Slide 1Municipal Solid Waste (MSW)MSW managementCharacteristics of MSW in US (2005)LandfillLeachateAnaerobic digestionEffects of leachate recirculation on organic compounds removalEffects of leachate recirculation on organic compound removalSlide 10Accelerated biodegradationSlide 12Methane production and methane contentEffects of leachate recirculation on metal concentrationEffects of leachate recirculation on metal concentrationMetal concentration in leachateMetal concentration in MSWSlide 18Study in full-scale landfillsBOD and BOD:COD & TimepH & TimeMetal concentration in leachateGas flow rate (production rate)DisadvantageNH3-N & TimeDisadvantageRecirculation StrategiesRecirculation StrategiesThanks and QuestionsEffects of leachate recirculation on anaerobic treatment of municipal solid wastebyChayanon SawatdeenarunatMunicipal Solid Waste (MSW)Municipal Solid Waste (MSW)Predominantly household wasteThe addition of commercial wastewhich are collected by a municipality within a given area.MSW managementCharacteristics of MSW in US (2005) Food waste 9.8%Yard trimming 9.6%Paper & paper board 39.6%Glass 4.7%Metal 7.8%Plastic 11.2%Wood 6.6%Total MSW generated 340 million tonsLandfillis a site for the disposal of waste materials by burial and is the oldest form of waste treatmentLeachateis the refuse from landfillsThe compositions vary regarding the age of each landfills and characteristics of MSWHigh COD, sulfate and metal ionAnoxic, acidicAnaerobic digestionEffects of leachate recirculation on organic compounds removalConventional landfillsWashed outBio-conversionBioreactor landfillsAccelerated bio-conversionEffects of leachate recirculation on organic compound removalWhat are the benefits of leachate recirculation on organic compound removal?Increase moisture contentEnhance hydrolysis stageEnhance contact between organic compounds and microorganismRecirculate organic compoundsRecirculate methanogen microorganismReach stabilization more rapidlyAccelerated biodegradationEffects of leachate recirculation on landfill gas production and methane contentMethane production increase in recirculating landfillsThe acceleration of organic compounds removalsReturn organic compoundsImprove methanogenic activitiesMethane content is not significantly changeHigh recirculation rateCause acid accumulation inhibit methanogen microorgsnismReduce methane production rateMethane production and methane contentEffects of leachate recirculation on metal concentrationMetal precipitationIn the beginning (acidogenesis stage) pH is between 4 and 6 High solubility of metalReach stabilization (methanogenesis stage)pH is between 7 and 9 Metal sulfide and metal hydroxide precipitateMetal concentration in MSWHigher due to the accumulation of precipitated metalEffects of leachate recirculation on metal concentrationConventional landfillsNeed longer time to reach methanogenesis stageRemove less metal from leachate when compared with bioreactor landfills at the same timeBioreactor landfillIncrease contact between waste and leachateRemove metal from leachate more effectivelyMetal concentration in leachateMetal concentration in MSWOther mechanisms of metal removal from leachateSubsequent capture within waste metrix by encapsulationSorptionIon-exchangefiltrationStudy in full-scale landfillsProperties of landfill facilitiesBOD and BOD:COD & Time• reach methanogenesis stage within 6 yearspH & TimeMetal concentration in leachate• Metal concentration is below standard within 13 yearsGas flow rate (production rate)•About 60% higher in bioreactor landfillsDisadvantageAccumulation of NH3-NLeakage of Nitrification bacteriaNH3 + O2 → NO2− + 3H+ + 2e− NO2− + H2O → NO3− + 2H+ + 2e− Leachate should be pre-aerated off site before recirculationNH3-N & TimeDisadvantageAccumulation of Cl- in leachateRecirculation StrategiesThe balance of biological process and hydraulic capacity of the wasteRecirculate slowly before reaching methanogenesis stage To prevent acid stuck which could inhibit methanogen bacteriaTo prevent bacteria washed out Initiated as soon as possible following waste placementTo ensure the appropriate moisture content of biodegradationRecirculation StrategiesLeachate should be recirculated uniformlyTo prevent short circuitingTo Increase contact between leachate and MSWThanks and