MBR, SBR, Activated Sludge, ATU, Suspended Growth

MBR:  Membrane Bio Reactor
SBR:  Sequencing Batch Reactor
Activated Sludge
ATU:  Aerobic Treatment Unit

Question: What do these three types of system all have in common?

Answer: They are all Suspended Growth systems.

MBR's, SBR's and activated sludge and ATU systems all work in the same manner: they blow air into wastewater.  That's it.  Within the pool of frothy wastewater are free swimming microorganisms that utilize the wastewater as a food source. The wastewater is supposed to be treated as the microorganisms act on it. 

This design, generally best suited for municipal scale systems that have access to a supply of full time(24 hr/day) operation and maintenance personnel,  has been adapted for smaller scale and residential systems as well.  You can find them under a variety of brands but they all look about the same and they all operate in nearly exactly the same manner.  A blower blows air into a pool of wastewater 24 hours a day, seven days a week.

However, and this is common knowledge to almost everyone in this industry even if they don't like to admit it, suspended growth systems are notoriously unreliable.  In fact, I attended a conference where the president of one of the really big manufacturers of a suspended growth systems was arguing that his company's individual systems should not be assessed based upon the results they were producing but rather, all the systems should have their results averaged.  I would like to be able to extend this logic, however tortured, to traffic laws.  "Well officer, I was only speeding for 10 minutes but I have been driving for 3 hours, so on average, I have not been violating the speed limit!"

Eliminite is an advanced onsite wastewater treatment system that differs significantly from the suspended growth systems.  The microorganisms providing the treatment are not free swimming in a pool of liquid.  Instead they are attached and immobilized on the surfce of our patented MetaRocks.  Why is attached superior to suspended?

"It is obvious that attached microorganisms stay in the system longer than non-attached microorganisms. Retention of slow-growing microorganisms such as nitrifiers and methanogens is facilitated by attachment, this leads to a higher inventory of the microorganisms in the system and thus reduces the hydraulic retention time required for treatment."

One reason is that the biofilm in which the microorganisms are embedded provides significant protection from toxic substances.  You can think about this as the difference to being outside versus being indoors.  The free swimmers are relatively unprotected and exposed to the elements where the attached growth has the protection of the biofilm.

I recently read a study that helped explain why so many suspended growth systems have such poor results.  In my experience, the ATU systems seem to perform well if they are in a study that is carefully choreographed and executed.  Once they are in the real world, everyone is left scratching their heads trying to figure out 1) why the ATU is not working and 2) how to fix it.  I have written on this blog a few times about Maryland's Best Available Technology (BAT) and how the state was required to allow loads of additional nitrogen into the aquifer and Chesapeake Bay because the BAT-ATU could not duplicate the same level of treatment it displayed in one of those play-act studies. 

Here is what I learned:

Bacteria within biofilms are much more resistant to toxins than are free-floating bacteria.  One study found that a bacteria attached to glass slides displayed a 150-fold increased resistance to chlorine disinfectant compared to free-floaters.  In another study, antiseptic concentrations had to be incresed by 40 times to kill attached bacteria versus the free-floating counterpart.   

It was previously thought that attached growth systems resistance to shock loads was due to the huge numbers of bacteria present.  I will write about this in a few days because it is true and worth examining.

If you look at manufacturers recommendations for ATU systems you will find that they are very concerned about what you put down your drain.  They don't want you to use bleach, water softeners, anti-bacterial soap or pine based cleaners.  A distributor of ATU's told me, trying to make excuses for his systems poor performance, that one person in the home was taking chemotherapy drugs and this was why the residents, in addition to dealing with cancer, had to deal with a non-compliant septic system as well.

Eliminite systems seem to take whatever is thrown at them, deal with it and produce stellar results.  A recent set of samples taken from one of our heavily used, high strength waste systems produced the following results:

Eliminite Results

Ammonia: 99% removal
TKN: 99% removal
TSS:99% removal
BOD: 99% removal
TN: 90% Removal

This data was collected in Montana in late December from a system that has had nothing done to it and no operator. It has been receiving high strength waste:  BOD>1200 mg/L, Total nitrogen>400 mg/L.  I will gladly provide the actual lab data if you ask.