Integrating electrooxidation and powdered activated carbon adsorption for removing organic micropollutants in landfill leachate: A UV254-based feedforward and feedback surrogate control strategy.

Micropollutants (μPs) in landfill leachate require effective polishing to mitigate ecological risks. This study addresses this challenge by establishing an integrated electrooxidation (EO) and powdered activated carbon (PAC) adsorption treatment, in which EO operates in continuous-flow mode and PAC adsorption in batch mode, focusing on the recalcitrant alachlor (ALA). The removal of six representative μPs was systematically evaluated in stand-alone, sequential and integrated systems. Mechanistically, experiments with μPs spiked into post-EO leachate (the sequential system) revealed that EO pretreatment reduced the competition of bulk organics for adsorption sites, thereby enhancing subsequent PAC adsorption. Based on these insights, a UV254-based surrogate monitoring framework was developed for the integrated EO+PAC system via a feedforward-feedback control strategy. A two-stage linear relationship between EO-induced UV254 reduction and PAC dosage saving (ΔPAC) enabled feedforward prediction of the required PAC dosage, while a verification logic linking the UV254 reduction in EO to that in EO+PAC provided feedback-based validation of removal efficiency, together forming a proof-of-concept feedforward-feedback control framework. Based on the experimental cost analysis, an operating point was determined at a [Formula: see text] of 1.72×10-2 Ah/m with 42 mg/L PAC, meeting the dual targets of 80% μP and 50% COD removal at an OPEX of 1.56 €/m3 with 45% ΔPAC. This study demonstrates that a single UV254 indicator can capture the multi-pathway EO degradation and guide inter-stage PAC dosing in high-salinity landfill leachate, providing a proof-of-concept basis for integrated process control.