Federal categorical pretreatment standards or state requirements and limitations on discharges shall apply in any case where they are more stringent than those in this chapter. To the extent the federal regulations contain stricter standards, the categorical pretreatment standards, found in 40 C.F.R. Chapter I, Subchapter N, pts. 405 through 471, are hereby incorporated by reference into this chapter. To the extent the state regulations contain stricter standards, the pretreatment standards found in 327 I.A.C. 5-12-6 are hereby incorporated by reference into this chapter.