Kohei Urano

Empirical rate equation for trihalomethane formation with chlorination of humic substances in water

Trihalomethane (THM) in drinking water is formed by chlorination of humic substances. In this study, the rates of THM formation in aqueous solution of humic acid were examined under various conditions. The following rate equation was obtained empirically. [THM] = k (pH − a)[TOC][Cl2]0mtn. Here, [THM] is the concentration of total THM after t h, [TOC] and [Cl2]0 are the concentrations of total organic carbon and chlorine dose, k is the rate constant and a, m and n are parameters. The values of k, a, m and n for humic acid as reagent were obtained as 8.2 × 10−4 (lmmg−mh−n), 2.8, 0.25 and 0.36, respectively. The activation energy was obtained as 37 kJ mol−1. Further, it was proved that the above equation could be applied to the rates of THM formation from precursors in actual river and lake waters.

Adsorption of surfactants on sediments

Abstract Adsorption isotherms of 5 priority surfactants on 7 river sediments were obtained. The surfactants were ready to adsorb in the same order as the adsorption on microbiologies. The adsorbed amounts per gram of the organic carbon in the sediments were nearly equal for most of the sediments.

Adsorption of polyethylene glycol from aqueous solution on montmorillonite clays

Adsorption rates and capacities of polyethylene glycol (PEG) were investigated for five montmorillonite clays. The adsorption of PEG for all the montmorillonite clays was rapid, and equilibrium was attained within 30 min. The adsorption isotherms of PEG for all the montmorillonites conformed to the Freundlich equation. The adsorption heats were 7.3 and 11.6 kJ · mol−1(mw.:2000), and 8.7 and 14.2 kJ · mol−1(mw.:20000) for the montmorillonite and the bentonite II-Ca, respectively. Adsorption capacities for all the clay samples approached constants for the molecular weight of PEG over 2000, though they increased with the increase of molecular weight under 2000. The adsorption capacities were slightly influenced by a nearly neutral pH. The montmorillonite clays which had different interlayer cations showed quite different adsorption capacities. The bentonite II-Ca, the acid clay, and the activated clay showed large adsorption capacities that were 30–50 % of that of an activated carbon.

Equilibria for adsorption of organic compounds on activated carbons in aqueous solutions I. Modified Freundlich isotherm equation and adsorption potentials of organic compounds

Abstract Studies on adsorption isotherms for 16 organic compounds such as benzene mono- or disubstitutes, fatty acids, and aliphatic alcohols in aqueous solutions on five commercial granular activated carbons were carried out at 25°C. It was elucidated that the Polanyi potential theory could only be applied to the adsorptions of sparingly soluble compounds from solutions, and the Freundlich equation could, theoretically, be applied to the adsorptions of sparingly soluble compounds from solutions when the distribution functions of adsorption potential could be approximated by exponential functions. The distributions of adsorption potential for various organic compounds in aqueous solutions on the activated carbons were calculated from the modified Freundlich expression, logarithmic relationship of molar adsorbed amount and reduced concentration. Further, applicability of the Traubes rule and influence of surface oxides of activated carbon on the adsorption potentials of organic compounds were also discussed.

Analysis of Respiratory Quinones in Soil for Characterization of Microbiota

Abstract Method for the analysis of respiratory quinones in soil was developed to characterize soil microbiota. The respiratory quinones were extracted with a mixture of chloroform and methanol using a Wahling blender or a sonicator and cleaned-up by a silicagel column cartridge. The quinone species were determined by reverse-phase high performance liquid chromatography. Spectra of peaks were measured with a photodiode array detector to examine the purity. More than 90% of extractable quinones in soil were recovered by three extractions. The recovery of quinones, added to soil as freeze-dried powder of microorganisms, was higher than 96%. This procedure led to higher representative results as follows. Fluctuations within 95% of cumulative frequency were 13% for the extracted amount of quinones and 20% for the dissimilarity, respectively. The quinone profiles of four soils were determined as follows: a soil from the aerobic layer of a paddy field, an ando soil and two yellow upland soils which had received...

Development of a Novel Solid Phase Extraction Method for the Analysis of Bacterial Quinones in Activated Sludge with a Higher Reliability

A novel analytical method for analysis of microbial quinones in activated sludge sample was developed with improved reliability compared to the conventional method. The operating conditions for the extraction of quinones from activated sludge sample with a methanol-chloroform mixture and hexane were optimized. A solid phase extraction method using the Sep-Pak Plus Silica, a small column packed with silica gel, was employed for the purification and separation of quinones instead of column chromatography and thin layer column chromatography used in the conventional method. The analytical operation was simplified and the analytical time was shortened by a half or two-thirds of that required for the conventional method. The recoveries of quinones were markedly increased from 30-60% with the conventional method to as high as 90-101% with the improved method, demonstrating that the reliability of the analytical results of the improved method is significantly higher than that of the conventional method. The quinone content value obtained using the improved method was twice as high as that obtained using the conventional method for the same activated sludge sample, but the quinone profiles expressed as the mole fraction of each quinone type were the same for each method.

Quantitative analyses of the change in microbial diversity in a bioreactor for wastewater treatment based on respiratory quinones

Abstract The change in microbial diversity in a submerged aerobic biofilter, into which a persistent chemical of dimethylformamide was fed, were analyzed based on the quinone profiles using a new diversity index of the respiratory quinones (DQ) and an index of equitability of the distribution of quinone species (EQ) originally proposed in this study: DQ=(∑ f 1/2 k ) 2 , EQ=DQ/ n . Where, f k is the mole fraction of quinone species k and n is the number of quinone species, respectively. The DQ value increases with an increase in the number and the equitability of the distribution of quinone species. In the case where the mole fractions of all quinone species are equal, the value of DQ becomes equal to the number of quinone species and the EQ value becomes 1. A simulation analyses shows that DQ has a higher sensitivity to the change in number of quinone species than Shannons index, i.e. one of the most widely used diversity indices. The relative sensitivity of DQ to the change in mole fraction of quinone species is higher than that of Shannons diversity index for natural ecosystems in which many kinds of quinone species exist and occupy smaller fractions. The quinone profiles of the biofilm significantly changed and the values of DQ and EQ increased during the acclimation of the biofilm to dimethylformamide in the biofilter. The plot of the mole fraction of dominant quinone species to the DQ values showed higher sensitivity to the change in the microbial community. These results indicated that DQ and EQ are useful indices for the evaluation of the changes in the microbial community in response to environmental conditions.

Adsorption of chlorinated organic compounds on activated carbon from water

Abstract The adsorption capacities and rates of seven principal chlorinated organic compounds for six commercial GACs were investigated. All the adsorption isotherms were expressed by the Freundlich equation, and the isotherms for the chloroethylenes such as trans - 1,2-dichloroethylene, trichloroethylene and tetrachloroethylene could be shown by the modified Freundlich equation Q′ = k′ (C/Cs)l/n for each GAC. The magnitude of adsorption of the chlorinated organic compounds was in the order of: tetrachloroethylene > trichloroethylene >trans - 1,2-dichloroethylene > 1,1-dichloroethane > carbontetrachloride > 1.1,1-trichloroethane > chloroform. The value of k for a certain GAC could be predicted from the quantity of pores smaller than 2 nm in diameter. The adsorbed amounts were decreased by 10–20% when humic substances coexisted. The working periods of a fixed bed adsorber before regeneration were predicted by calculating breakthrough curves for various influent concentrations of trichloroethylene and tetrachloroethylene at the space velocities of 5 or 10 h−1, and it was certified that the adsorption method by GAC was feasible for removing these compounds from water.

Optimal operation of bioreactor system developed for the treatment of chromate wastewater using enterobacter cloacae HO-1

The characteristics of a novel bioreactor system developed for the simultaneous treatment of toxic hexavalent chromium (chromate) and high-strength organic pollution by introducing a chromate-resistant and chromate-reducing bacterium Enterobacter cloacae strain HO-1 (HO-1, hereafter) were studied to optimize its operating condition. Based upon the growth and chromate-reducing kinetics of HO-1, a mathematical model to simulate the change of chromate removal rate per unit volume of bioreactor and that per unit cell mass under the fed-batch operation was proposed. The effects of repeated cultivation of HO-1 with ORP-controlled aeration and the cumulative chromate reduction per unit cell mass on the microbial activity were investigated to represent the kinetic expression of chromate reduction. By using the mathematical model developed through the present research, the relationship between the operating conditions and the chromate reduction rate in the bioreactor was simulated and the model was verified by comparing it with the observed data. Thus the optimal operating conditions to give the higher reduction rate and the longer operating interval with and without aerated cultivation of HO-1 are extensively discussed. This bioreactor can be used for the treatment of chromate wastewater provided that some high concentration organic wastes are available. The rate of chromate reduction in the bioreactor is as high as 10 - 15 g-Cr 6+ /m 3 h. Chromium hydroxide, products of biological chromate reduction, can be recycled as a green pigment.

Recovery of acid from wastewater by electrodialysis

Abstract The optimum operating conditions for electrodialysis using a newly developed membrane were studied for recovery of acid from acidic wastewater released from the iron and steel industry. The limiting current densities I lim / S and the current efficiencies η I could be expressed by the following equations, respectively. Furthermore, the concentration of iron(III) ion should be controlled lower than one twentythird of C , since the electric resistance of the cation-exchange membrane was increased considerably by fouling with iron(III) ion.