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- - -.. -.- - - - - - _. . - ,.' .. '....... ',' .. '. ....."];it:io;,.' ::cc..:_. 6:::ZT Division: Air Pollution Control Division James H. Lents. Director The primary pollutants of concern have been those terllted crItters pQllutants (referring to tbe Air Quality Criteria docwaeuts used to establish National Ambient Air Quality Standards (NAAQS) for each of thea>: particulate matter, sulfur oxides, volatile organic compounds (VOC, also. called hydrocarbons, which do not have an NAAQS, but which do contribute to exceedances of the ozone NAAQS), nitrogen ondes, carbon monoxide, and - most recently - lead. Table III-l summarizes the emissions sod overall levels of control statewide for these froll the "tradltlonar' sources of air pollution; em15s10ns from residential home heating (including fireplaces and wood stoves); temporary activities such 8S land clearing. and other fugitive emission sources are also significant and ar~ summarized in Table 2. Since there are only three major stationary sources of lead in Colorado and a total of 2.642 tons per year of controlled lead emissions frOll stationary sources, this report will concentrate on the opther criteria pollutants. In addition to the criteria pollutants I emissions of hazardous pollutants and certain "non-criteria" pollutants from specific sources are limited by regulation. Recently, concern over toxic pollutants, as well as such pollutant effects as acid deposition and reduced vi8ibllity~ has increased. Both toxic and hazardous pollutants are considet:ed harmful to health in certain concentrations; the difference is that the health effects of hazardous pollutants are considered irreversible; toxic pollutant effects are generally reversible. Air quality management. the term used to describe efforts to mitigate both mobile and stationary source air pollution, uses the fOllOwing basic strategies: 1. Establish emission limits for new sources that minimize these emissions and, In addition, review the impact these sources will have on ambient air quality to ensure that impact is not significant (in areaa which do not exceed the appropriate NAAQS) or does not interfere with reasonable further progress (in areas which exceed the applicable NAAQS). 2. In nonattainment areas (those which exceed an NAAQS), establish an attainment plan which may include more stringent emission 11a1ts for both new and existing sources, requirements that increases in emissions be offset by decreases in existing emissions, and other measures designed to reduce emissions to levels at which the NAAQS exceedances no longer occur. 3. prevent, through emission limits. dispersIon. source location and other measures, concentrations of pollutants in the ambient air which could affect public health or welfare, 'Ibis includes odorous, as well as ,the IDOre harmful toxic and hazardous, pollutants. Particulate matter (which generally refers to liquid droplets as well as solid pollutants), including lead, is usually controlled beat with fabric filters, although many other control devices are usede Of the two most common alternatives. electrostatic precipitators can be a8 efficient. but may be more expensive, while scrubbers are less efficient, more energy intensive, and, due to the wet nature of these control devices 8S opposed to the dry collecting conditions in fabric filters and electrostatic: precipitators, aore subject to corrosion and other maintenance problems. nle other pollutants are gases and, unlike partic.ulate matter, can not be captured physically; absorption, che.ieal reaction. or prevention of formation of the pollutant is required. This is much more difficult, as Table 1 indicates. Control technologies have evolved over the years. Scrubbers, for eIample, were considered a desirable control system for power plants up until the 1980's because both particulate matter and S02 emissions were reduced. Hainte-nance _pr~blem~ as well as the high energy requir~~t8 I,lD.d lover efficiencies. however, have decreased the popularity of scrubbers; electrostatic precipitators were the choice for particulAte aa-ti:er control, but the lower sulfur content of many western coals decreases precipitator efficiency. Fabric filters are an excellent alterDa~ive. but until recently. high power plant exhaust gas teaperatures prohibited fa.brlc filter use. The trend now is toward fabric -filters, which have -31-