(b) The board of supervisors may designate the county treasurer of the county in which the drainage district, or the largest portion thereof, is located, as ex officio treasurer of the drainage district, for the purpose of collecting and disbursing taxes and assessments. The treasurers of the counties in which the smaller parts of the district are located shall pay to the ex officio treasurer any and all funds collected by them for the benefit of the drainage district. The ex officio treasurer shall give a receipt for the funds received. A duplicate shall be filed in the office of the clerk of the county of which the person receiving same is treasurer. It shall be the duty of the treasurer, who is ex officio treasurer of the drainage district, to pay any money of the drainage district on hand upon warrants, signed by the chairperson and attested by the secretary of the board of supervisors of the district, when presented for payment.