Flow Through DSB

[bioload]

It's almost a month now and there is no noticeable reduction in Nitrates from the DSB effluent. I'll give it some more time, but growing impatient not seeing any signs of progress. ORP is still in the +300mV range.

If anyone has any documented success of a DSB providing nitrate reduction....I'm all ears, keeping in mind that I've yet to perform any water changes and there is no filtration that is exporting anything from the tank (fuge, skimmer, etc.)

Also I noticed your grain size looked rather large. - If I pull the plug on this one I might replace with some silica. I have a bucket that is fairly fine...don't recall the exact size, but the sieve I used to obtain the sand took some time to fill the bucket.

On a side note I've had some chaeto, and a couple varieties of caulerpa in a standard fish bowl on my desk with no filtration for about a month now. Still waiting on my sump, and I didn't want to keep it in the DT.......nitrates are 0.

 

[Aquarist007]

Capn' H - I strongly disagree with the model that says that water flow thro' the sediment is controlled or dominated by biological activity. It's been measured, modelled and experimnted with and demomstrated to be a mix of something like advective flow 90%, biological effected flow 8% and simple diffusion 2%. I've seen the various quotes from Shimek and others , adn they are completely unsubstantiated as far as I can tell - he offers no support for them.

Thanks Wayne

 

[artur]

Hello to all! Great thread,

Im setting up my dsb in a bucket type of thing, I build my bucket as of 10" by 12" and 23"high glass box, and im putting in very fine sad
i will be having hi flow over the top
Do you think this is to deep or the deeper the better?
Also should I set it up with a plenum below??
Thanks for your comments

 

[bioload]

Hi artur,

My guess would be a very deep sand bed would have a larger low/no oxygen zone. I'm currently at 6".

I just finished an acrylic box that is 8lx8wx17h> I was planning on using it as a very deep sand bed, but may just end up filling it with algae (chaeto in a bucket).

Forgot to mention earlier that my tank has no direct lighting preventing the growth of any algae inside the tank. There were some small patches of hair algae on the rocks when I first started but they are slowly fading away.

I'm beginning to think the DSB phenomena is somewhat of a placebo effect when it comes to reducing nitrate. Maybe I'm jumping the gun and it's still too early (Day 24), but many may be overlooking the effects of their algal growth, skimmer export, water changes etc.

 

[chimmike]

I'm going to venture a guess by saying that your experiment doesn't allow the growth of the bacteria through the soaked but not flowed-through media.

 

[bioload]

Hi Mike,

Would that mean that the bacteria has yet to colonize the substrate, and I just need to give it more time or the conditions are not suitable for the bacteria to establish

 

[Maivortex]

If the tank has been set up for a month, it still can be cycling. This is why u have not seen a reduction in trates. Have u measured nitrite?

 

[bioload]

The tank was set up in April and cycled within a couple weeks. Bioload 75 - Reef Aquarium

The remote sand bed was added June 10th when Ammonia and Nitrite were 0, and Nitrates were rising.

 

[Amphiprion]

You know, the DSB in a bucket is a really great, simple design, and the principle source of water flow is well understood and modelled. Please look to the research I referred to on the first page as they have already modelled all this stuff very nicely. To say noone knows how a dsb works is just not so. You just won't find it in a lot of hobbyist material

Capn' H - I strongly disagree with the model that says that water flow thro' the sediment is controlled or dominated by biological activity. It's been measured, modelled and experimnted with and demomstrated to be a mix of something like advective flow 90%, biological effected flow 8% and simple diffusion 2%. I've seen the various quotes from Shimek and others , adn they are completely unsubstantiated as far as I can tell - he offers no support for them.

I'd also argue the top layer of a sand bed is pretty good aerobic biological filter as well. You do not need a ton of live rock to provide a bacterial media (tho' it's nice)

What about advection that is a direct result of biological activity? What percentage of the overall porewater advection can be attributed to that vs. that of what is created by water column turbulence?

 

[ruprecht]

What about advection that is a direct result of biological activity?

By definition, advection is an abiotic physical process.

 

[Amphiprion]

By definition, advection is an abiotic physical activity.

No, not really. There have been several papers talking about bio-advection or advection as caused by biological activity. Advection, at least as I've always known it, is simply the horizontal/lateral bulk movement of water through a medium, be it more water or sediment. The original causal force isn't necessarily set in stone or necessarily abiotic. I could certainly be wrong, but I also do realize that across fields of study some definitions can be different.

 

[blasterman789]

I've been wanting to try this for years. Basically, after reading up on how a nitrate coil works I wanted build an external DSB or 5gal bucket with sand, and then run a very slow drip through the substrate (few gallons per day). If the nitrate coil worked, then this method should work much better because of the much greater surface area involved.

I'm as frustrated as the OP this hasn't worked. My suggestion would be to keep trying and perhaps seed the middle of the DSB with lots of deitrus.

 

[chimmike]

Hi Mike,

Would that mean that the bacteria has yet to colonize the substrate, and I just need to give it more time or the conditions are not suitable for the bacteria to establish

I think the water needs to flow OVER the sand bed, but not through it. There will be water in the bed itself, but flow through it is probably just barely too much for bacteria to establish.

It's worth a try at least. Put some baffles in to direct the water around instead of being a straight shot in, over the sand, and out.

 

[chimmike]

I'm as frustrated as the OP this hasn't worked. My suggestion would be to keep trying and perhaps seed the middle of the DSB with lots of deitrus.

I think something like seeding it with detritus is begging for trouble actually. Let it work naturally. But again, I wouldn't do flow thru, I'd do flow over. And there has to be enough flow that nutrient export onto the sand bed occurs. If it's too slow, you're probably not getting many nutrients to the sand bed in the first place.

 

[Allmost]

I think something like seeding it with detritus is begging for trouble actually. Let it work naturally. But again, I wouldn't do flow thru, I'd do flow over. And there has to be enough flow that nutrient export onto the sand bed occurs. If it's too slow, you're probably not getting many nutrients to the sand bed in the first place.

I completely agree with water having to go over the bed, not through it, and that was the point I was trying to make at the first couple pages ... lol

one thing to help you seed THIS method is sulfure though !!! at about 3 " down, add a layer of sulfure ! that will consume the oxygen and u can guess the rest

 

[TheFishMan65]

The way I understand it you don't want detritus. That seems to be a recipe for disaster. I don't completely understand these things (does anyone?) but with a remote deep sand bed the idea is to keep the detritus out.

 

[ruprecht]

No, not really. There have been several papers talking about bio-advection or advection as caused by biological activity. Advection, at least as I've always known it, is simply the horizontal/lateral bulk movement of water through a medium, be it more water or sediment. The original causal force isn't necessarily set in stone or necessarily abiotic. I could certainly be wrong, but I also do realize that across fields of study some definitions can be different.

I believe that "bio-advection" is typically referred to as bioturbation while some people like to use bioirrigation to describe the flux of water into and out of biologically derived sediment structures such as burrows. I agree that sand infauna can enhance advection but it has been shown that at particular flow rates, sand sizes, and sand depths, advection alone can be enough to drive water and micro particles to depths that coincide with bacterial (de)nitrification.

 

[Allmost]

The way I understand it you don't want detritus. That seems to be a recipe for disaster. I don't completely understand these things (does anyone?) but with a remote deep sand bed the idea is to keep the detritus out.

remote DSB, yes, u want it to be fed with pre filtered water.

but DSB in the system, like mine, I want detritus to settle on top, so that the creatures have something to eat and reproduce, and it works better than mechanical filter in sense of keeping water clear.

there are different types of DSB

 

[TheFishMan65]

I agree, but I believe the current model is closer to the RDSP or DSP in a bucket. I would like to see bioload try for another month. If that fails slow the flow let some detritus settle and model the other type for a month or two. Maybe we will find out which one works better. Ideally we would want new sand, but I am not sure it is required.

 

[chimmike]

I think that changing flow to over TOP of the sand will make the difference here, and increasing that flow (providing additional oxygen to the top layer via higher flow)