fluidized (sand)bed filters?

[ReefTECK]

Or I guess presumably they use sand in the "fluidized bed filters." These are different then DSB filters right? I'm under the impression that fluidized bed filters are used for detritus removal on large systems? Whereas DSB filters are for denitrification.

Q1: Am I correct in these assumptions?
Q2: Anybody using a fluidized bed filter? Pix?
Q3: Other benefits of fluidized bed filters other than detrius removal?
Q4: Is this comparative to a micron filter like a Ocean Clear, or Magnum 350?

Just thinkin..

ltz,
Andy

 

[ReefTECK]

::bump::

 

[superedge88]

fluidized bed filters can be referring to biological filtration that simply tumbles find sand in a water column for a huge amount of surface area for bacteria to grow on. The downside to a fluidized bed filter is that in a power outage the bacteria growing on the surface of all the sand grains is then suffocated by the collapse of the tumbling sand bed, which kills the bacteria in a matter of hours, so a system crash can happen quite easily if this is your main source of biological filtration.
A different type of filter is a sand filter is a mainly mechanical filter where particulate matter gets caught by a bed of sand, then when you backwash the filter you remove all caught particulate matter. The sand filter is also a means of some biological filtration.

 

[ReefTECK]

Would you then use different sizes of sand to target the filters primary purpose then? (ie. course for biological, oolitic for detrius removal)? Or your saying there are also flow differences in the way which water is pumped into and out of the two types of filters.

This would be most beneficial, and practical on a large, or commercial system housing a heavy bioload then yes?

 

[superedge88]

They are two different types of filters mechanically.
The sand filter is used in large aquarium applications.

 

[ReefTECK]

so is this what the difference is mechanically, where on filter 2 you wash water through the bottom up and out to dispose of detrius caught in the filter?

I'm not sure if this assumption is correct or not.

 

[superedge88]

that is basically a fluidized bed. The sand filter diagram is a little more flexible, some sand filters work differently than others as far as direction of flow, but you get the basic idea. The sand filter MUST be made so that you can backwash it, otherwise you are just creating a place for nutrients to go and rot.

 

[ReefTECK]

I am particularly interested because I have heard a lot about these types of filters, and I have been planning a large aquaculture laboratory.

Thanks for your input,
Andy

 

[Aaroneous]

I was just reading about these this morning. A couple notes they made about the fluidized bed filter is that you want to have some sort of sponge or filter floss to prevent any detritus or large particles from entering the system and Silica sand is to be used because argonite sand will breakdown or dissolve.

 

[ReefTECK]

Does silica sand not dissolve into silicate at low pH? Just a silly assumption I've been holding on to.....I figured it didn't hurt to stay away from it.

Likewise, aragonite shouldn't dissolve at a pH above 6.9, right? Unless biofilms within would cause localized acidification.....I feel a laboratory test coming on....damn...see this is why I need to build one soon!

ltz,
andy

 

[Aaroneous]

I think one of aragonites inherent properties is slow and constant breakdown; combine that with tumbling and a high water flow and that process is sped up. I think that is why it was suggested not to use it. When i get home Ill post the excerpt from the book.

 

[ReefTECK]

A book that I don't have? Impossible!!! I want to know what it is from! Actually, I might refer back to Dynamic Aquaria, there might be some info on fluidized bed filters in that.

Glad to see this thread wasn't a total dud.

 

[Aaroneous]

Im glad you started this thread. Its something I’m considering for my filter system. Seems to be an efficient and low maintenance filtration process that has proven itself in the wastewater treatment industry. And that’s some nasty water!

The book you don’t have, ha ha, is Marine Reef Aquarium Handbook by Dr. Robert J. Goldstein. It was given to me by the guy I bought my aquarium from. It’s a good book for a beginner like me. Touches on a lot of aspects but not in overwhelming detail. It’s good exposure, then I just research the things that peak my interest; like fluidized bed filters.

Couple excerpts:
“Advantages to fluidized bed filtration:
1. High degree of mineralization
2. Continuous removal of sediment and particles in the overflow
3. Small space required
4. Elimination of need to change sand, because tumbling and friction prevent formation of thick biological mats on sand, as they form on bioballs in trickling filters.”

“Always use silica sand, because aragonite sand dissolves, defeating the purpose of the sand’s providing a self-cleaning aerobic bacterial bed.”