Removal Of Algae In Water Supply By Advanced Pre-oxidation Technology And Chemical Coagulation

In recent years,although our country has done a great deal of work in terms of protecting surface water and preventing eutrophication which causes algal blooms,the outbreak of algae in the water supply often occurs.At present,China's urban water supply disinfection is mainly controlled by adding chemical oxidants to limit the concentration of algae.However,the chloroform and other substances caused by liquid chlorine have proved potential carcinogenicity to human,which has aroused a high degree of human's concern.A study was made on the removal of Oscillatoria tenuis by coagulation and hydrogen peroxide pre-oxidation,compared with ultraviolet radiation pre-oxidation,using Kaolin as coagulant aid,and polyaluminium chlorate(PAC) as flocculation reagent. The removal rates of turbidity and chlorophyll a,the changes of CODMn and the content of residual aluminum were investigated.After pre-oxidation,by observing the cellular morphology and the ability to restore growth of algae,the effects of hydrogen peroxide pre-oxidation and ultraviolet radiation pre-oxidation on algae cytoactive were studied respectively.Finally,the best composite conditions were found out.Under water quality conditions in the experiment,through orthogonal experiment,the optimum coagulation condition with hydrogen peroxide,PAC and Kaolin is worked out as follows:pH=7.0,2.5mg/L hydrogen peroxide, 20min pre-oxidation time,34mg/L Kaolin,3.5mg/L PAC with 25 min sedimentation time. Under optimal experimental condition, the removal rates of turbidity and chlorophyll a reach 96.4% and 98.2% respectively.The optimum coagulation condition with ultraviolet radiation,PAC and Kaolin is worked out as follows: pH=7.5,4min ultraviolet radiation time,3.5mg/L PAC,45mg/L Kaolin,after the treatment,the removal rates of turbidity and chlorophyll a reach the highest which are 94.85% and 98.88% respectively.Under the best composite condition,both of the content of residual aluminum are below the《Standards for drinking water quality GB5749-2006》.