I thought I would share an email that I wrote this week.
Dear Permaculture friend
I have extracted the text from your original email
> I’m involved in a project where a number of bungalows will be built
> plus a farm shop with an attached cafe. As there is no mains drains
> we are having to consider a treatment plant of some kind. Is it
> possible to do permaculture with black water as well as grey
> (yes I know grey water can be done)
I am replying from the Earthship design perspective, not a Permaculture perspective. I am assuming that you know a bit about Earthship systems, but if not, please ask for further explanations.
The original Earthship designs were created with the desert conditions in New Mexico in mind. These sewage systems do not discharge any water into the environment for the simple reason that they want to retain any water for growing plants and creating a green space in the desert – a very much appreciated commodity in that environment. A soakaway would get rid of the excess water, but it would not feed any plants.
The result presents us with an interesting prospect from an environmental, sustainability viewpoint: if you do not discharge any water into the environment, you are not making any impact on the environment – a great example of taking responsibility
But being practical about it, in most other climates we do not need to be so extreme and discharging processed sewage into the environment is acceptable. If we process our sewage to a high standard, then the impact on the environment is minimal and often beneficial (don’t forget the ‘nutrition’ present in wastewater). Such methods are often used and accepted by the authorities in remote locations in the UK. You may want to process your sewage to a _better_ level than the legal requirements and to always keep the impact on the environment in mind when ‘producing’ waste water (e.g. choice of detergents, consider that chemicals in medicines may pass through the human body and end up in the wastewater).
There are various approved and reliable methods, for example: reed beds, Findhorn’s Living Machine, septic tank.
Our experience with the Earthship systems:
1) the Grey Water Bed is indoors and works very well, but it creates a very humid atmosphere inside; you will need regular, good ventilation to maintain good air quality (many more air exchanges than building regulations specify)
2) the Black Water Bed (according to building regulations) must be at least 15 meters away from the inhabited area; that puts it outside; we have build a greenhouse to keep the plants active during the winter, but even then the lower temperatures and reduced daylight reduce the capacity of the black water processing. (composting toilets seem an easier option)
3) the capacity/size of Grey and Black Water Bed botanical cells: in the Earthship documentation we can find formulas to calculate their size, but this is based on very low water consumption (and therefore low wastewater production): Earthship residents in New Mexico live off the rain water they get (on average 8 inches a year). I suggest that, in our climate, we would need much larger botanical cells if we do not want to discharge any processed sewage into the environment. I wonder if we could use Earthship-like botanical cells as filtering systems (with a soakaway) instead of fully closed systems (will need to be demonstrated to work for the Environment Protection Agency)
I hope the above will assist you in your planning. Please do not hesitate to ask further questions.
Thank you for your willingness to take responsibility for the impact you make on the environment.