Corrosion Control If sequestration of iron and manganese is practiced, the chlorine residual in the water system should always be maintained at or above: Tags: Certification Exam Prep, Chlorine Residual, Distribution System, Iron, Manganese, Sequestration, Water Treatment Read more articles Previous PostWater Treatment and Distribution System Next PostWater Treatment and Distribution System You Might Also Like Reasons New Managers and Supervisors Fail: Lack of Training March 9, 2015 Fluoridation January 24, 2017 State Exam Information | California Treatment and Distribution Exam Fees June 29, 2018 Post author: Post published:January 11, 2017 Post category:Certification Exams / Distribution / Water Treatment