Efficient rural sewage treatment with manganese sand-pyrite soil infiltration systems: Performance, mechanisms, and emissions reduction.

The application of soil infiltration systems (SISs) in rural domestic sewage (RDS) is limited due to suboptimal denitrification resulting from factors such as low C/N (<5). This study introduced filler-enhanced SISs and investigated parameter impacts on pollutant removal efficiency and greenhouse gas (GHG) emission reduction. The results showed that Mn sand-pyrite SISs, with hydraulic load ratios of 0.003 m3/m2·h and dry-wet ratios of 3:1, achieved excellent removal efficiency of COD (92.7 %), NH4+-N (95.8 %), and TN (76.4 %). Moreover, N2O and CH4 emission flux were 0.046 and 0.019 mg/m2·d, respectively. X-ray photoelectron spectroscopy showed that the relative concentrations of Mn(Ⅱ) in Mn sand and Fe(Ⅲ) and SO42- in pyrite increased after the experiment. High-throughput sequencing indicated that denitrification was mainly performed by Thiobacillus. This study demonstrated that RDS treatment using the enhanced SIS resulted in efficient denitrification and GHG reduction.