The inhibitory effect of lipids and prevention of this inhibition in a two-phase anaerobic process were examined using laboratory-scale reactors and batch experiments. Lipids were satisfactorily degraded in a two-phase anaerobic filter while in a single-phase system, inhibition resulted in poor lipid degradation. Unsaturated long-chain fatty acids (LFAs) had a greater inhibitory effect than saturated LFAs. Methane production as well as beta-oxidation (degradation of saturated LFAs) were inhibited by unsaturated LFAs. The saturation of unsaturated LFAs was not inhibited, and palmitate (C16:0) was accumulated in the degradation of oleate (C18:l) or linoleate (C18:2). Greater inhibition was observed at low pH values. Continuous operation of a suspended-growth acidogenic reactor showed that hydraulic retention times (HRTs) of no less than 8 hours were necessary to mitigate the inhibition in a two-phase process. The fact that saturation of oleate occurred at HRTs no less than 8 hours suggests that the saturation of unsaturated LFAs in an acidogenic reactor is essential in the prevention of lipid inhibition in two-phase anaerobic processes.

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In this study, we report a new effective sludge-digestion gas (biogas) adsorption storage technology. The experimental data of the pure and binary adsorption equilibrium of methane and carbon dioxide, which are the main components of the biogas, on five types of activated carbons at a temperature range of 273-333 K and pressures up to 6 MPa, were measured. Pure isotherms were fitted with the Toth and extended Toth models. Binary equilibrium was predicted using the Ideal Adsorbed Solution Theory (IAST) based on the extended Toth model with the experimental data being predicted as well. The differential enthalpy of the pure and binary adsorption was calculated, and storage densities of the binary gases, methane and carbon dioxide, considering the increased activated carbon temperature, were estimated using the adiabat and isobar of mixed gases in the biogas composition.

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