Successful Removal of Manganese and Other Trace Constituents from Surface Water of Highly Variable Quality Using Intermittent Operation of Rapid Clarification

A complex treatment system was designed and built for an industrial facility to process raw stormwater prior to discharge to the environment, which required meeting a series of limits from a stringent NPDES permit. After extensive pilot studies, a treatment train consisting of pre-oxidation, rapid clarification, sand filtration, bag filters and granular activated carbon was selected. A major challenge for this system was its intermittent operation, as it was dictated by weather conditions. Rapid clarification performed successfully as a robust pretreatment to neutralize turbidity peaks during strong storms, which in turn allowed optimal operation of the downstream units. Meeting the manganese limit of 0.05 mg/L represented the most challenging part of the project, but was successfully achieved with a systematic approach to operation and monitoring. Careful consideration was given to the operation of the system under continuous startup and shutdowns corresponding to operation before, after and in between rain events.