Low Frequencies Ultrasonic Treatment of Sludge

Abstract

In the present investigation, ultrasonic (US) irradiation treatment technology has been adopted. The mechanism of action (cavitation and sonochemical reaction) of ultrasonic radiation is such that it acts as a potential tool for enhanced biodegradation and sonodegradation of waste and also recovery of resources from treated waste. In ultrasonic waste treatment technology the frequency of US and treatment time is a significant factor in determining optimal reaction conditions. The optimum frequency is substrate specific and low frequency is suitable for sewage sludge treatment. So we opted low frequency (35 kHz and 130 kHz) ultrasonic treatment over varying intervals of time to find out the possibilities to change the quality of sludge by ultrasonic irradiation. Primary sludge characterization parameters i.e. pH, conductivity, chemical oxygen demand (COD), total solid content, total nitrogen and total phosphorus were measured. Ultrasonic pre-treatment was carried out for 5, 10, 20 and 30 min. each (t $_1$ -t $_4$ ). Under following treatment, temperature rise, increase in the amount of soluble chemical oxygen demand (SCOD), total nitrogen and phosphorus were analyzed. Both control and treated samples (t $_1$ -t $_4$ ) were analysed side by side. Very little change in total nitrogen was observed but significant decline level of phosphorus in samples were seen with increase of time of treatment. These data may provide useful information in the way to solve water and soil pollution by ultrasonic treatment.