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Rick Dunn, 06/29/2007


Last month, Jeff talked about the issue of change and our “cheese moving”.  A very good article considering all the change this industry is encountering.  One recent change we have had to adapt to is a new treatment technology: membranes.


Membrane, or Membrane Bioreactor (MBR), is a phrase being thrown around lately when discussing wastewater treatment.  But what is it?  The membrane, or membranes, because there are many in the system, is only one piece of the treatment process.  Membranes provide ultra-filtration of treated wastewater producing a very high quality final effluent.


The treatment process and equipment varies between manufacturers but they function in very similar ways.  Basically, a Membrane Bioreactor is a mechanical treatment plant with an extremely fine filter on the end.  The membrane takes the place of the final clarifier, or final settling tank, and functions as a filter.  Membranes can be incorporated into any existing or proposed treatment process.


Why is there a sudden interest in membranes?  Membrane Bioreactor treatment for wastewater is relatively new to the United States, but has been in use for years in Europe, Asia, and other parts of the world.  Pennsylvania, and other states, are increasing effluent quality limits for treated wastewater discharges.  These revised limits are being imposed for effluent stream discharges, as well as land application of the effluent.  This has forced the wastewater treatment system designer to evaluate systems that can consistently produce an effluent that meets these more stringent permit limits.


As stated before, membranes can be incorporated into any treatment system, new or existing.  What I think interests our clients most are the pre-engineered package MBR treatment plants.


A few treatment equipment suppliers are manufacturing a product that is a self-contained system in a fabricated steel box.  The unit is a combination of an activated sludge process, a wastewater treatment process characterized by suspended growth of biomass, with a membrane filtration system designed to separate extremely fine particles.  This combination of functions results in a high quality effluent.


Besides providing consistent high quality effluent, another benefit of the MBR is standardization.  The treatment facility is designed around the MBR creating a standard design that needs very little alteration from project to project of similar size.  Placing the unit inside a building is possible; creating a very clean looking treatment facility on a relatively small footprint.


In addition to the MBR unit, there are other items necessary to construct a functioning treatment facility.  An aerobic digester (sludge tank) must be added and, depending on the specific design, the addition of an influent pump station, influent flow equalization tank, effluent equalization tank, and disinfection system must be considered.


The cost of the MBR system is comparable to any other mechanical treatment plant and the per dwelling unit cost is contingent on project size.  The economics become more attractive as the number of units increase and the project design flow approaches 25,000 gallons per day.  The benefit is not really a cost savings in most cases, but the ability to develop a concept design and an accurate budget construction cost for more than one specific project.  This gives the owner a better idea, at the start of a project, what the wastewater variable is.


Should you consider a MBR for your project?  Every project offers unique design considerations regarding wastewater flow, wastewater strength, type of disposal, effluent limits, and site layout.  Vendors of Membrane Bioreactor Systems each offer a unique product.  Evans Mill Environmental, LLC can evaluate your specific project, whether it is new construction or an existing facility upgrade, and determine what is best for you in terms of cost, operation, and performance.


We have several ongoing MBR projects and are one of the first in this region to obtain a Water Quality Management Part 2 Permit for an MBR.  Let us share what we have learned and help get your project permitted and constructed.


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18 Nov 2013



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