I. Core Parameters for Standard Backwashing of Quartz Sand Filters
Inadequate backwashing parameters can lead to incomplete rinsing, filter media loss, and energy waste. There are clear industry standards for the pressure and time parameters of different backwashing modes, which are also the core basis for the daily commissioning of quartz sand filters.
1. Backwashing Pressure Parameters: The standard pressure for conventional single-water backwashing is controlled at 0.15–0.25 MPa. This pressure allows the quartz sand filter layer to fully expand and loosen trapped impurities. During combined air-water backwashing, the air pressure should be stabilized at 0.05–0.08 MPa. Low-pressure aeration can break up caking filter media and prevent high-pressure aeration from washing it away. In daily operation and maintenance, the optimal time to start backwashing is when the pressure difference between the inlet and outlet of the equipment reaches 0.05–0.1 MPa.
Quartz Sand Filter
2. Backwashing Time Parameters: For ordinary water quality, the single-water backwashing time is 5-10 minutes; the combined air-water backwashing is suitable for highly polluted water quality, with a total time of 8-15 minutes. The standard commissioning time is 3 minutes of air washing, 6 minutes of mixed air-water washing, and 3 minutes of clean water rinsing. If the raw water has high turbidity and many impurities, the time can be extended by 1-3 minutes, ensuring the drain water is clear and free of turbidity. Avoid prolonged rinsing as this can damage the filter media.
II. Detailed Parameter Commissioning Steps
Step 1: Stop the machine and wait for it to start. Close the original inlet and outlet valves of the equipment, open the exhaust valve and drain valve to empty the water in the tank, preventing water accumulation from affecting the rinsing effect. Step 2: Adjust the pressure. Slowly open the backwash inlet valve, observe the pressure gauge, and gradually adjust to the standard pressure range. Sudden pressure increases that could impact the filter layer are strictly prohibited. Step 3: Set the rinsing time. Set the corresponding time according to the on-site water quality. For automatic equipment, the parameters can be locked directly in the PLC system; for manual equipment, strict timing is required. Step 4: Final Forward Wash. After backwashing, switch back to forward wash mode and flush for 3-5 minutes until the effluent is clear and the pressure differential returns to normal. Then, resume normal filtration operation.
III. Real-world Commissioning and Retrofit Case Study
A chemical production company in Xi'an had two quartz sand filters in its water treatment system. These filters had long suffered from incomplete flushing, cloudy effluent, and frequent filter clogging, severely impacting the lifespan of the downstream reverse osmosis equipment. After on-site inspection by Dean Water Treatment technicians, it was found that the equipment had incorrect parameter settings, including insufficient backwash pressure and excessively short flushing time, and that the equipment had not been adjusted according to water quality conditions.
Our on-site parameter readjustment: The single-water backwash pressure was stabilized at 0.22 MPa. For the high-turbidity raw water in the plant, the total backwash time for the combined air and water process was adjusted to 14 minutes. Simultaneously, the pressure differential was set to 0.08 MPa to automatically initiate the backwash program. After parameter optimization and debugging, the equipment filter layer is thoroughly flushed of impurities, and no more caking occurs. The turbidity of the effluent is stable and meets the standards. The replacement cycle of back-end consumables is extended by 60%, which greatly reduces the company's operation and maintenance costs and significantly improves the stability of equipment operation.
