Sound waves bubble biogas out of sludge

In a collaborative sludge treatment study, the Fraunhofer Institute for Ceramic Technologies and Sintered Materials (IKTS) has developed a process that exposes portions of sludge to sound waves that mechanically break it down.

“The ultrasound treatment creates microscopic bubbles within the sludge which implode and collapse. With this cavitation, the sludge substances can be broken down,” explains Dr Hannelore Friedrich of IKTS. The sludge chemistry changes, releasing enzymes that accelerate the digestion of organic matter. The resulting gas yield is improved by up to 45%.

“Our new process significantly helps to reduce sewage treatment costs and the investment can be fully amortized within less than four years,” continues Dr Friedrich, pointing to reduced energy costs for dehydrating the sludge, a shortened digestion period, less residue for disposal and increased gas yield.

Eleven sewage treatment facilities in Germany are already using the process, known as split-stream pulse disintegration. Japan, the UK, US, Canada and Australia have expressed interest in the process.