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Emerging Technology: Biological Wastewater Treatment with IFAS & MBBR
Author briefly reviews two emerging biological wastewater treatment technologies. Review by Sudhakar Viswanathan
Wastewater treatment plants in cities experiencing population growth and restricted by space for expansion are increasingly adopting alternatives like modified activated sludge (AS) systems. Emerging technologies among the alternatives include integrated fixed film/activated sludge (IFAS) and moving bed biological reactor (MBBR) systems.
Systems such as IFAS and MBBR involve the addition of floatable plastic media into existing AS basins to provide active sites for biomass attachment. This increases the biomass concentration without the need for increasing the mixed liquor suspended solids (MLSS) concentration, reducing the cost of operating the return activated sludge (RAS) line.
IFAS is often confused with MBBR. Although similar in configuration, IFAS usually includes both fixed film and suspended biomass, So the RAS line is functional, but at a lower rate. Whereas in an MBBR, the process is strictly fixed film with biomass attached to the surface of the media. The media used both in an IFAS and MBBR are not consumed or recycled, hence additional screens are required to prevent the media from washing out of the desired basins. Additionally, pretreatment screens might be needed to prevent undesired waste from clogging the media.
The media used in these systems come in all shapes and sizes, mostly made of plastic. The design of the media is such that maximum surface area is available for biomass attachment, allows easy transfer of nutrients and oxygen and is relatively simple to extrude/manufacture. The smaller the media, the finer the barrier screens, the larger media can make do with the regular coarse screen. The screens have a partial impact on the plant hydraulics, resulting in increased overall headloss. Also, smaller media is more prone to clogging and restrictive to transfer of nutrients and oxygen, hence operates at a lower efficiency compared to its large media counterpart.
While upgrading an existing AS plant into an IFAS or a MBBR system, it is common to alter the air diffuser system. While most AS plants use full floor fine bubble diffusers, most IFAS and MBBR systems require either partial floor fine diffusers or full floor coarse bubble diffusers.
The advantages of switching an AS plant into an IFAS or MBBR system are:
*The ability to increase plant capacity without increasing basin volume, most manufacturers claim a 50 percent increase in throughput
*Able to fully nitrify in systems previously partly nitrifying or not nitrifying at all
*Also, it is know that fixed film systems are more adaptive to changing influent conditions
Maintenance is relatively minimal as these processes do not require backwashing or scouring of the media, excess biomass simply passes through the screen to the secondary clarifiers.
While there are numerous IFAS or MBBR options to choose from, it is imperative to take this into consideration the following factors before selecting a system.
*Headloss: Increase due to addition of screens
*New aeration system: If a particular iFAS or MBBR system requires an aeration system different from the existing type
*Cost: the lifecycle cost must be worked out aside from capital and operating expense
Where situation permits, sustainability and ecological impacts of these processes should be considered prior to selection. Also, a thorough feasibility study should be performed prior to selecting the best treatment option for a given plant. This might include, but is not limited to, an onsite pilot study to evaluate technology feasibility, a lifecycle cost analysis and impact assessment for each alternative.
Posted by Moderator on January 12th, 2006 filed in review 18 Comments »
June 13th, 2007 at 9:09 am
Good overview, but neglected to include the fixed media option along with the floating media. Fixed media does not require inbasin screens and can normally be used with the existing fine bubble diffuser system. The bugs don’t know what they are growing on, so the process benifits of both fixed and floating media are the same.
July 22nd, 2007 at 12:36 pm
@ Dick Pehrson
If by fixed media you are referring to systems using cloth or plastic tubes/sheet, you are surely not looking at it from the point of view of maintenance. Snails and other critters make such fixed media home and the head loss through the system goes through the roof if the system experiences shock loads especially of solids from the preceding clarifier upset.
You are right about the screens, fixed media does not need screens, but in terms of material capital cost, the fixed media does cost higher and they do need anchor or frame to stay in place.
Hope this information is useful.
July 22nd, 2007 at 12:38 pm
@ Dick Pehrson
BTW, your BioPortz media looks awfully similar to K1, is it the same?
November 12th, 2007 at 2:57 am
IFAS with moving media is a good process for high plouted wastewater produced by factories such as meat processing and dairy industry. the biomass concentration will be increesed after one month operation significantly.
November 12th, 2007 at 6:02 am
@ sabzali
With IFAS, you are able to control the return sludge, so MLSS concentrations can be maintained at the desired levels.
December 15th, 2007 at 9:22 am
How much more oxygen will be needed for the higher biomass concentration in the aeration tank and how much more BOD and nitrification/denitrification will occur? Is there a model to use for design?
March 12th, 2008 at 6:11 pm
@ Yusef Jalali
There are some well modeled systems out there, but most are proprietary and may not be easily accessible. What exactly do you plan on doing?
March 14th, 2008 at 11:23 am
bonjour
je trouve que votre site est intéresant sur ce je voulais juste vous demander si possible que vous me fasse parvenir un exemple d’étude de cas sur les systèmes ifas et MBBr merci
April 28th, 2008 at 8:01 pm
@ toupou patrice
Send me your questions about IFAS/MBBR and I can send you answers and example case studies.
Envoyez-moi vos questions sur IFAS / MBBR et je peux vous envoyer des réponses et l’exemple des études de cas.
July 15th, 2008 at 12:38 am
Hi Sir ,
I am a final year Biotechnology Engineering student from Kerala, India. My final year project is on degradation of dairy Waste using MBBR technology. I would like to know if a holistic approach to dairy waste treatment can be done using MBBr , ie , if treatment is possible without the removal of oil and grease from the effluent.
August 3rd, 2008 at 9:27 pm
hello
I need someone to help me in process design of an IFAS system, I must consider a fixed media made of PVC sheet, I am in hurry
August 4th, 2008 at 7:31 am
My comment is similar to Yusef’s. it Is not easy to get information from manufacturers. In my case, all I need is an approximate footprint for a MMBR plant (including clarifiers). Is there any rule of thumb? Also, since most of the literature states that primaries are not necesary, I believe they would be beneficial if the particulate portion of the organic matter is high. Am I right or wrong?
August 4th, 2008 at 4:25 pm
@ Masoud
Fixed media might cause red worm issues. Try floating media instead.
August 4th, 2008 at 4:32 pm
@ Khalil Foukay
No rule of thumb, but I do not see why it should be difficult to get info from manufacturers, unless you are trying to design your own MBBR in which case you are not going to get much help. Primaries not necessary is decided on a case by case basis. I suggest you try calling one of the manufacturers.
October 15th, 2008 at 10:26 pm
hi. able the IFAS system for the wastewater 153000 person and flow 26000 m3/day???
October 15th, 2008 at 10:29 pm
please help me.thanks
October 15th, 2008 at 10:37 pm
i want desinged wastewater plant for city by 153000 person nd 26000 m3/day flow. i need information about IFAS & AGAR OR OTHER PROCCES SUITABLE FOR THIS CASE.WASEWATER PLANT IS IN THE PARK .ODOR CONTROL VERY IMPORTANT.
March 22nd, 2009 at 3:23 pm
@ behnaz
Send info via this contact form.