The department is hereby authorized to establish a schedule of reasonable fees, such schedule taking into consideration the volume of the discharge and treatment costs, for application for issuance of SPDES permits to compensate the department for its expenses hereunder, giving due recognition to the amount of federal assistance available; provided, however, that the department shall not charge a publicly owned drinking water treatment plant the rates charged industrial facilities, but shall consider such plants to be municipal facilities for the purposes of the imposition of fees pursuant to section 72-0602 of this chapter.