Skimming Principles

[crazzyreefer]

the bubble rise is at 1.17 or 3cm Clean... 2cm when its bonded with organics, so it throws another wrench in the mix, this is the whole piont, we dont want just clean bubbles to rise, so the 120 rule is also out the window... sorry, now the bubble still needs 120 seconds, but as it collects organics and oils, it will slow down, so if its a counter current model and it it slows down 1/3 of the rise rate the bubble will not enter the foam area.

[tinygiants]

In my modeling I am getting a water flow of .6 in/s. At a bubble rise rate of 2cm/s = .78 in/s. That would equate to corrected rise rate of .18 in/s

Why would this bubble (organics and all) not continue to rise?

Dale

[tinygiants]

Counter current skimmers usually have the inlet near the top but not above water line. The water will be counter current below the inlet and less directional above the inlet. The water speed will have less effect on the bubble at this point. So the bubble rise rate will slow down as it picks up organics and its overall rise rate will increase as it leaves the area of counter current influence.

If the spacing is worked out you could still have your cake and eat it too.

Dale

[crazzyreefer]

yes it would and it would also collectivly add to the Air ratio bumping it up past the 13% mark... ok lets think this through, you get the skimmer set up, your water isnt as clean and clear, so lets say your bubble rise rate is vary slow, and when you feed, even more organics enter the chamber, the air ratio goes through the roof... then it settles down again... the object isnt to have the fluctuation and a constant skimming, so how do you adjust air Automaticly? DO controller? redox Controller Orp controller? and how do you controll the air in the first place? adjusting the valve on a pump? can the funtion be done automaticly? cheaply?

[tinygiants]

I think the rise rate difference is really going to be insignificant compared to the other parameters.

The bubble rise is going to slow down on a curve. The bubbles at the top will be slower due to the load.

Skimmers by nature will not skim if the water is clean no matter how long the bubble sits. When we feed or medicate we are going to get skimmate.

I think I would sacrifice the efficiency for the time peroid that the skimmer recovers from feeding. I would accept slightly over 13% bubbles. We routinly accept < 13%. In fact i am not sure the average hobbyist has the ability to measure 13% bubble volume.

Dale

[crazzyreefer]

but the curve adjusts to the water quality... and a poor designed skimmer wont clean clean water... but made properly it will! and its at this end that a new skimmer principals might make all the difference in other parameters, we just dont know... its not tried or proven... foam area cleanliness is key to foam removal, if the skimmate breaks, it coat the side walls and becomes less efficient. lets have our cake...and eat it too...just come up with a way to adjust a air stone...could the skimmer have a float valve that operated on the buoyancy like a hydrometer and it controlled a air valve?

[crazzyreefer]

ok I read the article that you got the bombardment rate... and I believe escobal is flat out wrong on rule 3, the rest are accurate, but skimmer height does have an effect of bombardment rate , and rule 2 I just question... I bet the rules are meant to be simplistic, but at that point they are out of context. and no longer valid. again this is his theory, and can easy be disproved, he states a clean bubble rise only increases contact time not bombardment rate... contact time is bombardment... you can have a clean bubble rise without it further being bombarded! I wondered why you were confused... its rules are in a circle. and are contradicting to each other!

[Whaledriver]

Couldnt you measure a 13%bubble volume by the weight of the chamber before and with the foam? Just put a electronic bathroom scale under the skimmer and do the math.

This might help in tuneing and designing a recirculating skimmer. You can design it in therory but the variables change too much to predict it cost effectivly.

[crazzyreefer]

yes I can do it by weight! and a electonic model colud control a air valve!, ok I need my friends to start taking apart their scales... like they are not in enough trouble....


but this is compleatly workable, if not a bathroom model, a smaller electonic one.

ok water weights 8.33 lbs at 87% = 7.2471 Lbs

Thank you, this will work!

[Whaledriver]

Have you seen the DC motor on a needle wheel the Bubble King guy is testing? Very efficient. You could also use it with a speed controler that is regulated by the weight of the water in the chamber. Should be a simple control system with the right computer program.

This would create a skimmer that would warrent a premium price as value added product. Some other premium skimmers dont seem to warrent the premium

[crazzyreefer]

problem is the needle wheels recirculate the water/air mixture, which strips the organics.

on a different note can a air molecule attract a phoshore molecule or a nitrate molecule, I was reading that in waste management this is one of the primary ways of stripping phosphates out of waste water prior to reuse. ChemE?

[ChemE]

Wastewater isn't my forte, but I'll do some checking.

The bathroom scale idea is workable in theory but I doubt very very much that a bathroom scale is anywhere near precise enough to measure a few grams difference on something that weights 30-40 lbs. Sorry to rain on the parade. An optical sensor that measures water/foam interface height might be a better method.

[Pyrrhus]

ever thought of batch processing the water? I.E. every 2 minutes pump the skimmers volume in water into the skimmer and leave it to react for 2 minutes.

[tinygiants]

Well I got sick and tired of a messy worksheet. So I made Version 3.

This version will calculate the air volume required to meet the 13% Saturation.
It does all of the messy conversions on the fly (cubic inches - gallons, GPH - GPM, and so on).
It calculates water dwell time taking into consideration the volume of air in the skimmer.
Bubble dwell is calculated for a counter current skimmer.
For those that employ a recirc pump on the skimmer body, it calculates the recirc effect on the bubble and associated times.

While calculating this I found it interesting that the airpump does not need to be a brute if you keep the bubble suspended in the water column.

Let me know if you find any errors in my calculations.

Dale

[crazzyreefer]

recirculation rate isn't correct, the common misconception including escobal, is that the water recirculating isn't stripping the organics that hold the bubble stable, so where you have 3min its 70 sec this is the biggest problem with the skimmers that are on the market, except maybe RK2, but its because of lack of proper insight, and or the limitations of cabinet height/mass marketing that forces them to build a poor product. bulk batching wouldn't work, due to stripping. look at wet drys systems, I was on the leading edge 20 years ago designing them, there was a couple in the mid west, and a Swiss group, and even though I had a hand in the design I realize it was poor design, but it still sells today. another problem you have is your 3 inch tube, go larger, you are creating a lot of turbulence with 3 inches, again stripping... but hay this calc is easier to read...

[barryhc]

Originally posted by ChemE
Wastewater isn't my forte, but I'll do some checking.

There are some good links in this thread, for wastewater processes, and associated bacterial phosphate processing studies. One of the last links describes a new single vessel Aerobic to Anaerobic and back cycle that is much simpler than current technology.

Most experts believe that Nitrate and dissolved Phosphate processing can only be accomplished by the Aerobic to Anaerobic process.

http://reefcentral.com/forums/showth...6&goto=newpost

I hope the links are helpful.

Happy Reef Keeping > barryhc

[crazzyreefer]

I dont trust optical sensors in a skimmer due to all the organics, no a bathroom scale wouldnt work well for a small skimmer, but I have many scales here that are fine tuned and measure ounces from 50 lbls, but most larger skimmers have 20-30 lbs differances so on that part a scale that measured every 1-2 lb would work.

[crazzyreefer]

heterotrophic active biomass removes the phosphates, the higher the concentration of liquor, (organic solids) the higher the rate of Phosphate removal.

[tinygiants]

Originally posted by crazzyreefer
recirculation rate isn't correct, the common misconception including escobal, is that the water recirculating isn't stripping the organics that hold the bubble stable, so where you have 3min its 70 sec this is the biggest problem with the skimmers that are on the market, except maybe RK2, but its because of lack of proper insight, and or the limitations of cabinet height/mass marketing that forces them to build a poor product. bulk batching wouldn't work, due to stripping. look at wet drys systems, I was on the leading edge 20 years ago designing them, there was a couple in the mid west, and a Swiss group, and even though I had a hand in the design I realize it was poor design, but it still sells today. another problem you have is your 3 inch tube, go larger, you are creating a lot of turbulence with 3 inches, again stripping... but hay this calc is easier to read...

Ok - I think you are misunderstanding the design plan I based this on.

The recirc rate will be seperate from the feed. It is measured in GPM, not seconds. In order to achieve enough water velocity to slow the bubble down I had to add it. If I just speed up the feed rate, I sacrifice the water dwell time (while the bubble dwell would be ok). The water being recirced will be collected from the same area as the skimmer overflow outlet. Very few bubbles should be pulled through the recirc line.

The water dwell calculation is based on feed rate only. It does not include the recirc.

The water velocity calc adds the feed rate and the recirc rate for combined feed rate to use in the calc.

Does that answer the concern? Or do I still have a error.

Dale

[duhfactor]

This makes more sense to me. I looked through your calculation spreadsheet tinygiants, and it seems to work. I'm going to hold off of the inclined skimmer design for now, I like where this is going.....



D

[crazzyreefer]

nope thats the same as that convection type.. makes sence, one number that isnt in your cals is bubble rise it needs to be between .40 and 1.17 if you got this...you got it...other wise it will be sucked like a vaccume when the organics attach. was 60 inches just your liquid chamber part, how long of a foam area? you have the design right! see,,,,now... this is where the manufatures do not even start to make it work correctly.... way to go!

[crazzyreefer]

Question, what is the phosphate and nitrate levels of the skimmer effluent, if its off the chart, use rodi water to dilute by 10X and please post your results, this will give to different answers, either its not removing them, or they are being neutralized as the waste management seems to express.

[tinygiants]

60 inches is the liquid chamber.

Why does the bubble rise rate need to be between .40 and 1.17? As long as the rise rate is greater than the water velocity, the bubble will maintain positve boyancy. The bubble will not achieve maximum organic bonding till it is reaching the top of the water column anyway.

I am planning to buy a 6" PVC Pipe and either a 4" or 3" foam riser pipe. I was going to experiment with the foam pipe length as well as maybe a wetneck.

[crazzyreefer]

since we are removing multiple types of organics, not all bond at the same time, same way, and affect bubble dwell differently, Maybe I'm wrong... this part isn't proven, nor suddied in depth. but if you can keep you numbers in this range you wont have a potential issue. so what is your bubble rise?

[tinygiants]

.489 inches/second is the corrected bubble rise rate.