Air Pollution Technology and Medical Waste
Pollution prevention is the most preferred option for emission reduction because it can become an integral part of a facility’s process. Pollution prevention is best when accomplished with process control methods or process changes that eliminate or reduce emissions. An example of this is the use of low sulfur fuels in combustion devices. Diesel fuel could contain as much as 5,000 ppm of sulfur before the EPA began regulating sulfur content in 1993. The current 15 ppm standard was established in 2006. Low-sulfur fuels protect workers from toxic hydrogen sulfide emissions and reduces the amount of SO2 produced during combustion.
Process designers can choose equipment that inherently has lower emissions and/or propose equipment monitoring that, when implemented, would minimize emissions. An example of equipment with lower emissions is a floating roof inside a tank. A floating roof significantly limits the evaporation of liquid into the vapor space within the tank, lowering the quantity of vapors that can escape from tank vents. An example of equipment monitoring is the regular monitoring of fugitive components. No matter how well a company maintains their equipment, there will be leaks from components like valves, flanges, pumps, etc. These are called fugitive emissions. To identify these leaks, many companies monitor each component with a hand-held VOC analyzer.
Emissions from facilities are often routed to add-on abatement, such as flares, thermal oxidizers, scrubbers, and carbon adsorption systems. Some can reduce emissions by more than 99.9%. However, add-on abatement equipment may pose other concerns, such as the generation of additional emissions or the
transfer of air contaminants to water or some other medium.
Pollutants
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Sulfur dioxide - produced in combustion
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Carbon monoxide - produced in inefficient combustion
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Aldehydes - produced in decomposition of animal bodies (fats, oils)
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Nitrogen oxides - produced in combustion
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Phosgene - produced in decomposition of chlorinated hydrocarbons
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Suspended particulates - many types of operations produce solid and/or liquid particles that become suspended in air and are referred to as “particulates”. They range up to 1 millimeter in diameter.
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Odor - produced by many sources
Methods of Dealing with Air Pollutants
Baghouses
Upsides
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Low pressure drop and energy use
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Easy maintenance
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No added chemicals or heat required
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Flexible operation with some bags off line while others are on line
Downsides
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May not remove smallest particulates
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Cannot handle hot gas
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Bags liable to tearing
Electrostatic precipitators
Upsides
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Can be extremely efficient, especially is processing a steady waste stream
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Can remove very small particulates
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Low pressure drop through unit
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Can operate at high pressure and/or high temperature
Downsides
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High cost - capital cost
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Ozone produced in operation
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Removes particulate but not dissolved gases
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High voltages can be hazards for personnel
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Big floorplan
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Cannot handle input streams that vary in composition and flowrate without loss of efficiency
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Unsuitable for some waste streams (e.g. contain combustibles)
Condensers
Upsides
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Can recover condensed material that might be useful
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No need to add material to waste stream
Downsides
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Hard to get pollutants down to very low levels just by condensing
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Coolant system cost (capital and operating) and complexity
Combustion
Upsides
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Simple, can destroy a lot of chemical compounds
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Really efficient destruction of organic contaminants if operated correctly
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Generation of heat which can be useful.
Downsides
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High operating costs - fuel, personnel
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Hazards of playing with fire
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Potential for incomplete combustion and production of carbon monoxide and other hazardous chemicals such as dioxins
See also air pollution control for medical waste incinerators.
