The board of directors shall have authority to receive bids for all work which it may desire to have done by contract or for material and supplies to be used in connection with such work, which bids shall be received after reasonable advertisement therefor and when opened shall be read in public session. The board of directors may award contracts based upon the bids to the lowest responsible bidders, except that the board of directors may, for such reasons as appear to it good and substantial, reject all bids. The board of directors shall have power and authority to do all of such work and to purchase materials and supplies without advertising for bids and without entering into contract with any other persons or companies in relation thereto.