The Study on Segregation Purification for ...

Nitrogen is one of the main pollutants in sewage. The traditional wastewater treatment technology, which lacks in integrated collection systems, poses excessive investment costs on the control of nonpoint pollution. The constructed wetland capable of removing nitrogen effectively, moreover, it is friendly to eco-system and requires low investment costs. So it is an important technology to reduce the nitrogen load, especially from the nonpoint source. In order to further study on nitrogen removal mechanism and improve the removal rate of nitrogen from wastewater, combined floating bed and bio-film constructed wetlands (FBCW) simulation system was built to treatment sanitary wastewater with filamentous palm, non woven and Trifolium repens L. TN, NH3-N, NO3-N, NO2-N and pH were investigated for upper, middle and lower layer wetland system by intermission operation during 118 days under natural conditions. Results demonstrated that the system was into the stable phase of high removal rate after 48 days with hydraulic loading of 2m3/(m2.d) and the hydraulic retention of 10 hours. Average removal rate of TN and NH3-N were 64.4% and 60.6%, and the highest removal rate reached 79% and 77%, respectively. Segregation effect was clear. The purification ability of upper layer was higher than the middle. Middle layer was higher than the lower layer. TN and NH3-N removal rate of upper layer were 1.96, 1.45 times and 1.36, 1.12 times higher than that of the middle and the lower layer, respectively. And the system has a good buffering capacity. pH variation of inflow water have a greater impact on the lower layer, while the upper pH values stabilized at 7.38-7.74.