Resource recovery from sugarcane vinasse by anaerobic digestion - A review.

The increase in biofuel production by 2030, driven by the targets set at the 21st United Nations Framework Convention on Climate Change (COP21), will promote an increase in ethanol production, and consequently more vinasse generation. Sugarcane vinasse, despite having a high polluting potential due to its high concentration of organic matter and nutrients, has the potential to produce value-added resources such as volatile fatty acids (VFA), biohydrogen (bioH2) and biomethane (bioCH4) from anaerobic digestion. The objective of this paper is to present a critical review on the vinasse treatment by anaerobic digestion focusing on the final products. Effects of operational parameters on production and recovery of these resources, such as pH, temperature, retention time and type of inoculum were addressed. Given the importance of treating sugarcane vinasse due to its complex composition and high volume generated in the ethanol production process, this is the first review that evaluates the production of VFAs, bioH2 and bioCH4 in the treatment of this organic residue. Also, the challenges of the simultaneous production of VFA, bioH2 and bioCH4 and resources recovery in the wastewater streams generated in flex-fuel plants, using sugarcane and corn as raw material in ethanol production, are presented. The installation of flex-fuel plants was briefly discussed, with the main impacts on the treatment process of these effluents either jointly or simultaneously, depending on the harvest season.

Evaluation of fouling mechanisms in nanofiltration as a polishing step of yeast MBR-treated landfill leachate.

The aim of this study was to evaluate the nanofiltration process as a polishing step of a membrane bioreactor inoculated with commercial baker yeast (Saccharomyces cerevisiae) used to treat sanitary landfill leachate. The contaminants retention and influence of concentration polarization and fouling phenomena on the permeate flux decline (FD) at different operating pressures were analysed. The greatest total flux reductions of 63.57% and 70.83% were observed for the lowest and the highest pressures, respectively, being this reduction attributed mainly to the concentration polarization. Membrane itself and concentration polarization phenomena were the main resistances to the nanofiltration process. Hermia model adjustment to the experimental data revealed that cake formation was the main mechanism that explained the FD at pressures of 8, 10 and 12 bar. At recovery rates above 40%, there was a significant decrease in permeate quality, so this value was chosen as the viable value for the proposed system. Integrated MBR-nanofiltration system led to the high removal of pollutants and made the treated effluent feasible for reuse in the landfill itself.

Comparison of commercial baker's yeast versus bacteria-based membrane bioreactors for landfill leachate treatment.

This study compares the performance of the membrane bioreactor (MBR) inoculated with commercial baker's yeast (Saccharomyces cerevisiae) (MBRy) versus one inoculated with bacterial sludge (MBRb) for treatment of landfill leachate. The MBRb and MBRy were operated with a hydraulic retention time of 48 h, solids retention time of 60 d, and specific air demand based on membrane area of 0.6 m3 h-1 m-2. The MBRy was more efficient in removing chemical oxygen demand (COD) (68 ± 12%), color (79 ± 8%), ammoniacal nitrogen (58 ± 18%), and phosphorus (62 ± 19%) compared to MBRb, which showed removal efficiencies of 44 ± 18%, 46 ± 20%, 45 ± 17%, and 29 ± 15% for COD, color, ammoniacal nitrogen, and phosphorus. Furthermore, the MBRy had lower production of soluble microbial products, which are the main cause of membrane fouling, and so a lower membrane fouling potential. The average hydraulic permeability of the MBRy (32.23 L m-2 h-1 bar-1) was about four times higher than that of the MBRb (8.34 L m-2 h-1 bar-1). Thus using commercial baker's yeasts as a MBR inoculum can enhance pollutants' removal and membrane performance.