Enhancing excess sludge aerobic digestion with low intensity ultrasound

Abstract

In order to enhance the efficiency of aerobic digestion, the excess sludge was irradiated by low intensity ultrasound at a frequency of 28 kHz and acoustic intensity of 0.53 W/cm². The results show that the sludge stabilization without ultrasonic treatment can be achieved after 17 d of digestion, whereas the digestion time of ultrasonic groups can be cut by 3–7 d. During the same digestion elapsing, in ultrasonic groups the total volatile suspended solid removal rate is higher than that in the control group. The kinetics of aerobic digestion of excess sludge with ultrasound can also be described with first-order reaction.

Keywords

low intensity ultrasound / excess sludge / aerobic digestion / kinetics

References

[1] BernardS, GrayN F. Aerobic digestion of pharmaceutical and domestic wastewater sludges at ambient temperature[J]. Wat Res, 2000, 34(3): 725-734

[2] ZhangGuang-ming, WuMin-sheng, ZhangWeihao, et al.. Study of ultrasonic treatment of sludge[J]. Urban Environment & Urban Ecology, 2003, 16(6): 258-259(in Chinese)

[3] JanuaryB, LidiaW. Changes of some sewage sludge parameters prepared with an ultrasonic field[J]. Wat Sci Tech, 1997, 36(11): 101-106

[4] SchlaferO, SieversM, KlotzbucherH, et al.. Improvement of biological activity by low energy ultrasound assisted bioreactors[J]. Ultrasound, 2000, 38(1–8): 711-716

[5] Editorial Board of Environment Protection Bureau of ChinaMonitoring and determination methods for water and wastewater[M], 19973rd ed.Beijing, China Environmental Science Press

[6] LishmanL A, MurphlyK L. The significance of hydrolysis in microbial death and decay[J]. Wat Res, 1994, 28(11): 2417-2419

[7] BougrierC, CarrèreH, DelgenèsJ P. Solubilisation of waste-activated sludge by ultrasonic treatment [J]. Chemical Engineering Journal, 2005, 106(2): 163-169

[8] HenzeM, MladenovskiC. Hydrolysis of particulate substrate by activated sludge under aerobic-anoxic and anaerobic conditions[J]. Wat Res, 1991, 25(1): 61-64

[9] StephenB, CliveB. The effects of ultrasound on the activities of some glycosidase enzymes of industrial importance [J]. Enzyme and Microbial Technology, 1996, 18(30): 190-194

[10] TiehmA, NickleK, NeisU. Ultrasonic waste activated sludge disintegration for improving anaerobic stabilization[J]. Water Research, 2001, 35(8): 2003-2009

[11] LiuHong, YanYi-xin, WangWen-yan, et al.. Improvement of the activity of activated sludge by low intensity ultrasound [J]. Environmental Science, 2005, 26(4): 124-128(in Chinese)

[12] ChuC P, ChangB, LiaoG S, et al.. Observations on changes in ultrasonically treated waste-activated sludge [J]. Water Research, 2001, 35(4): 1038-1046

[13] LiHui. Mechanisms of enhancing liquid-solid mass transfer with ultrasound[J]. Journal of Shenyang Institute of Chemical Technology, 1994, 8(3): 175-181(in Chinese)

[14] LiYa-feng, MaHui, WangXiao-hua. Dynamics and relevant questions about sludge aerobic treatment [J]. Journal of Shenyang Arch and Civ Eng Univ: Natural Science, 2002, 18(2): 132-134(in Chinese)