DSB&CPW

[MikeS]

Hi all

We've been batting the subject of DSB's back and forth in another thread....
http://www.coralforum.com/ftopic1687.html
There has also been discussion concerning a method of plenum extraction...
http://www.coralforum.com/ftopic1521.html


Reguardless of your postion on DSB's...the arguement seems to boil down into a few basic issues. One of the main ones seems to be waste/nutrient accumulation within the DSB. Most anti-DSB folks claim that DSB's are nutrient sinks. Most pro-DSB folks think that this is overstated and the nutrients will eventually find theit way back into the tank to be dealt with in other means.

I'm pro-DSB....I've had a DSB in my tank for almost 3.5 years that functions as it is supposed to and with no major problems. Yet I recognize the the anti-DSB agruements and see some validity in them.

The main reason to have a DSB is denitrafication. The main arguement against the DSB is the potential for nutrient buildup and loss of denitrating abilities. So...logically....we should look for a system that gives us the denitrating benefits of the DSB while minimizing the potential negative side effects.

The CPW system outlined in the second thread is an attempt to do exactly that. I've read through it many times and I still come up with the same problems.

The first problem is biological. With a course substrate over the plenum, I think a number of problems will arise. The first is a loss of denitrating ability. This is not so much a function of surface area as it is a function of diffusion. The author stated he draws off the plenum daily...I feel that such a rapid drawing off of water combined with the use of a course substrate will introduce oxygen rich water into the substrate in a quantity that will effectively hinder the anerobic bacterias denitrating ability. Granted, there will still be some denitrafication taking place, but at a reduced level. And after all, if the primary reason for a DSB is denitrafication, why would you want to do anything to reduce that ability?
In addition, with such a course substrate required to make it function as the author has it designed, combined with a pull from underneith, detritus accumulation will undoubtly become an issue, much like a UGF., creating potential pollution problems

The second problem is mechanical in nature (but ties into the biological problem as well). Logically, to boost the denitrating ability of such a system, a smaller grain size must be used to control diffusion though the bed. But when such a small grain size is used, you begin to run into clogging problems and unequal diffusion. Diffusion through the bed must be fairly equal (as a function of area) for this system to be effective. If diffusion is not equal, "dead" spots in the sand and plenum will occur, rendering the system useless.

OK so we need a system that will have uniform diffusion and still maintain the amount of denitrafication that will justify having a DSB.
Here is my idea on how to make it work...

I'll start from the bottom up...

Plenum....I think I'd use a flat plenum that covers the whole bottom of the tank...with multible draw off ports....one in each corner, a few in the middle.

Crushed Coral.....A 2" bed of CC on top of the plenum.

Nylon fabric barrier (NOT mesh)....like the kind you see tents and sleeping bags made of.

3-4" Aragonite sand on top of nylon fabric.

Here's how I envision it working, from the bottom up. The ported plenum allows for waste to be drawn off. the multible draw ports will help minimize dead spots in the plenum. The CC provides a course substrate to aid in diffusion above the plenum without clogging it.
The nylon fabric prevents the fines from the sand to clog the CC. Mesh will be too open.....it will allow too many fines though and clogging will present a problem. Even if the nylon fabric is covered with fines, it will retain said fines, keeping them out of the CC, and still difuse H2O, and due to its fine filtering ability, I think it will do so in a fairly uniform fasion.
The aragonete sand will act as a filter and means of diffusion control. The larger particles of deritus will remain on the surace to be dealt with by scanvengers, ect.

I think that the author of the article is drawing off th e plenum too fast. I'd say that drawing a pint off every 4-7 days would be plent...

ok...open season.....have at it.... :lol:


Mike

[mojoreef]

Hi Mike, I am here as ordered, lol
DSB folks claim that DSB's are nutrient sinks
Not really nutrient sinks. DSB's can deal with P but does do a decent job on N. Its everything else it sinks.
Most pro-DSB folks think that this is overstated and the nutrients will eventually find theit way back into the tank to be dealt with in other means
I would have to agree with this statement for sure. I really dont think a DSB sinks nutrients. But to be honest algae blooms in my main system as an export system is not a very attractive option to me.
The main arguement against the DSB is the potential for nutrient buildup and loss of denitrating abilities
No mike thats really not it. the nutrients cycled with in a dsb will always leech out, thats the natural process, as above thats not an attractive option unless algae is what you are looking for. I dont think a dsb will ever loose its denitrifing capability. In reality the anaerobic zone (the dentrifing zone) will grow and grow until it reduces the aerobic zone, and begins to cause the loss of nitrification.
With a course substrate over the plenum, I think a number of problems will arise. The first is a loss of denitrating ability. This is not so much a function of surface area as it is a function of diffusion. The author stated he draws off the plenum daily...I feel that such a rapid drawing off of water combined with the use of a course substrate will introduce oxygen rich water into the substrate in a quantity that will effectively hinder the anerobic bacterias denitrating ability. Granted, there will still be some denitrafication taking place, but at a reduced level. And after all, if the primary reason for a DSB is denitrafication, why would you want to do anything to reduce that ability?
In addition, with such a course substrate required to make it function as the author has it designed, combined with a pull from underneith, detritus accumulation will undoubtly become an issue, much like a UGF., creating potential pollution problems
Ok the main concept behind a dsb is to put waste and detritus into biochemical cycles in order to facilitate the rotting of nitrogen based products and to sink the balance. Denitrification is but one process in the nitrogen cycle portion of the game. Problems that arise from this are as follows:
1: the eventual loss of the aerobic zone and thus the dependance on bugs to keep it circulated.
2: the build up of end product detritus = end products that the dsb cannot cycle or reduce.
3: the fact that you have to reduce the overall flow of the water in the tank so that you dont disturb the bed. this leads to eurthrophic (sp?) conditions.
We want to deal with the detritus and waste, if we dont we will be in trouble. So if we are going to trap it that is a good thing, now we will be able to deal with it. If the waste is pulled down through the substraight to an area where we can remove it from time to time we are practicing exportation, which is the main draw back for dsb's.
I think we need to look at the system first my friend. The concept has to be a total waste management system, not just denitrification. We need nitrification/denitirification/off gassing/ and the ability to remove products that the Sand substraight systems do not deal with at all. Stuff like Phosphates, metals, particulate dust, sulfides, methanes, and a multitude of inorganic components that are not nitrogen based.
Your system is a good start but lets focus on it as a total system. On the plenum I dont think you need multiple draw ports, good plumbing under the plenum would deal with that.
On the nylon, i am not sold on that yet, I think it would be to fine and would become a clog source very quickly. On the 3 to 4 inches of argonite you would basically render anything below that useless as the 4 inch dsb would do the same thing as if it were on the bottom. the suction you would need to deal with it would be far to much.
I also dont think the water to be drawn off from this kind of set up should only be done once every 3 to 4 months.

Mike I think the approch needs to be changed from trying to incorporate so many different systems into a new system that deals with the above mentioned probles, whatcha think.

Mike

[Condiman]

You both have brought up some excellent points. I think I will have to read more up on this before I make my final decision.

[MikeS]

No mike thats really not it. the nutrients cycled with in a dsb will always leech out, thats the natural process, as above thats not an attractive option unless algae is what you are looking for. I dont think a dsb will ever loose its denitrifing capability. In reality the anaerobic zone (the dentrifing zone) will grow and grow until it reduces the aerobic zone, and begins to cause the loss of nitrification.

Ok- but wouldn't oxygen rich H2O diffusion from the top down caused by pull on the plenum help keep the anerobic zone reletively in place?

Ok the main concept behind a dsb is to put waste and detritus into biochemical cycles in order to facilitate the rotting of nitrogen based products and to sink the balance. Denitrification is but one process in the nitrogen cycle portion of the game. Problems that arise from this are as follows:
1: the eventual loss of the aerobic zone and thus the dependance on bugs to keep it circulated.
2: the build up of end product detritus = end products that the dsb cannot cycle or reduce.
3: the fact that you have to reduce the overall flow of the water in the tank so that you dont disturb the bed. this leads to eurthrophic (sp?) conditions.
We want to deal with the detritus and waste, if we dont we will be in trouble. So if we are going to trap it that is a good thing, now we will be able to deal with it. If the waste is pulled down through the substraight to an area where we can remove it from time to time we are practicing exportation, which is the main draw back for dsb's.

Ok...but I'm still concerned about the detritus not making it all the way to the plenum. Wouldn't be easier to deal with it on the surface of the substrate rather than hope it makes it all the way to the plenum without getting trapped in the substrate?

I think we need to look at the system first my friend. The concept has to be a total waste management system, not just denitrification. We need nitrification/denitirification/off gassing/ and the ability to remove products that the Sand substraight systems do not deal with at all. Stuff like Phosphates, metals, particulate dust, sulfides, methanes, and a multitude of inorganic components that are not nitrogen based.

Agreed. I thought this was the purpose of drawing off the plenum, to help remove said stuff.

Your system is a good start but lets focus on it as a total system. On the plenum I dont think you need multiple draw ports, good plumbing under the plenum would deal with that.

Agreed.

On the nylon, i am not sold on that yet, I think it would be to fine and would become a clog source very quickly.

Hmmm...I really don't think it will "clog". The nylon fabric is a pretty fine knit product, I don't think sand will get trapped in it. Granted the finest particles will come to rest on top of it because of migration, but I still think water will still be able to pass through it adequately.

On the 3 to 4 inches of argonite you would basically render anything below that useless as the 4 inch dsb would do the same thing as if it were on the bottom. the suction you would need to deal with it would be far to much.

Couldn't that be "bypassed" by time given between draw-offs? I mean water will diffuse on its own through the nylon and into the CC, even without pull from the plenum.

I also dont think the water to be drawn off from this kind of set up should only be done once every 3 to 4 months.

neither do I...I said every 4-7 days or so.

Mike I think the approch needs to be changed from trying to incorporate so many different systems into a new system that deals with the above mentioned probles, whatcha think.

Definately open to any suggestions! :-D

[mojoreef]

Ok- but wouldn't oxygen rich H2O diffusion from the top down caused by pull on the plenum help keep the anerobic zone reletively in place?
yes that is the plan. I was just trying to identify the problem.
Ok...but I'm still concerned about the detritus not making it all the way to the plenum. Wouldn't be easier to deal with it on the surface of the substrate rather than hope it makes it all the way to the plenum without getting trapped in the substrate?
Agreed that is why I dont think the fine sand is going to work. Remember the detritus wont be in full form but just what ever is left over or doesnt get processed. anaerobic zones will form no matter what the substraight size, so its not much of a concern with me. The biggest thing is to get the end product out, that way it can fill.
Hmmm...I really don't think it will "clog". The nylon fabric is a pretty fine knit product, I don't think sand will get trapped in it. Granted the finest particles will come to rest on top of it because of migration, but I still think water will still be able to pass through it adequately.
What I worry about here is the pore size of the holes in the nylon. with all the percipatation and solid forming I think it would clog to easy. Again it is something we could skip if the particle sizes would be larger.
Couldn't that be "bypassed" by time given between draw-offs? I mean water will diffuse on its own through the nylon and into the CC, even without pull from the plenum.
Well diffusion is one of the draw backs of a dsb, i think the nylon just adds to the problem. Maybe you could do some testing on it???


Mike

[MikeS]

Sounds good...any suggestions for a test?

OK if the system was to incoperate a larger substrate and no fabric or sand...what size substrate would you recommend? Depth? And how often and in what amount would you draw off the plenum?

Mike

[mojoreef]

You know thinking about it why dont you just reverse the concept of your original plan. Run the wasteing thing as the base, kinda like a draw off system, then your nylon, then a 1 and 1/2 of fine sand,then nylon, then say 2 inches of coarse grade. on top of the that. the coarse grade substriaght should stay areobic for at least and inch or two, the fine sand in the snadwich would go anaerobic no problem. It wouldnt matter to much about even diffusion in the fine layer and the coarse layer would allow for better diffision from above and the suction from below. I think i still like the concept of fine mesh screening for migration of dust and organics, but until we know what the nylon will allow past it I am not sure about it.
As per how often to suck out the end product I would say every few months at best. the concept for me anyway is just to stop the eventual build it.


Mike

[Condiman]

Now my one concern with this is that with new reef hobbiest want to keep things simple and with a DSB maintainance is alot easier. That is why I think it is more popular. Not everyone like Razoreqx has the ability to have a controller to draw out the waste multiple times during the week. Hobbiests who just start out want to keep things simple. But as time goes on and they read and learn more then maybe they will try CPW. But I dont think it will catch on like DSB. Dose anyone have a diagram of what the CPW is supposed to look like. I think it will help other reefers and myself understand this better if we had a visual aid to look at.

[MikeS]

Now my one concern with this is that with new reef hobbiest want to keep things simple and with a DSB maintainance is alot easier. That is why I think it is more popular. Not everyone like Razoreqx has the ability to have a controller to draw out the waste multiple times during the week. Hobbiests who just start out want to keep things simple..

Agreed. The simpler this setup could be made the better. Personally, I'm looking at a version of it as a possibility when I upgrade my 55 to a 75 gallon. I don't want to spend a bunch of $$ on computer controlled gizmos and such. I'd like to have nothing more complicated than a powerhead on it.

But as time goes on and they read and learn more then maybe they will try CPW. But I dont think it will catch on like DSB. Dose anyone have a diagram of what the CPW is supposed to look like. I think it will help other reefers and myself understand this better if we had a visual aid to look at.

Not aware of any diagrams....


Mojo....I like your idea....I'm still a bit concerned about the larger substrate on top trapping detritus...obviously with the fabric none of the solids will find their way to the plenum. However, there is probably no way to make this "perfect" - a compromise will have to be found somewhere....

on your idea...I'd bump up the sand to 2 inches...just to keep us DSB types happy :-D ....and I'm still in favor of nylon fabric over mesh. I think even covered in dust and scum, water will still diffuse through it. The real trick will be to keep that diffusion uniform to avoid dead spots.

On the plenum itself....what would you recommend on design and extraction of waste?


Mike

[mojoreef]

Condi were just playing around my friend. Its what us old reefers do to pass the time, lol.

Mike no more sand, (flippen sand junkie) lol. Mike we want the solids to go into the plenum area. that way we can dispose of them.


Mike

[Condiman]

Hey dont worry I am always lookin to learn other techniques

[MikeS]

Condi were just playing around my friend. Its what us old reefers do to pass the time, lol.

Old...yes....it's so depressing :-D

Mike no more sand, (flippen sand junkie) lol.[/quote]

We'll negoitate sand depth after we clear up a few other problems. Gotta have my sand... :-D

Mike we want the solids to go into the plenum area. that way we can dispose of them.[/quote]

How are they going to get there? I don't see ANY solids making it through 2 inches of CC, 2 inches of sand :-D and two layers of nylon fabric.

However, consider this...since the solids themselves are not really the problem, their byproducts are, maybe we don't have to worry about them (the solids) so much. Drawing off the plenum will remove H20 hopefully saturated with said byproducts. All we are doing here is looking at it from a different time frame. Your idea is to remove the solids before they become a source of bad byproducts. My idea is to remove the bad byproducts as they accumulate in the system. If the system is adequate, the end result will be the same. Granted, mine pushes the waste accumulation envelope more than yours, but I think this approach will eliminate certain mechanical barriers, and will provide the tank with a bit stronger biological "cushion" so to speak.

I guess what I'm aiming for is a system that gives us the best of both worlds...one that will provide levels of nitrate reduction near that of a DSB while hopefully bypassing some of the negative side effects. Removing the solids is a great way to reduce nutrient and byproduct buildup in the tank, but if I wanted to go that route I'd simply do a BB tank like yours. In a nutshell, I want a system that will take care of the solids for me ( no vaccuming for my lazy bum :-D ), provide denitration, and allow me to remove some if not all of the nasty byproducts. Or at the very least help extend the life of the DSB.

Mike

[mojoreef]

However, consider this...since the solids themselves are not really the problem, their byproducts are, maybe we don't have to worry about them (the solids) so much.
Ahhh grasshopper, but solids are the key to the whole thing. Think about it, what is always going to be associated with the solids and the organics?????? answer that one and you have gotten it.

Dont put to many constraints on it mike remember the ultimate goal is to grow coral.


Mike

[MikeS]

However, consider this...since the solids themselves are not really the problem, their byproducts are, maybe we don't have to worry about them (the solids) so much.
Ahhh grasshopper, but solids are the key to the whole thing. Think about it, what is always going to be associated with the solids and the organics?????? answer that one and you have gotten it.

Dont put to many constraints on it mike remember the ultimate goal is to grow coral.


Mike

I think I know exactly what you are refering to. The solids are the culprit...their breakdown leads to undesireable byproducts. Eliminate said solids from the system and you take care of the byproduct issue. Right?

That's not what I'm looking for in this system however. If that were the case, I'd simply go BB. What I'm looking for is a system that allows the tank to deal with these solids and their byproducts without me having to suck them (the solid waste) out of the tank on a regular basis. I want the solids to be part of the equation.

IMO with the mechanical limitations of this system, the byproducts are going to be easier to extract than the solids themselves. My thinking is let the substrate deal with the solids (break them down) and then extract them out through the plenum. Although this system might not be 100% efficient, at the very least it will help. Let me guess your next reply....said byproducts will be tied up in the biogoo and not easily extracted into the plenum, right? :-D

Mike

[mojoreef]

I think I know exactly what you are refering to. The solids are the culprit...their breakdown leads to undesireable byproducts. Eliminate said solids from the system and you take care of the byproduct issue. Right?
Ok lets look at it for a second. In a dsb we are trying to reverse a couple of inevitables. One is that a dsb can only do a low ammount of bioload because the nitrification/denitrification process is slow. also it only handles an ammount of what is put in thier (nitrogen based) the balance stays and builds up. and then the problem with P leeching. In order to help the above problems along we need to adress them, possible with some filtration design. So one by one then,
The low bioload: The ammount a bed can handle in regards to waste/detritus and so on is low for what most folks want in a tank. If we can figure out how to remove some or eliminate some we can have a win here.
The build up: Now the pure idea of having a wasteing or draining system under the plenum (or what ever we call this) will fight this battle, so I think we are on the right road already.
P leeching: a little more tricky, but I think it will fall in line with the fix of the above problems.
Ok back to solids. helping to remove the solids will help the bed in the ammount of bioload it can handle. Also you have to look at what is associated with the solids and how thier removal will benefit us. As mentioned prior bacteria feed by excreting microbes in a enzyme type fuild (snot) they will surround the solid and begin to reduce what parts of the solid they need. with in and around the solid will be this snot, which is loaded with the byproducts, products they cant reduce, bacterial flock, the protienious bile (snot) and so on, removing it or allow it to drop into an area where we can remove it it a big win against both the build up and bioload problems. I am not saying go after all of it, but I think we should allow what ever can drop into the lower region to do that, it is a huge form of exportation and I think a major key. We are not going to be relient on it totally and will still have the vast majority of the bed performing the Nitri/denitri processes. But I think this will allow for the kind of processing ability that a dsb needs to be.
The waste and so on that would get trapped in the top portion of the bed is where the works needs to be done. this is the area that gets clogged the easist, the ammount of waste coupled with the biproducts and goo (lol) is what makes the region go anaerobic. My thinking is that if we make that area with larger particles we will help to keep it aerobic. Also the larger particles will allow for more diffision into the anaerobic zone, this will lessen the probem with being so relient on bugs for this operation, Win win.
On the removal of organics. build ups, detritus and so on that goes into the plenum area i dont like the concept of constant wasteing. When you pull water and all that is associated with it out of the plenum zone you are screw around with the integrity of the each zone. the areobic zone will feel no impact, the anaerobic zone is going to take a hit, it will be saturated with oxygenated water and will convert the bacteria to oxygen fixation instead of nitrate for the period of time that th oxygen is present, if you are constantly wasteing you are keeping this zone in an internal state of flux, I dont think that going to benefit us. For me once every 3 months or so we give it a good draw, This will hurt the anaerobic zone, but it will also flus the aerobic zone so thier wont be an immediate need for the denitrification as the waste has to go through the nitrification process from scratch. the time should balance itself out.

Anyway thier is a rough concept of what I had in my mind.


Mike

[MikeS]

Very well put as always mojo! :D

I think we are much closer to being on the same page now. That last post was much closer to what I have in mind.

Ok...maybe we can look at some of the specifics of the system....what do you think should be used as a plenum? A flat one like you see in a UGF?

Mike

[mojoreef]

Ok lets start on the bottom. We can go with a flat model like a UGF or a sloped scenerio as we talked about before. I think the guiding factor has to be its ability to gather up the detritus and falout that comes to it. You know I like the sloped model, so tell me why you perfer the flat??

Mike

[MikeS]

Not sure if I really have a preference...lets talk about the sloped model again....

Mike

[mojoreef]

I will draw something up to look at.


Mike

[MikeS]

Just an update....

we have a few plenum ideas....I'll post drawings soon....

Mike

[MikeS]

Update! :D

Mike (Mojoreef) has constructed a working prototype of this plenum system!

The plenum design consists of an acrylic "vee" shaped plenum. It is plumbed with a 1/2" PVC pipe water removal system. The plenum will be covered with eggcrate, fine mesh, and topped off with 3" of 1-3mm aragonite sand.

The basic theory is that most of the detritus will migrate through the substrate, slide down the vee shaped plenum top to collection points and into the plenum itself, where it can then be periodically extracted.

Mojo is getting ready to test his prototype in a tank, his first tests will be mechanical in nature.

These are pictures Mojo has taken of his plenum prior to putting it into a tank.

This thread will be updated with more pictures and the results of mojo's tests....