Research On The COD Systemby Ultraviolet Absorption Method

Environmental issues have always been the focus of social attention,and the pollution of water resources has also received more and more attention.As a non-renewable resource,water resources have always faced enormous problems in the context of rapid industrial economic development and expanding population.In recent years,China’s industrial,agricultural sewage and domestic wastewater have been polluted,and untreated wastewater has threatened the entire ecological structure and human health while polluting the water environment.Water quality testing technology is a technology for judging the degree of water pollution by testing physical,chemical and biological indicators of water,Chemical oxygen demand(COD)is one of the indicators.The chemical oxygen demand index is usually a parameter for judging the organic matter content in the water sample.The higher the organic matter content,the more serious the water sample is contaminated.The common chemical oxygen demand detection method is that the potassium dichromate method belongs to a chemical detection method.Although the measurement result is accurate,the labor and time cost are high,and the chemical reagent used is easy to cause secondary pollution to the environment.This paper introduces the common detection methods of chemical oxygen demand and the development status at home and abroad,and then focuses on the COD detection method and UV absorption method used in this paper.By introducing the principle of ultraviolet absorption method,the effect of reducing the turbidity parameters such as suspended solids on COD detection by using dual-wavelength detection technology is proposed.In this paper,a non-orthogonal double grating structure based on Czerny-Turner is designed as an optical system.The optical signal is stably converted and amplified by the design of the photoelectric conversion circuit,the amplification circuit,and the filter circuit.The embedded system with the STM32F103 microcontroller as the core completes the collection and processing of electrical signals,and finally displays and stores the COD values.Finally,COD and turbidity standard solution are configured to draw the COD detection standard curve and fit the equation,COD measurements excluding turbidity interference can be calculated by measuring absorbance values at 254nm and 546nm,the effects of chloride ion and temperature on COD detection were also analyzed.Through the measurement of standard water samples and actual water samples,the average measurement error of the system is 4.58%and 9.8%and has good repeatability.It shows that the detection system can realize on-line real-time detection of COD concentration between 0～1000mg/L,which is suitable for the emission detection of wastewater from factories and textile mills.