Advanced treatment of secondary effluent by the integration of heterogeneous catalytic ozonation and biological aerated filter.

The advanced treatment of secondary effluents was investigated by employing heterogeneous catalytic ozonation integrated with a biological aerated filter (BAF) process. The results indicated that catalytic ozonation with the prepared catalyst (MnxCuyOz/γ-Fe2O3) significantly enhanced the performance of pollutant removal and broke up macromolecules into molecular substances by the generated hydroxyl radicals. These molecular substances were easily absorbed by microorganisms in the microbial membrane reactor. In the BAF process, chemical oxygen demand (COD) (chemical oxygen demand) decreased from 54.26 to 32.56 mg/L, while in catalytic ozonation coupled with the BAF, COD could be reduced to 14.65 mg/L (removal ratio 73%). Under the same condition, NH4+-N decreased from 77.43 to 22.69 mg/L and 15.73 mg/L (removal ratio 70%) in the BAF and the catalytic ozonation coupled with BAF, respectively. In addition, the model that highly correlated influent COD to effluent COD and reactor height for filler could predict the removal ratio of COD of the BAF system. Based on the microbial community analysis, ozone in the solution had a certain screening effect on microorganisms, which helped to better adapt to the ozone-containing environment. Therefore, the integrated process with its efficient, economic, and sustainable advantages was suitable for the advanced treatment of secondary effluents.