Fine Bubble Aeration

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Masons are the New Zealand agents for Passavant-Geiger Fine Bubble Aeration Membrane Diffusers.

The heart of modern biological wastewater treatment plants is made up of the aeration tanks with their diffuser systems. For this application, wastewater technology today calls for ecologically sound but also economically optimized diffuser systems, that warrant a high degree of procedural flexibility at maximum oxygen transfer efficiency. This is a need we can meet with our wide range of diffuser systems, and we are able to do so to a particularly large degree by providing the optimal solution for the most varied requirements. 

For 25 years we have constantly improved our membrane diffuser to meet the high demands of water and wastewater treatment. Our membrane diffusers are mainly used in wastewater treatment plants as a main element for biological treatment.

Field of application

  • Activated sludge tanks and aerated detritus tanks of municipal and industrial wastewater treatment plants
  • Aerobic treatment of landfill leachate and manure
  • Anti-staling of water
  • Adjustment of pH-value by CO2 stripping
  • Oxygen transfer in fish farming ponds
  • Oxygenation of rivers and lakes

When air is supplied, fine slits in the flexible membrane open and release thousands of fine air bubbles.When the air is interrupted, the slits close as the membrane is pressed to the support, sealing the air inlet opening. Due to this double sealing mechanism, no water can enter the aeration system. As opposed to ceramic diffusers an intermittent operation of the aeration is possible which assures higher reliability.


In numerous worldwide installations our membrane diffusers, the disc diffuser Roeflex®, the Ecoflex® Aeration panel and the tube diffuser Bioflex®, have shown their durability. Several tests from accredited institutes have proven their high oxygen transfer efficiency.

Even though the quality of the diffuser is an important factor, oxygen transfer depends on several factors e.g. tank shape, diffuser  density, immersion depth or specific air flow. Thanks to our profound knowledge gathered over many years in building fine bubble and surface aeration systems, we can offer you the most efficient solution for your application.

Geoff Truscott
09 274 3143



Roeflex® Disc Diffuser

The  Roeflex® disc diffuser stands out for its simple and robust design. The Roeflex® consists of a unique, convex shaped support disc. The disc is covered and enveloped by a flexible, slitted membrane of elastomer. In addition, a ring secures the membrane. Due to the disc’s unique convex shape the membrane is slightly lifted off the disc when air is supplied, thus allowing an even distribution of the fine bubbles generated. The membrane can be delivered in different materials (e.g. EPDM, Silicone) and slit patterns (e.g. HL, SL) according to the application.


The disc diffuser Roeflex® is easily to install and can be mounted in two ways – with R 1/2” thread or with an adapter pin. The Roeflex® with R 1/2” thread is fixed to the distribution pipe by an inside thread, the Roeflex® with adapter pin is fixed with an EPDM-plug into a drill hole in the distribution pipe. Thanks to these fastening systems the Roeflex® offers least investment and installation costs.


  • Diameter 320 mm
  • Membrane Material EPDM / Silicone
  • Specific Air Flow max. 0 – 12 Nm3/(h x Diffuser) 

Key Features

  • High Oxygen Transfer Rate
  • Low Pressure Loss
  • Approved Design
  • Easy and Quick Assembly
  • Integrated Check Valve
  • 25 Years of Experience

Click here to view our projects using the Roeflex Disc Diffusers

Bioflex®ll and Bioflex®lV HPI

A complete tube diffuser Bioflex® consists of two diffuser elements. Concerning the Bioflex®ll these are mounted with four screws composed of stainless steel on a cicular tube. Concerning the Bioflex®lV HPI they are connected through thread adapters with a double nipple. Each element consists of a support tube with inside thread, a slitted sleeve membrane, two clamps to fasten the membrane onto the support tube, and an O-seal for sealing between the distribution pipe and the diffuser element. To avoid buoyancy the support tube is flooded. When air is supplied, it is directed via the double nipple and support tube under the membrane. Through the slits of the membrane the air bubbles smoothly into the wastewater.


In order to supply a matching diffuser for every type of wastewater, Passavant-Geiger produces membranes made of different elastomers for the special requirements of various wastewater. The most common material is EPDM, which has been successfully deployed for long time in municipal wastewater treatment. Particularly in industrial treatment Silicone is used as membrane material. Silicone membranes have a very smooth surface and a high resistance against wastewater that contains grease, oil and aromatic compounds.


  • Membrane Length 500 / 750 / 1000 mm 
  • Membrane Material EPDM / Silicone / NBR / TPU
  • Specific Air Flow max. 0 – 12 Nm3/(h x mDiffuser)

Key Features

  • High Oxygen Transfer Rate
  • Low Pressure Loss
  • Easy and Quick Assembly
  • Connection to all Pipe Systems
  • 20 Years of Experience