| The reservoir water of a water plant in Daqing City has seasonal pollution,serious eutrophication in summer,and a large number of zooplankton breeding problems such as cyclops and round daphnia in raw water.The large number of Daphnia in water treatment plants not only brings discomfort to people’s senses,but also poses a certain threat to the water quality safety.In this thesis,based on the original treatment unit of the water plant,the daphnia removal rate as an indicator,on the one hand,from the improvement and strengthening of water treatment process,the study of the removal of daphnia effective pre-oxidation and strengthening of the traditional process of joint daphnia removal technology.For the pre-oxidation unit,four oxidants,namely chlorine dioxide,sodium hypochlorite,potassium permanganate and ozone,were investigated,and the effect of different dosages on the removal of Daphnia was investigated;for the coagulation and sedimentation unit,four flocculants,namely polymerized ferric sulfate,polymerized aluminum sulfate,polymerized aluminum chloride and polymerized ferric aluminum chloride,were investigated,and the effect of different dosages on the removal of Daphnia was investigated;finally,the influence factors related to the penetration of Daphnia into the sand filter were investigated by using a filter column.Finally,a single-factor experiment was conducted to analyze the factors influencing the penetration of Daphnia magna into the sand filter.On the other hand,experimental studies were conducted on the effects of daphnids inactivation by micro and nano bubble ozone at different dosage levels,sustained effect,humic acid concentration on the inactivation effect and the effect of activated carbon catalyzed micro and nano bubble ozone on the inactivation of daphnids.The results showed that the best dosage of sodium hypochlorite inactivation was 2mg/L and contact time was 90 min,the best dosage of chlorine dioxide inactivation was 1.5mg/L and contact time was 40min;the best reaction time of ozone inactivation of daphnia was more than 30 min and the dosage was more than 2mg/L;potassium permanganate had the worst effect on daphnia inactivation,the best dosage was 2.0mg/L and contact time was 50 min.The four preoxidants were ranked from strong to weak: chlorine dioxide > ozone > sodium hypochlorite > potassium permanganate.The results of flocculation and sedimentation tests for Daphnia removal revealed that the best floc structure was a large floc with moderate density and good settling performance.The alum produced by ferric polymeric aluminum chloride can coat and cover the small-sized Daphnia and finally precipitate to the bottom for removal,while the removal effect on the larger round Daphnia is a bit inferior,and the best dosage is 30mg/L.The four flocculants were ranked from strongest to weakest for daphnia removal: ferric polymeric aluminum chloride > polymeric aluminum sulfate > polymeric aluminum chloride > polymeric ferric sulfate.The single-factor experimental analysis of the filter column found that the slower the filtration speed,the thicker the filter layer,and the smaller the particle size of the filter media,the better the control effect on the penetration of Daphnia magna into the sand filter.The inactivation test on Daphnia found that the rate and effect of micro and nano bubble ozone on both Daphnia species were significantly improved compared with the normal large bubble ozone when the ozone dosage was the same.In addition,the sustained inactivation effect of micro-and nano-bubble ozone on Daphnia and the resistance to organic impact were also greatly improved.The addition of activated carbon showed an increase in the rate of inactivation of cyclops and Daphnia in humic acid laced water by micro and nano bubble ozone as well as the inactivation rate. |
PDF Full Text Request