Research On Efficiency And Mechanisms Of Heavy Metal Adsorption By EPS From Activated Sludge

Extracelluar polymeric substances(EPS) is the third largest components of activated sludge characterized by efficient heavy metal enriching ability and has caused extensively attention for its special identity and important position. Today, achievements have obtained from the research on the components, characteristics, extraction methods and metal-enrich-ability of EPS. However, few researches have been conducted on the efficiency and mechanisms of EPS adsorbing heavy metals. Considering the serious heavy metal contamination of water and soil and the limits of exist treatment technology, efficiency and mechanisms of EPS adsorbing the classic heavy metal, Pb²⁺, Cd²⁺, Zn²⁺, both from contaminated water and soil were studied. Reduction in volume and mass of waste activated sludge by extraction of EPS enlightens the meaning of using EPS in heavy metal contamination control.In this paper, extraction methods were compared and effects of temperature on the composition of EPS from 3 extensively exist activated sludge (from treatment of municipal wastewater and anaerobic, aerobic treatment of Cola wastewater) were investigated. The influences of EPS on dewaterbility of sludge were also studied. It was believed that to this research, steaming is the best extraction method to obtain EPS from sludge; -20℃is the proper temperature for EPS storing; Extraction of EPS benefits the reduction in volume and mass of sludge.Based on the above research, EPS from sludge cultivated by simulated municipal and Cola wastewaterwere were used as adsorbent for heavy metal removing. Effects of pH, EPS dosage and duration time on the removal efficiency of Cd²⁺, Zn²⁺ from water were investigated. The results showed: EPS was efficient in Cd²⁺, Zn²⁺ adsorption. The optimal pH value is 6.0. The optimal dosage of EPS is 375mg/L and 250mg/L. At optimal condition, the absorption efficiency reaches 27mg/g of Cd²⁺ and 47.5mg/g of Zn²⁺ by EPSâ… , 19.5mg/g of Cd²⁺ and 40.5mg/g of Zn²⁺ by EPSâ…¡, 17mg/g of Cd²⁺and 37mg/g of Zn²⁺ by EPSâ…¢. The adsorption processes of Cd²⁺and Zn²⁺ with EPS both have two steps: fast adsorption and slow adsorption. Langmuir isotherm equations could describe...