The county treasurer shall deposit in the county treasury to the credit of the bond fund of the district all money collected upon any assessment upon which bonds have been issued, including all the following:

Money collected upon any assessment upon which bonds have been issued shall be used exclusively for the payment of principal and interest of the bonds issued on the assessment.

The county treasurer shall transmit to the treasurer of the district all canceled bonds and coupons received in payment on any delinquent sale and a memorandum of all sums endorsed as paid upon account of purchase money on any specified bonds or coupons. All money collected by any county treasurer upon account of an assessment on which bonds shall not have been issued shall be similarly accounted for to the treasurer of the district, and shall be credited to the general fund of the district.

Any balance remaining in the bond fund after payment in full of the principal and interest of all outstanding bonds of the district shall be transferred by the county treasurer to the general fund of the district.