Evaluation of Different Advanced Oxidation Processes (AOPs) for Removal of 1,4-Dioxane in Textile Wastewater

1,4-dioxane, which is widely used in various industrial processes, is one of the major recalcitrant and toxic contaminants. Several states in the US have established drinking water and groundwater guidelines as low as 0.3 ppb for 1,4-dioxane. Therefore, to address the industrial need to meet the regulatory standards for their discharge, investigation of efficient and cost-effective technologies is required. Advanced oxidation processes (AOPs) have shown promises in removing 1,4-dioxane from waste streams. However, the success of these processes depends on the water matrix. In many water and wastewater streams, 1,4-dioxane is accompanied by a background of organic substances, with a concentration significantly higher than the 1,4-dioxane. In these water-treatment applications, a selective method for the oxidation of 1,4-dioxane would be advantageous. A high selectivity treatment process versus other organics reduces operation cost and/or equipment footprint. In this study, several AOPs have been tested on a textile wastewater containing 350-450 ppm total organic carbon (TOC) and 12-14 ppm 1,4-dioxane to evaluate 1,4-dioxane destruction. The Fenton's process, electrochemical oxidation (EOX), and peroxone process (mixture of hydrogen peroxide and ozone) were investigated in 2-L batch reactors. UV + H2O2 was not included in this study due to low UV transmittance of the wastewater that would result in an inefficient destruction of 1,4-dioxane. Among the tested processes, peroxone was found to be the most efficient treatment technology by eliminating 1,4-dioxane from the wastewater to near non-detect levels in 2 hr (Figure 1), while Fenton's reaction (Figure 2) required up to 140 hr to reach that level. EOX was able to remove only 41% of 1,4-dioxane after 10 hr of reaction (Figure 3). Peroxone was the most selective oxidation process. TOC destruction was less than 30% while achieving > 99% destruction of 1,4-dioxane. The higher selectivity of peroxone process compared to the other AOPs should reduce the chemical usage as well as the reaction time. In the next step, process optimization will be performed by improving ozone mass transfer and solubility in addition to reducing the hydrogen peroxide dosing to minimize the capital and operating costs.