it adopts the “gravity filtration + backwash regeneration” mode: Raw water enters from the top and flows downward through the filter layer composed of quartz sand with varying particle sizes at a flow rate of 5-10 m/h (fine sand in the upper layer traps small particles, while coarse sand in the lower layer provides support and traps large particles). Impurities such as sediment, algae, and suspended colloids in the water are adsorbed or mechanically trapped by the pores between sand grains. The clarified water is collected and discharged through the pebble bed at the bottom (which prevents sand loss). When the resistance of the filter layer increases and the effluent turbidity exceeds the standard, backwashing is performed by reverse water flow (or air-water mixture). The impact of water flow loosens the sand layer, and the trapped contaminants are discharged with wastewater, quickly restoring the filtering capacity. The backwash time usually only takes 5-10 minutes.