Modeling carbamazepine transport in wastewater-irrigated soil under different land uses

Authors: FILIPOVIC, LANA - University Of Zagreb; FILIPOVIC, VILIM - University Of Zagreb; WALKER, CHARLES - Pennsylvania State University; Williams, Clinton; GALL, HEATHER - Pennsylvania State University; WATSON, JOHN - Pennsylvania State University

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2020
Publication Date: 5/3/2020
Citation: Filipovic, L., Filipovic, V., Walker, C.W., Williams, C.F., Gall, H., Watson, J.E. 2020. Modeling carbamazepine transport in wastewater-irrigated soil under different land uses. Journal of Environmental Quality. 49(4):1011-1019. https://doi.org/10.1002/jeq2.20074.
DOI: https://doi.org/10.1002/jeq2.20074

Interpretive Summary: The reuse of sewage effluent for irrigation is an effective way to dispose of treated wastewater while protecting surface waters from contamination. Carbamazepine is a persistent anti-epileptic drug found in wastewater effluent. The research objective was to model the movement and persistence of carbamazepine in soils with different land uses. Results suggest that movement of carbamazepine in surface soils is related to organic carbon content and that models overestimated the observed mobility and that augmenting soil organic matter content could be used to limit carbamazepine mobility.

Technical Abstract: The pharmaceutical compound, carbamazepine (CBZ), is a contaminant of emerging concern because of its frequent detection and persistence in the environment and its potential to negatively impact non-target aquatic and terrestrial organisms. Wastewater irrigation can serve as a long-term, frequent source of CBZ to the environment; therefore, understanding the fate and transport of CBZ as a result of wastewater reuse practices has important environmental implications. The objective of this study was to estimate long-term soil transport of CBZ originating from treated wastewater irrigation on plots under different land uses by combining field measurements, laboratory experiments and numerical modeling. Previous field and modeling research found elevated CBZ levels in soil under forested, grassland, and cropped land uses. Field data from a previous study comparing CBZ concentrations in soil under different land uses were used in numerical modeling with HYDRUS 2D/3D for the estimation of CBZ soil transport during 20 years of irrigation with treated wastewater. This study showed high CBZ retention in soil under all investigated land uses. Adequate modeling results were obtained by using soil organic carbon-water partitioning coefficient (Koc) for the CBZ linear sorption coefficient (Kd) estimation, yet an underestimation of CBZ concentration in soil was still noted. Thus, results suggest that, although highly important, organic carbon content is probably not the only soil property governing CBZ sorption at this site. Modeling results showed that irrigation with wastewater containing CBZ for 20 years increased the CBZ concentration in the soil profile and its vertical movement, with the slowest vertical transport rate occurring on the forested plots. Overall results suggest that a beneficial management practice could be to increase soil OC (e.g., by compost addition) when using treated wastewater for irrigation in order to retain CBZ in the surface soil, and thus limit its leaching through the soil profile.