Biogas comes from municipal organic waste, sewage sludge, muck or manure. Ultrasonic treatment improves the digestibility of this organic matter, resulting in more biogas and less sludge residue. Biogas is a by-product of the decomposition of organic matter by anaerobic or aerobic bacteria. It is mainly composed of methane, carbon dioxide and hydrogen sulfide. This makes biogas a renewable alternative to fossil fuels such as natural gas.
Energy prices and other interests such as chemicals, sludge treatment costs, environmental legislation, etc. require wastewater treatment plants to improve their treatment efficiency. Ultrasonic decomposition of organic materials prior to digestion significantly improves biogas production. With sonication the dewaterability of the sludge is improved and the amount of residual sludge to be treated is reduced.
The raw materials used in the production of biogas are a mixture of various aggregated and flocculated substances, fibers, viruses and bacteria, cellulose and other inorganic substances. Food waste, organic industrial and commercial waste, such as fats or distiller's grains, are supplementary raw materials for mesophilic and mesophilic digesters. Ultrasonic cavitation destroys aggregates and cellular structures. Sludge can be dewatered more easily due to the effect on the structure of the constituent materials. In addition, disruption of aggregates and cell walls improves the bioavailability of intracellular material for breakdown by bacteria.
Various results can be achieved with the application of ultrasound in sludge and waste stream treatment, such as:
Increase biogas production
Improve anaerobic decomposition
Improve the C/N ratio of denitrification
Improved settling behavior through degassing and flake disintegration
Improve the thickening process of excess sludge
Improve digestion and dehydration
Lower disposal costs due to reduced residual sludge after digestion
Reduction of polymers required
Destruction of filamentous bacteria