The Effect On Methane Production In Two-Phase Anaerobic Digestion Of Food Waste By Adding Municipal Solid Waste Incineration Bottom Ash

With the constant expansion of city scale and the rapid growth of population,the contradiction between economic development and ecological environment is becoming more and more serious,especially,the problem of waste disposal is particularly prominent,and the urgent need to improve.As the constructions of urban waste treatment facilities tend to centralized,the urban environmental protection industrial park has been formed gradually.In the park,due to high content of easily biodegradable ingredients,food waste can be hydrolyzed rapidly and it possibly leads to the accumulation of volatile fatty acid(VFA)during the anaerobic digestion(AD),especially the propionic acid which restricts the efficiency improvement and stable operation in AD.Solid Waste Incineration(MSWI)has developed recently,since more and more MSW are yielded.As a consequence,the annual production of bottom ash(BA),as a by-product,from the power plants increases greatly.BA management and utilization is becoming an important issue to consider in daily operation of power plants.However,limitations have been found in the traditional utilization of BA in Building materials.With a good performance of alkaline slow-release,the BA can be used as the alkaline conditioner in aicd inhibition of AD to enhance the system's buffering capability and increase the Methane production.This thesis mainly studied the feasibility of using BA in two-phase anaerobic digestion of food waste,including the effect on methane production in two-phase AD of food waste by adding BA and the effect of effluent recirculation and oganic loading rate on two-phase anaerobic digestion of food waste.The main experimental content are as follows:(1)The various amounts of BA(0?1%?2%?3% and 5%)as the addition agent are input into the acidogenic reactor,under certain organic loading,the effects of BA on the acidogenic and methanogenic gas production and system stability during the two-phase AD of food waste were studied.(2)Taking food waste as a single raw material,different effluent recirculation and organic load rate(OLR)were set up.The effects of the recirculation and OLR on methane yield and the characteristics of two-phase AD were investigated to explore the optimum parameters of two-phase AD of food waste.In this paper,the main conclusions are follows:(1)The results showed that BA could significantly accelerate the acidification and increase the pH value in the acidogenic reactor.The VFA concentration in the acidogenic reactor loading with 2% BA was 11257.51 mg/L,increasing by 28.36% compared to the control reactor.The total methane yield in the AD process loading with 2% BA was 478.98 mL/g VS,which was 32.60% higher than the control reactor.This work indicated that BA could accelerate the acidification in the acidogenic phase and increase the methane yield in the methanogenic phase.Besides,adding BA helped to improve the stability of methanogenic reactor and the biogas slurry accorded with the safety standard of water-soluble fertilizer.(2)The results showed that effluent recirculation could significantly increase the pH value of acidogenic reactor and accelerate the acidification.The concentration of VFA was 14967.64 mg/L when the recirculation rate was 50% at the 11.33 g VS/(L·d)of OLR,increased 40.74% by the CK,respectively.And the effluent recirculation had a significant effect on the efficiency of methane production at the 8.50 g VS/(L·d)of OLR;the efficiency of methane production of effluent recirculation rate of 50% on average was 486.14mL/g VS,which was 29.84% higher than the CK.Under the condition of non-recirculation,the optimum organic loading rate of methanogenic reactor was 6.38 g VS/(L·d),and it could be increased to 8.50 g VS/(L·d)with the effluent recirculation ratio of 50%.To sum up,the application of BA in the two-phase AD of food waste not only increased the methane production,but also provided a new way for the resource utilization of BA.Besides,it provided a new way of processing for the environmental protection industrial park,with good economic and environmental benefits.