The Council shall annually determine and fix the unit costs for use of the sewage works and facilities on the basis of flow and determine surcharge unit costs for BOD, SS and any other pollutant, taking into consideration the cost of treatment of sewage, and may increase or decrease the unit cost as often and in amounts as may reasonably be required to accomplish the purposes of this subchapter. The cost to be fixed by the Council shall be determined and allocated in each of the following categories:
(A) Category A. Includes debt service for bond issues for existing and proposed sewage works and facilities and any desired or required coverage for debt service; and
(B) Category B. Includes operation and maintenance of existing and proposed sewage works and facilities.
(1999 Code, § 99.04)