Technical and economic evaluation of the integration of membrane bioreactor and air-stripping/absorption processes in the treatment of landfill leachate.

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 m3 of treated leachate.

Combining yeast MBR, Fenton and nanofiltration for landfill leachate reclamation.

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, Fe2+:H2O2 molar ratio = 1:9.81 and C:H2O2 molar ratio = 1:1.14. Increased toxicity was observed with the Fenton application (EC50 = 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.

Performance evaluation of startup for a yeast membrane bioreactor (MBRy) treating landfill leachate.

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 NH3 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.