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
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
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 new treatment line includes the following: preozonation, oagulationflocculation and settling in a sludge-blanket type settling tank (PULSATOR), rapid gravity sand filtration, ozonation, and granular activated carbon filtration.
Results from laboratory tests used for the design are presented: ozonation rate, advantages for the quality of the treated water, expected reagejit savings, etc. 相似文献
Introduction of new technological achievements and development in the field of flame retardancy (FR)
Review of the current state of science and technology in FR
Review of applications and markets for FR products
Presentation of recent developments in local and global standardization and in testing technology
Discussion of toxicity and environmental issues
Provision of a unique opportunity for newcomers to FR research technology and marketing to become acquainted with the FR field in all its aspects
Discussion of halogen-based and non-halogen-based flame retardant chemicals, syngergism, intumescence, FR mechanisms, modeling, flame parameters, inherently FR polymers, and polymer blends 相似文献
1. Surface irregularities caused by melt flow phenomena
2. Crystallization behavior
3. Melt drawing phenomena in certain types of polyethylene 相似文献
During summer, algae blooms may occur. The old plant (including prechlorination, coagulation, flocculation, settling and sand filtration) has been replaced with a treatment line including: remineralization, preozonation, flotation, ozonation and granular activated carbon. Nitrate removal will be considered in the future. The paper presents the results obtained in the plant, the optimization of the preozonation dose as well as comparison with laboratory tests. A special reference concerns algae removal. 相似文献
Twenty bacterial strains capable of aftergrowth were isolated starting from ozonized surface water, from water of subterranean origin, and from a mixture of these two types of water. Six typical strains were used to determine the importance of the temperature factor on aftergrowth in five types of waters of different characteristics.
Three criteria for the evaluation of aftergrowth are: the growth rate factor (r2), the growth yield (maximum number of germs/mL when growth stops), and the latency time (in hours). The results, in triplicate, obtained from growth curves then were submitted to an analysis of variance by two cross classifications.
It was established that aftergrowth is related to the classical Pseudomonas and Azobacter families, but also to the species of Bacillus, Corynebacter, Micrococcus, Vibrionaceae, and even Enterobacter. Furthermore, it has been proven that the temperature factor is most important in all aspects, as an increase in water temperature enhances all growth characteristics: shortening of the lag-phase; increase in growth-rate factor; and yield.
Under practical conditions, the significant growth delay is very important. With Pseudomonas putida, the lag-phase is on the order of three days at +7.5°C and 10 hours at +17°C. 相似文献
A commonly proposed method for controlling .VOC emissions is filtration of the off-gas through adsorption of the stripped organics in the off-gas by granular activated carbon. The high incremental cost of this alternative has produced an interest in alternative control technologies.
One alternative currently available is based on short wavelength ultraviolet (UV) radiation. This technique combines the effects of ozone generation, free radical formation and photolysis of the contaminants to effectively control the VOC emissions. This technique is known as Advanced Photo Oxidation (APO)R.
The cost for APO is $0.27/m3 for a 3.8 m3/hr contaminated water system. A system of this size is adequate for a groundwater decontamination project where a moderate length of time is available for restoration of the site. The cost of a conventional air stripping tower with Granular Activated Carbon (GAC) adsorption emissions control in this size range would be $0.40 to $0.45/m3 (J.M. Montgomery, 1986).
Additional testing will be required to fully develop design guidelines for different contaminants and larger systems. Another area for additional technical documentation is the application of this technique to the liquid phase oxidation of VOCs. 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
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 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
The control strategies investigated and compared are multiloop SISO, 2-way decoupling and l-way decoupling. The control variables are the standard ones, i.e. reflux flow and boilup.
In most of the cases INA has been found to be a useful tool for design of the loops and for comparison of the different control approaches. INA has also been found to be useful for simultaneous tuning of the decouplers and the feedback controllers.
For 2-way decoupling the criterion to minimize interaction at the critical frequency for each primary feedback loop has been found useful in most, but not all, cases. The scheme can be designed by pure gains in the decouplers and there is no reason to introduce dynamics into the decouplers—the systems studied are already sufficiently rich in dynamics.
INA has been found to be a suitable vehicle for the choice between the two possible l-way decoupling schemes.
With the design approach taken, l-way decoupling has been found to provide considerably better control quality than 2-way decoupling in two of the six systems, the differences in control quality being small in the other cases.
The effect of model mismatching on the results, caused e.g. by process nonlinearities, is discussed and simple rules to decrease the parameter sensitivity for 2-way decoupling schemes are given. When model mismatching is considered, the advantage of l-way decoupling over 2-way decoupling seems to increase.
One deficiency of the INA design as used in this paper is that it does not single out the design which is to be preferred on the grounds of robustness. 相似文献
There has been a high degree of proliferation of new products in the form of new polymers, new grades of existing polymers, as well as filled, reinforced, alloyed versions. While this does introduce new degrees of freedom in material selection, it is a source of significant confusion for the design engineers who have to cope with selecting the preferred material from among the many that are available. The choices and data bases are becoming confusing.
Various forms of relatively exotic, aromatic-monomer chemistry are being applied, but the emphasis appears to be on new amorphous polymers.
High-performance requirements exist in virtually all segments of the plastics field; the major end uses are in aerospace, automotive, business machines, electrical/electronics, food packaging, and medical applications.
Foreign presence has strongly increased as European companies have increased imports or have purchased established product lines or business units.
There will be continued pressure on the performance plastics from the lower priced materials which are countering with upgraded, modified, alloyed versions of their own. There is also increased competition between thermoplastics and thermosets as the result of material developments and process refinements. 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
At 100 psia (0.69 MPa) Xclean < Xcont
At 300 psia (2.1 MPa) Xclean?Xcont
At 500 psia (3.5 MPa) Xclean > Xcont
The effect of contamination on CHF was found to be a function of pressure, initial contaminant concentration, and the relative steam quality at which CHF conditions occur. These results are compared to data available in the open literature where Xclean is always greater than Xcont. A method for correlating these data is also illustrated. 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
First of all, an obvious fact must be remembered. Each installation is a special case. It is therefore out of the question to present general results with direct across-the-board applications. On the other hand, it is possible to engineer a general methodology for price calculation and apply it to a few specific examples. As operator of a large number of these facilities, Compagnie Générale des Eaux can present economic results in many, widely different technological economic conditions.
Generally speaking, it can be said that the cost of ozonation is increasingly optimized. This technique, considered a few years ago as a luxury, is now technically and economically ready for incorporation on an equal footing in most treatment trains. 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