Enhanced methane yield through sludge two-phase anaerobic digestion process with the addition of calcium hypochlorite

This study investigated the effects of calcium hypochlorite (Ca(ClO) 2 ) on biomethane generation from sludge two-phase anaerobic digestion system. In first (acidogenic) phase, volatile fatty acids (VFAs) were largely generated when pretreated by Ca(ClO) 2 , while the methane yield was severely inhibited. In second (methanogenic) phase, the methane yield was observably enhanced by Ca(ClO) 2 . Further calculation showed that the total methane yield from the two phases was firstly promoted from 156.0 ± 4.5 to 269.9 ± 5.2 mL when Ca(ClO) 2 dosage enhanced from 0 to 1.6 g/L, which then reduced to 235.4 ± 5.5 mL when Ca(ClO) 2 content reached 2.0 g/L. Mechanism analysis showed that the suppression of Ca(ClO) 2 on coenzyme F 420 activity was relieved in methanogenic phase, and the abundances of functional microbes in methanogenic phase were enriched when added with Ca(ClO) 2 . The Ca(ClO) 2 -based method well realized the balance between efficacy and economy, possessing outstanding potential for large-scale applications.