Bringing the Spectral Measurement to the Lab – Optical Reagent-free Measurement of COD, Nitrate and Nitrite

Spectral Measurement  in Wastewater Treatment Plants
Determination of COD, Nitrate and Nitrite and keeping their values within the legal limits is day to day business of all wastewater treatment plants. Although wet chemistry analysers are still employed for this purpose, state-of-the-art are online spectral sensors that can continuously measure COD, nitrate and nitrite by measuring the spectral absorbance, typically at UV( 200–390 nm) or UV-VIS (200–702 nm) wavelength ranges. The measured spectrum is analysed and the concentration of the respective substances is calculated by complex algorithms stored on the sensor. The measured value is displayed directly.

Laboratory Verification: Now by Spectral Measurement, too
For documentation and self-monitoring purposes, the values measured with any online sensor are regularly verified in the lab using photometrical standard test kits. However, GLP-compliant work with cuvette tests requires at least a double, preferably a triple determination and a control standard, thus becoming an important cost factor. Further, the use of potassium dichromate and mercury sulphate involves health, environmental and disposal issues.

WTW have now successfully implemented the proven spectral measurement principle in the new photoLab® 7600 UV-VIS spectrophotometer, thus allowing to measure COD, nitrate and nitrite of effluent water without the need for any photometric reagent.

Performing an OptRF measurement is menu-guided and very simple:

• Take a sample from the effluent
• Pipet the sample into a 10mm quartz cuvette
• Start the 'OptRF Measurement' from the menu
• The values are displayed directly.

Conclusion
Even though photometric test sets will remain indispensable for referencing and self-control, OptRF lends itself as a fast and cost-free option for quick daily monitoring, sample verification and preliminary tests of the expected measuring range.

Trade in your old photometer for a new WTW photoLab® 7600 UV-VIS
Save money and time with the revolutionary spectrophotometer offering Optical Reagent-Free (OptRF) measurement for COD, Nitrate and Nitrite and benefit from WTW’s 70 year offer: upgrade your old model of any make with a 900 Euros discount to photoLab® 7600 UV-VIS, just proofing your ownership. Ask your WTW dealer.