Abstract
Anaerobic digestion (AD), being the most effective treatment method of waste activated sludge (WAS), allows for safe disposal. The present study deals with the electro-Fenton (EF) pretreatment for enhancing the WAS biogas potential with low-cost iron electrodes. The effect of pretreatment on the physicochemical characteristics of sludge was assessed. Following EF pretreatment, the pH, conductivity, soluble chemical oxygen demand (SCOD), and volatile fatty acids (VFA) increased to 7.5, 13.72 mS/cm, 4.1 g/L, and 925 mg/L, respectively. Capillary suction time (CST) analysis highlighted the dewaterability effect of EF on WAS, as demonstrated by the decrease in CST from 429 to 180 s following 30 min of pretreatment. Batch digestion assays presented an increase in the biogas yield to 0.135 L/g volatile solids (VS) after 60 min of EF pretreatment in comparison to raw sludge (0.08 L/g VS). Production of biogas was also found to improve during semi-continuous fermentation of EF-pretreated sludge conducted in a lab-scale reactor. In comparison to raw sludge, EF-pretreated sludge produced the highest biogas yield (0.81 L biogas/g VS) with a high COD removal rate, reaching 96.6% at an organic loading rate (OLR) of 2.5 g VS/L. d. Results revealed that the EF process could be an effective WAS disintegration method with maximum recovery of bioenergy during AD.
Highlights
Municipal wastewater treatment holds an important role in environmental concerns since wastewater discharges have greatly evolved in quantity and quality during recent decades
Conductivity increased to 13.72 mS/cm
The present study has highlighted the effect of EF pretreatment on the efficiency of disintegration and anaerobic digestion (AD) of sludge
Summary
Municipal wastewater treatment holds an important role in environmental concerns since wastewater discharges have greatly evolved in quantity and quality during recent decades. Activated sludge process is the main effective method used for treatment of municipal wastewater and leads to the production of large quantities of waste activated sludge (WAS) This residue, composed of cellular biomass (20–40%), refractory organic matter (40–60%), and mineral matter (10–30%), contains various minerals, organic micropollutants, and pathogenic organisms which can be potentially harmful for the environment and present genuine management problems [1]. With such environmental and economic concerns, there is growing interest focusing on the reduction in volume and stabilization of WAS [2].
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