Control Of Microcystis Aeruginosa By Quaternary Ammonium Salt Chitosan

In recent years,cyanobacterial blooms have ocuured in many lakes in our country,which have seriously affected people's production and living.Cyanobacteria bloom will destroy the water environment.In addition,the occurrence of cyanobacteria blooms in lake which is a source of drinking water,the damaged algal cells release intracellular toxins into the water,will directly threaten the safety of drinking water.Microcystis aeruginos(M.aeruginosa),as one of the most common harmful algal bloom species in our country,would release microcystins(MCs)with high acute toxicity and a wide distribution in the nature,cause the attention of the whole world.In the drinking water treatment process,the coagulation is key process for algae remove.After coagulation,the algae cells accumulate into flocs as sludge.However,high dose of inorganic coagulant is needed to effectively remove harmful algae.And the residual Fe and Al ions of inorganic coagulant would cause secondary pollution and deteriorate water quality.Therefore,a low-dose,degradable and non-pollution organic coagulant can solve the issues above.Chitosan quaternary salt,a new environmentally material,characterized by flocculation and antibacterial properties,can be applied in many fields.During the outbreak of cyanobacteria bloom,there are few studies on the control of cyanobacteria by quaternary ammonium salt chitosan.Thus,it is important to study the effect of quaternary ammonium salt of Chitosan on the growth of Microcystis aeruginosa,and the removal effect of cyanobacteria cells in the drinking water treatment process when chitosan quaternary ammonium salt is used as a coagulant,which can provide a theoretical basis for the application of control of Microcystis aeruginosa.Simulation an algal bloom in high algae laden period,the effects of of chitosan quaternary ammonium salt on the growth and toxin release of Microcystis aeruginosa at different doses were studied and using the chitosan quaternary ammonium salt as coagulant to investigate the M.aeruginosa cell integrity and toxins release during the coagulation-sedimentation process.During the research,the following results were obtained:(1)Under the condition of reducing the release of MCs,the optimal concentration was 1.2 mg/L for inhibiting Microcystis aeruginosa effectively.(2)According to this study,the optimum coagulation conditions for the effective removal of cyanobacterial cells(M.aeruginosa FACHB-905)in blooms are coagulant dosage 1.5 mg/L(HTCC),rapid mixing for 0.5 min at 300 rpm and slow mixing for 30 min at 60 rpm.(3)In the HTCC coagulation process,most of cells were removed intactly,the variety of coagulant dosage and mechanical actions did not cause any damage to cell integrity.(4)When HTCC is used as coagulant,the size of floc is large and the structure is stable(5)In the flocs storage processes,the formation of flocs brought a protection for M.aeruginosa cells and HTCC damaged cells.Under the optimum coagulation,the time required for cell disruption in the flocs storage processes is much longer than sludge discharge period of the conventional sedimentation tank,which meant the floc is safe.