Long-term evaluation of membrane bioreactor inoculated with commercial baker’s yeast treating landfill leachate: pollutant removal, microorganism dynamic and membrane fouling Gabriela C. B. Brito, Liséte C. Lange, Vera L. Santos, Míriam C. S. Amaral and Wagner G. Moravia ABSTRACT In this study, commercial baker’s yeast (Saccharomyces cerevisiae) was employed as a novel inoculum for a membrane bioreactor (MBRy). It was applied to landfill leachate (LFL) treatment to remove recalcitrant organic compounds as well as for the assimilation of recalcitrant compounds, since yeasts have a high ability to break such compounds down. The MBR was inoculated with 10 g L 1 of commercial baker’s yeast and was operated at a hydraulic retention time of 48 h and pH of 3.5. The specific air demand based on the membrane area (SADm) was maintained at 0.6 m 3 h 1 m 2 . The MBRy achieved chemical oxygen demand (COD), color, NH 3 , and humic substances removal of 68, 79, 68, and 50%, respectively. Furthermore, the MBRy showed lower fouling potential, which can be attributed to the low extracellular polymeric substances production, as the formation of a cake layer was the major mechanism of membrane fouling. The work demonstrated that novel MBR is a promising technology for treating recalcitrant landfill leachate. Gabriela C. B. Brito Liséte C. Lange Míriam C. S. Amaral Department of Sanitary and Environmental Engineering, Universidade Federal de Minas Gerais, Antônio Carlos Av. 6627, ZIP 31270-901, Belo Horizonte, Minas Gerais, Brazil Vera L. Santos Department of Microbiology, Universidade Federal de Minas Gerais, Antônio Carlos Av. 6627, ZIP 31270-901, Belo Horizonte, Minas Gerais, Brazil Wagner G. Moravia (corresponding author) Departments of Environmental Science and Technology, Federal Center of Technological Education of Minas Gerais, Amazonas Av. 5253, ZIP 30421-169, Belo Horizonte, Minas Gerais, Brazil E-mail: moravia@cefetmg.br Key words | baker’s yeast, fouling, landfill leachate, membrane bioreactor, recalcitrant compounds INTRODUCTION Landfill leachate (LFL) is a complex mixture of inorganic and organic compounds. It is generated through the precipi- tation, infiltration, compaction, and degradation of waste mass at landfill sites (Kjeldsen et al. ). Leachate is characterized by high concentrations of biological oxygen demand (BOD), chemical oxygen demand (COD) and nitro- gen, especially in the form of ammonium. It may also contain heavy metals, xenobiotic compounds, phenols, and other aromatic hydrocarbons (Lee et al. ). The synergis- tic, additive or antagonistic effects of the contaminants present in the leachate may lead to toxicity, carcinogenicity or estrogenicity (Kumari et al. ). Thus, the intensive use of biological treatments alone is insufficient to treat the LFL effluent to the standards required by the legislation (Kurniawan et al. ). Membrane bioreactors (MBR), can operate with a high concentration of biomass and sludge retention time, as the membrane allows the complete retention of sludge in the bioreactor, resulting in a more efficient biological degradation system (Boonyaroj et al. ). Alvarez-Vazquez et al. () compared the MBR to conventional biological treatment of LFL, concluding that the MBR, in general, has a higher COD removal efficiency for older leachate. Similarly, Ahmed & Lan () conducted a review on the use of MBR in the treatment of leachate from landfills. Their findings suggest that excellent removal of BOD and ammonia (over 90%) was achieved with low hydraulic retention time (HRT) and high organic load, compared to conventional biological systems. The COD removal efficiency ranged from 23 to 90%, mainly 398 © IWA Publishing 2019 Water Science & Technology | 79.2 | 2019 doi: 10.2166/wst.2019.067 Downloaded from http://iwaponline.com/wst/article-pdf/79/2/398/616527/wst079020398.pdf by guest on 15 September 2022