Abstract

Sludge treatment in wastewater treatment plants is one of the most difficult challenges for professionals and officials. Disinfection has become a challenging aspect of treatment because of the rapid elevation of health standards and the growing concern for pollution-free water resources. Chemical disinfection methods, like chlorination and ozonation, are often not environmental friendly (because of production of some undesirable by-products such as trihalomethanes) so alternative methods for disinfection are needed and the objective of this study is to determine the effect of ultrasonic waves with low wavelength and the high level of energy to improve removal rate of Escherichia coli in sludge and determine the optimum operating parameters of the ultrasonic method. In this research, variables include ultrasound density (0.375, 0.75, 1, 1.3 and 2.5) W per 1 mL and time (1, 5, 10, 15 and 30) min. Furthermore, the impact of these variables on the E. coli inactivation in sludge is measured. The results shows a significant increase in rate of E. coli bacteria reduction by increase of ultrasound density from 0.375 to 2.5 W/mL. By increasing of sonication time from 1 minute to 30 min, the similar increase in rate of E. coli bacteria reduction was observed. The experiments determined that the optimum operating parameters be sonification time of 30 min, ultrasound density of 2.5 W/mL in the frequency of 20 kHz. Inactivation rate of E. coli in these circumstances was 99.43% that is more than 2 logs. Based on the results of this research, high power and low-frequency ultrasound waves are capable of eliminating nearly all the E. coli bacteria population at relatively short irradiation time and they could remove E. coli and disinfect the sludge hence could increase the treatment rate.

中文翻译：

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超声波和纳米气泡在污泥大肠杆菌灭活中的应用

摘要

污水处理厂的污泥处理是专业人员和官员最困难的挑战之一。由于卫生标准的迅速提高和对无公害水资源的日益关注，消毒已成为一种具有挑战性的治疗方法。化学消毒方法，例如氯化和臭氧化，通常对环境不友好（由于产生了一些不良副产物，例如三卤甲烷），因此需要其他消毒方法，并且本研究的目的是确定超声波的影响低波长和高能级以提高大肠杆菌的去除率在污泥中，并确定超声方法的最佳操作参数。在这项研究中，变量包括每1 mL超声波密度（0.375、0.75、1、1.3和2.5）W和时间（1、5、10、15和30）分钟。此外，测量了这些变量对污泥中大肠杆菌灭活的影响。结果表明，通过将超声波密度从0.375提高到2.5 W / mL，大肠杆菌细菌的减少率显着提高。通过将超声处理时间从1分钟增加到30分钟，可以观察到类似的大肠杆菌减少率增加。实验确定最佳的操作参数是30分钟的超声处理时间，20 kHz的频率下的超声密度2.5 W / mL。大肠杆菌的失活率在这种情况下为99.43％，即超过2个日志。根据这项研究的结果，高功率和低频超声波能够在相对较短的照射时间内消除几乎所有大肠杆菌菌群，并且可以去除大肠杆菌并对污泥进行消毒，因此可以提高处理率。