Abstract: The coagulation of polymerized aluminium chloride （PAC） and polyacrylamide （PAM） and Vallisneria natans were combined to treat the domestic sewage， and the removal efficiency of ammonia nitrogen， total nitrogen， total phosphorus and COD by different treatments was explored. It was shown that the combination of PAC and PAM was effective to treat domestic sewage. The optimum dosages of PAC and PAM were 195 and 1.2 mg·L-1， respectively， and the optimum treatment procedures were as follows: after the addition of PAC， sewage were stirred at 200 r·min-1 for 30 s. Then PAM was added， and the sewage was stirred at 200 r·min-1 firstly for 30 s， and then at 70 r·min-1 for 8 min. Vallisneria natans was introduced for ecological purification after coagulation. Both in the catering and washing wastewater， the most effective purification appeared at a planting density of 32 g·L-1. And the best removal efficiency was achieved after 8 or 12 d treatment in the catering or washing wastewater， respectively.

Key words: catering wastewater, washing wastewater, coagulation, Vallisneria natans, ecological purification