Research on Water Quality Chemical Oxygen Demand Detection Using Laser-Induced Fluorescence Image Processing

Area of Science:

• Environmental Science
• Analytical Chemistry
• Optical Engineering

Background:

• Chemical Oxygen Demand (COD) is a key indicator of organic water pollution.
• Accurate measurement of low-concentration COD is essential for effective water quality management.
• Existing methods may have limitations in sensitivity or real-time application.

Purpose of the Study:

• To develop and validate an innovative Laser-Induced Fluorescence (LIF) image processing technique for detecting low-concentration COD in aqueous environments.
• To design and build a miniaturized, non-contact COD detection system based on LIF image processing.
• To assess the system's performance in terms of sensitivity, stability, and accuracy.

Main Methods:

• Utilized ultraviolet laser excitation to induce fluorescence in organic compounds within water samples.
• Employed a CMOS image sensor to capture fluorescence image data.
• Applied image processing techniques, including color channel isolation and RGB characteristic analysis, to derive COD values.
• Developed a predictive model using Partial Least Squares Regression (PLSR) based on image features.

Main Results:

• Successfully developed an LIF image processing system for COD detection, comprising a CMOS sensor, STM32 microprocessor, laser, and display.
• Acquired fluorescence images from mixed solutions of sodium humate and glucose at varying concentrations.
• Achieved a detection relative error of less than 10% for COD concentrations within the 0-12 mg/L range.
• Demonstrated the system's capability to correlate RGB color characteristics with COD concentrations.

Conclusions:

• The developed LIF image processing system offers a highly sensitive, stable, and non-contact method for measuring low-concentration COD.
• The system is suitable for rapid, real-time online water quality monitoring.
• This innovative approach provides a promising alternative for environmental water pollution assessment.