Using Ultrasound to improve breakdown of sewage solids, increase destruction of harmful micro-organisms, increase biogas generation, speed-up settlement and improve de-watering of residual biowaste – Ultrasewage -

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Innovate UK
Innovate UK

£150,240

Sept. 30, 2014

Sept. 29, 2015

The 9600 sewage treatment facilities in the UK process 1.7 million te p.a. (Water UK). The
main process involves the separation of solids as sludge, from the water component that then
undergoes filtration and bacterial treatments to produce clean water. The sludge component
undergoes processes to render it useful, most commonly including a digestion step, either
aerobic or anaerobic. Digestion can be used to produce biogas very effectively in purpose
built modern reactors, a vital & growing contribution to the nation’s renewable energy goals.
The final bio-waste sludge can be used as a fertiliser.
Sludge ideally enters the digester in a finely divided state, with the organic cell contents
available for the bacteria to attack. Recent advances in power ultrasonic processing have
shown the potential to increase the control and efficiency of these processes. However, a
major downside of in-line ultrasonic processing, where the sonotrode is inside the pipe with
small clearances for good sonic power transfer, is the propensity for blockage. Increasing the
clearance requires higher power sonotrodes that undergo cavitational degradation of the tips,
again requiring more frequent shutdown for replacement and maintenance.
There is an opportunity to apply our free flowing (no internal components, will not block)
ultrasonic pipe technique from a food industry processing aid, to use it at medium power to
provide de-agglomeration of solids & at low power to accelerate the flocculation of particles
for sedimentation. We further wish to prove the concept in the high power pre-processing of
sludge, to break down cells and increase the speed and yield of digestion processes.
This new technology would be retrofittable to existing lines with minimal disruption. Users
could benefit from 50% higher flow rates, 30% pump power reduction, much greater process
capability, much lower maintenance cost & no blockages, in addition to up to 30%
improvement in biogas yield from digestion.