Determination of water turbidity
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Is it necessary to deduct the blank value when measuring the turbidity of ultrafiltration or reverse osmosis effluent? When using the Hach 2100 to measure samples, the blank value is not deducted from the readings, but domestic turbidimeters deduct the blank value for each measurement, which results in differences between the readings obtained by these two instruments. At low concentrations, the difference corresponds exactly to the blank value: the Hach instrument gives a reading of 0.3 NTU, while the domestic instrument reads 0.2 NTU, with a blank value of 0.1 NTU.
Whether it is necessary to deduct the blank value when measuring water turbidity depends on the instrument’s instructions and the testing method. Turbidimeters of different brands and models may have different calibration and measurement procedures. If the instructions for domestic turbidity meters recommend deducting the blank value during measurement, whereas the Hashi 2100 does not require this, then the deviation in results you mentioned will occur. To maintain data consistency and comparability, it is recommended to choose a single measurement method and conduct the measurements in accordance with its requirements. If it is necessary to compare the data from these two instruments, they can be calibrated through experimental design so that the results can be compared on an equal basis. When determining low concentrations, measurement errors due to the blank value can indeed occur. In such cases, regular calibration and quality control procedures should be employed to ensure the accuracy and reliability of the data. If necessary, the measurement results can be corrected to obtain consistent results when using different devices. .