Thread: DIY: Designing and Building a protein skimmer/fractionator

Up early this morning and there's foam coming out of the airlifts again.. so time to get rid of those disolved organics and protein by adding another component to the filter.

The important point about making foam for skimmers is dwell time. This means you can either slow the rate and/or increase the time it takes to flow through by making the pipe longer or making the path the water takes longer (ie zig-zag through media).

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I have an anoxic filter that doubles as an airlift chamber and I did think about adding a mechanism to that with the foam dropping down the back into a small area where there's a hawthorn tree. The only issue is it's likely to smell and cause the plants there to grow nuts. It also complicates the returns as they'd be providing some of the gravity feed which then creates more back pressure and slows the flow rate further.. it would have been no extra energy as air is sent to the airlifts already (although it would have unbalanced the airlift supply making it even more complex to operate). No.. let's keep this simple and it doesn't need to run all the time.

Instead I have opted to augment the newly built UVC that is pump fed by syphoning off some of the pressured return through a 110mm tube with media and an air stone at the bottom. This makes use of two things - I already have some 110mm pipe and some 63mm clamp for piping. The pipe will be a similar design to the UVC. The outlet for the return water is then driven through to the main air powered return. The waste foam (and air) will then go through a pipe to the RDF waste. The tube will be sealed at the top by a pipe flex boot.

The key design points for me are:
* long enough pipe for good dwell time. This means the pipe may be longer than the UV and above the water level of the pond. Hence a pressurised (pumped) input is a good thing. Only issue is that I'm taking the inlet from the dirty side of the drum due to flow constraints. However there is a foam pad to prevent the pump from blocking.
* the output is not pressurised and so needs to flow back to the gravity return. This is because the waste pipe allows water out too hence we don't want that draining the pond accidentally. For this reason the foam return is above the water level maximum (but not far). Although it may not be as predictable as a sluce style fractionator, the issue is the gravity fed flow will always have a varying water level (especially with a drum in the loop). It will remove a large amount of mess though. This requirement means the pipes for the return need to be low restriction (as good practice with all gravity fed designs).
* media making water flow rate slower and giving longer dwell time.
* use of the existing air supply means I'm not wasting air (I'm having to vent some currently as it has more than enough for the system).
* makes use of the parts have lying around (or simple pipework).
* has a cap to stop the foam from rising out of the top of pipe and instead is driven by the flow of air down the waste chute.

So I finally managed to get an 1/2 hour to test some theory using a bucket and old 8klph pump. The idea, with a bucket of pond water, was to see if the pump with air sucked in could generate longer lasting foam.

The results, although not foamy, did make me think, a longer pipe design with longer contact time and smaller bubbles would work better possibly with alot more air.

Also pulling from the unfiltered UVC line will cause alot of debris, and I think I would probably want a water flush to waste to prevent smell in summer.

I also operate an air lift into an anoxic chamber.
The water level in this fluctuates because of the fluctuating level of the clean side of the drum filter between rinse cycles.
The water surface in this chamber collects foam like crazy and I tend to scoop it off with an old plastic dust pan.
I may revisit an earlier idea I had which used the water level changes to trigger a float switch to periodically trigger an electromechanical scraper or even a blower to push the foam up a slight ramp to waste.
Looks like there's no end to the tinkering we can do with this hobby

So I was thinking and watching some other videos on this. Many US folks use water bottles bonded together with a pipe to collect. That got me thinking with the requirement for dwell time, then it's possible that using a tall slimline 100L water butt could be useful with down flow water and using an EPDM bladder at the bottom for the air.

Irritatingly I had one of these butts before but threw it away. I don't think they're solvent weldable so they would need bulkhead connectors to seal properly. However I think the real bad point is that it's rectangular which makes putting in a foam collector more difficult.

Another alternative is a water barrel but this starts taking up space I don't have. There are slim tall circular water barrels only 12" wide but they £100+!

I am rejigging my airlift collection chamber at some point to add a bulkhead connector that will 'drain' the foam once it goes over a certain height.
I have a similar issue to ukzero, it raises up, and if I don't scoop it out, the foam over flows back into the anoxic filter.

Trying to link the foam drain in to the rdf waste is a good idea Nick. I'll see if Its practical for me to do that too, but they're at opposite ends of my filter setup, so it hadn't occurred to me before.

I have 1" stand pipes on all of my returns, hoping they would skim some foam off, but the chamber they are connected to seems to do all the work.
Oh well, best lead plans, don't always go accordingly....
Ignore the plastic cups. When I realized the upstand pipes weren't skimming I just placed something over them to stop me dropping anything down them by accident.

You can see the blue above the scummy brown stripe (normal running water height) where it tries to skim off my parasite treatments even! So I'll have to add a valve to whatever drain I put on it to prevent that.

That's a better view of it in action.
No real dwell time in mine, just up the airlift quickly plus the time it takes to gravity flow out of the chamber via the returns to the pond.
You can see the brown cruddy stains where the foams been overflowing over the collection chamber lip and out over the lid even.

Here's about 12 hour's worth of foam build-up in my anoxic chamber. My gravity system has the air lift after the drum filter and just before before the anoxic chamber - with 110mm gravity return to pond.
You can probably guess why I'm working on an electromechanical gizmo to skim it off automatically as regular removal without relying on me and an old dustpan can only be a good thing!!

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I don't think you need anything too fancy. Just a bulkhead fitting above the highest water line, down at the scummy end. Then that will drain off the foam.

Sorry this has taken a bit of a backseat due to being fired They prefer firing people under 2 years than making them redundant nowdays thanks to the UK employment law changes. So anyone under 2 years has no rights basically (previously that was 1 year).

Anyways, all good and progressing but I was thinking about this again over coffee pond side.

A very interesting point on what actually is skimmate?

https://reefs.com/magazine/elemental...quarium-water/

...I have a couple of spectrometers at work. Mass Spectrometry is a slightly different beast but in 'normal' spectrometry:
The machine shines a Laser through material and measures the light spectrum, which tells you what compounds are most likely to be present. So you'll get lots of results telling you what's most prevalent. Not an exact list of everything that's there, so it's a bit flawed trying to figure out everything that's in a sample. So if you take about a million samples, for example. If the most prevalent thing present is calcium, then that's what the spectrometer will come up with every time.
You are also limited by what's in a spectrometers 'library'. They don't have everything in the world in them for reference so it always tells you the most likely match (from what it has in its library)
They are also not very good on dark, reflective or organic compounds, so it isn't surprising that the test did not provide support for a huge presence of organic compounds.

...long story short.
I wouldn't trust those results...

Good points - I've built my own solar spectrograph, R6000 resolution and 0.9 angstroms bandwidth. An upgrade I had planned would have got that to 0.4 angstroms with 2D scanning but life got in the way.

I'll have a look at it, along with other things I have the time to look at now.