The Ottawa Water Treatment Facility takes water from four deep rock wells with radium levels ranging from 2.6 pci/l in well 11 to 16.9 pci/l in well 8 and processes the raw water in two reverse osmosis treatment facilities. The Well 10 facility has a capacity of 1.65 MGD and the Central Plant a capacity of 4.95 MGD for a total finished water capacity of 6.6 MGD. The Central plant was designed to add a fourth treatment train for an additional 1.65 MGD in the future. Finished water has been consistently tested at below the radium standard of 5pci/l. The treatment facility consists of four stainless steel reverse osmosis treatment trains manufactured by GE Osmonics. Each train is fitted with 30, seven foot long membrane vessels arranged in a 22-8 array and holding 210 membranes. Raw water is pumped through the membranes with vertical turbine pumps manufactured by Afton Pump Company. Permeate water is mixed with 32% raw water and stored in clear wells located below the treatment plant. 1300 GPM vertical turbine pumps pump the finished water from the clear wells into the distribution system.
The City of Ottawa water system was out of compliance with radionuclide standards to be enforced in December 2009. The City engaged McClure Engineering to prepare a study to evaluate available options and to make recommendations for water treatment. During the study engineers and city officials toured several water treatment facilities to gain further knowledge and insight into the options available. The study concluded that although not the least costly option, reverse osmosis treatment was the best option for Ottawa. Plans were prepared for two treatment plants, a new well and transmission water mains. New treatment facilities are capable of production 6.6 MGD of finished water with an acceptable radium level, significantly reduced hardness, with a recovery rate of 85%. Permits were obtained to discharge the concentrate stream from the treatment process directly to the Fox River, a first for Illinois.