Insights into modified sequencing batch reactor for the treatment of sugarcane vinasse: role of recirculation process

The application of the recirculation process in the biological wastewater treatment process was considered as an effective approach in promoting biomass retention and mixing intensity, enhancing the performance of treating wastewater. In this study, a recirculated sequencing batch reactor (R-SBR) was developed in the treatment of anaerobically digested vinasse. The comparative study of the conventional sequencing batch reactor (without recirculation process) and R-SBR was determined through the treatment performances and kinetic studies. The chemical oxygen demand and ammonium reduction of R-SBR (52.5 ± 8.0% and 31.7 ± 7.9%) were higher than the conventional sequencing batch reactor (31.8 ± 4.3% and 17.3 ± 5.3%) at the feed flow rate of 1.0 L/day. This result revealed that the enhancement of the mass transfer between activated sludge and substrate could improve the biodegradation of the R-SBR. Moreover, the effect of feed flow rate as a significant factor to achieve effective biodegradation was determined in the R-SBR system. The maximum chemical oxygen demand reduction (63.0%) and ammonium reduction (41.3%) of R-SBR were achieved at the lowest feed flow rate (1.0 L/day) from 1.0 to 5.0 L/day. The chemical oxygen demand reduction of R-SBR could be explained by using pseudo-first-order kinetics with rate constant (k) (0.0356 day). The kinetic study revealed that the R-SBR achieved the most effective performance at the lowest feed flow rate. Thus, the recirculation process as a feasible process improved the treatment performance in the R-SBR system at low feed flow rate.