Interesting Zeolite/nutrient thread in SPS forum

[Randy Holmes-Farley]

It still isn't making sense to me. I do not believe that the local concentration "near" the surface will be higher. I believe that it will be lower (before equilibrium) or the same (at equilibrium).

If we were talking about a simple electrical double layer, then I agree that the cations may be higher in the near surface region (near being maybe 3 nM). But that isn't, I presume, what we are talking about. Instead, I'm figuring it is a clear surface bound situation, and that the concentration of ammonia 5 nm from the surface will not be above the bulk water.

[Habib]

Randy:

If I would use other terms such as the mass transfer rate will increase does it then make more sense to you?

[Randy Holmes-Farley]

Sorry, no.

Do you believe that the phosphate concentration 1 um away from your Phosphate Killer is higher, lower, or the same as the bulk water?

[Boomer]

Jörg

Thanks for popping in

is in the range 1 - 10 Angströms (0,1 - 1 nm), and bigger sized pores or channels between the crystals > 50 nm.

Yes, but not all zeolites are the same or lets say have channels or voids. It depends on their geologic origin. Clino from formation x may not respond the same as clino from formation y. So the affinity will be less with some and more for others.


Hab

From what I have seen so far clinoptilolite has the largest affinity for ammonia over other cations when looking at zeolites only

Yes, most others aren't this high or those that are not common zeolites. Clino by far is much more common that other natural zeolites.

Do you or anyone else have the values for the affinities (relative selectivity coefficients) for the cations on clinoptilolite?


I see you found some coefficients, when I get home I will go through my 4 zeolite text books and see what I can find for you on Clino

This makes me believe that if one would design a filter which transforms ammonia faster using bacteria and would only want to use zeolites that clinoptilolite is probably the best candidate.

If one would like to use the ability of a media which attracts ammonia towards it's surface then one would not like to have a thick biofilm. The biofilm is the layer of bacteria and perhaps some sort of "glue" the bacteria excrete.
The thickness of a biofilm is reduced if the flow rate is higher.

Good thoughts, I guess I never thought of Clino in seawater and its ability to remove some Ammonia would mean much of anything. Now it does

[Randy Holmes-Farley]

FWIW, I think we have to be clear that no binding agent in seawater "attracts something toward its surface" (IMO).

What it may do is hold something right on the surface that randomly diffuses onto it, hits it, and sticks to it. It only holds it when exactly down onto the surface.

There is no "attractive force" for any ion that is more than a molecule diameter away from the surface, except for the electrical double layer effect, which can't be specific for ammonia or a zeolite.

[Jörg Kokott]

Originally posted by Boomer
Jörg

Thanks for popping in

no worries!

is in the range 1 - 10 Angströms (0,1 - 1 nm), and bigger sized pores or channels between the crystals > 50 nm.

Yes, but not all zeolites are the same or lets say have channels or voids. It depends on their geologic origin. Clino from formation x may not respond the same as clino from formation y. So the affinity will be less with some and more for others.

that's why I said "individually different pore size".

[invincible569]

I got this response from Aquareearch:

Edward,

Zeolite is used to absorb ammonia. This works in fresh water.
Saltwater, however, is used to recharge the zeolite by making it release the ammonia. If you use a good biofilter and have an adequate supply of calcareous material such as oyster shell, coral or coraline algae you should not have a problem. Bacta-Pur® N3000 is even used in lobster holding tanks at 4°C (40°F).

Best wishes,
IET-Aquareearch Ltd
Karl
Karl F. Ehrlich, Ph.D.

[Boomer]

Jorg

that's why I said "individually different pore size".

I wasn't sure what you meant by that so thanks for clearing it up

invincible

Go up a few posts, I answered that for you

[javajaws]

Originally posted by Randy Holmes-Farley
FWIW, I think we have to be clear that no binding agent in seawater "attracts something toward its surface" (IMO).

What it may do is hold something right on the surface that randomly diffuses onto it, hits it, and sticks to it. It only holds it when exactly down onto the surface.

There is no "attractive force" for any ion that is more than a molecule diameter away from the surface, except for the electrical double layer effect, which can't be specific for ammonia or a zeolite.

That makes perfect sense and doesn't contradict why they recommend high flow through the ZEOvit reactor. If you can't "attract" the ammonia to the zeolite, then just push it into it instead. Could be another reason why it's also important to "cleanse" the zeolite and replace it every few monthes - all to ensure that the zeolite has a clear shot.

So can denitrifying bacteria use this ammonia that is presumably "stuck" to the zeolite? Will the presence of bacteria prevent additional ammonia from "sticking"?

[Randy Holmes-Farley]

So can denitrifying bacteria use this ammonia that is presumably "stuck" to the zeolite? Will the presence of bacteria prevent additional ammonia from "sticking"?

Since the zeolite does not hold ammonia very strongly, it is in rapid on/off equilibrium between surface bound and free in solution. The bacteria can certainly use that portion that is free in solution for the time that it is free in solution. Sort of like bears catching salmon as they jump the falls going upstream. .

Can they use ammonia that is actually bound to a zeolite, while it is still bound? Or in other words, can they take advantage of a local plethora of bound ammonia? Only if they triggered it to release in some fashion, IMO, and then caught it before it left for greener pastures in the bulk water column (by diffuson to an area that would suddenly have a lower concentration).

Certain organisms might be able to take up phosphate this way when it is bound to a substrate, like CaCO3, by releasing some acid, so it is at least theoretically possible to do something similar for ammonia, although it sounds unlikely to me.

A lot of marine organisms, likely including bacteria, already have active uptake of ammonium ion. So they are already "magnets' for ammonia in the sense that they take up what ammonium drifts near them and into the clutches of active uptake proteins. Whether some nearby bound ammonia would be of interest to them is unknown to me. In the absence of having such ammonia/substrate systems naturally present in the ocean, developing such methods to release bound ammonia from zeolites seems a bit unlikely.

[Habib]

Originally posted by Randy Holmes-Farley
Sorry, no.

Do you believe that the phosphate concentration 1 um away from your Phosphate Killer is higher, lower, or the same as the bulk water?

Same as the bulk water.

But that is IMO not relevant.

The mass transfer rate is what is IMO relevant.

For example assume that the calcium concentration in the water is constant. The uptake rate (mass transfer rate) will increase if teh coral can remove the calcium ions faster from the various compartments. This happens if the coral grows faster.
The mass transfer rate increases

Another example.

Algae have a charge on their cell wall which attracts cations including ammonia. Now assume that the alga could increase the charge density then the concentration of cations around the cell wall will increase and the uptake rate will also increase (depending on the type of uptake mechanism).
The mass transfer rate increases.

If there is a substrate which does not bind ammonia too strongly on it's surface and if bacteria can grow on that surface then the number of ammonia molecules around the bacteria (neglecting membrane surface charges) will be what is in the bulk water + adsorbed on the zeolite surface (moles/ area).

This equates to a higher number of ammonia molecules per volume at a submicroscopical level.

Higher number of molecules per volume equates to a higher amount of ammonia transformed per unit time.

[Randy Holmes-Farley]

That assumes that the bacteria can consume an ammonia molecule that is actually bound.

[Habib]

Originally posted by Randy Holmes-Farley
That assumes that the bacteria can consume an ammonia molecule that is actually bound.

I expect it to be a dynamic process and don't see any reason why the ammonia would not be released from the zeolite surface at a high frequency especially at conditions in which there are so many other cations and the low capacity for ammonia in saline waters.

[Randy Holmes-Farley]

Yes, I agree that there will be a fast equilibrium. But I still contend that away from the actual surface (where I don't believe bacteria can utilize the ammonia), the ammonia in those parts of the system accessible to bacteria will be no higher, so no more bioavailable.

[Ger]

Boomer, Randy and Habib. You guys have come quite some ways since Boomer and I had a discussion not to long ago if and how zeolites have any application in saltwater

Is it to much to ask to have one of you summarize in laymens terms what you have come up with so far? To be honest, some of this information is above my head.

Thanks, Gary

[Randy Holmes-Farley]

From my standpoint, I do not know what, if anything, it does in a marine aquarium other than provide support for biofilms.

[Habib]

Originally posted by Randy Holmes-Farley
Yes, I agree that there will be a fast equilibrium. But I still contend that away from the actual surface (where I don't believe bacteria can utilize the ammonia), the ammonia in those parts of the system accessible to bacteria will be no higher, so no more bioavailable.

I think that is the point we disagree on and I think that a substance allowing to settle nitrifiers on a substrate which also binds ammonia loosly should be an heaven for those nitrifiers.

Like kids in a toyshop.

Perhaps we both will agree soon on what I think happens, or a modification of it or on what you think happens.

Allow me to add a few sentences from various publications in the following post(s)

[Habib]

from: http://www.pnas.org/cgi/content/full/96/7/3463

Nitrification of sludge is accelerated by the use of clinoptilolite, which selectively exchanges NH4+ from wastewater and provides an ideal growth medium for nitrifying bacteria, which then oxidize NH4+ to nitrate (17-19).


Only a title:
Environ Lett. 1973;4(1):27-34.


Enhanced nitrification by addition of clinoptilolite to tertiary activated sludge units.

Sims RC, Little LW.



From: http://dx.doi.org/10.1016/S0032-9592(03)00062-1

Enhanced nitrification efficiency in AS+Z was accomplished by the attached growth of nitrifier on-the-surface of carriers because zeolite has a superior ammonium adsorption capacity.
P.S. AS = activated sludge and Z= zeolite

[Habib]

Just a title:

Preston, K.T. and Alleman, J.E. (1993) "Co-Immobilization of Nitrifying
Bacteria and Clinoptilolite for Enhanced Control of Nitrification,"
Proceedings of the 48th Purdue Industrial Waste Conference, West
Lafayette, Indiana, pgs. 407-412.



From: http://dx.doi.org/10.1016/S0960-8524(01)00160-2

The results indicated that the clinoptilolite provided a relatively low C/N ratio for nitrifiers, due to ammonium adsorption of this mineral, and consequently nitrification was accelerated.

[Jörg Kokott]

Hi,

had some work to do and was unable to quickly react on this interesting discussion.

As a mineral ion-exchanger (clinoptilolithe as a cation exchanger) the zeolite simply binds cations on its surface. However, every particle is surrounded by a dead layer where particles approach the surface via diffusion. The thickness of this dead layer is largely determined by the current/water flow. That means, the zeolite doesn't catch cations, but the latter approach the adsorptive surface and are bound to the surface after contact. Thereby, the charged environment quickens this binding process.

To get back to the hobby: if one puts zeolite into a pot filter, the surface might get saturated with ammonia, which is kept in an equilibrium as sodium and potassium compete with ammonia. Although ammonia is preferentially adsorbed, the high sodium and potassium concentration might fully displace ammonia. That may happen. But this is hypothetically, as we do not know the binding constants for ammonia, sodium and potassium. It even occured that the calcium concentration in seawater was significantly lower after zeolite was applied to the system. That means, although calcium is not preferentially adsorbed, the high concentration of the salt solution has great impact on the adsorption characteristics of the zeolite.

Assuming that the fresh zeolite is saturated with ammonia, AOB can settle on the surface and utilize the ammonia to produce nitrite. But as the establishement of NOB populations characteristically show a lag phase (because they're ammonia-sensitive and toxified by high ammonia concentrations), these NOB would settle on the zeolite after AOB have already developed. Thus, they would potentially occur when almost all adsorbed ammonium is already oxidized to nitrite. This nitrite would then be released to the water and washed off the zeolite filter without being further oxidized to nitrate within the zeolite filter. But this would mean that the zeolite filter would as work as good as a wet/dry filter filled with bioballs and would strongly increase the nitrate concentration in the water.

So, I would suppose something else is happening.

When bacteria settle on a given surface they release strong organic glues to the surface to attach themselves. As these biofilms may break off the substrate, the glue would still stick to the surface and would clog the pores. Consequently, the ion-exchange capacities of the zeolite would strongly decrease with time or even would approach zero. However, if the zeolite grains scratch against each other due to the strong current in the filter, and rub off the surface which is thereby regularily removed to a degree, that ammonia could newly be adsorbed, and new AOB settle on the surface.

I know, some of you are really bored by all these theoretical approaches to the truth, while we're simply speculating about things which might happen or might not happen. This is off course non-scientific, however, as there's great knowledge within this forum, we might rule out specific issues and might have the chance to proof certain hypotheses by experiments in the future.

[Jörg Kokott]

Originally posted by Habib
Just a title:

Preston, K.T. and Alleman, J.E. (1993) "Co-Immobilization of Nitrifying
Bacteria and Clinoptilolite for Enhanced Control of Nitrification,"
Proceedings of the 48th Purdue Industrial Waste Conference, West
Lafayette, Indiana, pgs. 407-412.



From: http://dx.doi.org/10.1016/S0960-8524(01)00160-2

The results indicated that the clinoptilolite provided a relatively low C/N ratio for nitrifiers, due to ammonium adsorption of this mineral, and consequently nitrification was accelerated.

Dear Habib,

all these papers are interesting, but they all use industrial wastewaters, and not seawater for their experiments!

[Habib]

Originally posted by Ger
Boomer, Randy and Habib. You guys have come quite some ways since Boomer and I had a discussion not to long ago if and how zeolites have any application in saltwater

Is it to much to ask to have one of you summarize in laymens terms what you have come up with so far? To be honest, some of this information is above my head.

Thanks, Gary

My current opinion (but can change) is that some zeolites have the potential to enhance nitrification rates thus reducing the nutrient ammonia at a faster rate.

Experiments would have to show if some zeolites are really much better than some other substrates in a seawater environment.

[Habib]

Originally posted by Jörg Kokott
Dear Habib,

all these papers are interesting, but they all use industrial wastewaters, and not seawater for their experiments!

Yes, they are and I also expect these effects to be (far) less pronounced in seawater but still they might be significant enough.

I also wanted to show that that using an ammonia adsorbing substrate can enhance nitrification rates.

[Habib]

Jörg:

A high flow rate would IMO, and we talked about it before, would allow to keep the biofilm thin so that the surface of the zeolite can still act as a binder of ammonia.


Ammonia is positively charfed whereas nitrite and nitrate are negatively charged and would be taken up by corals and zooxanthellae throug differnt channels.

Furthermore, IMO, ammonia is a better nutrient if at the same concentration as combined nitrte + nitrate.


Removal of ammonia should IMO be the first priority.

Nitrite will be transformed in the tank to nitrate and nitrate can be removed by many methods. E.g by creating biomass (water borne bacteria) and removing them by skimming. Would also lower phosphate.

[Randy Holmes-Farley]

I still don't buy the argument that bacteria can utilize ammonia that is bound in a way that makes it more available than the same solution and solid surface in the absence of such binding properties.

The folks in one of Habib's articles assert that " Enhanced nitrification efficiency in AS+Z was accomplished by the attached growth of nitrifier on-the-surface of carriers because zeolite has a superior ammonium adsorption capacity. "

But there can be many explanations of why one substrate is better for biofilm formation and subsequent nitrification than another. It is the "because" part that I question.