Comparative Experimental Study of Mesophilic and Thermophilic Batch Fermentation Process of Vegetable Waste
The rapid and harmless treatment of vegetable waste has been a"bottleneck"in the development of the plateau summer vegetable industry.In view of the instability of the anaerobic fermentation process in the existing large-scale treat-ment plants of vegetable waste,and the lack of study on thermostatic fermentation processes both domestically and interna-tionally.Comparative experiments of mesophilic and thermophilic batch anaerobic fermentation were conducted in two 0.56 m3 thermostatic fermentation tanks.The experiments compared the biogas production,ammonia nitrogen concentration,pH value,and changes in total dissolved solids(TDS)during both processes,meanwhile,the modified Gompertz equation was used to analyze the methane production process by thermostatic anaerobic fermentation.The results showed that during the 30 day batch anaerobic fermentation process with the inoculum concentrations of 30％and the total solid(TS)content of 2.2％,both mesophilic and thermophilic fermentation processes could proceed stably,the fitting results of the modified Gompertz equation were all in coincident degree with R2 greater than 0.99.The cumulative biogas production and methane production of the thermophilic group were 3939 L and 2034.2 L,which were 11.3％and 15.5％higher than that of the mesophilic group;at the same time,the time for the methane volume fraction of the thermophilic group to reach 50％was advanced by 3 days compared with that of the mesophilic group.The lowest pH values corresponding to the mesophilic and thermophilic test groups were 6.66 and 6.52,respectively,and gradually increased and stabilised at about 7.30 in the later stage.The concentration of ammonia nitrogen in two test groups continued to fluctuate after a rapid increase in the early stage,and the thermophilic group was greater than that of the mesophilic group on the whole.This experimental study provides a refer-ence for the stable,rapid and harmless large-scale treatment of vegetable waste by using thermostatic anaerobic fermentation.
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