THE EFFECTS OF ULTRASOUND ON SLUDGE DIGESTION

Ultrasound treatment, which involves the introduction of high-intensity sound waves into a sludge medium, is one of several technologies which promote hydrolysis during sludge treatment. It has become well-established with numerous full-scale plants in Europe operating for several years. The basic principle involves the release of extra-cellular material which then catalyses biological reactions and improves bacterial kinetics, resulting in lower sludge quantities and (in the case of anaerobic digestion) increased biogas production. Its use is most suited to plants containing large quantities of refractory material and/or cellular matter, such as waste activated sludge. This paper uses the data from several full-scale part-stream ultrasound plants and discusses the influence of the technology on numerous operating conditions, especially with respect to improved digestion and enhanced biogas production.