Study on the Advanced Treatment Technology for Wastewater Containing both Zn<sup>2</sup><sup>+</sup> and Cd<sup>2+</sup>

Abstract

The removal of heavy metal ions is very significant for the restoration of ecological environment and recycling utilization of water resources. By using the advanced treatment technology for wastewater such as strengthening coagulant, adsorption by modified zeolite and the combination of both，respectively, the influence of different parameters like adding dosage of coagulant and flow rate of raw water on the removal efficiency of zinc and cadmium ions from wastewater was investigated, and the operating conditions were optimized. The results showed that the removal efficiency of zinc and cadmium ions from wastewater both improved in the combination process of strengthening coagulant and adsorption by modified zeolite, and they increased by 5.8% and 2.8% respectively than that of strengthening coagulation process alone, while the removal efficiency of zinc ion increased by 4.5% than that of adsorption by modified zeolite process alone. The removal efficiency of zinc and cadmium ions both gradually increased with increasing adding dose of coagulant, but they decreased when flow rate of raw water increased. In the combination treatment process of strengthening coagulant and adsorption by modified zeolite, the suitable operating condition were selected as 8 of initial pH of wastewater, 18 mg/L of polyaluminium chloride (PAC), 9mg/L of polyacrylamide (PAM), 150g of modified zeolite and 20L/h of flow rate of raw water.