Weber Entec GmbH & Co. KG is a subsidiary of Weber Ultrasonics GmbH, a world-leading manufacturer of ultrasound components and ultrasonic welding equipment.

The company concentrates on general control systems and the construction of applications using ultrasound in the field of environmental engineering, especially the sewage sludge disintegration process developed jointly by Weber Ultrasonics and the Fraunhofer Institute. Because of its broad range of services, the company is a one-stop source for manufacturing, plant construction, sales, system analysis and process optimisation.

The Fraunhofer Institute, IKTS division, has been collaborating with Weber Ultrasonics for many years, resulting in the development of a sewage sludge disintegration process which is superior in crucial technical respects to currently available processes. This means that it can be used more universally and especially with greater cost and energy efficiency. The approach and mindset of scientists of the Fraunhofer Institute, confirmed by their years of fundamental research, coupled with the years of wide-ranging industrial experience of Weber Ultrasonics GmbH have ultimately produced a process which is now available in the form of the SmartDMS as a market-ready product.

 Ultrasonic disintegration of sludge

Sludge disintegration means the sludge is broken up by external forces into minute particles. Depending on the intensity of the impacting energy, this causes the floc structure of the sludge to disperse and increases enzyme activity until microorganisms contained in the sludge are broken down and cell constituents 
are released.

The SmartDMS discharges the necessary energy by ultrasonic cavitation generation. In ultrasonic disintegration, the electrical oscillations created by a generator are converted by a converter (sonic transducer) into mechanical oscillations. These oscillations are transferred by a device known as a sonotrode into the surrounding medium. Following the rhythm of the ultrasonic frequency, they cause alternating high positive and negative pressure phases, depending on whether the oscillator is expanding or contracting. During the negative pressure phase, microscopically tiny cavities are formed in the liquid exposed to the ultrasonics which then collapse in the subsequent positive pressure phase. This process is known as cavitation. While the cavities are collapsing, impact and shear forces occur in the area immediately around the cavities, which then cause the surrounding microorganisms to disintegrate.

The core technology of the SmartDMS is the Biopush reactor which was specially developed for sludge disintegration. The materials, amplitudes, oscillation frequency and construction were matched to the specific requirements, which guarantees maximum durability at maximum performance.

Advantages through ultrasonic disintegration

The organic substances released by disintegration are more readily available for both anaerobic and aerobic degradation. The increased enzyme activity has a similarly positive effect. This makes the SmartDMS a very versatile product.

Optimization of biogas plants

During fermentation of energy plants, slurry and manure the process biology is optimized. 

–› Enhancement of biogas yield up to 25%

–› Same power output at decreased substrate supply up to 5%

–› Decreased retention time in fermentation 8 to 15%

–› Reduction of stirring energy consumption up to 15%

Enhancing anaerobic stabilisation

In the majority of large municipal WWTPs, the sludge is treated anaerobically. The anaerobic degradation of organic substances goes through four phases which convert them to water, methane and carbon dioxide as end products. In the initial – and at the same time limiting – hydrolysis phase, polymeric substrates are split by exoenzymes into low-molecular dissolved components. Ultrasonic disintegration provides support for this degradation stage. This again has a positive effect on operating parameters relevant to sludge treatment and thus results in costs savings: 

–› Reduction by up to 15% in the amount of digested sludge to be disposed of (reduced disposal costs)

–› Increased specific biogas production related to the input of organic matter by up to 25% (generation of thermal and electrical energy)

–› Improved solid content after dewatering by up to 12% (reduced disposal costs)

–› Lower polymer demand by up to 15%

–› Reduction in the volume of the digester (relevant when planning new facilities or if digesters are overloaded) 

Eliminating problems with bulking and floating sludge

For some years, increasing problems with bulking and floating sludge, and the tendency of sludge to foam, have been observed at many WWTPs in Germany designed for the activated sludge process. These are biologically determined phenomena attributable to the proliferation of masses of filamentous organisms. 
The disintegration of return sludge produces the following effects:

–› Destruction and reduction of filamentous microorganisms

–› Improved sludge sedimentation in secondary sedimentation

–› Minimisation of problems with foam during digestion
(also possible by disintegration of excess sludge) 

Biological nitrogen removal / Aerobic stabilisation

Two further objectives can be formulated for aerobic applications: 

–› Reduced excess sludge production 
(relevant for aerobic sludge stabilisation, reduced disposal costs)

–› Improved denitrification capacity, production of internal carbon sources 
(cost saving by reducing external carbon sources)