If established under the provisions of Chapter 302 of the Revised Code, the department of water and sewers shall assume all duties and perform all functions related to the operation of the county’s sewer and water systems. The board of county commissioners may create a board of trustees to serve at its pleasure and may assign to such board such functions and responsibilities as are by law delegated to the board of county commissioners in Chapters 6117. and 6103. of the Revised Code as they pertain to the operation of a county sewer system and a county water system.