All acts of such officials and of all county and state officials relating to levying taxes and special assessments heretofore levied and assessed for the payment of the principal and interest on such bonds and for all other purposes necessary and incidental to the business of the drainage district if done in substantial compliance with the laws as printed in the statute book, are hereby validated and legalized. Any taxes and special assessments in an amount sufficient to pay the principal and interest of bonds now outstanding, shall be annually assessed and collected in each of the drainage districts and applied to the payment of the bonds and interest thereon, and express authority so to do is hereby delegated to the proper drainage district officials and county officials in any county in which the drainage districts are located.