| Due to the enormous differences from cities in terms of geographical environment,social environment and economic conditions in China,rural areas cannot mechanically apply the existing processing scheme of municipal solid waste.Nowadays,it is very necessary and urgent to develop a set of economical and feasible technology which is applicable to the rapid and stable processing of solid waste in rural areas.According to the current situation garbage disposal in rural areas,this paper set up three kinds of landfill schemes suitable for popularizing in underdeveloped rural areas,namely,anaerobic bioreactor landfill,semi-aerobic bioreactor landfill and anaerobic-semi-aerobic bioreactor landfill.The three landfill schemes were compared and selected by expert scoring and group analytic hierarchy process.The results indicated that anaerobic-semi-aerobic bioreactor landfill was most suitable for popularizing in rural areas.On this basis,we carried out the laboratory comparison and simulation experiments of anaerobic,semi-aerobic and anaerobic-semi-aerobic bioreactor landfills.This paper explored the degradation,migration and transformation mechanism of major pollutants in anaerobic-semi-aerobic bioreactor landfill,and analyzed the change rules of solid phase,liquid phase and gas phase indexes.Moreover,the operation strategy of anaerobic-semi-aerobic bioreactor landfills was explored.Based on analytic hierarchy process,important index screening method and the theory of fuzzy comprehensive evaluation,the fuzzy comprehensive evaluation model was established to evaluate the stabilization of anaerobic-semi-aerobic bioreactor landfills.(1)On the basis of GAHP principle,the three schemes of anaerobic landfill,semi-aerobic landfill and anaerobic-semi-aerobic landfill were compared and selected from the four perspectives of economical efficiency,social influence,environmental influence and technological innovation.The total hierarchy weight of the three schemes is(0.3128,0.3364,0.3508)T,and the precedence order is D3,D2,and D1.The anaerobic-semi-aerobic landfill is more suitable to be popularized in rural areas.(2)The decrease ranges of BDM,total nitrogen,combustible components and Organic Matter in anaerobic bioreactor landfill R1,semi-aerobic bioreactor landfill R2,anaerobic unit R3-? and semi-aerobic unit R3-? of anaerobic-semi-aerobic bioreactor landfill were 33.28%?61.99%,25.71%?54.29%,12.38%?48.65%and 27.60%?50.16%.The moisture contents of waste in the four landfill units were maintained in the range of 65%?75%.High moisture content is conducive to microbial metabolism.The removal rate of COD by R2,R3-? and R3-? was greater than 95%,while the removal rate by R1 was only 34.00%.The removal effects of ammonia nitrogen by R3-? and R3-? were between R1 and R2.The concentration of Fe in the leachate of each unit is R1,R3-?,R3-? and R2 in descending order.The concentration of Fe and Mn had a significantly correlation with COD and pH.The general variation trends of the volume fraction of CO2,CH4,N2 and in R1 and R3-?were coincident.(3)After the experiment was completed,the settling volumes of in the four landfill units R1,R2,R3-? and R3-? occupied 16.63%,31.00%,17.75%and 28.78%of the total landfill height.The cumulative settling volume in the anaerobic unit increased logarithmically with the landfill time.The cumulative settling volume in semi-aerobic unit increased linearly with the landfill time.(4)In anaerobic-semi-aerobic bioreactor landfill,anaerobic units and semi-aerobic were connected in series,forming a space structure integrating aerobic zone,facultative anaerobic zone and anaerobic zone.The type and quantity of microorganisms in the landfill system were enhanced.The pollutants can circulate with the leachate in the three zones.A series of biochemical reactions occurred under the combined action of a variety of microorganisms,which accelerated the stabilization of landfill.(5)Through the visual analysis and variance analysis,the optimal conditions in the acid production stage were as follows:recharge frequency was 3d/time,cross recharge ratio was 75%,the pH value of leachate was adjusted to 8.0,and no aeration was conducted in the leachated.The optimal conditions in the methane production stage were:recharge frequency was 1d/time,cross recharge ratio was 50%,recharge rate was 15 mL/min,pH value of the leachate was not regulated.(6)The solid phase index BDM,organic matter,liquid phase index COD and settling rate can characterize the stabilization of landfill.After the landfill for 100d,the anaerobic units of the landfill entered into a completely anaerobic state,and the values of the four core indexes decreased exponentially with time.After the landfill for 480d,the stabilization degree of anaerobic-semi-aerobic bioreactor landfill was basically stable.The research results of this paper can provide theoretical basis and technical support for the rapid and stable technology of household waste in rural areas. |
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