The board, pursuant to a resolution entered in its minutes, may distribute, among the landowners of the district, any funds in the treasury belonging to the district which were collected on an assessment on which no bonds are outstanding (or collected by way of interest or penalties on the assessment or by the rental, sale or redemption of delinquent land under the assessment) and which appear to the board to be greater than required to meet all obligations incurred or to be incurred for the purposes for which the assessment was levied, such distribution to the landowners to be made in the proportion that they were assessed on such assessment.