COD fractionation and solubility assessment of sonicated waste‐activated sludge

Abstract

Ultrasonic treatment is adopted as one of the important strategies to accelerate the hydrolysis of waste‐activated sludge (WAS). This study intends to optimize amplitude and time for ultrasonic treatment of WAS using statistically designed experiments that would render a better degree of disintegration, measured in terms of chemical oxygen demand (COD) solubilization. The main and interaction effects of nonlinear regression analysis revealed a significant interaction between amplitude and time over the degree of sludge disintegration. The ultrasonic density of 0.45 W/mL for 30 min favored a 153.84% increase in COD solubilization with a 27.65% degree of sludge disintegration. This condition also favored the minimum specific energy input of 801.58 kJ/g total suspended solids compared to other sonication conditions. Besides, the sludge volume index was reduced by 45% and 26% at the ultrasonic density of 0.45 W/mL for 60 and 30 min, respectively. Microscopic examination of WAS revealed disintegration of bacterial flocs during the ultrasonication process releasing filamentous bacteria with smaller floc sizes. The results from this study indicate that higher ultrasonic density for short time could improve the sludge disintegration with minimum specific energy input.

Comparison of ultrasound and UV technologies to control bulking and foaming in a wastewater treatment facility. A case study in an industrial park in Morelos, Mexico

“…After 10 min of ultrasound application, the SVI and TSS content of the mixed liquor sludge decreased to 53% and 89.9%, respectively. This is due to the effect of acoustic cavitation caused by sound waves, which leads to the breaking of cellular structures (David and Cheeke, 2017;Al-Hoqani et al, 2022), which could be revealed by microscope observations (Figure 5), where damage to the filament structure responsible for the bulking and foaming in the mixed liquor was evident. However, when applying 5 min of sonication to the mixed liquor samples, no drastic changes in the SVI were observed (only 14%), not consistent with the TSS reduction observed (and the microscopic observations that show there is damage to the filament structures).…”

“…However, when applying 5 min of sonication to the mixed liquor samples, no drastic changes in the SVI were observed (only 14%), not consistent with the TSS reduction observed (and the microscopic observations that show there is damage to the filament structures). Several studies support the use of ultrasound to carry out the hydrolysis of activated sludge (Al-Hoqani et al, 2022) and the inactivation of pathogens present in them (Vázquez-López et al, 2019).…”

“…Ultrasound has been successfully applied to inactivate pathogens and remove contaminants present in wastewater (Vázquez-López et al, 2019), as well as for the hydrolysis of activated sludge (Al-Hoqani et al, 2022). Ultrasound transducers transform electrical current into mechanical energy and generate mechanical vibrations and acoustic cavitation (the phenomenon of growth and collapse of bubbles due to the action of acoustic waves).…”

Degradation of Azo Dyes: Bacterial Potential for Bioremediation

“…As demonstrated, there is more than one form of inoculating a bioreactor for bioremediation use, and the initial bacteria acclimatation/growth also varies with the bacteria strain and bioreactor operation. Because of the various possibilities when it comes to bacterial inoculum, this step is susceptible to improvement, being an interesting hub for microbial prospection and cultivation optimizations, including here the pre-treatment of the sludge for better results [97][98][99].…”