This comparison was undertaken on three models of natural organic compounds : an aquatic fulvic acid, a protein and a disaccharide. The first results showed the following order of relative efficiency: O3/TiO2 > O3/H2O2 > O3 as far as Total Organic Carbon (TOC) removal was concerned. 相似文献
- oxido-flocculation, using Fe2+, H2O2
- inter-oxidation, using O3, H2O2 and eventually an heterogeneous catalyst.
- disinfection, using UV, O3 and H2O2 combinations.
Results show that triazines can be removed by all these processes with different efficiencies. At full scale, the O3/H2O2 process presents the best performances from an economical and technical point of view. 相似文献
In optimum Ou/UV system application conditions, the abatement of COD in water from the Seine river is never above 30%. On the other hand, TOC removal is increased in weakly carbonated pond water loaded with humic matter. The O3/UV system also ensures oxidation of saturated volatile organic halogens, with the exception of carbon tetrachloride. 相似文献
The higher rate of TCE oxidation implies that direct reaction occurs with the double bond. Finite reaction rate of DCE with ozone, and substantial increases in rate at higher pH imply the participatation of hydroxyl radicals in the oxidation of both compounds. For example, at pH = 7, initial ozone concentration of 2.3 mg/L, the ko for TCE oxidation by ozone/ultraviolet radiation is approximately 500 M?1 sec?1 almost too fast to measure in a batch system.The rate also is increased by increased ultraviolet radiation intensity, and by the presence of hydrogen peroxide, which acts as a catalyst. 相似文献
All these considerations have led us to use static mixers to transfer ozone into water. This process enables us to control the ozone concentration in water and detention time. It is a very simple system, with very low maintenance requirements due to the lack of moving parts. Civil engineering is minimized. A pilot scale study is presented here. It took place at the Méry-sur-Oise water treatment plant, on a pilot plant working at 8-12 m3/h. It is composed of a static mixer for the transfer of ozone from gas to liquid, linked to an air lift to separate gas from liquid, providing ozonated water.
The optimization of transfer was achieved by studying the impact of water flow, gas flow and ozone concentration in the gas. It is possible to reach 90% of transfer in less than 15 s. Headloss (ΔP) across the mixer is a function of gas and water flows and remains economically very acceptable as 0.15 bar for 12 m3/h.
Atrazine removal was studied using a static mixer, an air lift and a contact pipe 80-m long, providing an optimum contact time phase, working as a plug flow reactor. Ozone and H2O2/O3 treatments were compared. The maximum reduction of atrazine concentrations (e.g., for an infinite contact time) is a function of the amount of transferred ozone, but H2O2 influences the kinetics of the reaction. In the presence of H2O2 with a ratio of H2O2 to O3 of 0.4 w/w, maximum elimination is reached in 2 min 30 s.
The effect of such treatments on environmental bacteria also was followed. A counting of total germs at 20°C showed a decrease of 1- to 3-logs 10 after 1 min 30 s of contact time for about 2 mg/L of transferred ozone. No significant difference between treatments with or without H2O2 was shown. The same conclusions were obtained from heterotrophic plate counts (37°C) and epifluorescence countings. 相似文献
The effect of humic acid and bicarbonate on the removal of TCB was studied. At 1.6 mg/L humic acid, 92–95% of the TCB was oxidized by the processes studied. The removal of TCB by ozone alone was significantly affected by the presence of bicarbonate ion. For the other processes at 10 mM bicarbonate, approximately 80% of the TCB was oxidized. 相似文献
If the ozone dosage is restricted just to reach the required disinfection level at pH 7.2, ozonation is a poor barrier against pesticides. Out of 23 selected pesticides, only 6 were effectively degraded: dimethoate, chlortoluron, diuron, isoproturon, metoxuron and vinclozolin (O3/DOC = 0.55 g/g). Application of an (O3/DOC ratio of 1.0 g/g results in an effective barrier for roughly 50% of the tested pesticides (also for diazinon, parathion-methyl, linuron, methabenzthiazuron, metobromuron, MCPA and MCPP). Pesticides were degraded more effectively at high pH and high temperature.
For additional degradation of high concentrations of persistent pesticides, advanced oxidation may be applied. Atrazine, propazine, simazine, chlor-fenvinphos, tetrachlorvinphos, 2,4-D, 2,4-DP and 2,4,5-T were degraded by O3/DOC = 1.4 g/g and H2O2/O3 = 0.5 g/g. Dicamba and dikegulac were most persistent. pH has a minor effect on the degradation of pesticides by advanced oxidation. Higher hydrogen peroxide dosages showed no improvement in degradation. After ozonation and advanced oxidation, about 50% of totally reacted atrazine and propazine was converted into desethylatrazine. No desisopropylatrazine formation was observed. 相似文献
A correct mathematical treatment is given for calculation of the light absorption of the individual components of a multi-absorbent reaction mixture.
On the basis of the literature data and die present results, a probable chemical and reaction kinetic model was proposed to characterize the investigated reaction systems. Reaction kinetic simulations demonstrated that the model predicts a good fit to the measured data with the preferred literature rate constants, except that for the HO3 radical decomposition reaction. A reasonable reduction of this rate coefficient value is in accordance with the latest published results. 相似文献
The effect of ozonation on membrane flux was found to be largely dependent on raw water quality as well as ozone dose. In case of upstream water (A), preozonation achieved significant flux enhancement regardless of ozone dose. Whereas, for the downstream water (B), the steady state flux was increased or decreased depending on ozone dose.
The analysis based on the resistance-in-series model provided the mechanistic interpretation on the membrane flux variation. Ozonation in an ozone-ultrafiltration system always brought about a decrease in cake resistance (Rc) and an increase in fouling resistance (Rf). Based on the measurement of particle size distribution and zeta potential, the reduction in cake resistance through ozonation was attributed to an increase in particle size due to “ozone-induced particle destabilization”. However, the increase in the fouling resistance seems to be caused partly by the microbial characteristics of raw water.
Although there was little effect on TOC, ozone-UF treatment could get much higher removal of UV 254, THMFP (lday) and THMPF/TOC ratio than UF treatment alone. 相似文献
Generally, increasing levels of CH4 and CO at constant NOX levels will increase O3 and suppress OH. A rough estimate of possible global changes shows tropospheric O3 increasing ?10% from 1980 to 2030 and OH decreasing ?10% during that period. When calculations are performed assuming that stratospheric ozone depletion and climate warming occur at anticipated rates during the same period, tropospheric O3 enhancement and OH loss in nonurban areas are both reduced relative to changes assuming that only CH4 and CO emissions change.
Regional changes in surface-level O3, OH and the water-soluble oxidant H2O2 are estimated for the year 2030. Increases in CO and CH4 suppress OH and enhance O3 and H2O2 in nonpolluted (low NOX) areas. In urban environments (background NOX > 1 ppbv), increases in CO and CH4 add significantly to all three oxidants, O3, OH and H2O2. Changes in and near urban areas may be of greatest magnitude, but the high levels of OH (and H2O2) found in the tropics indicate that perturbations in that region could dominate future global oxidant changes. 相似文献
Ozonation and ozone/hydrogen peroxide decreased the amount of organic material from drinking water by about 20 percent measured as TOC and CODMn. Color and turbidity level reductions were 49 and 11 percent, respectively. Ozonation reduced the AOX concentrations formed during postchlorination from 150 μgL?1 to 75 μgL?1. The addition of hydrogen peroxide further improved the removal to 37 and 26 μgL?1 depending on the ratio of H2O2/O3. The mutagenicity reduction followed the same pattern: without ozonation the chlorination-derived mutagenicity was 1,450 net revertant L?1 after the ozonation 700 and after the H2O2/O3 treatment from <100 to 400 net revertant L?1 depending on the H2O2/O3 ratio. Nanofiltration appeared to be the most effective way to remove organic material. The removal of TOC was 68%, CODM 72%, color 90%, turbidity 68%, AOX 88%, and mutagenicity 85%. 相似文献
Efficiency of the two oxidant systems – ozone and ozone coupled with hydrogen peroxide – is evaluated for 11 pesticides commonly analyzed in control laboratories. Comparison of the two systems is made in terms of pesticide removal, but also in terms of ozone consumption. Matrix effects and contact time are also taken into account, and an order of reactivity for each system considered is suggested. 相似文献
In this research compounds of the different classes were used: glyoxal, pyrrole-2-carboxylic acid, p-toluenesulfonic acid and naphthalene-1,5-disulfonic acid. Depending on the classes of compounds in some cases the elimination rates of the initial compounds is enhanced by using UV/TiO2/O3 compared to UV/O3 or O3 alone. But in all cases greatest DOC elimination is achieved by using UV/TiO2/O3. 相似文献
In order to exclude its toxic effect on the pulmonary epithelium, the medical ozone/oxygen mixture is administered so that exposure of the respiratory tract is avoided at all times, i.e., without the disturbing effects of its odor. 相似文献
Heterotrophic plate counts, and counts of Staphyiococcus aureus and Pseudomonas aeruginosa were lowest when using chlorine, next lowest when using ozone #x002B; UV radiation, and highest when using UV-generated ozone. It is concluded that insufficient dissolved ozone is present for a sufficient reaction time to effect disinfection of these organisms by ozone generated by UV radiation. The fact that the odor of ozone was present above the spa water indicates that contacting also was inefficient. 相似文献
Extensive development work has been performed to optimize the dosage of ozone for water treatment. Potential users are kept informed on this technology through published data. Theory, however, is only one side of the problem, practical application quite another. Here technicians and engineers have been required to integrate oxidation and disinfection with ozone, into the technology for water treatment and to make this economic.
In Switzerland since the 1950s, more than 40 waterworks have been converted to ozone. The development and the experience that has been collected since the introduction of this technique is the subject of this paper, primarily in regard to cost development and cost economy through innovative engineering services for development, engineering and project execution. 相似文献
It has been indicated that the removal of the five species of aromatic nitro compounds by ozonation can well be expressed mathematically by first order reaction equations. Besides, the reaction constants and half-life periods for various species of the tested nitro compounds were calculated at different temperatures and pH.
An ozonation effect index (OI) was developed in the study to express the degree of degradation of substrates by ozonation, by means of which the five aromatic nitro hydrocarbons were compared with each other and finally ranked in the following order from greatest to smallest degrees of degradation:
p-nitroaniline > nitrobenzene > p-dinitrobenzene > p-nitrotoluene > m-dinitrobenzene
It has also found that the CODm/M ratio increases with ozone doses. This means that some easily degradable intermediates are produced, and increase in concentration with increase of ozone dose in the ozonation process.
The mechanisms of removing the five aromatic nitro hydrocarbons are discussed from the viewpoint of orienting effects of substituent groups on the aromatic rings. 相似文献
In each CSTR, the calculation of oxidant concentrations (O3, H2O2) is made through mass balance equations and a semi-empirical formula which gives hydroxyl radical concentrations as a function both of ozone concentration and the main characteristics of the water to be treated (pH, TOC, alkalinity). Another semi-empirical formula links ozone consumption to the same characteristics. 相似文献
The operation of these water treatment systems has shown that safe and high quality pool water is obtained reliably and economically. One pool (Main Pool) is of Olympic size, the other (Learner pool) is designed especially for use by children. Both pools utilize a full corona discharge ozone water treatment system. They were the first ozone systems in the U.S. to be built for public pools using the process of ozonation, flocculation, filtration, ozone removal and residual chlorination.
An extensive testing program was initiated in cooperation with the Wisconsin Department of Health. The bacteriological water quality from these swimming pools was in compliance with Wisconsin State Health Regulations and the German DIN Standard 19,643.
The first year of operation of the Peck Aquatic Center has shown that the corona discharge ozone pool water treatment process can:
1) Operate reliably in a public swimming pool environment without the need for highly or special operator qualifications.
2) Produce continuously bacteria- and virus-free pool water without the harmful and unpleasant effects of chlorine.
3) Creates a user constituency group praising and promoting the use of “minimal chlorine swimming” in the community. 相似文献
The experiments were conducted both on a synthetic water, with or without addition of humic substances, and on raw water from the Moulin-Papon dam. While iron was easily removed by simply increasing the pH measurement from 8.2 to 8.5 without intermediate oxidation, ozonation applied to water with a pH of nearly 8.4 did not enable the manganese to be removed with a low ozone dose (about 1 mg/L) unless a significant amount of bicarbonates (120 to 130 mg/L as CaCO3) were injected prior to the ozonation-filtration stage.
As it removes the manganese from the water, intermediate ozonation also removes the abatement of organics on the filters, and lowers the THM buildup potential. 相似文献