Modelling of the anaerobic semi-continuous co-digestion of sewage sludge and 2 wine distillery wastewater

Abstract

The semi-continuous mesophilic anaerobic co-digestion of sewage sludge and wine distillery wastewater was investigated. In this sense, the effects of reducing hydraulic retention time (HRT, from 20 d to 8 d) on the degradation of organic matter and methane production were determined. The experimental results showed that anaerobic co-digestion enhanced the biodegradability of the mixture in terms of VS and CODt (7-8% higher) for HRT = 8 d. The methane productivity at HRT = 8 d (18.0 LCH4/kgVS·d), was also enhanced (30% higher) than those obtained in the control experiment. In addition, a mathematical kinetic model was proposed to determine the rate-limiting step of the process. Stoichiometric parameters obtained for SS:WDW (0.115 kgCH4/kgCOD) was higher than SS (0.094 kgCH4/kgCOD), which means that co-digestion increased the rate of consumption because more amount of biodegradable compounds. Kinetic study showed that anaerobic co-digestion favoured methane production rate enhancing the acetate consumption step and making methanogenesis the rate-limiting step in this process.