grey water system design for cold climate

Hello Permies !

I have been planning the grey water system for my semi-rural property in Transylvania, Romania, and two somewhat different solutions offer themselves - I will need to decide which route to take. I thought I could share these and hear your opinions with regard to pros and cons, and perhaps possible tweaks - and even alternatives?

Background: the property is in zone 5, continental climate (cold winters - temperatures of minus 20 degrees Centigrade are not uncommon, hence in winter, water running on the surface quickly turns into ice, and some elements like constructed wetlands have limited efficiency). Soil is heavy clay, with poor percolation.

The objective is to re-use the household grey water for garden irrigation, and/or turn it into water that is suitable for a small wildlife pond

I have read Art Ludwig's book on grey water, found it very useful and interesting, but the solutions he describes are not wholly suitable for my climate or my situation - although the general principles and some of his ideas were helpful in getting me started on my design.

What resonated with me was the TraiSelect system proposed by Jozsef Orszagh - see http://eautarcie.org/en/index.html or on YouTube

The two solutions that I'm weighing at the moment are:

(a) an (adapted?) Traiselect, consisting of a grey water tank ("batch reactor" - basically a septic tank where the grey water is pre-treated through anaerobic purification ); an aeration tank; a planted trench filter; and a constructed wetland or pond.

(b) a system consisting of an underground concrete chamber filled with mulch (straw, wood chip etc.), possibly also charcoal, which would act as grease trap and initial filter; and a constructed wetland possibly two (water "cascading" from the one into the next); and a pond or tank where filtered water collects. Between the concrete chamber and the constructed wetland I might include a winding gravel swale to provide extra filtration and aeration. A similar system is described here http://eautarcie.org/en/temoignage-andalousie.html

Note that system (a) expressly excludes the use of a grease trap (the grease film that forms on the surface inside the "reactor" has an important role); and that it requires a pond aerator which (I assume) is an air pump not very different from the ones used in an aquarium. So technologically slightly more complex than system (b). It seems to me that the aerator is a nice-to-have rather than an essential element, and could be dispensed with.

I am slightly more inclined towards (b) because of its seeming simplicity, and because (a) involves the use of the "reactor" which (pardon my ignorance) I have not seen used like this before - besides, the reactor has grey water sitting in it for a relatively long time, which in Art Ludwig's book is a mistake (although I do suspect that this is a different concept from grey water just collecting in a container).

The downside of system (b) is probably the long pathway that the water has to cover between the initial filtering and the final destination, and hence the larger loss through evaporation.

I would be extremely grateful for any thoughts / ideas / suggestions !

Levant

Thus system can handle black water even:
https://permies.com/forums/posts/preList/31936/248689. http
And check out Abe's system here:
https://permies.com/forums/f-77/composting-toilet

I have been looking at Sand Filtration for our grey water-


Then, once clean, it be used for nearly everything except for drinking. If you heated the water it could do dishes, laundry or, flushing toilets, though most people don't make enough grey water to use for the water wasting toilets so maybe get a SeaLand toilet with a compost toilet system?

I think the Sand Filtering tanks are ideal, and to add to the efficiency I would add some additional filters-
First, the top filter should be able to be taken out and burned (?) as this is the catch-all filter.
And, on the bottom I would add a charcoal filter.

That said, a large sand filter seems to be the best solution to northern climate greywater systems. The filtered and cleaned water can then be used for watering plants or garden/yard.

Hi guys,

Thanks for your replies / posts regarding sand filtering and other solutions.

I have some doubts about the efficiency and even suitability of sand filtering for a grey water system

I do see S Andow's point about a 'catch-all filter' (I called it grease trap) - this would catch some of the grease and the rough particles that float in the grey water. For this you can use mulch of some type, which you can remove periodically and compost (rather than burn).

HOWEVER, I don't think that grey water that exits such a grease trap would be suitable for sand filtering. It would still contain a fairly high amount of grease and solids that would quickly clog up your sand filter and render it useless within a short time. Thus you will need to wash (or replace) your sand filter several times a year (=not practical).

More importantly, I believe that trying to pass grey water through a sand filter is an overkill. Your goal is not to obtain pure water that's suitable for drinking (as in the video that Sherry Jansen posted), but water that is suitable for, say, (a) a wildlife pond; or (b) for storage, e.g., in a cistern, so that you can use it for watering crops when needed, rather than when produced.

If you had a system that took your grey water directly to the veg bed or tree that you wanted to water, you might not even need to filter it at all, except if you were concerned about pipes clogging up with solids. I'd like to go beyond that, i.e., I'd like to be able to use the grey water only when and where needed - hence I would need to store it, hence it would have to be 'filtered' or treated to some extent, before it goes into the storage tank.

Any further thoughts are still welcome !

Levente

Hi Levente, have you considered a constructed wetland system or gravel reed bed system at all? These would filter the grey water and then you could store the final effluent in a pond as a reservoir for use in the garden. For a typical Irish house I'd estimate a size of about 50m2 for a constructed wetland or half that for a gravel reed bed. This will get the final effluent relatively clean - but by no means drinkable. For irrigation of edibles, you need to be sure that you're happy with the ingredients in your cosmetics, shampoos, soaps, cleaners etc. Buying all your stuff in health stores is a good start - but no guarantee of perfection.

Wetlands and reed beds have been used in cold climates; the residual warmth helps them to stay thawed for most of the year. Have a look into this more if you're worried about frosts.

I'd still recommend a grease trap first. The soil based constructed wetland has the advantage that solids don't really cause problems. For other differences have a look at www.wetlandsystems.ie/reedbedsystems.html

Another thing to do is the Oasis Design approach and just use willows or some good local tree as a firewood crop.

Be sure to follow local codes so that you don't have to undo hard work.

have you built your system yet? I could give you some advice depending on what stage you are at in construction. I have built a functional cold climate greywater system in zone 3b-4b. I will be happy to share my experience if you still need help

bjorn

Bjorn, I would love it if you start a new thread all about your successful cold-climate greywater system!

bjorn deluz wrote:have you built your system yet? I could give you some advice depending on what stage you are at in construction. I have built a functional cold climate greywater system in zone 3b-4b. I will be happy to share my experience if you still need help

bjorn

While I'm extremely curious to see your grey water system (good design that I can learn from is always welcome), I've already implemented a "system" which is a lot simpler than the one I described originally.

It consists of:

- grease trap under the kitchen sink
- all grey water (kitchen sink, bathroom washbasins, showers, washing machine) are collected into a single pipe which drains into the open (no settling tank etc.), some 10 metres downhill from the house
- from there, grey water is directed into a 15-metre long gravel ditch / swale which also collects rain water from one of my French drains - the intention here is to have the gravel "flushed clean" periodically by rain water
- the gravel ditch ends in a shallow mulched basin at the bottom of my property - the basin will be planted with willows

I switched design as I decided that the "cleaned" grey water that I had originally intended to obtain did not justify the expense in terms of money, work, and space taken up by the tanks and other elements of the initial design. You may ask why have a grey water system at all then.  The answer: as a minimum, by separating grey water from black water, I ease the burden on the septic system; the grey water draining into a swale and mulch basin will benefit the landscape during dry spells in summer; and finally, as the pipe drains into the open, I still have the flexibility to modify the final segment of the design if I want to add new elements later on (e.g., a wetland, small pond, etc.).

I hope it will work as expected. The "system" is already built (except the planting of the mulch basin) but not tested yet (we have yet to move into the new house & start using the plumbing).

I'll try to post some photos soon.

Greetings Levant/bjorn:

"I switched design as I decided that the "cleaned" grey water that I had originally intended to obtain did not justify the expense in terms of money, work, and space taken up by the tanks and other elements of the initial design. You may ask why have a grey water system at all then.  the answer: as a minimum, by separating grey water from black water, I ease the burden on the septic system; the grey water draining into a swale and mulch basin will benefit the landscape during dry spells in summer; and finally, as the pipe drains into the open, I still have the flexibility to modify the final segment of the design if I want to add new elements later on (e.g., a wetland, small pond, etc.)."

I have a similar perspective to yours and live in a colder climate. I'd love to see some pics/maps/diagrams. I have a grey water system plumbed inside my home, but it currently goes...nowhere, except back to the septic system until I flip the diverter lever. Expense, using the elements that make the water "grey" and future design flexibility all seem like the most important design parameters to me.
Thanks, Peter

John French wrote:have you built your system yet? I could give you some advice depending on what stage you are at in construction. I have built a functional cold climate greywater system in zone 3b-4b. I will be happy to share my experience if you still need help

bjorn

I'm with Rebecca.  I would love to hear about this.

Sorry about the late reply, I don't get on this forum that much, when I get some time I will post a drawing of the system and explain what has worked and what has not. I guess this is to let you know I haven't totally forgot about this and I will help as much as I can. thanks! Bjorn

I also am very interested in grey water systems for cold climates (zone 5 / 6). Certainly not as cold as some - water pipes are typically only buried 4 ft. - but we do have winters like the one just past where a lot of pipes at 4 feet froze. I'm still in the planning stage with the house, won't start building until next spring, but it will definitely have a grey water system. Still debating about whether to but in a septic system or stick with composting toilets, but that's another subject.

So thank you to everyone who has already contributed such useful information and please keep it coming!

Carla