Trickle Filter advice.

[Shane]

Hi everyone,

I'm considering adding a DIY Trickle Filter to my Megabin system as this system won't have as large a GB area as the other system does.

I'm looking for some pro's/con's of different types of media to use inside,

Anything you would or wouldn't recommend me using based on your experiences would be much appreciated.

Cheers,
Shane.

[GaryD]

Hi Shane,

I've been using trickling bio-filters on my mega bin system for 4 years.

I use oyster shells (the flat section) as media because:


It costs me nothing
It offers modest surface area
It doesn't clog
Its downside is that it is heavy.

I've trialed a variety of other media types including styrofoam beads, Kaldnes K1, clay pebbles and gravel.

Everything but large gravel (25mm+) clogs up sooner or later (and gravel is a killer for the weight) and the water begins to channel.

I've used plastic drums and plastic stacking crates to contain the oyster shells.

Ideally, you should put some form of mechanical filtration (like DaveOponic's swirl tank) before the bio-filter......because bio-filters (including grow beds) are more efficient if solids loading is minimised.

I'll put some photos up tonight.

Gary

[Shane]

Thanks for that info Gary,
& Yes, your photo's would be greatly appreciated.

Cheers,
Shane.

[Crusty]

How many fish do you have Shane and how much grow bed?

[GaryD]

Hi Shane,

Here's some images of my mega bin systems with trickling bio-filters.

When I load up a bio-filter, I place each shell to maximise the surface area and ensure even movement of water through the filter.

Gary

[Shane]

Hi Crusty,

System I intend to put the Cat's into is currently fishless cycling, Cat's are currently in my main system (fingerling tank)
System I intend to transfer them into presently it comprises of 1 x 585 litre GB (planted out a week ago & with high pH is currently suffering from nutrient lockout) with an upcoming extension of an extra approx 200 litre GB in the coming weeks + suggested trickle filter....there is no huge rush to introduce them to this system.

I've already moved 12 of the Cat's into 2 x 300 litre systems of their own (6 in each) & they are powering along OK

So this leaves 30 Cat's that I'll eventually have to transfer into the Megabin system.

[Shane]

Hi Gary,
Got to fly (Footy's on now)
Thanks heaps for the snaps they are fantastic ( & much appreciated)
No doubt I'll have a few questions for you this weekend,

Cheers,
Shane.

[Crusty]

Hi Crusty,

System I intend to put the Cat's into is currently fishless cycling, Cat's are currently in my main system (fingerling tank)
System I intend to transfer them into presently it comprises of 1 x 585 litre GB (planted out a week ago & with high pH is currently suffering from nutrient lockout) with an upcoming extension of an extra approx 200 litre GB in the coming weeks + suggested trickle filter....there is no huge rush to introduce them to this system.

I've already moved 12 of the Cat's into 2 x 300 litre systems of their own (6 in each) & they are powering along OK

So this leaves 30 Cat's that I'll eventually have to transfer into the Megabin system.

Hi Shane,

What makes you think you have a nutrient lockout? Is your pH above 8? If not, it may be more of lack of nutrient rather than actual lockout (pretty hard to lock out nitrogen).

So just to summarize your intended system, so I can get my head around it:


1 x mega bin (is it full/half full or other?)
1 x 585L growbed (full/bit from the top of media? what size? what type?)
1 x 200L growbed (to be added later but is part of the plan)
Plus a trickle filter of some size.

Is that it?

and you want to put 20 catfish in it? What species (eel tail catfish?) sorry if you have mentioned that elsewhere, I missed it. What size will you be growing the catfish to?

[Shane]

Hi Shane,

What makes you think you have a nutrient lockout? Is your pH above 8? If not, it may be more of lack of nutrient rather than actual lockout (pretty hard to lock out nitrogen).

Hi Crusty,
pH was originally 8.2, we've had a significant amount of rain though recently & its dropped to 7.8 as of last weekend (& was still 7.8 last night)
Have been dosing with Seasol to give the plants nutrient.


So just to summarize your intended system, so I can get my head around it:


1 x mega bin (is it full/half full or other?)

1 x Megabin, almost full (approx 8-9 cm's from the top)


1 x 585L growbed (full/bit from the top of media? what size? what type?)
Yes, 1 X 585 Litre GB...Media is Hydroton clay balls, GB is filled to approx 4-5 cm's from the top

http://i652.photobucket.com/albums/uu241/Shane3137/th_P1040241.jpg (http://s652.photobucket.com/albums/uu241/Shane3137/?action=view&current=P1040241.jpg)


1 x 200L growbed (to be added later but is part of the plan)
Yep, 1 X 200 Litre additional GB to be up & running within 2-3 weeks.


Plus a trickle filter of some size.
[/LIST]
Yes, although Gary has also suggested I hook up a form of mechanical filtration also.


Is that it?

and you want to put 20 catfish in it?

NO not 20.....initially 30.
Cat's are currently very small (50-60mm)
Within 6 months I will have another system set up to transfer 1/2 of them into.
This will leave 15 Catfish in the Megabin to grow out.


What species (eel tail catfish?) sorry if you have mentioned that elsewhere, I missed it. What size will you be growing the catfish to?

Yes Crusty the Cats are Tandanus Tandanus,
Size, hoping for at least 400 gram.

Your thoughts on the above set up would be appreciated.

Cheers,
Shane.

[Shane]

Hi Shane,

Here's some images of my mega bin systems with trickling bio-filters.

When I load up a bio-filter, I place each shell to maximise the surface area and ensure even movement of water through the filter.

Gary

Hi Gary,

Are you running straight aquaculture in those snaps with just trickle & swirl filters?
Or are you pumping also to GB's on the other side of the shed wall?

Cheers,
Shane.

[Shane]

Gary,

When plumbing your trickle filter inlet,
Does the water enter via a single inlet or via a spray tube?

Thanks,
Shane.

[Crusty]

Hi Crusty,
pH was originally 8.2, we've had a significant amount of rain though recently & its dropped to 7.8 as of last weekend (& was still 7.8 last night)
Have been dosing with Seasol to give the plants nutrient.You have already planted it, without fish? You are going to be dosing with Seasol for awhile then.





1 x Megabin, almost full (approx 8-9 cm's from the top)
Yes, 1 X 585 Litre GB...Media is Hydroton clay balls, GB is filled to approx 4-5 cm's from the top
Yep, 1 X 200 Litre additional GB to be up & running within 2-3 weeks.
Yes, although Gary has also suggested I hook up a form of mechanical filtration also.
NO not 20.....initially 30.
This will leave 15 Catfish in the Megabin to grow out.
Yes Crusty the Cats are Tandanus Tandanus
Size, hoping for at least 400 gram.

Your thoughts on the above set up would be appreciated.

Your grow bed (585L) will handle all 30 of the cats provided you have some form of small solids filtration before the bed. Though crowding them in a 700Liter tank may not be a great idea, so two fish tanks will be handy. Especially, when you go to clean the fish tanks out (you will need to regularly), with lots of fish, this task can be quite difficult for you (or the lads) and very stressful to the fish. This puts your density at harvest to 17kg/m3 with one tank, which is getting up there, so you are going to need some good aeration. At density you will be feeding about 240 grams per day.

If you were running that on a trickle filter by itself (for bypass) you would need a 125Liter filter. As a shared load between the beds and a filter the filter could be smaller but if you are to have a filter, it should be designed to handle all of the load. I would stick to adding a swirl filter to the fish tank outlet, the grow bed (plus a 200L as safety) will be able to handle the load, provided they are kept free of solids.

Either way, to handle that amount of fish in a small space (without even more growbeds), a small 20 or 30 liter swirl filter will keep the muck out of the beds and permit the greater fish load. The waste, as with the UVI system, can be used for your earthen gardens. Personally, I would pass up on the trickle filter for now.

[Shane]

Hi Crusty,

It doesn't bother me to dose with Seasol for awhile, if it means slower plant growth until fish transfer, then so be it.
Thanks also for the above info you've provided regarding the above system.

Cheers,
Shane.

[GaryD]

Hi Shane,


When plumbing your trickle filter inlet,
Does the water enter via a single inlet or via a spray tube?
I use a plastic bowl (with a flat base) with lots of 5mm holes drilled in it as a water distributor. Think about an old-style shower head and you'l get a sense of how it works.


Are you running straight aquaculture in those snaps with just trickle & swirl filters?
Or are you pumping also to GB's on the other side of the shed wall?
I've run them both ways. At the moment, I have two of them operating and they are both set up as basic recirculating aquaculture systems. Each week I pump some water out of them.......to keep nitrate levels and suspended solids under control. We use the water on our raised bed gardens.

Gary

[Privatteer]

It doesn't bother me to dose with Seasol for awhile.
Adding some ammonia and fishless cycling safer for your new fish anyway.

Top layer of mine is a plastic sheeting. Under that is 10 layers of a co**** sponge similar to what you see around pond pumps etc. (got that cheap)
There is another full layer of the plastic stuff held about 50mm from the bottom of tub. Bottom drain.
Its a lot deeper than it looks in the pic.

Worked well for me but I am not putting a big quantity of solids into it. Settling tank before.
http://www.users.on.net/~freedomfries/Pond/Filter.jpg

[Shane]

Thanks for all the different pics so far,
That & the additional info provided makes the topic so much easier for me to understand,

Cheers,
Shane.

[GaryD]

Hi Shane,

Before I started using mechanical filtration, I always chucked a handful of worms into my trickling bio-filters. They serve the same purpose there as they would in a grow bed. These days, we still put a few worms in our bio-filters since, even though there's less organic matter in the bio-filter, they eat bacteria and keep the bio-filter in peak operating condition.

Contrary to what you may have read elsewhere, properly designed bio-filters (particularly those using oyster shells for media) do not clog and you can put reasonable volume through them.

A good trickling bio-filter will provide for greater nitrification and aeration than a grow bed of a considerably larger size......particularly if the grow bed is operating on something like the commonly used 15 minutes ON/45 minutes OFF pumping regime.

Gary

[Crusty]

A good trickling bio-filter will provide for greater nitrification and aeration than a grow bed of a considerably larger size......particularly if the grow bed is operating on something like the commonly used 15 minutes ON/45 minutes OFF pumping regime.
While the last part of that statement is true, the first bit would need a little more detail Gary. If you were to take the two surface area estimate of 90m2/m3 for clay and 200m2/m3 for trickle filter media (not oysters), then you could say "a trickle filter half the size in media volume of a growbed (without organic loading) with 20mm expanded clay media will convert the same amount of ammonia". The other side of the discussion is you can achieve 200m2/m3 in a gravel packed filter and achieve a removal rate of 0.15kg/day in a growbed where as a trickle filter of the same size will have a TAN removal rate of 0.09kg/day, so from an TAN removal efficiency, the trickle filter would need to be 40% larger to match the grow bed...

[GaryD]

Hi Crusty,

I'm a bit confused.......


If you were to take the two surface area estimate of 90m2/m3 for clay and 200m2/m3 for trickle filter media (not oysters), then you could say "a trickle filter half the size in media volume of a growbed (without organic loading) with 20mm expanded clay media will convert the same amount of ammonia".
If I read this correctly, the trickle filter containing half the volume of a comparable grow bed would convert a similar amount of ammonia......and this is so because of the greater surface area of the trickle filter media.



The other side of the discussion is you can achieve 200m2/m3 in a gravel packed filter and achieve a removal rate of 0.15kg/day in a growbed where as a trickle filter of the same size will have a TAN removal rate of 0.09kg/day, so from an TAN removal efficiency, the trickle filter would need to be 40% larger to match the grow bed...

Sorry......this is where I came unstuck......it has the appearance of contradicting your first statement. Can you work me through it?

Also, what is your view on the following......

In looking at the nitrification and aeration efficiency of a bio-filter, the volume of water that flows through it must have some bearing. Right?

I believe that a trickle filter of a given volume (and assuming a similar media surface area) where water is flowing continuously, has to be more efficient (in all respects) than a flood and drain grow bed of the same volume......where the water flow is intermittent (like the commonly used 15 minutes ON/45 minutes OFF pumping regime). Right?

Also, do your calculations assume the use of mechanical filtration?

A grow bed has to become less efficient over time due to the build up of solids. Even where these solids are spent, they occupy void space that would otherwise contain air and water. Is this correct?

Gary

[Crusty]

Hi Crusty,

I'm a bit confused.......


If you were to take the two surface area estimate of 90m2/m3 for clay and 200m2/m3 for trickle filter media (not oysters), then you could say "a trickle filter half the size in media volume of a growbed (without organic loading) with 20mm expanded clay media will convert the same amount of ammonia".If I read this correctly, the trickle filter containing half the volume of a comparable grow bed would convert a similar amount of ammonia......and this is so because of the greater surface area of the trickle filter media.
In that statement, yes you are right and only looking at it from a surface area only.



The other side of the discussion is you can achieve 200m2/m3 in a gravel packed filter and achieve a removal rate of 0.15kg/day in a growbed where as a trickle filter of the same size will have a TAN removal rate of 0.09kg/day, so from an TAN removal efficiency, the trickle filter would need to be 40% larger to match the grow bed...Sorry......this is where I came unstuck......it has the appearance of contradicting your first statement. Can you work me through it?
Yes it does contradict the first statement as this time we are looking at it from a TAN (total ammonia nitrogen) removal with the same surface area. This second statement suggests that a growbed can achieve similar surface area as a trickle filter and it can have a higher TAN removal rate, which is also contradicory to your statement "A good trickling bio-filter will provide for greater nitrification and aeration than a grow bed of a considerably larger size". This is merely an example to caution against too much guesswork when designing your filtration.

An example that can be confusing, is your oyster shell filter is acting very much like a packed bed only it is not submerged, but still has the same inherent issues as the submerged packed bed, such as clogging and organic loading purely as a result of the low void space ratio. This low void space would bring into question it's capacity for degassing or even gas diffusion.


Also, what is your view on the following......


In looking at the nitrification and aeration efficiency of a bio-filter, the volume of water that flows through it must have some bearing. Right?
I believe that a trickle filter of a given volume (and assuming a similar media surface area) where water is flowing continuously, has to be more efficient (in all respects) than a flood and drain grow bed of the same volume......where the water flow is intermittent (like the commonly used 15 minutes ON/45 minutes OFF pumping regime). Right?
Also, do your calculations assume the use of mechanical filtration?
A grow bed has to become less efficient over time due to the build up of solids. Even where these solids are spent, they occupy void space that would otherwise contain air and water. Is this correct?



Yes
Yes but that is only one side of the argument. If your trickle filter had the same flow rate, the results will be the same.
Yes
Yes

[GaryD]

Hi Crusty,

Thanks for that......very helpful.


This second statement suggests that a growbed can achieve similar surface area as a trickle filter and it can have a higher TAN removal rate........

If I understand this properly, the statement only applies if:

the rate of flow is the same.
there is mechanical filtration upstream of the grow bed.
I think you'll agree that these are important issues because the flow rate through many grow beds is determined by the autosyphon......and very few flood and drain systems are fitted with any sort of mechanical filtration. Indeed, AP fundamentalists boast that they use their grow beds as solids filters as well as bio-filters.


An example that can be confusing, is your oyster shell filter is acting very much like a packed bed only it is not submerged, but still has the same inherent issues as the submerged packed bed, such as clogging and organic loading purely as a result of the low void space ratio. This low void space would bring into question it's capacity for degassing or even gas diffusion.

Remember, my oyster shell media comprises whole shell (as distinction from crush shells) so I have not experience clogging. As for void space, I'd say that the void space would be equal to (if not more than) that of gravel......with the obvious downside that surface area would not be so high.

I've dismantled this sort of bio-filter before and my observations were that correctly placed oyster shells ensure fairly even water distribution across the media and there was very little in the way of solid waste among the shells.

Because my bio-filter barrels have a side outlet (rather than a bottom one), I do get some build up of sediment in the bottom.....which I can pour off at regular intervals. If I build such bio-filters in the future, I'll make sure that they drain directly out of the bottom of the barrel.


Gary

[Shane]

Hi,

Just regarding the 'Rate Of Flow',

To be at its most effective, what should the rate of flow for a trickle filter be approximately?
Example: If you had a 50 litre container filled with oyster shells, roughly how many litres of water should you be pumping through it per minute (or hour)?

Cheers,
Shane.

[Crusty]

This second statement suggests that a growbed can achieve similar surface area as a trickle filter and it can have a higher TAN removal rate........
If I understand this properly, the statement only applies if:


the rate of flow is the same.
there is mechanical filtration upstream of the grow bed.

I think you'll agree that these are important issues because the flow rate through many grow beds is determined by the autosyphon......and very few flood and drain systems are fitted with any sort of mechanical filtration. Indeed, AP fundamentalists boast that they use their grow beds as solids filters as well as bio-filters.
Yes on both counts Gary. Also keep in mind that if the filter is treated in the same manner as the grow bed, then it will act the same. So adding pre-filtration and a constant flow rate will have a positive benefit to both applications. The fundamental flaw in the flood and drain designs currently about is, the flow rate is limited by the function of the auto syphons. Which counter acts the current rule of thumb about the traps, a flow rate of 1 x the fish tank volume. I have a fish tank of 1000 liters so I plan for a 1000 liter per hour pump. Yippy, then I dirvert 50% of the flow directly back into the fish tank to make the syphon work..... What happened to the flow rate suggestion?

We have talked quite a few times on solid accumulation in the grow beds, while it may be great for plant production to some degree and people with no solids capture prior to the grow bed will boast "marvelous green growth" in their growbeds but will without a doubt have next to no fish in comparison to those that are prefiltering their water in some manner prior to the growbed. To make aquaponics easy, simply add the fish food directly to the bed, wet it and be done with it, because that is effectively what you are doing with a submersible pump in the fish tank. I know because, we used to use out of date barra feed to fertilize the fruit trees and they grew like mad... I suspect this is similar to the current model of "aquaponics", just load the bed up and get great plant growth at the expense of the fish and then carry on about balance.


Remember, my oyster shell media comprises whole shell (as distinction from crush shells) so I have not experience clogging. As for void space, I'd say that the void space would be equal to (if not more than) that of gravel......with the obvious downside that surface area would not be so high.......
I am sure your filter works sufficiently Gary. The danger is generalizing their capacity and efficiency. How much load does one of those filters carry on its own? No point in telling me how much fish it carried, it is the feed per day that is the measure.

[Crusty]

Hi,

Just regarding the 'Rate Of Flow',

To be at its most effective, what should the rate of flow for a trickle filter be approximately?
Example: If you had a 50 litre container filled with oyster shells, roughly how many litres of water should you be pumping through it per minute (or hour)?

Cheers,
Shane.With trickle filters, the flow rate is governed by the oxygen demand of the fish, so in your case Shane I am not sure. Perhaps Gary has number that will work. I would suggest the entire system volume per hour and increase that as the water temps get over 22C.

[GaryD]

Hi Crusty,


I am sure your filter works sufficiently Gary. The danger is generalizing their capacity and efficiency. How much load does one of those filters carry on its own? No point in telling me how much fish it carried, it is the feed per day that is the measure.
Your point is well made. I think there are better bio-filters......but they've proved useful in my journey to a better way of doing things. As you've said, none of the bio-filter options is going to operate at anything like their full potential without mechanical filtration.

Gary

Gary