MBBR: The Riddle, wrapped in a Mystery, inside an Enigma —Cracked

November 4, 2018

It has baffled me no end why even a half educated Environmental engineer would start promoting the MBBR (Moving Bed Biofilm Reactor) for mini and small STPs when it militates against every prescribed design criterion, every desirable engineering feature which needs to be followed if this technology is to be successful on such small scale. Maybe I am expecting too much from this half-baked engineer. After all it was originally promoted in India by an even less cerebrally endowed company, but with a brand name famous for its sales acumen and not so much for its technical skills in the area of Wastewater Treatment. Yes. I am referring to the same old Zermatt you may have read about in my blog of several years ago :




About 25 years ago I even had the misfortune to totally berate and reject outright a 300 KLD MBBR STP by this company for a software major in Electronics City, Bangalore. Despite adding one more MBBR tank, the STP had to be finally totally scrapped on account of inherent deficiencies. Scrap merchants in Electronic city were the only happy folks.




Now, as happens in any large company, there were many engineers who were only ephemeral transit passengers and who upon parting Company continued the legacy of bankruptcy in technical knowhow and skills. As a result, the City of Pune is full of MBBR STPs dotting the landscape each worse than the previous version due to diminishing knowhow and skills syndrome. A city plagued by MBBRitis.


Recently I cracked the riddle visiting a fairly large MBBR STP in Pune apparently built by one of the offshoots of the Company in question. While chatting with the Supervisor of the plant, I was given a tutorial on the advantages of the MBBR over the Extended Aeration Activated Sludge (EAAS) system. The designer most probably an Ex-Zermatt guy or a plumbing consultant had educated him on the benefits of the MBBR and superiority over EAAS thusly:


The large mass of plastic media floating around in the MBBR tank offers much higher surface area for microbes to grow than the four bare walls of the Aeration tank in an EAAS STP. More the area, better the performance. Elementary my dear Kodavasal.




Brilliant! My God! How could I not know this fundamental difference between MBBR and  EAAS? And me with all my Chemical Engg. background (IIT Madras no less), PhD in Advanced Wastewater treatment from Vanderbilt University (Nashville, USA) under the legendary Prof. Eckenfelder!! I should have died of shame on the spot that day. 


For those of you wondering what's wrong in the designer's reasoning (or lack thereof): MBBR is a reactor operating in the Attached Growth regime. Microbes attach themselves to the plastic media. EAAS, on the other hand, is a reactor operating in the Suspended Growth regime. Microbes are fully suspended in the aeration tank (not attached to the four "bare" walls as the designer thinks). A fundamentally completely different operating principle.



November 01 is celebrated in our State as Karnataka Rajyotsava Day. The day the State was born.

On that Happy note, I wish for a rebirth as a brilliant engineer who knows what is and what is not.

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