Influence Of Ultrasonic Disintegration On Sludge Characterictics And Zero Waste Activated Sludge Production Process

Ultrasound can be applied to disintegrate the waste activated sludge(WAS),so that the substances inside and outside the cells release into the liquid phase, the sludge characteristics is changed and the quantity of sludge is decreased. After disintegration, the rate of subsequent anaerobic digestion and the production rate of biogas are improved. Besides this, the dewaterability of sludge is changed and new zero sludge production process may be found. In this paper, the probe type ultrasonic reactor with low frequency is applied to disintegrate the sludge from wastewater treatment plant. And the fundamental research is carried out. The main content is as following: the solution mechanism of released liquid from ultrasonic waste activated sludge disintegration; the change of sludge dewaterability before and after disintegration; the possibility of recycling the disintegrated sludge back to the aeration tank to realize zero sludge production process based on the lysis growth.It has been found that the soluble chemical oxygen demand (SCOD), protein, polysaccharides is increased greatly after disintegration. The predominant substance in the extracellular polymer substances (EPS) and the released liquid is protein. In the first 5min of sludge disintegration, the quantity of protein in the released liquid has exceeded the one in the EPS, which illustrates that the not only EPS in the sludge flocs are destroyed, but also the substances inside the cells are released into the solution. From the contour lines for the change of protein and DNA based on Response Surface Method (RSM), we know that the solution of protein and DNA increases with the increase of ultrasonic intensity and time. When the disintegration time is less than 15min, the solution of protein and DNA increases evenly with time increasing, and it is linear solution. When the disintegration time is more than 15min, the change rate of protein and DNA becomes slow down with time increasing. In the beginning of disintegration, the Ca2+ and Mg2+ release into the solution with sludge disintegration.After ultrasonic sludge disintegration, the sludge dewaterability characterized by Specific Resistance to Filtration (SRF) and Capillary Suction Time (CST) deteriorates. The deterioration of sludge dewaterability is related to solution of biological polymers. A great of biological polymers, such as protein and polysaccharides, release into solution and combine with water molecule, which increases the sludge viscosity and decrease the filtration characteristic. At the same time, the adsorption effect of fine...