摘要:

A laboratory study has been designed to investigate the decomposition of ozone in natural water and to determine its potential to produce hydroxyl free radicals for the oxidation of micropollutants during the ozonation process of drinking water. This report describes the first data obtained using a continuous flow reactor capable of observing reactions with relatively short time scales (Q = 34 mL/min; 1.4 < tc< 27 sec). Rates of ozone decay were studied in fulvic acid solution in the presence, or in the absence of radical scavenger (tert-butyl alcohol) or of promoter of ozone decomposition (formic acid), and a micropollutant of interest (tetrachloroethylene). Also, three natural waters were studied, illustrating that OH radical formation depends on chemical composition of the waters.

ISSN:0191-9512    

DOI:10.1080/01919519208552474

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The efficiency of ozonation and advanced oxidation processes such as ozone/UV, ozone/H2O2and H2O2/UV was assessed for chlorinated hydrocarbons using a closed batch-type system. 1,1-Dichloropropene (DCPE), trichloroethylene (TCE), 1-chloropentane (CPA), and 1,2-dichloroethane (DCA) were used as model compounds.

ISSN:0191-9512    

DOI:10.1080/01919519208552475

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Oxalic acid is chosen as a model compound to study the UV + O3reactions in an heterogeneous continuous gas sparging reactor. Oxalic acid has the advantage of not reacting significantly with ozone alone, and when oxidized with O3+ UV radiation, the reaction is of the single-step type : HOOC-COOH + O3(UV) = 2 CO2+ H2O + O2. The reactions are of zero order as long as no additional alkalinity is introduced into the system. Evidence is that the photolysis of ozone is produced in the gas phase and that the reaction occurs in the gas-liquid boundary layer.

ISSN:0191-9512    

DOI:10.1080/01919519208552476

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This paper builds on a prior paper by this author, McGrane (1991). In that paper, ozone is used as the sole means of cooling tower water treatment. The paper discusses water conservation by increased cycles of concentration, greatly increased efficiency through extremely low biological populations, and corrosion data which is compared to ozonated and chemically treated towers.

ISSN:0191-9512    

DOI:10.1080/01919519208552477

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Residence time distribution (RTD) experiments are carried out in a pilot plant (QL = 1 m3.h−1). The RTD curves are analyzed by the completely mixed reactors in series model or by the axial dispersion model. Measurements are performed either on the overall bubble column or on four equal parts of the reactor. The bottom part (gas introduction) is completely mixed. The top part (water introduction) is a mixed reactor in which the middle parts are plug flow reactors with a weak axial dispersion coefficient. Dissolved ozone measurements along the column are in agreement with that model which allows a reactor modelization to compute the dissolved ozone profiles.

ISSN:0191-9512    

DOI:10.1080/01919519208552478

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The presence of pesticides in water sources and their removal by treatment processes is of particular interest currently to water companies and research scientists. Although operators and scientists are debating whether the related standards and legislation are too stringent, the current European Drinking Water Directive stipulates a maximum contaminant level (MCL) of 0.1 μg/L for an individual pesticide. Atrazine is amongst the most frequently identified pesticides in water supply sources. Since conventional treatment processes (chlorination, coagulation and filtration) are unable to reduce this micropollutant to an acceptable concentration, two advanced technologies are being investigated extensively; namely, adsorption onto activated carbon, and ozonation, particularly ozone combined with hydrogen peroxide. As for ozonation, several authors (Glaze et al., 1987; McGuire and Gaston, 1988; Terashima, 1988; Ferguson et al., 1991) have reported that the removal of refractory organics (e.g., 2-methyl isoborneol – MIB and geosmin) by ozone appears to be more effective in natural waters than in pure water solution; this was attributed to the action of natural organic material in water (such as humic substances) which promotes the radical reactions of ozone. In other more fundamental studies (Staehelin and Hoigné, 1985; Xiong and Legube, 1991), humic substances were speculated to be involved in radical decomposition of ozone in solution.

ISSN:0191-9512    

DOI:10.1080/01919519208552479

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Three ketoacids; glyoxylic acid, pyruvic acid and ketomalonic acid, were identified in ozonated drinking waters and fulvic acid solutions using gas chromatography-mass spectrometry. It was found that the concentrations of ketoacids were much higher than those of aldehydes in ozonated waters. The significance of ketoacids in finished drinking waters is discussed.

ISSN:0191-9512    

DOI:10.1080/01919519208552480

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0191-9512    

DOI:10.1080/01919519208552481

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0191-9512    

DOI:10.1080/01919519208552473

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor