View Full Version : The Permaculture Principles Greywater Spiral Mound Design - What would it look like ?
22-08-2011, 09:18 PM
Diversion of greywater via a hose directly into the garden can be problematic in some areas. How do we design a greywater dispersal mound to minimise environmental and health risks and maximise water and nutrient reuse? How do we prevent root blockage of the pipe? How do we prevent spray drift and odour problems, mosquito breeding, water logging of soil. How do we set up composting of contaminants, growth of beneficial plants and establishment of an ecosystem for processing the greywater? How large would the mound have to be, how high, how many spiral swales would be utilised, how deep, how wide and how long would the spirals need to be and on what grade? What sort of plants should be used? Plants with space between stems that will not block up? Swampy plants? Evergreen plants, plants that can be harvested for mulch?
It is assumed the greywater is pumped up through a pipe into the centre of the mound but rather than spurting out over the surface like a fountain, there probably needs to be a cover over the end of the pipe. Should it be a larger pipe with the end blocked off that just rises up when the pump starts to release the water through the accumulated debris below? Should it be a compost bin with a sand or rock base that slowly lets out the greywater into surrounding spirals for their long path down the mound?
What are the maintenance issues? How often would the spirals need to be reformed and replanted? Will the mound grow as more organic material deposits itself on the mound? will the earthworms thrive in the walls of the swales?
Does the mound have to be round or could it be square or hexagonal? Many septic tank systems need to be almost as large in area as the house floor area of the house they are serving. I am sure that a permaculture system could be designed that is far more efficent than that and utlise the water all through the process.
Many greywater diversion systems need filters but would this be necessary on this type of system? Could it be designed that clogging just builds up and rebalances the mound distribution system?
The problem sites are on very flat clay flood plain sites with very poor drainage - any suggestions?
23-08-2011, 06:06 PM
Spiral mound as opposed to the usual linked beds fed from gravity? Pump to get to top of mound, as opposed again, to gravity?
I'd run a 25mm pipe up through the centre for cleanliness (run up side for ease of maintenance or movement), a T-piece underneath with a drain tap on the low side out of the mound (for cleaning and draining when not in use). Dirty-water sump in a holding tank at the house, running when full or once every 24 hours at a minimum and overflow plumbed into sewer (for legality reasons). Exit point would have a arrestor on it (used in hydroponics etc.), with large enough holes to allow debris through. Personally, I'd catch a lot of debris before the sump pump. 24 hour movement of water should prevent mosquito breeding.
A mound of subsoil, with concentric aggregate swales in rings on the mound. Each swale draining into the next one down when full via more aggregate. Aggregate size would be varied and significant. Each swale dug into mound, reinforced with rocks or aggregate on walls and subsoil. Once top swale filled with organic matter and/or water, potentially the second swale would be the first to take the water and so on. Bottom of mound would have a larger swale or ditch around it, reinforced with a higher wall to increase capacity in event of failure. If top swale was too large to fill, water should infiltrate down into subsoil and drain down sides and roots would chase it (maybe bog plants in first swale too?).
I'd put top soil onto top of aggregate swales so plants had a choice to use the water or not, and weren't sitting in it exclusively. Depending on amount of greywater, the lowest largest swale could hold bog plants for mulching purposes (all depending on how much water made it there). Subsoil mound could also be a hugelkultur mound too (sinkage could be an issue).
Since I just put that together in 5 mins, I see issues with weeds growing on the sides (terracing more perhaps), the pump pumping too hard through the arrestor and creating spray drift (leaves should catch that).
Callum, you seem to have considered it, what's your thoughts on the design? Am I way off track as to what you were asking? I just figured a circular mound of subsoil and rocks/aggregate is more obtainable. The pump on the other hand...
Personally, I like the staggered gravity-fed bed but I'm sure it could be done better. Me, I'm going to run tapped 50mm poly to a bed with comfrey (having read that comfrey can be a bog plant) in it and then allow the water to move from there into my drainage 'swales'/ditches.
24-08-2011, 12:46 PM
You are spot on - I will address all your points later in the day when I get a chance - great stuff - thanks for your input ! Callum
24-08-2011, 09:17 PM
A basket in the pumpwell is probably a good idea but I am hoping to set up a cover on top of the pipe where it rises up out of the mound, probably on a normal 25mm stand pipe. I am proposing to put a 90mm PVC pipe on top that will be lifted up when the pump activates releasing greywater out at its base and falling down again when the pump stops.
I am hoping this will reduce risk of plant and particle blockages. Might also help suppress noise and odour at initial pump start up.
We could probably do a gravity fed version as well where an on grade pipe is run out to the mound on an elevated earth ramp and pours into a u-tube that spills in much the same way where it rises up out of the top of the mound.
Drain valve and a valve to divert from the pumpline to other parts of the garden in summer is also important - this mound is designed mainly for use in wetter times.
I think the swales need to be spiralled down the mound to avoid any surface stagnation and probably need to be sand lined to minimise surface flows and erosion. Maybe a capture ring swale at the bottom of the mound might help balance any exit flows.
The local dispersive clays here just dissolve and lose structure on contact with fresh water so that is why sand is probably more important than aggregate because the clay gets in side the rock and sets like concrete to defeat the purpose. Sand on the other hand is fine enough to keep the clay out but also release the water over a maximum clay surface area.
I agree about putting the topsoil back on top to help sustain the plants in between the swales.
I guess the plants are there to:-
- transpire the water,
- filter the water with their root systems, mulch and stems, stem hairs, leaf litter oxygen supplies, antibiotics and microbe colonies,
- provide a source of mulch,
- displace potential weeds,
- prevent erosion,
- aesthetic benefit,
- protection and shelter for earthworms and other life forms involved with composting and breaking down the solids particals such as hair in the greywater.
- compaction of plant bases should help reduce rainfall infill and increase transpiration uptake from below,
- reduction of wastewater management system cost.
It would be interesting to see how much or how quickly the top of the mound grows with the composting process. If the feeder pipe is verticle then the solids should automatically redirect flows to self balance accumulations and flows like a river delta but in a circular cone.
Will be interested to hear how yours goes.
Under the spirals at about metre intervals I am proposing to have 300mm diameter tractor drilled holes (normally used for fence posts) down about 1500mm into the more structured clay with a better permiability and extending up into the mound through 300mm pipes that are lifted out when the surrounding soil is in place. The spoil from the holes builds up the mound and the sand provides deep soakage. The and could be bought in by cement mixer and poured into each whole as it is drilled and the mound grows wider.
Maybe a similar design could be devised for sandy sites with shallow groundwater where a plastic liner is placed under the mound and the lateral flows outwards from the mound are used to improve water quality before discharge into the sand below from the outer ring. (no deep sand core holes on this one except in the middle down to the liner maybe.
25-08-2011, 07:52 PM
Interesting. Could you draw me a picture of what you intend?
I installed greywater for a year with a Queensland government approved setup, and trust me, it was in no way that detailed. And I'm not afraid to admit, I've had greywater, almost black, in my mouth at times through tragic splashes.
My system, whilst I would of installed a Watermark-approved system, is just going to be 2nd-storey shower water, t-d into the current plumbing, tapped on each run so I can chose sewer or garden in one spot on the wall. And garden is going to be a 400mm high x 500mm, rock-walled Comfrey bed. I envision no problem with stagnating water because, during my employ, I never saw anything untoward, besides in holding tanks that were neglected. Biggest issue was soap and hair, and a conglomeration of skin cells I assume.
The systems I installed, the gravity-fed ones, picked up all the greywater they could, had a filtered bag on the inlet, and then 25mm/19mm'd out into the garden into drippers. Each run had a 19mm/13mm on the end (25mm to get the water to where it needed to be, 19mm and 13mm to add backpressure so the gravity-feed, downhills and such). Opening the end taps and washing clean water through would clear that particular run. Each dropper obviously wet the exact same spot.
I'm aware of the risks you are negating but be careful not to over-engineer. I figure once that dangerous anaerobic bacteria is exposed to an aerobic process, it's the end of the line for it. In my case, besides soap and other cleaning products, how unsafe is shower greywater going to be? I've had a lot worse over hands, face, and other parts of my skin. Your mound minimises everything, and is the safest option, I'd question if it needs to be 'that' safe.
28-08-2012, 04:40 PM
Yes please, a picture would be great. I am having trouble visualising what you are describing. I have two gray water systems on my place and at the moment the water is wasted, just running off over the grass. I want to make good use of it rather then wasting it like that.
Our gray water just runs into a holding concrete tank and then gets pumped out when a certain level it reached. I suspect there are some bacteria at work to 'digest' whatever is in the laundry, kitchen and bathroom water entering the tank.
Well anyways... I really would like to put this water to good use, so an image of what you describe would be fab :). Thanks
29-08-2012, 10:49 AM
There is no one design that fits all but here are a few pointers. I have some diagrams but want to try them myself first.
The greywater in the pumpwell will be digesting but the warm nutrient rich water will multiply them up to very high numbers and should not be held for more than 24 hours or it can become quite dangerous.
The main issue is at the end of the greywater pipe -
blockage - run the kitchen water separately to a septic tank if possible. (Kitchen water quickly mucks up most systems)
distribution - too higher application rates to soil cause blockage, surfacing and spillage over the soil. (There is a thing called a drainwave that might help achieve this without a pump or putting too much backpressure on your washing machine pump)
root blockage - weeds and root systems will block pipes long term unless barriers are in place. (Use of 100mm air gaps can help overcome root blockage)
It is important to think about overflow relief if a blocakage occurs and venting on systems to prevent odour accumulation.
I should have more on all this in the future.
30-08-2012, 04:42 PM
Hmm... a bit of stuff to think about.
I remember vaguely having bought a book about gardening with graywater... I will have to do a search in my 'library' and see if I can find it.
I am thinking of using the graywater to water fruit trees, maybe wicking beds too.
27-09-2012, 04:35 AM
I remember when we bought our first ever large acreage up in the mountains above Palm Springs California. We never knew we had a graywater line which had hooked to it the Master Shower, Guest bath sink, Washing machine and the kitchen sink. The lines had been redone under the house by the former owner and he took a two and a half inch pipe and attached it into the ground outside to a 1.5 inch pipe. Talk about disaster. One day after two weeks after we moved in it all backed up and there was sand coming up into the Kitchen sink. I couldn't imagine what it was. After doing a full investigation and discovering what he had done (which was outrageously absurd), I dug a trench following the 1.5 inch pipe to a dry wash some distance from the house. I thought the graywater idea was great but poorly constructed for the obvious reasons. Put in new line of 2.5 inch pipe to match the one under the house and everything worked perfectly.
What it did do was make me more conscious about the soap products we used in dishes, shower and washing machine. The area where the water came out in the wash became very wet and saturated, so I planted Riparian water loving trees for a habitat effect. I was in the automotive restoration business down in Palm Springs and brought home some of my countless cleaning rags. My wife decided to wash them for me, something I had always done below in the city. Now the rage were loaded with all manner of paints, solvents, oils and caustic soda residues. After the wash, I noticed all the trees and plant understory of wild rose and native currants took a thrashing. Severe leaf burn on everything. Talk about a terrible experience to burn something into your memory banks. After that we were always conscious about natural products only and utilized a water molecule restructuring system which worked off vortex compression and grounded electromagnetic hydrolysis to soften the water molecules into something less clustered. Things went from terrible to completely healed after that.
Some of my best learning has come from mistakes.
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