Quality criteria

The purity of a gas corresponds to the content of the main molecule and is given in percent, usually with reference to the mole fraction. Another indication of purity, the dot notation [9.4] has also gained acceptance, as already described in Section 2.2.5.5. The dot notation serves the clear indication of the minimum content of a gas by means of two digits separated by a dot. 

Apart from the dot notation, there are also terms that point to particularly low impurities or to an application. 

Essential additional criteria are defined by listing components (specifications) with limiting concentrations that must not be exceeded. Owing to the low proportions, the following smaller units have gained acceptance. 

a number of large-scale units for the generation of gases can achieve the purities (6.0 and higher) required for specialty gases. These plants are described, inter alia, in the Sections 2.2.5.5, 3.3.2, 3.4.2,4.2, 5.2.4 and 6.2.4. The generation of aU other gases occurs in complex chemical processes in which split streams are branched off for further utilization. 

The product quality achieved in large-scale plants not always is sufficient for the different applications of specialty gases. This means the products have to be subsequently purified. The multitude of pure gases and the descriptions of the related individual purification-processes would go beyond the scope of this chapter. Therefore, Table 9.1 shows only examples of processes, pure gases and impurities to be removed [9.5]. 

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It is useful to specify at the start the principal quality criteria for each type of product (motor fuels, heating fuels), imposed by the requirements for the different kinds of energy converters motors, turbines, burners. 

We will examine here other quality criteria having less impact yet still being important. 

Air Quality Criteria for Oxone and Other Photochemical Oxidants, PubUcation No. EPA-600-8-84-020F, 5 vols., U.S. Environmental Protection Agency, Research Triangle Park, N.C., 1986. EPA pubUshes separate criteria documents for aU the criteria poUutants and they are updated about every five years. 

For an excellent, comprehensive review of the chemistry, environmental, and anthropogenic release, environmental fate, and environmental and human health effects of lead, see Air Quality Criteria for Eead, Vol. I—IV, EPA-600/8-83/028a-dF, U.S. Environmental Protection Agency, Washington, D.C., June 1986, -Msd Air Quality Criteria for Eead Supplement to the 1986 Addendum, EPA-600/8-89/049F, U.S. Environmental Protection Agency, Washington, D.C., Aug. 1990. 

Ambient Water Quality Criteria forMercury—19S4, EPA-440/5-84-026 (NTIS No. PB85-227452), U.S. Environmental Protection Agency, Washington, D.C., 1985. 

Air Quality Criteria forTead Supplement to the 1986 Addendum, U.S. EPA, Environmental Criteria and Assessment Office, Washington, D.C., 1990. Technical Support Document to Proposed Airborne Toxic Control Measure for Emissions of Toxic Metalsfrom Non-Ferrous Metal Melting, State of California Air Resources Board, Stationary Source Division, Sacramento, Calif., 1992. 

Table 3. Coastal Water Quality Criteria for Toxic Substances Other Than Biocides ...

Table 10. Quality Criteria for White Sugar, According to EC Sugar Market Regulations ...

Air Quality Criteria for Sulfur Oxides, National Air Pollution Control Administration, U.S. Dept, of Health, Education, and Welfare, Washington, D.C.,Jan. 1969, pp. 89-102. 

In many cases, the quality of a stream or another water source can be adequately improved by removing more BOD or suspended solids. In other iastances, the effluent is prepared for groundwater recharge which may require only the removal of nutrient. A classification of wastewater treatment processes is given ia Table 3. Table 4 summarizes water quality criteria for various iadustrial uses (10). 

Quality Criteria for Water Environmental Protection Agency, Washington, D.C., 1976. 

I. Air Quality Criteria for Photochemical Oxidants National Air PoUution Administration Pub. No. AP-63, U.S. Government Printing Office,... 

Ambient Water Quality Criteria for Chromium, EPA 440/5-80-35, United States Environmental Protection Agency (EPA), 1980 Fed. Reg. (FR), cited as Volume FR Number 56 FR3526 56 FR 30266. 

Despite EPA s urging and guidance, state response was disappointing. A few states adopted large numbers of numeric toxic pohutant criteria, primarily for the protection of aquatic life. Most other states adopted few or no water-quality criteria for priority toxic pohutants. Some rehed on free from toxicity criteria and so-called acLion levels for toxic pollutants or occasionally calculated site-specific criteria. Few states addressed the protection of human health by adopting numeric human health criteria. 

Purchasing may be critical to quality, cost efficiency and safety of the service provided. Therefore evidence should be given that there is a written management policy or directive establishing quality criteria. 

An additional role of the model evaluation methods is to help in the actual modeling procedure. In principle, an improvement in the accuracy of a model is possible by incorporating the quality criteria into a scoring function being optimized to derive the model in the first place. 

Discuss the relative importance of air quality criteria and cost effectiveness in the setting of air quality standards. 

U.S. Environmental Protection Agency, "Air Quality Criteria for Lead," EPA 600/8-S.3-018F. Research Triangle Park, NC, June 1986. 

Air quality criteria are cause-effect relationships, observed experimentally, epidemiologically, or in the field, of exposure fo various ambient levels of specific pollutants. The relationships between adverse responses to air pollution and the air quality levels at which they occur have been discussed in Chapter 4 and illustrated in Table 4-5 and Fig. 4-10. 

For any pollutant, air quality criteria may refer to different types of effects. For example. Tables 22-1 through 22-6 list effects on humans, animals, vegetation, materials, and the atmosphere caused by various exposures to sulfur dioxide, particulate matter, nitrogen dioxide, carbon monoxide, ozone, and lead. These data are from fhe Air Quality Criteria for these pollutants published by the U.S. Environmental Protection Agency. 

Criteria stipulate conditions of exposure and may refer to sensitive population groups or to the joint effects of several pollutants. Air quality criteria are descriptive. They describe effects that can be expected to occur wherever the ambient air level of a pollutant reaches or exceeds a specific concentration for a particular time period. Criteria will change as new information becomes available. 

Sources Air Quality Criteria for Particulate Matter and Sulfur Oxides, final draft, U.S. Environmental Protection Agency, Research Triangle Park, NC, December 1981 Review of the National Ambient Air Quality Standards for Sulfur Oxides Assessment of Scientific and Technical Information, Draft OAQPS Staff Paper, U.S. Environmental Protection Agency, Research Triangle Park, NC, April 1982. 

Air quality standards prescribe pollutant levels that cannot legally be exceeded during a specific time period in a specific geographic area. Air quality standards are based on air quality criteria, with added safety factors as desired. 

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