This document is an instructional module package prepared in objective form for use by an instructor familiar with operation and maintenance of rotating biological surface (RBS) wastewater treatment systems. Included are objectives, instructor guides, student handouts and transparency masters. This is the second level of a three module series. The module considers the role and function of the RBS unit, factors affecting unit performance, solutions to adverse situations, design approaches, maintenance and reporting requirements. (Author/RH)