The pulp and paper industry is one of the leading contributors to industrial wastewater pollution, discharging effluents rich in recalcitrant organic compounds such as lignin and cellulose. These pollutants significantly increase chemical oxygen demand (COD), biological oxygen demand (BOD), color, and toxicity in aquatic ecosystems, posing serious environmental and public health threats. Addressing these challenges, this study systematically investigates and optimizes three advanced electrochemical treatment technologies Electrocoagulation (EC), Electro-Fenton (EF), and a sequential EC/EF hybrid process for the treatment of real wastewater from a tissue paper production facility in Hashtgerd Industrial Park, Iran.
A key innovation in this research is the integration of a cathode–anode automatic switching system, designed to prevent passive oxide layer formation on electrode surfaces. This switching strategy enhanced electron transfer efficiency, extended electrode lifespan, and reduced water consumption for electrode cleaning by over 50%. To achieve maximum treatment efficiency, Response Surface Methodology (RSM) with Central Composite Design (CCD) was employed for process optimization, focusing on variables such as pH, current density, reaction time, and H₂O₂ concentration (in EF). Under optimized conditions, the COD removal efficiencies were 64% (EC), 72% (EF), and 92.9% (EC/EF).
A comprehensive Life Cycle Assessment (LCA) following ISO 14040 and ISO 14044 guidelines was conducted using SimaPro v9.2 and the ReCiPe 2016 (H) methodology, evaluating environmental impacts across midpoint and endpoint categories. Results indicated that global warming, terrestrial ecotoxicity, and fossil resource depletion were the most affected categories, primarily driven by energy use. The CO2-equivalent emissions per kilogram of COD removed were 36.06 kg (EC), 20.7 kg (EF), and 19.94 kg (EC/EF). Endpoint human health impacts ranged from 894 mPt (EC) to 528 mPt (EC/EF). Sensitivity a