Investigation of nitrite accumulation by hydrogenotrophic denitrification in a moving bed biofilm reactor for partial denitrification and anammox process

The partial denitrification and anammox (PDA) process has received attention for its ability to optimize treatment of wastewater containing low NH4+N concentration. This study investigated the suitable operational condition for NO2--N accumulation by hydrogenotrophic denitrification (HD) in operation of a lab-scale moving bed biofilm reactor, for future application in PDA process. NO3--N accumulation was achieved by minimizing the H-2 flow rate under optimized condition (i.e., 15 mL/min H-2 flow rate, 40 mg-N/L influent NO3--N, 7.0 h hydraulic retention time, and 2 L working volume). Hydrogenophaga comprised 39.2% of the bacterial abundance after NO2--N accumulated, indicating its contribution to the NO2--N accumulation. In addition, an intermittent H-2 supply maintained the NO2--N accumulation rate (NAR) and maximized the nitrite accumulation efficiency (NAE). A H-2 supply ratio of 0.7 (i.e., ON: 7 min, OFF: 3 min) was optimal, which induced increases in NAR, NAE, and the NO3--N removal efficiency that reached 0.07 +/- 0.01 kg-N/m(3)/d, 64.4 +/- 14.5%, and 89.2 +/- 8.9%, respectively. The ratio of H-2 supply rate to the NO3--N loading rate was calculated as 4.3 in.this experiment, which may represent the optimal balance for maximization of NO2--N accumulation by HD.

Automated summary

This study investigated the suitable operational condition for NO2--N accumulation by hydrogenotrophic denitrification (HD) in the PDA process. It was found that minimizing the H-2 flow rate and providing intermittent hydrogen supply could achieve nitrite accumulation and improve the treatment efficiency of wastewater containing low NH4+N concentration.