Ammonia is included on the EPCRA Section 313 toxic chemical list with the qualifier "includes anhydrous ammonia and aqueous ammonia from water dissociable ammonium salts and other sources; 10 percent of total aqueous ammonia is reportable under this listing" (40 CFR Section 372.65). As this qualifier indicates, the quantities applied to EPCRA Section 313 threshold determinations depend on the specific form of ammonia manufactured, processed, or otherwise used, and release and other waste management calculations also depend on the form of ammonia released or otherwise managed as waste. How does one distinguish between anhydrous ammonia and aqueous ammonia for the purpose of this listing? What are the differences in threshold determinations and release and other waste management calculations for the two forms of ammonia?
The term "anhydrous" means "lacking water," whereas "aqueous" means "dissolved in water." Anhydrous ammonia (in either the gas or compressed liquid state) may, however, contain a small amount of water. The presence of water in anhydrous ammonia does not constitute aqueous ammonia unless the amount of water present is sufficient to dissolve the ammonia. If ammonia is not actually dissolved in water, then the ammonia must be considered anhydrous. Facilities must be able to distinguish between anhydrous ammonia and aqueous ammonia when making threshold determinations and release and other waste management estimates because different percentages of the total amount of ammonia apply depending on the form of ammonia present. If anhydrous ammonia is manufactured, processed, or otherwise used, then 100 percent of the anhydrous ammonia must be counted when determining whether an activity threshold has been exceeded. If the facility exceeds an activity threshold for ammonia (anhydrous and/or aqueous), then all of the anhydrous ammonia released and otherwise managed as wastes must be included in the facility's release and other waste management calculations. Total aqueous ammonia includes both the ionized (NH4 + ) and un-ionized (NH3) forms of ammonia present in aqueous solutions. When a facility manufactures, processes, or otherwise uses aqueous ammonia, it is conducting a threshold activity on 100 percent of the aqueous ammonia. However, the facility owner or operator counts only 10 percent of the total aqueous ammonia involved in a covered activity when making threshold determinations. Similarly, when estimating annual releases and other waste management estimates of ammonia from a facility, only 10 percent of the total aqueous ammonia must be included in the calculations. Dissolving water-dissociable ammonium salts in water constitutes the manufacturing of aqueous ammonia. According to the ammonia qualifier, 10 percent of the total amount of aqueous ammonia created must be applied toward the 25,000-pound manufacture threshold as well as the processing or otherwise use threshold, depending on the use of the aqueous ammonia at the facility. However, since 100 percent of the anhydrous form of ammonia is reportable under the ammonia listing, all anhydrous ammonia used to make aqueous ammonia must be applied toward either the processing or otherwise use threshold, depending on the use of the aqueous ammonia solution at the facility. Further guidance on reporting for ammonia can be found in the Guidance for Reporting Aqueous Ammonia and the Revised 1998 EPCRA Section 313 Questions and Answers Document.