Improved Pretreatment Processes for Wastewater Reuse Using Reverse Osmosis

摘要

Colloidal and dissolved organic matter was shown to be a primary foulant in reverse osmosis treatment of wastewaters for reuse. A two-phase study was conducted on pretreatment methods to remove these organic foulants. In the first phase, river water and petroleum refinery effluent were treated with inorganic coagulants (ferric chloride and alum) under a variety of conditions. The clarified waters were then tested for fouling potential in reverse osmosis, at high membrane fluxes (25 to 35gfd) to accentuate fouling rates. Fouling flux decline was nearly always encountered; also, organic removal was ineffective. In Phase II, a novel set of thin film composite ultrafiltration membranes were developed. These consisted of anionic methyl cellulose graft copolymers deposited as membranes on microporous supports. These membranes removed organic foulants from river water and petroleum refinery effluent, and were fairly effective on municipal secondary effluent in ultrafiltrations at 50 psi.