Safe Reuse of Treated Wastewater: Accumulation of Contaminants of Emerging Concern in Field-Grown Vegetables under Different Irrigation Schemes
Qingyang Shi, Dahang Shen, Rebecca Yates, C.J. Chou, Andrea Barajas, Jing Jing Zhang, Daniel Schlenk, Jay Gan
Abstract
The reuse of treated wastewater (TWW) for irrigation alleviates freshwater (FW) scarcity while supporting a circular economy. However, the potential human exposure to contaminants of emerging concern (CECs) through plant accumulation is a significant barrier. Currently, knowledge on CEC contamination of edible produce and effective mitigation strategies for the safe reuse of TWW is limited, particularly under field conditions. This study examined the accumulation of a representative set of CECs, including perfluoroalkyl and polyfluoroalkyl substances (PFAS), pharmaceuticals and personal care products, and tire wear particle (TWP) chemicals, in radish, lettuce, and tomato under three irrigation practices: FULL (continuous TWW irrigation), HALF (midseason switch from TWW to FW), and FW-only. Despite low PFAS concentrations (8.1-25.7 ng/L) in TWW, the plant uptake was consistently observed, including in tomato fruits. Alternating TWW with FW significantly reduced CEC accumulation in edible tissues, particularly for compounds with short half-lives, with reductions up to 82.4% even for persistent PFAS. For most CECs and plant species, edible tissue concentrations were similar between the HALF and FW treatments. These findings demonstrate the on-farm applicability of simple irrigation modifications to reduce food contamination and contribute to the promotion of safe reuse of nonconventional waters.