35 Pa. Stat. § 691.211
For the purpose of financing the cost and expense, or its share of the cost and expense, of constructing or acquiring or extending any sewer, sewer system or sewage treatment works, either singly or jointly with other municipalities, a municipality may issue non-debt revenue bonds secured solely by a pledge, in whole or in part, of the annual rentals or charges imposed for the use of such sewer, sewer system or sewage treatment works. Said bonds shall not pledge the credit, nor create any debt, nor be a charge against the general revenues, nor be a lien against any property of the municipality, but shall be a lien upon and payable solely from the annual rentals or charges for the use of the sewer, sewer system or sewage treatment works.
35 P.S. § 691.211