Optimizing ozone solubility for effective surfactant removal and COD reduction in synthetic laundry wastewater

¹ Department of Chemical Engineering, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia
² Department of Chemical Engineering, Faculty of Industrial Technology, Universitas Pembangunan Nasional Veteran Yogyakarta, Yogyakarta 55283, Indonesia

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Laundry effluents generally contain high concentrations of surfactants and organic substances that can cause serious environmental and health impacts if discharged untreated. This study investigated ozonation as an alternative chemical treatment for synthetic laundry wastewater, focusing on ozone solubility and pollutant removal. Experiments were conducted in a 5 L reactor containing 1,6 mL of detergent/L wastewater with an ozone supply rate of 3 g/h. Operational parameters, including oxidation–reduction potential (ORP), DO, pH, dissolved ozone concentration, surfactant levels (MBAS), and chemical oxygen demand (COD), were monitored for 150 minutes. Based on Henry’s law, the theoretical maximum ozone solubility was 7.14 mg/L, but actual values were lower due to limited solubility, instability, and rapid reactions with water constituent. The 5 L reactor at 3 g/h provided the most stable ozone dissolution with lower ozone consumption. Results showed that MBAS decreased by over 90% within 90 minutes, while COD decreased more slowly, reaching about 40% at 150 minutes. The limited COD reduction suggests the presence of complex organics, that are more resistant to ozonation. Overall, ozonation was highly effective for surfactant degradation but less efficient for COD removal, indicating the need for complementary treatments to improve overall wastewater remediation.