Study On Stabilization Rules And Mechanism Of Solid Waste In Spatiotemporally Anaerobic/Semi-Aerobic Bioreactor

In China,sanitary landfill is still the main waste disposal method in quite a long time in the future.However,it has caused increasingly serious secondary pollution of solid waste due to the unreasonable design and construction,as well as poor operation and management of sanitary landfills.Especially in rural areas,a large amount of solid waste is discarded or simply buried on account of the waste treatment facilities deficiency.Plenty of researches have shown that bioreactor landfill technology is particularly suitable for small and medium-sized rural solid waste treatment for its advantages such as short operation cycle and large potential of resource utilization,which could provide a new approach for the treatment and disposal of rural solid waste.However,different types of bioreactor landfills have their own superiorities and deficiencies.How to make full use of the superiorities of various bioreactors and overcome the disadvantages of various bioreactors is still needed to be further studied.In order to adapt to the treatment of rural solid waste,a spatiotemporally anaerobic/semi-aerobic bioreactor(STASAB)was proposed based on the full use of advantages of anaerobic and quasi-aerobic bioreactors.STASAB combines anaerobic with aerobic operation in time(single reactor goes through anaerobic and aerobic stage successively)and space(Leachate of anaerobic and semi-aerobic phase in different reactor was mixtured and recharged),and further optimizes and improves the sequentially anaerobic/semi-aerobic bioreactor(SASAB)processing technology,research shows that:(1)In the quasi-aerobic stage of STASAB and SASAB,through evaporation,the total leachate production decreased linearly due to evaporation.Without considering rainfall infiltration,STASAB and SASAB could achieve zero discharge of leachate after 3 to 5 months.(2)By combining anaerobic with quasi-aerobic operation in time,STASAB could raise the pH value of leachate in the bioreactor to alkalinity in the quasi-aerobic stage.By the combination of anaerobic with quasi-aerobic operation in space,microbial inoculation and pH regulation in the start-up phase of the bioreactor could be realized simultaneously.The results showed that the pH value of the bioreactor leachate in the hydrolytic acidification phase of STASAB was always higher than 6.88,and the duration of the hydrolytic acidification phase was only 1/3 of SASAB.After entering the methane generation stage,the pH value was also always maintained at about 8.0.It inferred that STASAB can effectively solve the accumulation of organic acids in the anaerobic stage,and significantly shorten the acid inhibition time,which could realize the rapid startup of the anaerobic methane generation stage.(3)Leachate mixed and recharged in STASAB provides sufficient connection among insoluble substance,soluble nutrient and anddifferent microorganisms,which stimulates the activity of microorganisms and increases the diversity of microorganisms,so as to achieve the purpose of rapid degradation of organic matter.At the same time,the mixed leachate of different concentrations have dilution effect,which could reduce the inhibitory effect generated by excessive toxic and harmful substances.The experiment showed that the COD concentration peak of STASAB was 39440 mg/L,only about 1/2 of SASAB.(4)On the one hand,STASAB makes full use of the highly efficient denitrification function of the quasi-aerobic bioreactor and removes the ammonia inhibition in the anaerobic fermentation process.On the other hand,leachate mixed and recharged provides sufficient nutrients for the semi-aerobic later stage,removes inhibition of the C/N ratio imbalance on denitrification effect.The experiment showed that the leachate TN removal rate of the semi-aerobic bioreactor units in STASAB reaches 92.3%~95.5%,and even in anaerobic biological reactor unit,TN removal rate of leachate reached 49.4%.And TN concentration peak of leachate in STASAB is 1461 mg/L,which is only about half of the SASAB.(5)STASAB can effectively promote the startup and yield of methane production stage.Experiments showed that the startup time of gas production peak period is only about 1/3 of SASAB.Moreover,the duration of gas production peak period of STASAB was about twice as long as that of SASAB,and the total gas production was 43% higher than it.(6)Leachate produced from biological reactor in different stages of STASAB(hydrolytic acidification,methanogenesis,and quasi-aerobic)was mixed and recharged,which can realize pH regulation,microbial inoculation,nutrient addition,pollutant dilution and other effects at the sametime,thus promoting the degradation of landfill waste.