Removal Efficiency And Mechanism Of Algal Bloom Organisms Using Different Modified Clays

Recently,the frequent harmful algal blooms(HABs)have been observed.The bloom frequency,magnitude and duration time continuously increase,leading to serious damages to the marine environments and local economy.In order to cope with the situation of frequent HABs,in the current research,we compared the removal efficiencies of HABs organisms with different types of modified clay(MC),and discussed the flocculation mechanism.This study can be treated as a reference for the control and mitigation of HABs in an emergency situation.The main results were as follows:(1)The removal efficiency of algae using inorganic MC and potential mechanismThe difference of algae removal ability by different types of modified clay were determined.D-MC,E-MC,F-MC had good performance in removal of all HABs species.A-MC,B-MC,C-MC showed high removal efficiencies in Skeletonema costatum,Prorocentrum donghaiense and Heterosigma akashiwo,while they were not efficient in removal of Phaeocystis globosa.In addition,differences in distinct HABs species removal by modified clay were found.Specifically,the small algal cells with strong moving capability(shape were spherical or close to the spherical)were difficult to remove.The ability of modified clay in removal of algae was influenced by modified conditions.Appropriate modified clay type,enhancing the surface positive charge,increasing the concentration of modifier and modified clay,decreasing the pH of modified clay suspension can benefit removal efficiency for HABs organisms.(2)The removal efficiency of algae using organic-inorganic combined MC and potential mechanismThe removal efficiency of organic-inorganic combined MC was affected by the concentration and molecular weight of organic modifier.The removal efficiency of PAM-MC firstly increased and then decreased with increasing concentration of PAM.After modified by PAC and TA,the clay particles showed higher removal ability of algae.TA/PAC-MC displayed high removal efficiency for Prorocentrum donghaiense when compared with Phaeocystis globosa.(3)The removal efficiency of algae using oxi-inorganic combined MC and potential mechanismAfter modified by oxidation and PAC,the algae removal ability was profoundly enhanced.Oxi-inorganic modified clay,namely KHSO5/PAC-MC,could rapidly remove algal organisms.Its removal ability was barely affected by suspension medium and modified method.After adding oxi-inorganic MC,the pH of algae culture solution decreased,gradually approaching to seawater.In summary,oxi-inorganic MC is one of promising and effective methods to control HABs.