(2) Treatment facility. For purposes of subparagraph (1)(i) of this paragraph, a treatment facility is a facility which (i) is used to abate or control water or atmospheric pollution or contamination by removing, altering, disposing, or storing of pollutants, contaminants, wastes, or heat and (ii) is used in connection with a plant or other property in operation before January 1, 1969. Determinations under subdivision (i) of this subparagraph shall be made solely by the Federal certifying authority. See subparagraph (3) of this paragraph. For meaning of the phrases plant or other property and in operation before January 1, 1969, see subparagraphs (4) and (5), respectively, of this paragraph.