Different filter media have significantly different strength tolerances, and the backwashing time cannot be directly determined using universal parameters. Quartz sand and anthracite, with their relatively high hardness, can withstand backwashing operations of 8 to 15 minutes. This duration is sufficient to remove deep-seated silt. (Click to learn more about the appropriate backwashing pressure for quartz sand filters.) However, activated carbon is more brittle, and the backwashing time must be strictly controlled within the range of 5 to 8 minutes. Exceeding this time can easily cause breakage, leading to powder clogging the effluent filter screen.
Last year, a factory set its activated carbon tank backwashing time to 12 minutes. After only half a month, the effluent consisted entirely of black carbon powder, indicating a 30% loss of filter media. (Click to view: Signs of impending filter media failure and replacement timing in well water filtration equipment) After changing the backwash time to 7 minutes, the filter media loss decreased to less than 3%, and the water quality returned to normal. Therefore, the first step in any related operation is to clearly identify what kind of filter media is inside the tank.
Quartz Sand Filter
Water Quality Change Cycles Must Be Adjusted
Simply relying on fixed flushing times is insufficient. Well water quality varies significantly between the rainy and dry seasons. When the daily turbidity is below 5 NTU, it is recommended to flush every 12 to 24 hours; when the turbidity is between 5 and 20 NTU, the flushing interval should be shortened to 8 to 12 hours; if the turbidity exceeds 20 NTU, such as in the case of muddy water during the flood season, the flushing frequency must be increased to 4 to 6 hours. Remember this ironclad rule: when the water becomes turbid, it's better to flush more frequently than to worry about the water bill. The losses from a single blockage are far more severe than ten additional flushes.
Pressure differential is the true signal to initiate backwashing.
Simply relying on time is unreliable. When water quality suddenly deteriorates, the filter bed may still be dirty even after the allotted time has passed. The most crucial indicator is the inlet and outlet pressure differential. When the pressure differential reaches 0.08 to 0.1 MPa, it indicates that the filter bed is completely clogged with sediment and backwashing must begin immediately. After flushing, the pressure differential will drop back to 0.01 to 0.02 MPa, indicating that backwashing is complete. One aquaculture customer previously used a fixed 10-minute interval and never checked the pressure differential, resulting in severely clogged filter cartridges and poor water output. After installing a pressure differential gauge, the problem was completely resolved.
Turbidity of Backwash Determines When to Stop
Many people are unaware that backwashing isn't simply about stopping the machine after a set time. The most accurate way to stop is by checking the turbidity of the backwash. In the first minute or two of backwashing, the water will inevitably be yellowish and turbid, which is normal. Continue flushing until the turbidity drops below 5 NTU and remains clear for one or two minutes. At this point, you can stop. This method is more effective than blindly applying any general parameters because it's based on the actual level of contamination, preventing both over- and under-flushing.
Activated Carbon Filter
Four Steps for Practical Operation
Step 1: Determine the basic flushing time based on the filter media. Quartz sand requires 8 to 15 minutes, while activated carbon requires 5 to 8 minutes. Step 2: Adjust the flushing cycle according to the daily turbidity; flush less when the water is clear and more frequently when the water is turbid. The third step is to trigger backwashing when the pressure difference reaches 0.08 MPa; this is the primary criterion. The fourth step is to stop backwashing when the drainage becomes clear. It's crucial not to rigidly adhere to a fixed timeframe. This process has been repeatedly verified through hundreds of trials at DIEN Water Treatment, effectively extending the filter media's lifespan and ensuring effluent quality.
Regular maintenance is essential for long-term stability.
After installation, the equipment is not yet ready for use. It's recommended to check the pressure gauge reading monthly and observe the turbidity trend of the drainage every three months. If the backwashing time becomes increasingly longer to achieve clear drainage, it indicates that the filter media may be aging or caked, requiring partial replacement. Furthermore, high iron and manganese content in the well water can cause film formation on the filter media surface, reducing the washing effect. At times like these, it's necessary to increase the frequency of chemical cleaning. For example, soaking in a citric acid solution every six and a half months is recommended. Only by dynamically adjusting the parameters can the equipment achieve stable operation over a long period.
Do you think that when performing backwashing, relying on "time tracking" or "pressure differential tracking" is more reliable? We sincerely welcome you to share your experiences in the comments section. Don't forget to like and save this post so that more colleagues can see it!
