Shogo Taniguchi

The usefulness of ultraviolet-C (UVC: 254nm) and vacuum UV (VUV: 185+ 254nm) photolysis for elimination and mineralization of four selected pharmaceutical compounds (PhCs) in mixed aqueous solution were tested in laboratory batch experiments. UVC photolysis was unable to eliminate moderate and refractory PhCs. Moreover, it was not at all useful for mineralization of the PhCs (<10% TOC removal, 30min reaction) and longer reaction period (i.e. 60min) had no significant positive impact on the mineralization efficiency. On the other hand, VUV photolysis eliminated the PhCs almost completely in a short reaction period irrespective of their nature, and 90% mineralization was achieved in an hour. The greatly enhanced elimination and mineralization efficiencies for VUV photolysis were attributed to accelerated direct and indirect photolysis reactions. Based on the results, it was concluded that VUV photolysis was very promising over UVC photolysis for mineralization of PhCs in mixed aqueous solution. However, more studies are necessary for practical applicability of the method in wastewater treatments.

© 2015 The Surface Science Society of Japan. We have conducted a pilot study of a biological filtration (BF) system for low-cost arsenic (As) removal from groundwater containing both ferrous iron (Fe(II)) and arsenic (As). Throughout the study, we have observed that arsenite (As(III)) as well as arsenate (As(V)) could be removed with this system. In conventional water treatment technologies, the preoxidation of As(III) to As(V) by oxidizing chemical is a mandatory step for As(III) removal However, such a preoxidation unit has not been used in our BF pilot unit, and hence the mechanisms of As(III) removal by BF have been of interest. Using a flow-through column reactor that simulates the actual BF pond for analysis by X-ray absorption spectroscopy (XAS), we could observe the adsorption of As(III) in water onto iron hydroxides deposited on the biological filter. The time-resolved As K-edge X-ray absorption near-edge structure (XANES) spectra were obtained when the water containing As(III) and Fe(II) was continuously fed to the reactor. An increase in the absorption intensity of the X-ray with time was clearly observed in the time-resolved spectra, indicating that the spectra represented the concentration and chemical state of As adsorbed at the solid-liquid interface of the biological filter. The XAS results also show that while the original water fed to the reactor was supposed to contain only As(III) and Fe(II), a small portion of As(III) was oxidized to As(V) in the influent line when the As(III) solution met the Fe(II) solution before flowing into the reactor. Consequently, besides As(III), As(V) probably formed by the oxidation of As(III) in the influent, was detected on the filter by XAS. The results demonstrate that, in BF, mechanisms of As(III) removal are at least partially explained by the adsorption of As(III) in the raw water to the biological filter as it is.

This article aims to elucidate on usefulness of vacuum ultraviolet (VUV) for photoreductive degradation of perfluorooctanoic acid (PFOA), a representative perfluorinated compound (PFC), in water for the first time. Bench-scale tests were conducted on oxidative and reductive (with aquated electron: e (aq) (-) ) mineralization of PFOA using low-pressure UV (LPUV) lamps and potassium iodide. Unlike with 254 nm wavelength (UVC), the reductive mineralization with VUV was very inefficient compared to the corresponding oxidative mineralization. The inefficiency is attributed to low reactivity of e (aq) (-) with PFOA and its fluorinated products than that of 185 nm photons. Direct VUV photolysis of PFOA and its products in reductive reaction conditions was not apparent due to a very big difference in reactivity of 185 and 254 nm photons with iodide. The results demonstrated that highly energetic VUV photons are not suitable for photoreductive degradations of PFCs involving e (aq) (-) , but they can be best used for oxidative degradations. These findings should serve as an important reference on VUV usage to decompose refractory micropollutants.

Ultraviolet (UV) photolysis of sixteen pharmaceutical compounds (PhCs) in mixed solutions with four types of water and two sets of UV radiation was investigated. UVC (254 nm) photolysis was ineffective at eliminating a large number of PhCs while a big number of them were refractory. However, vacuum UV (VUV: 185 nm + 254 nm) photolysis in the same experimental conditions eliminated the PhCs almost completely. The eliminations in ultrapure water (UPW), tap water (TW) and Neya River water (NRW) and their organic/inorganic contents were inversely correlated, which was more evident in VUV photolysis. Natural organic matter (NOM) in NRW did not have an impact in indirect photolysis, but effluent organic matter (EfOM) in secondary-treated effluent (NWTPE) enhanced indirect photolysis, which was more evident in VUV photolysis underlining the point that radiation wavelength/intensity can be a limiting factor in organic-rich waters. Moreover, VUV photolysis was far superior (90% mineralization) to UVC photolysis (10% mineralization) for PhCs mineralization. The greatly enhanced elimination and mineralization efficiencies observed for VUV photolysis were attributed to accelerated direct photolysis with 185 nm wavelength and indirect photolysis involving (OH)-O-center dot. The results demonstrated efficacy of VUV photolysis in wastewater treatment and its potential use as a tertiary treatment.

With the view of their importance in photochemical reactions, impacts of five selected parameters (UV wavelength/transmission, perfluorooctanoic acid (PFOA) concentration, dissolved oxygen (DO), solution pH and water quality) on PFOA photodecomposition in water were investigated for the first time in our knowledge. Laboratory batch tests using a glass reactor (1.5 L), a low pressure UV (LPUV) lamp (20 W) and two types of lamp sleeves were carried out. Ultrapure water (UPW), tap water and urban river water were used in "water quality effect" tests, while UPW was used in all other tests. UV wavelength and transmission showed profound impacts on PFOA photodecomposition. The compound was more easily decomposed by vacuum UV (VUV: 185 nm) than by UVC (254 nm). No visible impact of PFOA concentration (0.12-2.42 mu M) on its elimination ratio was observed. The inverse correlation observed between defluorination ratio and PFOA concentration was attributed to UV photon-limited condition for larger PFOA concentrations combined with stepwise photodecomposition of PFOA. DO in reaction solution had negative impact on PFOA elimination, while abundant DO in solution was detrimental for its photomineralization. Though no clear-cut impact of solution pH (3.0-10.0) on PFOA photomineralization was observed, pH 3.0 was relatively better. Water quality also profoundly impacted PFOA photomineralization. Organic constituents and bicarbonates were directly and indirectly responsible for drastic decrease in PFOA photomineralization in organic-rich waters. These findings may serve as basic information for photodecomposition of similar other perfluorinated compounds (PFCs). (C) 2011 Elsevier B.V. All rights reserved.

The widespread detection of perfluorinated compounds (PFCs) in the water environment has been a concern for the last several years, while effluents from wastewater treatment facilities are the major sources of these compounds. Even advanced oxidation technologies (AOTs) are not useful for mineralization of the compounds due to their very high stability. Photochemical techniques using particularly vacuum UV (VUV) have been found to be very promising in this regard. But the use of VUV in UV-based AOTs has still not progressed much. Moreover, the impact of water quality on PFCs photomineralization is unknown. This investigation aimed to assess photomineralization potentials of perfluorooctanoic acid (PFOA) in ultrapure water (UPW), tap water (TW), surface water and treated wastewater effluent using a reactor setup enabling maximum utilization of VUV emission of low pressure lamp in laboratory batch experiments. Neya River water (NRW) and the Nakahama Wastewater Treatment Plant Effluent (NWWTPE) represented surface water and treated wastewater effluent respectively. Also, tests were carried out in 50% diluted NRW and NWWTPE. PFOA photomineralization in terms of PFOA removal, defluorination and total organic carbon (TOC) removal are discussed. The usefulness of the method for PFOA mineralization in organic-rich wastewaters, and further research needs are also highlighted.

Perfluorooctanoic acid (PFOA) is very persistent in the environment and widely detected in the water environment. Only some advanced methods with extreme reaction conditions are shown to be capable of degrading the compound efficiently, and almost all the earlier investigations used very high PFOA concentrations. The compound is detected normally at very low concentrations in the water environment, while mild reaction conditions for its degradation are preferable. This article aimed to elucidate photodegradation of PFOA in dilute aqueous solutions by combined UV wavelengths (185 nm + 254 nm) and 254 nm using a newly designed UV jacket. PFOA degradation was greatly enhanced with the combined wavelengths with almost one hundred percent PFOA removals in four-hour reaction. The removals were well described by the first-order reaction kinetic. The removal efficiencies and rate values significantly decreased with smaller initial PFOA concentrations. But defluorination was greatly enhanced with smaller PFOA concentrations possibly due to accelerated decomposition of fluorinated intermediates of PFOA. Formic acid and acetic acid were two tentatively identified intermediates of PFOA photolysis while the former was a major intermediate predominantly controlling solution pH during the oxidation. The results demonstrated that PFOA photolysis by the combined wavelengths with mild reaction conditions can be greatly enhanced by proper design of UV jacket and reactor system.

Ultraviolet photolysis and ultraviolet and hydrogen peroxide oxidation of fourteen commonly used pharmaceutical compounds and two personal care products in mixed solution using low pressure ultraviolet lamp was investigated in laboratory batch experiments. Removal of the compounds followed the first-order reaction kinetic. Three distinct impacts of hydrogen peroxide on ultraviolet and hydrogen peroxide oxidation of the compounds (positive, negative and no significant effect) were observed. Removal behavior of the several tested compounds in mixed solution varied significantly than their respective behavior in absence of coexisting compounds. Clofibric acid, diclofenac, fenoprofen, isopropylantipyrine, ketoprofen, phenytoin and triclosan were removed very efficiently (&gt 96%) by ultraviolet photolysis alone. Residual hydrogen peroxide during ultraviolet and hydrogen peroxide oxidation was quantitated for the first time. Hydrogen peroxide addition to ultraviolet photolysis was not worthy for majority of the tested compounds as their removal did not increase significantly and very big fractions (&gt 85%) of the added hydrogen peroxide (0.29 ~ 1.47 mM) remained unused presumably due to small fluence of the lamp, very small molar absorption for hydrogen peroxide at 254 nm (27.06 /M.cm) and acidic pH of reaction solution (&lt 5.7). Further exploration on ultraviolet and hydrogen peroxide oxidation with higher fluence lamp and alkaline solution pH will clarify usefulness of the method to treat pharmaceutical contaminated waters. © IRSEN, CEERS, IAU.

Presence of chlorinated organic compounds in water bodies has become a concern among governments, health authorities and general public. Oxidation of organic compounds in water under high temperature and pressure is considered as a promising technique, but usefulness of the technique to mineralize 2,4-dichlorophenoxyacetic acid (2,4-D) is not well understood. This article aimed to elucidate degradation characteristics of 2,4-D in both subcritical and supercritical waters by laboratory batch experiments. 2,4-D degradation, total organic carbon (TOC) removal and dechlorination increased with increasing reaction time and temperature especially in subcritical waters, while dechlorination was a major step. 2,4-dichlorophenol (2,4-DCP) and acetic acid were the main degradation intermediates both in subcritical and supercritical waters. Though 2,4-D disappeared almost completely in subcritical waters near critical region (approximate to 99%), significant amounts of TOC and organic chlorine still remained as 2,4-DCP and acetic acid. But TOC removal and dechlorination were significantly enhanced (approximate to 95 and 91% respectively) in supercritical waters. Complete mineralization of 2,4-D in subcritical waters required a considerably longer reaction period, while the mineralization was almost complete within a short reaction period in supercritical waters. This is an important information of practical significance for oxidative degradation of chlorinated pesticides similar to 2,4-D.

Widespread detection of pharmaceutical compounds in water environment has been a serious concern recently, while conventional sewage treatments are ineffective for their elimination. But, advanced oxidation techniques are very promising to remove varieties of organic contaminants in water. This research aims to elucidate oxidation potentials of sixteen commonly used pharmaceutical compounds in mixed solutions by seven advanced oxidation techniques in laboratory batch experiments. The removal profiles exhibited four distinct patterns: a) easily degradable by all seven techniques, b) not easily degradable by all seven techniques, c) easily degradable by ozone-based techniques, but not by ultraviolet radiation-based techniques and d) easily degradable by ultraviolet radiation-based techniques, but not by ozone-based techniques. Ozone-based techniques rather than ultraviolet radiation-based techniques were very powerful for simultaneous removal of the compounds efficiently. Moreover, ozonation combined with ultraviolet radiation was the most appropriate technique for simultaneous removal of the tested compounds efficiently. Increased ozone dissolution and decomposition with ozone-based techniques did not always enhance the compounds' removal. Physicochemical properties of the compounds and solution pH also presumably played an important role on the removal which merits further attention. © IRSEN, CEERS, IAU.

More effective techniques are required to mineralize the increasing number of recalcitrant organic contaminants at low concentrations in the water environment using advanced oxidation process. Though relatively new, photocatalytic ozonation (O3/UV/TiO2) is considered superior to ozonation (O3) and photocatalysis (UV/TiO2), due to synergistic effects and use of immobilized TiO2 photocatalysts is a milestone in advance oxidation process. This article aimed to elucidate 2, 4-dichlorophenoxyacetic acid (2, 4-D) mineralization characteristics in low aqueous solutions by O3/UV/TiO2 using the world's first high-strength TiO2 fiber catalyst in laboratory experiments. 2, 4-D degradation and TOC removal in O3, UV/TiO2 and O 3/UV/TiO2 followed pseudo-first order reaction kinetic. The removal rates for 2, 4-D and TOC in O3/UV/TiO2 were respectively about 1.5 and 2.4-fold larger than the summation of the corresponding values in O3 and UV/TiO2. The O 3/UV/TiO2 process was characterized by short-lived few aromatic intermediates, faster degradations of aliphatic intermediates and dechlorination as a major step in 2, 4-D mineralization. The significantly enhanced 2, 4-D mineralization in the process was attributed to increased ozone decomposition and reduced electron-hole recombination on TiO2 surface resulting to a large number of ·OH generation. The O3/UV/ TiO2 process with the TiO2 fiber catalyst was very promising with respect to the major challenges being faced in AOP involving TiO2, namely separation of powder catalyst in suspension and reduced efficiency of immobilized catalysts (e.g. TiO2 film/fiber). © IRSEN, CEERS, IAU.

This paper aims to elucidate retention characteristics of some pharmaceuticals and personal care products (PPCPs), and endocrine disrupting chemicals (EDCs), by two polyamide low pressure reverse osmosis (LPRO) membranes. Feed solution pH did not have an influence on rejections of undissociated solutes, which was most likely governed by adsorption, size exclusion and diffusion simultaneously. Size exclusion was presumably dominant, especially with tight membranes (UTC-70U). Rejections of the solutes with low dipole moment (< 1.0 debye) decreased with increasing octanol-water partition coefficient (K(ow)). The solutes with large Kow values were most likely adsorbed on membrane and subsequently passed through it resulting in larger diffusion coefficient (D(p)). The rejections decreased with increasing Dp values irrespective of their dipole moments. Rejections of solutes with comparatively larger dipole moments might be dominated by diffusion and/or convection rather than their hydrophobicity. However, rejections of solutes with hydroxyl and carboxyl functional groups by UTC-60 increased with solution pH. More than 80% rejections were obtained for degree of dissociation (alpha) > 0.5. Electrostatic repulsion played a key role for rejection of dissociated solutes, especially by loose LPRO membranes. Therefore, assessing the dissociation degree at desired pH values can be a key step to obtain an insight of rejection mechanisms by polyamide membranes.

Photocatalytic ozonation (O(3)/UV/TiO(2)) is an emerging oxidation method for recalcitrant organic contaminants in water. However, immobilised TiO(2) catalysts suffer from reduced photonic efficiency. Therefore, TiO(2) catalysts with excellent mechanical and thermal properties and enhanced photonic efficiencies are sought. This paper aimed to elucidate the mineralisation of low concentration 2,4-D (45.0 mu M) by O(3)/UV/TiO(2) using the world's first high-strength TiO(2) fibre in laboratory batch experiments. 2,4-D degradation and TOC removal followed pseudo first-order reaction kinetic. The removal rates for 2,4-D and TOC in O(3)/UV/TiO(2) were 1.5 and 2.4-fold larger than the summation of the values for ozonation (O(3)) and photocatalysis (UV/TiO(2)), respectively. O(3)/UV/TiO(2) was characterised by few aromatic intermediates with low abundance, fast degradations of aliphatic intermediates and dechlorination as a major step. The significantly enhanced 2,4-D mineralisation in O(3)/UV/TiO(2) was attributed to increased ozone dissolution and decomposition, and reduced electron - hole recombination resulting in large number of hydroxyl radical ((center dot)OH) formation from more than one parallel path. The discrepancies in the organic carbon mass budget were attributed to few apparently major unidentified intermediates, while chlorine mass balance was reasonably acceptable. The mineralisation efficiency of O(3)/UV/TiO(2) with the TiO(2) fibre can further be enhanced by optimisation of experimental design parameters. The new TiO(2) fibre is very promising to overcome the problem of reduced efficiency of TiO(2) catalyst in an immobilised state.

More efficient oxidation methods are needed to degrade especially newly emerging recalcitrant organic contaminants at. low concentrations in the water environment. Reduced photonic efficiency of immobilized TiO2 is a major challenge in TiO2-assisted advanced oxidation processes (AOP). Mineralization of 2,4-dichllorophenoxyacetic acid (2,4-D) in low aqueous solution by O-3/UV/TiO2 using the world's first high-strength TiO2 fiber was investigated and compared with O-3, UV/TiO2, and O-3/TiO2 in laboratory batch experiments. The 2,4-D degradation and total organic carbon (TOC) removal followed pseudo first-order reaction kinetic, while their rates in O-3/UV/TiO2 were respectively about 1.5 and 2.4 times larger than the summation of the values in 03 and UV/TiO2. The O-3/UV/TiO2 was characterized by few aromatics with very low abundance, fast disappearance of aliphatics and more than 95% dechlorination. The discrepancies in organic carbon mass balance among the intermediates and 2,4-D were attributed mainly to few apparently major unidentified intermediates. The significantly enhanced 2,4-D mineralization in O-3/UV/TiO2 was attributed to increased ozone dissolution followed by its decomposition, and reduced electron-hole recombination in presence of dissolved ozone resulting in a large number of hydroxyl radical (center dot OH) generation from more than one parallel path. The removal efficiencies of the systems can further be enhanced by optimizing design parameters, and O-3/UV/TiO2 with the TiO2 fiber is promising to mineralize recalcitrant organic contaminants in water at low concentrations.

This paper aimed to elucidate electrochemical degradations of sixteen common pharmaceuticals and personal care products (PPCPs)(Fenoprofen, Ibuprofen, Ketoprofen, Phenacetine, Naproxen, Indomethacin, Diclofenac, Isopropylantiprine, Clarithromycin, Gemfibrozil, Clofibric acid, Carbamazepine, Phenytoin, Phenobarbital, Methoxsalen and Triclosan) using newly developed porous ceramic electrodes in presence of sodium chloride by laboratory batch experiments. Based on their degradations, the PPCPs were classified into three groups: easily degradable (Isopropylantipyrine, Diclofenac, Naproxen, Indomethacin, Triclosan and Gemfibrozil), degradable in relatively longer time (Phenacetine, Clarithromycin, Methoxsalen and Carbamazepine) and difficult to degrade (Ibuprofen, Ketoprofen, Phenobarbital, Clofibric acid, Phenytoin and Fenoprofen). Adsorption of the PPCPs on electrodes was an important phenomenon. The values for Triclosan; Indomethacin, Clarithromycin and Methoxsalen; and others were about 100%, 30% and less than 20%, respectively. Though free chloride species played an important role on PPCPs removals, the degradations due to free chloride only were significantly smaller than the degradations by electrochemical process. Based on the results of this investigation, it is concluded that electrochemical process with the new porous ceramic electrodes is an efficient and promising oxidation method for PPCPs.

Concentration of 2,4-dichlorophenoxyacetic acid (2,4-D) may affect its degradation kinetics in advanced oxidation systems, and combinations of two or more systems can be more effective for its mineralization at low concentration levels. Degradations and mineralizations of 0.045 mM 2,4-D using O-3, O-3/UV, UV/TiO2 and O-3/UV/TiO2 systems were compared, and influence of reaction temperature on the mineralization in O-3/UV/TiO2 system was investigated. 2,4-D degradations by O-3, O-3/UV and UV/TiO2 systems were similar to the results of earlier investigations with higher 2,4-D concentrations. The degradations and total organic carbon (TOC) removals in the four systems were well described by the first-order reaction kinetics. The degradation and removal were greatly enhanced in O-3/UV/TiO2 system, and further enhancements were observed with larger 03 supplies. The enhancements were attributed to hydroxyl radical ((OH)-O-.) generation from more than one reaction pathway. The degradation and removal in O-3/UV/TiO2 system were very efficient with reaction temperature fixed at 20 degrees C. It was suspected that reaction temperature might have influenced (OH)-O-. generation in the system, which needs further attention. (c) 2006 Elsevier Ltd. All rights reserved.

Sediment pollution by hazardous organics like dioxins and Polychlorinated Biphenyls (PCBs) has become a problem these days. Since factors like specific surface area and organic carbon content of sediments influence adsorption/desorption characteristics of hazardous organics, grain-size may affect removals of the organics in contaminated sediments. This paper aimed to investigate grain-size effect on removals of dioxins and PCBs by indirect thermal desorption method. Sieved (75-2000 μm, 20-75μm and >20 μm fractions) and not sieved contaminated sediment samples were heated in quartz tubes up to 400°C. Concentrations of organics were measured in the remaining sediment samples and off-gas colleted during the experiments. Grain-size did have influence on dioxin removals and the removal efficiency increased with smaller grain-size fractions. About 95% removal efficiency was observed in less than 75μm fractions. However, almost the same removals (>99%) were observed with all the sediment fractions in case of PCBs. Therefore sedimentation can be an effective step before remediation of dioxin-contaminated sediments by indirect thermal desorption technique.

Pollution of the soil environment by Polycyclic Aromatic Hydrocarbons (PAHs) and dioxins has become a subject of concern these days. Indirect thermal desorption method has been one of the effective remediation techniques for soils contaminated with several hazardous organic substances. This method could be effective for treating PAHs and dioxins contaminated soils also. The objective of this paper is to elucidate on degradation characteristics of PAHs and dioxins in contaminated soils using indirect thermal desorption method. The contaminated soil was heated in a quartz tube from 200°C to 600°C. The exhaust gas was analyzed for evaporated pollutants while the soil after heating was analyzed for the remaining pollutants. Most of the PAHs were removed from the soil when heated over 200°C. The PAHs with low boiling points evaporated easily while those with high boiling points remained in the soil on heating. The remaining PAHs in the soil most probably degraded to PAHs with low boiling points including other compounds on continued heating and subsequently evaporated. Most of the dioxins in the contaminated soil degraded when heated over 400°C. The traces of metals found in the contaminated soil presumably played as catalyst resulting in dioxin degradation at relatively low temperatures in this case. The results indicated that dechlorination was not a major process in dioxin degradation by this method.

This study aimed to investigate the effects of coexisting substances on separation of endocrine disrupting chemicals (EDCs) in water and domestic wastewater effluents using low pressure reverse osmosis (LPRO) membrane. The coexisting substances included calcium chloride, glutamic acid sodium salt, acetic acid and humic substances whose molecular weight ranged up to twenty thousand. The results showed higher rejection of nonylphenol in a mixed solution of the coexisting substances. Thus, the results indicated that coexisting substances can affect rejection properties of EDCs in LPRO membranes. In using higher desalting membranes, much higher rejection rates of EDCs in domestic wastewater effluents were observed compared to rejection of a single solution, which shows over 95% rejection. However, rejection of E2 from domestic wastewater did not increase with relatively loose membrane.