Ozone based

According to the number of AOPs investigations directed to the treatment of eolored wastewater, the most studied processes are Fenton type proeesses, then UV-based technologies, ozone-based technologies, etc. This part of chapter contains the more detailed review of AOPs applied for the treatment of eolored wastewater investigated in our laboratory, and the less detailed overview of other AOPs. 

Kusic, H Koprivanac, N Loncaric Bozic, A. Minimization of organic pollutant content in aqueous solution by means of AOPs UV- and ozone-based technologies. Chemical Engineering Journal, 2006 in press... 

The detection of new kinds of microorganisms, such as the cysts and oocysts of parasites (Giardia, Cryptosporidium), the identification of more and more chemical pollutants in waters and increasing quality levels required for drinking and waste waters has induced new interest in ozonation and ozone-based advanced oxidation processes. However, care has to be taken in the application of ozonation, since recent research has indicated that presumably hazardous by-products can be formed, e. g. bromate in the ozonation of waters containing bromide. 

The absorption maximum of ozone occurs at 254 nm, which is close to the wavelength of the mercury resonance line at 253.7 nm. The decrease of the UV intensity at X = 254 nm is proportional to the concentration of ozone based on the Lambert-Beer s law of absorption ... 

How effective are proposed control or management strategies This question could pertain to the confidence with which a standard will be met. For example, Hanna et al. (2001) assess the uncertainty associated with estimates of predicted ambient ozone levels subject to a particular emission scenario, and Abdel-Aziz Frey (2004) evaluate the probability of non-compliance with United States National Ambient Air Quality Standards for ozone based upon uncertainty in emission inventories that are propagated through an air quality model. A probability distribution of estimated exposures can be compared with a point estimate of an exposure benchmark in order to determine the probability that the benchmark will be exceeded and, if so, by how much. 

Ivandini, T.A., Rao, T.N., Fujishima, A. and Einaga, Y. (2006) Electrochemical oxidation of oxalic acid at highly boron-doped diamond electrodes. Anal. Chem. 78, 3467-3471 Josephy, P. D. (1996) Molecular Toxicology, Oxford University Press, New York, NY Kraft, A., Stadelmann, M. and Blaschke, M. (2003) Anodic oxidation with doped diamond electrodes A new advanced oxidation process. J. Hazard. Mater. 103, 247-261 Kusic, H., Koprivanac, N. and Bozic, A.L. (2006) Minimization of organic pollutant content in aqueous solution by means of AOPs UV- and ozone-based technologies. Chem. Eng. J. 123, 127-137... 

Although AOPs make use of different reacting systems, they are almost all characterized by the efficient production of hydroxyl radicals ( OH). A short critical review of recent developments and the state of the art of hydrogen peroxide and/or ozone based AOPs with reference to research and industrial applications has been presented by Andreozzi et al. (1999). 

The development of a unique method (12), originally described by Strong (55) in 1941, whereby it is possible to determine the mean height of the ozone layer through measurements of the pressure-sensitive infrared absorption of the ozone molecule and comparison with determinations of the total amount of ozone based upon ultraviolet spectroscopic measurements has given added impetus to routine ozone vertical distribution determinations. This method permits the evaluation of the approximate vertical distribution of the ozone solely from the use of surface observations. Preliminary results (12) indicate that there is no simple relation between the vertical distribution of ozone and the total amount present in the atmosphere at any given time. When routine measurements are established over a network of... 

Treatment of Lamffill Leachates. Landfill leachate contains large quantities of nonbiodegradable and toxic constituents. Some heterogenous catalytic ozonation processes (Ecoclear or Catazone systems) can successfully treat landfill leachates. " In addition, ozone-based AOPs have also been successfully used to remove COD or TOC either as pretreatment or at the final stage of the treatment. Both heterogenous catalytic ozonation and the AOP processes are introduced below. 

Ozone-based AOPs are being used increasingly to treat landfill leachates. " They are also used for ground-water treatment to destroy trichloroethylene (TCE), tetrachloroethylene, and pentachlorophenol. In addition, they are used for groundwater remediation at Superfund sites in the United States to destroy volatile organic compounds and benzidines. Another application of ozone-based AOPs involves their use at U.S. ammunition plants to destroy explosives. ... 

In various studies concerning ozonation and ozone-based AOP the formation of bromate is observed [31,62,66-68]. The extent of bromate formation is dependent on the ozone exposure. Higher ozone doses usually result in higher bromate concentrations. However, if the ozone demand of the water itself is high, the ozone exposure for bromide is smaller and less bromate is formed [31,62,66]. During experiments with the combined process... 

There are many applications for conductimetric measurements, some of which are very specific. For example, in a medical application, a conductivity sensor has been used to determine levels of ammonia in human breath In the same article, the authors also demonstrated a second sensor for breath analysis of carbon dioxide. In environmental analysis, a samarium iron oxide (SmFeOs) gas sensor has been developed for the detection of ozone based on conductance at sub-ppm levels ". ... 

An attractive alternative for selective detection is sulfur chemiluminescence (SCD). In 1989 Benner and Stedman described a new ozone-based SCD. Owing to its high sensitivity, the great advantage of linear response vs. concentration of sulfur species, its wide linear dynamic range, high... 

Ozone is one of the most powerful oxidant agents available. It is used widely for drinking water disinfection and for the oxidation of pollutants in industrial wastewaters. Ozone is unstable in water and decomposes into radicals such as HO, which are the strongest oxidants in water. To enhance the decomposition of ozone and consequently the efficiency of ozone-based oxidation processes, the combination of ozone with homogeneous or heterogeneous catalysts, with or without metallic phases, has been investigated and recently reviewed [164]. Activated carbon has been mentioned as one of the most attractive alternative catalysts for this process. 

OxyTech (UK) Ltd. is currently selling ozonators based on this technology using 20 cm long, 2.5 cm diameter tubular glassy carbon anodes. The cathodic reaction for this system is the reduction of oxygen by using an air cathode. 

Infrared spectrophotometry of ozone based on the principal absorption band near 9.5 pm is relatively free from interference by the bands of other atmospheric constituents. However, a long optical path is necessary for detection of atmospheric ozone. A White cell (multiple reflection cell, 10-1000 m path) combined with a Fourier-transform infrared (FTIR) spectrometer (spectral resolution of lcm or better) with a HgCdTe detector is often used in multi-component air-monitoring and smog chamber experiments. 

The distribution of atmospheric ozone based on data obtained by the Nimbus 4 BUV satellite is shown in Fig. 2. Ozone is most abundant in the tropical middle stratosphere ( 30 km), where the solar zenith angle is small and the atmospheric density is sufficiently large to produce O3 efficiently via reactions (1) and (2). The decrease in ozone toward the poles is due to a decrease in production due to the steeper solar zenith angles at high latitudes. The important solar absorption bands for ozone and oxygen are listed in Table I. Figure 3 shows the altitudes where the stratosphere and mesosphere are heated by these absorption bands. The peak in the heating is nearly coincident with the stratopause temperature maximum shown in Fig. 1. 

---