sketch of my planned grey water treatment system

Hello Permies !

I'd like to share my sketch of a grey water system, hoping to get as many comments & critique from you as possible.

I will assume for now that my pictures are self-explanatory, and so I won't add any commentary here.

Background: my project is in a temperate climate zone, with very cold winters. Hence, most of the solutions that Art Ludwig proposes in his books are not feasible here. Soil is heavy clay (= low percolation rate expected).

Objective of grey water system: (a) treat grey water separately from black water, to avoid overload of septic system; (b) use the treated grey water to feed a pond

Looking forward to your feedback !
L_

What are you going to do with the straw after it has captured the grease? How often will you be changing the straw out? Where is the straw going to come from?

Also, how often is the water going to be oxygenated? And how is it going to be oxygenated?

One to oxygenate the water is to add a flowform or two or many:



In the video, you can see how the water splashes around a lot. You can also see the bubbles getting trapped in the water, too!

I like that you're drain pipe, drains to sunlight. This makes future maintenance much simpler, should it ever need to be rooted out.

Dave Burton wrote:What are you going to do with the straw after it has captured the grease? How often will you be changing the straw out? Where is the straw going to come from?

Also, how often is the water going to be oxygenated? And how is it going to be oxygenated?

One to oxygenate the water is to add a flowform or two or many:

In the video, you can see how the water splashes around a lot. You can also see the bubbles getting trapped in the water, too!

Dave:

The straw or other mulch - e.g., alfalfa hay, of which I'm producing plenty - will be composted. I don't know how often I will need to change the mulch, at this point I assume it will be once or twice a month. If the mulch will be straw from bales, I will need to buy it; baled straw is easier to store, handle, and apportion into the grease trap; and straw is excellent compost material. However, as I said, I can also use my own stuff, such as alfalfa hay.

Re. oxygenation: I wonder if this is really necessary. In an earlier version of my plan I had a settling tank and an aeration tank (both underground), in place of the grease trap & filter - something similar to the system illustrated in the video below.

https://www.youtube.com/watch?v=r7efH9DVlws

However, as this option would have required 2 watertight tanks placed below the frost line (= more room taken up & higher cost), I decided to eliminate the 2 tanks and put in the filter instead. I'm counting on the water getting oxygenated as it flows from one basin of the wetland into the next, and then into the pond.

I'm not sure if Flowforms would be justified in my case as the flow of water would be an intermittent trickle (our water consumption is quite modest), and for 4-5 months out of 12 probably more of a hindrance than a help (I can't try to imagine where the grey water will go when the Flowforms are covered in snow and ice).

Levente, I've actually got this setup and it works great. In the containers I put half bark chips and half large gravel as the growing medium for reeds. I wanted more organic matter and some acidity from the bark chips because most of the grey water has soap in it, which is alkaline. So far the reeds are doing really well. I transplanted young ones with large roots and they never even wilted. I collect the "finished" water in a container with a valve that goes down to a greenhouse where it flows through more bark chips.

I read that the trick is not to let the water rise above the rocks/bark chips, so it doesn't smell, so the outlet holes are placed accordingly. If I stir the water around it has an odor, but not the disgusting odor of sitting grey water with no plants involved. Even on a hot day there is no odor coming off the containers.

No animals or rodents are chewing on the reeds, which they don't on my pond anyway, but I don't trust them! Ha!

The only thing I might add is that you might need more containers depending on how many people are using water. I think there should be three steps (containers) that the water goes through for real cleaning, so you might need more room before the pond for any expansion of number of containers. Or maybe you could zigzag the containers if you wanted to add more and run out of space.

Hi Levente,

I am looking to build a similar system in a different part of Transylvania, so with similar climate condition just maybe not as cold as your place in the winter.

My questions are not necessary for your system but just want to check some points to fit my design:
- The grace trap filter is placed below the freezing line? What would happen if the top part of this filter freezes … will the water still flow through the frozen straws or will overflow.
- How often you expect the straws will need to be changed (for your typical water consumption)? I would expect that needs to be changed less often in the winter if it’s close to freezing point since the decomposition will be slowed down.
- Do you see any problems on placing the grease trap on the end of the pipe (near the wetland)?
- On the wetland did you study the possibility of placing some evergreens suitable for cold climate instead of simple reed beds, does this make sense? I remember meeting some species of rhododendron growing in the alpine bogs with evergreen leaves. Searching on the net I found some possible candidates for this: Labrador tea (Rhododendron groenlandicum), Vaccinium macrocarpon (large cranberry)

Thanks,
George

George Sandu wrote:Hi Levente,

I am looking to build a similar system in a different part of Transylvania, so with similar climate condition just maybe not as cold as your place in the winter.

My questions are not necessary for your system but just want to check some points to fit my design:
- The grace trap filter is placed below the freezing line? What would happen if the top part of this filter freezes … will the water still flow through the frozen straws or will overflow.
- How often you expect the straws will need to be changed (for your typical water consumption)? I would expect that needs to be changed less often in the winter if it’s close to freezing point since the decomposition will be slowed down.
- Do you see any problems on placing the grease trap on the end of the pipe (near the wetland)?
- On the wetland did you study the possibility of placing some evergreens suitable for cold climate instead of simple reed beds, does this make sense? I remember meeting some species of rhododendron growing in the alpine bogs with evergreen leaves. Searching on the net I found some possible candidates for this: Labrador tea (Rhododendron groenlandicum), Vaccinium macrocarpon (large cranberry)

Thanks,
George

Hello George,

Probably the safest would be to place the mulch (straw or other) below the frost line. But in my zone (Harghita county) the frost line would be around 1 m, and if I placed the grease barrier so low, I would be losing a lot of head.

So, I'm hoping to get away with much less than 1m, say for instance 50cm. My theory is that (a) in a covered pit, at a depth of 50 cm, the wet mulch will still be somewhat protected from hard frost, most of the time; (b) if the wet mulch does freeze at 50cm depth, the mass of frozen mulch will still be porous enough to let the water through; (c) household water / grey water is comparatively warm and should thaw the frozen mulch temporarily; (d) underneath the 20-30cm thick mulch (grease trap), I plan to have a rough gravel filter of about 30cm in depth; so the gravel will start at a depth of 70-80cm, which is almost at the frost line; thus, I expect the gravel to act as thermal mass that will help keep the mulch frost free most of the time.

In conclusion, the grey water that has passed through the grease trap & gravel filter will collect at a depth of about 1m, at which point it should be frost-free; unfortunately this is not ideal, because by the time I reach 1m in depth, I'm left with very little head for feeding into the 'wetland'.

I would check the grease trap every couple of weeks, and change the straw / mulch as often as is necessary - e.g., when the mulch is starting to get too 'dirty'. Probably once a month? Once every 2 weeks? I don't know.

Re. placing the grease trap at the end of the pipe: it may work, but I think it will depend on how much head you have left between the grease trap and the wetland.

I have not thought about the choice of plants for the wetland. I think that that the science is not certain regarding the extent of the filtering role of plants, even in the warm season (it seems that the main filtering action is through the passage of water over soil and through the soil microorganisms). The plants that you propose may be okay, but I have learned that availability of the plants is a key consideration. They are no use to me if I cannot source them from any of the nurseries nearby...

I hope this helps. Let us know how your design progresses.

L_

thank you! You have provided an answer to my grey water concerns

Cristo-

Any chance of posting pics of your setup?

Thanks

I agree, that most of your household water (even in winter) is at least room temp and so I'd wonder if it wasn't possible to put some insulation around the grease trap???

We are in Ohio, so winters are fairly cold, and we did a very different idea for our constructed wetlands... about 4' deep Stone and gravel, keeping the water level about a foot or more below the top surface, on the premise that it was friendly microbes that cleaned the water, not plants... So keeping the water and microbes sheltered was our concept...We also ran the greywater pipe from the house through the processing stone (on its way to the infiltrator manifold) so the warmth in the pipe would supply the processing area with warmth and our winter OEPA testing showed that the temperature at the finished end was still in the mid-lower 40s in the winter snow time....

We didn't worry about a grease trap since we were doing thermophillic composting toilets as well as offal and grease cleanups with paper..
Testing (2 yrs in service) showed the output was very well cleaned so microbes are good workers when treated well..... Our sizing was done with the equations developed by Vymazal (Czech), Darcy et al, from the 1988 EPA manual...... ttyl, best as always

Levente,

To assist with the freezing issue, what if you created an "overflow" out of the grease trap. I would imagine this would look something like a very coarse and loose french drain that initiated a couple inches below the top of the trap. You could run it out as a french drain to a tree or something on the hillside to put it to good use. That way in case you ever had an influx of greywater (summer or winter) you don't get a big mud pit around your grease trap and the water will go to something beneficial.

Also building a rock sun trap around the trap above the surface using some good heat trapping stone would help in tempering the freezing issue.

Love your design!

This is helpful for what we are planing here in the near future. We are turning our far flung annual gardens to perennials and moving the annuals closer to the house where the gray water will help to irrigate. Thanks for the drawing

I've got some update info.

--The most helpful part of the setup is a C of a V of hardware cloth at the exit end keeping the gravel and bark chips out of the exit hole. The C is filled with gravel on the inside, and is held in place by the gravel and bark chips on the outside of it.

-- The reeds die back in winter, although the fat roots are alive, and I am hoping they are still affecting the water in good ways. But it turns out it only took the pack rats a month to find and chew the reeds off for nesting material, so a chicken wire surround has to be in place.

--I've added two other types of aggressive pond plants into the tubs so there will be active greenery in the winter, and the critters will hopefully leave them alone, or the plants can outgrow the chewing. So far this is working. Sorry, I don't know what plants they are. One is a fern-looking water plant, and the other is a type of vine with roundish leaves that grows at the edges of the pond in the muck where it's shallow. Both of these transplanted without wilting and took off in what I assume is pretty alkaline water.

-- I'm finding that the critters move just about everything involving the pipes and gravel and plants, so all pipes and supports have to be fastened down.

-- The water in the first container, if you stir it up, doesn't smell so great, and on a hot day there might be some scent of stagnant water. But these containers are 40 feet downhill from the house, and sitting out on the deck I've never smelled it. The driveway is about halfway to the containers, and that's where I've noticed the scent on occasion, but only when it's hot. The fourth container water (the final one before releasing) does not have any disagreeable odor about it.

-- I keep the water level slightly below the gravel/bark chips are, so the mosquitoes can't have standing water, but the chicken wire has to be in place because critters will happily walk across the gravel and bark chips to get what they want.

-- I am hoping little tree frogs will move in, and make their way through the 1" chicken wire holes. They might feel safer with the wire around the plants.

-- The fourth container is just water, I let it fill up so when I release it to go downhill into the greenhouse it will spread the whole length of the pipe that is over the bark chip trench, rather than just trickle down in small amounts that are coming out of the shower or kitchen sink water and only dribble into the same place. I have put a couple of logs in this container so no rabbits or birds or pack rats will get into the deep water and die. But I have to let it out often as there are mosquitoes. A lid might work, but I like to keep an eye on it.

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Luke, I'll see about some photos, but it's very basic. The bark chip trench in the greenhouse doesn't show anymore, but there is a good picture of a bark chip trench with PVC pipe at the Solviva site.