Response surface modelling of Fenton pre-treatment of slaughterhouse sludge for enhanced anaerobic digestion

Abstract

Abstract Slaughterhouse sludge, a byproduct of meat processing, poses significant environmental risks if not properly treated, with potential impacts including water contamination and land pollution. Anaerobic digestion (AD) of this high-organic-content sludge offers a sustainable solution by facilitating biogas production, reducing reliance on fossil fuels, and enabling resource recovery. However, the complex nature of sludge necessitates pretreatment to enhance its biodegradability. In this study, the Fenton process, utilizing hydroxyl radicals (•OH) for oxidative breakdown of organic matter, was employed to improve the digestibility of slaughterhouse sludge. A response surface methodology (RSM)-based optimization approach, specifically the central composite design (CCD), was applied to investigate the effects of key operational parameters—pH, ferrous ion (Fe2+) dosage, and hydrogen peroxide (H2O2) dosage—on sludge disintegration. The response variables analyzed were soluble chemical oxygen demand (sCOD) and volatile suspended solids (VSS) reduction. The optimal conditions were identified as a Fe2+ dosage of 7.2 mg/g total solids (TS), a H2O2 dosage of 130.4 mg/g TS, and a pH of 3. Under these conditions, sCOD and VSS degradation increased by 37.5% and 40.5%, respectively, resulting in a 31% increase in methane yield over a 20-day AD period compared to untreated sludge. These findings demonstrate that Fenton pre-treatment enhances the biodegradability of slaughterhouse sludge, thereby improving the efficiency of AD and contributing to more sustainable waste management practices.