vortex size

[bil]

A while back I read a very nice account of the physics as to why the heavier particles settle in the centre. I'm pretty sure it involves an upward force. Stir a cup of tea with tealeaves in it, and a cone of tealeaves forms in the middle.


Centripetal force acts at right angles to the radius of rotation, so the finer particles are thrown out in a spiral and then impact in the boundary layer which is the static layer of water that it 'stuck' to the internal surface of the vortex. If this surface is rough, turbulence will occur that will destroy this smooth undisturbed layer, and the particles will not be able to sink thru it to the bottom, but will, I think be ejected back into the main flow. Peter M basically created multiple surfaces upon which static boundary films formed. You could create the same effect with a non rotating settlement with many sheets of corrugated plastic sheets a small distance apart, so the water was forced to take an undulating path thru it, forcing particles out along its length.

Failing all this, you could simple bin the vortex and place a microscreen over static K. That has a tiny footprint, but enormous solids removal. Plus the screen being fine nylon curtain material is dirt cheap to make.

CAUTION such screens will seize up solid in an hour or two if exposed to daylight. If kept in the dark, they will work brilliantly for months without that happening.

[bekko]

bil,

That trick with the corrigated plastic sheets would be like an inclinded plate (aka inclined tube) sedimentation chamber. There is a commercially available product for use in inclined plate sedimentation which is made of fused sheets of corrigated plastic.
http://www.aquaticeco.com/index.cfm/.../5031/cid/1394
This stuff is also promoted for biofilter use, but the square feet of surface area per cubic foot of space is is pretty low.

I think the principal of the inclined plate is that as water moves through these inclined plates or tubes, a particle has to fall only a short distance straight down before it comes into contact with a solid surface. The vertical height within an tube inclined at a 45 degree angle is only the square root of two times the diameter squared. Hope this makes sense - a picture would be nice. Once the particle comes into contact with the solid surface inside the tube it sticks and, as crud accumulates, it may slide back down the inclined tube or plate. It is a way to increase the sedimentation rate within a vessel of given volume and flow. These things increase sedimentation well, but are not very good at self-cleaning and are often difficult to manuall clean. If the crud is not washed away on a regular basis, the spaces will clog.

I still like the idea of spinning debris to a center drain where it can be removed on a frequent basis with minimal effort - or even automatically via an actuator valve and timer. Not only does this reduce labor requirements, it gets crud out of the system before it can decompose further and release more nutrients to the water.

steve hopkins

[bil]

The difference ic that with an inclined plane the sediment settles onto the plates, and is hard to clean. Vertical plates ensure the muck drops down and can be collected as in a vortex base.


Easier to go with screens tho as you can get serious solids removal in a very small space.

[shiromujigirl]

But Bil, you must admit that CLEANING screens is not an easier go.

I put a submerged trash pump on a GFI and timer in my settling tank. It is the height of laziness.

[bil]

if set up properly, the muck all goes down to one end, pushed by the water flow. Screens with static K will give almost total removal in the same sort of footprint as a Nexus, at a FRACTION of the price. They fail safe, unlike the answer and cost nothing to run. If the price of that is tipping the crap off the screen every day or two, I figure I can live with that.

[shiromujigirl]

What mu screen are you using?

Do you remeber the horrible fight we got into on NI a few years ago about settling tanks? You are such a good insulter.

Bil, please go over to KV and see about your tomcat and daffodils in Cat Issues thread. I need to discuss "gentles".

[bil]

200 micron, but 50 also seems to work well. I plan to have the ability to have a cascade system if necessary, but we shall see.


Gentles? Now there's an old English word.

[bekko]

bil,

Is the screen lying across the top of the sedimentation tank? Is the screen on a frame and what does the frame look like? How is it fool-proof and what happens when the screen clogs?

Sorry for the barage of questions.

steve hopkins

[bil]

There is no direct water connection between pond and filter. The water is sucked out of the filter and dropped into the pond thru a TT, so the water can't siphon back.

The water from the pond then overflows onto the screen and falls thru it, pushing the waste ahead of it. The screen isn't submerged.

email me at bil_wight@ntlworld.com and I'll send you a diagram. Put something about filters in the subject line or the email will get deleted with the spam.

The idea is that if the screen does fill up and clog, the water will overflow into the filter and then the crap would be caught in the static K. No risk of overflow.

[bekko]

I get it bil. Sounds good.

Since SMG's gets to remember stuff, so do I. About 1995 someone on one of the long-forgotten koi boards told me about using nylon stockings for mechanical filters and about using a cannister of compressed air to help backwash and re-segregate sand and gravel in a mixed media filter. I think that was you. Used both of those tricks here and there along the way and both worked as advertised. A belated thank you.

steve hopkins