Study and design on chemical oxygen demand measurement based on ultraviolet absorption

•Proposed an online UV absorption test method for COD, which used orthogonal double grating structure to reconstruct the optical detection system.•Used orthogonal double grating structure and designed an optical filter structure, the stray light in the incident light was eliminated.•Designed a more stable and reliable COD detection device and provided a guarantee for the monitoring of pollutants and traceability technology.

Chemical Oxygen Demand (COD) is an important parameter for the detection of organic pollutants in water. UV absorption detection method of COD is a simple physical method that can detect water samples online without secondary contamination from chemical reagent. In this paper, the detection of COD based on UV absorption method was studied. The UV absorption method was used to detect COD in water samples, and the COD online detection device was designed. Optical path and circuit design principle of the device were introduced to overcome the difficulties including weak signal and the output signal instability, and the size of the system was effectively reduced. Contrast experiments showed that the system performance and measurement results are reliable and can be used for accurate COD detection within its range (up to 1000 mg/L).