Common concerns for illinois citizens in regard to their water quality:
Nitrate -- May be an indication of water contamination if found at unusual levels. The drinking water standard for nitrate as nitrogen is 10 mg/L. Reverse osmosis or distillation can remove nitrate if necessary.
Hardness -- A measure of the amount of calcium and magnesium in the water, resulting in accumulation of scale on fixtures and in plumbing. Also increases the amount of detergent necessary to produce a lather. A water softener removes hardness and exchanges it for sodium.
Sulfur -- "Rotten-egg" odor is not a health concern but is unpleasant and can cause gray or black tarnish and stains. Carbon filtration or oxidation is used to eliminate sulfur odor.
iron -- At levels greater than 0.3 mg/L, can stain laundry and porcelain. A water softener or oxidizing filter can remove iron from water.
Salty or bitter Taste -- Due to a large amount of dissolved minerals, such as sodium, chloride, and sulfate in the water. Excessive minerals are removed from water by reverse osmosis or distillation.
Coliform bacteria -- An indicator organism used to determine if water is likely to contain pathogens. ideally, water should contain no coliforms. The water source should be protected so coliforms do not enter the water.
Lead -- Typically due to plumbing components, it can accumulate in the body and cause organ and nervous system problems. Flushing the water until it is as cold as it can get will eliminate lead from the plumbing system.
pesticides -- An indication of surface contamination. Many pesticides have various drinking water standards associated with them. proper construction should keep pesticides out of the water, but if this is not successful then pesticides can usually be removed by carbon filtration.