The board of trustees of any sanitary district organized under this article shall have power to build and construct and to defray the costs of providing for the disposal of the sewage thereof including the sewage and drainage of any incorporated city, town, or village within the boundaries of such sanitary district, and to save and preserve the water supplied to the inhabitants of such district from contamination and for that purpose may build, construct, enlarge, repair, maintain and operate a sewage treatment plant or plants together with such intercepting sewers, trunk sewers, lateral sewers, pumping and ejector stations, force mains, outfall sewer or sewers, channels, drains, and all other necessary or useful and convenient appurtenances in connection therewith: Provided, That such works established or constructed by said sanitary district shall serve and benefit the entire territory within the sanitary district and not otherwise: Provided further, That nothing in this article shall be construed to limit the power of the municipalities included in said sanitary district from constructing and establishing drains and sewers within the corporate limits of such municipality: And provided further, That before any general outlet, main or trunk sewer shall be constructed by any such municipality, included in said sanitary district, a plan or profile of any such proposed general outlet, main or trunk sewer shall be filed in the office of the board of trustees of said sanitary district and be approved by said board. Such main channels, drains, ditches and outlets for carrying off and disposing of the drainage, including the sewage of such sanitary district, together with such adjuncts and additions thereto as may be necessary or proper to cause such channels or outlets to accomplish the end for which they were designed, and such disposal plants and works for disposing of the sewage of said sanitary district may extend outside the territory included within such sanitary district and the rights and powers of said board of trustees over the portion of such channel or outlet or sewage disposal plant, or works, lying outside of such sanitary district, shall be the same as those vested in said board over said portions of such channels or outlets, plants or works, within the said sanitary district.

Such board may also treat and purify such sewage so that when the same shall flow into any lake or other watercourse, it will not injuriously contaminate the waters thereof, and may adopt any other feasible method to accomplish the object for which such sanitary district may be created, and may also provide means whereby the said sanitary district may reach and procure supplies of water for diluting and flushing purposes: Provided, however, That nothing herein contained shall be construed to empower and authorize such board of trustees to operate a system of waterworks for the purpose of furnishing or delivering water to any such municipality or to the inhabitants thereof.