Treatment of Industrial Wastewater of Variable Quality Using Ultrasound Irradiation

This paper investigated the use of ultrasound irradiation to treat real mixed industrial wastewater under various conditions, including single and dual frequencies, variable wastewater strengths, and different operating conditions, including flow rates/residence times. This work is important to evaluate the organics’ removal efficiency and to identify operational control bottlenecks under actual wastewater conditions. The highest removal efficiencies were 69.5% and 31.9% for COD and TOC, respectively, for the high-strength wastewater, which were found to occur at 16 kHz frequencies and 500 ml/min flow rate. The removal efficiencies were slightly less in the case of medium-strength wastewater (66.7 and 25.3% for COD and TOC, respectively). They were found to occur at dual frequencies of 16/20 kHz and 1500 and 1000 ml/min, respectively. For the low-strength wastewater, the efficiencies reached 78.6 and 9.1% for COD and TOC, respectively, at the same frequency and flow rates as the medium-strength wastewater. These findings demonstrated the effectiveness of dual frequency in medium- to low-strength wastewater. Among the organics monitored, chloroform (CHCl3), tetrachloroethene (C2Cl4), 1,4 dichlorobenzene (C6H4Cl2), and dichloromethane (CH2Cl2) exhibited variable removal, and in some cases, the removal was found to be negative, indicating intermediary products as a result of incomplete oxidation of organics. Besides the frequency and flow rate, it was found that the concentration of metals and organics are mostly positive influencers on organics removal. At the same time, TDS and pH have mixed effects, but they positively influence organics' removal at higher flows in a few instances. Additionally, as the residence time decreased, the concentration of organics and the pH negatively influenced organics removal. Doi: 10.28991/CEJ-2025-011-04-013 Full Text: PDF