Application of Polysilicato-Iron Coagulant to Coagulation of Algae and Municipal Wastewater
A new inorganic polymer coagulant, polysilicato-iron (PSI), was developed. PSI has a molar ratio of Fe to Si of 1:1 to 1:5 and a molecular weight of 200 000 to 500 000 Da. The optimum pH ranges for the coagulation of suspended particles and soluble organics are 6.0 to 8.0 and 4.5 to 7.0, respectively. This paper deals with the effectiveness of PSI for the coagulation of municipal wastewater and algae such as Microcystis sp. and Stephanodiscus sp. Jar test results showed that, compared to aluminum sulfate (AS) and polyaluminum chloride (PAC), PSI is very effective for coagulating algae. With dosages equivalent to 0.16mmol/l Fe in PSI, the removal efficiencies of Microcystis sp. and Stephanodiscus sp. were 98 % and 99 %, respectively. This is significantly better than 20 % and 60 %, respectively, for the two species using 0.16mmol/l Al in PAC. The jet mixed separator (JMS) was used as a process unit for simultaneous flocculation and sedimentation. With a PSI dosage of 5 mgFe/l and a pH of 6.5, and a hydraulic detention time of 90 min in the JMS, the average JMS effluent turbidity and total phosphorus concentration were 27 Turbidity Unit (TU) and 0.6mg/l, respectively.
KeywordsMunicipal Wastewater Porous Plate Aluminum Sulfate Aluminum Sulfate Turbidity Removal
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