The disconnection of any such area of land shall not exempt it from taxation for the purpose of paying any indebtedness contracted by the corporate authorities of the municipality, prior to the filing of the petition for disconnection. On the contrary, the territory shall be assessed and taxed to pay such indebtedness until this indebtedness is completely paid, the same as though the territory had not been disconnected. Except for this purpose, no county clerk shall include disconnected territory within the limits of the municipality from which the territory has been disconnected.