The researchers tested a new way to filter wastewater from a treatment plant in Syria using a dual-layer rapid sand filter. They found that this method was effective in removing solid particles from the water, with a high efficiency in reducing turbidity, TSS, and COD levels. The filter, made of local sand and pistachio peels, showed better performance compared to traditional filtration methods. This new approach could be a cost-effective and efficient solution for treating wastewater in treatment stations using natural oxidization ponds.