Effect Of Intermediate Covers On Anaerobic Bioreactor Landfill Stabilization

The production of municipal solid waste（MSW）is enormous and shows a rising trend. Andlandfill technology is the widest method to deal with MSW. In order to overcome theshortcomings of slow refuse degradation speed in traditional landfill, bioreactor landfilltechnology was proposed and anaerobic bioreactor has the highest utilization. The intermediatecover layer is an important part of anaerobic bioreactor landfill, which accounted for10~20%ofthe volume. Research on selection and design of intermediate covers holds great significance toaccelerate the degradation of refuse，and advance the in situ treatment of leachate and promotethe recycling of solid waste. The thesis, from this point of view, studies the effect of differentintermediate covers on anaerobic bioreactor stabilization.Five kinds of different intermediate covers were designed in this thesis, named as: dewateredsludge+waste incineration fly ash, dewatered sludge+natural zeolite, mineralized refuse+waste incineration fly ash, mineralized refuse+heavy calcium carbonate, mineralized refuse+Waste Incineration Fly Ash+natural zeolite+heavy calcium carbonate, respectively. Six sets ofsimulation anaerobic bioreactor landfills were established to study waste degradation processesand leachate properties, and investigate the effect of intermediate covers on anaerobic bioreactorlandfill stabilization.The results show that intermediate covers can optimize the environment in anaerobic reactorlandfills, promote the growth of microorganisms and accelerate landfill stabilization process.Intermediate covers composed of Dewatered sludge+waste incineration fly ash or mineralizedwaste+Waste incineration fly ash can promote the waste degradation，advance the conversionand the removal of organic matter in leachate and accelerate the stability of anaerobic bioreactorlandfill. The intermediate covers mainly affect the hydrolytic acidification stage of wastedegradation process, promote the hydrolysis acidification bacteria growth, accelerate thehydrolysis acidification of waste and improve the conversion of organics in leachate. Analysis ofwaste and leachate properties indicated that all the reactors are in the transitional period fromacidification phase to methane fermentation phase, most of the organic matters in the refuse havebeen transferred to leachate.Intermediate cover materials can promote refuse degradation and organic matter transformation,the order is dewatered sludge> mineralized refuse> Waste Incineration Fly Ash> heavy calcium carbonate> natural zeolite. The intermediate covers composed of dewatered sludge and naturalzeolite can promote the degradation and transformation of nitrogen components of the waste, butthe intermediate covers composed of mineralized refuse, waste incineration fly ash, naturalzeolite and heavy calcium carbonate are counterproductive. The presence of intermediate coversare conducive to maintain the temperature and the optimum moisture in the reactors. MSWI flyash, mineralized refuse and heavy calcium carbonate can enhance the leachate alkalinity and pH,whereas natural zeolite oppose. The intermediate cover composed of dewatered sludge andmineralized refuse is advantageous to promotion organic matter of refuse hydrolysis andtransformation to leachate. The intermediate covers contained zeolite or calcium carbonate caneffectively control the ammonia nitrogen and total nitrogen concentrations in the leachate, butmay also have a negative effect on degradation of the waste.