A filter unit using silica sand was optimized to clean handwashing wastewater by removing dirt and particles. By adjusting the size of the sand particles, the depth of the filter, and the flow rate, the filter was able to remove around 60% of the dirt and particles. The best results were achieved with 0.6 mm sand particles, a 12 cm filter depth, and a flow rate of 0.3 L/min. Even though the water still had some dirt in it after filtering, this process is an important step in making the water cleaner for further treatment.