Treatment of mature landfill leachate in tropical climate using membrane bioreactors with different configurations

This study describes the collection of landfill leachate from seven sites in different climatic zones of Sri Lanka and characterizes the landfills through the analyses of leachate quality. Membrane bioreactors (MBRs) with different configurations were employed to treat some of those leachates. An aerobic MBR (AMBR) system was operated in three Phases. In the first Phase, an AMBR alone, in the second Phase an anaerobic reactor followed by an anoxic reactor and an AMBR and in the third Phase an anoxic reactor followed by an AMBR were operated. In Phases I and II, the sludge retention time (SRT) and the hydraulic retention time (HRT) were kept at infinite (as no intentional wasting of sludge was made) and 96 h; in Phase III, the SRT was varied from 60, 30, 20 to 10 days and under each SRT, the HRT was varied from 96, 48, 24 and 12 h. The optimum operating conditions for the configuration used in Phase III was established through extensive experiments which had a SRT. The three MBR configurations removed more than 93%, 64.8% and 59% of BOD5, COD and total nitrogen respectively. They also removed large amounts of slowly biodegradable substances and nitrogenous compounds other than NH4+, NO3− and NO2−. Relationships between SRT and MLSS as well as SRT and fouling rate of membrane have been found. The study illustrates the capabilities of MBR in treating landfill leachate. [Display omitted] •Leachate collected from seven landfill sites covering 3 climatic zones in Sri Lanka.•They were characterized as mature leachate based on the analyses.•A laboratory scale MBR system was optimised for treating the actual leachate.•SRT of 60 days and HRT of 24 h were found to be the optimum.•MLSS and membrane fouling rate were related to SRT.•Slowly biodegradable substances and nitrogenous compounds can be removed by the MBR.