Nitrogen removal by bioaugmentation in constructed wetlands for rural domestic wastewater in autumn

Two subsurface flow constructed wetlands planted with Typha orientalis (CCW) and Phragmites (RCW) were constructed to study the effect of the addition of Paenibacillus sp. XP1 on nitrogen removal from rural domestic wastewater in autumn (15-21 degrees C). CCW inoculated by Paenibacillus sp. XP1 (CCW-XP1) had obvious improvement on ammonia (NH3-N) and total nitrogen (TN) removal efficiency than RCW-XP1. The removal efficiency of TN in the CCW is similar to that of NH3-N, and the maximal removal efficiency of 78% was achieved, doubled with the control group. The final removal efficiencies of the CCW-XP1 were found to be 73% for chemical oxygen demand, 94% for NH3-N, and 78% for TN. The effect of hydraulic retention time (HRT) variation on treatment efficiency of CCW was also discussed. Statistical analyses indicated that the optimal HRT for NH3-N concentrations achieving the GB18918-2002 standard (China) for Class I-B guideline of 8.0 mg/L was 4 days, while the NH3-N removal of the control group had not meet the criteria until 18 days. In comparison with the control group, HRT of CCW-XP1 was shortened for more than 15 days. The CCW would be a cost-effective measure for N removal from rural domestic wastewater by bioaugmentation.