Section 430.21 - Specialized definitions(a) The general definitions, abbreviations, and methods of analysis set forth in 40 CFR part 401 and § 430.01 of this part apply to this subpart.(b)Baseline BAT limitations or NSPS means the BAT limitations specified in § 430.24(a) (1) or (2) , as applicable, and the NSPS specified in § 430.25(b) (1) or (2) , as applicable, that apply to any direct discharger that is not "enrolled" in the "Voluntary Advanced Technology Incentives Program."(c)Enroll means to notify the permitting authority that a mill intends to participate in the "Voluntary Advanced Technology Incentives Program." A mill can enroll by indicating its intention to participate in the program either as part of its application for a National Pollutant Discharge Elimination System (NPDES) permit, or through separate correspondence to the permitting authority as long as the mill signs the correspondence in accordance with 40 CFR 122.22 .(d)Existing effluent quality means the level at which the pollutants identified in § 430.24(a)(1) are present in the effluent of a mill "enrolled" in the "Voluntary Advanced Technology Incentives Program."(e)Kappa number is a measure of the lignin content in unbleached pulp, determined after pulping and prior to bleaching.(f)Voluntary Advanced Technology Incentives Program is the program established under § 430.24(b) (for existing direct dischargers) and § 430.25(c) (for new direct dischargers) whereby participating mills agree to accept enforceable effluent limitations and conditions in their NPDES permits that are more stringent than the "baseline BAT limitations or NSPS" that would otherwise apply, in exchange for regulatory- and enforcement-related rewards and incentives.