Oxidation experiments have also been extended to pyrazine, and its sensitivity to only radical ozonation is shown. 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 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
The direct reaction between substrates and ozone predominated at lower pH, which resulted in the efficient oxidation of the olefin, DCPE. At higher pH, ozonation resulted in more efficient oxidation of the chlorinated alkanes, with a corresponding decrease in the efficiency of DCPE oxidation. Consistent results were observed for ozone/H2O2 and ozone/UV treatment. Due to slow UV-induced decomposition of H2O2, the process using H2O2/UV (254 nm) resulted in very slow oxidation of all four compounds.
The total ozone requirement to achieve a given degree of elimination (to 37% of the original concentration), δ0.37, was used to assess the combined effects of the direct and indirect reactions for different types of waters. 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
Prechlorination was not conducted in the ongoing pilotplant experiment of an advanced water purification process with ozone and granular activated carbon. It is necessary, therefore, to oxidize manganese by the oxidative effect of ozone instead of prechlorination.
It is important for the treatment of manganese to adjust the ozone dosage because manganese is oxidized up to the soluble septavalent state by the surplus ozone. Since ozone does not continue to exist for very long in water, though its disinfecting power is high, final disinfection by chlorine is required. 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
The study of the interactions between those reactants has been made according to the following main topics :
As for THM formation, experiments conducted on simple organic compounds or on natural fulvic acids show important decreases in THM or TCAA formation after ozonation. It may be noticed, however, that the ozonation of surface waters may induce the formation of haloform precursors, usually with a low level of reactivity.
In water supplies containing bromide ions, oxidation of the latter through hypobromous acid may take place during the ozonation stage. Failing preozonation treatment, hypobromous acid is generated very rapidly during chlorination, thus inducing the formation of chloro- brominated organic compounds.
During the ozonation of fulvic acid solutions, the presence of small amounts of bicarbonate was found to improve precursor removal significantly.
It can be concluded that the partial analogy of the action of ozone or chlorine on aromatic structures, whether simple or complex (such as humic and fulvic acids), seems to indicate that the consequence of preozonation is the destruction, at least in part, of the most reactive sites for THM production, thus leading to a decrease of the volatile organochlorinated compounds formed during the post-chlorination. However, some ozonation products of natural waters are THM precursors, though of low reactivity. Then, in the presence of bromide ions, the formation of volatile organobrominated compounds may be observed during ozonation. 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
Predicted products fell into one of permanent gases, tight liquids, phenolics and carbonaceous residue fractions. Product yields were more dependent on lignin type than on reaction environment.
Comparison of simulation predictions with experimental pyrolyses of actual lignins, accomplished in terms of both product identities and yields, is encouraging. It is noteworthy that the simulations are strictly a priori and incorporate no actual lignin pyrolysis information. 相似文献
Greatly enhanced mass transfer coefficients kL are measured whilst simultaneously maintaining low ozone loss. Comparisons of kL and volumetric coefficient, kL a values, are made with more conventional packed or bubble columns.
Acetic acid, 2-propanol and 4-nitrophenol, representing a wide reactivity range, are used to elucidate the applicability of rotating contactors in effluent treatment. It has been possible to study the effects of surface activity on mass transfer with subsequent reaction and to generate design data for the next generation of rotating contactors. 相似文献
A study of ozone efficiency and yield concerning the reduction of TOC and COD levels is presented. The biological degradability.of treated water is discussed. A design and rating calculation procedure for countercurrent contactors is presented. Various waste treatment strategies using separation processes and ozone are discussed briefly. A cost estimate to treat a typical dye effluent in two stages on industrial scale is included. 相似文献
Experiments with manganese allowed the determination of second order rate constants for the reaction of ozone with manganese at various pH values. The oxidation of manganese in the presence of organic matter occurred in competition with oxidation of the organic matter. As a result, high ozone doses were required to achieve the same degree of removal of manganese. An increase in bicarbonate alkalinity from 50 mg/L to 200 mg/L did not result in an acceleration of the manganese oxidation in the absence of organic matter. However, in the presence of organic matter, higher levels of bicarbonate created conditions that resulted in more complete oxidation of the manganese following total consumption of the dosed ozone. 相似文献
Samples of logyard run-off were obtained from two British Columbia coastal sawmills. Ranges obtained for measured parameters of these samples were as follows: COD 2400-8700 mg/L, tannins and lignins 160-2500 mg/L, BOD 190-1900 mg/L, acute (Microtox) toxicity EC50 2%–27% v/v. Centrifuged samples were treated with ozone doses up to approximately 0.5 mg ozone/mg COD in a lab-scale reactor.
Ozonation was found to significantly reduce toxicity (80%-90%), tannin and lignin (TL) (90%-95%) and dehydroabietic acid (DHA) (95%-100%) levels. There were moderate reductions in COD (30-35%) and BOD (15%-25%). At slightly acidic to neutral pH, pH had no effect on the rate of COD oxidation; TL and toxicity removal were slightly improved in neutral solutions compared to acidic ones, while DHA removal significantly improved 相似文献
In the pH range of 7 to 9, the TNT destruction rate increases with the hydrogen peroxide and hydroxyl ion concentrations with exponents of 0.104 and 0.15 respectively. It is technically feasible to treat toluene and TNT contaminated waters by the peroxone oxidation process to achieve the residual level of a few parts per billion in treated waters to meet environmental requirements. 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 raw water obtained from 100 different wells will be purified by a water treatment plant of 150,000 m3/day capacity. Considering the high iron content (0.05–0.15 mg/L) and manganese content (0.05–0.2 mg/L), the raw water fails to comply with the requirements of the potable water standard.
Since 1990, over a period of three years, we conducted water purification experiments in several stages. In these, three methods of oxidizing as well as single and double layer open rapid filters were applied to oxidize the manganese (and, to a lesser extent, the water) present in dissolved form, resp., to destroy various living organisms.
In the course of the experiments, it became clear that the chlorine and chlorine + air methods are efficient in case of a small quantity of iron to be oxidized and only 20–25% of the dissolved manganese content could be oxidized.
Neither of the two methods could ensure firm management of microbiological and bacteriological characteristics. The best results were obtained by ozone oxidation, in which case the chemical oxidizing process was almost fully completed and even the chlorine-resistant living organisms could be destroyed.
On the basis of the experiments carried out, the investment program of the water treatment plant was worked out and the conditions of an international tender were compiled whose winner will be commissioned to build up the water works in the time period 1993–1996. One of the main steps of the proposed technology is the ozone treatment. 相似文献
The results obtained in the field confirm the synthesis of some aliphatic carbonyl compounds of low molecular weight. This phenomenon happens preeminently during the ozone disinfection process and, secondarily, during the other disinfection processes.
Experimental results show that, in this last event, chlorine reacts with organic substances, and in a second moment, after organics consumption, if chlorine is still in a sufficient concentration, oxidizing them. 相似文献
In the fresh water system, the separating effect of the ozonated water on the microorganisms such as the sphaerotilus and the zoogloea which adhere to the piping and form the slime is recognized. When the ozonated water is supplied intermittently to the piping without stopping the flow of the cooling water, a constant volume of cooling water can be maintained. At the velocity of 1 m/sec, the amount of metal corrosion produced by the ozonated water is reduced on the mild steel, increased on the copper and does not change on the cast iron, when compared with that produced by the water containing no ozone.
In the seawater system, since many substances are oxidized by the ozone, the same treatment as that in the fresh water system cannot be applied. However, if the seawater in the cooling system can be replaced with ozone-containing air intermittently once a week, the adhesion of organisms such as barnacles and mussels to the piping can be prevented without having a bad influence on the other living oceanic organisms. 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