Distribution of 1,4-dioxane in relation to possible sources in the water environment

Microbial succession in response to 1,4-dioxane exposure in activated sludge reactors: effect of inoculum source and extra carbon addition

Bacterial community succession related to 1,4-dioxane exposure was investigated in two different activated sludge-inoculated reactors (municipal wastewater and dye industrial wastewater sludge), with or without additional carbon source, for 7 weeks. The denaturing gradient gel electrophoresis (DGGE) analysis revealed that microbial succession varied according to the inoculum sludge sources and the presence or absence of the extra carbon source. In the reactor inoculated with the municipal sludge, bacterial species belonging to alpha- and gamma-Proteobacteria and Nitrospira class were dominant over time. On the other hand, bacterial species showing significant homology to beta-Proteobacteria (e.g., Methylibium petroleiphilum PM1) and Actinobacteria class, who have been reported to have 1,4-dioxane degradation potential, were found in the industrial sludge-inoculated reactors. The appearance of these bacteria demonstrates that the microbial community structure of the inoculum and the presence of an extra carbon source affect the microbial succession in the system exposed to 1,4-dioxane.

Distribution and variation of 1,4-dioxane in water from rivers in Niigata including the Shinano River

The distribution of 1,4-dioxane in the waters from 27 sites in 12 rivers including the Shinano River, the longest river in Japan, was investigated in 2002. 1,4-Dioxane was detected in concentrations ranging from 0.02 to 0.49 microg/L. The monthly variations in the 1,4-dioxane concentrations at 6 sites along the Shinano River showed mutually different patterns, and the concentrations did not correlate with the concentrations of the biochemical oxygen demand and the suspended substances. The annual mean concentrations were from 0.02 microg/L at sites located in the middle reaches to 0.11 microg/L at the river mouth. The 1,4-dioxane concentration in the Shinano River has shown a downward trend from 1989 to 2003.

Investigation of 1,4-dioxane originating from incineration residues produced by incineration of municipal solid waste

As a groundwater contaminant, 1,4-dioxane is of considerable concern because of its toxicity, refractory nature to degradation, and rapid migration within an aquifer. Although landfill leachate has been reported to contain significant levels of 1,4-dioxane, the origin of 1,4-dioxane in leachate has not been clarified until now. In this study, the origins of 1,4-dioxane in landfill leachate were investigated at 38 landfill sites and three incineration plants in Japan. Extremely high levels of 1,4-dioxane 89 and 340 microg l(-1), were detected in leachate from two of the landfill sites sampled. Assessments of leachate and measurement of 1,4-dioxane in incineration residues revealed the most likely source of 1,4-dioxane in the leachate to be the fly ash produced by municipal solid waste incinerators. Effective removal of 1,4-dioxane in leachate from fly ash was achieved using heating dechlorination systems. Rapid leaching of 1,4-dioxane observed from fly ash in a sequential batch extraction indicated that the incorporation of a waste washing process could also be effective for the removal of 1,4-dioxane in fly ash.

Ozonation combined with electrolysis of 1,4-dioxane using a two-compartment electrolytic flow cell with solid electrolyte

Ozonation combined with electrolysis (ozone-electrolysis) is a new advanced oxidation process for water treatment. The advantages of ozone-electrolysis are (1) that reagents such as hydrogen peroxide or ferrous salts are unnecessary, (2) there is less influence from chromaticity, and (3) electric power is only required for operation. However, electrolysis has a serious limitation, in that it requires electrical conductivity (EC). This research is aimed at developing an ozone-electrolysis reactor that is applicable to wastewater with low EC using a cation exchange membrane as solid electrolyte. Moreover, experimental evidence of hydroxyl radical (.OH) generation via the cathodic reduction of ozone was obtained. Competitive kinetics analysis, based on the experimental data from the ozone-electrolysis of a mixed solution of 1,4-dioxane and tert-butyl alcohol, revealed that .OH contributed to 1,4-dioxane degradation. The ozone-electrolysis reactor was successfully applicable to degradation of 1,4-dioxane in both 1,4-dioxane solution (EC: less than 0.30 microS/cm) and a landfill leachate treated by a low-pressure reverse osmosis membrane (EC: 0.06 mS/cm). The use of a solid electrolyte was also very effective in reducing the electric power required for electrolysis.

Ralstonia pickettiiin environmental biotechnology: potential and applications

Xenobiotic pollutants such as toluene and trichloroethylene are released into the environment by various industrial processes. Ralstonia pickettii possess significant biotechnological potential in the field of bioremediation and has demonstrated the ability to breakdown many of these toxic substances. Here, we provide a description of the major compounds that various strains of R. pickettii are capable of degrading and a brief review of their breakdown pathways and an argument for its use in bioremediation.

Enhanced sonochemical decomposition of 1,4-dioxane by ferrous iron

The enhanced ultrasonic decomposition of 1,4-dioxane by the addition of ferrous iron (Fe(II)) was investigated at 205, 358, 618, and 1071 kHz. The total organic carbon (TOC) remaining was also determined at each frequency. Addition of Fe(II) improved the 1,4-dioxane decomposition rate and mineralization efficiency at all frequencies studied. A nearly four-fold increase of the rate constant was observed at the optimal Fe(II) concentration and a frequency of 205 kHz. In the presence and absence of the iron, the fastest overall degradation and mineralization of 1,4-dioxane took place at 358 kHz where 95% of the initial 1,4-dioxane was removed after 50 min. Finally, although reduced, the ultrasonic decomposition of 1,4-dioxane was still significant at all frequencies in the presence of the hydroxyl radical scavenger bicarbonate.

Gas chromatographic-mass spectrometric determination of hydrophilic compounds in environmental water by solid-phase extraction with activated carbon fiber felt

Simple gas chromatographic-mass spectrometric determination of hydrophilic organic compounds in environmental water was developed. A cartridge containing activated carbon fiber felt was made by way of trial and was evaluated for solid-phase extraction of the compounds in water. The hydrophilic compounds investigated were acrylamide, N,N-dimethylacetamide, N,N-dimethylformamide, 1,4-dioxane, furfural, furfuryl alcohol, N-nitrosodiethylamine and N-nitrosodimethylamine. Overall recoveries were good (80-100%) from groundwater and river water. The relative standard deviations ranged from 4.5 to 16% for the target compounds. The minimum detectable concentrations were 0.02 to 0.03 microg/l. This method was successfully applied to several river water samples.