Ozone application

Ozone applications in the United States for drinking water are far fewer than in Europe. However, the potential market is large, if environmental or health needs ever conclude that an alternate disinfectant to chlorine should be required. Although energy costs of ozonation are higher than those for chlorination, they may be comparable to combined costs of chlorination dechlorination-reaeration, which is a more equivalent technique. One of ozone s greatest potential uses is for municipal wastewater disinfection. 

Favorable operational economics and good management practices require high levels of control of the ozonation system. Depending on the specific process of ozone applications, plant size, and design philosophy, the control system may be simple or complex. The trend in Europe is toward highly sophisticated and centralized control. 

Mock, B. Hamouda, H. Ozone application to color destruction of industrial wastewater - Part I Experimental. Am. Dyest. Rep. 1998, 87, 18-22. 

Being poised on the edge of the third millennium in Berlin, the city of Siemens who constructed the first ozone generator almost 150 years ago, and writing a book on ozone applications in water can make one philosophical. Especially when one has been confronted with the puzzlement of most acquaintances about why anyone deliberately produces ozone and what it has to do with water. These two aspects of this book ozone and water need some clarification. 

Removal of NOM or its alteration to products less reactive to chlorine is a priority task in modem water treatment, comprising chemical oxidation by ozone, biodegradation, adsorption, enhanced coagulation or even membrane technologies. A DOC-level of approximately 1 mg L 1 appears to be the lower limit of ozone applications, but a few cases exist, where waters with lower concentrations of NOM (ground water) have been treated. 

For the experimenter in the laboratory, not only do materials have to be chosen on the basis of their corrosion-resistance, but also for their effect on ozone decay. Some metals (e. g. silver) or metal seals enhance ozone decay considerably. This can be especially detrimental in drinking water and high purity water (semiconductor) ozone applications, causing contamination of the water as well as additional ozone consumption. Moreover, the latter will cause trouble with a precise balance on the ozone consumption, especially in experiments on micropollutant removal during drinking water ozonation. With view to system cleanliness in laboratory experiments, use of PVC is only advisable in waste water treatment, whereas quartz glass is very appropriate for most laboratory purposes. 

The fact that dissolved ozone is produced brings a very important advantage to subsequent ozone applications mass transfer from the gas to liquid phase is not required. Efficient mixing (e. g. with static mixers) of the ozone-rich pure water stream with the (waste-)water stream to be treated, though, is required. During this in-situ ozone production, the liquid ozone concentration (cL) can easily reach the solubility level (cr ), depending on the pressure (P) and temperature (T) in the cell. Oversaturation of the feed-water will immediately occur, when the pressure drops. Due to this potential degassing, vent ozone gas destruction is also required for this system. 

The influence of surfactants is predominantly of importance in waste water ozonation studies where often comparatively high concentrations of such compounds occur. However, similar effects can occur in drinking or ground water ozonation applications. This was shown for the decomposition of the organic phosphate pesticide diazinon (phosphorotoic acid <5,<5-diethyl-o[6-methylethyl)-4-pyrimidinylJether) in aqueous solution by ozonation. This compound was found to considerably affect the surface tension of the aqueous solution, even at low concentrations (c(M) < 10 mg L l) and, thus, also influenced the oxidation mechanism (Ku et al., 1998). 

The previous chapters in Part B have dealt with the basics of the ozonation process. As seen in the discussion of full-scale ozonation applications (Chapter A 3), ozone is rarely used alone. The combination of ozone with other water treatment processes can often greatly increase effectiveness and cost efficiency of ozonation, or the addition of ozonation to an existing production process can increase efficiency in achieving production goals. Process combinations make sense that utilize ozone s effectiveness in ... 

An example where all four areas are utilized in combination with production processes is found in ozone applications in the semiconductor industry (Section B 6.1). Part of ozone s effectiveness in these four areas is derived from its production of OH-radicals. Combined processes, i. e. advanced oxidation processes, represent alternative techniques for catalyzing the production of these radicals and expands the range of compounds treatable with ozone (Section B 6.2). 

Ozone is applied in three-phase systems where a selective ozone reaction, oxidation of residual compounds and/or enhancement of biodegradability is required. It can be used to treat drinking water and waste water, as well as gaseous or solid wastes. Especially in drinking water treatment full-scale applications are common, e. g. for particle removal and disinfection, while in waste water treatment sludge ozonation and the use of catalyst in AOP have been applied occasionally. Current research areas for three-phase ozonation include soil treatment and oxidative regeneration of adsorbers. Ozonation in water-solvent systems is seldom studied on the lab-scale and seems favorable only in special cases. In general, potential still exists for new developments and improvements in ozone applications for gas/watcr/solvent and gas/waler/solid systems. 

The principles and goals of ozone application in both types of three-phase systems are discussed in Section B 6.3.1. Since mass transfer may decisively influence the oxidation outcome in these complex systems, their additional resistances and effects on mass transfer is also discussed in detail in this section. In doing so, the gas/water/solvent system is used as an example for both types of system, leaving the reader to adapt the principles to the gas/ waler/solid systems by him- or herself. Examples of ozone application in both types of three-phase systems are then presented (Section B 6.3.2), with emphasis on their goals, as well us technical advantages and disadvantages, while Section B 6.3.3 provides useful advise for experimentation with three-phase systems. 

Ozone applications in gas/water/solid systems cover a wide range of media such as sludges, soils, adsorbents and catalysts. Disinfection, which can be regarded as a three-phase system, is a well-described and established application (see Section A 3.2.1 and 3.3.2). The preozonation for particle removal is discussed frequently, especially in the treatment of surface water, where different organic (e. g. bacteria, viruses, algae, suspended organic matter) and inorganic (e. g. silica, aluminum and iron oxides, clay) particles can be present (see Section A 3.2.4). 

While in lab experiments or on-site the pH can be controlled, in an in situ application it will always decrease due to the formation of organic acids. This will effect shifts in the oxidation mechanism toward the direct oxidation pathway and in the chemical equilibrium of the soil. Furthermore, both ozone applications will result in changes in the soil chemical constituents, i. e. the cation exchange layer and the humic fraction. The consequences of these changes are still mostly unknown. A special lag-phase and a selection of bacteria in regrowth might be caused by the ozonation. 

When aqueous solutions are treated with ozone for several hours, there is significant sample evaporation the rate of this process depends on the initial sample volume and the average temperature of the sample during the period of ozonolysis. The time required for ozone application is considerably longer than that needed with other AOPs, such as UV irradiation. 

Ozonation—Application of ozone for disinfection and other purposes. 

In most of the data reported here, the rate of ozone application was 20 to 25 mg. per minute. 

Amount of ozone application is controlled by the number of generators placed in operation. The amount of ozone being generated is determined from the cubic feet per minute passing through the plant and an iodometric titration of 1 cu. foot of the ozonated air passing to the contact tanks. 

Each of the two ozonation application systems was constructed of concrete and designed to treat 26 cubic meters (6600 gallons) of water per hour. They were served alternately by the single ozone-generating plant which ran continuously day and night for nearly 8 months beginning October 1951, to the complete satisfaction of the Berne Water Bureau as well as ourselves. 

Full-scale ozone applications of textile wastewater treatment have been installed in Japan, the United Kingdom, Italy, Germany, etc. " ... 

EfTectiveness of ozone application in removing established biofilms... 

Polyurethane elastomers have high strength extremely good abrasion resistance good resistance to gas, greases, oils, and hydrocarbons and excellent resistance to oxygen and ozone. Applications include solid tires, shoe soles, gaskets, and impellers. 

Ozone Ozone is a colorless gas that is extremely unstable and is a strong oxidizing agent that is capable or reacting with a wide variety of organic and inorganic solutes in water. Effectiveness of ozone disinfection is a function of the pH, temperature of water and method for ozone application. 

Corona or atmospheric plasma treatments are often combined with ozone application in coating extrusion and lamination. Let us consider, for instance, the coating... 

In spite of a common use of ozone application together with various surface modification techniques, such as corona and atmospheric plasma, the influence of the combined action on the most popular plastics has not been quantified by exhaustive experimental data. Such a discussion regarding to the use of ozone with corona or of ozone with atmospheric plasma on heat seal strength will follow. 

Besides these factors, several ozone related parameters were identified that could affect adhesion and heat seal strength. These parameters were ozone flow rate, ozone concentration (power setting on ozone unit), and geometry of the ozone applicator set-up, such as horizontal distance and angle from horizontal. The levels used in this design are found in Table 5.1, accomplished by a combination of oxidation of the extrudate and treatment of the substrate. 

There Is an important point to be made regarding the positioning of ozone application near the extrudate surface. Firstly, ozone gas is delivered to the production process using an applicator tube that is configured to suit the extrusion coating machine. The tube is usually deckled to the extrudate width to maximize ozone delivery. Applicator tubes are typically manufactured from stainless steel of various diameters, but consistently with 1 mm holes drilled and aligned approximately 10 mm apart. The applicator is usually positioned within 30-40 mm of the melt... 

---