Qi Li

Plant absorption via aquatic plants is vital for the deep purification of treated wastewater. This study aimed to determine the removal efficiencies of nitrogen and phosphorus for different aquatic plants and the effect of monochromatic light as compared to white light. Five plants (i.e., Iris pseudacorus, Oenanthe javanica, Zantedeschia aethiopica, Ipomoea aquatica Forssk. and Sagittaria trifolia) were cultured in prepared wastewater and radiated by white, red, green and blue LED lamps with 8 h radiation per day, respectively. After 4 d of cultivation, the O. javanica and S. trifolia exhibited relatively better growth status and higher TP removal rates (90%). The blue light radiation played a key role in the TP uptake of the tested plants. The N removal rates of plants were relatively lower (10–40%), limited by the low COD content. The S. trifolia exhibited the highest efficiency, and red light promoted the removal of TN and NO₃⁻-N, whereas NH₄⁺-N removal was driven by blue light radiation. So, O. javanica and S. trifolia coupled with blue and red lamps as supplementary light were suggested for the deep purification of municipal treated wastewater. The effect of intensity and ratio of monochromatic lights could be a direction for further research.

To verify the feasibility of biofilm-membrane bioreactor in municipal wastewater treatment. In this paper, based on the Fourier series algorithm, the basic configuration of biofilm-membrane bioreactor, the design of membrane bioreactor test index and method, the proposed urban wastewater treatment system based on biofilm-membrane bioreactor, and the creation of experiments to verify the biofilm-membrane bioreactor with the example of urban wastewater in the sewer of residential buildings in the district on the two COD _Cr and NH ₄ ⁺ -N in urban wastewater in municipal wastewater. The results showed that the removal rate of COD _Cr in municipal wastewater by the biofilm-membrane bioreactor system increased with time, and the removal rate was stable at about 83%. The NH ₄ ⁺ -N removal rate increased with time and was stable between 85 and 90%. It can be shown that biofilm-membrane bioreactor can sufficiently reduce the concentration of COD _Cr and NH ₄ ⁺ -N in municipal wastewater, thus promoting municipal wastewater treatment. It also presents a new solution for urban wastewater treatment.