Anaerobic Treatment and Biogas Production of Raw Leachate from Fresh Market Waste Composting by an Anaerobic Hybrid Reactor

Raw leachate discharged from composting process is considered as a promising feedstock for biogas production with high potential for renewable bioenergy recovery. In order to prevent environmental concerns relating to the composting disposal, anaerobic digestion could be a good practice for treatment and utilizing the wastewater derived from fresh market waste composting facilities. The aim of this study was to examine an anaerobic hybrid reactor performance on organic content reduction and biogas production from the raw leachate. The preliminary study included the examinations on leachate characteristics and biochemical methane potential (BMP) assay. In the pilot study, a 200-liter anaerobic hybrid reactor with a combination of an upflow sludge bed reactor and a filter reactor was set-up and was operated semi-continuously with the raw leachate collected from a fresh market waste composter as feedstock. The prior test results showed that the leachate contains high COD and BOD as 34,500 mg L⁻¹ and 14,800 mg L⁻¹, respectively. An extensive data on BMP tests indicated that the leachate could be anaerobically digested and generated biogas with the conversion rate as 0.48 L g⁻¹ of COD removed of fed leachate. Average methane content in the biogas was approximately 60%. Similar results were achieved in an observation of the anaerobic hybrid reactor performance for 100 days. The reactor was operated efficiently with hydraulic retention time higher than 10 days and maximum organic loading rate as 8 kg COD m⁻³ day⁻¹. However, H2S content in the biogas was higher than 5,000 ppm which required further H2S clean-up before utilizing biogas as an alternative fuel.