Emerging organic contaminants in soil irrigated with effluent: electrochemical technology as a remediation strategy

Abstract

The effluent reuse for soil irrigation is foreseen as a possible strategy to mitigate the pressure on water resources. However, there is the risk of potential accumulation in soil of emerging organic contaminants (EOCs). In the present work the electrokinetic remediation (EKR) technology, use of direct current, was applied for the removal of EOCs from a soil irrigated with effluent. For this, a soil collected from a rice field (located in Portugal) was mixed with spiked effluent to simulate flood irrigation in one time-period. The experiments were carried out for 6 days applying a low current intensity of 2.5 mA. Different current strategies were tested: continuous mode, reversed electrode polarization (REP), On/Off time periods, and the combination of the last two. The target EOCs comprises a list of six pharmaceuticals and personal care products widely detected in treated wastewater. This study showed that once introduced in soil through effluent irrigation, 20-100% of the EOCs were still present in the soil after 6 days. EKR enhanced up to 20% of the EOCs removal when comparing with control (without current). The EOC removals showed to be related to the microcosm location (anode, central or cathode sections) and dependent of EOCs characteristics. Soil characteristics did not change when On/Off system was combined with REP as a current strategy, and a more homogenous removal of the studied EOCs was achieved in the tested conditions. EKR showed to be a promising technology to be applied in EOCs contaminated soils, not only for removal purposes, but also to avoid possible dispersion in the environment.

Keywords: Effluent reuse; Electrochemical oxidation; Pharmaceuticals and personal care products; Soil irrigation.