Feasibility of Fenton-based oxidation for reducing organic content, toxicity, and carbon footprint of automotive industry wastewater

Abstract Automotive industry wastewater, particularly from the cataphoresis process, presents a challenge due to its high chemical oxygen demand and heavy metal content. Biological treatment alone is often insufficient, requiring pretreatment to enhance biodegradability. Fenton oxidation effectively targets toxic compounds, reducing inhibition of biological process. This study evaluates the feasibility of Fenton, Fenton-based, and photo-Fenton oxidation for pretreating automotive industry wastewater, aiming to optimize chemical oxygen demand removal and minimize sludge formation. Experimental studies using Response Surface Methodology revealed that Fenton and Fenton-based oxidations achieved similar chemical oxygen demand removal efficiencies, although the Fenton-based process with ferric iron produced more sludge. Photo-Fenton oxidation did not provide any significant benefit. Inhibition tests showed Fenton pretreatment reduced sludge inhibition from 44 to as low as 9% under optimal conditions. The optimal operating conditions for classical Fenton oxidation were determined as a ferrous iron concentration of 0.58 g L −1 , a hydrogen peroxide to chemical oxygen demand molar ratio of 0.58 mol mol −1 , and a reaction time of 30 min, resulting in a 49.58% chemical oxygen demand removal with minimal sludge formation and activated sludge inhibition. Compared to the coagulation-flocculation process, Fenton oxidation demonstrated the potential to reduce the carbon footprint by 6.6–16.6%, based on carbon dioxide emissions from chemical consumption. Therefore, classical Fenton oxidation as a pretreatment process can enhance biological treatment efficiency and lower the carbon footprint of automotive industry wastewater treatment. Graphical abstract