Hybrid venturi/vortex aeration system for RDWC

[SuperiorBuds]

I was staring at all of my different airstones and diffusers the other day and I thought – I really should do a comparison of these to see which one works the best at aerating the reservoir. Unfortunately I don’t have a DO meter right now so I started looking around to find one.

Any suggestions, @Northern_Loki? Cheaper is better but I would take accuracy over cost.

I also have my venturi from my E&F setup so I could do a good side by side by side comparison. I’d love to see time to total saturation for each of these so we could truly compare. I know the venturi worked well for me last time, but there’s more data to consider here and I’d love to see it all.

[beacher]

A friend has used a similar but more basic system for years. A water pump circulating the res. The intake line for the water pump sits on the bottom and has a small tube branching off that goes above the surface to get air.

I wouldn’t say it makes a vortex, but a ton of air gets in there very simply and cheaply.

Interesting design!

[ATM]

Um. Wow. Just to take the effort to do this. Now just do a run in each of these scenarios and see how it affects yield. Haha. Just kidding…good work.

[Northern_Loki]

@slain

So in your plot ‘air’ indicates the active venturi?

Yes, correct. The venturi, in this case, is nothing more than some polypropylene tubing jammed into the pump feed line with a value to meter the air inlet. I need to construct something better than just a tube.

@slain

given it’s going to hold the same amount of oxygen regardless of the aeration method

Part of what I was trying to evaluate was whether we could super-saturate the DO. From the trials, I did see positive signs of super-saturation on the order of several percent. But this needs to be re-evaluated carefully as I also saw some conflicting/confounding measurements (as can bee seen in the graph trends).
Yes, it is possible to achieve >100% saturation using active methods. Which techniques to use, and within our grasp, to achieve that is the question. The extreme end is nano-bubbles that collapse in solution under pressure achieving a DO that is much much greater than 100%.

@slain

it’s not like there is much of a lag in oxygen uptake even

@slain

it’s hard to see how this won’t function every bit as well as any air pump

I agree, I think other mechanisms will easily compete with airstones. And, could end-up being less costly along with other benefits.

So, for those graphs, they have a fairly long time scale. When the venturi is allowing gas into the system, I was seeing about 30 minutes to fully saturate 40 gallons of solution. It is fast relative to fluming (air off). We need some other experiments to see if there is actually any merit here versus vortex, airstones/air pump, waterfall, etc, etc…

@slain

I am thinking I might have a crack at making some in Inventor and 3d printing them out.

Very interesting. Looking forward to seeing how this works.

@slain

II found a reasonably good technical paper on the "analysis on the effect of venturi tube structural parameters

That is awesome, I need to study this. Thank you.

[Northern_Loki]

Data geeks unite!

So for DO probes, there are two primary types. Polarmetric and luminescent(LDO). The preferable type is luminescent. Polarmetric is touchy, sensitive to solution velocity, and drifts. But, it also the least expensive.

What I have is a Hatch LDO probe along with a Hach meter. Their stuff is very expensive although, by being patient, these can be had via Ebay. I ebay’ed a used LDO probe and simply purchased a new LDO “cap”. From what I recall, I was able to get the probe for ~$100, the replacement cap ~$100, and the meter for ~$200. So, yeah, even used it is pricey. If you are willing to spend some sweat equity, industrial meters/probes can sometimes be had on the cheap.

A polarmetric Milwaukee DO probe + meter are available for under $200. There are downsides to the polarmetric method but may be perfectly suitable depending on how it’s going to be used.

For on-line process, the newest generation of LDO require no calibration ($$$), Hach LDO® Model 2. But, money to burn?

For what I’m doing, the probe needs to stay stable for long periods of time while submersed. LDO is better for that. And, I can say that DO probes in general are a bit tricky to use/understand in practice.

@SuperiorBuds

I’d love to see time to total saturation for each of these so we could truly compare.

That would be excellent. If we can get folk with various set-ups measuring the DO %, rates, plants in-situ / ex-situ, we’ll have data that well exceeds what is currently available on the interwebs.

Understanding, measuring this is fairly difficult and expensive. It requires a certain amount of data geeky-ness to get sensible results. Right now, viewing the past experiments available from other sources, I feel their results may be a bit “misleading” as they avoid looking at things like saturation rate, etc. A comparison using an improved experimental methodology would be valuable.

[Indiva710]

If someone wants to let me borrow a meter I would have zero problems getting some data for the interwebs…and considering I have several different setups and I would like to know how they run vs each other…as I have a superponics cloner which is a dwc with top feed…I’m building a new cloner which will be done in 2 days when all the parts get here which it will be low pressure aero and fogponics too…so I can of course do one or the other and both…my veg setup is current culture rdwc but it’s upgraded and im running a alita60 with 2 large air stones per bucket for a 4 site 8gal…and my bloom setup is 4 site rdwc 27gal totes 3in pvc waterfalls I have x2 350gph pumps and my return pump is a 700gph 3in pvc I also have a drain kit I built which leaves 200ml in ea tote only…same setup for veg for the drain kit which they help with circulation to…so if anyone has a d.o meter that would let me borrow I wouldn’t mind getting data for everyone

[anon32470837]

@beacher

A friend has used a similar but more basic system for years. A water pump circulating the res. The intake line for the water pump sits on the bottom and has a small tube branching off that goes above the surface to get air.

I wouldn’t say it makes a vortex, but a ton of air gets in there very simply and cheaply.

Excellent idea!

I have been trying to keep my rez cool, so I am using an ice chest and adding frozen water bottles. But, with the ice chest lid closed up tight, the rez wasnt getting enough fresh air, and the water got nasty. Ive been playing with different ways to allow more air in while keeping the light out and keeping things cool, but none of them worked perfectly.

I have a 300 GPH aquarium pump fluming the rez. After reading this thread, I just stuck a section of air line tubing in the intake of the water pump, and ran it out side the ice chest through a small hole. Now it sucks in fresh air through that small tubing and the impeller in the pump breaks it up into small bubbles every time the pump runs. Extra freash air with no light contamination and I can keep the ice chest sealed tightly for less heat. The bubbles are not as small as you would get with a needle wheel impeller, but good enough for what Im doing. About the same size you get from a regular air stone.

[GrapeApe]

Add a pvc drain pipe that drain from the top. Like a over flow on an ebb n flo table. Then insert venturi valve at the bottom. It creates a wicked venturi effect.

[Tappy]

This whole conversation is super cool…I’ve heard of the venturi effect before, but never looked into it.

What types of degrees do you guys have?..lol

[slain]

Haha well I’m a systems engineer so I basically mess about with experimental stuff for a living. I have a mate who is setting up a 8 pot dwc, so I am going to attempt to build one of these vortex venturi’s that hopefully works in a real world setting,
note… it’s not MY setup I am game to experiment on this with I’ll post some pics of it when I do.

[cannabissequoia]

@Tappy

I’ve heard of the venturi effect before, but never looked into it.

Just stare at a bong!

[SquirtleSquad]

I wanna experiment with this in a RDWC setup.

I’m worried about burning the pump out with so much restriction on the discharge.

I plan on using a 1000GPH that takes water from control bucket and dumps the water into the totes from a waterfall. This is where I was thinking of install a Venturi. So water would go from the control to a manifold which has branch run-outs to each plant site tote. On the branch run outs would be a Venturi to an elbow down through the tote lid and waterfalling on the water surface.

Water returns to the control via 1" barbed bulkheads and 1" poly.

The branches are 1/2" so not sure how much more I can reduce that for a Venturi effect.

This is the easiest way I see it working with my existing setup.

I first thought of using the barbed bulkheads as the discharge and doing away with the waterfalls and drilling holes mid way on the totes and returning to control bucket via that.

[anon32470837]

You dont really need a restriction in the water line to have the venturi work as far as sucking air. The restriction is there to force the water to flow faster, which will create more suction than withoout a restriction, but you can get suction just fine with no restriction to the water flow.

Just stick the air line in at a slight angle towards the direction the water is flowing. It also helps quite a bit if you can position the venturi up as hi as possible so there is no static pressure from the water colume that has to be over come.

If you have the venturi on the floor for example, then when you fill the buckets, there will be several inches of water above the level where the air needs to enter the system. That creates pressure and forces the water up into the sir line until its at the same height as the water in the bucket. Then when the venturi starts to work, it has to over come that pressure before any air can start to enter the system.

Instead, position the venturi as hi as possible relative to the ‘full’ or maximum water height in the buckets. That will let the venturi work at max efficiency.

Or here is another option that works just fine - cut the air line end at a steep angle and position it as in the drawing.

[anon32470837]

Also, if your pump is magnetic drive, I wouldnt worry about the blockage much. For other pumps, as long as you dont slow them down tooooo much they should be fine…

[GrapeApe]

Please keep in mind the roots are going to grow thick and long. Last 20 days of 12/12 can be a nitemare…Expect and plan for some sort of system shut down.

Think what the system will do when roots clog drains. Next what going to happen when the power goes out.

[slain]

Check this out for an aeration system… uses a venturi to suck air into the main line, and then uses a venturi in in the nozzles to drag water into the stream and mix it with the air… I am thinking I could 3d print one of these nozzles

From here.

http://www.acquaecoremedy.com/en/

The other thing to consider is an inline ‘static mixer’ like this:

with a venturi like this:

So Pump>Venturi>Mixer if you are using a standard pump or Venturi>Pump>Mixer if you are using a needle wheel pump. TBH, I think with a decent flow, just the venturi and static mixer would provide enough aeration for our needs.

[GrapeApe]

The bottom picture valve works great…

[Northern_Loki]

A non-optimal but super simple venturi to get started:

Although, the amount of air injected and the bubble size will be dependent on the velocity of the fluid moving past the venturi. The velocity has to be sufficient to pull a vacuum on the venturi.

Here’s an animated gif after passing the fluid + bubbles through a pump with a needle-wheel impeller using the above noted venturi:

FWIW, I like the concept of using a venturi.

[soultouch]

Not sure how a vortex drain at the bottom adds any more air to the system though it does help create a swirling mixing effect which that German guy from the 1800s would claim is a very good thing. The venturi certainly will thoroughly mix air into the water at what ever rate the orifice size will allow. Yes venturis are a very efficient way to add much smaller air bubbles than airstones, Now a vortex at the surface of a Rez tank would help draw in air, but splashing, waterfall, nozzles will also aerate the solution. You are correct that a DO meter would be necessary to measure how much air and how much air at depth

[666Dman]

Bruh, I’m in love with your layout and general idea. This is pure genius. Keep us posted.