No statement in this Chapter shall be construed as preventing any special agreement or arrangement between the City and any commercial or industrial concern whereby a waste of unusual strength or character may be accepted by the City for treatment, providing the acceptance of such wastes, either singly or in combination with other wastes shall not result in:
(b) Violations of the NPDES permit issued to the City.
(c) The impairment of the sewage works operations.
(d) Violations of Categorical Pretreatment Standards.
(e) Limitations with respect to final disposal of any pollutant removed or separated at the wastewater treatment plant.
(f) Added cost without adequate recompense to the City.