The board, in the operation of the plant or plants or sewerage systems, from time to time may employ agents, servants, and employees as it may deem necessary in the operation of the plant and may likewise discharge such agents, servants, or employees and such others as may have been employed in the operation of the plants or sewerage systems at the time of the creation of the board. No person related by blood or marriage to any member of the board shall ever be employed by it for any purpose.