Water hardness is the sum of magnesium and calcium ions that occur in all possible combinations. Table 1 presents the main distribution of water hardness. General hardness by cations General hardness by anions carbonate hardness non-carbonate hardness calcium hardness Ca(HCO3)2, Ca(OH)2, CaCO3 CaSO4, CaCl2, Ca(NO3)2 magnesium hardness Mg(HCO3)2, Mg(OH)2, MgCO3 MgSO4, MgCl2, Mg(NO3)2 […]