Phreatic zone wastewater irrigation: Sensitivity analysis of contaminant fate

“Subsurface irrigation by recharging shallow phreatic aquifers to raise the water table allows treated wastewater and other marginal water to be used in irrigation, without directly exposing crops to contaminants of emerging concern (CECs). The effects of soil and aquifer properties, environmental hydrological fluxes, irrigation parameters, and CEC biogeochemical reaction parameters, on crop and environmental contamination risks, are studied through numerical modeling. Non-biodegraded CEC solutes leave the agricultural field mostly by lateral discharge within the phreatic zone. The solute mass discharged beneath the simulated domain (potentially into deeper confined groundwater) typically represents the smallest portion of solute fate, but varied by orders of magnitude across scenarios. In contrast, other components of solute fate: the solute mass recovered by the subsurface drains, crop solute uptake, and solute mass discharged laterally within the phreatic zone are larger (in ascending order), but varied across scenarios mostly within one order of magnitude. Furthermore, solute biogeochemical reaction parameters most greatly (by orders of magnitude) affected crop solute uptake and solute discharge into the environment, followed by the hydrogeological parameters, atmospheric fluxes, and finally irrigation parameters. Hence, unfavorable biogeochemical or hydrogeological conditions cannot be mitigated by optimizing irrigation parameters. Although biogeochemical parameters affect only the partitioning of irrigated solute fate across the possible outcomes, hydrogeological parameters may also affect the irrigated solute mass, as more irrigation is needed to maintain target groundwater levels in phreatic aquifers with higher hydraulic conductivities or deeper confining layers. The irrigated solute mass strongly determines contaminant discharge to the environment, but has less effect on crop solute uptake, which is limited by crop water uptake. This study also shows that phreatic zone wastewater irrigation has crop contamination risks that are sensitive to factors different than (near-)surface irrigation techniques, and therefore contributes a meaningful alternative technique for reusing marginal water in irrigation.”

(Citation: Tang, D.W.S., van der Zee, S.E.A.T.M., Bartholomeus, R.P. – Journal of Hydrology 645(2024)art. no. 132263 – DOI: 10.1016/j.jhydrol.2024.132263 – (Open Access))

© 2024 The Author(s). Published by Elsevier B.V. This is an open access article distributed under the terms of the Creative Commons CC-BY license