Field Equipment Calibration PH, Temperature, Conductivity, Turbidity, Dissolved Oxygen, Free & Total Chlorine Gregory Langland CCSF

Objective Understand Equipments and Supply Needed Ensure QA/QC is in place for data collection Testing various water samples -pH/Temp/Specific Conductance/Total Dissolved Solids (TDS) -Turbidity -Dissolved Oxygen - Total & Free Chlorine

Necessary Equipment & Supplies Turbidity -< NTU standards for 4 point calibration - Sample vial - Chlorine Standards A & B - DPD-Colormetric Determinant for Free and total Chlorine -TURBIDITY /Chlorine meter pH/temp/Electric Conductivity meter -pH Electrode Storage Solution -4.0 pH buffer -7.0 pH buffer pH buffer -Conductivity Standard -multiparameter probe and meter Dissolved Oxygen -Dissolved Oxygen/Meter Probe Extra batteries for the meters Extra Field data sheets Beaker/ sample Container Deionized water for cleaning probes, vials

pH/Temperature Calibration Probe must be submerged in the solution and allowed to stabilize Calibration Three point calibrations Use pH 7.0, pH 4 & pH 10 for three point depending on the anticipated sample pH. Slope should be % out side this range readings are not accurate pH is temperature dependent; most meters compensate for the temperature effect (not as strong an effect as for EC) Measure Temperature of stabilized buffers Buffers/standards pH measurements are only as accurate as the buffers used for calibration. Discard buffers after their expiration dates. Be careful not to contaminate stock solutions with used buffer, rinse water or with a different buffer.

Conductivity (EC) Calibration Probe must be submerged in the solution and allowed to stabilize Calibration Standards conductivity standards commonly used depend on the instrument example : mS/cm for Hanna Multiparameter probes A maximum of 20% error regardless of standard used is acceptable. Beyond 20%, readings are not accurate

Turbidity Calibration Sensor calibration Turbidity free water = zero (0 NTU) standard filtering either sample water or deionized water through a 0.2 um or smaller filter to remove particles or use deionized water that is degassed by sparging (bubbling) with helium to minimize air bubbles that give false turbidity readings

Turbidity Standards Formazin -Opacity of Formazin Standards ( 0, 2,10,40 80, 400 NTUs) : Higher opacity= higher turbidity Other Standards available that are more environmentally friendly ! Most Portable meters have their own Turbidity Standards (<0.1, 15, NTUs)

Turbidity Range & Calibration Standards range depends on anticipated sample values Drinking water - typically 0-20 NTU Lakes, streams and wetlands , 0-50 or NTU Wastewater; Storm water run off NTU; sometimes>1000 NTU, require dilution 2 standards typically adequate, but four point calibration is better (response is linear) Most commonly use ready made standards <0.1 NTU, 15 NTU, 100 NTU and 750 NTU.

Total & Free Chlorine-Colorimetric Calibration Calibrate the meter with Calibration solution provided with the meter. Most meters have specific calibration standards. Sample is initially read without addition of colorimetric solution For Total or free Chlorine specific colorimetric test reagent are added Field Meters have an interface that converts Absorbance recorded by instrument into ppm (part per million) or mg/L of Total or Free Chlorine Validated Range 0-5 ppm (instrument can read as low as 0.02 ppm)

Dissolved Oxygen-Sensor Probe Calibration Hanna Instrument The probe is under polarization with a fixed voltage of approximately 800 mV. Probe polarization is essential for stable measurements with the same recurring degree of accuracy. With the probe properly polarized, oxygen is continually "consumed" by passing through the sensitive diaphragm and dissolving in the electrolyte solution contained inside the probe. Calibration should be 100% in the air (at sea level) The Probe can measure Oxygen as % saturation in a solution or mg/ L without recalibration, by simply pressing RANGE function, The mg/L readings make it possible to read the concentration of the dissolved oxygen directly in ppm. Range: 0.00 to mg/L O2 /0.0 to 300 % O2

Dissolved Oxygen-Sensor Probe Salinity, Altitude Compensation Temperature is automatically compensated during the Probe sensor read out. Temperature has an impact on amount of dissolved O2. However, reading need to be adjusted manually for altitude and salinity that will affect DO reading. Adjustment charts are provided to compensate for change in altitude or salinity in reference to sea level. Salinity adjustment is required when measuring salt water. Altitude compensation is required if above sea level.

Stabilization Criteria for each parameter QA/QC Reading must be stabilized within certain range for each parameter calibrated and tested Stabilization Criteria for each parameter is required as part of QA/QC. Temperature +/- 0.2 deg C Conductivity <100 mS/cm +/- 5% >100 mS/cm +/-20% pH +/- 0.1 unit DO +/- 0.3 mg/L Turbidity +/- 10%