sherm71tank
Premium Member
Or, the wetter you skim the better? Which would explain why so many favor the becketts. Not that you can't wet skim with other types.
Skimmer 2 minute dwell time. Anyone have any proof of this?
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mr.wilson
.Registered Member
Escobal refers to water dwell time and air dwell time, with bombardment rate being the ratio of the two. This would hold both of our definitions true.
We're not so far apart on the use of needlewheel technology as well. Needlewheel is what I pratice, air-driven is only what I preach.
Do you have a link to Randys' article. I haven't come across it.
We're not so far apart on the use of needlewheel technology as well. Needlewheel is what I pratice, air-driven is only what I preach.
Do you have a link to Randys' article. I haven't come across it.
hahnmeister
In Memoriam
thats true, he does say interface area, but as it relates to time. If the interface area is not enough (as in, you dont have a 6' tall skimmer), you can increase the interface time. The more interface time = more interface area. The two would seem directly realated, no?
JC VT
New member
My understanding of Randy's POV is that it has nothing to do with stubborn proteins. More along the lines of "the time that the water hangs around getting blasted with bubbles." And not necessarily time either, but the simple fact that the more interface area water gets exposed to, the more organics are bound.
hahnmeister
In Memoriam
The idea or concept of interface area, by definition, is a function of time, wouldnt it be? I mean, as time increases, so do the bubbles. If the water velocity/throughput is manipulated to provide an ideal time for exposure, you are in effect manipulating the interface area with time, no?
sherm71tank
Premium Member
The impression I got was that skimmers that processed the highest volumes of water and air were better at removing proteins, I.E. Beckett. Not considering power consumption of course.
hahnmeister
In Memoriam
Not really. Just spitting out alot of water and air doesnt mean that they are able to interact. Becketts have a very short contact time, and where the air/water mix comes out is only right around the corner from the exit, so much of the water makes a B-line from the injector to the outlet. No counter-current, lots of turbulence, etc. But the more I think about how Randy explains it, the more it makes sense. Becketts are just very different than needlewheels.
And, FWIW, becketts dont necessarily have the highest throughput of air. A 40watt needlewheel can throw out 1000lph... something that you would need over 100watts to do with a Beckett.
The small notes in snailman's skimmer page, taken from escobal's book, set the record straight... more time in the skimmer = more molecules skimmed.
And, FWIW, becketts dont necessarily have the highest throughput of air. A 40watt needlewheel can throw out 1000lph... something that you would need over 100watts to do with a Beckett.
The small notes in snailman's skimmer page, taken from escobal's book, set the record straight... more time in the skimmer = more molecules skimmed.
JC VT
New member
Here's an interesting tidbit from Randy's article:
"If the bubbles are moving against the water's flow, or are in a turbulent environment, the required absorption time will be lower (because the flow helps bring organics to the interface) than if the bubbles are moving with the flow. "
"If the bubbles are moving against the water's flow, or are in a turbulent environment, the required absorption time will be lower (because the flow helps bring organics to the interface) than if the bubbles are moving with the flow. "
hahnmeister
In Memoriam
Yeah, he even goes on to suggest that a certain degree of turbulence is favorable... for better mixing.
I say counter current airstone driven are most efficient because:
1. they produce the finest bubbles which = most surface area
2. you can pump a lot of air into the water column this way
3. you can do it with the fewest watts.
But... ya gotta change those wooden stones regularly.
As Mr. Wilson pointed out, if "good enough" gets you there with a needle wheel that dosn't need changing, it dosn't neccesarily matter which is most efficient.
Fred
1. they produce the finest bubbles which = most surface area
2. you can pump a lot of air into the water column this way
3. you can do it with the fewest watts.
But... ya gotta change those wooden stones regularly.
As Mr. Wilson pointed out, if "good enough" gets you there with a needle wheel that dosn't need changing, it dosn't neccesarily matter which is most efficient.
Fred
mr.wilson
.Registered Member
You only need enough turbulence to spin the molecules around to attract the non-polar, hydrophobic end. Too much and you detach weakly bonded molecules.
Beckett skimmers have their time and place and work on a different principal, so the laws we've discussed here don't necessarily apply to them. They rely on an instant migration as water is fractionated. Downdraft technology creates weakly bonded, realatively unstable bubbles, so a rapid ascent is necessary. A surfactant and POC juggling act, manages to produce an impressive yield. I believe it was a beckett skimmer that won the skimmer comparison here at RC, but I haven't read the thread myself, so I can't qualify the results. Dr. Ron studied the contents of skimmate, but I don't think he elaborated as to what fractionation method was used.
http://reefkeeping.com/issues/2002-12/rs/feature/index.php
I use two huge beckett skimmers on coral systems in a retail store. They skim quite a bit. My only complaints are the injector noise and biweekly cleaning, and the fact that they go on strike if there's a heavy load or hands in the tanks. One of them has been off line for the past five days due to a new anemone shipment. Nothing skimmed in five days is bad news when you need them the most, but it's a situation unique to commercial systems. My experiences with becketts has been a wet foam, so the "bubble popping" principal of phosphate and nitrate removal is well represented.
Perhaps the answer is an assembly-line process, whereby, one technology (Beckett) is used for skimming certain "easy" agents (hydrophobic proteins), while another technology (air-driven) is used to remove the remaining "stubborn" hydrophilic proteins, heavy metals, DOC & POC.
Beckett skimmers have their time and place and work on a different principal, so the laws we've discussed here don't necessarily apply to them. They rely on an instant migration as water is fractionated. Downdraft technology creates weakly bonded, realatively unstable bubbles, so a rapid ascent is necessary. A surfactant and POC juggling act, manages to produce an impressive yield. I believe it was a beckett skimmer that won the skimmer comparison here at RC, but I haven't read the thread myself, so I can't qualify the results. Dr. Ron studied the contents of skimmate, but I don't think he elaborated as to what fractionation method was used.
http://reefkeeping.com/issues/2002-12/rs/feature/index.php
I use two huge beckett skimmers on coral systems in a retail store. They skim quite a bit. My only complaints are the injector noise and biweekly cleaning, and the fact that they go on strike if there's a heavy load or hands in the tanks. One of them has been off line for the past five days due to a new anemone shipment. Nothing skimmed in five days is bad news when you need them the most, but it's a situation unique to commercial systems. My experiences with becketts has been a wet foam, so the "bubble popping" principal of phosphate and nitrate removal is well represented.
Perhaps the answer is an assembly-line process, whereby, one technology (Beckett) is used for skimming certain "easy" agents (hydrophobic proteins), while another technology (air-driven) is used to remove the remaining "stubborn" hydrophilic proteins, heavy metals, DOC & POC.
JC VT
New member
Hi Mr. Wilson,
Randy HF addressed some of these comments
Here are some quotes (emphasis mine):
if it took a second or a minute or 5 minutes for the actual binding to the interface to take place, then contact time itself would be critical. That might happen for certain very complex proteins, but I do not believe that plays a dominating role in reef aquaria
The only other possible mechanism (that I know of) that would suggest that longer dwell time is useful is the time it takes a protein to become denatured (to change its three dimensional structure) and so to more fully adsorb to an air water interface. However, I think that once a protein adsorbs enough to begin to denature, it is probably stuck to the bubble and won't get away.
Found here: http://www.reefcentral.com/forums/showthread.php?threadid=961594
Randy HF addressed some of these comments
Here are some quotes (emphasis mine):
if it took a second or a minute or 5 minutes for the actual binding to the interface to take place, then contact time itself would be critical. That might happen for certain very complex proteins, but I do not believe that plays a dominating role in reef aquaria
The only other possible mechanism (that I know of) that would suggest that longer dwell time is useful is the time it takes a protein to become denatured (to change its three dimensional structure) and so to more fully adsorb to an air water interface. However, I think that once a protein adsorbs enough to begin to denature, it is probably stuck to the bubble and won't get away.
Found here: http://www.reefcentral.com/forums/showthread.php?threadid=961594
mr.wilson
.Registered Member
I believe the second half of Randys comment is in regard to #2 below. Therein lies the "stubborn protein".
Protein skimming doesn't only remove proteins, it also separates humic and phenolic compounds, organic acids, and toxic chemical compounds. We also need to agree that part of the proteins primary function is to remove excess trace elements. Randy made no comment with regard to their binding conditions. Perhaps these were omitted because they have the same reaction time and properties as proteins.
Randy may be right, and he certainly has the credentials to dispel what science has given us in the study of foam fractionation, but I believe his comments were admittedly speculative.
Rubin et al. (1963), proved that foam fractionation removes DOC by two mechanisms...
1) surface-active materials are absorbed physically at the surfaces of rising air bubbles in a contact column.
2) non-surface-active compounds may combine chemically with surface-active material and be collected.
Protein skimming doesn't only remove proteins, it also separates humic and phenolic compounds, organic acids, and toxic chemical compounds. We also need to agree that part of the proteins primary function is to remove excess trace elements. Randy made no comment with regard to their binding conditions. Perhaps these were omitted because they have the same reaction time and properties as proteins.
Randy may be right, and he certainly has the credentials to dispel what science has given us in the study of foam fractionation, but I believe his comments were admittedly speculative.
Rubin et al. (1963), proved that foam fractionation removes DOC by two mechanisms...
1) surface-active materials are absorbed physically at the surfaces of rising air bubbles in a contact column.
2) non-surface-active compounds may combine chemically with surface-active material and be collected.
JC VT
New member
Hello Mr. Wilson,
If non-surface-active compounds are combined chemically with surface-active material, this would not have anything to do with bubble dwell, correct? The rate limiting step would probably be the chemical reaction between the non-sa compound and the sa compound. I'd imagine once the non-sa compound were bound to the sa compound, we could treat the whole entity as a sa-compound.
If non-surface-active compounds are combined chemically with surface-active material, this would not have anything to do with bubble dwell, correct? The rate limiting step would probably be the chemical reaction between the non-sa compound and the sa compound. I'd imagine once the non-sa compound were bound to the sa compound, we could treat the whole entity as a sa-compound.
mr.wilson
.Registered Member
None of the books elaborate when the chemical bonding occurs; in the display tank on an ongoing basis, or in the skimmer in flux, as migration occurs.
Unfortunately, not much science trickles down to our hobby. Every significant aquarium author advises that a long dwell time and small bubble size are the key to efficient skimming. They reference a few studies from the water treatment sector, but don't tell us anything more than what we've discussed here already.
To complicate matters more, these laws don't apply to downdraft skimming. Ozone also changes the scenario, as it decreases bubble stability, but at the same time should be exposed to treatment water far as long as possible to avoid residual ozone off-gassing.
Randy Holmes Farley believes that it's a quick migration, and I'm sure his belief is founded in fact. His predecessors are all confident that it's a slow process. It's possible that everyone has been passing down bad information for the past 50 years. It won't be the first time we've all been collectively wrong. I'm gonna go with the mob rules on this one, until I hear of new experiments.
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