Backwashing Procedures And Precautions For Multi-media Filters

 Multi-media filter backwashing procedures and precautions
 I. Standard Backwashing Procedure
 Shutdown of filtration

Close the inlet and outlet valves, open the vent valve to release the pressure inside the tank, and stop normal water production.
 air scrubbing

Open the air inlet valve and introduce compressed air to agitate the filter media, peel off the attached mud, sand and colloidal impurities, and scrub for 3-5 minutes.
 Combined air-water backwash

Maintain air supply and simultaneously open the backwash inlet valve. The water flows from bottom to top in a counter-current flushing manner, causing the filter layer to expand by 40% to 50% and carrying away most of the dirt. This process takes 4 to 6 minutes.
 Separate water backwash

Close the air intake valve and continuously backwash with clean water to thoroughly remove loose impurities until the drain water becomes clear.
 Filter media sedimentation

Close the backwash inlet valve and let it stand for 2-3 minutes to allow the multi-layer filter media to naturally reposition themselves according to density, preventing layer mixing.
Forward washing drainage

Open the inlet valve to let water flow from top to bottom, and open the drain valve for a forward wash. The water should be clear and meet the standards.
 Restore operation
 Close the drain valve, switch to normal filtration mode, and start continuous water production.
II. Precautions for backwashing
 Control the triggering conditions

When the differential pressure rises to 0.05~0.1MPa, or reaches the set cycle, backwash in time and do not exceed the time limit.
 Control backwash intensity

The intensity of air washing and water washing must be strictly performed according to the parameters. If the intensity is too high, it will disrupt the filter media layers; if it is too low, it will not be able to wash away impurities.
 It is strictly forbidden to start or stop valves under pressure.

Depressurize before opening and closing the valves to avoid water pressure impact damaging the tank and pipeline fittings.
 Observe the drainage status

The backwash is considered clean only when the turbidity of the drainage gradually decreases; if the drainage is black and turbid and does not disperse, the rinsing time needs to be extended.
 Prevent filter media from being mixed and lost

During the settling stage, water should not be introduced to disturb the water. If particulate filter media is found in the effluent, the water distribution cap and the support layer should be checked immediately.
Record running data
Record the duration, pressure difference, and water quality changes for each backwash, and flexibly adjust the backwash interval according to the influent water quality.
 Regular inspection and maintenance

Frequent backwashing over a long period can reduce the effectiveness of the filter media. It is important to promptly check for issues such as filter media caking, wear and tear, and pipe blockage, and replace the filter media as needed.
Safe Operation

Operate the valves slowly to avoid water hammer, and pay attention to whether there are any leaks or abnormal noises in the tank during inspections.