Any special assessment within a city of the metropolitan class, except when payable in installments, shall be deemed delinquent if not paid within fifty days after the passage and approval of the ordinance levying such special assessment, and interest at the rate specified in section 45-104.01, as such rate may from time to time be adjusted by the Legislature, payable in advance, shall be paid on any delinquent special assessment from the time such special assessment shall become delinquent.