Determination Of Nitrogen and Phosphorus Removal Performance of Sand, Rice Husk And Zeolite Mixture

Growing population, urbanization, and agricultural activities are causing an increase in nitrogen and phosphorus loads in water resources, leading to eutrophication and water quality issues. In this study, the nitrogen and phosphorus removal performance of a mixture of sand, rice husks, and zeolite—which could be used as an alternative filter material in constructed wetland systems—from synthetic wastewater was investigated using laboratory-scale column experiments. The filter material mixture, prepared in equal volumes, was placed in columns; synthetic wastewater containing nitrogen and phosphorus, prepared at different concentrations (50 to 100 mg L-1) under laboratory conditions, was applied at different flow rates (1 and 2.3 mL min-1). Throughout the experiments, samples were collected at different retention times (3, 6, 12, 24, and 48 hours), and analyses of pH, electrical conductivity (EC), total nitrogen (TN), and total phosphorus (TP) were performed. The obtained pH (8.07–9.52) and EC (470.4–1284 µS cm-1) values were found to be compliant with relevant discharge standards. The highest phosphorus removal efficiency (99%) was achieved at a concentration of 50 mg L-1 and a flow rate of 1 mL min-1, resulting in an effluent concentration of 0.50 mg L-1, while the lowest removal efficiency (62%) was observed at a concentration of 100 mg L-1 and a flow rate of 2.3 mL min-1, resulting in an effluent concentration of 38.0 mg L-1. For nitrogen removal, the highest performance (90.1%) was achieved at a concentration of 100 mg L-1 and a flow rate of 2.3 mL min-1, resulting in an effluent concentration of 9.99 mg L-1, while the lowest removal performance (4%) was measured at a flow rate of 1 mL min-1, resulting in an effluent concentration of 68.34 mg L-1. In conclusion, the study demonstrated that the mixture of sand, rice husks, and zeolite provides high efficiency in nitrogen and phosphorus removal and can be used as a sustainable, low-cost, and environmentally friendly alternative filter material in constructed wetland systems. However, it was determined that increasing concentration and retention time did not produce the expected positive effect, particularly in phosphorus removal. Furthermore, it was found that low flow rates and appropriate pH conditions enhance adsorption efficiency, and it was assessed that pH optimization is necessary, particularly in wastewater with high pH values. It is believed that the findings obtained at the laboratory scale will make significant contributions to the applicability of natural filter materials for nutrient removal in constructed wetland technologies if supported by long-term and pilot-scale studies.