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Any thoughts on treating greywater for long term storage?  RSS feed

 
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Other than the obvious "Don't"?

I'm working on connecting the shower and rinse water sink in the kitchen to a branched drain system to water some more fruit trees down in the garden.  To simplify filtering, I'm leaving the wash sink with all the grease/food particles connected to the septic tank.

My issue is that I produce much more grey water than the trees need during the winter (10-15 gallons surplus per day), and not nearly enough during our hot, dry months (May and June). 

I'm planning on building a subsurface flow constructed wetlands to process the shower and rinse sink water.  I'm wondering it this will purify the water enough to allow storing it for up to 6 months or if I'll need to additional purification.

Any thoughts?

FWIW My eventual goal is to expand my rain water collection system to the point where I can disconnect from the water company.  Having a more efficient greywater system should help during the occasional long dry spell.
 
pollinator
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Trying to store greywater is considered an error, because it will quickly turn to black water:  http://oasisdesign.net/greywater/misinfo/
 
pollinator
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The grownetwork has the water harveting expert Brad  Lancaster speaking on harvesting greywater. It's a free webinar, starting Monday, June 12th.
http://thegrownetwork.pages.ontraport.net/hgfs2017register
Our fearless leader is presenting as well!

Maybe Lancaster will touch on storage?
 
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If you are filtering it subsurface, I suspect we could say it's no longer greywater but rather groundwater.
Maybe it could be passed through the subsurface filter into a retaining pond. Kind of how  a natural swimming pool works.Plant the pond with duckweed.
Use a solar powered fountain for aeration.
 
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I know that septic systems that do not percolate up to municipal standards use a peat moss system. It creates an affective bio filter for septic waters so i imagine that it would handle gray water.
 
Joylynn Hardesty
pollinator
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Ooops. I forgot to report back on Brad Lancaster's webinar presentation.

As expected, the presentation was good. Brad Lancaster said NO to any grey water storage in tanks. But we permies know about storing water in the earth. He recommended using a mulch basin such as in the the below article at Art Ludwig's site. Scroll way down to the bottom, it's figure #2.
http://oasisdesign.net/greywater/brancheddrain/
Also Brad Lancaster said to use this for watering perennials, not in the vegie garden.

Brad's site.
https://www.harvestingrainwater.com/
 
gardener
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If I were going to store grey water in a tank, it would be an open tank with azolla and duckweed growing on the surface. These plants would remove nutrients as they become available, with the breakdown of minute  particles. The plants would need to be raked off regularly, and fed to livestock or composted. Nutrient loads in ponds managed this way, are low. Growth of phytoplankton is minimal, and mosquitoes don't like to live under azolla. When the azolla turns a crimson color, you know that there is a shortage of phosphorus, and the water beneath is pretty clean. Of course, such a system would go through some water, but in return, you'll get unlimited storage time and something to feed to the chickens.
 
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So everyone keeps saying DON'T do it but they keep talking about water that is just flowing straight into a tank. My thoughts on this are what kind of filtration system can be set up to make the water storeable in a tank? Gravity fed sand filter? A holding pond with appropriate plants that is then pumped into a tank?

I mean they have whole house water filters that can filter out viruses, bacteria, chemicals, heavy metals, etc ... so what would it take to make a filter that filters out sediment and soaps? Isn't it the same theory of cleaning the water?
 
William Bronson
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I'm pretty sure azolle fixes its own nitrogen, so it's not necessarily the best plant for filtering greywater.

I have been thinking about an in-house tank for recovering the heat from grey water.
My design would trickle greywater through a large sand filter,built of concrete block,sealed with surface bonding cement,or lined with plastic. Or both. Probably both.😁
A coil of PEX pipe would run cold water through it on the way to the water heater.
The grey water would be forced through the filter,then down the drain,since it would be wintertime.
Could grow reeds,cat tails,duckweed or hyacinth,but artificial light would be needed.


Somethings from the world of aquariums caught my eye.
In addition to using UV lights to purify the waters, some people use electrolysis. The oxygen produced is effective in killing microbes. The hydrogen must be vented.
Some of the commercial devices introduce enough oxygen as to be harmful to fish. These devices are aimed at those who got pot or other equally high value hydroponic crops,I suppose.😏
Even if you just used bubblers, keeping the water oxygen rich might keep it from going from grey to black.
 
Peter VanDerWal
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I looked into heat recovery from shower water and I don't think it's worth the cost to install.  I was looking at systems using counterflow heat exchangers, basically the drain water went through a 2" copper pipe with smaller copper pipe wrapped around the outside.  Cold water flows through the small pipe and gets heated up.
In the studies I've seen this is the most efficient way to recover heat.  Normally these studies use this to heat the cold water on it's way to the water heater.  It seems to me that it would be simpler, more effective, to heat the cold water on the way to the shower, that way you need less hot water to get the same temp shower.

Anyway, I use a heat pump water heater so we only use about 1 kwh per day to heat water and their are a few things I can do to drop that a bit.  Assuming I could get maximum efficiency on the heat recovery I could drop that by 200-300 watt hours a day.  That savings would never pay for the cost in money/resources of the heat recovery unit, let alone the cost of installing it.

FWIW the thermal mass of the water/sand/etc. in your filter idea would suck up all the hear from the shower water.  That coupled with slow heat transfer through pex means that you probably wouldn't recover much if any heat.

FWIW I briefly toyed with the idea of having a constructed wetlands INSIDE the shower.  I.e. have a large shower with the wetlands at one end filled with attractive plants, perhaps even something with pretty blooms, have the shower floor slop towards the wetlands and then the wetlands overflows to the grey water system. 
Put a large window on the shower to let in light and maybe a few LED grow lights if necessary.
I decided it wasn't worth the cost/hassle.
Might be worth it if you go with your sand filter idea.  Make it a lot easier to clean the filter if it's open on the top.
 
Peter VanDerWal
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Joylynn Hardesty wrote:Ooops. I forgot to report back on Brad Lancaster's webinar presentation.

As expected, the presentation was good. Brad Lancaster said NO to any grey water storage in tanks.



The point everyone seems to keep missing is that I'm not talking about storing raw grey water, I'm talking about storing filtered, purified, grey water.  Almost all of the nutrients and BOD will be removed before it gets stored.  The chemical composition will be closer to rain water than raw grey water.

I intend to try it out, if it doesn't work then I'll just use the tanks for storing more rain water.  I'll post my results.
 
William Bronson
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Good point about the filter sucking up the heat.
I still want to recover the heat,even if it's only for space heating.
If I had the room I'd consider putting it though a large filter to feed a large aquaponic tank both inside a greenhouse.
 
Peter VanDerWal
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If you can figure out how to recover the heat without any extra expense then, yeah go for it.   But, assuming your sand filter tank idea, doing some quick calculations I come up with maybe 500 to 1000 BTUs, that's roughly the equivalent of 1 or 2 tea candles.  So I wouldn't recommend putting too much effort into trying to recover it.

Assumptions: 
  shower water initial temp = 110° F (maximum safe water temp for showering)
  house temp 60° F (higher temps will result in less energy recovered)
  10 minute shower at 2 GPM (20 gallons total)

If you take shorter showers, or cooler showers, or keep the house at a higher temp, these will all reduce the amount of energy that can be recovered.

Insulating the sand filter tank will increase the amount of energy that can be recovered, but it's probably not cost effective.
 
William Bronson
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Interesting. Sounds like I'd be better of dumping greywater in the cold season. I simply don't have room for significant storage.
Ah well,plenty of other projects need doing.
I have a Solvia style woodchip and compost worm filter built but no greywater fed to it yet.
Originally used for treating blackwater, it should be plenty good enough to treat greywater that's going into the land scape.
 
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I intend to try it out, if it doesn't work then I'll just use the tanks for storing more rain water.  I'll post my results.


Hi Peter, I actually just thought of this idea yesterday. I totally understand what you're going for here when you're talking about filtered greywater. Theoretically it makes perfect sense to me but I'm no expert and have no idea how it works in real life. I would be very interested to hear progress on this experiment!
 
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It would be nice if there was an option for off-grid, no septic setups in cold environments where plant filtering shuts down in the winter. Having a way to process that winter water other than dumping it in the yard would be handy. I'm betting one or several books on greywater already address it, but a few I've seen say "switch back to your city sewage/septic in winter" which isn't an option.

I'm hoping to have a setup where a shower, bath sink, and kitchen sink are inside a wofati/Oehler design and all drain to plant filters and then a pond. There would have to be some diverter switch, perhaps in the bathroom, that you go from "ground level biofilter" to "below frost line mulch pit" for winter use. Fortunately I have a couple years to come up with ideas.
 
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