Solutions for Reducing the Extreme Hardness in Treated Water

A technology aimed at reducing extremely high water hardness in Chotěšov, a village in the Czech Republic, was developed and tested. Three treatment methods were evaluated under laboratory conditions: softening filtration using a cation exchange resin in the Na+ cycle (resulting in a 72% reduction in hardness); nanofiltration (NF); and reverse osmosis (RO), which reduced hardness by 71% and 96%, respectively. The mixing of the permeate with treated groundwater at a volume ratio of 1:1 resulted in a further reduction in hardness to 41% with NF permeate and to 53% with RO permeate, relative to the original value.