Collection Systems Operator’s Guide to Preparing for the Certification Examination (WEF) (Levels 1-4)This guide was prepared jointly by the Water Environment Federation, the Association of Boards of Certification, and the Certification Commission for Environmental Professionals (C2EP). The third edition of this critical study guide has been updated to reflect new Need to Know Criteria and core competencies for collection system operators. The questions included in this guide have been chosen to sample as many different aspects of a collection system