Peroxidation enhances the biogas production in the anaerobic digestion of biosolids

During the anaerobic digestion of wastewater treatment sludge, commonly called biosolids, an energy rich biogas is formed which is now considered as renewable energy source and widely used for the production of heat and/or electricity. Pre-treatment methods, which achieve a transformation of refractory COD into readily available and soluble BOD, have the potential to enhance the biogas-production. This paper studies several peroxidation techniques for this purpose: the well-known Fenton peroxidation and novel reactions involving peroxymonosulphate (POMS) and dimethyldioxirane (DMDO). The results of the treatments show a considerable increase of COD and BOD in the sludge water, and an increase of the BOD/COD ratio. The biogas production was moreover seen to increase significantly. A maximum increase of 75% was measured with Fenton, while the POMS treatment increased the biogas production by a factor of nearly 2, against an even higher 2.5 for the DMDO treatment. The methane content of the biogas remained between 65 and 70%, thus maintaining its heating value.