Dear Respectful researchers
I need the information regarding to limitations and disadvantages of the MBR process in treating high industrial strength wastewater. There are some limitations such as aeration limitations, Stress on sludge in external MBR, Membrane pollution, and etc. I would like to explore the limitations in the full-scale installation.
Regards,
Ata
MBR is relatively expensive to install and operate. It requires high energy and found to reject only 98% of organic carbon and 90% of ammonium nitrogen. Therefore forward osmosis membrane bio reactor is better to remove greater than 99% organic carbon and 98% ammonium nitrogen. They have the better compatibility than conventional membrane bioreactor.
Daer Dr. Tarafdar
Thank you so much for your valuable contribution.
Regards,
Ata
Most drawback is fouling of the membrane.
For high strength industrial wastewater don't keep biomass concentration too high, aeration could be a drawback in this case.
MBR has some disadvantages. It's including:
• Membrane surface fouling
• Membrane channel clogging
• Process complexity
• High capital cost and operating costs
• High running costs
• Limited flow capacity – equalization required
• Membranes subject to fouling and failing
• Cleaning chemicals necessary
• Increased foam potential
• Fine screening required
• More complex operations
All of them effects to result of MBR
Dear Muhammad and Thanh
Thanks for your contribution.
By the way, Thanh, could you please provide more details about the limitation of flow capacity and potential of foam increasing in the MBR process?
The following papers may be help you:
http://www.sciencedirect.com/science/article/pii/S0167779907003216
http://www.sciencedirect.com/science/article/pii/S0011916410005618
Conveniently, fouling, adsorption and concentration polarization are considered major limits which tend to reduce the performance of the membranes ..
The fouling of a membrane can be defined as the set of phenomena that intervene in the modification of its filtering properties. There are three forms of fouling :
- If the particle size is greater than that of the pores, a fouling on the surface, called clogging, occurs (surface deposition of the membrane).
- If the particle size is considerably less than that of the pores, the particles will enter the membrane, gradually reducing the size of the pores until they completely block. This is called pore blocking. There follows a reduction of the porous surface of the membrane.
- If the particle size is similar to that of the pores, a phenomenon of pore blockage occurs. This phenomenon of blocking leads to a reduction in the membrane filtering surface.
However, the adsorption and polarization phenomena do not directly involve the size of the flocs but rather the interactions between the suspension and the membrane.
Adsorption is an irreversible phenomenon due to physico-chemical interactions (hydrogen bridges, Van der Waals bonds and electrostatics) between the solutes and the surface of the membrane. It corresponds to the formation of one or more molecular layers on the surface or inside the pores of the membrane or at the level of the filter cake. There is then a change in density and pore size of the membrane.
Concentration polarization describes the tendency of the solute to accumulate in the vicinity of the surface of the membrane. The progressive accumulation of species by convection (molecules or particles) establishes a concentration gradient between the wall of the membrane and the solution. This difference in concentration leads to a flow of diffusion of the membrane towards the solution (retro-diffusive flux). This phenomenon can lead to the formation of a gel layer and the precipitation of the solutes. The layer thus formed constitutes a second filtering barrier capable of retaining particles having dimensions smaller than the cut-off threshold of the membrane.
fouling by adsorption requires chemical washing in order to regenerate the filtration performance of the membrane. Pore blockage and particle deposition can be eliminated by backwashing when membrane technology allows (hollow fiber membranes). For other membrane technologies, chemical washing is required. Chemical washing involves the use of an acidic solution (eg citric acid) to remove fouling due to the inorganic material and an oxidant (eg, NaOCl solution) to oxidize the organic material.
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