Characterization of Heavy Metal Contaminated Wastewater Using a Coaxial Sensor and Electromagnetic Wave Reflection Technique

Abstract

Industrial wastewater control is an important issue for protection of the environment. Liquid characterization using radio frequency signal is an interesting approach for selective detection of heavy metal contaminants in industrial wastewater. A simple sensor based on open-ended coaxial structure filled with the liquid under test is proposed. Liquid samples for the experiments are copper, zinc and nickel solutions with various concentrations of 1, 10, 100 and 1000 mg/liter each. From the measurement results using a vector network analyzer (VNA) in combination with the proposed sensor, the concentration of a specific contaminant can be determined by the magnitude of the measured reflection coefficient in a frequency range lower than 2 GHz. Applying a capacitive model of the sensor, complex permittivity of the liquid under test can be calculated from the measured reflection coefficient. Obvious relationship between the imaginary part of complex permittivity and the concentration of contaminant in a frequency range lower than 2 GHz was observed. The type of contaminants in the liquid samples can be identified by the position of the resonant peaks when the magnitude of reflection coefficient is plotted in the spectrum. The frequency range for contaminant’s identification lies between 2 and 3 GHz.

Microwave Sensors for In Situ Monitoring of Trace Metals in Polluted Water

“…Puangngernmak and Chalermwisutkul [ 94 ] are the only researchers who also experimented the detection of trace metals (Cu, Zn and Ni) in water with concentrations of 1, 10, 100 and 1000 mg/L using an open-ended coaxial structure and a VNA. They demonstrated the detection of these metals at frequencies lower than 2 GHz and the differentiation of these metals between 2 and 3 GHz.…”