Wastewater treatment has used a wide range of technologies through the years to streamline its process of converting sewage into biosolids and clean water. One novel approach that is being utilized lately is with the use of wastewater ultrasound technology. These high intensity sound waves are applied to sewage to promote hydrolysis during sludge treatment.
Ultrasound causes the destruction of bacterial cells and difficult-to-degrade organics. The destroyed cells release its contents making it available for consumption by other species during anaerobic digestion, while the remaining organics are broken down into smaller readily biodegradable fractions.
When applied to a liquid medium, wastewater ultrasound technology causes minute bubbles to form during the cavitation process. This is when extreme temperature and pressure are used to cause the cavitation bubbles to implode. These implosions break up the sludge particles and the effects of which may vary depending on the intensity of the ultrasonic field.
Lower intensities cause filamentous organisms to be shaken off and/or destroyed from the surface of sludge particles, thereby aiding sludge settlement. Higher intensities raise the particle size distribution and surface charge of the sludge particles alters. Extracellular materials are released, and dewatering characteristics are improved in a process known as “bioflocculation” which makes sludge dewater better.
This higher intensity of wastewater ultrasound technology increases the availability of enzymes which assists in biological hydrolysis reactions and improves biokinetic reaction rates. Since volatile solids can also be broken down, biogas production increases and solids output during anaerobic digestion is reduced. This also leads to reduced solids during activated sludge treatment.
Wastewater ultrasound technology has proven to be so effective that full-scale demonstrations of this process have resulted in the removal of over 80% phosphorous and 90% of ammonia from the sludge.
Large quantities of waste and sludge along with refractory material and/or cellular matter are efficiently broken down by ultrasound that these streams are almost completely catabolized during anaerobic digestion.
The use of ultrasound isn’t entirely new, however. Europe has been using this process for several years across 14 wastewater treatment plants. Germany has documented impressive results from two full-scale treatment plants that use wastewater ultrasound technology in treating sludge.
Their ultrasound treatment improved volatile solids destruction in anaerobic digesters by an average of 50%, which subsequently increased biogas production by 45% at a sewage treatment plant located in Süd, Germany. The feed stream of the anaerobic digester at this site is now fully supplied by ultrasonically treated sludge.
Another German treatment plant located in Wallerfangen saw an improvement of volatile solids destruction from 50% to 62% using wastewater ultrasound technology. Unlike the Süd plant however, the feed stream is composed of a mixture of primary and secondary sludge at a ratio of 35:65. Their biogas production increased by an average of approximately 25%. In the dewatering plant, cake solids content increased by up to seven percentage points (an improvement of >40%). Dewatering performance improved from 17% to 24% dry solids. Combined, the improved dewatering and volatile solids destruction resulted in 30% less sludge after treatment.
If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us at 1 (877) 479-1388.