membrane bioreactor

1. Membrane bio-reactor
An excellent option for waste water treatment
Under guidance of Dr. P.G Bansod

2. INTRODUCTION
• Urban wastewater is usually treated by conventional activated
sludge processes (CASP’s),which involve the natural
biodegradation of pollutants by hetrotrophic bacteria (i.e.
activated sludge) in aerated bioreactors .Activated sludge could
be separated by gravitational setting. The treatment efficiency is
usually limited by the difficulties In separating suspended solids
(SS’s). The optimal sludge concentration is generally up to
5g/L,which imposes large size of aerated bioreactor. Further
treatment of sludge needs to be provided separately.

3. Membrane bioreactor technology
• Membrane bioreactor Technology is based on Biological Treatment
followed by membrane separation ,system comprising of an intense
activated sludge process with the biomass separation stage carried outby
the cassettes located outside the Aeration tank in a separate membrane
tank.
• The membranes replace the settlement stage in conventional activated-
sludge systems and effectively revelutionize the process.
• The seperation of biomass from treated water using membranes
provides filtered quality effluent , offering possibilities of re-use
• It allows very high biomass mixed liquor suspended solids (MLSS)
concentration to be developed in the bioreactor without the detrimental
effects usually associated with the traditional settlement techniques.

4. Membrane
• It is an intervening phase separating two phases and/or active or passive
barrier to the transport of matter between phases.
• Membrane fibres have billions of microscopic pores on the surface.
• The pores form a barrier to impurities, while allowing pure water molecules to
pass.
• Water is drawn through pores using gentle suction.

5. Process configuration
• Two main process confrigurations of biomass rejection MBRs are as follows:
• (i) submerged or immersed MBR (iMBR):
In the submerged MBR(EMBR), the mixed liquor is pumped from the aeration tank.
By applying low vacuum or by using the static head of the mixed liquor , liquor
effluent is driven through the membrane leaving the solids behind.
(ii) External/sidestream MBR(EMBR)
In the External MBR(EMBR),the mixed liquor is pumped from the aeration tank to
the membrane at flow rates that are 20-30 times the product water flow to
provide adequate shear for controlling solids accumulation at the membrane
surface. The high cost of pumping makes EMBR system impractical for full scale
municipal wastewater treatment plants.

6. Process configuration : Compact layout

8. Working theory
• Normally, systems are built with two different compartments .
The first section is the screening stage where the wastewater enters the
unit. In this area : heavy solids are first separated subsequently
traversing to another compartment which houses the membranes. The
in initial screening is of high importance, as the larger molecules (scum
and grit) will not trap the surface of the membrane and lead to fouling.
In the second compartment, the biological process takes place involving
vigorous agitation, coming from air bubbles generated from a blower
system. This act to scour and clean the surface of the membrane to
prevent buildup material on the and also to provide sufficient oxygen
concentration for biological action that supports growth of bacteria.
Denpending on how the system is design to ensure efficient air to water
transfer, the household MBR is capable to support up to 400ppm of MLSS
level while large-scale industrial waste water treatment plant bioreactor
scan handle up to 20000ppm.

9. Advantages of MBR over other treatment
processes
• The retention of all suspended matter and most soluble compounds witjin the bioreactor leads
to excellent effluent quality capable of meeting stringent discharge requirements and opening
the door to direct water reuse.
• The possibility of retaining all bacteria and viruses results in a sterile effluent , eliminating
extensive disinfection that would be required otherwise and eliminate the corresponding
hazards related to disinfection of products.
• It results in more compact system than conventional processes significantky reducing plant
footprint making it desirable for water recycling applications.
• The process is more compact than a conventional activated sludge process (CAS),skipping
three(3) individual processes of the conventional scheme. The feed wastewater only needs to
be screened (1-3mm) just prior to removal of larger solids that could damage the membranes
• It has higher nitrogen removal rate than ant other treatment processes.
• Finally, it has a comparatively low sludge yield ; therby reducing the IOM cost of the sludge
handing .

10. DRAWBACKS
• Not withstanding the advantages of MBRs,the widesoread implantation Is limited
due to its high costs, both capital and operating expenditure (CAPEX and
OPEX),mainly due to membrane installation and replacement, and high energy
demand. This high energy demand in comparison with CAS , is closely associated
with strategies for avoiding/mitigating membrane fouling(70% of total energy
demand for iMBR).
• Another drawabacks of iMBR is the fouling of membranes.Fouling is the
restriction, occlusion or blocking of membranes pores or cake building by solids
accumulation on the membrane surface during operation which leads to
membrane permeability loss. Though, Traditional strategies for fouling
mitigation such as air sparging , physical cleaning techniques(i.e is backflusing
and relaxation ) and chemical maintainace cleaning have incorporated in most
MBR design as standard operating strategy to limit fouling.

11. Summary of technology
Membrane Bioreactor(MBR)
• Waste water treatment system that include a biological aeration basin followed
by a membrane system-replacing traditional clarifiers
Benefits
• Potential reuse of effluent water
• Smaller bioprocess footprint
• Substantial reduction of effluent TSS
• Eliminating settling challenges associated with a clarfier
Potential Limitation
• Refinery upsets could foul membranes resulting in accelerated rate in cleaning
and replacement.

13. Certain key features of the plant
• The treated water is reused for toilet flushing in the flats of the
Akshardham complex and also in its chillers.
• Acoustic Enclosure are provided around blower which help in
reducing the noise level by about 5-10 db.
• The control system for the plant has been designed so as to be
operated automatically. This automatic provision is beneficial to
department from energy saving point of view.
• The entire plant is encloused in a single building.

14. Conclusion
• The treatment performance of the MBR is better than in conventional activated
sludge process. A high conversion of ammonia to nitrate (>95%) and constant
COD removal efficiency (80-90%) was achieved regardless of the influent
fluctuatuion.
• Microbial analysis of permeate shows the absence of bacterial indicators and
parasitic microorganisms. At the same time, the membrane presented over 98%
efficiency in the elimination of viral indicators.
• The removal efficiency of BOD, COD and NH3-N were ranged between 98.9-
99.9%, 97.8-99.9% and 91.0-100% respectively.
• The removal efficieny of COD was on the average as high as 97% in which 85%
was attributed to the bioreactor and the residual 12%a result of membrane
separation.
• The PH of the effluent was increased by 20.1-39.2% of that of the influent.

15. Thank you