| Title |
Feasibility of Ultrasonic Irradiation on Raw Sludge as Carbon Source for BNR Process |
| Authors |
황규대 ( Hwang Gyu Dae ) ; 강재순 ( Kang Jae Sun ) ; 장준기 ( Jang Jun Gi ) |
| Keywords |
Raw Sludge; Ultrasonic Irradiation; Cavitation; Carbon Source; BNR Process; Denitrificaton; P-release |
| Abstract |
In the sonochemical reaction, the solid of sludge can be disintegrated and solubilized by hydromechanical shear force, pyrolysis, and free radical attack during the cavitation. This study was performed to evaluate the feasibility of ultrasonically treated raw sludge as carbon source for biological denitrification and phosphate release. A 530W ultrasonic processor with a frequency of 40kHz was used to sonicated the raw sludge from wastewater plant. To find the optimal SCODcr buildup condition. we examined the effects of solid concentration of sludge, ultrasonic density, irradiation time, aeration, and pH on TSS and SCODcr concentration during the ultrasonic irradiation on raw sludge. Ultrasonic irradiation was applied to raw sludges with different solid contents (1, 3, and 5%.) and different ultrasonic density (0.04, 0.06, and 0.12W/rnl). Ultrasonic irradiation showed a rapid and significant decrease in TSS concentration in raw sludge. The kinetic of the degradation rates of TSS by ultrasonic irradiation was satisfactorily described by a pseudo-first order reaction. The degradation efficiency of solid in raw sludges were over 60%, and ranged from 3.0 to 7.2 ㎎TSS/W . hr. Also the SCODcr yields of 2.1 -3.2 ㎎SCODcr/W·hr in this study were observed and depended strongly on ultrasonic density. With aeration. the sonication on raw sludge further increased SCODcr concentration. However, it is less effective to irradiate ultrasonically the pH-adiusted raw sludge. The optimal operating condition to increase soluble organics was to sonicate the sludge with 5% TSS under the ultrasonic density of 0.12W/ml and showed the yield of 3.2 ㎎SCODcr/W . hr. Also the sonicated sludges with different sonication time(ranging between 0-9hrs) under 0.I2W/ml were fed into the batch reactors as carbon source. Those ones had a strong influence on the denitrification rate and the P-release concentration. The specific denitrification rates of batch reactors varied within a range from 0.46 to 1.97 mgNO₃-N/gVSS·hr, and 1.33-1.85 gSCODCr consumed/gNO₃-N removed was observed. The concentration of phosphate which was released by poly P microbes were in the range of 0-4.75㎎/L. and 0.55-1.22gPO₄-P released /gSCODcr consumed was showed. The economically most competitive sludge as carbon source was one under 3hr sonication time to accomplish the high denitrification rate and the P-release concentration. Therefore, the ultrasonically treated sludge can be another carbon source for BNR process. |