About adding MBBR media to expand capacity of wastewater plants

2/13/2019

MBBR media with biofilm. Photo from AAEES.ORG.

Moving Bed Biofilm Reactor (MBBR) media has potential to expand wastewater treatment plant capacity, but as with any technology there are some tradeoffs compared to conventional suspended growth systems. Usually constructed of HDPE (polyethylene) with a density near that of water - 0.95 g/cm3. The HDPE is extruded into high surface area shapes which provide a surface for bacterial biofilm development. Biofilm treatment systems go back as far as trickling filters - it is just plastic gives us more options for supporting the biofilm. The MBBR media is kept in the aeration basin by screens with excess biosolids soughing off during movement.

MBBR Benefits

Allows higher levels of biological solids than suspended growth activated sludge systems. Meaning that you can run high MCRT & lower F/M for a given aeration basin/secondary clarifier.
Lower F/M means less solids production - older biomass but this does require sufficient D.O. to prevent filamentous bacteria development.
Helps if your clarifiers are not able to support high MLSS due to hydraulic constraints.

So why don't we see every system converted to MBBR technology? There are a few challenges:

Media can be expensive
Heavy FOG (grease) loadings can foul the media
Running further into the growth curve - lower F/M - requires oxygen normally seen in aerobic digesters. Do you have the aeration capacity for more biomass?

Jon Hancock link

5/5/2019 07:29:47 am

Has anyone had any problems with media floatation due to excessive biomass buildup? If so, what size and type of mbbr media was involved and what was the application?
Has anyone used the Mutag BioChips in domestic/municipal wastewater treatment? Do they perform better than the gear shaped media?

Erik Rumbaugh

5/5/2019 07:50:50 am

In theory, the media encounters enough friction to keep biofilm at target % of weight. Also, biofilm tends to be heavier than water unless you entrap gas bubles or have a lot of grease/fatty acids. Remember that grease and oils are the enemy of fixed film systems.

While we usually think of MBBR media as plastic discs or balls, there are also sponges, PVA balls. Each has advantages and disadvantages. I am currently working on a lab scale with Kurary's PVA sphere carrier. The carrier uses lower volumes in the basin as the PVA sphere has much more suface area than traditional rigid plastic.

For the system you mentioned, I would look at FOG entering and inspect the media to see if it is fouled. If it has grease accumualtion, there are a few tricks that can help remove the low density fatty acid coating.

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About adding MBBR media to expand capacity of wastewater plants

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