Zerovalent iron-sand filtration can reduce the concentration of multiple antimicrobials in conventionally treated reclaimed wastewater

Authors: KULKARNI, PRACHI - University Of Maryland; RASPANTI, GREG - University Of Maryland; BUI, ANTHONY - University Of Maryland; BRADSHAW, RHODEL - University Of Maryland; KNIEL, KALMIA - University Of Maryland; CHIU, PEL - University Of Maryland; Sharma, Manan; SAPKOTA, AMIR - University Of Maryland; SAPKOTA, AMY - University Of Maryland

Submitted to: Environmental Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2019
Publication Date: 2/10/2019
Citation: Kulkarni, P., Raspanti, G., Bui, A., Bradshaw, R., Kniel, K., Chiu, P., Sharma, M., Sapkota, A., Sapkota, A.R. 2019. Zerovalent iron-sand filtration can reduce the concentration of multiple antimicrobials in conventionally treated reclaimed wastewater. Environmental Research. https://doi.org/10.1016/j.envres.2019.02.012.
DOI: https://doi.org/10.1016/j.envres.2019.02.012

Interpretive Summary: Zero-valent iron (ZVI) filtration is an emerging technology for use on small-scale farms to improve irrigation water quality. Reclaimed wastewater provides a potential source of irrigation water in areas where surface or well-water may not be available or of sufficient quality to use on crops intended for human consumption. An emerging concern for the use of reclaimed water in irrigation has been the presence of antibiotics to which humans may be exposed to through consumption of fresh fruits and vegetables. The research presented here investigates the use of zero-valent iron (ZVI) filtration to improve the water quality of the reclaimed wastewater with respect to reducing residual antibiotic concentrations in reclaimed wastewater. Using a gravity-fed ZVI filter set- up, ZVI-filtration was able to significantly reduce the concentrations of eight out of twelve antimicrobials present in reclaimed wastewater. Furthermore, the ZVI-filtered reclaimed wastewater met the recommended guidelines for agricultural irrigation with respect to nitrate, salinity and inorganic elements. The results of this research show that ZVI-filtration may improve the quality of reclaimed wastewater for use in agricultural irrigation on small-scale, diversified farms. This research will benefit small-scale farmers by demonstrating a cost-effective filtration solution which can improve the chemical quality of non-traditional irrigation water.

Technical Abstract: Irrigation with reclaimed water is increasing in areas that lack access to, and infrastructure for, high-level treatment and distribution. Antimicrobial residues are known to persist in conventionally treated reclaimed water, necessitating the investigation of reuse site-based mitigation options to further reduce these contaminants. We examined the effectiveness of a 50% volume:volume, particle matched, micro-scale zerovalent iron (ZVI)-sand filter in reducing concentrations of mixtures of antimicrobials present in pH-unadjusted conventionally treated reclaimed water. Twelve antimicrobials (azithromycin, ciprofloxacin, erythromycin, linezolid, oxacillin, oxolinic acid, penicillin G, pipemidic acid, sulfamethoxazole, triclocarban, tetracycline and vancomycin) were quantified using high performance-liquid chromatography-tandem mass spectrometry in reclaimed water, and ZVI-sand filtered reclaimed water, in a two-month long greenhouse-based experiment. Data were analyzed using a non-parametric rank-based approach. ZVI-sand filtration significantly reduced concentrations of azithromycin, ciprofloxacin, oxolinic acid, penicillin G, sulfamethoxazole, linezolid, pipemidic acid and vancomycin. Azithromycin, the antimicrobial with the highest median concentration (320 ng/L), was reduced to below the limit of detection after ZVI-sand filtration. Inorganic element (antimony, beryllium, cadmium, chromium, iron, lead, selenium and thallium) and water quality (free and total chlorine, nitrates, nitrites, pH and total dissolved solids) analyses showed that ZVI-sand filtered reclaimed water quality (nitrate, salinity, and inorganic elements) met the recommended guidelines for agricultural irrigation with reclaimed water. Based on our initial results, ZVI-sand filtration may be a promising basis for a point-of-use filtration system for reclaimed water irrigation on small-scale farms.