Figure 2: Diurnal variation of Ammonium/Nitrate |
However, in December of that year, the automatic ammonium analyser was subject to failure and could not be relied upon to provide accurate data for this period. As a solution, the ammonium values of the ion-selective probe were used for control and regulation purposes from that time, indicating the superior reliability, durability and accuracy of this technology. Depending on the requirements for absolute accuracy, a regular check with laboratory reference values is useful in order to comply with quality standards related to process management and sensor technology. Overall, costs associated with the maintenance and calibration of the ion-selective probe technology were low.
The probes were routinely subjected to a maintenance check, however as a result of the integrated and automatic compressed-air cleaning function, no additional manual cleaning or maintenance was necessary. Occasionally measured values were validated using comparative measurements in the laboratory, with minimal deviations recorded and no additional calibration necessary. The ammonium and the nitrate electrode were recalibrated for the first time after approximately three months of use.
After a six month trial comparison, results compiled by the wastewater treatment plant at Strass indicate that the latest ion-selective probe technology provides data quality consistent with the automatic analyzer. The overall results of the comparison suggest that ion-selective probe technology offers a cost effective alternative for smaller wastewater treatment plants, while still providing a high level of reliability and data quality.
Author's note: Dr. Klaus Reithmayer is product manager and Robert Hengel is wastewater market leader at WTW, a Xylem brand. For more information email: [email protected] and [email protected].
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