High performance filtration with compressible filtermedium

Reference Installations

Tertiary / Advanced Treatment

Since the spring of 2018, the first municipal Flexbed filter system has been running as part of a 4. Purification stage for the reduction of trace substances and for the elimination of phosphorus at the treatment plant Barntrup (NRW).

The plant consists essentially of a contact basin, in which powdered activated carbon adsorbs the trace substances. The loaded activated carbon is combined with precipitated phosphorus in 4 downstream, high-efficiency Flexbed filters, which are designed for a full flow treatment, effectively removed from the waste water (12,400 PE, 160 l / s, 4 filters, total filter surface 16 m²).


Landfill Seepage Treatment (left)

  • Deponie Alte Schanze, Paderborn, Nordrhein-Westfalen
  • 2 x Flexbed Filter Type 1
  • Duplex stainless steel
  • Following attached growth biology and ozone
  • Prior to granulated carbon filtration
  • 19 m3/h
  • Commissioned: 2019

Heavy Metal Removal (below)

  • Domestic Appliance Manufacturer in Bavaria
  • Precipitation and sedimentation of industrial metal production waste water
  • 1 x Flexbed Filter Type 1 used for further clarification
  • 25 m3/h
  • Commissioned: 2017

Further References

  • Clarification of abbatoir waste water following flotation (Germany, 2017)
  • Rainwater filtration (Germany, in planning)
  • TSS reduction (England, 2014, 2017, 2018)
  • Phosphate removal (England, 2016)


Bosman Flexbed Filter - Filter with compressible filtermedium for high performance filtration

The pink balls made of synthetic fibers are responsible for the high performance of the Flexbed Filter. With its compressible filter medium the filter provides variable porosity and high grade contaminant uptake at filtration rates up to 100 m³/m²/h. Particle sizes between 5 microns to several millimeters can be removed effectively from water and wastewater without risk of clogging. Individual adaptation to any filtration task is possible through freely selectable compression of the filter bed. Neither filtrate still fresh water is needed for the backwash.

Flexbed Filter installations have a modular design and are available in different sizes and standard versions. They can be used in a very space efficient, universal and flexible way. Furthermore they provide the option of expansion and upgrade.

Application Fields

  • Final filtration for wastewater treatment
  • Phosphate removal after coagulation and flocculation
  • Tertiary treatment / micro pollutant removal
  • Advanced treatment of combined sewer overflows
  • Purification of storm water drains
  • Prefiltration in front of other systems
  • Industrial wastewater treatment
  • Water recycling / process water treatment
  • Removal of microplastics

Technology / Innovation

The synthetic filter material of the Flexbed Filter is permeabel in contrast to conventional filtering techniques with mineral filter material. The particle-containing water flows through both the pore space between the filter elements and the outer areas of Flexbed balls themselves. The porosity of the entire filter bed grows over 90 % by using the additional space within the filter balls.

This means in effect, compared to conventional filter materials, a doubling of the available pore space and thus a higher expected loading capacity up to 16 kg DM / m³, while conventional depth filters (without flocculation) can take up max. 4.0 kg DM / m³. For simple (flat) sand filter systems even only 1.0 to 1.5 kg DM / m³ are accepted for assessment.

Due to the compressibility of the filter material and hence variability of pore sizes in the filter bed, an optimization of the filtration process and flexible adaptation to different raw water qualities of the inlet and particle sizes can be accomplished without structural modifications need to be made to the filter itself.

The combination of the above-mentioned characteristics allows efficient particle separation with high filter speeds up to 100 m/h and minimal space requirements.

Another advantage of the Flexbed Filter technology is, that the backwash doesn’t need fresh water or filtrate, but only a small raw water flow is required in addition to compressed air. Thus savings arise from both lower construction costs (no filtrate storage tank required) and lower operating costs in comparison to conventional filtering techniques.