The fermentation of sludge from WWTPs releases biogas. But it is very difficult to destroy the sludge particles effectively, which means that a considerable amount of energy remains unused. In the process of cavitation very high local temperature and pressure causes the disintegration of the particles. Such processes often require relatively high energy input, as in the case of ultrasonic cavitation for example. One installation developed by Whirlwindi, based on active hydrodynamic cavitation, might be more effective, thus disintegrating the sludge better. This technology is also of potential use in the removal of organic micropollutants from water.
With the use of a new Whirlwindi-developed system of generating hydrodynamic cavitation, WWTP sludge disintegration could be significantly improved. Besides a higher production levels of biogas, this also leads to a decrease in the amount of sludge requiring disposal. The advantage of active cavitation compared to the familiar passive cavitation is that operations can be conducted at lower flow rates and higher backpressures.
The project further developed this technology into an innovative pilot, which was tested on the Houtrust WWTP sludge line. This made it possible to study whether the application of active hydrodynamic cavitation leads to an increase in the production of biogas.
The pilot research allows one to conclude that 10% methane production can be expected following the sludge treatment using this active hydrodynamic cavitation tool. Potentially, the tool could also improve the dewatering abilities of the digested sludge.