Ootmarsum, Netherlands


Rain water flow, 150 m3/h (fluxes up to 65 l*m-2*h-1) Dry weather flow, 75 m3/h (fluxes up to 55 l*m-2*h-1)


October 2007


Airlift™ MBR


Waterschap Regge en Dinkel, a Water Board in the East of Holland, has realized an innovative Hybrid MBR for treating municipal wastewater at the WWTP Ootmarsum.

The hybrid systems combines conventional biological treatment, followed by sandfiltration with membrane bioreactor treatment as shown below in the schematic overview. 

The Airlift™ membrane unit is delivered by Pentair. The MBR was successfully commissioned in October 2007 and the actual performance of the bioreactor and the UF installation are both above expectation.

Reasons to choose the Airlift™ MBR technology were:

• robust and reliable system
• low energy and chemical     
• dry solution (side stream)
• closed system, easy to clean
• fully automated
• high water quality
• small footprint

Flow chart

Pentair X-Flow flow chart Ootmarsum case study

airlift mbr

Airlift™ MBR is a compactbuilt purification system combining the biological degradation (biological N and P removal) step with UF separation placed outside the bioreactor. In the UF membranes, activated sludge is circulated over the modules combined by continuous aeration controlling the cake formation, while permeate is extracted at the permeate side. The Airlift™ system is a cost-effective method for treating municipal wastewater in a clean setup.

Application area
High mixed liquor suspended solids (MLSS) streams, up to 15,000 mg/l.

Main application

Municipal/ low industrial polluted wastewater treatment plants.

System lay-out

Airlift™ MBR systems are available as standardized, modular skids. The modules are placed vertically resulting in a reliable and compact installation.

Scope of supply

84 x Compact 33V – 5.2 mm UF membrane
5 x Airlift™ skid
1 x Airlift skid executed with 12 Helix membranes since february 2015


The ultrafiltration system consists of four skids with a total of 96 Xiga 40 UF modules capable of processing 7000 m3 of water a day. The complete treatment plant operates automatically. Incoming water from the mains is stored in two 800 m3 storage tanks from where it is pumped to the four activated carbon tanks containing a total of 66 m3 of filter medium. After going through the activated carbon tanks and the organic scavenger, the water is pumped to the Pentair skids which have a combined normal throughput capacity of 400 m3/h. The Xiga technology is effective in removing 99.99 percent of viruses and 99.9999 percent of bacteria, including water borne cryptosporidium. 

Minimizing water wastage is another key part of the Pentair system philosophy. 8 m3 of wash water an hour from the carbon filters and the ultrafiltration modules is pumped to a 60 m3 holding tank before going through the Pentair water recovery system. This has a capacity of 10 m3 an hour and incorporates the company’s Aquaflex 40 UF modules. For every cubic meter of water going through the recovery system, only 10 percent goes to waste. To ensure maximum performance, the plant is maintained in close association with Pentair under a service agreement.

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