Two wastes into one resource: Carbide slag-driven anaerobic fermentation of excess sludge towards short-chain fatty acids recovery

The anaerobic fermentation has been regarded as promising technology for short-chain fatty acids (SCFAs) recovery from excess sludge. Despite that various treatment approaches have been developed, the sustainable waste utilization of carbide slag in enhancing anaerobic fermentation has rarely been reported. It demonstrated that the carbide slag-derived alkaline condition dominantly contributed to triggering extracellular polymeric substance disruption and microbial cell lysis by protein molecule deconstruction. Considerable sludge hydrolysis was facilitated owing to extracellular and intracellular organic matter release, solubilizing 14.73 % of total solid organic matters in 4-h treatment. Correspondingly, massive SCFAs of 2219.70 mg COD/L (mainly acetate) were produced through 8-day anaerobic fermentation, with the improved acidification and the inhibited methanogenesis. Approximately 83.03-96.21 % of the recoverable SCFAs were extracted after sludge conditioning and solid-liquid separation, providing remarkable economic benefit of 196.23 CNY/ton VSS and carbon-emission reduction of 0.069-0.347 ton CO2/ton VSS. The findings proposed an innovative and sustainable carbide slag driven anaerobic fermentation strategy for SCFAs recovery and waste stabilization, with low heavy metal residual and negligible environmental risks in "two wastes into one resource" pattern.