Assessment of calculation methods for calcium carbonate saturation in drinking water for DIN 38404-10 compliance

Abstract

Abstract. The new German standard for calcium carbonate saturation in drinking water, DIN 38404-10, 2012 (DIN), marks a change in drinking water standardization from using simplified equations applicable for nomographs and simple calculators to using extensive chemical modeling requiring computer programs. The standard specifies the chemical outlines for the modeling and presents a dataset with 10 water samples for validating used computer programs. The DIN standard, as well as the Standard Methods 2330 (SM) and NEN 6533 (NEN) for calculation of calcium carbonate saturation in drinking water were translated into chemical databases for use in PHREEQC (USGS, 2013). This novel approach gave the possibility to compare the calculations as defined in the standards and internationally accepted chemical databases provided with PHREEQC. From the research it is concluded that the computer program PHREEQC with the developed chemical database din38404-10_2012.dat complies with the DIN standard for calculating Saturation Index (SI) and Calcite Dissolution Capacity (Calcitlösekapazität) or Calcium Carbonate Precipitation Potential (CCPP). This compliance is achieved by assuming equal values for molarity as used in DIN (obsolete) and molality as used in PHREEQC. From comparison with internationally accepted chemical databases it is concluded that the use of molarity limits the use of DIN to a maximum temperature of 45 °C. For current practical applications in water treatment and drinking water applications, the PHREEQC database stimela.dat was developed within the Stimela platform of Delft University of Technology. This database is an extension of the internationally accepted chemical database phreeqc.dat and thus in compliance with Standard Methods 2330. The database stimela.dat is also applicable for hot and boiling water, which is important in drinking water supply with regard to scaling of calcium carbonate in in-house drinking water practices. The SM and NEN proved to be not accurate enough to comply with DIN, because of their simplifications. The differences in calculation results for DIN, SM and NEN illustrate the need for international unification of the standard for calcium carbonate saturation in drinking water.

Restoration and meteorological variability highlight nested water supplies in middle altitude/latitude peatlands: Towards a hydrological conceptual model of the Frasne peatland, Jura Mountains, France

“…Considering the strong correlation between [Ca] and EC ( R 2 = 0.98) in our samples and the acidity of peat water (mostly pH < 7), we considered calcium as a conservative tracer (de Moel et al, 2013; Hart et al, 2011) allowing to evaluate water and solutes transfer processes throughout the peat column by comparing vertical [Ca] variability with a constant source diffusive equation (Equation ) proposed by Crank (1975): where C ( x , t ) is the calculated cation concentrations, C 0 (mg·L −1 ) the initial and assumed constant concentration at the substratum/peat interface, x (m) the distance from this interface, t (s) the time, erfc the complementary error function and D * the effective diffusion coefficient. D * was determined from the molecular diffusion in solution for cations adjusted by a tortuosity factor, both respectively set at 2.10 −9 m 2 ·s −1 and 0.22 according to Freeze and Cherry (1979) and Fraser et al (2001).…”

Taya Caves, a Buddhist marvel hidden in underground Japan: stone properties, deterioration, and environmental setting

“…, and has higher kinetics in acid solutions (especially when pH is below 6 or 5) whereas, in basic and alkaline solutions, rather precipitation is favored [47][48][49][50][51][52]. Pyrite is the most common species involved in mudrock weathering, and can alter when exposed to air at any pH value, with higher kinetics when in contact with water and in framboidal minerals [53][54][55].…”

Real Time 3D Observations of Portland Cement Carbonation at CO2 Storage Conditions

“…The saturation index depends on pH, being lower at alkaline and higher at basic conditions. 51 The precipitation of CC̅ inside the channel started after an induction time of t ∼ 90 min into the first hydrostatic phase. This was the time needed for the water in the channel to reach oversaturation and for the particles to grow to a detectable size.…”