Underground Grey water system

I'm considering using a couple of those square metal caged plastic fluid containers (4 foot cubed, I think) {I can't recall what they are called}, buried underground 5 feet or so and 3/4 filled with mulch/fungi, and worms. The grey water would flow into and through one, and then into the next, before going into the ground water system (or possibly with the additional step of a dumping in the middle of a deep hugulkulture trench downslope).

I'm considering doing this because I want to process the grey water below the frost line (which can be substantial... like 4 feet, here) before having it go into the groundwater.

There is a possibility that this could be under the floor of a greenhouse or solarium type building to further protect it, and so that I might be able to access it with an very heavy insulated hatch top.

The following are my thoughts on the system you have described:

I think that harvesting composted material and worm casting would be very difficult without modification of the typical lid that comes with these type of vessels. I use one for water storage at my cabin and it is difficult to access the inside just for typical cleaning purposes.

The tops of the tanks would require significant insulation to prevent freezing inside the tanks, further complicating access and maintenance of the system.

If 2 tanks in series are utilized the second tank would need to be installed with the inlet lower than the outlet of first tank. In order to provide a free draining 1st tank (avoiding anaerobc conditions and providing the required worm habitat) the outlet would need to be at the bottom of the tank. This would result in burying your second tank about 1 m lower than the first.

I think that it would be difficult to control nutrient carry-over into the final greywater discharge to the aquifer as there is not the nutrient uptake that would be performed in a natural wetland system for example. I think that a natural wetland system would be impossible to maintain through your harsh winters, unless contained within a heated greenhouse, so it is probably not an ideal option.

Cold climate greywater issues were discussed in this recent thread: Neighbourhood Scale Greywater and another poster provided the following links Oasis Cold Climate and Greywater Action Cold Climae.

How much land do you have where you are considering your discharge? What are the BC regulatory requirements for greywater and what are your chances of having an inspector stop by?

I think that you could experiment for a small cost and minimal work by applying the recommendations outlined on the Oasis link. I would increase the tolerances recommended due to your climate considerations if the slope of your land would allow for it. Provide additional area to allow for ice build and to allow for containment during spring thaw.

If you do decide to experiment, consider a backup/alternate disposal option should any system failure occur. Construct all parts of the system so that they can be inspected and maintained.

Thanks for the reply, P. I will check out the links. In the meantime, I will quickly address some of what you wrote:

harvesting composted material and worm casting would be very difficult without modification of the typical lid

Yes, I was thinking that the top would be completely removed, but not necessarily just to harvest the nutrients... more to monitor it, and add mulch. I'm under the impression that the combination of the greywater and the mulch (chopped leaves and hay and char) would result in a microbial rich mixture that would, as the carbon was digested, not only not need removing often, but would instead need additions. I'm thinking of the Solviva example here. I'm not sure if you are familiar with this book.

tops of the tanks would require significant insulation to prevent freezing

Yes. I was thinking that the bins would be 3/4 full and that six inches of styrofoam would be cut and inserted into the tank, and an additional foot of foam above it. These would be sandwiched between some thin plywood on the top and plastic on the bottom and used as a hatch on top of the bins. The bins would be accessed under the greenhouse floor by another hatch (also insulated).

I was considering, if I was going the greenhouse route, that I would follow this method(a variation of which I had in my mind for a long time but was publicized in a great Geoff Lawton video that I can't seem to find now): The greenhouse would have a small solar panel that was used to run a fan. The intake for the fan would be at the ceiling of the greenhouse. Whenever the greenhouse was above the optimum temperature in the prime growing season, (conveniently a time when the sun is powering the panel) the thermostat would turn the fan on and suck the hot air down pipes that would be down in the earth or buried plastic water barrels and heavy stones, below the worm bins. The floor of the greenhouse would mostly be insulated, but some of this heat would be vented up under the beds so that that space was moderated during early and late winter, thus extending the shoulder seasons in the greenhouse. The greenhouse would be more of a solarium, insulated well on all sides but the glazing. In this way, and with the additions of foam insulation on the bins, I think that the there would not be an issue maintaining the system above freezing.

If 2 tanks in series are utilized the second tank would need to be installed with the inlet lower than the outlet of first tank. In order to provide a free draining 1st tank (avoiding anaerobc conditions and providing the required worm habitat) the outlet would need to be at the bottom of the tank. This would result in burying your second tank about 1 m lower than the first.

Yes. That's pretty much what I had in mind. I was also thinking that the bottom four to six inches in the tanks would be round rock covered by landscape cloth to facilitate drainage.

it would be difficult to control nutrient carry-over into the final greywater discharge to the aquifer as there is not the nutrient uptake that would be performed in a natural wetland system for example

I was under the impression that the fungal mycelia as well as the worms would facilitate adequate nutrient uptake. These beings do that as a matter of survival. I was also considering incorporating char to help absorb nutrients and further purify the water. I was thinking that the pipe dump beyond these tanks would be contained (protected) under a half barrel, which was in the middle of a deep hugul type pit that would also have char. This system would be below frost line as well. I would hope that all the wood would absorb whatever the worms/fungal/char bins didn't. I can't imagine that the bins and the hugul trench would not be able to handle the nutrient load of the grey water. In the summer, alder trees surrounding this pit at a slight distance would be uptaking the nutrients. These would be used to chop and drop for other projects (or perhaps chipped to mulch in the bins). I was thinking of pears and hawthorns near the pit as well.

How much land do you have where you are considering your discharge? What are the BC regulatory requirements for greywater and what are your chances of having an inspector stop by?

I have a sloped field of about 20 degrees basically sloping South, and slightly East. About 6 acres at least of land is available below this before getting near my little creek to the East or the road to the South. I do not yet know of the regulatory requirements. Although a building inspector might come by, unless he rats me out I doubt the food and sanitation inspector would come around. That said, I do not want to be polluting the groundwater. I do want to make the system adequate to do the job fully.

Interestingly the building inspector himself, I have heard rumored, has a grandfathered blackwater discharge directly into an otherwise pristine river. He doesn't have a lot of respect in the community. The entire city of Victoria has a blackwater discharge directly into the ocean, right outside the provincial parliament buildings!

If you do decide to experiment, consider a backup/alternate disposal option should any system failure occur. Construct all parts of the system so that they can be inspected and maintained.

That would be optimum wouldn't it? But I'm not sure how to go about that when I want to have so much contained in the Earth. Hmmm. Definitely food for thought.

Anyway, now i'll check out those links, which will probably make me want to simplify my plans and shut the heck up. Thanks huge for your input, P.

Another interesting tid bit... When I purchased the land, the previous owner (who worked for the regional district and so had to jump through every hoop to cover his own butt) had hired an engineering outfit to design a sewage treatment drain field. I have this blueprint. It's basically a big septic table. If they were going to allow that, with sewage, then why not what I'm thinking of doing with grey water? I'm not saying that they wont let me, but it would be so typical for them to deny the ecological option. Bureaucrats hardly ever make sense, just dollars. Unfortunately I paid for this engineered design, as the land price (that the previous owner paid two years before me), had this cost, plus the surveying costs of the original development added to my land cost.

Thanks for the clarification on your plans, I enjoy hearing the ideas and thoughts of others thinking about these issues and the best methods for a sustained winter operation.

I think that your containers will essentially be creating a healthy environment for treatment, similar to what nature creates in healthy topsoil. My perspective is however, that the environment you are creating within the containers will be isolated from the natural environment, essentially limiting the potential of the system to benefit your site. Without the ease of harvesting the nutrient rich resources created, you are eliminating the possibility of easily applying and utilizing this material. I would prefer the design of a system to most effectively use all of the outputs of the greywater resource.

I like the Solviva system and others that I have seen similar to it, your thoughts and ideas included. It is well worth experimenting with in more extreme cold weather situation, something that is definitely more feasible within a greenhouse environment like you are considering. I believe that I read that the system created has not needed any material removed after years of operation, so I think it is possible you could operate the proposed system for many years without issue, providing you can keep the system healthy.

My thinking on the nutrients within the system is that at some point, without plants to uptake the nutrients, there will be a carry over of nutrients, ie. worms digest input materials but release castings, some of which would be carried over as soluble nutrients within the treated greywater outflow. If I understand correctly your discharge would not be directly to the groundwater system but to downstream trees and plants that would happily consume these nutrients, so this is probably a non-factor in potential ground water contamination depending on the soil conditions of your site and distance to groundwater table.

You have a nice large lot to work with and a convenient slope that allows you many options for construction of your ultimate system, so take advantage of the possibilities that are not available in all locations.

Some perspective on my thinking:

For many years, I was building and experimenting with wetland systems for both greywater and combined wastewater systems, mostly in Indonesia. I experimented with many different types of grease traps, different wetland systems (subsurface/horizontal flow and vertical flow) and evapotranspiration concepts. In many cases, the grease traps eventually failed due to lack of maintenance, which resulted in subsequent clogging of the downstream system. It was definitely not install and forget and there were considerable resources used in the construction and a required maintenance component.

I met a permaculture practitioner, also working in the region, and was introduced to the concepts of the banana circle. The resulting system eliminated the grease trap and proved to be much simpler and practical for both the construction and maintenance with respect to most applications I was working on. Soon after, I started reading the information from the Oasis web page, finally ordering a copy of the book. It was at this point I realized that most simple solution possible for effective treatment was far superior to more elaborate designs that tried to replicate what nature effectively accomplishes given the opportunity. There are a couple of key take-aways that I always keep in mind based on Art's material (I am paraphrasing based on memory):

1. The best treatment of greywater occurs in the upper region of the topsoil
2. A well built and maintained mulch basin will not fail even if the system is abused (ie. grease and solids handling capabilities)

I have since tried to simplify all of my designs to best utilize the natural environment available and avoid external inputs and components that can complicate any design or maintenance requirements.

Thanks for your continued insight, P.

I am going to post more ideas, but on your 'extreme cold climate greywater' thread instead of here.