Study On Methods For Treatment Of A Refractory Organic Contaminant 1,4-dioxane In Water

1,4-dioxane is an emerging contaminant, and is classified as a Class B2 (probable) human carcinogen by U.S. EPA. It is used as a stabilizer for chlorinated solvents, particularly, 1,1,1-trichloroethane (TCA), and it is formed as a by-product during the manufacture of polyester and various polyethoxylated compounds. 1,4-dioxane is also used as an ingredient in many products including dyes, resin, and oils. 1,4-dioxane with high aqueous solubility and high resistance to biodegdation, is difficult to remove from water and wastewater by conventional treatment processes, and greatly increase the potential for surface and groundwater contaminant.In this paper, the analysis of 1,4-dioxane in aqueous matrice using headspace-gas chromatographic(GC) method with a flame ionization detector(FID) was studied. The optimal analytical condition was determinated for the considering the factors of volume ratio of gas and liquid, ratio of N₂ and H₂, equilibrium time, equilibrium temperature. The lowest detection limit 0.1mg/L can be achieved. The method is accurate, fast and suitable for the lab analysis. The following studies contained the anaerobic biodegradation of 1,4-dioxane by enriched sludge with Fe(III)-reducing and humus-respiring microorganisms, and in the anaerobic cometabolic condition. The adsorption of 1,4-dioxane by high silica zeolite (ZSM-5) was also discussed.The enrichment of Fe(â…¢ )-reducing and humic acid-reducing bacteria in anaerobic sludge were tested in 50 days incubation. It was investigated that the incubated sludge with acetate as the carbon source had more capacity of reducing Fe( â…¢ ) and humic acid. The biodegradation of 1,4-dioxane occurred in Fe(â…¢)-supplemented sludge enrichment culture. The addition of humic acid as the terminal electrical acceptor improved the reducing of ferric oxide and the efficency of 1,4-dioxane degradation. The sludge enrichment of humic acid-reducing bacteria had the best degradation efficency, and the addition of Fe(â…¢) contributed to the mineralization of 1,4-dioxane.In the batch test, the sluge incubated with low 1,4-dioxane contributed to the biodegrading 1,4-dioxane. THF was supplied as the primary substance to enhance thebiodegradation of 1,4-dioxane, but the biodegradation efficiency with nothing supplied as extra carbon source was lower. The glucose as extra carbon source might inhibited biodegrading 1,4-dioxane. Results from the batch tests suggested that anaerobic biodegradation plays an important role on 1,4-dioxane removal. Intrinsic bioremediation is a feasible technology to remediate the 1,4-dioxane-contaminated site.Adsorption of 1,4-dioxane by high silica zeolite ZSM-5 was investigated. ZSM-5 zeolite possessed a higher adsorption capacity than other zeolite and activated carbon. The Langmuir and Freundlich model were applied to describe the equilibrium isotherms for 1,4-dioxane adsorption and the Langmuir model agrees very well with experimental data. The parameters of pH and temperature had little effect on the adsorption, and the adsorption capacity of ZSM-5 zeolite was steady.