EFFECT OF ULTRASOUND ON THE BIOLOGICAL-ACTIVITY OF BACTERIA USED IN WASTEWATER-TREATMENT

In biological wastewater treatment, the limiting factor is usually the efficiency of oxygen transfer from air to water. It is known that high fluid turbulence will increase oxygen transfer efficiency. A very high degree of local turbulence can be created by ultrasonic cavitation. In the reported experiments, a total of 10 cultures isolated from a municipal waste treatment plant, along with ″mixed liquor″ from the same plant, were subjected to ultrasonic irradiation for 15 min at a frequency of 25 kHz and an acoustic intensity of 2. 0 watt/cm**2. Survival rates varied widely, from a low of 0% to a high of 77%. Respiration rates showed a close correspondence to survival rates. It is demonstrated that simultaneous aeration and ultrasonic treatment led to a steady increase in respiration rate, indicating that the ultrasonically aerated culture was more metabolically active than those not irradiated.