This paper discusses a potential process that removed up to 90% of the calcium from a groundwater supersaturated with carbonic acid during aeration, termed a "spontaneous aeration" process. The kinetics of calcium removal was accelerated by adding a nuclei particle or increasing aeration rates. Calcium removal occurred between pH 8.0 and 8.5 as calcite became supersaturated. A second softening process, involving conventional lime and soda ash addition plus a metal salt and/or polymer, was also examined. Ferric chloride addition decreased the operating pH from 11 to 10.5, thus reducing magnesium removal while still achieving high calcium removal. Ferric chloride improved settlability, as measured by turbidity. The addition of a polymer also improved settlability, but not overall hardness removal. The viscosity of settled sludge increased with higher polymer dosages, suggesting that viscosity measurements may be a good indicator of the "stickiness" of sludges.