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A membrane bioreactor inoculated with commercial baker's yeast (Saccharomyces cerevisiae) (MBRy) integrated to an air-stripping/absorption (AS/AB) as pre-treatment (aiming ammonia recovery) or a post-treatment (polishment step) was assessed for the landfill leachate treatment. The effect of chemical oxygen demand (COD) and nitrogen (N) ratio (C:N) on the performance of the MBRy was also investigated. At high COD/N ratio, high organic matter removal in terms of COD (71 ± 4%) and ammonia removal (97 ± 3%) was observed. Lower COD/N ratio favored yeast growth in the mixed liquor even under adverse conditions. The results of ammonia removal and recovery, and economic analysis demonstrated that the best way to integrate the AS/BS processes is as pre-treatment of MBRy. The ammonia concentration in the AS/AB process feed was a key factor to achieve the market specification. Although pH and temperature adjustment were adequate to promote ammonia removal/recovery, the AS operation at high temperatures showed the highest ammonia removal rate (99%). Therefore, the integration of AS/AB with MBRy allows obtaining a permeate with a final concentration of 2902 ± 374 mg L -1 of COD and 9 ± 7.5 mg L -1 of ammonia. Although it was possible to reach the Brazilian discharge standard for ammonia (20 mg L -1 ), it was not possible to reach the standard for COD, where the remaining fraction is recalcitrant organic matter, requiring the integration of a physico-chemical process. It should be noted that the proposed route allowed recovery 7 kg of ammonia per m 3 of treated leachate., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

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 (bioH 2 ) and biomethane (bioCH 4 ) 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, bioH 2 and bioCH 4 in the treatment of this organic residue. Also, the challenges of the simultaneous production of VFA, bioH 2 and bioCH 4 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., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

This study investigated the best way to combine nanofiltration (NF) and Fenton with membrane bioreactor inoculated with Saccharomyces cerevisiae (MBRy) for the treatment of landfill leachate, aiming at compliance with legislation and water reuse. Firstly, the permeate from MBRy was treated by Fenton process followed by NF (MBRy - Fenton - NF). Another alternative evaluated was the polishment of MBRy permeate by NF and treatment of NF concentrate by Fenton process (MBRy - NF - Fenton (concentrate) ). COD removal in the Fenton step was optimized according to central composite design (CCD) and 85.5% removal was obtained at pH = 3, Fe 2+ :H 2 O 2 molar ratio = 1:9.81 and C:H 2 O 2 molar ratio = 1:1.14. Increased toxicity was observed with the Fenton application (EC 50  = 2.45%). The NF showed the best performance treating the MBRy permeate. High permeate flux (8.9 ± 1.6 L h -1 m -2 ) and ion rejection (82 ± 4.2%), and low membrane fouling was observed in this condition. Although both NF permeate presented potential for reuse, the final COD concentration was lower in the MBRy - Fenton effluent (88 mg L -1 ). The Fenton application for the NF concentrate was able to remove 87.24% of COD. With a preliminary economic analysis, it was verified that the MBRy - NF - Fenton (concentrate) combination is the most advantageous due to the lower chemical reagent and membrane area requirements. Thus, this route presents itself as an alternative for landfill leachate reclamation., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The necessity for landfill leachate treatment is a requisite to reduce the environmental impact related to municipal solid waste landfills and different aspects must be considered while deciding for an appropriate treatment process. For example, it was demonstrated that the landfill leachate stabilization in tropical regions is achieved right after its first year of operation, requiring technologies capable of treating leachates of a higher recalcitrant character if compared to those leachates from temperate regions and same landfill age. In view of its complexity and variability, stand-alone processes (either biological or physicochemical) are often ineffective in attaining the threshold values for its discharge in receiving bodies. Due to that fact, full-scale facilities have adopted integrated routes, harvesting the benefits of both biological and physicochemical processes. The implementation of membrane bioreactors followed by polishing membrane separation process (nanofiltration and reverse osmosis) seems to be a trend in leachate treatment by full-scale treatment plants. This technology is widely employed in China, European countries, and tropical countries as Brazil, generally with a treatment cost lower than the costs related to its disposal in domestic effluent collection systems. From the technologies already employed by full-scale facilities, four integrated routes were proposed for a sensitive analysis considering the treatment of a landfill leachate of different physicochemical characteristics. From all routes, those employing the membrane separation process as a polishing step had a better efficacy in attaining the threshold values for leachate disposal, being that an interesting alternative for leachate polishing by full-scale facilities., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The startup process of a membrane bioreactor inoculated with yeast biomass (Saccharomyces cerevisiae) and used in the treatment of landfill leachate was evaluated. The yeast membrane bioreactor (MBRy) was inoculated with an exogenous inoculum, a granulated active dry commercial bakers' yeast. The MBRy was successfully started up with a progressive increase in the landfill leachate percentage in the MBRy feed and the use of Sabouraud Dextrose Broth. The membrane plays an important role in the startup phase because of its full biomass retention and removal of organic matter. MBRy is a suitable and promising process to treat recalcitrant landfill leachate. After the acclimation period, the COD and NH 3 removal efficiency reached values of 72 ± 3% and 39 ± 2% respectively. MBRy shows a low membrane-fouling potential. The membrane fouling was influenced by soluble microbial products, extracellular polymeric substances, sludge particle size, and colloidal dissolved organic carbon.