An innovative pH control strategy for alleviating membrane fouling in bipolar membrane electrodialysis during ultraviolet stabilizer production wastewater treatment

Abstract

Developing an effective resource utilization approach for ultraviolet stabilizer (UVS) wastewater is challenging due to its high-salinity and complex organic pollutants. This study employed bipolar membrane electrodialysis (BMED) to reclaim acid and base from actual UVS wastewater. To alleviate potential membrane fouling caused by specific UVS organics, an innovative two-stage pH control strategy and its mechanisms were developed. Results indicate that pH regulation is crucial for the stable operation of a 3.6 kg/d on-site pilot-scale BMED system. Under optimal conditions of current density (40 mA/cm²), initial acid-base concentration (0.02 mol/L), and initial volume ratio (2:2:1), high concentrations of 1.03 mol/L acid and 1.90 mol/L base can be reclaimed with low energy consumption. Analysis of membrane surface morphology, hydrophobicity, and resistance, along with the distribution of organic substances, shows that the two-stage pH regulation reduces fouling by probably minimizing electromigration, aggregation, hydrophobic interaction, adsorption, and deposition of humic- and tryptophan-like substances. Compared to conventional initial pH adjustments, the two-stage pH regulation approach stabilizes acid/base production while reducing process costs to $1.5/kg acid and $1.0/kg base. A life cycle cost analysis reveals that, at a BMED treatment capacity of 20 m³/d, savings of up to $774.7 thousand can be realized over a 3-year lifespan, with a relative payback period of 1.2 years. These findings highlight that BMED coupled with two-stage pH regulation is effective for the acid and base reclamation from UVS wastewater, offering a practical solution for sustainable resource recovery and achieving zero wastewater discharge.