An efficient strategy for improving short-chain fatty acid production from sludge anaerobic fermentation with calcium carbide residue addition

Calcium carbide residue (CCR), a industrial by-product generated by acetylene production, was introduced into sludge anaerobic fermentation as an alternative approach for improving short-chain fatty acid (SCFA) production. The maximum SCFA production increased by 13.52 times as the amount of added CCR increased from 0 to 0.16 g/g suspended solids (SS) and then decreased upon further increasing the CCR dosage. CCR accelerated sludge disintegration and hydrolysis to provide substantial organic material for SCFA generation. The activities of key acid-forming enzymes were simultaneously increased. Although the addition of CCR reduced the diversity of the microbial community, the methanogens were inhibited, whereas the bacteria responsible for hydrolysis and acidification (e.g., Bacilli, phylum Firmicutes) was enriched. However, the dewaterability of fermented sludge was dependent on the dosage of CCR, which deteriorated when CCR dosage exceeded 0.08 g/g SS. This study provides a robust method of treating waste by waste for enhancing SCFA production from anaerobic fermentation of waste activated sludge.