As we learned earlier this year, the existing plant was designed to soften water using a zeolite system. The zeolite softeners (pictured right) are badly deteriorated and are no longer in operable condition. In their plans for the new water plant, the City is proposing a new treatment process - direct membrane treatment. Direct membrane treatment has water pumped directly from wells through membranes without additional pretreatment processes required.
As the City is not currently using direct membrane treatment technology, the Iowa DNR requires a pilot study in order to confirm the effectiveness of direct membrane treatment with Grinnell’s specific raw water characteristics. The pilot study became fully operational earlier this month and will last for three months.
After the pilot study is complete, the membranes will be autopsied to evaluate presence of fouling (buildup of particulate material on the membrane such as limescale, mineral deposits, etc.) to determine the condition of the membranes and efficacy of this treatment process. At that point, new membranes can be installed in the pilot and the pilot can be manipulated to optimize performance for treatment of Grinnell’s raw water. Information gathered from the pilot study will be used to design the full-scale water treatment plant.
Below are pictures of the pilot study. We'll share more information on the Water Treatment Plant process as it becomes available.