AWWA WQTC69413

In order to comply with the United States Environmental Protection Agency's (USEPA's) arsenic standard and the manganese and iron secondary maximum contaminant levels (MCLs) in water (10µg/L, 50µg/L, and 300µg/L, respectively), many Midwestern water utilities must add a strong oxidant before filtration to oxidize the reduced forms of arsenic, manganese and iron. Free chlorine and permanganate are the two most common chemical oxidants used to address arsenic, manganese, and iron issues. In the Midwestern United States, engineering practices have traditionally favored the use of permanganate as the oxidant of choice, followed by green sand filtration to remove manganese from source waters. Most water treatment plant personnel, however, find permanganate undesirable to use for a number of reasons, including: it stains everything it contacts; overdosing causes "pink" water; under-dosing can cause manganese spikes; and, handling issues. There is a real need to compare the effectiveness of chlorine and permanganate in manganese (and arsenic) removal systems and, more importantly, to provide better guidance as to when each oxidant is most appropriate to address an iron, manganese, and/or arsenic problem. Observations from full-scale treatment plants are used to illustrate the appropriate applications of chemical oxidants. Includes 2 references, table, figures.