Simultaneous Enhancements of Nitrification and Denitrification Process of Heterotrophic Nitrification and Aerobic Denitrification Bacteria by Incorporation of Clay Minerals

The performance and mechanisms of nitrification and denitrification process of heterotrophic nitrification and aerobic denitrification bacteria enhanced by clay minerals were investigated. The batch experiment results found that the mixed clay raw ore (MC-RO) and rectorite raw ore (REC-RO) significantly improved both the nitrification process and the denitrification process under aerobic conditions. MC-RO of 0.5 g/L increased the removal of NH 4 + -N, NO 3 - -N and TN by 10.41%, 7.63% and 10.40%, respectively. And REC-RO of 0.5 g/L increased the removal of NH 4 + -N, NO 3 - -N and TN by 16.51%, 8.07% and 16.48%, respectively. The mechanisms of enhancement were explored through materials characteristics, comparison experiments and reductase activity test. The results showed that MC-RO and REC-RO have larger layer spacing, stronger layer charge properties, more adsorbed water and Fe morphology with high surface electron conduction, which led higher layer swelling of the two clay minerals relative to other clay minerals. And enzyme activity test and electron transport system activity analysis demonstrated that the strong layer swelling of clay minerals is the key factor for the activity of nitrate reductase and nitrite reductase contributing to nitrification and denitrification, respectively. It could be concluded that the low-cost clay raw ore, MC-RO and REC-RO could be used as promoters of nitrification and denitrification process in biological treatment for wastewater with high concentrations of NH 4 + -N and NO 3 - -N.