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
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.