By special contract between the city and any industrial user, industrial wastewater of unusual strength, composition or quantity may be accepted by the city for treatment at a charge fixed by such contract. The city may enter into and perform such special contracts, not to exceed a term of five years, with any industrial user, for the provision and operation by the city of sewage facilities to accept discharges of industrial wastewater by the industrial user and the payment, periodically or otherwise, by the industrial user to the city of amounts sufficient to compensate the city for such portion of the cost of providing, operating, and maintaining the sewage facilities serving such industrial user as the city council shall determine. Nothing contained in this section shall be construed to exempt any industrial user from any of the provisions of Article IV which shall be in effect at the time when any special contract executed pursuant to this section shall become effective. Any contract executed pursuant to this section may contain as a part thereof the terms and conditions of a permit issued in accordance with Article IV. (Ord. No. 1271, § 1 (part).)