ENDRESS+HAUSER  CA80NO-AAG21C101

Integrated controller with up to 2 measuring channels and digital Memosens technology

Application

• Monitoring of nitrite in drinking water
• Quality control of raw water for the food industry
• Monitoring of nitrite in mineral water batch processes

Your benefits

• Easy upgrade to measuring station by connecting with up to four Memosens sensors
• Automatic calibration and cleaning
• Cooled version for longer reagent shelf life
• Digital communication for remote access
• Two-channel device available
• Digital fieldbuses (Profibus DP, Modbus TCP, Modbus RS485 and Ethernet IP) and web server

Colorimetric measuring principle

After application-specific sample preparation, some of the permeate is pumped into the mixing/ reaction chamber. The specific color reagent is metered exactly in a defined mixture ratio. The chemical reaction causes the characteristic change in the color of the sample. The multispectral photometer measures the level of absorption by the sample or the stain solution at defined wavelengths. The analyzed wavelengths, and their relationships to one another, are parameter- specific.

Based on proportionality the amount of light absorption is a direct indicator of the concentration of the parameter under analysis in the sample. To compensate for any interference influences resulting from turbidity and fouling, as well as from the deterioration and aging of the LEDs, a reference measurement is performed before the actual measurement. This reference signal is subtracted from the measuring signal. The temperature in the photometer is kept constant to ensure a reproducible reaction that takes place with a short period of time.

Nitrite

Nitrite is an intermediate stage of the bacterial oxidation of proteins and urea to ammonium and nitrite, and ultimately to nitrate.

Therefore nitrite in the WWTP outlet or drainage canal is an indicator of incomplete nitrification. Nitrites are often used as a corrosion inhibitor in process water and cooling water. The food industry uses nitrite as a preservative (e.g. curing salt). Nitrite rarely occurs in surface water as it is easily oxidized to nitrate in the air. Therefore, online nitrite measurement is particularly performed in areas with reduced oxygen content, such as well water and areas with low flow. Due to its toxicity, no nitrite is permitted in drinking water. (For example, the limit at the water treatment outlet is 0.1 mg/l (0.1 ppm) according to the 2011 German Drinking Water Regulation). Nitrite causes the conversion of hemoglobin to methemoglobin, which decreases the ability of the blood to carry oxygen ("internal asphyxia").