Recycled HDPE swarf

[cnwent]

I run a small fabrication company making furniture from recycled HDPE (generally from milk flagons). We get a certain amount of waste which we try to recycle. Offcuts are not a problem but we generate quite a bit of swarf which our suppliers will not accept. I was wondering whether this would have any applications. I have seen suggestions of using shredded milk flagons as grow bed media and ground up tyres as bio filter material. Do you think this swarf would be of use? We get very fine chippings which would probably be too fine and light, but we also get lots of long twisted bits from drilling the material which would probably be useful. Does anyone foresee problems with this? I have a few spare 220litre barrels which I was thinking of filling with swarf to make a biofilter. One issue which might be a problem is that the smaller particles have a strong static charge and can be a bugger to get of you.

Chris

[GaryD]

Hi Chris,

There may be some scope to use the swarf in a packed media filter.....for the removal of suspended solids. A

A mechanical filter of this type is placed before the bio-filter. You'd just place it in a 200 litter drum and up flow your water through the swarf media. You would clean it at pre-determined intervals - I'd suggest that you "boil" it up with an air pump and then drain the watery solids out of the system......for use on your soil-based gardens......or even for aerobic digestion. Once digested, you could re-introduce the mineralized nutrients back in to the system and feed the sludge to your worms.

Gary

[cnwent]

Hmmm interesting. So I assume that I would need to pack them in pretty tight then. Would it be as simple as a barrel rammed full of the swarf with an outlet at the bottom (or the top?) for the water? Not sure I understand what you mean by boiling it up with an air pump. I am planning on using a 1000 litre IBC as the fish tank, is the 200 litre mechanical filter a bit on the large side? if I understand you correctly I would be taking the waste water from the fish tank, passing it through the swarf mechanical filter with the liquid waste going to a bio filter and the solids going to an anaerobic digester for further processing. The liquid produced by the digester then goes to the bio filter (and then back into the fish tank - is this risky?) and the solids out to a worm bin for final processing. Sounds like a pretty good plan...
Chris

[GaryD]

Hi Chris,


So I assume that I would need to pack them in pretty tight then. Would it be as simple as a barrel rammed full of the swarf with an outlet at the bottom (or the top?) for the water?
No.....just chuck them in the barrel as they fall. The idea is that the water flows upwards through the media. As the filter becomes operational, bio-film will form on the swarf.....and, as the water wells up through it, the solids stick to the bio-film.


Not sure I understand what you mean by boiling it up with an air pump.
You use an air pump to blow air through the swarf and water and the agitation that produces dislodges the built up solids on the swarf......and you just drain them out through the bottom of the barrel.


I am planning on using a 1000 litre IBC as the fish tank, is the 200 litre mechanical filter a bit on the large side?
No.....it's a good size for use with an IBC.


if I understand you correctly I would be taking the waste water from the fish tank, passing it through the swarf mechanical filter with the liquid waste going to a bio filter and the solids going to an anaerobic digester for further processing.
That's just one way of doing it. You can also make a basic swirl filter out of your barrel. That will get rid of the sedimentary solids.....and it will be easier to clean out than a barrel full of swarf.


The liquid produced by the digester then goes to the bio filter (and then back into the fish tank - is this risky?) and the solids out to a worm bin for final processing.
I probably wouldn't couple a digester up to a fish tank of that size. You can put the solids into a barrel with an air stone and bubble them away for a few hours and then let it stand until the solids settle out. Decant the nutrient-rich water and put that back into your system......and give the remaining sludge to your worms.

It's probably useful for you to describe what you have in mind (whether you're going to run a simple recirculating aquaculture system or whether you plan to have gravel grow beds)......so that we are not working at cross purposes and can sort out any major issues at an early stage.

Gary

[cnwent]

You have previously recommended a simple recirculating aquaculture systems due to our chilly climate, which I can then use with our existing raised beds or possibly wicking beds when it is warm enough to grow and 'unplug' when everything cools down a bit. Maybe I should wait until I have got your book and studied it a bit further before I take up too much of your time - it is easy to get carried away with this and think about it all the time and ask lots of questions about simple things which would be easily answered by studying the basics! I had a closer look at the swarf and it is nearly all fine flakes from sawing rather than larger swirls of plastic from drilling, so I won't persue this line of thought and will look into a swirl filter instead.

Cheers
CHris