The use of an oxidative pre-treatment method for increasing the efficiency of anaerobic digestion of waste activated sludge
Sustainable process-product development & green chemistry
Environmental Engineering & Management (T1-3P)
Keywords: biogas, anaerobic digestion, waste activated sludge, oxidation
The disposal of sewage sludge is a growing and worldwide problem. Waste Activated Sludge (WAS) processes are widely used for the treatment of urban wastewater because of their excellent purification capacity. They however produce huge amounts of Waste Activated Sludge (WAS), called bio-solids, which have to be disposed of. One way for reducing sludge volumes, thereby partially transforming its energy content into a useable fuel (biogas), is the use of anaerobic digestion. During anaerobic digestion, organic matter is partially decomposed by anaerobic micro-organisms and producing an energy-rich biogas. The latter can be used in gas engines for generating electricity or can be burnt with energy-recovery.
The digestion of WAS is however rate-limited by the hydrolysis-stage and sludge pretreatment (thermal, chemical, ultrasonic and mechanical) has been suggested in literature to enhance the reaction rate.
The use of Advanced Oxidation Processes (AOP) in WAS-treatment for enhancing the dewaterability of the sludge was previously reported in literature. It was concluded that this process destroys the extracellular polymeric substances in the sludge flocs and causes a disintegration of the sludge cells, hence releasing intracellular matter and increasing the soluble fraction of the COD and the polysaccharide and protein content of the sludge water. The released molecules provide a readily available feed source for the anaerobic micro-organisms, thus possibly enhancing the production of biogas.
During the present research, secondary sludge was subjected to several peroxidation methods, and lab-scale digestion experiments indeed confirm a significant increase in biogas-production. The green-energy value of the extra amounts of biogas produced, outbalances the costs of the peroxidation. The technical and economical results are presented.
Presented Monday 17, 13:30 to 15:00, in session Environmental Engineering & Management (T1-3P).
