Backyard Aquaponics
A place to discuss aquaponics

Basically there are 2 types of solids in an aquaponics system
1- Settleable solids
2- Suspended solids

And we use 2 different types of filters for these respectively
1- Radial Flow Filter (RFF)
2- Static Upflow Filter (SUF)

I understand RFF and can build one easily.

What are the inner workings of a SUF? I searched on the net but the thing looks like RFF with some filtering material in it. Or may be I couldn't put good search criteria in Google.

Can someone please explain the difference with an easy to understand drawing?

as far as i know a static upflow is just a container with media whos flow comes in the bottom and out the top... with static media. I.E like a moving bed filter, but no moving media.

Thanks Yavi, so the pictures I have seen on Google images were right

So would a sand filter such as a pressurized sand filter be considered a static filter? Just doesn't have the upflow part.

yea that would be a type of static filter, so is a media bed.

Having terminology aside, IMHO yes, sand filter is a static filter that removes the suspended solids.

I am also interested in the maintainability aspect of these filters.
Obviously RFF is very easy to clean. Isolate the filter, open the tap and let the sludge go into a worm farm or in a bucket.

SUF would be a little harder than RFF as the static media in it needs to be removed, pressure washed and put back again.

you mean you doubted goigle

Both Andy (Dasboot) and scotty have upflow filters. Think scotty uses that expensive stuff and Andy uses plastic bottlecaps (HDPE).

Edit

I think scotty has a combined RFF and SUF.

Actually if you do it right a SUF is relatively easy to clean and doesn't require you to remove the media. Just use static media that floats on the surface around the exit pipe. All the solids have to pass through this to get to the outflow. To clean the filter just turn off the inflow and outflow then agitate the media to release the trapped solids and drain the filter out the bottom. Repeat if needed then turn the flow back on.

You could construct a static upflow filter with a non floating media like sand and they often use these at water treatment plants. If I remember right it called slow sand filtration but I could be wrong about this .

Note: I usually just explain that a SUF is for suspended solids but I do this because you would normally have an RFF first so that you wouldn't have to clean the SUF as often. I've said it before but I'll mention again that a SUF will actually remove both settleable and the suspended solids if there is no RFF. It acts like a 3 dimensional sieve. I have one running without an RFF and it's setup to allow the water to bypass some of the filtration if the filter media blocks up (basically the media floats higher so water tops the outlet without passing through all of it). It's very simple to do.

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+1 on those last comments except I no longer have an RFF (haven't for a few years), I'm not sure what to call it, it is in the old RFF barrel but it's more of a settling tank that ends in a SUF .

Thanks for the reply Scotty.

My next question is what are the suitable media to use in SUF? Like old bird nettings, onion sacks, coffee sacks, old stockings. Should I stack them from top to bottom; coarse to fine? Especially if I am going to use only SUF without an RFF.

What others are doing?



It certainly is Tonzz

You can use lots of different things for media but if you want it to be easy to clean you should use something that's easy to clean by agitating or stirring. None of the things you mentioned are particularly easy to clean and they'd probably all have to be removed to clean them. I use K2 media which is a bit pricey. Dasboot came up with the idea of using plastic bottle caps which can be really cheap if you can find them in mass locally. Plastic beads would also work so long as they can't pass through your strainers. Whatever you get, for ease of cleaning you want it to float so that it forms a layer at the top of the filter and you want the mass to break apart during cleaning so that it can release the trapped solids.

With K2, beads or bottle caps, there is no stacking, just throw them in and they'll form a floating layer at the top all around the outflow. The size of the solids that pass through the filter is determined by how thick the layer is and how big the media you use is, flow rate also plays a role. Too large of particles getting through - throw in more media or smaller media. Filtrations too good - reduce the amount of media or go with larger media.

You don't need anything else in the tank - just an inflow, an outflow, a bunch of media between them and a drain to dump the collected solids. You'll also need strainers to prevent loss of media on all openings and a way to mix for cleaning. If you want to economize on the media and only have a few hundred gallons to filter, you might do something like this -



The inner bucket is where the SUF media will be. The outer bucket will likely be a swirl filter. The water comes into the upper pipe and goes around the outside and down toward the bottom then up through a mesh basket into the bucket of media. The water travels up through the media and over the outflow.



Showing the strainer over the outlet. If the media blocks up too much the media level rises and some of the water will bypass the filter so the whole thing won't overflow.



The outer container in this case is a 20 gallon Sump container made from the same material as the rubbermaid stock tanks I use. The inner container is a 5 gallon food grade bucket. The drain is at the bottom but hasn't been added in these pictures. I'm also going to be trying this design as a mineralizer tank with a built in SUF filter.

If you want to build the SUF without that inner bucket then the inlet is near the bottom below the media layer. The outlet for filtered water is at the top and the drain is at the bottom. Making it without the bucket would increase the filtration capacity or reduce the frequency of cleaning.

Hope this gives you some ideas, just ask if you have questions .

Thanks Scotty. Great info as usual.

Okay, I am thinking of a solution now for the media. What about gravel size charcoal. Would this remove too much of the nitrogen from the system leaving the plants without nutrients?

I can then bury the charcoal in my garden as activated bio-char during the media change and cleaning.

Or, I have pieces of HDPE cut from the IBCs laying around. I can process those with my table saw to create curly pieces which will be a hell of a job but might give me a media with lots of surface area.

Otherwise I will start collecting plastic bottle caps.

While a media that floats would be better one of these might work (I don't think either will float for very long). You could put them in net bags of some type and suspend them on a rack above the inlet until you get bottle caps.

I'm not sure about the biochar but you can probably find out online or there may be some people who know that are on BYAP. My gut says that it would remove too much initially but that that wouldn't last and you'd be OK using it and then discarding it in the garden bed but I'm not really sure . The HDPE would work but it's a lot of work which is repetitive, boring and potentially hazardous to do and then you'll have little plastic bits in the system for generations to come. I wouldn't go there.

Thanks Scotty

I've found these guys on Ebay for bio balls.
I am thinking of ordering some to solve the problem once and for all.

The bioballs would probably work, depending on which size you get the spaces between them will be large which means that the particles passing through could be large as well so you do need a thick layer (true of bottle caps as well). On the other hand that's a really good price from the looks of it and with enough in your container it should work. Nothing prevents you from mixing different media together, you could add bottle caps or other media to the barrel later, if you need better filtration and didn't get enough of these. These are really designed for biofiltration both aerobic and anaerobic from the looks of them and would work better in an MBBR or a trickle filter to help along nitrification (the internal sponge looks to me like it is probably going to be an anaerobic environment with some denitrification going on in most cases). Just clean the filter regularly to keep the denitrification to a minimum unless you want to remove some nitrogen from your system.