Any municipality may acquire, or construct, and maintain and operate a combined waterworks and sewerage system either within or without the corporate limits thereof. A municipality owning and operating a waterworks or sewerage system may provide for the inclusion of that waterworks or sewerage system or the combination of the 2 in a combined waterworks and sewerage system under this Division 139, and in connection therewith may provide for paying or refunding any unpaid obligations which are payable solely from the revenue of or which are secured by a mortgage of that waterworks or sewerage system, or any part thereof included in the combined waterworks and sewerage system. Any municipality owning and operating a combined waterworks and sewerage system may also provide for paying or refunding any unpaid obligations which are payable solely from the revenue of the combined waterworks and sewerage system. A municipality owning, acquiring, or constructing and providing for the operation of a combined waterworks and sewerage system may improve and extend that system, and may impose and collect charges or rates for the use of that system as provided in this Division 139. A municipality may also, when determined by its corporate authorities to be in the public interest and necessary for the protection of the public health or in the best interests of the municipality and its environs, enter into and perform contracts, whether long-term or short-term, with any other municipality within a radius of 25 miles of its corporate limits and construct water mains to such municipality and supply water to such municipalities on the request of any such municipality; provided, that such water mains be constructed and that such municipality purchase water on a long term basis at rates sufficient to amortize the cost of the construction of such water mains and pay the cost of maintenance and operation thereof, as hereinafter provided in this Division 139, and also with any industrial establishment for the provision and operation by the municipality of sewerage facilities, either within or without the corporate limits of such municipality, to abate or reduce the pollution of waters caused by discharges of industrial wastes by the industrial establishment and the payment periodically by such municipality or municipalities or the industrial establishment to the municipality of amounts at least sufficient, in the determination of such corporate authorities, to compensate the municipality for the cost of providing (including payment of principal and interest charges, if any) and of operating and maintaining any such facilities. This amendatory Act is not a prohibition upon the contractual and associational powers granted by Article VII, Section 10 of the Constitution.