Efficient Wastewater Treatment The Secret Inside: Discover Submerged Membrane Bio Reactors

Author / Editor: Carsten Bachert* / Manja Wühr

The extension of capacity is a common requirement. But space is usually limited — especially in existing wastewater treatment plants. The advanced Bio-Cel-Modul now provides four percent more performance with the same module size, as this article shows...

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Microdyn-Nadir's range of filtration
Microdyn-Nadir's range of filtration
(Picture: Microdyn-Nadir)

Nowadays, the use of submerged modules in a so-called MBR (Membrane Bio Reactor) for efficient wastewater treatment is a proven method and it is state-of-the-art technology. For instance the Bio-Cel made by the Germany-based membrane specialist Microdyn-Nadir is currently used on every continent predominantly in MBR systems in the municipal and industrial sector. Industry examples are:

  • fish processing in Mexico,
  • pasta production in Italy,
  • fruit juice production in the United Arab Emirates,
  • dairy in South Africa.

Self-supporting Membrane

Bio-Cel is a submerged “hybrid module”, which combines the advantages of conventional flat sheets and hollow fiber modules without incorporating their inherent disadvantages. During the production of the membrane sheets, two membranes are physically bound over the entire surface on both sides of a spacer material. This results in a self-supporting membrane pocket which can be backwashed and is very flexible at the same time.

In addition, Bio-Cel offers the advantage that the membrane laminate sheets in the module do have a self-healing mechanism. If the membrane surface is not intact or even entirely damaged (e.g. cut corners or deep scratches), the increased suction at the site of the damage causes biomass to quickly accumulate and automatically seal the breach, usually in less than two minutes. Therefore, the module can deal reliably with highest demands in terms of solids retention during operation even in case of severe damages of the membrane. The Bio-Cel modules are available from 50 to 1920 m2 membrane surface. For piloting purposes a module with 10 m2 can be used.

Comparing the previous model Bio-Cel BC400 with the new module BC416 it appears that they visually do not differ from each other. The connections for the filtrate (or permeate) and for the aeration are designed identically for both module types. The design dimensions have not changed; module length, width and height are the same as well. The concept of a separate base-frame with built in fine-bubble aerators and separately replaceable membrane cassettes can be found in both Bio-Cel modules.

Intrinsic Values

But the inside of the module was changed significantly. By modifying the suspension of the self-supporting laminated membrane sheets two improvements were achieved. First, the distance between the membrane sheets and the cassette walls were optimized. As a result, the air distribution during the operation of the submerged Bio-Cel BC416 is more even, particularly as the distance between the membrane sheets as well as the first and last membrane sheets to the cassette walls is the same.

Second, two additional membrane sheets have been added into the cassettes. This increases the membrane surface by four percent, which also increases the module performance by four percent. At the same time, the packing density is boosted without decreasing the distance between the membrane sheets. A minimization of the distance between the membrane sheets to increase the packing density was deliberately omitted, since such an adjustment would negatively affect the tendency to clog and thus adversely affect the operational safety.

* The author is Sales Director Middle East & North Africa at Microdyn-Nadir, Wiesbaden/Germany.