No statement contained in this subchapter shall be construed as preventing 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 § 51.30 by the industrial concern, provided that the payments are in accordance with state and federal guidelines for a user charge system.
('74 Code, § 27-80) Penalty, see § 51.99