Effects of rural domestic sewage treatment in Taihu Lake Valley by wetland of plant floating island

The treatment effects of rural domestic sewage were researched by wetland of plant floating island, choosed four land plants which were Ligustrum lucidum, Ligustrum quihoui Carr, Ilex purpurea Hassk and Cymbidium faberi Rolfe were chosen to make wetland of plant floating island. The results showed that the removal rates of COD, TP and NTU could reach 60%, 65%, 60% and 70%, respectively, in 6 days of retention time under natural conditions simulated. Furthermore, all the removal rates except TP could increase to 80% above and then the retention time could decrease to 5 days by aerating intermittently. The dynamic analysis indicated that the reaction of COD removal followed the first-order reaction in the system of plant floating island with intermittent aerating, and the reaction rate constant K of plants were -0.591 (Ligustrum lucidum) and -0.978 (Cymbidium faberi Rolfe). On the other hand, the degradation process of NH3-N met the zero-order reaction. The removal rates of single plant were 46.32 mg/d (Ligustrum lucidum) and 43.76 mg/d (Cymbidium faberi Rolfe). Synergistic effects of plant roots and the biomembrane of the plant surface were good for the degradation of pollutants in sewage. The demonstration project after working continuously for more than a year indicated that the wetland of plant floating island had a better purifying capacity to treat rural domestic sewage in every moment at each season of the year, the effluent water could meet Grade B discharge demands of integrated wastewater discharge standard (GB8978-1996). The study could guide valuably some regions which were analogous or located near south of the Yangtze River to adopt the wetland of plants floating islands to treat rural domestic sewage.