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Hello, I would like to know which nutrients I should use to maintain living anaerobic sludge in a bioreactor in order to be able to retrieve a draw volume as needed.
I currently use a mixture of KH2PO4, Peptone, NH4Cl, and CH3COONa as the daily food supply. This mixture is used for aerobic sludge, and I was wondering if it is suitable for anaerobic sludge. If not, what would be the right mix?
Thank you for your help.
You only have to put sludge from the digester into an aeration basin and vice versa to see that these 2 types of treatments do not process the same sludge. Input from people opposed to biological treatments does nothing to help elucidate questions from forum participants.
I'm the only one performing true “biological” treatment of wastewater. So I am not against it.
Simply sticking the label "aerobic" or "anaerobic" on the sludge does not make it so. You have to provide arguments and evidence.
The sludge in the aeration tank is the same as the sludge in the digester: dead, inert organic matter.
To determine what distinguishes "living" organic matter from dead, inert organic matter, all you need to know is that in losing its essential feature of being alive, "living" organic matter gets transformed by Mother Nature into sludge.
10 gr of fecal matter are eliminated in 12-15 days through a "biological" process; sludge is eliminated in the order of months to years.
This lends itself to the question: why does living organic matter turn into sludge?
Wastewater effluent at output of a given habitat has an organic or "biological" feature; therefore it is aerobic.
As it makes its way to the treatment plant, it is in contact with the air. Once in the aeration tank, it is still exposed to the ambient air. So, at this point it is still "aerobic."
- At what point does "aerobic" effluent containing rarefied air become oxygen-free?
- According to what principle?
- What is the proportionality of "aerobic" effluent, since the tanks are open?
- What is the proportionality of effluent without oxygen?
The $64,000 question:
How to determine the dividing line between the aerobic portion and the one without oxygen? Where is it? Does it change with each new input of aerobic effluent? When the effluent is stirred, is the separation between the two maintained? How so? What happens when aerobic effluent comes into direct contact with effluent that contains no oxygen? How does effluent without oxygen maintain itself when it is in permanent contact with aerobic effluent?
In fact, no purifying treatment actually takes place. As evidence, I submit the staggering amount of sludge produced in a wastewater treatment plant yearly. In France we generate more than 35,000 tons, and more than 45 million tons are produced worldwide.
Biological treatment entirely eliminates the organic content of wastewater (mainly fecal matter).
To remove organic material, nature needs time and the appropriate biological parameters.
That is hard to come by in today's wastewater systems. Every day thousands of liters of chemicals are dumped into wastewater: bleach, drain cleaners, powerful household disinfectants, medical and paramedical sanitizers as well as industrial products such as hydrochloric acid, de-scaling and diluting agents, grease—the list goes on.
The effluent is still aerobic, but the chemicals have killed all the microorganisms.
When bacteria drops below the 75% threshold, they are not able to regenerate and any treatment effectively ceases.
Without the biological elements you are referring to, there is no such thing as biological treatment.
Have no doubt, sludge is not dead or inert; it's a mix of "living" and "dead" organic matter as well as minerals. The composition of the sludge and the quantity and nature of the microorganisms present depend on the environment—in particular whether it is aerobic, anoxic or anaerobic—and what the load to be treated is. In short, it reflects the type and the operating conditions of your treatment system. In any event, it is never a completely inert or sterile environment, and that's a good thing since the microorganisms play a key role in the treatment process.
Therefore, depending on your objective:
- To perform kinetic analyses or measurements: do so as quickly as possible after sample taking
- If you want to keep the sludge to seed a reactor or use it in a pilot-scale bioreactor/fermenter: try to establish conditions similar to those of the original treatment system, especially in term of aerobic (or anaerobic) states.
The term "sludge" used in biological treatment refers to a mixture of organic matter both living and inert. According to the residence time in the bioreactors and the organic loads applied, you can get different mineralization rates and therefore different sludge composition…
The choice of microorganism is based on the conditions in the environment, so essentially aerobic (dissolved oxygen) or anaerobic (no dissolved oxygen or chemically combined in the form of nitrates).
Aerobic reactions are faster than anaerobic ones and produce mainly carbon dioxide and water, while there is slower fermentation in anaerobic conditions with associated problems of weather conditions, step sequencing of the reactions, etc.
But overall, the essential food for microorganisms is still organic matter, possibly with N and P supplementation. So, in theory, the same as what you are doing but less often because the kinetics are slower.
Everything depends on what you want to do with your sludge: seed a reactor? Run tests? Measure kinetic or other processes?
If it's just to keep them a few days and then put them in a pilot-scale bioreactor/fermenter, then I don't think you need to do anything, no need to provide substrate. It is more difficult with aerobic sludge, for which you have to provide an aeration device, precisely to avoid anaerobic conditions and possibly give them some food if you want to keep them longer.
To delve further into the topic, you would need to provide more details about your installation and your needs.