Anaerobic Digestion Of Fruit And Vegetable Waste Based On Acidogenic Fermentation

This study focused on the anaerobic treatment of fruit and vegetable waste(FVW)to solve the problems of easy acidification,long hydraulic retention time(HRT)and low organic loading rate(OLR).In this thesis,the new idea of “FVW treatment based on the research of type of anaerobic acidogenic fermenation” was proposed and investigated.The influence of pH and OLR on distribution of anaerobic acidogenic fermentative products was investigated with FVW as substrate at different pHs(6.0,5.5,5.0,4.0)and OLR(13,20,30 gVS/(L·d)).The results showed that pH was the key controlling parameter on fermentative type.And at pH 4.0,ethanol and acetate were the predominant fermentative products taking proportion of 98.2%,which was defined as ethanol-type fermentation.The ethanol-type fermentation at pH 4.0 was further investigated to analyze the fermentative mechanism.Results showed lactate was largely produced excepet ethanol and acetate and the sum of the proportion of these three products was more than 98%.Thus this fermentation was named as ethanol(lactate)-type fermentation.In addition,Lactobaccillus was the dominant bacteria.In order to increase the efficiency of ethanol(lactate)-type fermentation,pH in the reactor was increased from 4.0 to 5.0.When glucose was used as substrate,though acidified rate largely increased,however,the fermentation type was varied from ethanol(lactate)-type fermentation to mixed acid fermentation.When FVW was used as substate,the fermentation type still maintained as ethanol(lactate)-type fermentation and the acidified rate increased.And thus variable pH controlling stategy(after ethanol(lactate)-type fermentation was stable,increased of pH from 4.0 to 5.0)could help increase the efficiency of ethanol(lactate)-type fermentation of FVW.In order to further increase VFA production,two kinds of acidogenic granular sludge of ethanol(lactate)-type fermentation and butyrate-type fermentation were successfully cultivated at upflow system reactor.And the OLR of acidogenic granular reactors of ethanol(lactate)-type fermentation and butyrate-type fermentation were high to 44.8 gCOD/(L·d)and 61.5 gCOD/(L·d).The key of controlling fermentation type was by controlling pH of effluent at 3.6±0.4(ethanol(lactate)-type fermentation)and 4.2±0.2(butyrate-type fermentation).A novel two-phase anaerobic technology of “two-phase AD based on ethanol(lactate)-type fermentation” for FVW treatment was proposed.Two configurations of CSTR-CSTR and CSTR-UASB were used to certify its possibility and superiority.The total HRT of CSTR-UASB was 3.56 d.And pilot-scale study in Qingdao kitchen waste treatment plant also indicated the possibility of this two-phase anaerobic technology.