The performance of simultaneous denitrification and biogas desulfurization system for the treatment of domestic sewage

This paper proposed a novel simultaneous denitrification and biogas desulfurization (SDBD) process for domestic sewage treatment and biogas upgrading. The process consisted of an expanded granular sludge bed (EGSB) for integrated autotrophic and heterotrophic denitrification (IAHD) and a biological aerated filter (BAF) for nitrification. The experiments were firstly conducted to investigate the performance of the lab-scale SDBD system with real domestic sewage at various hydraulic retention times (HRT). The system successfully achieved 83.0 ± 1.8% chemical oxygen demand (COD), 96.2 ± 1.8% ammonia (NH₄⁺-N) and 67.3 ± 4.1% total nitrogen (TN) removal efficiency without biogas introduction, and the optimal HRT of EGSB and BAF was determined to be 6 h and 4 h, respectively. Then, biogas with three different hydrogen sulfide concentrations (1.5%, 1.2% and 0.9%) was introduced into the system. Almost complete removal of hydrogen sulfide in biogas was achieved in all the tested scenarios and the removal efficiency of COD, NH₄⁺-N and TN maintained at around 86.8%, 98.4% and 83.4%, respectively. Microbial community analysis results showed that biogas introduction notably increased the bacterial diversity and particularly enriched the nitrate-reducing, sulfide-oxidizing bacteria, which forms the major contribution to the hydrogen sulfide removal in the system. Finally, we put the SDBD system in the whole treatment system of domestic sewage and discussed its economics. The results indicated that the total operating cost of sewage treatment plant could be saved to 0.59 RMB/m³, which proved SDBD system to be a promising alternative way in biological nitrogen removal and biogas desulfurization.