Water ozonization

Ozone is used extensively in Europe to purify water. Ozone, a moleeule eomposed of 3 atoms of oxygen rather than two, is formed by exposing air or oxygen to a high voltage eleetrie are. Ozone is mueh more effective as a disinfectant than... 

Packed-bed contactors, which include concurrent or countercurrent water/ozone-rich gas flow. 

Three triatomic molecules, water, ozone, and carbon dioxide, provide particularly strong experimental evidence to support the VSEPR ... 

Brewing water, ozonation of, 17 807-808 Brewster angle, 14 670 Brewster s law, 14 857 Brewster windows, 14 682, 687 Brezinaite, 6 471t... 

Photolytic. Based on data for structurally similar compounds, acenaphthylene may undergo photolysis to yield quinones (U.S. EPA, 1985). In a toluene solution, irradiation of acenaphthylene at various temperatures and concentrations all resulted in the formation of dimers. In water, ozonation products included 1,8-naphthalene dialdehyde, 1,8-naphthalene anhydride, 1,2-epoxyacenaphthylene, and 1-naphthoic acid. In methanol, ozonation products included 1,8-naphthalene dialdehyde, 1,8-naphthalene anhydride, methyl 8-formyl-1-naphthoate, and dimethoxyacetal 1,8-naphthalene dialdehyde (Chen et al., 1979). Acenaphthylene reacts with photochemically produced OH radicals and ozone in the atmosphere. The rate constants and corresponding half-life for the vapor-phase reaction of acenaphthylene with OH radicals (500,000/cm ) at 25 °C are 8.44 x lO " cmVmolecule-sec and 5 h, respectively. The rate constants and corresponding half-life for the vapor-phase reaction of acenaphthylene with ozone at 25 °C are... 

Richardson SD, Caughran TV, Poiger T, Guo Y, Gene Crumley F (2000) Application of DNPH derivatization with LC/MS to the identification of polar carbonyl disinfection byproducts in drinking water. Ozone Sci Engin 22(6) 653-675... 

Gates D. 1999b. Practieal suggestions for meeting USEPA compliance monitoring requirements and in-plant operational control of chlorine dioxide in drinking water. Ozone Sei Eng 21 433-445. 

Ozone has many industrial applications. It is a sterilizing and deodorizing agent. It is used for disinfection of filtered drinking water and to purify waste-waters. It also is used in water treatment plants for removal of metal impurities by oxidizing them into insoluble compounds. This removes undesired taste, odor, and color from the water. Ozone also is used for odor control. 

Multiple-stage ozonization seems to be more effective than single-stage ozonization, both followed by biodegradation, for DOC ehmination in treatment of reservoir waters and secondary effluents of a domestic wastewater treatment plant . The fate of O3 in water ozonization consists of a fast reaction with the DOC and a slow first-order decay of unreacted O3. A method for optimization of a two-stage water ozonization process is based on control with a FIA unit, where the ozone concentration is continuously measured by oxidation of indigotrisulfonate(8) . The various fractions of DOC (in the ppm range) may react with the traces of bromide (sub-ppm) found in natural waters, as this anion... 

DPA (diphenylanthracene), 1219, 1223, 1226 Drinking water, ozone disinfection, 606, 673, 740 Dmgs... 

Rubber is chemically resistant to most corrosive liquids, gases, salt water, ozone and UV light. These corrosive agents are commonly... 

Kool H J, Hrubee J (1986) The influence of an ozone, chlorine and chlorine dioxide treatment on mutagenic activity in (drinking) water, Ozone Science Engineering, 8 217-234. 

Prados M, Paillard H, Roche P (1995) Hydroxyl Radical Oxidation Processes for the Removal ofTriazine from Natural Water, Ozone Science Engineering 17 183-194. 

Full-scale waste water ozone treatment facilities may roughly be defined as systems with a ozone generation capacity of more than 0.5 kg per hour. They can be found in various applications in all branches of industry, treating almost all types of waste waters. The operating conditions used in waste water ozonation are dependent on the type of industry and the kind of waste water. They can be grouped according to ... 

The discussion of full-scale ozonation systems for waste waters in the following sections is grouped according to the main removal goal of the application, analogous to that used in drinking water ozonation systems. 

The most frequently used contactors in full-scale waste water ozonation systems are bubble column reactors equipped with diffusers or venturi injectors, mostly operated in a reactor-in-series counter-current continuous mode. Many full-scale ozone reactors are operated at elevated pressure (2-6 barabs) in order to achieve a high ozone mass transfer rate, which in turn increases the process efficiency. 

The most frequent operational problems in waste water ozonation systems are foaming and the formation and precipitation of calcium oxalate, calcium carbonates and ferrous hydroxide (Fe(OH)3) which may easily clog the reactor, piping and valves and also damage the pumps. 

Goals, technology and results of full-scale applications on some types of waste waters are discussed in more detail in the following sections. An overview of technological features, operating parameters and treatment costs of full-scale plants for waste water ozonation is given in Table 3-3. 

Table 3-3 Overview of technological features, operating parameters and treatment costs of full-scale plants for waste water ozonation. 

Reactor Water Ozonation (Input)11 Amount of Ozone Used Pollutant Removal11... 

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 type of feed gas used, air or oxygen, determines the achievable ozone gas concentration and the gas preparation requirements. The higher the oxygen content, the higher the ozone concentration possible. Ambient air contains 02 in about 21 vol % (at STP) and is thus a cheap and ubiquitous resource for ozone production. Its main use and advantage is in applications where large mass flows are required at comparatively low ozone gas concentrations, e. g. in drinking water ozonation systems. 

Water or waste water ozonation - regardless of the scale of equipment - is mostly performed in directly gassed systems, where the ozone containing gas is produced by an electrical discharge ozone generator and is introduced into the reactor by some type of gas diffuser. Since two phases, the gas and the liquid, are required for the oxidation reaction to proceed as it does, they are also called heterogeneous systems. 

In waste water ozonation experiments with high concentrations of (highly reactive) contaminants it is recommended that the ratio of QG to VL not be too low, i. e. the liquid volume not be too large (VL= 1-5 L) and an appropriate ozone generator be used. This is important because of the high reaction rates which may be achieved and which may cause a total depletion of ozone in the off-gas, causing problems in balancing the ozone consumption in the systems. 

It is very important to apply the same oxidation conditions in each batch, and vary only one parameter at a time, unless statistical experimental design is being applied. Be especially careful to assure constant liquid ozone concentration cL as well as constant pH. Both are often observed to vary within the reaction time in waste water ozonation. The liquid ozone concentration shows an increase whereas the pH normally decreases due to the formation... 

Where necessary and applicable, the specific ozone dose or the specific ozone absorption (best recorded and computed on-line) is recommended as the measure for analyzing process performance. Since in waste water ozonation, the ozone off-gas concentration often increases during the batch-treatment, the specific ozone absorption will not vary linearly with the treatment time. 

In the presence of ozone in water, ozone diffuses through the membrane into the reaction chamber. The rate of flow is dependent on the partial pressure of ozone. In order to avoid a depletion of ozone molecules at the surface of the membrane, the electrode should be immersed into a continuous flow. 

---