Study On Characteristics Of Dissolved Organic Matter In Stratified Reservoirs And Its Treatment By Coagulation And Membrane Filtration

In order to understand the sources,properties and treatability of dissolved organic matter(DOM)in stratified reservoirs,quantity and quality of DOM in Jinpen reservoir as well as its treatment by coagulation and ultrafiltration were investigated from the perspective of thermal stratification.Moreover,impact of algae bloom on the content and properties of DOMwas studied in Lijiahe reservoir..The main results and conclusions are as follows.(1)During thermal stratification,the content and properties of DOM varied significantly with water depth.DOM in the upper layer was influenced by photochemical degradation significantly,and its DOC concentration was lower than those of the middle and lower layer.The proportion of aromatic organic compounds was relatively small,but the content of protein-like fluorescent component was slightly higher.The middle layer was influenced by exogenous input of organic matter substantially,and therefore its DOC and SUVA are higher,with a higher content of humic-like and fulvic-like fluorescence components.(2)The running of the artificial mixing and oxygening system accelerated the mixing of water,and made homogenization of the content and properties of DOM in different depths.Sufficient dissolved oxygen in water during artificial mixing and subsequent natural mixing promoted degradation of microorganisms and reduced DOC.The parallel factor analysis(PARAFAC)showed that the humic-like and fulvic-like fluorescent components did not decrease obviously at the early stage of mixing,but the protein-like fluorescent component decreased duringthe whole mixing period.(3)The removal of DOM by coagulation was different for various fractions.The fraction with higher SUVA was readily removed by coagulation.PARAFAC analysis showed that the humic-like and fulvic-like fluorescence components were easy to be removed by coagulation,while the protein-like fluorescent component was refractory to coagulation.Therefore,the removal rate of DOM at 20 m depth was the highest,while that in the surface water was the lowest.(4)The effect of various fluorescent components on ultrafiltration membrane fouling was different.The protein-like fluorescent component had great influence on the reversible fouling,while the humic-like and fulvic-like fluorescence components exerted significant influence on the irreversible fouling.Therefore,the ultrafiltration membrane fouling caused by upper layer water during the stratification stage was the most serious,but its reversibility was better.The growth of trans-membrane pressureduring ultrafiltration of the middle and lower layer of raw water was small,but its reversibility was much poor.(5)Algal bloom during thermal stratification had a great influence on the DOM content and composition of the upper and middle layer waters,but exerted little effect on the lower water bodies.DOM produced by algae exhibited lower SUVA and higher content of protein-like substances,which was difficult to be effectively removed by coagulation,and exhibited high fouling potential.The simulation experiments showed that the proteins and polysaccharides produced during the decay process of Microcystis aeruginosa had better biodegradability,but the aromatic components such as humic substances were not easily decomposed by biodegradation.