Study On The Efficiency Of Coagulation To Remove Algae-derived Organic Matter And Disinfection By-product Precursors

With the development of industry and the progress of human life,a large number of pollutants are discharged into water bodies,which can easily cause algae blooms.The outbreak of algae will release a large amount of organic matter,which contains a large amount of precursors of disinfection by-products,which harms clean water.Water supply is safe.As a common pre-treatment technology for water purification,coagulation is currently widely used to remove algae and algae-derived organic matter(AOM)from water.The changes of physical and chemical characteristics of algae and AOM under different growth periods have an important influence on the algae removal effect.The thesis takes algae and algae-derived organics as the research objects,explores and compares the growth characteristics of Anabaena algae and Chlorella,and investigates the effectiveness of coagulation to remove Anabaena algae and the precursors of disinfection by-products.The mechanism of coagulation and the characteristics of algae-derived organic matter and its disinfectant by-product precursors.The main research contents and results are as follows:The characteristics of algae-derived intracellular organic matter(IOM)and extracellular organic matter(EOM)organic matter at different growth stages of Chlorella vulgaris and Anabaena sp.Were compared and analyzed.Trihalomethanes and NDMA were selected Representative carbon-nitrogen disinfection by-products were studied for the production of two algae.Compared with Chlorella vulgaris,Anthracnose blooms have a higher production of trihalomethanes and NDMA disinfection by-products,and with the increase of time,the unit production contribution gradually increases.Furthermore,after comparison,the IOM trihalomethanes and NDMA disinfection by-products of Anabaena algae contributed the most,which were 43.2 ?g / mg DOC and 120.5 ng NDMA / mg DOC,respectively.The blue-green algae Anabaena has higher hazards than the green algae Chlorella.The investigation and analysis of the three coagulants(PACl,Fe Cl3,Al2(SO4)3)on the removal effect of the blooming Anabaena at different growth stages and the effect of different p H conditions on the removal effect were compared.Commonly used coagulant on the removal of precursors of algae-derived trihalomethanes and NDMA disinfection by-products.Among them,the removal effect of PACl is the best,and the removal rates of OD685,DOC,UV254 and chlorophyll a can reach 95%,51.9%,59.8% and 82.8%,respectively.Al2(SO4)3 is obviously affected when the p H changes.When the p H drops to 5,the maximum removal rate during the decay period drops by about 22.4%.The removal effect of PACl on the precursors of trihalomethanes and NDMA disinfectant by-products of Anabaena is relatively best,and the removal rate of NDMA precursors can be up to 29.2%.The use of PACl as a coagulant has a certain effect on the pretreatment process of Anabaena algae and its disinfection by-product precursors,which can deal with the pressure of the subsequent process to a certain extent.Through analysis and research,we explored the AOM removal effect of Anabaena sp.At different growth stages.Among them,PACl removes EOM poorly,the average removal rate is only 26.4%,and the removal effect of IOM and EOM + IOM is relatively good,and the removal rate is increased by 19.2% and 34.6%,respectively.PACl has the best removal effect in the three-stage stationary phase,with an average removal rate of 37.3%.The removal effect of PACl on the formation potential of IOM chloroform is better,the three-stage removal rate is 54.2%,60.9% and 50.4%,while the removal effect of dichlorobromomethane and NDMA precursors is relatively poor,only about 30% But there is basically no removal effect on the precursor of dibromochloromethane.The mechanism analysis shows that the AOM of Anabaena algae in the exponential phase and the stable phase is dominated by electrical neutralization,and the AOM of Anabaena algae in the decay phase is mainly net catching and sweeping.With the same molecular weight distribution and three-dimensional fluorescence analysis,EOM and IOM mainly consist of <3K Da and> 10 K Da components,and as the growth stage increases,the composition of different levels of components also changes,coagulation The effect of AOM removal on Anabaena sp.Is mainly concentrated in> 10 K Da components,mainly hydrophobic macromolecules.The molecular weight distribution of trihalomethane formation potential of AOM of A.algae is mainly composed of <1K Da and> 10 K Da,so its removal performance is similar to that of DOC.NDMA-based precursors are mainly concentrated between <1K Da and> 10 K Da components,and components of <1K Da NDMAFP have a higher proportion,mainly hydrophilic components,so the coagulation removal effect is poor.After the coagulant is added,it has a certain removal effect on the large-molecule tyrosine / tryptophan protein and humic acid in AOM,and it has a removal effect on tyrosine / tryptophan and other small molecular substances and fulvic acid Relatively poor.