Full-Scale Application of Up-flow High Rate Anaerobic Reactor with Substrate Modification and Effluent Recirculation for Sugarcane Vinasse Degradation and Biogas Generation

This study was aimed at studying the potential of biogas (methane) production from vinasse wastewater in real full-scale application using a two-stage sequencing Up-flow High Rate Anaerobic Reactor (UHRAR), with effluent recirculation and substrate modification. A batch experiment was initially conducted prior to the full-scale application experiment. The batch experiment was done with experimental condition variable: undiluted sample (pH 6) and diluted samples (pH: 5; 6 and 7), while pH and methane production were observed for 50 days. Full-scale application was carried out in two-stage UHRAR reactors with volume 60 m3, HRT 40 d and OLR 60.1–104 kg COD/m3•d. The observation lasted for 32 d. The result from the batch experiment showed that the diluted samples achieved higher COD degradation and methane generation than the undiluted sample. The optimum condition occurred at pH 7, with theoretical methane yield of 7.5–10.64 L CH4 per kg COD. In turn, in full scale application, at day 32, COD removal was 71% (69.1 kg COD/d removed), with methane production was 36.72 m3 CH4/d. Methane production per COD removed was 0.53 m3 CH4/kg COD•d. Substrate modification and effluent recirculation could improve the substrate biodegradability, maintain microbial diversity and enrich nutrients in the reactor.