Looking for help with filtration

[Lakeside]

I'll try to keep this as brief as possible. I am one of 23 householders who are all shareholders of the limited company which owns a piece of amenity land (in the middle of our houses) in a village called Irthlingborough in Northamptonshire. A large part of the land is given over to what is grandiosely described as a lake but is really a 2-level pond with a weir between. The ponds are fed by the piped outpourings from an abandoned mine further up the hill, and the water then proceeds through our ponds to an outlet pipe which in turn feeds into Irthlingborough Lakes, part of the River Nene water meadows and a Site of Special Scientific interest. The picture of most of the upper pond below gives an idea of the area and size.

The ponds have become infested with Australian Swamp Cropweed (Crassula Helmsii) and some of the residents have been busy digging out several tons of it on to the banks to dry out before we dispose of it: see below.

(lower part)

(part of upper pond)

I have constructed a rough and ready filter across the outlet, consisting of an ultra-fine mesh across the outlet and a slightly coarser mesh in front of that to limit the flow of leaves etc. (Pictures to follow later)
The problem is that the fine filter clogs rapidly, particularly when we are actually raking out the weed, and the water level rises very quickly. At this time of year the area is rarely used and I am concerned that we may cause the pond to overflow and damage houses and gardens lower down the hill.

Any suggestions on how to stop the weed going downstream and infesting the SSSI (and therefore possibly us being prosecuted) while allowing water to flow freely would be very welcome. We have no fish in the lake and none of the residents is an expert on ponds. I also apologise if this is posted in the wrong part of the forums.

Many thanks in advance for any assistance anyone can supply.

 

[MitchM]

Welcome!
You may find good advice over on Pond Boss.
They deal with larger natural ponds/lakes like what you are dealing with.
Here's a link to their forum:
http://forums.pondboss.com

 

[Tula]

Welcome What a lovely setting

 

[Lakeside]

Thank you both (Tula and MitchM) for taking the trouble to post. Thanks, too, to MitchM for the link: I'll try there in a minute.
It doesn't look as if I can edit my original post, so I'm going to describe my filter now and hope that is acceptable.

The outer coarse filter works quite well, but obviously allows small fragments through. The inner fine filter also does what it is supposed to, until it gets choked up. I thought the second fine filter (which I designed to be easy to pull out and clean) would help trap some of the fine detritus, but most of this just floats off when we remove this filter and is then sucked into the inner filter. Incidentally we have no idea what the numbers on the scale at the right are supposed to represent: the bricks make it clear that the graduations are somewhere between inches and feet!

Thanks again to both of you.

 

[Lisak1]

Oh my gosh - so pretty! And WOW that's a lot of pond weed!

I think putting any kind of filter on a pond this size - with flow through on top of it - is going to be a challenge. Every pond filter ever designed or built will clog eventually, and as you noted, cause water to back up and possibly overflow.

I second Mitch's suggestion to post this question on Pond Boss! Good luck!

 

[brokensword]

It seems to me if you can get rid of the pond weed, you'd be golden, right? I'd look to see if you can get some sort of natural solution, like fish (or turtles, ducks, etc) that eat the weed. Too, I'd limit the weed's population during early spring. Here where I live, we have a similar problem, though it's self-inflicted, in the form of cattails. They're trying to choke out a 2 acre natural pond at the end of my street. Controlling is the only way we're ever gong to see them NOT take over, so we spray (at the appropriate time) and wait for die-back. I'd suggest this may be your best option, unless you can find something that eats this weed fast enough to not have a problem. We also treat the underwater plants on occasion when they get so numerous that the pond looks like a forest. Works wonders, but as I said, our pond is self contained with an overflow.

Re your filter, short of daily/weekly maintenance, not sure how you're going to keep up. Of course, the larger your filter, the less maintenance but am not sure you want to increase the size. Is it possible to get ALL the weed out and then control on a timely basis thereafter? Is this weed originating from somewhere upstream?

Just brainstorming; maybe some is useful to you.

Michael

 

[Lakeside]

Michael,

Many thanks for your helpful reply. We are in the middle of a project to get all the weed out, although that is almost certainly an impossible task as this invasive weed can self-propagate from tiny fragments. I reckon we have extracted over 15 tons so far, and have a huge disposal task ahead as well! We do intend to try to keep on top of the problem from now on, although chemical control is not always very effective. In case you or anyone else is even vaguely interested I attach a pdf extract from UK Department of the Environment guidance on controlling this stuff. No mention anywhere that any life form eats it at all.

Jim

 

[brokensword]

Seems you do have a problem; hard to believe chemical measures aren't more effective (according to what I read) but probably due to anything REALLY effective is going to impact other flora and fauna. I did read that grass carp will eat your weed (not their first choice) but there can be problems from having those in your pond, too. Any chance you can do the 'cover with black tarp' trick? Guess it would depend on how large your pond(s) are and funds you have to spend, but I got the idea that's one of the more effective.

Re your tons of weed disposal; can you crate a compost pile somewhere and after decomposition, use it as soil amendment or augmentation? It's what I do with any of my pond plants that begin to over-grow their welcome. Might at least save you $$ re hiring for disposal.

Re your filter issue; not sure my method would help, but thought I'd throw it out there just in case. You'll have to see if you can adapt to fit your situation. What I went to is an aquarist's 'sock filter' because I get a lot of filtering area. The idea is instead of pushing (or pulling) your water through flat layers (or vertical in your case) padding, the water from my pond enters a filter drum and a bag, which stops the fine particles (and some larger sizes too) as the water passes. It certainly cut down on maintenance as instead of the proposed 300 sq in or so, I ended up with over 1400 in the same barrel/drum. So, maybe you can set up some sort of 'sock' that catches the flow after your coarse filter and have it accessible by attaching 'ropes' to pull it ashore and dump/clean. You could make this sock as large as you felt comfortable pulling up. Then you can rinse if by turning it over and then setting it back up again. You'd then go longer between cleanings (at least) but would prob need additional help hauling and dumping.

I'd have additional 'plastic chicken wire' as a cage around your sock to give it more integrity re pulling, as well as (in my case) some sort of screen on the inside prior to actual filter material. This helps keep the filter material from tearing/breaking when you're pulling and cleaning.

Just an idea.

Sorry you're having the issue but it really is a lot like the underwater weed issue at our association's large pond down the road, which we periodically dose with the chems.

Michael

 

[Lakeside]

Michael,
Many thanks again for all your input: as you say we seem to have similar issues.

You are almost certainly right that there are chemicals which would kill the weed but would kill everything else as well (including the newts that colonise in the summer).

We are still working on the "composting/burning/burying/getting someone to take it away" issue, but this is not too urgent as we'll need to let it drain and dry off for some weeks or even months before doing anything.

I don't think black tarpaulin would be practicable given the area.

Thanks for the suggestions about filtration, which have given me quite a bit of food for thought. There is a pond supplies shop in the next town and I'll go there this week to have a look at what they have: the internet is brilliant but you can't beat seeing things for yourself.

Jim

 

[brokensword]

Hey Jim,
hope you get it sorted and keep us updated; I'd like to know how you solved or ended or maintained surrendered to the problem!

Good luck!

Michael

 

[Lakeside]

Michael and any other interested parties,

One week on, and one serious overflow later, herewith a progress report.

The temporary filter has proved almost completely ineffective and has been removed. The outer filter is still doing what it needs to do but will probably be replaced with a deeper (and straighter!!!!) version for the final filter. The problem of clogging of the inner filter has been drastically eased by easing it out from the wall around the outlet, so that rather than the debris collecting in the small area where the mesh has been sucked into the relatively small "letterbox" through which the water actually flows, it can now spread over a much larger area as the water finds alternative paths through the mesh. As Lisa said earlier, it does still clog eventually but now needs cleared only once or twice a week rather than daily. I'm tending towards the final solution being a metal box-type construction with a couple of removable filters (which can easily be pulled out for cleaning) running in channels down the side. We'll see in due course how that works out.

We didn't get any more weed cleared this weekend due to adverse weather conditions (we are all softies and it is unpleasant enough standing in freezing cold water without coping with sleet and snow as well) but will continue over the next few weekends as weather permits. The bulk of the weed is now out with only the following left to do:

• some trimming round the edges where the weed has grown into the wooden pilings
• skimming off the weed that has floated into the centre of the ponds,
• removal of the last weed in amongst the rushes, themselves growing in rather unpleasant muck.

We also have to decide what to do with all the extracted weed. The only options are as follows:

• Burn it on site (clearly this would depend on how well it would dry out, otherwise we would need huge amounts of accelerant),
• Bury it on site. We would need to hire a digger, find a suitable spot, and then work out how to dispose of the removed soil.
• Pile it in a corner somewhere and cover it with black plastic to let it rot down, as you yourself suggested earlier. A good suggestion, this, but no-one seems able to say how long it will take to rot completely! It could also be a bit of an eyesore if not carefully thought out.
• Have it taken away for commercial composting. The only suitable "in vessel compost facility" is about 30 miles away. If we could get the stuff there (a few of the residents have trailers which could be used if necessary) we would have to pay £96 per ton (including tax) for the privilege of having it disposed of. I suspect this would be vetoed by some of the residents who object to any expenditure, let alone large sums like this.

A final decision on disposal will have to wait until we have finished the extraction and had a vote on the preferred method.

Thanks for your continued support.

Jim

 

[Lisak1]

Great update! You guys are working hard to maintain this beautiful area - and so much cooperation from neighbors is good to see! I am surprised at how weak you Brits are... we Americans WAIT for the sleet to start falling before we get into our freezing cold ponds.

The only concern I would have about composting this off-site is that it appears to be a noxious weed. If it's not completely composted, the danger of it being spread to other areas would worry me. I don't take any compost from our local "free" pile for this very reason - not everyone is careful about keeping noxious weeds out of their compost. But it sounds like you have a great group of workers and you will all come to a logical, workable solution!

 

[Lakeside]

Thanks for your comments, Lisa. You must be hardier than us.

Just to reassure you, I asked our local recycling centre if they could recycle our weed with other garden waste (grass cuttings, pruning etc). Their response was " During the processing of such materials at our off taker, we could not guarantee the prevention of escape of such species as the processing is primarily out in the open. We would be concerned about processing such materials due to the proximity to freshwater and aquatic systems, therefore we would have to suggest that it cannot be processed through our sites. I would suggest that the best route to go down would be to see whether it can be accepted at an in vessel compost facility as opposed to a wind row facility which our off takers operate, or even possibly a local incineration company."

The only in-vessel composting within a reasonable distance is Envar, and at http://www.envar.co.uk/the-science/ you can see that the waste materials are composted in a completely closed environment. They are the people who quoted £96 per ton in the full knowledge of the nature of the weed.

Given that going down that route is likely to cost thousands, rather than hundreds, of pounds we are very unlikely to get agreement for this anyway so the point is probably moot.

Jim

 

[Lisak1]

Smart people you have there! I think it will break down rapidly though, so on site composting may be the best option. There are enzymes you can buy to add to compost to get it hotter faster, or you can find info on YouTube for homemade mixtures that will speed the process.

Good luck!

 

[brokensword]

It does sound like you have some dedicated people, though, Jim. I know we struggle here to get anyone to help when it comes to the cattails. And I've come to expect any 'year' of composting to take about a year to do just that, so I think you could expect decent decay in that time. I typically have 'one side for decomposing' and one side for 'useful compost', then alternate yearly which side gets new leaves, dead plantings, etc. Works really well, actually and a lot less work in the long run.

Yeah, the idea re filter is; easy to clean/dispose+replace, and a large enough area that maintenance is not constant. I think eventually, if you stop the weed almost entirely, you'll only do a couple of seasonal cleanings/replacings.

The trick, imo, now is to KEEP ON TOP of your problem so it never gets this way again. Here, we had a group when I was younger that kept at it and we never had a cattail problem. Then those folks got older, interest changed to 'close my eyes and I don't see it' until we eventually had almost 20' of pond near all shores covered in the beasts. Took about 3-4 years before we knocked them back to presentable. In the last 4 years, the problem came back and we're once again working to knock them back. You think your weed is tough, just don't ever get a pond full of cattails as they're almost sentient in their ability to take over.

And I feel your pain re disposal as ONCE, we could burn the dead cattails in the winter; the association here would actually have a 'burning party' right on the ice, in January/February. Now, our township won't let us and the only means is to cut and bundle and have local disposal pick up. But there's a ton of area covered still with the cattails and unless some secret army of volunteers steps up, I'm not leaping to the fray all by myself (actually, there'd be two of us but you get what I mean). A lot of manual labor and not a lot of man(uals), you know?

So, IF you can burn it, I'd opt for that as then you don't have to labor moving the weed into a compost area (my second choice, here). Shouldn't be hard to do a test burn and see how well it all goes, you know? I bet with enough dry weather (hmm, I dunno, do you Brits HAVE dry weather????), it should go okay.

Again, hope you have your problem under control and sounds like you have, so good for you. It is a great scenic place there, from the pics!


Michael