Effect of hydraulic retention time on the methanogenic step of a two-stage anaerobic digestion system from sewage sludge and wine vinasse: Microbial and kinetic evaluation

• Published in: Fuel (Guildford) 2021-07, Vol.296, p.120674, Article 120674
• Main Authors: Tena, Miriam, Perez, Montserrat, Solera, Rosario
• Format: Article
• Language: English
• Subjects: Acidification; Anaerobic digestion; Anaerobic microorganisms; Archaea; Continuously stirred tank reactors; Correlation coefficient; Correlation coefficients; Fatty acids; Hydraulic retention time; Hydraulics; Methane; Methane production; Microorganisms; Refuse as fuel; Retention; Retention time; Sewage sludge; Sludge digestion; Substrates; Thermophilic microorganisms; Two-stage system; Vinasse; Volatile fatty acids; Wine; Wine vinasse
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2021.120674

•The effect of HRT on CH4 production from sewage sludge and wine vinasse was studied.•The highest CH4 production (159.35 mL CH4/g CODremoved) was achieved at HRT 4 days.•The maximum Archaea activity (11.55·10-9 L CH4/cells) was achieved at HRT of 4 days.•The effect of HRT on the effluent substrate concentration was modelling kinetically.•HRT of 4 days is the optimal time for the methanogenic step of codigestion of SS:WV. The aim of this study was to investigate the effect of hydraulic retention time on methane production in the methanogenic step of a two-stage thermophilic-mesophilic anaerobic digestion system. The methanogenic step was carried out in a continuously stirred tank reactor under mesophilic conditions. The methanogenic digester was fed with a mixture consisting of 50% sewage sludge and 50% wine vinasse previously acidified in a thermophilic acidogenic step. Eight hydraulic retention times (20, 16, 10, 6, 5, 4, 3 and 2 days) were tested to determine the effect of each operational variable. Maximum methane production (1.8 L/LR·d) was reached at a hydraulic retention time of 2 days, whereas maximum methane yield (159.4 mL CH4/g CODremoved) and Archaea activity (11.6·10-9 L CH4/cells) were achieved at a hydraulic retention time of 4 days. From this time onward, an accumulation of volatile fatty acids took place, reaching values of over 1000 mg/L. Although the Stover-Kincannon model is more suitable to predict the chemical demand oxygen concentration in the effluent, both the Grau Second-order and Stover-Kincannon models adequately describe substrate removal in the methanogenic step of an anaerobic digestion system with a high correlation coefficient (R2 > 0.996).