Anaerobic Digestion of High Lipid Content Wastes: FOG Co-digestion and Milk Processing FAT Digestion

摘要

The digestion of two different residues with high lipid content was investigated in the present research. The first part of the experimental work focussed on an assessment of the co-digestion of sewage sludge and fat, oil and grease (FOG) residues separated from the grease trap in the biological pre-treatments of wastewater treatment plants, as proposed in the present study. The second part of the experimental work studied the individual digestion of fat recovered from the grease trap of a milk processing plant. The digestion process was performed under batch and semi-continuous operation at mesophilic temperatures. Successful digestion of wastes was attained, with no inhibitory consequences due to the accumulation of long-chain fatty acids. An increase in biogas production was observed under batch digestion of sewage sludge when FOG was added as a co-substrate. However, the small increase reported was in accordance with the limited volume of this residue added. With regard to the digestion of the milk processing fat, although the addition of nutrients may be necessary for maintaining longterm operation, with the long hydraulic retention time tested no foam accumulation was observed and successful operation was achieved.