What is a Membrane Bioreactor? - Membrane bioreactors are used during the filtration stages of water treatment. Microfiltration and ultrafiltration are used with bioreactors to filter water. This operation has began to replace older systems as a cheaper more efficient source. It is essential to successful water treatment. -Membrane modules are submerged in the activated sludge to combine
the biological step and the solid-liquid separation step into a single
process. -Combines the use of an activated sludge bioreactor with a crossflow membrane filtration loop. It also provides a barrier to certain chlorine resistant pathogens such as Cryptosporidium and Giardia. -Sedimentation is usually incomplete, in getting rid of microorganisms. -Conventional plants will discharge 10000 to 100000 microbes per milliliter. -Since the membrane acts as a barrier to microorganisms, the quality is much better than that produced by a conventional plant. Also, the membrane barrier allows
the activated sludge to be more concentrated. This reduces
the capacity needed for biological tanks, saving space and money. http://www.mcilvainecompany.com/WEFTEC_2008/WEFTEC58.jpghttp://images-mediawiki-sites.thefullwiki.org/02/4/0/8/54719782764222864.jpgThe Process
-Two MBR configurations exist: internal/submerged, where the membranes
are immersed in and integral to the biological reactor; and
external/sidestream, where membranes are a separate unit process
requiring an intermediate pumping step.
-External/sidestream-The filtration element is installed in either the main bioreactor vessel
or in a separate tank. The membranes can be flat sheet or tubular, and
can incorporate an online backwash system which reduces membrane surface
fouling by pumping membrane permeate back through the membrane.
-Internal/Submerged-The filtration elements are installed externally to the reactor, usually
in a plant room. The biomass is either pumped directly through a number
of membrane modules in series and back to the bioreactor, or the biomass
is pumped to a bank of modules, from which a second pump circulates the
biomass through the modules in series. Cleaning and soaking of the
membranes can be undertaken in place with use of an installed cleaning
tank, pump and pipework.PollutantsThe key pollutants that membrane bioreactors are intended to remove are microorganisms, water-bourne diseases, bacteria,etc.
-MBR system is that it effectively
overcomes the limitations associated with poor settling of sludge in
conventional sludge processes.
- It is also a cheaper source of water filtration being more rapidly used today.
-Filtering creates a disinfection barrier
-Produces less waste.
-Membrane modules are expensive and have to be replaced every 5 to 10 years. -Cleaning solutions for the system can be considered hazardous waste.
Chapman, Stephen. “Membrane Bioreactors (MBR)
for Municipal Wastewater Treatment- An Australian Perspective.” --.
N.p., n.d. Web. 7 Jan. 2011. <http://www.membrane.unsw.edu.au/staff/papers/gleslie/mbr_for_reuse_awa.pdf
Crites, RW, et
al. “Membrane Bioreactor (MBR) in Wastewater treatment.” Operators Notebook.
N.p., n.d. Web. 6 Jan. 2011. <http://www.wrights-trainingsite.com/WWT%20MBR.htm>.
Bioreactor.” Wikipedia. Wikipedia, 31 Dec. 2010. Web. 6 Jan. 2011.