Impact of Water Blending on Calcium Carbonate Equilibrium in Water Distribution Systems

A set of equations describing calcium carbonate equilibrium in water was applied to water mixtures found in an existing water supply system. A theoretical model was used to calculate the total alkalinity and pH resulting from the mixing of two waters of different origin. The accuracy of the results was tested experimentally. The experimental results confirmed the theoretical calculations with acceptable accuracy. Two different sources of possible errors in the Langelier saturation index computations were investigated and compared graphically. The first source resulted from possible inaccuracy of data, assumed to be equal to the standard errors of laboratory measurements. The second was caused by neglecting the inorganic complexes of calcium and magnesium in calculations.