Biological 1,4-Dioxane Wastewater Treatment by Immobilized Pseudonocardia sp. D17 on Lower 1,4-Dioxane Concentration

Abstract

Biological 1,4-dioxane removal performance using newly isolated Pseudonocardia sp. D17, which can utilize 1,4-dioxane as the sole carbon source, was evaluated. A low level of influent 1,4-dioxane, at 5–50 mg/L, was treated to meet the Japanese effluent standard of 0.5 mg/L. The gel entrapment technique was used for immobilization of Pseudonocardia sp. D17 so that it is not washed out from the bioreactor under a short hydraulic retention time. Consequently, an average effluent 1,4-dioxane concentration of 0.49 mg/L was achieved at a loading rate of 0.096 kg dioxane/(m³ · d) with an influent 1,4-dioxane concentration of 50 mg/L. The startup of the bioreactor was observed at 25°C within 2 weeks. Moreover, the effluent 1,4-dioxane concentration of 0.38 mg/L on an average was confirmed at a loading rate of 0.060 kg dioxane/(m³ · d), even though the operating temperature was 15°C. The temperature effect on 1,4-dioxane removal activity was characterized on the batch experiment. The maximum 1,4-dioxane removal activity was observed at 33.9°C. Moreover, 1,4-dioxane removal activity was observed even at 7.4°C, although that was decreased to 27% compared with that at 25°C. The activation energy for 1,4-dioxane removal by Pseudonocardia sp. D17, representing the temperature dependency, was calculated as 51.9 kJ/mol.