Study On Eutrophication Algae Removed By Poly-aluminum-ferric-silicate-chloride

Coagulation is one of the most widely used water treatment methods, and it is efficient, low-cost and convenient to operate to remove algae.AlCl3FeCl3,Na2SiO3,hydrochloric acid and Na2CO3 being raw materials, a series of poly-aluminum-ferric-silicate-chloride(PAFSC),which has different basicity(B) and Si/Al/Fe molar ratio, was prepared by copolymerization. With the water samples from Lianhua Lake. Jar test was carried out to research the coagulation properties of PAFSC with different B and Si/Al/Fe molar ratio under different dosage, including turbidity removal, color removal and Chla removal. Before and after the raw water was treated,the change between the structure of algae community was researched.Following are the main results:①The structure and morpholopy of the polymer and the size of the polymer of the PAFSC were affected by the Si/Al/Fe molar ratio and basicity(B).Compared with PAC,PAFSC is characterized by having higher turbidity removal ,color removal,Chla removal, better coagulating efficiency and wider pH range by jar test.②Algae removal processing optimizing by PAFSC were as follows. The turbidity ,color, Chla are removed from raw water respectively. The removal rates reach 95.6%,93.0%,92.0%with mixing round intension 200r/min, coagulating 2min,flocculating reacting intension 50r/min, flocculating 20min.③There is a serious eutrophication in Lianhua Lake, and during the period between May and August every year, the algae in the lake increase rapidly, which leads to too large a quantity of algae. Phytoplankton in Lianhua Lake consist mainly of M.aencginosa Kutz., M.incerta Lemn. and Euglena caudate Hubn., which belong to Cyanophyta; diameter of those microorganism ranges from 10~100μm. Coagulation experiments were carried out with PAC and PAFSC respectively, and the change of the algae community was analysised.The conclusion is : while used to treat raw water which micro-algae dominate, PAC is less effective than PAFSC obviously.Finally, the coagulation mechanism was discussed, adsorption bridging and precipitation catch mechanisms, especially by charge neutralization and adsorption bridging mechanism. In a word, PAFSC is a high-effectieness inorganic polymer coagulant.