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Hach Company IntelliCAL™ Probes for Superior Measurement Performance for LDO ® Dissolved Oxygen Don F. Harrington, Robbin A. Crane, and Cary B. Jackson, Ph.D. • Hach Company • Loveland, Colorado INTRODUCTION Hach’s IntelliCAL LDO probes deliver a number of benefits, which help to en- sure the highest degree of accuracy. Some of these product features include: • Calibration Alerts • Automatic Probe Recognition • Automatic Prompts for Calibration Protocol • Automatic Storage of Calibration History • No Membranes • No electrodes to polish or maintain • No electrolyte solution to refill • Easy Stable Calibration • Superior Accuracy and Precision • No Polarization • Fast Measurement Readings • No Chemical Interferences • Compact and Field Portable The United States Environmental Protection Agency (USEPA) has recom- mended that each EPA Region grant interim approval of ASTM International Standard D 888-05 Standard Test Methods for the Measurement of Dissolved Oxygen in Water for measurement of DO in wastewater and in for use in mea- suring DO in methods approved at Title 40 of the Code of Federal Regula- tions Part 136.3 (40 CFR Part 136.3) for measuring Biological Oxygen De- mand (BOD5). EPA has reviewed the method and supporting validation data and determined that the method, includ- ing Test Method C (Luminescence-Based Sensor Procedure) meets all requirements for approval in compliance monitoring. In response, many EPA Regions and States have begun to authorize use of LDO in DO effluent monitoring as well as in BOD de- terminations. EPA RECOMMENDS LDO METHOD COMPARATIVE PERFORMANCE CONCLUSIONS: Accuracy and Precision Summary of Bias and Precision Method Reference Water POTW Wastewater % Biasavg %Precisionavg % Biasavg %Precisionavg Winkler 2.5 5.0 5.0 4.4 Membrane 2.5 3.8 3.3 2.9 LDO 0.0 2.5 0.0 2.5 Hach’s HQd Series of Meters and IntelliCAL Probes offer a superior solution for measuring dissolved oxygen for water quality assessments, compliance moni- toring, and for process control. LDO ® is first in accuracy LDO ® is first in precision LDO ® is the first choice in DO measurement A summary of validation results, including data collected from 12 participating wastewater facilities nationwide, from both influent to treatment and final ef- fluent samples are shown below. Each of the facilities performed independent accuracy and precision of DO, and BOD5 determinations. Measurements were performed in parallel with Winkler, Membrane Electrode, and LDO meth- ods. Below are charts demonstrating the comparative performance: R esults by Method Compared to Theoretical Dissolved Oxygen 1.50 2.50 3.50 4.50 5.50 6.50 7.50 8.50 9.50 10.50 1.50 3.50 5.50 7.50 9.50 Theoretical DO (mg/L) Method DO (mg/L) Theoretical Winkler Membrane Luminescence Linear (Theoretical) air - saturated w ater BOD 5 Demonstration Quality Control Acceptance Criteria for LDO IPR Range IPR Conc. 97.5% Lower 97.5% Upper 96% Upper (mg/L) Limit of Limit of Limit of Recovery(%) Recovery(%) Precision (%) Low 1.72 – 1.74 95.4 104 1.75 High 7.22 – 9.23 96.2 104 1.10 APPLICATIONS Hach’s HQd Series of Meters and IntelliCAL Probes, along with LDO Technol- ogy, offer the premier solution for your application needs, including: • Process control • Effluent discharge compliance monitoring • Biological Oxygen Demand compliance reporting • Biological nutrient removal • TMDL development in receiving water Dissolved oxygen (DO) concentration is one of the most important parameters monitored in surface water and wastewater. When used to access water qual- ity and derive the biological oxygen demand (BOD5), it becomes a regulatory compliance and process control tool. Thus, accuracy and precision for the de- termination of DO becomes critical for establishing and measuring water qual- ity criteria in surface water and wastewater facilities, as well as for calculating loading costs for industrial discharges to municipal wastewater treatment facili- ties. With the recent EPA recommendation for interim approval of ASTM D888-05: Method C – Luminescence Based Procedure, there are now three compliance methods for the measurement of DO. These are the Winkler Titration, Mem- brane Electrode (e.g., Clark Cell), and luminescence dissolved oxygen (e.g., LDO ® ). The Winkler Titration was first proposed in 1888 and the Patent for the Clark Cell was originally awarded in 1959. Hach launched its breakthrough LDO technology (Patent # 6,912,050) in early 2003 and has been delighting customers from various industries ever since. Hach’s new HQd series of meters and IntelliCAL™ probes offer a number of advantages for DO measurement over traditional compliance methods. Un- like Winkler and membrane electrode methods, LDO is free of chemical inter- ferences, maintenance free, and nearly unaffected by sample flow across the luminescence sensor. LDO also offers superior accuracy and precision com- pared to alternative methods. Hach’s IntelliCAL probes offer additional benefits beyond the LDO technolo- gy to further insure accuracy and to make the end users job easier. IntelliCAL probes store the calibration history, allowing easy change-over of probes with- out the need to recalibrate. Additionally, the IntelliCAL probes are automatically recognized by the meter, prompting the user through the appropriate Calibra- tion Protocol. How Does LDO Work LDO is a patented breakthrough technology that measures the quenching of a particular luminescent dye embedded in a hard plastic, oxygen permeable cap. The luminescent dye is excited by a flash of light from a blue LED. A de- tector positioned close to the sensor measures the emitted red luminescence. The higher the measured luminescence, the lower the oxygen concentration and vice versa.
