Updated: July 2002

1. Purpose

In this high rate filter, bundles of long fibers are fixed at their lower end portions but free-standing at their upper end portions. Feed water is passed downward through the fiber bundles with suspended solids in the feed water being captured in the interstices between the fibers. As the filtering process proceeds, the lower portions of the fiber collapse with the result that suspended solids in the feed water are arrested very effectively due to the higher fiber density in the lower portion of the filtering media. The filtering process is terminated when the pressure drop through the filtering media has reached at a predetermined value. Then, the fiber bundles are backwashed with water (filtered water) and air. Upon backwashing, the fiber bundles are fully extended, and release deposited solids. The filter is ideally suited for treating white water for its recovery and clarifying river and industrial water.

2. Performance

Feed water turbidity: < 50 mg/l
Treated water turbidity: < 2 mg/l
Flow rate: 20-100 m/h
Backwash time: 6 min
Water recovery ratio: 80-95%

3. Characteristics

The use of long fibers (polyacrylonitrile) permits the filtering process to occur at flow rates far exceeding those of the conventional sand filter. The higher flow rates achievable with this filter results in significant saving in space requirements. Being fixed to the filter bottom, the fiber bundles stay put even when back-washed at exceedingly high flow rates, which in turn results in a short duration of backwash. Standard and skid-based filter units are available. Therefore, these filter units can be installed with a minimum of site work. The fiber filtering media are resistant to any chemical attacks, and therefore can be used for treating not only process water and white water but various wastewater as well.