Application performance of a new coagulant in wastewater reuse

Ultraviolet (UV) absorption characteristics of poly-Al-Zn-Fe (PAZF), a polymerized coagulant containing three kinds of metallic elements prepared from a galvanized-aluminum slag, was analyzed by UV-visible spectrophotometry during its polymerization process. Pollutant removal by PAZF in treating various wastewaters was investigated, in comparison with that of polyaluminum chloride (PAC). The results showed that PAZF can be applied to different wastewaters and had excellent coagulation behavior due to its special internal composition. Various complicated substances having different absorption wavelengths and polymeric properties were produced during the PAZF polymerization process, and the structures of these complicated substances were adjusted continuously with the increasing of the polymerization time. PAZF posed better turbidity and organic matter (chemical oxygen demand, COD(Cr)) removal than PAC for different wastewaters, and the required dosage of PAZF was far lower than that of PAC when achieving the same coagulation performance. For pharmaceutical, sugar, dyeing, simulated pesticide and landscape wastewaters, PAZF gave higher removal of turbidity or COD(Cr) than PAC, by up to 79.5% (coagulant dose: 74 mg/L) or 16% (148 mg/L), 13.4% (111 mg/L) or 10% (185 mg/L), 26.5% (148 mg/L) or 8.1% (18.5 mg/L), 40% (18.5 mg/L) or 13.4% (111 mg/L), and 5% (70 mg/L) or 5% (70 mg/L), respectively.