Evaluation of a Recirculating Hydroponic Bed Bioreactor for Removal of Contaminants of Emerging Concern from Tertiary-Treated Wastewater Effluent

Abstract Tertiary effluent from a municipal wastewater treatment plant in Tucson, AZ, was added to light expanded clay aggregate (LECA)-filled, recirculating hydroponic bed bioreactors for 10 days. Bioreactors were planted with high and low densities of sorghum (Sorghum bicolor), switchgrass (Panicum virgatum) and Bacillus thuringiensis cotton (Gossypium sp.). The experiment also included a non-planted bioreactor treatment and a control bioreactor with neither plants nor substrate medium. Of 46 emerging contaminants assayed with liquid chromatography tandem mass spectrometry (LC-MS/MS), 16 were initially identified at detectable levels. After one day, Ibuprofen and Diphenhydramine were removed below detection limits in all treatments. After five days, initial concentrations of atenolol, benzotriazole, carbamazepine, hydrochlorothiazide, iohexol, iopamidol iopromide, primidone, sulfamethoxazole and tris TCPP were reduced by greater than 80% in all treatments, while the control exhibited little to no removal. Diclofenac, simazine and sucralose exhibited variable removal rates among treatments ranging from 44-84% after five days. After 10 days, concentrations of DEET, diclofenac, iopromide, primidone and simazine were all below detection levels, while there was near zero removal in the control. Bioreactors planted with cotton had significantly more removal of sulfamethoxazole than unplanted bioreactors by 16-19% after five days and 18-20% more removal after 10 days. The percentage uptake of benzotriazole by every planted treatment was significantly higher than the non-planted treatment after five and 10 days. Significant contaminant removal occurred in the media substrate, likely through adsorption to LECA or microbial degradation. More research is needed to examine specific pathways of degradation and removal by various microbials and plants.