UV Vis Spectrophotometric Sensors

The objective of this document is to provide guidance on proper selection, commissioning, maintenance, operation, and application of sensors based on spectrophotometry for process monitoring of wastewater treatment. Many important substances in wastewater, including nitrate, nitrite, and organic carbon parameters, can be measured based on absorption of UV and visible light (UV-Vis). This document covers measuring principles, design, and operation of UV-Vis sensors which are part of the YSI IQ SensorNet process monitoring system. The concepts presented are also applicable to other major brands although the design and operation of the sensors is specific to each brand. 


  1. Wastewater treatment monitoring – nitrification and denitrification
  2. Spectrophotometry for wastewater
  3. Carbon sum parameters
  4. Nitrogen parameters
  5. Design, operation, maintenance, calibration and cleaning of UV-Vis spectrophotometric sensors
  6. Applications for monitoring carbon and nitrogen

Carbon parameters can be detected quickly and directly without the use of reagents by measuring the penetration of ultraviolet (UV) light through a sample using the principle of UV spectrophotometry. UV Vis spectrophotometric sensors built into probes which are immersed directly in the wastewater provide a continuous and direct online measurement of carbon parameters, nitrate and nitrite without the need for costly reagents.

Continuous monitoring helps operators to avoid conditions that upset the process. Learn more about UV Vis Spectrophotometry in this white paper. Download for free now!

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