Effect of immobilized bacteria and algae filler on enhanced nitrogen and phosphorus removal in constructed wetland

In view of the poor nitrogen and phosphorus removal efficiency of constructed wetland, the immobilized bacteria and the immobilized bacteria and algae were used as the substrate to investigate the effects of the control (gravel) group,the immobilized bacteria group and the immobilized bacteria and algae group on nitrogen and phosphorus removal in the constructed wetland. The results showed that the immobilized bacteria group and the immobilized bacteria and algae group enhanced the load resistance and stability of the wetland system, and the pollutants in the water body could be quickly removed in the early stage of wetland operation. The immobilized bacteria and algae group, the immobilized bacteria group and the gravel group began to stabilize the effluent on the 40th, 48th and 56th day of wetland operation, respectively. The stability of effluent quality of the immobilized bacteria group and the immobilized bacteria and algae group was better than that of the gravel group, reaching Level 1 A standard of Discharge Standard of Pollutants for Urban Sewage Treatment Plants (GB 18918-2002). The algae powder and its adsorbed organic matter could be used as supplementary carbon source to enhance nitrogen removal. The effluent concentrations of NH₃-N、TP and COD_Cr from the immobilized bacteria and algae group reached Class Ⅴ standard of Environmental Quality Standards for Surface Water (GB 3838-2002). The removal rates of COD_Cr, NH₃-N, TN and TP were 58.10%, 81.47%, 86.70% and 85.54%, respectively.