MBR technology

Waterleau has left the limited end-of-pipe thinking approach and has switched to a process-integrated approach.
The Membrane BioReactor (MBR) ideally fits in this philosophy. It produces an effluent that is extremely pure and appropriate for immediate reuse: no wonder that it is considered worldwide as the most promising techno logy for wastewater treatment. Micro- and ultrafiltration membranes can be used for the separation of sludge and biologically purified wastewater.

By replacing the sedimentation step by a membrane separation it is possible to operate the bioreactor at much higher sludge concentrations (typically 12 to 15 g/l). Hence, the volume of the bioreactor can be reduced drastically (by a factor of 3). An additional advantage of this system is the fact that the filtrate is virtually free of suspended solids and bacteria since these cannot pass the membranes. The filtrate will thus be ready for reuse or for further treatment by reverse osmosis.

There are two types of MBR's:

1. membranes placed externally, i.e. in an external loop to the bioreactor (X-TRACTOR® MBR)
2. submerged in the activated sludge, i.e. in the bioreactor itself (ATLANTIS® MBR)

Both membrane bioreactor concepts have there own advantages and they have their own range of application.

X-Tractor^® Crossflow MBR

In an X-TRACTOR^® installation tubular membranes are placed in an external loop of the bioreactor.
In an X-TRACTOR^® MBR the sludge – purified water mixture is passed at high speed along the surface of the membrane in order to maintain turbulent conditions at the membrane surface.

The water will pass through the membranes while the suspended solids are retained and recycled to the bioreactor. Due to high speed recirculation these membranes have very low fouling characteristics and are therefore especially used in rather difficult wastewater applications such as laundry and leachate wastewater treatment.

A potential disadvantage of this technology however compared to the ATLANTIS^® technology is the higher energy consumption. Therefore these installations are generally used to treat smaller but rather difficult wastewater flows.

An advantage of placing the membranes outside the bioreactor is that harsher membrane cleanings can be performed easily since there is no immediate contact with the biomass in the bioreactor.