Decomposition of 1,4-dioxane by advanced oxidation and biochemical process.
This study was undertaken to determine the optimal decomposition conditions when 1,4-dioxane was degraded using either the AOPs (Advanced Oxidation Processes) or the BAC-TERRA microbial complex. The advanced oxidation was operated with H2O2, in the range 4.7 to 51 mM, under 254 nm (25 W lamp) illumination, while varying the reaction parameters, such as the air flow rate and reaction time. The greatest oxidation rate (96%) of 1,4-dioxane was achieved with H2O2 concentration of 17 mM after a 2-hr reaction. As a result of this reaction, organic acid intermediates were formed, such as acetic, propionic and butyric acids. Furthermore, the study revealed that suspended particles, i.e., bio-flocs, kaolin and pozzolan, in the reaction were able to have an impact on the extent of 1,4-dioxane decomposition. The decomposition of 1,4-dioxane in the presence of bio-flocs was significantly declined due to hindered UV penetration through the solution as a result of the consistent dispersion of bio-particles. In contrast, dosing with pozzolan decomposed up to 98.8% of the 1,4-dioxane after 2 hr of reaction. Two actual wastewaters, from polyester manufacturing, containing 1,4-dioxane in the range 370 to 450 mg/L were able to be oxidized by as high as 100% within 15 min with the introduction of 100:200 (mg/L) Fe(II):H202 under UV illumination. Aerobic biological decomposition, employing BAC-TERRA, was able to remove up to 90% of 1,4-dioxane after 15 days of incubation. In the meantime, the by-products (i.e., acetic, propionic and valeric acid) generated were similar to those formed during the AOPs investigation. According to kinetic studies, both photo-decomposition and biodegradation of 1,4-dioxane followed pseudo first-order reaction kinetics, with k = 5 x 10(-4) s(-1) and 2.38 x 10(-6) s(-1), respectively. It was concluded that 1,4-dioxane could be readily degraded by both AOPs and BAC-TERRA, and that the actual polyester wastewater containing 1,4-dioxane could be successfully decomposed under the conditions of photo-Fenton oxidation.
Kim
Chang-Gyun
CG
Department of Environmental Engineering, Inha University, Incheon Metropolitan City, Korea. cgk@inha.ac.kr
Seo
Hyung-Joon
HJ
Lee
Byung-Ryul
BR
D001669:Biochemical Phenomena; D001671:Biochemistry; D001673:Biodegradation, Environmental; D004146:Dioxanes / Q000032:analysis*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D010777:Photochemistry; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*
D004146:Dioxanes; C045076:Fenton's reagent; D014874:Water Pollutants, Chemical; D006861:Hydrogen Peroxide; D007501:Iron; C025223:1,4-dioxane