At Glacier Filtration, we understand the critical role pressure filter vessels play in both industrial and municipal water treatment. These systems are designed to remove suspended solids, contaminants, and in some cases, chemical impurities, ensuring clean and reliable water supply.
To maintain performance and extend system life, a pressure filter operates in a repeating cycle. This cycle consists of four key stages: filtration, backwash, rinsing and restart filtration. Each step is essential for efficiency, water quality, and the ongoing reliability of the vessel.
1. Filtration
During the filtration stage, untreated water enters the vessel through the top inlet and is evenly distributed across the filter bed by a diffuser. As water passes downward through layers of media, suspended solids are trapped within the media bed.
The filtered water is then collected by an underdrain system—either lateral collector arms or a nozzle plate floor—and exits via the bottom outlet.
Over time, as debris builds up, the pressure difference between inlet and outlet (known as differential pressure) increases. Once this differential reaches around 0.6 bar, it signals the need to initiate a backwash cycle to restore system performance.
2. Backwash
The backwash stage reverses the flow of water to dislodge and flush out trapped contaminants. Water enters from the bottom of the vessel, flows upward, and expands the filter bed. The dislodged particles are then carried out to waste via the upper diffuser.
In some systems, an air scour step is used before the water backwash. Low-pressure air (up to 0.5 bar) agitates the filter media, improving cleaning efficiency and reducing water use.
Typical water backwash rates are between 40–50 m³/h per square metre of filter area, though the exact requirements depend on the type of filter media used.
3. Rinsing
Following backwash, the filter enters a rinse cycle. Clean water flows from top to bottom in the normal direction, but is directed to waste instead of the clean water outlet. This stage, usually lasting around three minutes, removes any residual debris or unsettled media, preventing carryover into the treated water supply.
4. Restart Filtration
Once rinsing is complete and the backwash water runs clear, the vessel is ready to return to service. The valves are reset to the filtration position and the pump is started gradually to avoid sudden pressure shocks.
At this point, inlet and outlet pressures are recorded to establish a new “clean” baseline, and the vessel resumes normal operation, beginning the next cycle of contaminant removal.
Cycle Management
Efficient operation depends on consistent monitoring of differential pressure, flow rates, and water quality. Delaying backwash too long can lead to media compaction or channeling, while performing it too frequently wastes water and energy.
By following manufacturer guidelines for flow, pressure, and media care, operators can ensure:
- Optimal performance of the filter vessel
- Extended service life of the filter media
- Reliable compliance with water quality standards
At Glacier Filtration, we specialise in designing and supplying pressure filter vessels tailored to the needs of water treatment projects worldwide. Our solutions are built for reliability, efficiency, and long-term performance.
Contact our team today to discuss how we can support your next project with customised filtration systems.