| With the rapid development of China's economy and the accelerated process of urbanization,in recent years,the generation of urban and rural organic waste(OW)and crop straw increases significantly,and the characteristic of waste in new towns has changed obviously compared with rural and urban OW.Recently,garbage-type dry fermentation technology has been recognized by the majority of researchers in China because of its stability and applicability to the treatment of complex substrate.Garbage-type dry fermentation process,according to the way of inoculation and spray,can be divided into single-phase technology and two-phase process.Two-phase garage fermentation is more efficient and stable than single-phase garage fermentation.In this paper,the methane production potential of corn straw and organic waste is 216.79±27.21mL/gVS and 264.45±43.72mL/gVS,respectively.And in the subsequent experiments for different spray process conditions are studied,including leachate recirculation spray ratio(Leachate to Substrate Ratio,L/S),spray intensity,inoculation of solid digestate under different spray intensity and spray pattern(interval and continuous spray),to explore the effect of the above spray conditions on VFA and biogas production in the two-phase garage-type dry fermentation process.The major research results are as follows:(1)The effect of Spraying: On the one hand,it contributes to increase the contact opportunity between microorganisms and substrate,to adjust the moisture content of substrate,and to promote mass transfer.At the same time,spraying increases the amount of microorganisms in substrate,which contributes to achieve the inoculation of substrate,to speed up the decomposition of substrate,to accelerate the Volatile fatty acids(VFA)and the generation of methane.(2)The results of different L/S spray show that the effect of hydrolysis and acidogenesis of substrate is higher than that of methanogens under the condition of higher L/S spray,however,under low spray L/S,spray is not conducive to the VFA accumulation,and the inhibition of methane bacteria is not obvious,thus more conducive to methane fermentation.(3)Under low L/S spray condition,the results of different spray intensity show that the spray intensity has little effect on the production of VFA under the low L/S spray,but relatively speaking,the smaller the spray intensity,the less the VFA generation,the lower the accumulation and inhibition,the higher the methane production rate.With the increase of spray L/S,the stimulating effect of spray intensity on the hydrolysis and acidogenesis increases,and the greater is the spray intensity,the easier is to promote the formation and accumulation of VFA,thereby theactivity of methane bacteria is inhibited whichresults in a lower biogas production.(4)Under different spray conditions,the results of addition of solid digestate show that VFA generation decreases obviously,the time of returning to normal VFA/TIC is shorter than without the addition of solid digestate.Inoculation with solid digestate can counteract the inhibition of VFA accumulation on methane fermentation under the high intensity of spray.Under the low spray intensity,with or without addition of solid digestate does not show a significant effect on the biogas production,which indirectly proves that the spray can play a similar inoculation effect as the addition of solid digestate under low spray intensity.Increasing of spray intensity appropriately can promote biogas production under the condition of solid digestate inoculation.(5)The results of spray pattern show that the continuous spray pattern promotes the production of VFA in high L/S spray condition.This study further shows that the spray L/S,spray intensity and spray pattern are important factors that affect VFA production in the garage-type dry anaerobic fermentation system. |
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