Improving soil aquifer treatment efficiency using air injection into the subsurface

Abstract. Soil aquifer treatment (SAT) is an effective and sustainable technology for wastewater or stormwater treatment, storage, reuse. During SAT, the vadose zone acts as a pseudo-reactor in which physical biochemical processes are utilized to improve infiltrated-water quality. Dissolved oxygen (DO) necessary aerobic microbial oxidation of carbon nitrogen species effluent. Therefore, enhance aeration, SAT generally operated flooding drying cycles. While long periods (DPs) lead better oxidizing conditions water quality, they reduce recharge volumes. As population grows, quantity effluent directed sites increases, increasing volumes become concern often limiting factor usage. In this study, direct subsurface air injection (Air-SAT) was tested alternative long-DP operation. Six long-column experiments were conducted (2 m column) that aimed examine effect on soil's content, oxidation–reduction potential (ORP), DO concentrations, infiltrated amounts, ultimate outflow addition basic parameters, such dissolved organic C (DOC) N species, quality analysis also included examination three emerging contaminants: ibuprofen, carbamazepine, 1H-benzotriazole. Pulsed-air-injection during continuous using different operation modes (i.e., pulse durations, frequencies, airflow rates). Our results show Air-SAT doubled time infiltration possible with no downtime) allowed up 46 % higher mean rate some cases. result, 47 %–203 than conventional flooding–drying (FDO). A longer duration (60 min vs. 8 min) (∼2 L min−1 ∼1 min−1) led rate, whereas high frequency (4.5 h−1) lower compared low-frequency (24 h−1). Air good recovery ORP levels soil, especially high-frequency experiments, where steady maintained most flooding. Consequently, DOC, total Kjeldahl (TKN), ibuprofen removal values these 9 %, 40 65 those FDO, respectively. However, significant deterioration probably due enhanced biological clogging. Hence, it may be more feasible beneficial combine allowing increased while sustaining still need verified at full scale, highlight possibility minimize DP length alleviate pressure existing sites.