The Oxidation Of Sodium Percarbonate Activated By Fe²⁺ To Enchance Microcysis Aeruginosa Coagulation

As global climate change and entrophication reinforce,the infrequency and intensity of cyanobacteria bloom have been increasing throughout the world.The abnormal proliferation of cyanobacteria in dringking water resource cause the color change of water,meanwhile algae cell release intercellular organic matters and toxins into water,which severely influence the safety of drinking water.Coagulation is a key processe of drinking water treatment for algae removal.After coagulation,massive algea cells can separate from water and accumulate into sludge.Recently,the efficiency of algal cell removal using traditional coagulation is not ideal.Preoxidation coagulation process can modifiy the algae removal,but it can destroy the cell integrity and induce to the release of intercellular organic mater and toxins into water,which can cause greater water risk.Therefore,it is of great significance to realize enhanced coagulation to remove algae and control the release of intracellular organic and toxin substances in the process of coagulation treatment.In view of the above problems,this study adopted the Fe2+/SPC pre-oxide coagulation technology to enhance algae removal during the cyanicbacteria bloom outbreak,and investigate the the algae removal and cells damage,and the release and degradation of intracellular organic matters and toxins during the reaction process.Futuremore,this study investigated the effects of enhanced coagulation by Fe2+/SPC preoxidation on algal cell activity,and clarify the release of intracellular organic matters and toxins during sludge storage.The concrete contens and results as follows:(1)The optimum dosages of Fe2+and SPC for effective removal of Microcystis aeruginosa(106 cells/mL)with low damage are the 1:1 molar ratio of Fe2+to SPC,0.2 mM dosage of Fe2+and SPC under condition of no additional coagulant.(2)During peroxidation coagulation process,M aeruginosa cells released intercellular organic matters and Microcystins into water in response to oxidization stress.Meanwhile,active free radicals and hydrolyzed flocs formed by in suit Fe3+can remove organic matters and Microcystins by degradation and absorbtion,keeping the concentraitons of soluble organic carbon and microcystins under control in optical dosage condition.(3)With the increase of storage time,algal cells continually produced the oxidative stress response for severe oxidative damage effect caused by preoxide coagulation,and algal cells entirely lost their activities on day 8.In the high-dose group,algal cells were seriously damaged and released humic acid and fulic acid substances on day 0,owing to strong oxidative damage during the preoxide coagulation process.However,for optical dosage condition,algal cells began to lyse and released a large amount of intracellular protein substances on day 4.Additionally,the algal cells were largely damaged and relased abundant microcystins on day 6.In order to avoid secondary quality pollution of water caused by algal cells damage during sludge storage time,the storage sludge should be treated and disposed within 4 days.