A Real-Time Water Quality Measurement Instrument for Simultaneously Detecting Turbidity and Particle Size by Using Single-Photon Counting Technique

A real-time water quality measurement instrument was developed to detect the liquid turbidity and particle size simultaneously. To reduce the complexity of the system and improve the sensitivity of the measurement, a high-precision single-photon detector is used to measure the intensity of scattered light. The system uses the principle of the 90° Mie scattering theory and the dynamic light scattering method to process the signal to obtain turbidity and particle size parameters. Combining the above theory with single-photon detection technique, a new instrumental measurement model, which can detect turbidity and particle size at the same time, is proposed. According to the experimental results, the system can simultaneously measure turbidity and particle size in the range of 1–100 Nephelometric Turbidity Units (NTU) and 50–400 nm, respectively. Turbidity and particle size showed a good linear relationship over the entire measurement range. In addition, in the actual measurement, the parameters of the instrument need to be adjusted and optimized when considering the interaction of turbidity and particle size. The system can simultaneously obtain the turbidity and particle size of liquid samples, shorten the detection time, and reduce the cost of measurement, which is sufficient for many applications, including the control and optimization of undissolved particles in chemical processes.