When any special assessment is made under this Act, the ordinance, authorizing such assessment may provide that the entire assessment and each individual assessment be divided into annual installments, not more than twenty in number. In all cases such division shall be made so that all installments shall be equal in amount, except that all fractional amounts shall be added to the first installment so as to leave the remaining installments of the aggregate equal in amount. The said several installments shall bear interest at the rate of not to exceed six per cent per annum; both principal and interest shall be payable, collected and enforced as they shall become due in the manner provided for the levy, payment, collection and enforcement of such assessment and interest, as provided in Article 5 of the “Illinois Drainage Code”, approved June 29, 1955, as heretofore and hereafter amended.