ENDRESS+HAUSER  CAS40D-AA1A1A1

Online measurement of nutrient parameters in municipal wastewater treatment plants

Ion-sensitive sensor for continuous measurement of ammonium, nitrate and other ions

The ion-sensitive sensor works directly in the activated sludge basin of municipal sewage treatment plants without any additional sample conditioning or sample transportation.

A complete measuring system consists of a sensor with electrodes and a transmitter with display and operating elements.

The sensor is used to monitor the ammonium and nitrate content

• in the activated sludge basin
• in the preclarification outlet.

• Reliable, cost-saving unit:
  • Direct measurement of ammonium or nitrate without costly sample conditioning
  • Optional potassium and/or chloride measurement, also to compensate high concentrations of interference ions
  • pH measurement as standard
  • Low operating costs since no reagent used
• Versatile and flexible: Large measuring range 0.1-1000 mg/l NH4-N or 0.1-1000 mg/l NO3-N
• Easy-to-use and safe:
  • Installed directly on the basin rim, no measuring container or sample-conveying pump required
  • Minimum maintenance thanks to compressed air cleaning
  • Long electrode service life, membrane cap must be replaced every 6 months approximately
  • Standardized digital communication enables Plug & Play

At the heart of the ion-selective electrode (ISE) is a membrane that is selective for the ion to be measured. An ionophore is integrated into the membrane which facilitates the selective "migration" of a specific type of ion (e.g. ammonium or nitrate) to the electrode. As a result of ion migration, a change in the charge occurs, causing the creation of a potential that is proportional to the ion concentration logarithm. The potential is measured against a reference electrode with a constant potential and converted to a concentration using the Nernst equation. With the potentiometric measuring principle, the color and turbidity do not affect the measurement result.