The treasurer of the board of seven-director districts is the custodian of all moneys collected for liquidating any bonded indebtedness and interest on the same, and is responsible on his official bond for the safekeeping and proper appliance of the debt service fund received by him, and also for any loss incurred or damage resulting from his failure to cancel any and all redeemed bonds, as required in section 108.160. He shall promptly pay the interest on bonds when due, and pay off and cancel the bonds as rapidly as possible.