The APA 6000 High Range Hardness analyzer is well suited for measurements in both raw and finished waters. It is free of heavy metal and carbonate interferences and covers a wide range of concentrations. Two sample streams can be connected to one instrument, allowing the end-user to collect hardness information on both the raw and finished waters. Combined with its networking capabilities, the High-Range Hardness APA 6000 is ideal for the monitoring of water softening processes, cooling water in power plants and raw water and final effluent from drinking water facilities.
Raw Water Specifics:
In addition to variable levels of hardness, many raw waters also contain heavy metals that interfere even at trace levels. Even though heavy metals contribute to the total hardness and therefore should be measured, they cause problems because they also interfere with the indicator dye. The High-Range Hardness APA 6000 uses a masking agent (Magnesium-CDTA reagent) prior to the titration step. Under the proper reaction conditions, the CDTA chelant removes all bound heavy metals from the indicator that were present in the sample, exchanging one magnesium for each bound heavy metal. This allows the heavy metals to contribute to the total hardness measurement due to the additional magnesium added (calcium, magnesium, heavy metals) without interfering with the measurement value.
Many ground waters also contain high levels of carbonate alkalinity. An acid digestion is performed in the High-Range Hardness APA 6000 prior to the titration step to remove carbonates in the sample that would precipitate with hardness at the pH of the titration. After digestion, the strong buffering capacity of the reagents brings the sample to the proper pH for the titration.