In practice, discharge thresholds for Total Residual Chlorine (TRC) in effluent in Canada are becoming more stringent. Although the federal limit of 0.02 mg/ L has been the same for many years, some provinces are introducing measures that require more precision and lower limits of detection. For example, some Environmental Compliance Authorizations (ECA) in Ontario require the measurement method be accurate within 0.006 mg/L. Some plants also run more aggressive targets than are required by the applicable legislation. Colorimetric (aka DPD) analyzers and amperometric (aka “reagentless”) analyzers are not able to detect below about 20 mg/L so are not suitable for verifying low levels of residual chlorine needed to achieve these targets. Fortunately, with the iodometric electrode measurement method used in the Thermo Scientific Orion 7070iX TRO (Total Residual Oxidant) analyzer, measurements down to 0.001 mg/L even in dirty samples are achievable.
How to verify the absence of Chlorine – Dechlorination Applications
EPA-approved and a successor to the Orion 1770 analyzer, the 7070iX’s measurement method and ISE (Ion Selective Electrode) electrode technology have been proven in the field for decades. Several independent studies have validated the ability of this method, specifically using the Orion electrode, to measure down to 0.001 mg/ L. Such low-level sensitivity makes it ideal for dechlorination applications where the measurement used for regulatory reporting purposes could be described as verifying the absence of chlorine.
Save On Reagent
For regulatory compliance purposes, the 7070iX allows plants to operate in interval mode whereby measurements are taken at defined intervals – 10, 20, 30 minutes or up to 2 hours. Typically, this is sufficient for reporting purposes and provides significant savings on reagent use over continuous measurement. To further save on reagent, the analyzer will operate ‘on-demand’ whereby if no sample is present, it will switch into standby mode and output 3 mA to indicate this state. In addition, since there is only one reagent and the analyzer is fully automated, the opportunity for operator error is low. Watch video
Safe Discharge of Effluent Back into Natural Bodies of Water
The 7070iX is not limited to measuring residual chlorine and will detect other oxidants such as bromine and ozone with the same sensitivity. Moreover, the Orion 7070iX TRO is a robust solution for the low-level measurement of common oxidants used for disinfection to ensure safe discharge of effluent into natural bodies of water.
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