Wastes containing permissible constituents, with BOD, suspended solids, total phosphorus, and, if so established, other concentrations greater than that set by the Director of Public Works: will be subject to a sewer service surcharge, which is to be based upon the unit cost of handling and of treating the wastes at the receiving treatment plant; and may be subject to discharge limitations. City Code, 1976/83, art. 25, §6(a)(5) Ord. 75-914 Ord. 84-129 Ord. 91-775