The potential of sand–Polonite filters for reducing total phosphorus concentration in subsurface horizontal flow constructed wetlands

The aim of this research is to develop an effective sand-Polonite filter mixture for individual treatment plants to reduce the total phosphorus concentration in wastewater. Polonite (trade mark Polonite®) is a commercial product used in filter systems for on-site wastewater treatment systems. The hypothesis is that the appropriate proportions of sand and Polonite (in the filter mixture will effectively reduce the total phosphorus concentration in wastewater. In the study, nine different sand-Polonite mixtures with various material proportions were developed. A phosphorus-containing solution (Cₚtot ~17 mg/L) was prepared to assess the effectiveness of these mixtures in reducing total phosphorus concentration by filtering the water through them. Total phosphorus concentrations were measured using a spectrophotometer before and after filtration. Based on laboratory trials, the use of a sand-Polonite mixture for reducing total phosphorus in subsurface flow constructed wetlands shows the good potential. The mixtures with varying proportions of sand and Polonite demonstrated effective phosphorus removal, achieving reduction efficiencies greater than 90%. In mixtures with low (10–30%) Polonite content, the influencing factor on phosphorus reduction efficiency was the retention time: the longer the phosphorus-containing solution remained in the filter, the greater the reduction in total phosphorus concentration. In mixtures with moderate (40–60%) Polonite content, the key factor for phosphorus reduction efficiency was the proportion of Polonite in the mixture. Employing sand-polonite materials in constructed wetlands can mitigate seasonal variations in wastewater treatment efficiency, particularly by enhancing phosphorus reduction during non-vegetative periods. To ensure optimal performance, it is crucial to maintain continuous water flow to prevent chemical clogging, and it is recommended to separate the mixture from fine particles (smaller than 2 mm). This research highlights the potential of sand-Polonite mixtures as a viable method for enhancing phosphorus removal in wastewater treatment systems.