No statement contained in this section 8-2-6 shall be construed to prevent any special agreement or arrangement between the city and any industrial concern whereby an industrial waste of unusual strength or character may be accepted by the city for treatment, subject to payment therefor, in accordance with the provisions of subsection 8-2-6-1C2 of this chapter and approval by the Illinois environmental protection agency. (2006 Code § 7-2-11)