My future wetland

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Ralph
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My future wetland

Post by Ralph » Fri Jan 02, 2004 10:40 am

Happy New Year.

New year, old house. The iron pipe which drains the sinks/shower to the septic tank is pretty well shot. Certain fixtures in my house have, a-hem, "modified" greywater plumbing. So, given the antiquity of my house and the ample surroundings, I'd like to construct a wetland greywater treatment area.

I have a spot picked out which is about 250 from the house and approx. 10 feet down gradient. This spot is in a natural swale, just uphill from a farm pond. It is currently grassed. The soil is extremely thin because the natural soil was removed for construction of the pond dam. The pond is about 5,000 square feet area at average depth of 4 feet. The area for the greywater treatment area is about half that size.

My main concern is that the constructed wetland would be too wet in the rainy season. This area collects runoff from approx. 15 acres and is seldom dry. The greywater input would not be large - perhaps 150 gpd on a big day. So my question is:
What is a good way to deal with huge amounts of runoff in a constructed wetland? Maybe I need to avoid the main channel and construct along the sides where there would not be so much runoff? French drain under the wetland liner? Anybody have experience with this?

Thanks,
Ralph
West Wind Farms
Organic & Grassfed Meats & Poultry
http://www.grassorganic.com

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Bob
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Post by Bob » Fri Jan 02, 2004 11:57 am

Hi Ralph,

Sounds like an interesting set of problems/challenges.

My first thought is how small your graywater volume is compared to the amount of rainfall:

annual graywater = 100/7.48 gal/cu ft * 365 ~ 5,000 cu ft/year

rainwater = 60"/12 * 15 acres * 43,560 sf/acre * say 33% (amount not evaporated nor absorbed) ~ 1,000,000 cu ft/year

Is your concern that the graywater solids would accumulate in the wetland during the dry season, to be washed out into the pond whenever there are heavy rains?

What if you treat the graywater in a much smaller constructed wetland (e.g. an aesthetic "water garden") near the house, and drain the treated effluent to the existing natural wetland 250' away, where it combines with the runoff?

Just thinking out loud...

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Ralph
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Post by Ralph » Fri Jan 02, 2004 12:49 pm

In my plan, I would size the wetland optimally for the high end of influent expected. If I base the design on this domestic production volume, it will not be adequate for the potential (and frequent) runoff from the fields. I don't want to flush "unfinished" material into the pond because the pond is my primary source for livestock water (via irrigation). So it seems appropriate to avoid the area of highest runoff.

The reason for siting the wetland near the pond is that the areas near the house are getting cluttered with outbuildings, greenhouses, perennial bedding plant areas, doghouses, traffic, underground utilities, etc. (Man, I'm feeling cramped. Its a good reason to stay out in the fields.) I could potentially locate the wetland behind a shed about 100 feet away from the house, but it depends on how small I can make the wetland. I'd only have about 500 s.f. to deal with there and it may present an access problem to a couple of buildings.

Sounds like a good opportunity for on-site consulting. Or a good reason to build a new house!

-Ralph
West Wind Farms
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http://www.grassorganic.com

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Bob
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Post by Bob » Fri Jan 02, 2004 3:51 pm

Ah, so the primary goal of the wetland is to polish the runoff from the fields? (given that that volume is about 200X the volume of the household graywater?)

Re a small dedicated household graywater treatment system, what if it were only about 100-120 sf and beautiful, something that you'd be proud to show off to visitors as a centerpiece, rather than hide behind a shed? What if it looked like this?

Image

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Ralph
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Post by Ralph » Mon Jan 05, 2004 8:24 am

Well, no, the primary goal of the wetland is domestic greywater treatment, not treating field runoff. The greywater will need to be suitable for watering livestock and other "watery" uses. A 100 s.f. treatment area would be great. As far as placement, it needs to be out of the way so I don't trip over it while running around the farm at night without my flashlight (I do a lot of that - running around, not tripping).

An aesthetically pleasing treatment arrangement would suit Kimberlie very well. She already has a spot dug out for a water garden smack in the middle of the front yard. And I've already learned not to fall into the hole at night. Additionally, the yard doesn't get any field runoff so that problem is avoided. I just need to figure out where to discharge the effluent. I'd rather not need to pump it.

Good ideas, Bob. The only drawback to "centerpieces" I can see is that they need to be kept pretty, which will require some extra time above normal maintenance. Time is in short supply around here but maybe we could make it work.

-Ralph
West Wind Farms
Organic & Grassfed Meats & Poultry
http://www.grassorganic.com

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Bob
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Post by Bob » Tue Jan 06, 2004 3:47 pm

Here is what I am doing with graywater in our house, Ralph. As described, the system treats about 100-150 gpd, yielding water suitable for reuse--a fully closed system--with very little maintenance required. Graywater first...
  • ...drains by gravity to a primary settling/aeration tank (an earlier, simpler version of this), then is pumped to
  • a "wetland" (consisting of a pea-gravel filled trench planted with selected bog plants, surrounding a pond), from which it overflows to
  • the pond (about 7-8' diameter x 24-30" deep, i.e. ~ 5 day HRT at 150 gpd), from which it overflows to
  • a subsurface drainfield (perforated drainpipe buried in the soil of the indoor greenhouse). From here it percolates down through layers of soil, sand and gravel, until it hits the sloping bottom (visualize an indoor swimming pool with sloping concrete bottom, backfilled with sand/gravel/geofabric/topsoil), to collect at the deep end, from where it flows through a UV sterilizer into a sump, where a pump with float switch pumps it into
  • a 5,000 gallon cistern, from which it is
  • further filtered (depending on end use), and reused.
In describing this, I don't mean to suggest that you install a similar system, but I can tell you that the first two components alone (the primary settling/aeration tank and the pond/trench) is able to reliably remove >99% of BOD and TSS from 100-150 gpd, with very little attention and/or maintenance required. I wouldn't want to drink the water in this pond, but I would bet that it is probably pretty similar quality to what you have in your livestock pond. (Fish in the pond act as water quality monitors (like canaries in coal mines).

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Ralph
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Post by Ralph » Wed Jan 07, 2004 7:25 am

Bob-

Thats a nice summary of your water recycling system. Makes it easy to understand. Laurel has tried to describe it to us, and I read your article describing it. For some reason, it reminds me of Frank Herbert's book Dune.

The plants used by you to do water remediation in your greywater treatment process are "bog plants" in your indoor greenhouse. The whole process takes place inside the "heated envelope". Certainly plants need to be actively growing in order to do any water-cleansing. Well, it was 7 degrees F. outside my house this morning. Water doesn't flow very quickly at that temperature and my bog plants look a bit weepy. It seems to me that greywater treatment via an artificial marsh is only suited to subtropical or greenhouse environs. Winter weather conditions in most temperate regions would seem to present too many problems to make it work there.

Thanks,
Ralph
West Wind Farms
Organic & Grassfed Meats & Poultry
http://www.grassorganic.com

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Bob
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Post by Bob » Wed Jan 07, 2004 4:21 pm

Heh. Yeah Dune was a great read. (and no, we don't walk around in stillsuits, nor do we expect to be rendered down upon our demise... :-) )

Good point about winter temps. I guess I was just thinking of Tennessee as a hot place. (Compared to here, almost every place seems like that)

Having said that, though, I wouldn't arbitrarily rule out the idea, but just modify the thinking somewhat. In fact, a variety of plants do continue to transport oxygen to the root zone, and uptake nutrients (and, e.g. heavy metals) throughout the winter -- while apparently dead (e.g. dry brown stalks sticking up through the snow). I'm away from my office right now, so don't have access to the cites, but here's one reference that has that info in it.

If you had a 2' deep pond, how thick might the ice get on it during a worst-case winter cold snap? If it were fed with 100 gal/day of 60-70degF water do you think that would keep it from freezing? Does moving water (your creek) freeze?

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Ralph
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Post by Ralph » Wed Jan 07, 2004 9:13 pm

Bob-

Do you have a copy of Ecological Engineering for Wastewater Treatment? It only costs $110, so it is within the grasp of the tax category"continuing education".
If you had a 2' deep pond, how thick might the ice get on it during a worst-case winter cold snap? If it were fed with 100 gal/day of 60-70degF water do you think that would keep it from freezing? Does moving water (your creek) freeze?
Ice can get 2-3 inch thick on ponds and such around here, but it does't stay there for more than a week or two. More typical is a 1/2-3/4 inch ice layer for a couple of days. The creek will form ice in the pools and along the edges of the rapids, but the rapids never freeze. Our winters are about like southern Ohio - we're a cool spot in Tennessee.

If an artificial wetland will work outdoors in our climate year round, I'll certainly make an attempt to construct one.

Thanks,
Ralph
West Wind Farms
Organic & Grassfed Meats & Poultry
http://www.grassorganic.com

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nathan_lamothe
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Post by nathan_lamothe » Thu Jan 08, 2004 11:15 pm

Idle speculation I suppose, but we measure the thickness of ice around here in feet, and drive trucks on it...

but a fairly small aeration unit will keep the water from freezing in the dugouts... at least where the bubbles surface. I would suspect that if you are only dealing with a couple of inches of ice for a week or two you won't have to worry about freezing if your effluent is warm, steady flowing, and hey... build in the rapids, that'd look pretty.

Hi Bob! good to see some action on the forums here. Thanks again for the great site!

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Post by Bob » Thu Jan 08, 2004 11:47 pm

Hey Nathan! Nice to see (read) you. How's things?

Ralph, yes, I have a copy of Ecological Engineering for Wastewater Treatment. (In fact, a paper of mine is in it.) I'll dig it out and find the relevant info.

Work kind of bunched up on me, so it might take me a few days to get back to it.

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