In order to carry out and effectuate the purposes of the commission, every commission is authorized to enter upon and use and connect with any existing public drains, sewers, conduits, pipelines, pumping and ventilating stations and treatment plants or works or any other public property of a similar nature within the district, deemed proper by the commission in the exercise of the powers and performance of the duties set forth in this chapter, and, if deemed necessary by the commission, close off and seal outlets and outfalls therefrom. The commission shall not, however, take possession of any such treatment plant unless it acquires the same by purchase, condemnation or otherwise.