Insights into pH dynamics, dissolved oxygen variability, and ion removal efficiency in floating treatment wetland

Abstract

This paper aims to analyse the dynamic responses within FTW constructed on the riverbank, focusing on pH, dissolved oxygen (DO), and the dynamics of calcium and magnesium concentrations. While some research has been carried out on Ca and Mg behavior in constructed wetlands no papers specifically addressed the removal mechanisms of these ions in FTWs have been found. Results showed that both polluted and treated water exhibited characteristics consistent with a mildly alkaline environment. Extremely low DO levels in cells with floating islands were increased after water passing through cell with algae. Ca removal efficiency in cells with floating island cells ranged from 2% to 6%, while the cell with algae achieved 23% to 49% efficiency. Modest Mg removal (1-6%) could indicate potential challenges in Mg removal processes within the FTWs. The analysis of plant responses to polluted water exposure reveals species-specific variations in Ca and Mg concentrations in shoots and roots. Ca concentration in algae tissue increased over time contrasting the marked decrease of Mg content. The study also revealed a gradual decrease of Ca and Mg concentration in stone wool corresponding to exposure duration. This research contributes to a better understanding of the complex dynamics of water treatment in FTWs, emphasizing the need for continued investigation into ion removal mechanisms, plant responses to increased Ca and Mg concentrations, and the role of algae in these biological systems.