Wastewater Operator’s Guide to Preparing for the Certification Examination (WEF) (Levels 1-4)The Wastewater Operators Guide to Preparing for the Certification Examination was prepared jointly by the Water Environment Federation, the Association of Boards of Certification (ABC), and the Certification Commission for Environmental Professionals (C2EP). It outlines what you can expect from the exam, provides key formulas, and lets you test your skills with sample questions. Use the book to study on the go, and then when you get home, take an