The treasurer of the city in which the waterworks or electric-light plant is located shall be ex officio treasurer of the board of public utilities. Except as otherwise authorized, all funds and property in the treasurer’s hands belonging to the water and light department shall be subject to the control of the board, and it shall be the duty of the treasurer to receive and receipt for daily the money collected by the board, and to pay out the same when ordered by the city or the board upon warrants signed by the mayor and city clerk or chairman or vice-chairman of the board and countersigned by the manager of collections and accounts, certifying that such warrant is issued by authority of the city or the board. The ex officio treasurer shall give a surety bond to the board in such amount as it may deem necessary, the bond to be approved and paid for by the board.