Combined application analysis of MBBR and magnetic coagulation process in a full-scale project

The combined application of moving bed biofilm reactor (MBBR) and magnetic coagulation (MC) is a new method of enhancing nitrogen and phosphorus removal of wastewater treatment plants with limited land occupation. This had been successfully used in a full-scale 30,000-m3/d wastewater treatment plant in Guangdong Province, China. The effluent concentrations of COD, NH4+–N, total phosphorus (TP), and suspended solid (SS) stabilized at 11.6 ± 3.9, 1.4 ± 1.3, 0.28 ± 0.11, and 2.2 ± 1.2 mg/L when the corresponding influent concentrations were 81.7 ± 27.5, 15.2 ± 3.0, 1.40 ± 0.29, and 42 ± 19 mg/L, respectively, which could steadily meet the designed discharge standard even though the land occupation was merely at 2000 m2. Regarding the MBBR effluent, the MC process sufficiently removed residual SS, TP, and some COD within 3 min of sedimentation, which ensured that the discharge reached the designed standard. The relative abundance of nitrifying genera of the secondary MBBR was higher than that of the primary MBBR, leading to a greater NH4+–N removal ability for the secondary MBBR. Meanwhile, the primary MBBR was superior to the secondary MBBR in terms of organic matter removal. The suspended carrier was more competent in enriching nitrifiers than the activated sludge, highlighting the significant advantage of MBBR. However, the suspended carrier was insufficient in enriching phosphorus removal bacteria as compared with the activated sludge, leading to a poor biological TP removal efficiency of the MBBR process. Further research is needed to improve the biological phosphorus removal ability of MBBR.