Settling Tank

[Esquare]

I am getting tired of all of the detritus that accumulates in my sump and skimmer area. Therefore, I am looking at options to deal with the waste in an easy manner that doesn’t involve a sock. In the process of researching this question/issue, I came upon the option of a settling tank and would like to know if anybody has any experience with them and can pass along your experience. I was thinking of something that was in line with the drain from the DT and also incorporated a drain direct to my sink drain for removing the detritus easily.

Any thoughts are much appreciated.

 

[saveafish]

The only think I can thank of would be 2 ways either very long and wide OR one full of many baffles. to have it settle is has to have a steady sllllooowww flow rate. The commercial ones I ever seen had many baffles in them that was only 1-2" tall from the bottom.

 

[Esquare]

Yeah, that's what I was afraid of.

I have a 20 L that is supposed to be a frag tank eventually in line before my fuge that gave me the idea for a settling tank. It catches a lot of detritus but the flow is the same as what goes through my fuge so it’s slow. I also get a lot of junk in the skimmer section of my sump, but that’s pretty tall with a bubble tower for the feed so the water goes down then up a ways.

If I wanted to run all of the flow through a settling tank prior to splitting off to the fuge and skimmer I’m afraid it will be too fast to really settle. I just like the idea of a settling tank with a sloped bottom and a drain to the sewer line so all you needed to do to clean it is throw a ball valve. Oh well, can’t have everything I guess.

Thanks for your input.

 

[One Dumm Hikk]

If everything is settling in your sump now, then adding a second sump before the current sump would give it a place to settle instead of in the sump/skimmer area. Then you simply siphon the first sump. You could build the bottom of it for easy draining if you wanted.

 

[Esquare]

I picked up some acrylic scraps from the local plastic place the other day so maybe I'll give it a try. At worst I'll be out $10 in acrylic.

 

[Jasontkd]

get a cone bottom or conical tank. hook it inline. there is a bulkhead at the bottom of the cone. everything will settle down into the cone, and then you just have to open a ball valve to your drain, and all the stuff comes out.

 

[Esquare]

That's what I was thinking Jason except with a slanted bottom to the bulkhead.

 

[Esquare]

Ok, here is a basic idea of what I'm thinking.

 

[saveafish]

Where and how does every one have these dang draw programs. my sump has a heck of a settling problem. but it is made costom and it holds the settlements in one place for the most part but I can not draw it for you

 

[Esquare]

I used to use a 2D CAD program called Delta CAD (and still do use it from time to time) now I use Google sketch up for 3D (it’s free go to Google downloads). I just threw the above sketch together and am refining it so as to get other opinions. The idea is that the open hole on the left would be where the bulkhead and ball valve would go to drain/clean out the debris directly to the sewer. The vertical pipe next to it would be a drainpipe (stockman or something similar) that would split off to the fuge and skimmer. That leaves the pipe on the right for inflow from the DT. The question of physics is will the water slow down enough to allow the junk (or a larger portion of it) to settle out.

 

[Jasontkd]

I was talking about something like this

http://www.usplastic.com/catalog/pr...splastic&category_name=20726&product_id=33150

 

[Esquare]

That would certainly funnel the debris to the drain. Let me ponder and see can I redesign with that in mind. Thanks Jason.

 

[Pbrown3701]

In order for a settling tank to work, you need a high flowrate INTO the tank so that detritus is delivered to it. You then need a large volume/large cross sectional area so that the velocity of the water through the settling tank is very low - which allows the smaller particulate to settle.

I think with your design/drawing, the flowrate into this tank would stir up the bottom. If you turned the flowrate down so that it didn't, you wouldn't get enough flow to bring much particulate into it.

The ideal case would be to have the settling tank as the first "chamber" after the water drains from the tank. The tank would be very large (wide and long). As the water slowly moves from one side to the other, the particulate settles to the bottom.

I don't think there is any way to get around the large size required, just due to the physics of it.

 

[Pbrown3701]

The conical tanks would only work if they were a very large diameter. You could plumb into the tank from the side (towards the bottom) and then out the top. The key again is to have a very low velocity from the input to the exit. The faster the velocity, the fewer small particulate you will trap.

 

[scottyd1119]

If you somehow put a verticle divider in the middle of that conical tank and have your inlet and outlet on opposite sides of the divider that would force the water to go down below the divider and then come back up which would help alot with getting things to settle

 

[Esquare]

Pbrown, that's my dilemma, trying to get the maximum amount of settling in the minimum amount of space. After Jason’s input of the conical design, I thought of incorporating the conical bottom into the square design above for more efficient removal of debris.

Scotty, that was the idea of the vertical divider in my drawing, to slow down the water flow.

I think that I need to take another look at my space available and see if I can squeeze a larger tank in there.

 

[Pbrown3701]

<a href=showthread.php?s=&postid=13121006#post13121006 target=_blank>Originally posted</a> by Esquare
Pbrown, that's my dilemma, trying to get the maximum amount of settling in the minimum amount of space. After Jason’s input of the conical design, I thought of incorporating the conical bottom into the square design above for more efficient removal of debris.

Scotty, that was the idea of the vertical divider in my drawing, to slow down the water flow.

I think that I need to take another look at my space available and see if I can squeeze a larger tank in there.

In actuality, the center divider will SPEED UP the water. The velocity of water depends directly on the cross sectional flow area. If you have just a round tank with no center divider, then your cross sectional area is PI*R^2. So, if your volumetric flowrate is X [in3/s] and your area is Y [in2] - to get mean velocity, you simply divide X/Y which gives you velocity [in/s].

Now if you put a center divider in, the flow area is cut in half and you double the mean velocity. Sure, the water will flow down first and force all the particulate down, but then it will also flow up (and at a much higher velocity than if you didn't have the divider). Furthermore, if you force all the water to the bottom and then back up, you will simply entrain all the settled particulate and drive it up and out of the tank.

 

[Esquare]

Very helpful info Pbrown. I wouldn’t have thought the divider would actually speed up the flow but as you explained it, it makes sense. So, as I understand it, for a settling tank to work efficiently it needs to provide a large open area to allow the flow to dissipate. Is there any way to cipher the correct dimensions for say approx 600 gph?

 

[Pbrown3701]

Esquare - exactly correct.

It is a sliding scale. The size of the tank will directly affect the size of the particle removed. So in order to calculate size, you need to determine what is the smallest particle you want to remove by this method.

Think about it this way, if a large pebble entered the tank, it would most likely sink regardless of the flowrate (practically speaking). However, a 1 micron particle of the same rock (same density...) would require a much slower flowrate in order to settle.

Or another way - given a constant flowrate into and out of the tank, there will be a particular size particle that will settle - smaller than which will not. Again, this is assuming that the particles are all the same density, which is not the case, but is close enough for this explanation.

 

[Esquare]

The way my sump system is set up, the water diverted to the fuge first goes through a bare 20 gal long (future frag tank) then the fuge (another 20 gal L) then the sump. The bulk of the water from the DT goes to the skimmer then the sump. It sounds like my best bet (as a short term experiment) might be to send all of the water to the bare 20 l first then split it to the fuge and skimmer and see what settles out in the bare 20 L. This should at least give me an idea of what a tank the size of a 20 L will settle.