Study On Inhibitory Mechanism Of Lipid In Anaerobic Digestion For Food Waste

Nowadays a large amount of food waste are produced in China, which is easily decayed, emitting malodor and transmitting diseases. How to dispose food waste properly has becoming a significant and urgent problem. Anaerobic digestion for food waste is considered to be an effective approach to promoting energy saving and pollution alleviation. Food waste is rich in organic matters, especially high oil content, which is provided with great gassing property. However, high oil content will affact the stability of anaerobic digestion. Due to this problem, inhibition mechanism of anaerobic digestion for lipid and other orgnic matter had been studied in sequencing batch reactors in this thesis. Then the adaptive dosing quantity of organicsubstances and oil content had been optimized by response surface experiments. At last, The removal and accomulation of lipid in continuously single-phase anaerobic digestion reactor were also been studied. Several conclusions had obtained from the experiments aboved.The inhibition mechanism of lipid was different from other orgnic matters in food waste. For the lipid, high-concentration of long chain fatty acid adsorbing the surface of cytomembrane hindered mass transfer and coacervation of undegraded lipid wrap up sludge which restrain the activity of acid-producing bacteria and methanogen. And for the other orgnic matters, the main reason was that high-concentration volatile fatty acid(VFA) and acidulated habitat restrain the activity of methanogen.The digestion of lipid was more easily hindered than other orgnic matters in the case of high dosing quantity. The maximal dosing quantity of lipid and other matters were in the rangs of 45 to 51 kgVS/m3 and 6.0 to 24.0 kgVS/m3 respectively. The gassing property of lipid was also much great than other orgnic matter and their gas production rate in the intervals of 1.30 to 1.50 L/gVS and 0.56 to 0.68 L/gVS. The gassing property of animal oil was slightly bigger than vegetable oil with their gas production rate of 1.22 and 1.37 L/gVS.In batch anaerobic digestion for food waste with their dosing quantity in the interval of 40 to 60 kgVS/m3, it had no affact to the stability of the system.when the oil content ranged from 5% to 15%. The optimal dosing quantity and oil content for maximum gas production were 50.9 kgVS/m3 and 9.23%.In continuously single-phase anaerobic digestion for food waste, the optimal of lipid volumetric loading rate was 1.59 kgVS/(m3·d), and the maximum volume biogas production and gas production rate were displayed as 6.4L/(L·d) and 1.18L/gVS respectively. The average and maximum methane content were 68% and 75%, which was very suitable for biogas recycling. The lipid easily accumulated in reactor, where the lipid volumetric loading rate was over 1.59 kgVS/(m3·d), and formed as elaiosphere and oil sludge which encapsulated microorganisms and reduce effective microorganisms. It was probably the main reason for operation failure of anaerobic digestion for food waste.