In 1981, EPA promulgated the first set of technical regulations that governed the incineration of hazardous waste. This rule was fairly simple. It required hazardous waste incinerators to destroy at least 99.99 percent of the organic constituents of the hazardous waste, keep particulate matter emissions below 180 mg/dry standard cubic meter (dscm), and limit chlorine emissions to less than 1.8 kg/hr or 99 percent removal (whichever is higher). In 1984, Congress passed amendments to the Resource Conservation and Recovery Act giving EPA the authority to include such restrictions as necessary in permits to protect human health and the environment--the so-called "omnibus" authority. Because EPA had this "omnibus" authority, they controlled hazardous waste incinerator emissions primarily through individual permits rather than through the development of new regulations. As a result, permit conditions vary significantly from one jurisdiction to another.
In 1991, EPA developed new regulations governing the burning of hazardous waste in boilers and industrial furnaces. These rules contained limits on carbon monoxide (100 ppm), particulate matter (180 mg/dscm), feed rate limits for certain metals, feed rate limits for chlorine, and in certain instances, risk based limits on dioxins and furans. Most of these limits have been incorporated into hazardous waste incinerator permits using the "omnibus" authority.
In 1996, EPA's Office of Solid Waste began developing revised air emission regulations for hazardous waste incinerators and certain industrial furnaces. These revised standards will be based on the Maximum Achievable Control Technology methodology contained in the 1990 amendments to the Clean Air Act. This law requires EPA to survey each industry to determine what technology will result in the best available control of air emissions. Congress gave EPA specific instructions to set new emission standards on a pollutant-by-pollutant basis at the average of the best 12 percent of existing sources for that pollutant. EPA is expected to finalize these regulations in early 1999.
Maximum Achievable Control Technology requirements
Although the revised air emission standards for hazardous waste incinerators will not be final until 1999.
With the exception of particulate matter and carbon monoxide, it is difficult to compare the old and revised standards directly. Revised emission standards are based on concentration in the stack, while the old standards relied on either feed rate limits (metals), total loading to the environment (chlorine), or risk assessments. Under the old standards, each of these parameters took into consideration the physical location of the facility, the air flow rate in the stack, the height of the stack, and other site-specific parameters to determine emission limits in their permits. With the revised standards, hazardous waste incinerators will have to meet the same concentration standards unless site-specific risk assessment shows that these levels will harm human health and the environment--"omnibus" authority again. However, there is little doubt that the revised standards will be stricter than the old standards and will force facilities to make choices on how to meet the revised standards.
Types of upgrades needed
Because of the way the emission standards were developed, some facilities should already meet them. In addition, since individual permits vary in their restrictions, facilities with more restrictive permits may need fewer modifications. However, since the emission standards were developed on a pollutant-by-pollutant basis, many facilities will need at least some modifications to meet the revised standard.
The revised emission standards are based on technology. Although EPA defines the technology that is expected to meet the standards, they will not require the installation of specific equipment. They only specify that each incineration unit meet all the requirements. Simple installation of the designated technology may not be sufficient to meet the revised emissions standards. Rather, the facility must show that the new equipment meets emissions standards before the facility can continue to operate. The practical problems of meeting all standards simultaneously make this more difficult.
Most likely, facilities will opt to add stages to their current air pollution control devices to tackle individual problems. For instance, if a facility has problems meeting the new mercury or dioxin standards, they may choose to inject activated carbon or run the flue gas through a fixed bed. Both of these technologies are available but are not without problems. Fixed beds of activated carbon must be kept below the autoignition temperature to prevent a fire. Both create additional waste that requires treatment by incineration, recycling, or disposal in a hazardous waste landfill. Thus, the choices are not always simple, straightforward, and easy to engineer.
One of the more difficult choices facing facilities is meeting the requirement to install and operate a continuous emissions monitor for particulate matter. While there is considerable debate regarding whether particulate matter monitors are sufficiently developed for use as a compliance tool in the United States, it appears likely that they will be required in the near future. If a continuous monitor is required, you will have to choose which monitor best suits your needs.
There are two primary factors a facility will need to consider when choosing the type of monitor to be installed--whether your stack is wet or dry and the variability of your waste streams. Most of the commercially available monitors should work on a dry stack. Monitors based on <I>in situ<I> light scattering have the advantage of being the least expensive, the easiest to install, and requiring the least amount of maintenance. The light scattering monitors have the disadvantage of being influenced by particle size, shape, and color.