Denitrification behavior and microbial community spatial distribution inside woodchip-based solid-phase denitrification (W-SPD) bioreactor for nitrate-contaminated water treatment.

The NO removal pathway and microorganisms change along with the height of an up-flow W-SPD bioreactor was investigated in this study. Modeling and microbial community analysis were used to analyze the denitrification behavior in W-SPD bioreactor. The results showed that NO removal rate matched for zero-order (R > 0.97) and first-order (R > 0.94) combination Michaelis-Menten kinetics, whereas microbial reaction rate suited for modified logistic model (R > 0.99). The excellent denitrification performance (92.5%-96.4%) and microorganisms' quantity occurred in the middle of W-SPD bioreactor. Moreover, high-throughput sequencing analysis revealed that dominant denitrifiers, carbonaceous compound degrading bacteria and fermentative bacteria co-existed in W-SPD system, which was vital for efficiently sustainable NO removal. Hence, aerobic degradation, heterotrophic denitrification and dissimilatory nitrate reduction to ammonium (DNRA) occurred successively along the water direction in the bioreactor, offering reasonable references for W-SPD bioreactor study and application.