Hi dears
I'm wondering if there is any simple method for determination of aerobic granule per floccular sludge ratio (G/F)?
Thanks in advance
Once your supply air, your oxidizing agent should interact with organic matter, as a result biomass grows. In terms of biomass and sludge we can easily observe bulk of biomass floc. If the sludge is light may be floating. Based on dynamic of flow; there is a chance for you in your specific flow behavior bionucleation and biogranulation occur. In fact the major contribution of your system is related to biological treatment with nucleation system. In such system the flow behavior should have key role in such phenomena. We shall discuss more about biogranulation process.
The best way would be to look at what distinguishes flocs and granules. Two suitable factors would be size and settling velocity.
For size you could use a set of soil sieves to separate the granules from the flocs. However, a dilemma would be that some large aggregates may not necessarily be granules since you can have flocs in the order of 500 um and granules at around 200 um.
The second way would be more onerous. You would need a tall settling column already filled with liquid, add a known quantity of sludge and then give it certain time to settle. Based on a defined settling velocity after a certain time remove what had settled at the bottom - defining it as granules. Use gravimetric analysis on that removed fraction (granules) and then on the solids that remain in the column which settle later. This method is still prone to some error - e.g. a large floc will probably settle faster than a small granule, but because it is a measure of both size and density it would be more accurate.
The issue is further complicated by defining exactly when does a floc become a granule. So whatever method you choose make sure you define it clearly and that it is repeatable.
Thank you dear Prof. Najafpour. I'll appreciate it to talk more with you about this subject.
Dear Hamish
Thank you for sharing your experiences.
As u said, these methods would prone to some errors. If the errors could be negligible, what will be the common settling time for ur second suggestion?
I must add this point that I can easily detect some other particles in addition of granules and flocs, as the substrate is raw wastewater. These unfavorable particles settle like big granules and big flocs. I'm pleased to know ur idea about how I can get rid of these stuff? (They can easily block the filters)
Regards
Dear Ali,
In my opinion, if you ask for a simple method for determination of aerobic granule per floccular sludge ratio (G/F) the use of sieves is the most convenient and simple method.
We work with granular biomass (partial nitrification and anammox bacteria in the granules). We measure the TSS and VSS (g/L) of a 1 L sample of biomass (flocs and granules). Then using a sieve, we can separate the floccular biomass and the granules. Then, we complete both samples to 1 L and repeat the TSS and VSS analysis. With that we have the fraction of the VSS that came from the granular biomass (VSSgranules/VSStotal). It is an approximation of course, but usefull for the evaluation of the granulation process in the reactor.
Dear Ali
If it is sand and grit you needn't worry about it. You will be able to have an idea of its magnitude based on differences between your TSS and VSS - focus on the VSS for flocs vs granules comparison.
If using the settling test method and it is inert inorganics it will settle even faster than the granules, so can be separated this way, or via centrifugation.
For the settling test velocities it is best to check some papers, to some degree it depends on the type of sludge and size of granules. From memory activated sludge settles at a rate of roughly 1-7 m/h. Granular sludge tends to be 10-80 m/h. You will need to confirm these though.
Dears Nicolas and Hamish
There is a relatively resemblance in your both methods. In my opinion, however, these two methods can be joint with each other :)
Many thanks
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