Anaerobic co-digestion of wastes from fruit processing and activated sludge reactor in juice production industry

Abstract

Anaerobic co-digestion of wastes from fruit processing wastes (FPW) and activated sludge reactor (WAS) were studied in a semi-continuous digester at 30-32 °C during 193 days. The best results of biogas yield and volumetric biogas production were 635.4 L·kg−1 total volatile solids (TVS) fed and 473.9 L·m−3·d−1, respectively, obtained when FPW:WAS ratio applied was 1:1 and retention time was 40 days. Biogas yield and volumetric biogas production increased 210% and 357%, respectively, when FPW:WAS ratio was changed from 0:1 to 1:1; and hydrolysis was also improved since TVS removal efficiency achieved nearly 75%. The microbiological analysis of samples taken at day 70, 135 and 168 supported these results with increased FPW:WAS ratio. Both the relative abundance of methanogens and hydrolytic bacteria were observed to increase significantly; in the case of hydrolysis, the percentage of Chloroflexi relative abundance increased from 17% at day 70 to 50% at day 168.