Abstract
Groundwater recharge by infiltration of urban wastewater is promising option for the sustainable urban water cycle. In this study, removal mechanism of water-soluble organic micropollutants during infiltration of sewage effluents into soil was studied through soil column experiment where secondary effluents were percolated into soil columns (20 cm i.d. × 50 cm; 20 cm i.d. × 20 cm) for 71 days at flow rate of 300 mL/hr. Concentrations of alkylphenols, bisphenol A, natural estrogens, fluorescent whitening agents (FWAs), linear alkylbenzenesulfonates (LAS), pharmaceuticals. (aspirin, ibuprofen, naproxen, mefenamic acid, ketoprofen, p-hydroxybiphenyl, triclosan, diethyltoluamide, crotamiton, carbamazepine) and estrogenic activity were measures for the column influent and eluent. Natural estrogens, octylphenol, and bisphenol . A were efficiently (≥89%) removed by the infiltration throughout the experimental period, indicating that infiltration into soil is effective for the removal of endocrine disrupting chemicals from urban reclaimed water. On the other hand, some pharmaceuticals such as crotamiton and carbamazepine showed only slight removal (approx. 20%), whereas other pharmaceuticals such as triclosan and ibuprofen were removed efficiently (≥90%). Removal mechanism was discussed in terms of hydrophobicity and biodegradability of individual compounds. The following mechanisms were suggested: ionic chemicals such as FWAs and LAS are removed by ion exchange and/or chemical precipitation reaction in soil; non or poorly ionic chemicals (EDCs and pharmaceuticals) are removed by partitioning to soil organic matter in early stage and microbial degradation in latter stage where partitioning sites are saturated.
