Effect of Feeding Gas Type and N/S on a Novel Sulfide-Driven Denitrification Methane Oxidation (Sdmo) System

To save the treatment costs of nitrogen-polluted water, a novel sulfide-driven denitrification methane oxidation (SDMO) system, which integrated autotrophic denitrification (AD) and denitrification anaerobic methane oxidation (DAMO) to simultaneously realize wastewater denitrification and biogas utilization in situ , has been operated for 735 days in previous study. In this work, nine batch groups V0—V8 derived from previous reactors were proceeded to investigate the effect of feeding gas type and N/S ratio on the kinetic performance, microorganism community structure, and functional genes for comprehensive understanding of SDMO system. Results showed biogas serving as feeding gas for SDMO system would enhance nitrate removal efficiency both through DAMO and AD. Meanwhile, as N/S of SDMO system rising up, the nitrate removal efficiency would decrease but nitrate removal contribution via DAMO/AD would increase. Group V3 (N/S=2.3) with 1.5% hydrogen sulfide content biogas serving as feeding gas owned the highest nitrate removal efficiency, leading from the highest density of nitrate reduction genes. In this group, nitrate removal efficiency through DAMO was 33.1% and through AD was 65.6%. Low hydrogen sulfide content in feeding gas gave little effect on microorganism community structure but high hydrogen sulfide content would decrease the abundance of DAMO bacteria Candidatus Methylomirabilis and increase abundance of AD bacteria Thiobacillus . Comparing with V1, nitrate reduction genes napA , narG , nirK , nirS , cnorB and sulfide oxidation gene soxB up-regulated in HS groups (biogas with H 2 S content >1% serving as biogas) while gene pmoA up-regulated in LS groups (biogas with H 2 S content <1% serving as biogas).