The Potential of Sand - Polonite Filters for Reducing Total Phosphorus Concentration in Subsurface Horizontal Flow Constructed Wetlands

Abstract The European Union is implementing stricter regulations for phosphorus management in wastewater treatment, recognizing phosphorus as a key factor in eutrophication and water pollution. This study evaluates the efficiency of Sand-Polonite mixtures in constructed wetlands for phosphorus removal, aiming to support improved treatment processes in light of these regulatory changes. Eight filter models with varying Polonite content were tested under laboratory conditions, analyzing their performance in reducing total phosphorus concentration. The results showed that all Sand-Polonite mixtures achieved an average phosphorus reduction efficiency exceeding 90%. The highest efficiency (99.9%) was observed in a mixture with 70% Polonite content. Statistical analyses, including the Wilcoxon signed-rank test (p = 0.0039) and Kruskal-Wallis test, confirmed significant phosphorus reduction across mixtures, particularly between those with lower and higher Polonite content. Spearman’s correlation analysis indicated a strong relationship (r = 0.85) between Polonite content and phosphorus removal efficiency. However, chemical clogging, likely due to CaCO 3 formation, was observed, affecting hydraulic performance. While Sand-Polonite mixtures demonstrated high efficiency, their use in large-scale constructed wetlands may incur higher material costs, necessitating careful economic evaluation.