Evaluating the effectiveness of adding chicken manure in the anaerobic mesophilic co-digestion of sewage sludge and wine distillery wastewater: kinetic modelling and economic approach

Abstract

Anaerobic digestion (AD) has been extensively investigated to obtain energy from chicken manure (CM). However, CM has a high total and volatile solids (TS and VS) content, making wet AD unsuitable for treatment due to high levels of water consumption and large digester volumes. Previous studies have shown that anaerobic co-digestion (AcoD) of sewage sludge and wine distillery wastewater (SS:WDW) resulted in lower methane production (MP) values than those obtained in AD of SS alone due to the lower VS content of the WDW. The present study was carried out to address these challenges. AcoD of SS:WDW:CM is proposed here for the first time as an effective new alternative for managing three wastes in one and the same digester. To achieve this goal, different proportions of SS:WDW:CM (50:50:0; 49:49:2; 47:47:6; 44:44:12 w/w/w) were considered. Increasing the proportion of CM resulted in an increase both in MP (from 3.3 to 11.5 L CH4/L reactor) and SMP (from 197 to 229 L CH4 /kg VS), along with high organic matter removal rates (% TCODr = 60 ± 3 % and % VSr= 64 ± 3 %). However, it also resulted in a reduced methane rate (from 0.116 to 0.045 d-1) and a longer lag phase (from 0.394 to 3.199 d) due to the high amount of non-soluble organic matter in the CM. Optimal conditions were 44:44:12 (w/w/w) SS:WDW:CM, which resulted in removal rates of %VSr = 60%, SMP = 229 L CH4/kg VS, MP= 11.5 L CH4/L reactor and methane productivity (at 30 days) = 0.38 L CH4/L reactor/d.