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#103202 - 12/10/07 04:20 PM thoughts on air stone diffusers & piston comp.
JMAC Offline
Lunker

Registered: 11/27/07
Posts: 110
Loc: MI
I've always thought that dual piston compressors are quieter and more reliable, though all I see on here are threads about rotary vane. Can anyone spell out which is better? Same goes for air stones vs. membranes.
_________________________
Justin McLeod
If you don't know where to start, go back to the beginning.

jmcleod@thepondguy.com
http://www.thepondguy.com


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#103211 - 12/10/07 05:01 PM Re: thoughts on air stone diffusers & piston comp. [Re: JMAC]
Sue Cruz Offline
Ambassador
Lunker

Registered: 12/22/04
Posts: 709
Loc: Pompano Beach, Florida
Hi Justin -
We prefer pistons at Vertex and have been using them for about 4 years. Previously we used vane compressors but we ran into some problems and limitations. The piston compressors can operate at a much higher PSI so you can use them in deep water and with long tubing runs. They don't require maintenance as often as the vanes do and don't have the problem of sucking water into the compressor. Vanes can put out more CFM, though, and if you have a shallow water application they may be preferable... If the vanes run at a lower PSI you won't have to change the vanes so often.
Discs vs. stones... Stones can clog up quickly and cause back pressure on the compressor - not good when combined with a vane compressor! You will cause the compressor to run harder, and increasing the PSI. I can go on and on, but I must go.... I'm sure plenty of folks will put in their 2 cents.
_________________________
Sue Cruz
Vertex Water Features
www.vertexwaterfeatures.com


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#103238 - 12/11/07 09:07 AM Re: thoughts on air stone diffusers & piston comp. [Re: Sue Cruz]
Theo Gallus Offline
Moderator
Lunker

Registered: 05/14/04
Posts: 12394
Loc: Central Ohio
IIRC diffusers produce more and smaller bubbles than airstones - a more efficient aeration use of your available air supply.
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"Live like you'll die tomorrow, but manage your grass like you'll live forever."
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#103242 - 12/11/07 09:43 AM Re: thoughts on air stone diffusers & piston comp. [Re: Theo Gallus]
JMAC Offline
Lunker

Registered: 11/27/07
Posts: 110
Loc: MI
From my schooling, the largest and most efficient source of aeration is at the surface interface... And i've seen studies involving bubble size with aerators, showing that larger bubbles (with air stones) move more water. I have always thought that the most efficient circulation, not aeration, of the pond is the best way to go. Also, I've had problems with "self cleaning" membranes in that you need a compressor to push 3-4 times the air volume to inflate the membranes to clean them. I feel that can be an expensive option when looking for compressors. As far as stone clogging, I haven't had enough problems with them to warrant a change. Thoughts?
_________________________
Justin McLeod
If you don't know where to start, go back to the beginning.

jmcleod@thepondguy.com
http://www.thepondguy.com


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#103254 - 12/11/07 11:34 AM Re: thoughts on air stone diffusers & piston comp. [Re: JMAC]
Cary Martin Offline
Ambassador <br /> Field Correspondent
Lunker

Registered: 11/24/04
Posts: 551
Loc: Mooresville, NC
Here at Aeration Technologies, we use piston compressors to. Sue did a great job explaining the differences to you. I know you have used stones for a while now Justin and at the time, they were the "Cats Meow". With the new membrane technologies out there, psi can be overcome.

For example our tube diffusers only require 0.25 cfm to allow bubbles from the entire tube 360 degrees around it for a total of 1 cfm for each AirPod. It is all in the design of the membrane. How many holes, how far apart, the thickness of the membrane etc. Vertex has done the same homework with their disc-style diffusers.

What the common pondowner does not see is the money spent by Aeration Technologies, Vertex, Aquatic Eco and energy spent studying the effects and results by people like Ted Lea and Theo, to ensure the set up of the system is right before it arrives to the pond user.

As I can see with your replys Justin, there is much more to aeration than just simply "making bubbles"!

As for stone clogging, I have removed my share of clogged stones to know there are more problems than you are aware of. Most pondowners are not going to remove the diffuser if it is creating some sort of bubbles much less know if they are small bubbles or large bubbles. Therefore we must design a system that will be as maintenance free as possible and as efficient as possible.
_________________________
Cary Martin
http://i36.photobucket.com/albums/e4/martincv123/fishfight.gif[/IMG]

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#103259 - 12/11/07 01:50 PM Re: thoughts on air stone diffusers & piston comp. [Re: Cary Martin]
WaterWizard Offline
Lunker

Registered: 11/08/07
Posts: 227
Loc: San Luis Obispo, CA, USA
I agree, dual piston oil-less air compressors are the way to go. As for the diffusers; one thing to realize is that all pond aeration devices are adopted from a waste water treatment application. Diffusers such as air stones, flex membrane disks, ceramic diffusers, etc... are used in a waste water treatment process called "mixed liquor" in which the sediments of the treatment cell are agitated or "mixed up" for oxidation. This mixing is a result of an un-controlled release of air which creates turbulent flow. It is easy to see how this process could potentially stir up nutrient rich bottom sediment in a pond application, and it does.

Although many companies have tried to offset this mixing effect by propping up the diffusers, this actually defeats much of the benefit of bottom laid diffusion in that aeration only occurs from the point of bubble rise. This means that there is still a thin anaerobic layer of water at the very bottom of the pond where the nutrients are still soluble, available for algae growth, and not being consumed by aerobic bacteria.

There is however another solution in bottom laid aeration tubing with laminar flow. Laminar flow is achieved through a controlled release of air that is not turbulent, sits directly on the sludge/water interface and will not disturb the bottom sediment. This type of tubing also achieves higher Standard Oxygen Transfer Efficiency (SOTE) which is a ratio of oxygen deliverd per unit of energy (usually horse power). This is what you want to look for in any type of diffuser as it is a true measure of the efficiency of the system. Furtheremore, this tubing will typically not clog unless you have high levels of dissolved metals in your source water. The life expectancy of the tubing is 20 years without maintenance. I would recommend reconsidering your choice of diffusers.
_________________________
Richard Dennis
EP Aeration
rich@epaeration.com
www.epaeration.com
(800) 556-9251


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#103261 - 12/11/07 02:38 PM Re: thoughts on air stone diffusers & piston comp. [Re: WaterWizard]
JMAC Offline
Lunker

Registered: 11/27/07
Posts: 110
Loc: MI
I would like to see any of these documented cases, as I have only seen air stones and membranes in action. Of course we are all sticklers for our own "tried and true" methods. The tubing is very interesting... how about a cost-effectiveness analysis between the three?
_________________________
Justin McLeod
If you don't know where to start, go back to the beginning.

jmcleod@thepondguy.com
http://www.thepondguy.com


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#103262 - 12/11/07 03:04 PM Re: thoughts on air stone diffusers & piston comp. [Re: WaterWizard]
Cary Martin Offline
Ambassador <br /> Field Correspondent
Lunker

Registered: 11/24/04
Posts: 551
Loc: Mooresville, NC
Richard,

I would like to be on record stating that all types of aeration have their place. Deep water, shallow water, canals, cold water, deicing and even hypolimnetic and not to forget the ozone technology.

We have found using our diffusers positive ORP readings after installation, 2-3 mg/l oxygen levels in the "slurry/water" interface and orthophos readings below detectible levels once ORP was met. I think I speak for Vertex as well saying they have experienced the same results.

Yes the goal in wastewater is to stir the liquor to increase oxidation, but they are using blowers capable of 200cfm +, our compressors are only capable of 8.8cfm maximum. A big difference in the volume of air. We also use regulating valves to control the flow to each diffuser and not an "un-controled" release of air.

These diffusers are being used in a different application to gently circulate the entire water body and not "violently" create turbulent water flows. When diffusers that are designed and sized properly and not over or worse, undersized, the nutrients will be locked up in the sediments.

SOTE is a great measurement for individual diffuser performance, but it can not be the only limiting factor in making an informed decision on what type of diffuser to use. We use gpm and turnover rates because that is a number that most are familuar with. We do keep the OTE as a design perameter when sizing systems.
_________________________
Cary Martin
http://i36.photobucket.com/albums/e4/martincv123/fishfight.gif[/IMG]

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#103263 - 12/11/07 03:08 PM Re: thoughts on air stone diffusers & piston comp. [Re: Cary Martin]
Cary Martin Offline
Ambassador <br /> Field Correspondent
Lunker

Registered: 11/24/04
Posts: 551
Loc: Mooresville, NC
Justin, I agree on the comparison.

How about this:

5-acre lake
15 feet deep
Round in shape
115v power available
_________________________
Cary Martin
http://i36.photobucket.com/albums/e4/martincv123/fishfight.gif[/IMG]

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#103264 - 12/11/07 03:36 PM Re: thoughts on air stone diffusers & piston comp. [Re: Cary Martin]
JMAC Offline
Lunker

Registered: 11/27/07
Posts: 110
Loc: MI
My typical install for that lake would run $4-5 thousand. I cant put any fancy numbers to it but have taken temp & DO's in similar lakes showing destratification. That is our goal. Circulation of the lake introduces the most water to the surface. As far as uncontrolled, I have never seen a pond go from clear to turbid following an install. I would call a constant rate of air through a non-moving diffuser a controlled air application, especially once turnover begins.
_________________________
Justin McLeod
If you don't know where to start, go back to the beginning.

jmcleod@thepondguy.com
http://www.thepondguy.com


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#103265 - 12/11/07 03:56 PM Re: thoughts on air stone diffusers & piston comp. [Re: JMAC]
JMAC Offline
Lunker

Registered: 11/27/07
Posts: 110
Loc: MI
thats about $58/month to run too
_________________________
Justin McLeod
If you don't know where to start, go back to the beginning.

jmcleod@thepondguy.com
http://www.thepondguy.com


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#103266 - 12/11/07 04:22 PM Re: thoughts on air stone diffusers & piston comp. [Re: JMAC]
Cary Martin Offline
Ambassador <br /> Field Correspondent
Lunker

Registered: 11/24/04
Posts: 551
Loc: Mooresville, NC
We would be about $1800-$2200 depending on cabinet style and tubing requirments. Electric would range from $25/mo to $35/mo.
_________________________
Cary Martin
http://i36.photobucket.com/albums/e4/martincv123/fishfight.gif[/IMG]

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#103267 - 12/11/07 04:38 PM Re: thoughts on air stone diffusers & piston comp. [Re: JMAC]
Cary Martin Offline
Ambassador <br /> Field Correspondent
Lunker

Registered: 11/24/04
Posts: 551
Loc: Mooresville, NC
We would be about $1800-$2200 depending on cabinet style and tubing requirments. Electric would range from $25/mo to $35/mo.
_________________________
Cary Martin
http://i36.photobucket.com/albums/e4/martincv123/fishfight.gif[/IMG]

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#103269 - 12/11/07 06:42 PM Re: thoughts on air stone diffusers & piston comp. [Re: Cary Martin]
WaterWizard Offline
Lunker

Registered: 11/08/07
Posts: 227
Loc: San Luis Obispo, CA, USA
Cary & Justin, First of all I just want to say that I am not trying to step on anyones feet. I am simply sharing information. I agree that all types of diffusers have their applications depending on site conditions, budget, goals, etc...For instance, course bubble flex diffusers tend to work better for ice melting. And of course number of turnovers per day is a major part of the design of an aeration system. My point is that whereas flex membrane diffusers, air stones, and others are designed specifically to mix the water and sludge, (even though this can be somewhat checked by adjusting pressure and or elevating the diffusers) the particular tubing that I speak of is specifically designed not to mix at any reasonable flow rate. As for the term "uncontrolled" release of air. I simply mean that the bubbles do not follow a laminar flow. I have experienced on several occasions when these flex diffusers were turned on they released large plumes of anaerobic sediment from the bottom creating a fowl odor and subsequent algae bloom. But as you mentioned Cary, this could be do to too much pressure. I'm glad to hear that you are aware of your SOTE as several other aeration companies I have spoke with cannot tell me their numbers. By the way, we get 3% per foot with the specified SCFM (.015-.08 CFM/Ft depending on type of tubing)and can circulate more than 20 million gallons per day with 1/3 horse power.

Justin, these numbers were derived by studies done by Dr. Michael Stenstrom of UCLA who is the chairman of the EPA for Oxygen Standards. As far as cost goes, the tubing is generally more expensive. However, when you consider that you are getting more turnover and oxygen transfer with less power, the reduced operation costs typically meet the difference in capital costs with 5 years. In addition, the tubing typically never requires maintenance unless there is high dissolved metals in your water. The tubing usually lasts at least 20 years. As for some documentation check out the following link.

http://www.agr.ca/pfra/pub/aerat51b.htm

Cary, out of professsional curiosity, when you design your systems, how many turnovers do you look for per day? We usually shoot for 5-15 depending on the size of the water feature and goals of the customer.
_________________________
Richard Dennis
EP Aeration
rich@epaeration.com
www.epaeration.com
(800) 556-9251


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#103270 - 12/11/07 07:00 PM Re: thoughts on air stone diffusers & piston comp. [Re: Cary Martin]
cde Offline
Fingerling

Registered: 12/05/07
Posts: 1
Loc: florida
I have 1/2ac. pond ranges from 4' to 13' in center. Pond is less than 2yrs old this summer had a lot of grass and algae. Pond is in central FL ground water no run off entering pond. What system would be best for me?
CDE

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#103325 - 12/13/07 02:15 PM Re: thoughts on air stone diffusers & piston comp. [Re: cde]
JMAC Offline
Lunker

Registered: 11/27/07
Posts: 110
Loc: MI
Water Wizard, how would I go about measuring SOTE? Are you measuring the O2 in the air going into the lines or are you measuring the change in DO throughout the water body. Also, How do you figure turnovers?
_________________________
Justin McLeod
If you don't know where to start, go back to the beginning.

jmcleod@thepondguy.com
http://www.thepondguy.com


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#103335 - 12/13/07 03:42 PM Re: thoughts on air stone diffusers & piston comp. [Re: JMAC]
WaterWizard Offline
Lunker

Registered: 11/08/07
Posts: 227
Loc: San Luis Obispo, CA, USA
Change in DO throughout the water body. The 3% that I quoted is for clean water. Generally we deflate this number for "dirty" water by multiplying by 0.66. This is a waste water calculation which gives us a true SOTE of about 2%. Pond & lake water is not nearly as "dirty" as waste water (I hope) so the SOTE is somewhere between 2-3% depending on the quality of the source water. I have video footage and documentation of the test. If you are interested I can send you a CD/DVD.

As far as turnovers go; if you are asking me how to derive this number it's simply pumping rate per 24 hours divided by total volume. However, I think you are asking me how to derive the pumping rate. This is done by an extensive and complicated set of waste water calculations but is generally a function of bubble size, rate of rise, and flow pattern. Basically, a whole bunch of small bubbles moving in a laminar flow will move more water than fewer large ones moving in a "turbulent" flow. When I say tubulent I mean a lot of horizontal movement, relatively speaking.
_________________________
Richard Dennis
EP Aeration
rich@epaeration.com
www.epaeration.com
(800) 556-9251


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#103336 - 12/13/07 03:48 PM Re: thoughts on air stone diffusers & piston comp. [Re: WaterWizard]
WaterWizard Offline
Lunker

Registered: 11/08/07
Posts: 227
Loc: San Luis Obispo, CA, USA
CDE, if you want to contact me personally, we can talk about your options based on your goals, etc..
_________________________
Richard Dennis
EP Aeration
rich@epaeration.com
www.epaeration.com
(800) 556-9251


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