Anaerobic digestion of sugarcane vinasse in anaerobic membrane bioreactor

Abstract

Vinasse, a by-product of sugarcane processing, is a source of nutrients such as calcium, magnesium and potassium. For that reason, its main destination is the fertigation. However, vinasse has high concentration of solids and organic matter, acidity and a high sulfate content, which can affect the productive quality of the soils. Therefore, the previous treatment of vinasse before its use in fertigation is desirable. Anaerobic biodigestion is an alternative for reducing the polluting organic load and, simultaneously, for recovering of bioenergy, due to the generation of biogas by such process. However, improvements in the application of the anaerobic treatment of vinasse are still necessary to enable the production of bioenergy in large scale, since vinasse is generated in large quantities and it has high concentrations of organic matter and sulfate. The main reactors used in anaerobic processing of vinasse are of high rate reactors, in which the sludge granulation process is indispensable for the success of the treatment. Presence of recalcitrant compounds, high levels of solids, high acidity or high alkalinity, salinity, high temperatures, can affect the process of granule formation, and causing washing of the biomass. For this reason, Anaerobic Membrane Bioreactor (AnMBR) must be considered for the treatment of vinasse, since the granulation of sludge is not required, and the greater retention of biomass allows the application of greater organic loads. In this study, the AnMBR with attached external membrane is proposed for the treatment of vinasse. The configuration allows the use of reactors already used in anaerobic treatment with polishing the membrane. Complete biomass retention can be achieved by using AnMBR due to the ultrafiltration modules, so it is possible to obtain a complete retention of all microorganisms, especially those responsible for the degradation of specific pollutants and allows to obtain a better effluent quality, without solids in suspension compared to conventional anaerobic processes. This technology represents an innovation for the treatment of wastewater, however more research using this reactor configuration and different types of effluents is needed. In the case of vinasse, studies reported in the literature that address the treatment of sugarcane vinasse using AnMBR are still scarce. If successful, this work hopes to further contribute to the dissemination of this technology, especially in Brazil. (AU)