Types of membrane bioreactors used in

treatment of waste water

A membrane bioreactor refers to the amalgamation of a membrane and a biological

reactor. The membrane bioreactor is commonly used in wastewater treatment plants in

large industries. Generally, a membrane bioreactor as used in the treatment of waste

water can be categorized into the following groups:

· Extractive Membrane Reactor

· Recycle Membrane Reactor

· Membrane Separation Reactor

1. Extractive membrane bioreactor

An extractive membrane bioreactor improves the overall performance of waste water

treatment by capitalizing on the membrane’s potential to achieve a high degree of

separation while at the same time allowing components of the waste water to be

transported from one stage to the next. This particular separation helps to maintain the

optimal conditions inside the bio-reactor hence enabling the waste water pollutants to be

biologically broken down.

In extractive membrane bioreactors, the membrane is not affected by the toxins

contained in the waste water since conditions inside the bioreactor are at optimal hence

ensuring complete degradation of the toxins within the waste water. This system of

waste water treatment has been proven to be effective in treating pollutants such as

chloroethanes, tuolene and chlorobenzenes

2. Recycle Membrane Bio-reactor

This membrane bioreactor is made up of a reaction vessel which works as a stirred tank

reactor and an externally attached membrane. The waste water and bio-catalyst are

mixed with the reaction vesselin measured concentrations. The mixture is then pumped

via the route of the externally attached membrane. Small molecular compounds

permeate through the membrane, while the large molecules are rejected and recycled

back into the reaction tank. This membrane bioreactor has been successfully tested in

industries dealing with bio-remediation activities, for the complete removal of

pesticides, fungicides and other air pollutants.

3. Membrane Separation Bioreactor

Most aerobic waste water treatment systems use activated sludge to treat municipal as

well as industrial waste water. This method is highly reliable and this is what is

attributed to the success of this waste water treatment technology. However, large

sedimentation tanks allowing unlimited time for the sludge to settle are required to

obtain sufficient separation of the waste from the water. Moreover, close monitoring of

the treatment process is required so as to prevent poor settling of the solids which lead

to the accumulation of sludge.

A membrane separation bioreactor has a complete barrier which suspends the solids

hence producing better quality of treated waste water. A membrane separation

bioreactor has the following advantages over an aerobic waste water treatment system:

· Easy to operate and requires minimal maintenance for instance cleaning since the

sludge is not allowed to settle and accumulate

· This membrane bioreactor does not require sedimentation or any equipment after

treatment to attain good quality of water which can be reused

· This method is capable of removing bacteria and viruses hence the effluent that is

finally discharged bears no threat to the environment.

· This method of waste water treatment does not emit any smell since all equipment

used can be firmly shut during the process.

Membrane bioreactors have proven to be more than effective in waste water treatment.

They are affordable, reliable and easy to maintain. Perhaps it’s time all industries and

municipal waste water treatment plants use them as their only waste water treatment

technology.

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