Pollutant removal in subsurface wastewater infiltration systems with/without intermittent aeration under different organic pollutant loadings

Organic pollutant and nitrogen removal performance of subsurface wastewater infiltration systems (SWISs) with and without intermittent aeration, and operated under different organic pollutant loadings, was investigated. The intermittent aeration strategy not only significantly increased removal rates of organic pollutants and NH4+-N, but also successfully created aerobic conditions at a depth of 50 cm and did not change anoxic or anaerobic conditions at a depth of 80 and 110 cm, resulting in high TN removal. Increasing organic pollutant loading did not affect the removal of organic pollutants and nitrogen in intermittent aerated SWISs. High removal rates of COD (98.0%~98.4%), NH4+-N (93.8%~98.1%) and TN (84.5%~94.0%) were simultaneously obtained in intermittent aerated SWISs for organic pollutant loadings ranging from 7.4 to 29.1 g COD/(m2∙d), and these removal rates were significantly higher than for non-aerated SWISs. The results suggest that intermittent aeration is a reliable option to achieve high nitrogen removal in SWISs, especially with high organic pollutant loading.Keywords: subsurface wastewater infiltration system, intermittent aeration, oxidation reduction potential, organic pollutant loading, pollutants removal