Bog/upflow wetlands filter experience

[brokensword]

Well, thought I'd relay my experience with a bog/upflow wetlands cleaning I just did. Took a fair amount of time and made almost every muscle I have ache. I'd like to show what I went through for others and/or get advice for any further 'cleanings'.

What I have is an approximately 4'x4'x4' bog that empties into a small/short stream which then empties into the pond (~2700 gal, ~100 sq. ft surface area). I didn't have this forum for reference when I started, so my bog was built after a 'pro's' version on the web. What I have is a bottom layer of 6" cobble that surrounds my 4" drain pipe, slit with holes. Next, there's about 2' of 2" cobble followed by 2' of pea gravel. The flex pvc coming from my submersible pump goes into the drain pipe which ends in a 12" diameter stack, which is supposed to be used as a clean out. There's the first of my questions;

if this stack is to be used, and by this I mean lowering a pump into the stack and 'backflushing' the bog, how does any debris/detritus work its way down through the entire rock layers and then into the stack if it's sealed? I think this 'stack' is more to be used if the drain pipe gets clogged. If not, I'd like a clue as to how to backflush and get the stone filter area clean instead of having to dig everything up and hand washing.

I figured I had to 'clean' my bog because over the past couple of years, I've been losing water from the bog. This was because I think it was clogged up, either by the plants or by the stones being filled by detritus. This caused the water to not seep upward but find any avenue up to escape the pump's pressure. It began to pour along the sides of the bog and through the stack/clean out. When I put a 'filter' piece inside the stack, it didn't do much besides make the water act more aggressively against the bog's sides.

Soooo, to alleviate the fact I had to slow the flow to the bog (and lessen the filtering power), I decided to clean everything out. When I dug out the stone, there was the expected detritus/debris, especially beneath the foam filter in the stack, as well as a large glob at the drain pipe's end, but overall, I didn't think it was that 'caked'.

Now, I'd like to see if I can do this better in the future and would welcome ideas. I know some might say I should go all pea gravel and if so, please advise it, even if I won't change anything until the next 'cleaning'. I'd still like to know a 'better way' if you have it. Btw, I have no way to add a drain; just the clean out stack. I don't really think 'backflushing' is going to work as I want it to but maybe someone can show me the way. I'd certainly welcome it for the next time. I'm at least of the thought that I'll only dig out the top 2' of pea gravel next time and wash/clean that. Unless someone can tell me why that wouldn't be a good idea and I need to completely take it down to the bottom again.

And for anyone wondering, there was no obnoxious smell at all; just clean pond water, so no anaerobic issues at all, despite it being shut down for the winter.

I think some of my 'errors' were; putting the sub pump too low in the pond initially. I have had it about mid-height for the past two years. I don't have any 'pre-filter', all I have now is a window screen 'bag' around it to keep out anything large. Is this enough?

Another thing I did wrong was to put 'large' plants in my bog; last year, I had a 7' black taro, and also too many yellow flag irises. I'm planning on putting in lower growing plants like pennywort or some dwarf papyrus.

A last question would be; last year to help alleviate the water loss, I lessened the flow to the bog so it merely trickled. Is there a better flow rate? That is, if faster, does it clean better? Does it act as a better biofilter if I blast the water through or trickle it?


Anyway, I never thought I'd have to 'clean' this bog but found out otherwise. If my methodology is wrong, I'd like to know. I think my changes will help and the bog lasted 3 good years before I began having issues in year 4 then 5.

Thanks for listening and any help/discussion.

Michael

 

[MitchM]

It sounds to me like it may just be a case of overgrown roots.
Can you remove the majority of the existing roots and see if you have improved water flow?
Perhaps you could use a plumbers snake down the stack to clean out the plumbing.
For water flow, I prefer a slow rate as opposed to a faster one.
I think removing the rock should be a last resort.

 

[addy1]

After a few years of running I had to raise the sides of my bog pea gravel filter. The plants were causing the water to flow out slower, ie. raise higher.
I did raise the back down slope side of the liner by about a inch to two. Also during the summer I go into the bog and make a track down the middle to help the water flow out. Like a mini river. I run around 6000 gph through it, but with the size of it, each part of the bog gets some of that flow. It makes a nice water fall into the pond, also comes over the ponds bog wall here and there.

I do yank plants off and on during the summer it does get really over grown, sure takes good care of the ponds.

Like yours mine has never stunk.

 

[brokensword]

It sounds to me like it may just be a case of overgrown roots.
Can you remove the majority of the existing roots and see if you have improved water flow?
Perhaps you could use a plumbers snake down the stack to clean out the plumbing.
For water flow, I prefer a slow rate as opposed to a faster one.
I think removing the rock should be a last resort.

I hope you're right, Mitch. When I cut everything down last autumn, I did do some testing and it flowed better as well as I didn't lose any water. That means I have to probably be careful just how many/much plants I have in the bog. Just wasn't expecting it to get as clogged as fast since I can usually see much of the actual bog/pea gravel surface. I'm sure the taro didn't help. Re the snake; I think just putting the pump down the stack will clear it in the future but I was hoping there was a sure fire way of backflushing so I can get ALL the rock layers clean, if I wanted to, without digging. Since yesterday, I had to cut the flow back again; must have a leak in the river portion as I'm sure the bog now is okay. But I'll keep the flow slower in general, now.

Yeah, it should be the last resort, hence why I let the problems go for the past two years...heh.

Michael

 

[brokensword]

After a few years of running I had to raise the sides of my bog pea gravel filter. The plants were causing the water to flow out slower, ie. raise higher.
I did raise the back down slope side of the liner by about a inch to two. Also during the summer I go into the bog and make a track down the middle to help the water flow out. Like a mini river. I run around 6000 gph through it, but with the size of it, each part of the bog gets some of that flow. It makes a nice water fall into the pond, also comes over the ponds bog wall here and there.

I do yank plants off and on during the summer it does get really over grown, sure takes good care of the ponds.

Like yours mine has never stunk.

Yeah, I had to 'adjust' the liner of the bog to compensate for the increased water level. I had hoped that was all I needed but apparently, I have too little liner to adjust and it's finding a way out anyhow. I checked it just now and I've lost water in the pond so there must be a leak––I'm betting it's now in the stream portion and have cut the bog flow to see. I thought about cutting a path in the bog for the water but it seems then you're compromising the bog, aren't you? That is, if there's an easy out for the water, seems any other parts will not get forced flow, only the area nearest the 'path', yes? I could try that though and see how it works...after I fix any stream issues.

Thanks, addy!


Michael

 

[Meyer Jordan]

The idea of incorporating 'bogs' into the filtration process in a pond was derived from the enormous constructed wetlands that are used for the cleansing of municipal and industrial waste water. Somehow over time in the adoption process several important aspects of constructed wetlands have
been omitted and/or neglected.
First, although a 'bog' may be used for nitrification, the original (and still) main purpose of constructed wetlands is to 'polish' (removal of Nitrate, heavy metals, and other organic and inorganicpollutants) the water through the use of phytofiltration.
Because of the immense surface area available on the gravel used in construction, nitrification will also occur.
In either usage the bog should be treated as at least secondary filtration. Mechanical filtration should definitely precede a 'bog' much as mechanical filtration should precede the use of any biofilter. Efficient removal of suspended solids beforehand is paramount for ensuring the efficiency of any biofiltration.
This mechanical filtration can be in the form of a skimmer, RDF (Rotary Drum Filter), settling tank/chamber (@addy1 's multiple smaller ponds are an example) or other means.
Without this pre-filtering (Mechanical), a 'bog' will clog. Some may take longer to do so than others.
Overgrowth of 'bog' plants can also cause issues as the roots grow and trap minute suspended particles resulting in clogging and water channeling.
A 'bog' should not be over-planted or allowed to become overgrown. Thinning should be done on an as needed basis, but no less than once per year.
If a 'bog' has become clogged from accumulation of organic particulate then two options are available: backflushing or deconstruction. The former is usually the first choice. Since a 'bog' operates utilizing an upflow of water then backflushing should be accomplished with downflow in order to dislodge any particulates causing the clogging.

 

[brokensword]

Meyer;

I sort of suspected as much and am wondering which is least maintenance; sifting/backflushing the pea gravel or ministering to a separate mechanical filter (I'm assuming you mean something like a Skippy, yes?). As it is, it took 3 years before I noticed any issue and if I'd have backflushed or cleaned then, probably would have avoided any issues. Knowing now that I can't put my sub pump near the bottom, and keeping large plants/too many plants from taking over the bog, I figure I should at least get another 3 years before I have to do anything. Then comes the question;

I understand that backflushing will dislodge particulates, but how do I get them out of the bottom of the bog? There is only the drain pipe slits to allow anything to make its way into the stack for the pump's removal. Does the natural sucking power of the pump in the stack pull the matter out? That's the answer I'm hoping you're going to give...if not, any 'best of' ideas? I figure I probably didn't have to dig all the way down and could have just cleaned the top layer of pea gravel, which while laborious, is the easiest of the whole process, imo.

Second question would be; what type of filter would you advise for the mechanical filtering? I don't need a skimmer as my pond is enclosed and I only get what falls from the surrounding plantings, which doesn't seem like that much. What I have is a sub pump on one end, the tubing works from that, goes overland and rises to a 3' waterfall where it tees off; one to the waterfall, the other to the bog, which is a descent and then finally into the bottom of the bog. Being enclosed, any mech filter is going to be dicey to employ/place as I'm using most of the surrounding area for plantings. I'd have to have some idea and work alternates if the size is too large, etc. But I need a starting point. It might be possible to use a mech filter BEHIND the waterfall, but size will matter. That is, size of any filtering material. And of course, it's not easy to get to but well, I suppose I have that coming...

Any further ideas would be welcome.

Michael

 

[addy1]

I thought about cutting a path in the bog for the water but it seems then you're compromising the bog, aren't you? That is, if there's an easy out for the water, seems any other parts will not get forced flow, only the area nearest the 'path', yes? I could try that though and see how it works...after I fix any stream issues.

The channel was dug in more before I raised the liner. Even with the channel the water flowed through plants and plant roots before it entered the channel and water-falled back into the pond. So some filtration was going on.

 

[Lisak1]

I know some might say I should go all pea gravel and if so, please advise it

I personally would never recommend all pea gravel. We have no pea gravel in our bog at all. I find it clogs too easily and is a pain to clean out once it does.

As for your cleaning question - I wonder if you used a power washer to push the debris downward and then the pump was sucking upward, if that would accelerate clean out? We have a stack in our bog, too and that's always been my plan if we ever felt the need to clean it out. I guess a lot would depend on how much debris you could push back through the holes in your plumbing. Ours is a centipede, which has large slits so I am pretty confident it would work in our set up.

Although I am equally hopeful that it's never going to be necessary... we'll see!

 

[addy1]

Mine is nothing but pea gravel and plants.

I decided once years ago to power wash the gravel, I opened the bottom bog drain, used a lot of water and time and got barely any thing out. But then again there was not much in the gravel. I have not tried again since.

 

[Lisak1]

Mine is nothing but pea gravel and plants.

And there you go! Always more than one way to go!

I think one of the mistakes we made in our "down flow bog" was using two types of gravel - pea gravel and construction gravel. The two mixed eventually and locked together - just like they are supposed to! I don't know why I thought the layers would stay separate... dumb. Gravity - and lots of raking - forced the pea gravel down into the larger gravel... nothing but problems. Had to dig the whole thing out (thank you strong sons who love their mom enough to spend a hot Saturday digging out and hauling gravel!) and replace it with new stone.

 

[brokensword]

I personally would never recommend all pea gravel. We have no pea gravel in our bog at all. I find it clogs too easily and is a pain to clean out once it does.

As for your cleaning question - I wonder if you used a power washer to push the debris downward and then the pump was sucking upward, if that would accelerate clean out? We have a stack in our bog, too and that's always been my plan if we ever felt the need to clean it out. I guess a lot would depend on how much debris you could push back through the holes in your plumbing. Ours is a centipede, which has large slits so I am pretty confident it would work in our set up.

Although I am equally hopeful that it's never going to be necessary... we'll see!

LisaK1;
If you use all 'rounded' types of stone (the concrete gravel is different) then locking shouldn't occur. That was my experience, though it was still a pita because I couldn't use the shovel on the 2 inchers or the bottom 6 inchers. Lots of hand abuse in fairly cold water (I have a well, deep too). My question though is, if you power wash backwards (which sounds like a good idea) and drive everything down, I'm wondering how effective the pump in the stack can be. Do you think the 1/4" slits would be good enough? It's the only way anything is going to get to the stack pump...

I was hoping someone here might have actually gone through this, you know? I'd like to hear if there are any tips to use for next time!

Michael

 

[brokensword]

Mine is nothing but pea gravel and plants.

I decided once years ago to power wash the gravel, I opened the bottom bog drain, used a lot of water and time and got barely any thing out. But then again there was not much in the gravel. I have not tried again since.

I have a feeling addy that you're really benefitting from having such a large area. And Meyer mentioned you have your feed from the pond going through a series of smaller tubs? I imagine this helps settle some of the detritus? I'm contemplating how I might put some sort of mechanical filter ahead of the bog but it might just be I should put more effort into being able to backflush easier, for future issues. Doing something every year might also help, as opposed to waiting until it gets bad.

Michael

 

[brokensword]

And there you go! Always more than one way to go!

I think one of the mistakes we made in our "down flow bog" was using two types of gravel - pea gravel and construction gravel. The two mixed eventually and locked together - just like they are supposed to! I don't know why I thought the layers would stay separate... dumb. Gravity - and lots of raking - forced the pea gravel down into the larger gravel... nothing but problems. Had to dig the whole thing out (thank you strong sons who love their mom enough to spend a hot Saturday digging out and hauling gravel!) and replace it with new stone.

btw, LisaK1, my layers stayed pretty well intact; there was some pea gravel down low but not much!

 

[Meyer Jordan]

I'm contemplating how I might put some sort of mechanical filter ahead of the bog but it might just be I should put more effort into being able to backflush easier, for future issues. Doing something every year might also help, as opposed to waiting until it gets bad.

I would recommend both if you want the 'bog' to work at peak efficiency.