Short-chain fatty acids from lysis liquid of residual sludge anaerobic fermentation enhanced by microbial electrolysis

Abstract

Sludge lysis liquid is a highly concentrated solution containing macromolecular organic matter produced during thermal hydrolysis of sludge. Anaerobic digestion is commonly used to achieve degradation conversion and resource recovery. However, during the thermal conversion process, the presence of refractory organic matter such as Melad reaction products can result in low anaerobic conversion efficiency and methane yield. To address the issue, this study proposes a method for the intensive treatment and resource recovery of sludge lysis liquid using a microbial electrolysis-assisted anaerobic digestion (ME-AD) system. The study aimed to investigate the degradation efficacy of macromolecular organic matter and the conversion efficiency of short-chain fatty acids (SCFAs). The results of the study showed that the direct treatment of raw lysis liquid with ME-AD improved the anaerobic degradation efficiency compared to the usual treatment, which involved a 5-fold dilution of lysis liquid. The COD removal rate was 40.2% in the renewal batch cycle, which was 15.6% higher than the conventional anaerobic conversion. Additionally, the complex organic matter in the intensively degraded sludge lysis liquid was converted to SCFAs, which were produced at a maximum concentration of 40.0×10^5 mg/L during the fifth day of intensive anaerobic fermentation. Among the SCFAs, acetic acid had the highest percentage at 68.1%. This study provides a new approach to address the treatment of sludgelys is liquid and utilization of sludge resources.

Keywords

• residual sludge
• microbial electrolysis
• anaerobic fermentation
• short-chain fatty acids
• refractory organic matter