Electrode-Based Suspended Solids Detection

Suspended solids (SS) refer to solid particles that cannot pass through a filter and serve as a critical indicator of water quality. While the conventional gravimetric method is accurate, it is time-consuming and unsuitable for real-time monitoring. 

Electrode-based methods offer a rapid, continuous alternative by measuring changes in the electrical properties of water.

The core principle lies in how suspended particles alter the electrical characteristics of water. As particle concentration increases, the conductive pathways for ion migration become restricted, causing an increase in resistivity. In addition, suspended substances may adsorb onto the electrode surface to form a film, changing the electrochemical state of the electrode and thereby affecting the electrode potential. 

More advanced approaches employ electrochemical impedance spectroscopy (EIS), in which the impedance of the sample is measured at various electrode spacings. This moving-electrode configuration enables probing of a small section of the sample and is particularly advantageous for heterogeneous liquids such as suspensions.

The operational procedure generally involves three steps: calibration, measurement, and data processing. Calibration combines zero-point and span calibration using standard solutions of known concentrations. During measurement, the electrode is immersed in the water sample with care to avoid bubble attachment, and readings are recorded after stabilization. Since temperature significantly affects electrical parameters, electrodes equipped with built-in temperature sensors enable automatic compensation.

Key interferences include bubble adhesion, flow velocity fluctuations, and electrode fouling. Bubbles block electrical signal pathways, while excessive flow disturbs particle distribution and insufficient flow promotes sedimentation. Mitigation measures include self-cleaning mechanisms, controlled sampling flow rates, and regular electrode cleaning with soft brushes or specialized reagents. 

Because the electrical response varies with particle size and surface properties, the electrode method is best suited for long-term monitoring of water bodies with relatively stable composition, with periodic validation against the gravimetric method to ensure data reliability