Soil infiltration bioreactor incorporated with pyrite-based (mixotrophic) denitrification for domestic wastewater treatment

In this study, an integrated two-stage soil infiltration bioreactor incorporated with pyrite-based (mixotrophic) denitrification (SIBPD) was designed for domestic wastewater treatment. Benefited from excellent adsorption ability and water-permeability, soil infiltration could avoid clogging, shorten operating time and lower maintenance cost. Respiration and nitrification were mostly engaged in aerobic stage (AES), while nitrate was majorly removed by pyrite-based mixotrophic denitrification mainly occurred in anaerobic stage (ANS). Fed with synthetic and real wastewater for 120 days at 1.5 h HRT, SIBPD demonstrated good removal performance showing 87.14% for COD, 92.84% for NH4+-N and 82.58% for TP along with 80.72% of nitrate removed by ANS. TN removal efficiency was 83.74% when conducting real wastewater. Compared with sulfur-based process, the effluent pH of SIBPD was maintained at 6.99-7.34 and the highest SO42− concentration was only 64.63 mg L−1. This study revealed a promising and feasible application prospect for on-site domestic wastewater treatment.