Sewage sludge management and enhanced energy recovery using anaerobic digestion: an insight

Abstract

Sewage sludge (SS) is a potential source of bioenergy, yet its management is a global concern. Anaerobic digestion (AD) is applied to effectively valorize SS by reclaiming energy in the form of methane. However, the complex floc structure of SS hinders hydrolysis during AD process, thus resulting in lower process efficiency. To overcome the rate-limiting hydrolysis, various pre-treatment methods have been developed to enhance AD efficiency. This review aims to provide insights into recent advancements in pre-treatment technologies, including mechanical, chemical, thermal, and biological methods. Each technology was critically evaluated and compared, and its relative worth was summarized based on full-scale applicability, along with economic benefits, AD performance improvements, and impact on digested sludge. The paper illuminates the readers about existing research gaps, and the future research needed for successful implementation of these approaches at full scale. HIGHLIGHTS AD offers sustainable sludge management by harnessing energy recovery.; Pre-treatment approaches for enhanced hydrolysis during AD.; Challenges and recent advances during sludge pre-treatments are discussed.; Further research on detailed characterization after pre-treatment is required.; The future outlook for pre-treated sewage sludge digestion has been discussed.;

Keywords

• anaerobic digestion
• bioenergy
• hydrolysis
• sewage sludge
• sludge pre-treatment