Gary's 3 Mega Bin System

[Crusty]

Hi

My understanding of polygeyser filters is they run on high pressure.

[jet]

Hi Crusty, thought youd dissappeared
They make an open top type so it must be gravity fed type
They do have pressurized ones too, and thats probably what your talking about. Seems Polygeysers for higher flow rates - Im guessing due to cost
Ive never used one but flushing concept looks good as an add on.
Looking at specs using self cleaning every 2 hours or so they halve the amount of media used for a certain flow rate, which makes sense.
If we had High pressure air a small solonoid and timer could flush like this too. Thats how a Bubble bead setup works.

[GaryD]

Hi John,

Thats how a Bubble bead setup works.

I didn't think a bubble bead filter has air connected. I was under the belief that it exploits a venturi action to boil the beads as they drain from the top section of the filter to the lower section.......dislodging the solids along the way as they drain from the filter.

Gary

[jet]

After looking properly, you are right - just has "air inlet" indicated, after hearing price I didnt look much harder. Just a check valve and the air coming in is replacing water leaving. Nice design, the throat or waist in the enclosed vessel is needed, and would be difficult to replicate cheaply.
Regarding the requirement for a pump, the only major headloss in either sort of filter is pushing water through media which gets harder as it fills up with rubbish. We still have this issue no matter if the filter is auto flush or not. By cleaning automatically we reduce the requirerment to store the rubbish in the media for so long and can therefore operate lower headloss OR have a smaller media for same flow rate.
We could alter the shape of the media pack and change things too, deeper = finer filtration (more headloss), wider = more storage area (lower headloss, less flushing)
An auto geyser type uses 50L media whereas BBF needs over 110L for ~ 1kg feed/day

[GaryD]

Hi John,

It seems that much of what you pay for the Polygeyser, or the bubble bead filter, boils down to being able to clean the beads without becoming too 'hands on.'

Personally, I'd be prepared to pay for more media and get a little more 'hands on' in order to save many hundreds of dollars. Installing an air manifold and boiling the beads at regular (even daily) intervals is very do-able.

I beginning to think that the sort of densities that are achieved in a commercial recirculating aquaculture system come at a price.......and high pressure (read expensive) pumps are just part of the picture. I believe that, somewhere between the two ends of the RAS/basic flood and drain AP system continuum, we have what I'm looking for.......cost effective and safe fish production.

Gary

[Crusty]

There are air assisted back-wash bead filters but they all run on higher pressure than most use. I had one that ran at 15psi which increased to 25psi which was the limit of my pump, at which time it needed back-washing.

[jet]

Yep both comments are correct, Garys spot on regarding media volumes, just add more media will work well, keeping in mind you want to increase surface area rather than depth, BUT once you get past a certain size cleaning by hand becomes harder, also filter housings get bigger and cost is exponential on structurally increasing filter size.
The addition of auto flushing and pressure/energy (which overcomes headloss build up) become better value than larger filter structures. Often in my industry pressure is required anyway to move water around in reasonable pipe sizes and make layouts workable so its just adding a larger pump rather than a whole new addition. Having even lower pressure like 10-20 psi permits a lot of design freedoms. The filter Crusty mentioned is running out to 7 metres headloss, In our gravity setups 0.2 metres loss is enought to stop the system cycling.
We use Pressure diferential switches which watch headloss through filters and begin backwash cycle once it reaches say 10 mhd. Often they flush on time too as when using pressure to push water through it can pack media tighter not allowing good cleaning when it finally does block up.

I reckon the 2000-4000lph is getting to the limits for realistic DIY gravity media filtration. If you have the time to clean say twice a day, no problem. I cant rely this is going to happen so need auto help I think. Im going to try and setup bypass too in case filter clogs early.
I regards to upsizing media area, a 200 l drum with media in top has more than 4x the surface area of the bucket. 50 L media makes it just 10 cm thick though. Will this be deep enough?
Loose the nice all in one feature of the bucket setup though.

[GaryD]

Hi John,

......just add more media works well, keeping in mind you want to increase surface area rather than depth, BUT once you get past a certain size cleaning by hand isnt an option, also filter housings get bigger and cost is exponential on structurally increasing filter size.

For the backyard systems that I design and operate, cleaning by hand is not an issue.....and (relative to the overall size of the system) nor is the need for (or cost of) slightly larger barrels or tanks.

Lose the nice all-in-one feature of the bucket setup though.

The dual purpose function of the filtration modules is a "nice to have" rather than a "must have".....it just makes for a smaller footprint.

My next system will be based on a 1000 litre round aquaculture tank and two 250+ litre swirl tanks. Each of these will be dual purpose......one will be a swirl tank/packed media filter (and I may use beads in that) and the other will be a moving bed bio-filter and sump combination.

There will be much greater opportunity to add more filter media (both for solids capture and for moving bed bio-filtration) in that system. The increased solids capture and removal (and nitrification) capabilities of this system should be reflected in its productivity and (dare I say it) resilience.

Gary

[Jackalope]

Hi Jackalope,

I'm unable to grasp exactly how your idea works.....any chance of a diagram?

Gary

I'm not that computer savvy! LOL

[GaryD]

Hi,

The adventures around the swirl tank continue.

When we first set the system up, we used a 20 litre plastic drum full of Kaldnes K1 media as a packed media filter......which we positioned over the outlet pipe in the swirl tank.

I discovered that the algae plugged the holes in the bucket which then made the bucket (complete with media) float off the outlet pipe.......a nice bit of fail proofing but useless as a filter to trap suspended solids.

We then set the K1 media free in the swirl tank but that restricted out view and we were a bit concerned that it might limit the swirl action of the filter.

We changed the bucket for one with the bottom cut out......and we placed the K1 media into the bucket (it remains positively bouyant). That worked in that it allowed the swirl action but it took longer than we wanted to clean.

So, then we liberated the media again. The secondary filtration was good (it was catching plenty of suspended solids) but, when we removed the media to check on how it was impacting the swirl action, we confirmed that the swirl filter was acting as a sedimentation tank......and that the solids were clinging to the walls of the filter rather than gathering around the dump point as they should.

Today, I replaced the original 20 litre bucket over the outlet and filled it with clay pebbles. The weight of the pebbles is such that the bucket will no longer float and, once they get coated in bio-film, they should prove to be reasonably effective at trapping suspended solids.

Anyway, time will tell.

In the meantime, I get a nice little inner glow whenever I open the dump valve (at least twice per day) and that slug of black muck shoots out into the bucket. I luv swirl filters.

Gary