Skimming Theory

Mogrash · #1 03/08/2007, 11:15 AM

I understand the concepts and physics behind skimming. Proteins and lipids collect at the water/air interface.

This is all fine and dandy for hydrophobic proteins that float, but what about hydrophillic proteins? I would tend to think they will not be collecting at the surface and would not be efficiently removed by skimmers. Is there something I'm missing?

billsreef · #2 03/08/2007, 03:51 PM

Some carbon will take care of what the skimmer doesn't

barbra · #3 03/08/2007, 04:19 PM

A skimmer removes that which is not water-soluble, it can't do much for things that bind with water and won't ride the surface.

Mogrash · #4 03/22/2007, 11:00 AM

Barbara, I know that. I'm asking how are we removing all the waste that can't be exported by skimmers. Hydrophobic waste is likely a small amout of the total waste produced as most proteins are hydrophillic.

Billsreef, how is carbon going to remove all the hydrophillic proteins that a skimmer can't remove? If that was the case the carbon should look like a cesspool. Seems more likely that these are just uptaken by algae and bacteria. If so, wouldn't that make other exports of waste besides a skimmer critical, if not more important than a skimmer? Just pondering...

billsreef · #5 03/22/2007, 12:24 PM

Indeed my answer was a bit too simplistic. Yes, carbon will remove some but probably not all. It will still be a significant amount and if you don't change your carbon often enough it will end up like a cesspool

Water changes will remove some and also many of the biological process going on in the tank will utilize a great deal of it.

Ninong · #6 03/22/2007, 12:45 PM

Quote:

Originally posted by Mogrash
This is all fine and dandy for hydrophobic proteins that float, but what about hydrophillic proteins? I would tend to think they will not be collecting at the surface and would not be efficiently removed by skimmers. Is there something I'm missing?

I think what you may be missing is the fact that the proteins and other dissolved organics that can be skimmed out of the water column are bipolar molecules (hydrophillic and hydrophobic).

Shane Graber discusses this concept in detail here.

Mogrash · #7 03/22/2007, 01:50 PM

Ninong: No, I'm a not missing that. However, the majority of proteins in their natural conformation are not bipolar as a molecule (although all proteins contain some hydrophobic and some hydrophillic amino acids). Yes, membrane bound proteins will have a hydrophobic portion that is embedded in the lipid bilayer but those proteins would naturally be ideal candidates for the protein skimmer. The most abundant proteins are all hydrophillic, at least in their non-denatured state. Afterall, most proteins are interacting in an aqueous environment. I don't know Shane's background so I'm unsure if he has scientific data backing this up or making some assumptions from a limited background...

Mogrash · #8 03/22/2007, 01:57 PM

Quote:

Originally posted by billsreef
Indeed my answer was a bit too simplistic. Yes, carbon will remove some but probably not all. It will still be a significant amount and if you don't change your carbon often enough it will end up like a cesspool Water changes will remove some and also many of the biological process going on in the tank will utilize a great deal of it.

In that case, why skim at all since potentially the majority of proteins will not be skimmed out, while lipids and other organic molecules will? Would water changes and carbon be more economical vs skimmer electricity? Or large refugiums/scrubbers?

I mean, I have noticed that if I let detritus sit in my sump for a bit my skimmer eventually starts pulling out gobs and gobs of skimmate. If I siphon out the detritus it severly cuts down the amount of gunk the skimmer is pulling out. That alone makes me wonder just how efficient these things are.

Ninong · #9 03/22/2007, 02:14 PM

Quote:

Originally posted by Mogrash
I don't know Shane's background so I'm unsure if he has scientific data backing this up or making some assumptions from a limited background...

If you mean his day job, he's a chemist. He's also on the editorial staff of an online reefkeeping magazine on another reefkeeping bulletin board.

P.S. -- In his Reef Central profile, he gives his occupation as "industrial chemist."

Mogrash · #10 03/22/2007, 02:26 PM

Hrm. Industrial chemist. Ninong, do you know if anyone has done some actual science behind skimmers?

Ninong · #11 03/22/2007, 03:04 PM

Quote:

Originally posted by Mogrash
Hrm. Industrial chemist. Ninong, do you know if anyone has done some actual science behind skimmers?

What do you mean by "actual science?" Do you mean a quantitative and qualitative analysis of the skimmate or a scientific review of the mechanics involved?

There are several hobby level articles that have been written on protein skimmers over the past decade or so. They are discussed in Delbeek & Sprung (1994, 2005) and in Fossa & Nielsen as well as several articles in the various online reefkeeping magazines.

http://www.reefkeeping.com/authors/rhf.php] Dr. Randy Holmes-Farley[/url] (V.P. Research, Genzyme, and moderator emeritus of Reef Central's Chemistry forum) has written an article on skimming.

Dr. Frank Marini (a biochemist/microbiologist), has written an article on skimming.

Several people have performed analyses of skimmate. Dr. Ron Shimek has done some work in this area and Eric Borneman, a Ph.D. candidate at the University of Houston, discusses this topic in this thread on another board.

Mogrash · #12 03/22/2007, 03:06 PM

I read some papers on protein separation with foam. Quite complicated stuff.
If someone is interested this is what I got out of it:
1)the water-air interface can denature some proteins
2)extent of denaturing is very variable even between hydrophillic proteins
3)low pH apparently helps the interaction
4)charge of the protein also changes separation ability

all of this is due to the sequence of amino acids and the secondary and tertiary structure of the protein.

Mogrash · #13 03/22/2007, 03:08 PM

Quote:

Originally posted by Ninong
What do you mean by "actual science?" Do you mean a quantitative and qualitative analysis of the skimmate or a scientific review of the mechanics involved?

Yes to the first, maybe to the second if they provide references. Thanks for the links!

Ninong · #14 03/22/2007, 03:13 PM

Quote:

Originally posted by Mogrash
Yes to the first, maybe to the second if they provide references. Thanks for the links!

I edited my post to add a couple more links.

I'm not sure if I can find links to the skimmate analyses but I'll look around a bit and see what I can find.

Ninong · #15 03/22/2007, 03:22 PM

OK, here you go: Skimmate analysis by Dr. Ron Shimek

Mogrash · #16 03/22/2007, 03:49 PM

Hrrm, Randy's article is good on how skimming works (which I understood) but a bit unclear on how much total protein/lipids is actually removed. At face value I would tend to say most proteins are not removed based on his 'hydrophobic' comment.

If you look at Eric's thread. While interesting it hasn't gone beyond the 'quick and dirty' science yet. What strikes me is the size of the particulate matter. While it could be massive protein/lipid aggregates the micron size of the stuff is way way above single cell size.

Shimek's analysis was great for chemicals, a bit weak for organic info. Especially, given how some of the key aspects are missing. It also doesn't discuss what is left in the water vs what is skimmed out-which is really the question I have.

I admit I read these articles quickly (at work!). Will try to go over this some more. Wish I had an extra skimmer-I could quite easily measure protein concentrations in water skimmed vs not skimmed.

billsreef · #17 03/22/2007, 06:13 PM

Quote:

Originally posted by Mogrash
Wish I had an extra skimmer-I could quite easily measure protein concentrations in water skimmed vs not skimmed.

If you got the means to make those measurements, perhaps just simply measuring your tank water where it enters the skimmer and again where it exits, might provide some interesting data. I've got a hunch this could get quite interesting

Mogrash · #18 03/22/2007, 06:58 PM

Well, it wouldn't be a very controlled experiment. Need to think if it would work properly.

Assuming the saltwater itself will not interfere with the reaction it would be quite easy to do. I measure protein concentrations all the time before I do a Western Blot. I guess I need to decide how I should treat the sludge/skimmate. Do I need to lyse the samples? Sonicate them, etc... Should I prefilter it much like Eric is doing?

Speaking of protein, time to go cook some steaks! be back in a bit

Mogrash · #19 03/22/2007, 07:20 PM

Hrrmm...
Well measuring my tank water and skimmate wouldn't tell us what type of proteins are being removed, but it might be interesting nonetheless. At least we would know total export of proteins. Time to go clean my skimmer as I don't remember when I last cleaned it.

And why haven't you done this yet billsreef? You are a marine biologist...

billsreef · #20 03/22/2007, 08:44 PM

Quote:

Originally posted by Mogrash
And why haven't you done this yet billsreef? You are a marine biologist...

Need to be a bit more of a chemist for that stuff

Besides, if I started buying up the stuff needed for that type of testing, I'd need to find a good excuse to explain it all to my boss

Mogrash · #21 03/22/2007, 09:40 PM

Well, I read through Eric's thread in full. Seems interesting, but I'm not sure how valuable it will be without looking at CNP, or at least protein levels. Guess we will have to wait for his article.

Ozone seems to break down the larger matter into smaller pieces-which would be expected. Whether it actually helps remove a higher % of waste can not be determined from his current samples (unless he hasn't listed some).

Ideally, it would be nice to have a tank with just saltwater freshly madeup. Add known weight of pellet food or flake food(something dry with no water). Use powerhead for circulation, seal tank, add hepa filter on skimmer air intake. Skim until no visible food is in water, collect waste at multiple intervals and check dry weight. Then check protein concentration of water and skimmate.

Then, take tank water from a reef system (has bacteria and algae). Repeat above experiment.

The way he is doing it contains a lot of variables...

Hrm, I do have an old crappy marineland skimmer. Wonder what I did with the powerhead that goes to it...

davidryder · #22 03/23/2007, 08:52 PM

Why am I reading this thread?!

Mogrash · #23 03/23/2007, 11:00 PM

Because you live in Ohio?

davidryder · #24 03/23/2007, 11:18 PM

Quote:

Originally posted by Mogrash
Because you live in Ohio?

LOL

lovethereefer · #25 03/24/2007, 10:42 AM

In a reef setting I think the fact that some organics are needed has been overlooked. The corals and other filterfeeding organisms uptake organics at a high level. Although I think it would be interesting to know what is actually being removed by the skimmer I think it is a moot point. While certainly the skimmer pulls out organics it adds a lot of DO back to the tank that it couldnt get on surface area alone. This will add a bit of stability to the tank w/out the pH swings that we would experience w/out it (not including running your fuge on a reverse lighting cycle). I do have a question though, if you are running ozone in huge skimmer and there was still a lot of organics making it through the skimmer, what else could be done to break down the organics? If ozone can't break down the organics in combination with the skimmer what else could do it besides the metabolic pathways of corals and other filter feeders as evident w/ Steve Tyrees operation. My take on skimmers is that it provides stablity to the tank and removes just enough organics as to not starve corals but to not allow nuissance growth of unwanted algaes. With the protein skimmer I think that the hydrophilic proteins are removed by the change in shape revealing the hydrophobic portions that RHF suggests. That would be the most logical answer to me. The organics that can't change shape could be taken up by corals, algaes, ect in metabolic pathways. I could be totally wrong though.....