A Research On The Anoxic/Aerobic Digestion Of Sludge Intensified By Ultrasonic Wave

Use of ultrasound disintegration the waste activated sludge (WAS) of urban sewage plant, can change the characteristics of sludge, and the substances inside and outside of the sludge cells dissolution into the liquid phase, is conductive not only the dissolution of micro-organisms as of the end of the realization of hidden growth, promote follow-up sludge digestion rate, reduce the amount of solid sludge, but will affect the dewaterability of sludge. In this paper, the low-frequency (28 kHz) trough ultrasonic cleaning reactor is applied to disintegrate the WAS from Guangzhou Lijiao urban sewage plant. The solution mechanism of released liquid from ultrasonic WAS disintegration is studied, and the promotion action of ultrasonic disintegration to sludge stabilization and reduction in WAS anoxic/aerobic digestion technology of hidden growth is researched.The results showed that the ultrasound played signigicant role in the sludge cell lysis, the SCOD, TN, TP of supernatant after a short period of time of ultrasonic radiation is basically a linear trend of increase, and the sludge biodegradable properties is improved. Ultrasonic promote sludge from the cellular material into the liquid inside and outside, in the relatively low density of the sound energy, a 0.05 w/mL of sound energy density is more ideal. Seeing from the state of particles and biota in the sludge in a certain time of ultrasonic radiation, 20 minutes of irradiation not only can play a better role in the dissolution cell, but avoid a filamentous expansion. Therefore, a 0.05 w/mL of sound energy density and 20 minutes radiation in the economy and disintegration results achieved strike a better balance.In order to verify the role of ultrasound on the effects of sludge digestion, the three controlled groups of sludge ultrasonic-anoxic/aerobic digestion (US-A/AD) process was designed to digest for 20 days. The results showed that in the same room temperature, the same as the initial conditions of sludge, the same anoxic/aerobic digestion conditions, sludge digestion stability of No. 2 digestive tank(a frequency of 28 kHz, 0.05 w/mL of sound energy density, 20 minutes of irradiation time and 13.3 % of the sludge) was the best. After 16 days of digestion, its volatile suspend solid (VSS) removal rate reached 45.2 percent, after 20 days of digestion, the VSS removal rate reached 50.35 percent. No.3 digestive tank was followed by No.2. It was entered twice daily equivalent energy of No.2 digestive tank. After 16 days of digestion the removal rate of the VSS was 38.69 percent. After 20 days the removal rate of the VSS was 44.44 percent. The comparison group No.1 tank was the minimum. After 16 days of digestion the VSS removal rate was 38.4%, 20 days the VSS removal rate was 40.53 percent.To further study the digestive effects of low-dose ultrasound under US-A/AD digestion process, through better technical conditions under extension test of the US-A/AD sludge digestion process , every three days irradiation (at room temperature, Frequency of 28 kHz, 0.05 w/mL of sound energy density, 20minutes) 5% of the sludge, after 16 days of digestion, the average removal rate of VSS in the sludge reached 40.95 percent, has been able to meet the request on the sludge stabilization of "Urban Sewage Treatment Plant Emissions Standards "(GB18918-2002) . After 20 days of sludge digestion, the average removal rate of TSS and VSS, were respectively 30.4 percent and 47.53 percent. In an inspection of a cycle (24hours) digestive period in the US-A/AD process, ultrasonic sludge makes the role of organic matter in the rapid dissolution, which makes sludge quickly reduction possible. And the removal and reduction of organic compounds in the sludge mainly happened in the aerobic period. Through aerobic microbes, organic matter has continually been used as a substrate to digest, so that VSS in the sludge decline, thus achieving the stability and minimization of the sludge. And anoxic digestion of the sludge is to provide the system stable nitrogen and pH value, and maintain the system stable operation. The denitrification in the anoxic period, makes the TN in the supernatant of the sludge system inaccumulate.