[Municipal wastewater treatment using a composite flocculant made of polyaluminum chloride and polydimethyldiallyammonium chloride].

A composite flocculant (denoted JYF-1), made of polyaluminum chloride (PAC) and polydimethyldiallyammonium chloride (PDMDAAC), was used in jar-tests to simulate the chemically enhanced primary treatment (CEPT) for municipal wastewater. Removal of particles, organic compounds, nitrogen and phosphorus in wastewater was investigated, and the effects of pH and surface overflow rate (SOR) on flocculation were also examined. Electrical charge and distribution of particles in wastewater were analyzed before and after flocculation. Furthermore, the flocculation mechanism and application of JYF-1 in CEPT were discussed. The results demonstrate that JYF-1 performs better than PAC under a wide pH and SOR range. When 8 mg x L(-1) JYF-1 is added, 76.72% COD and 64.31% soluble COD (SCOD) can be removed. About 90% soluble TP (STP), 80% TP and 20% TN can be removed by addition of 12 mg x L(-1) JYF-1. After flocculation, the BOD/COD ratio increases from 0.23 to 0.53, which indicates the biodegradation ability of wastewater is improved. It can be concluded that JYF-1 is a high-efficiency low-cost flocculant, which can improve outlet water quality and produce less sludge without changing the existing equipments and treating process in sewage plants.