City of Carmel

City of Carmel

Location: Carmel, Indiana

Carmel, Indiana is a rapidly growing suburb located 20 miles north of Indianapolis. Due to a population explosion, Carmel was facing a water deficit and needed to move quickly to avoid summertime water shortages. The City teamed with Tonka Water to design a new 4 MGD water treatment facility on a tight deadline. The decision was made in 2004 to design the new peaking iron removal water treatment plant around Tonka Water’s Dualator® III package treatment unit; which incorporates aeration, detention, and filtration. This proved to be a very economical treatment solution and the pre-purchase of equipment aided in meeting the short timeline of the project. The Carmel Water Treatment Facility includes three 950 gpm Dualator® III units for a total plant capacity of 4 MGD.

Tonka Water’s Dualator® III is a low-profile water treatment system that incorporates aeration, detention, and filtration in a single packaged unit. The treatment process begins as the raw water enters the aerator section of the Dualator® III where air is introduced to promote iron oxidation. The oxidation is completed while the water serpentines through the baffled 30-minute detention section. Water from the detention section is uniformly collected and transferred by gravity to the filter compartment where it is uniformly distributed into each filter cell. The water then filters through a dual media consisting of silica sand and anthracite where the iron precipitates are removed and the effluent water flows into the clearwell.


The concentration of iron in the raw water at Carmel, IN is relatively high. Tonka Water’s Dualator® III treatment units have been effective in delivering excellent effluent water quality, as indicated below:

Raw Water
Finished Water
Iron (Fe)2.75 mg/LNot Detected

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