Treatment of Landfill Leachate Reverse Osmosis Concentrates by Advanced Oxidation-Heterotrophic Nitrification-Aerobic Denitrification Combination process

This study aimed to develop a multistage treatment system for highly toxic wastewater named reverse osmosis concentrates of landfill leachate. Therefore, a combination of the ammonia stripping process (ASP), catalytic ozone oxidation process (COP), and heterotrophic nitrification-aerobic denitrification process (HNADP) was proposed and the quality of effluent was evaluated for the concentration of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total nitrogen (TN). ASP had moderate removal efficiency of NH4+-N, and TN in the effluent. COP was catalyzed by cerium-supported-activated carbon achieved good performance in disposal of COD. The effluent of HNADP had the most significant removal efficiency of COD, NH4+-N, and TN. As a result, the effluent of combined process successfully met the discharge standards for NH4+-N and TN according to Table 1 of GB 16889-2008 in China. To investigate the microbial mechanism of pollutant removal in HNADP, 16S rRNA high-throughput sequencing was performed and the results suggested that the relative abundance and diversity of microorganisms fluctuated with the changes of COD/TN ratio in HNADP. Truepera and Halomonas were identified as the key genera involved in the simultaneous degradation of COD and nitrogen-containing pollutants, the functional genes (hao, amoA, nirS, and nirK) were predicted in nitrification and denitrification process. Overall, this study demonstrates a feasible multistage system for treatment of concentrates and propose that further explorations of combined techniques may lead to even more satisfactory removal efficiencies.