Pollutants removal, greenhouse gases emission and functional genes in wastewater ecological soil infiltration systems: influences of influent surface organic loading and aeration mode.

The influences of influent surface organic loading rate (SOLR) and aeration mode on matrix oxygen, organic matter, nitrogen, phosphorus removal, greenhouse gases emission and functional gene abundances in lab-scale wastewater ecological soil infiltration systems (WESISs) were investigated. In WESISs, intermittent or continuous aeration improved oxygen supply at 50 cm depth and hardly changed anaerobic condition below 80 cm depth, which enhanced chemical oxygen demand (COD), NH-N, total nitrogen (TN) removal, the abundances of bacterial 16S rRNA, amoA, nxrA, narG, napA, nirK, nirS, qnorB, nosZ genes and reduced CH, NO conversion efficiencies with SOLR of 16.9 and 27.6 g BOD/(m d) compared with non-aeration. Increased SOLR resulted in high TN removal, low NO emission in aeration WESIS, which was different from non-aeration WESIS. High average COD removal efficiency of 90.7%, NH-N removal efficiency of 87.0%, TN removal efficiency of 84.6%, total phosphorus (TP) removal efficiency of 93.1% and low average NO emission rate of 12.8 mg/(m d) were achieved with SOLR of 16.9 g BOD/(m d) in intermittent aeration WESIS. However, continuous aeration WESIS obtained high average removal efficiencies of 90.1% for COD, 87.5% for NH-N, 84.1% for TN, 92.9% for TP and low average emission rate of 13.1 mg/(m d) for NO with SOLR of 27.6 g BOD/(m d). Aeration could be an optional strategy for WESISs to achieve high pollutants removal and low CH, NO emission when treating wastewater with high SOLR.