Performance Of Two-Phase Anaerobic Co-Digestion Of Fruit And Vegetable Waste And Kitchen Waste

As the representative of the city of organic garbage, kitchen waste(KW) made a huge yield in China as well as vegetable waste (FVW). Otherwise, KW and FVW could produce high quality biomass energy as raw materials. In consideration of their characteristics, two-phase anaerobic digestion as a targeted process was adopted to treat biomass waste effectively and produce biomass energy at the same time. So it was a promising and key treatment of high moisture content of urban organic garbage with economic benefits and environmental benefits.Research of acidification phase and methanation phase of the two-phase anaerobic digestion was made. As raw material at acidification phase, KW and FVW’s mixing ratio was8:5on wet weight. At35℃,45℃,55℃,30gTS·L-1,40gTS·L-1,50gTS·L-1and60gTS·L-1acidification load, F/M=4, and acidification time10days, the following conclusion was made:The optimal conditions obtained by acidification of batch method is45℃60g TS·L-1. Under this condition, it could retain the advantages of35℃and55℃at the acidification phase with SCOD reaching1100mg·g-1TS, VFA to300mg·g-1TS, which compared with the beginning of the reaction were increased by50%and150%.On the basis of batch experiment, C/N and F/M effect on the acidizing experiment, separate kitchen and fruit acid acidification effect experiment, and the limit load conditions experiment were launched. Under conditions about C/N=15and C/N=25, F/M=2and F/M=4, performed on60gTS·L-1(45℃), the conclusions were made. C/N=25experiment could reduce the product quality with glucose as carbon source. The acidification rate was60%lower than the not-regulate C/N. So C/N didn’t have obvious promotion to the acidification phase.Acid production of mixing feedstocks one increased by70.7%than separate feedstocks one. The mixing feedstocks one could be stable pH in4.2-4.6, and improved hydrolytic acidification ability of separate feedstocks one.Under conditions about60gTS·L-1(45℃), batch acidification experiment about F/M was launched. F/M=4:pH could steady in4.2-4.6at the short time. Although the total VFA of F/M=2was slightly higher than the F/M=4one, its hydrolysis efficiency was lower than the later one.What was more, propionic acid of F/M=2one was up to4850mg·L-1. So condition of F/M=4had more advantage than F/M=2one at acidification phase.In limit load experiment,80gTS·L-1one had a large quantity of VFA production (33250mg·L-1), but it had lower acidification quality than60gTS·L-1one. The20gTS·L-1one produced a small amount of VFA (8263mg·L-1).80gTS·L-1one could meet the requirement of hydrolysis acidification, though the one’s hydrolysis acidification effect was worse than60gTS·L-1one.A research of the relationship between the acid load and hydraulic retention time was made with continuous stirred tank reactor (CSTR). At the conditions about acid loading rate12gVS·L-1·d-1,9days as hydraulic residence time could keep64354mg·L-1VFA total amount and46.9%proportion of ethanol and48.1%proportion of acetic acid respectively, which had obvious advantages in acidification. Hydrolysis rate was high at lOgVS·L-1·d-1and10days HRT, and the12gVS·L-1·d-19days HRT and14gVS·L-1·d-18days HRT possession advantage on producing acid amount.Based on acidification experiments, batch methanation experiments were launched on lOgVS·L-1,15gVS·L-1and20gVS·L-1load (35℃)respectively. Three different components of the acid as raw material, and under different parameters of two F/M inoculation method for parameters, got that the initial methane phase of high acetic acid and ethanol content would guarantee the continuous gas production and methane content at methane phase. High butyric acid content made the methane gas production peak earlier with the peak of emergence on2-3days. F/M was closer to0.5, the cumulative gas production was larger with high ethanol and acetic acid content as material. Butyric acid with high content should be controlled F/M between0.6-1.0.The conclusion of sequencing batch methane stable operation conditions was4gVS·L-1·d-1as stable load, and the maximum was up to4.5gVS·L-1·d-1,4gVS·L-1·d-1methane phase volumetric gas production rate was up to3.13L·L-1, steadied in2.0L·L-1. There are73.8%and83.5%for TS and VS removal rate.