide stress.The corresponding production potential of HAcAms and haloacetic acid(HAAs)in bEOM of Microcystis aeruginosa and Cylindrotheca increased.Under low temperature conditions,Microcystis aeruginosa and Cylindrotheca were more affected by water temperature than Chlorella and Scenedesmus.The contents of macromolecular organic nitrogen and small molecular organic nitrogen in their dEOM and IOM increased,Correspondingly,the production potential of HAcAms and HAAs in Cylindrotheca dEOM and IOM increased significantly.