Coagulation To Remove Cynabacteria By Combination Of Chitosan And Polyaluminum Chloride

Cyanobacterial blooms not only cause a series negative impacts to conventional drinking water treatment processes,but also pose a great challenge for water safety.The enhanced removal rate of cyanobacteria as a result of the combination of chitosan(CTS)and polyaluminum chloride(PAC)was observed in this study.The raw water contain 3.5(±0.5)×10~8 cells/L of Microcystis aeruginosa(FACHB-911)or Anabaena flos-aquae(FACHB-245).Single factor experiment and response surface methodology were use to achieved the most effective coagulation condition,providing technical guidance and theoretical fundament for coagulation of harmful algal blooms.Coagulants with CTS(0.1~1.2 mg/L)or PAC(0.5~6.0 mg/L),the removal rates increased first and then decreased with the increasing dosage of coagulant.When CTS was used only,the chlorophyll a removal rates of M.aeruginosa and A.flos-aquae were 88.1%and 83.2%,respectively.When PAC was used only,the removal rates of chlorophyll a of M.aeruginosa and A.flos-aquae were 90.1%and 91.5%respectively.In the pH range of 7~10 in raw water,7~8 for CTS and 7~9 for PAC were optimal.The combination of CTS with PAC greatly improved the removal rate of cyanobacteria.At pH 9.0(a simulation of alkaline algae-containing water),the type of PAC/CTS was the most effective in removing algae.The best condition for coagulation of M.aeruginosa were:CTS 0.40 mg/L,PAC 2.0 mg/L,and the removal rate of chlorophyll a was 94.9%.As for A.flos-aquae,in the condition of CTS 0.24 mg/L,PAC 2.00 mg/L,could achieve chlorophyll a removal rate of 95.3%.The PAC/CTS removed cells was the most effective for stronger charge neutralization,briding and sweeping ability.The combination of CTS and PAC has higher removal rate on EOM than CTS and PAC individually applied.PAC/CTS is the most effective,and the removal rate of dissolved organic carbon(DOC)and dissolved organic nitrogen(DON)for M.aeruginosa were 51.3%and 39.8%,and 42.5%and 35.3%for A.flos-aquae,respectively.The EEM showed that the removal rates of EOM by PAC/CTS for M.aeruginosa and A.flos-aquae were 60.9%and41.0%respectively.The concentration of icrocystin(MCs)in M.aeruginosa was 2.41?g/L and anatoxin-a in A.flos-aquae was 0.28?g/L,and the highest removal rate were 29.0%and27.6%,respectively.