DIN 38404-10:2012-12

The behaviour of water with respect to the calcium carbonate modification calcite is described by the calcite saturation condition. An evaluation of the corrosion chemical properties of water interacting with materials usually coming into contact is often associated. The Trinkwasserverordnung ("German Drinking Water Regulation") contains the parameter "calcite dissolution capacity" to be monitored (attachment 3, indicator parameters) and requires calculation in accordance with this standard. This standard contains all required information for the sufficiently accurate calculation of the calcite dissolution capacity by means of suitable programs. Testing the suitability of calculation programs with regard to relative and absolute accuracies of calculation results is possible with the given example data sets and a test scheme independent of analysis data. This standard specifies a calculation method with which calcite saturation or the quantities, calcite dissolution capacity or precipitation capacity used to describe calcite saturation can be calculated. This standard applies to waters intended for distribution as potable water and serves exclusively for the determination of the aforementioned quantities. The calculation method also allows calculation of other water parameters (for example, saturation index, species concentrations); these are not subject of this standard, however. The maximum quantities of the list of additives for processing in accordance with § 11 of the German Drinking Water Regulation apply. For correct application of the calculation method and for the plausibility check of the calculation results the following data regarding water quality shall be determined by analysis methods (preferably standardized) in accordance with the German Drinking Water Regulation and made available in a quality assured manner: - the pH value of the water to be examined at measurement temperature; - the measurement temperature of the water, in °C; - the evaluation temperature of the water which the statement of the method is referred to, in °C; - acid capacity up to pH 4,3 in mmol/l with titration temperature; - alkalinity or acid capacity up to pH 8,2 in mmol/l with titration temperature; - molar concentrations in mmol/l or mass concentrations in mg/l of the following substances: - calcium, magnesium, sodium, potassium, - chloride, nitrate, orthophosphate, sulphate. The method for the determination of the calcite dissolution capacity described here is often additionally used outside the actual scope for calculation of raw waters. Here a plausibility check is recommended, in particular for acid waters. The following modifications have been made with respect to DIN 38404-10:1995-04: a) the title has been amended; b) the calculation method of this standard replaces method 3 of DIN 38404-10:1995-04 with innovations in the following areas: - scope, - plausibility check, - reaction rate constants, - activity coefficients, - requirements for calculation programmes, - accuracy requirements for results, - addition of new example datasets for testing the absolute accuracy, - test scheme for testing the relative accuracy; c) method DIN 38404 - C 10 - R 1 (Determination of calcite saturation of water by calculation of the saturation pH value after exchange of carbon dioxide) has been deleted; d) method DIN 38404 - C 10 - R 2 (Determination of calcite saturation by calculation of the saturation pH value according to Strohecker and Langelier) has been deleted; e) method DIN 38404 - C10 - M 4 (Determination of the calcite saturation by adsorbate) has been deleted; f) method DIN 38404 - C 10 - S 5 (Determination of the calcite saturation by pH rapid test) has been deleted. This document has been prepared by NA 119-01-03-01-22 AK "Calcitsättigung" ("Calcite saturation") of NA 119-01-03 AA "Wasseruntersuchung" ("Water Analysis") at the Water Practice Standards Committee (NAW) and the DVGW Deutscher Verein des Gas- und Wasserfachs e. V. (German Technical and Scientific Association for Gas and Water).