Effectiveness of the resistivity method for non-destructive detection of organic and inorganic substrate clogging in treatment wetlands

Abstract

The detection of substrate clogging is crucial for the sustainable operation of treatment wetlands. Electrical resistivity methods have shown promise for non-destructive detection of clogging, but their effectiveness in identifying different types of clogging has not been identified. This study explores the feasibility of using the resistivity method to detect organic-dominated, inorganic-dominated, and combined organic-inorganic clogging during the drainage phase of vertical flow treatment wetlands. Results reveal that the amount of clogging matter accumulation and the corresponding hydraulic resistance follow the order: combined organic-inorganic > organic-dominated > inorganic-dominated clogging. Organic clogging matter generates greater hydraulic resistance than inorganic matter for the same mass, whereas hydraulic resistance does not correlate consistently with the water flow regime. The study establishes a direct link between the hydraulic effects of different types clogging matters and their corresponding conductivity. Linear regression analysis shows moderate positive correlations for total solids (R² = 0.56) and a stronger positive relationship for volatile solids (R² = 0.81) with conductivity. Additionally, conductivity is negatively correlated with substrate permeability (R² = 0.93). The conductivity of the wetland substrate under drained conditions is influenced by its water retention capacity, which is closely related to the hydraulic resistance of the clogging matter. This study introduces a non-destructive method to identify both organic and inorganic clogging and assess their impact on substrate hydraulic permeability. The application of this method enables real-time, non-invasive assessment of substrate clogging distribution and severity in wetland systems, enhancing the ability to effectively monitor and maintain wetland performance.