Grey water recycling

So, no. 1 spawn has a summer environmental project to do, and she’s thinking about doing something about water conservation (which given that much of SE England has less rainfall than Lebanon isn’t a terrible idea).

This has obviously led onto idle thoughts of grey water recycling. Anyone doing this? I gather the issue in the UK is that water/sewerage is cheap, but presumably there must be some water usage/CO2 footprint of sewage processing benefit?

Today is the 5th anniversary of me watering the garden with our shower water. 60 litres a day.

Still use rain water for anything we eat.
Washing machine water goes on the grass.

I read somewhere in the process of idle Googling that ⅓ of most household water use is toilet flushing, which seems a bit wasteful when it’s clean tap water?

issue appears to be storage and legionella

We do this at work to some degree, although ours is combined with black water and we have a rather large bioreactor/membrane/filtration skid that gets everything to almost potable water quality. We run A LOT of tests on the effluent to prove this which will be a struggle to do from home, although some pH indicator strips and a swimming pool chlorine test kit might be easy enough to come by and could give you an idea of how any treatment you’re doing affects the end product. Not sure if they’d be sensitive enough but worth a look.

For DIY treatment of grey water only I’d be looking at a dual stage fine sand/carbon filtration set up. Maybe a holding tank for grey water that slowly feeds through sand then activated carbon filters into a storage tank? Have a look at this paper for some ideas: https://ijisrt.com/wp-content/uploads/2018/04/Comparision-of-Household-Grey-water-Treatment-using-Slow-Sand-Filter-and-Slow-Sand-Aided-with-Activated-Charcoal-Filter.pdf

Not sure there’s much need for treating it if all it’s doing is diverting into the flower beds? The soil will act as one big biological treatment plant as long as you don’t use anything too harsh to clean the shower (e.g. put dilute bleach in a spray bottle to clean it rather than sloshing the bottle around, or use the ecover stuff that’s safe for septic tanks).

I put some thought into is but
a) our garden slopes upwards so would need a water butt at the house, a pump and another at the top and then hoses to let it drain into the beds by gravity.
b) we only have one downpipe and it’s boxed in, inside the house so splitting brown/grey water would need major renovations.
c) We already have 2 big water butts which are enough to last about a fortnight, so we only have to use tapwater after a couple of dry/hot weeks (just in time for a hosepipe ban, dammit). And most of our beds are established so don’t need watering, just the salad beds.

What about a delf watering garden instead?


This uses grey water to feed plants in the most efficient way with correct dosage and minimal effort.

I honestly despise the fact we flush our toilets with drinking water…

I’d love to build a house with billions of gallons of underground water storage, simply to collect rain water. This’ll pump UP into a header tank, which directly feeds toilet cisterns (only). The header tank would have a SECOND ballcock that’s mains fed, that would be below the groundwater store one..thus if there’s no rain water, the header will still fill from the mains…

DrP

We have this for all wastewater.

Wastewater Treatment Systems

@DrP If you’re building from scratch why not flush the toilet(s) from shower/bath grey water rather than rainwater? Is it the need for filtration etc?

I’d love to build a house with billions of gallons of underground water storage, simply to collect rain water.

Pretty standard outside urban Australia. We have several thousand gallons. In laws used to have 93,000 gallons (father in laws root moulding business, so he had massive test tanks) for drinking and firefighting.

The only problem with storing underneath is you need a generator as back up during power cuts. Ideally you pump up a hill or use a tank stand and store… not always practical.

That raises the question about which Australian state capital gets more rain than London (all of them)

Idle Googling suggests that grey/rainwater reuse is more of a thing in countries where water and sewerage have been expensive, or where water is limited (both of which could be the UK in the not-distant). Am I right in thinking it’s increasingly common in new commercial buildings?

@ratherbeintobago  .  it’s just a thought experiment at the moment! No intention or ability to currently act on it! I guess it would make sense to also route sinks and baths to drain into the grey water storage too…
But I just can’t help feeling that, with a house of several teenage boys, rainwater is likely to be cleaner…!

Also, not sure if you’d get frothing issues/pump issues with soaps etc coming in?

You can get toilets with a small sink above them, and THAT rains into the cistern… that’s cool…

DrP

Aye, have seen those. A few issues though – sink offset to one side would be ergonomically better (unless it’s a very small bathroom), and unless there’s some sort of interlock that stops the cistern refilling from mains until the sink has drained, I suspect most of the sink run-off will go straight down the overflow?

it seems some of them are ONLY plumbed into the tap…. so you HAVE to fill via the tap!

Also, you’d feel less guilty about peeing in the sink i guess…

DrP

DrP
billions of gallons of underground water storage simply to collect rain water

cool idea

DrP
This’ll pump UP into a header tank, which directly feeds toilet cisterns (only).

huh, how many toilets do you have?

Ha! Got 5 loos in our current house…

Hence why replumbing all those NOW would be too much.
But if I were to build a house from scratch (which, may I add…have no plans to) then you could simply run separate greywater piperwork..

DRP

DrP
Full Member

Ha! Got 5 loos in our current house…

Is that why they call you Dr P ?

(IGMC, etc)

I use the water from the tumble dryer and the dehumidifier for watering the plants in the garden.

@DrP I’d be very dubious about there being enough water from hand washing to fill the cistern, though? Unless people are taking an “if it’s yellow, be mellow” approach, or are our 10yo.

That raises the question about which Australian state capital gets more rain than London

All except Adelaide… and South Australia has the highest rate of  rainwater tanks (or did 18 years ago when I last checked).

There is a housing development in edinburgh that reuses greywater – it has 3 reed beds to clean it

Just spent 3 weeks in northern India using an earth toilet. Two ‘chambers’ per toilet, one of which is in use and the other closed for a year before being dug out and used on the veggies. You squat over a hole then scatter a spadeful of dust and sawdust.

OK – so it’s not a room to take your favourite mountain bike mag for a read and a strain, but you get used to it. Like many other things – on my return we do seem so incredibly wasteful.

Today is the 5th anniversary of me watering the garden with our shower water. 60 litres a day.

Thats interesting, the RSH advocate against not doing that.

Does it not depend what you’re watering? Anything you’re going to eat = probably not for grey water?

Rainwater keeps my garden watered.  I have 2x 220l butts.  One down pipe for me and my neighbours house (on my side of the fence) fills those up with a few hours of heavy rain.

I also use this ‘clean’ water to top up/ change the water in the raised fish pond.  I have another water butt by the pond where I empty the water from there to use on the garden.

Be good to rig up some grey water system though.  Sounds like a nice project

I work in the industry and Greywater recycling is usually one of the first items to be ‘value engineered’ out on projects. Of course there are green credentials, but money is usually more wisely invested elsewhere.

I worked on an interesting project many years back where we were looking at using urine from urinals to provide nutrients for a green wall… we dubbed this ‘peeponics’!

I wonder if that will change with climate change and increasing scarcity of fresh water?

I think things are changing already here. Not so much recycling of water but new housing developments in my area require either solar panels or rainwater tanks, and that’s in places that have access to reticulated water.

Years back I worked on the early stages of a project to develop aquifer storage recharge in a drought area on east coast Tasmania. A colleague had developed a water efficient toilet system and left the firm to to progress it. If there’s efficiency savings and money to be made it will happen I think.

Thinking about this, I genuinely need to harvest rainwater in our new place… anyone got links to cheap water butts? They should be free IMO – given out by the council…but hey ho!

DrP

Whereabouts are you? There’s one in my garden you can have.. (Oxford)

I’ve got a cheapie council water butt. It’s faded badly and isn’t exactly level.

Saw this on the internets and thought it looked like a neat way of doing things:

So, thinking more about this, if you had a basin that drained into the toilet cistern, is there some sort of valve you could have so the cistern didn’t fill while the (cold) tap was running?

@DrP I think that if you just want the harvest water for the garden the standard water butt from Wilko or similar shops are about as cheap as it gets. Butts larger than 200 litres get more expensive as they need to structurally stronger. You can double or triple up.
The other way to do so cheaply is to get a second hand 1000 litre IBC. You need a black one to prevent algae build up but very cheap. If you want to use rainwater for toilets it gets a bit more complicated as you need to have tank, pipe, pumps, etc protected from frost which usually means either burying them unless you have cellar or underfloor space.
You don’t need to use a header tank for flushing though. A system pumped directly from your rainwater tank should be fine. I looked into doing it (and may yet). One of the limiting factors for us is getting the tanks under the house. I did work out that it could save us £200 a year from our water bill for 4 of us (we are metered). Good luck with the project.
Edit: if CO2 footprint of water is needed for the OPs school project there is a government spreadsheet that tells you average CO2 for all services, electric, gas , water, etc. It’s the standard document for most companies to report carbon footprint.

A friend of mine has a passivhaus/autonomous house near Worcester, designed from the ground up. All water derived from the roof, stored/filtered in the basement via 10 man sized cylinders. The loos are composting, straight drop from the first floor into a basement composting unit that provides fertiliser (and thus loos don’t use water, just a handful of sawdust you chuck in). Great house and an interesting concept – there’s loads online about autonomous houses.

This is the place (that’s the original designer/owner):

There is quite a bit on environmental agency website I recall. The main issue is that grey water contains skin and or food particles (depending on it’s source) bacteria feed on these so it is I *think* although may be required that the water is stored for no more than 48 hrs I think. So I’m it you dump it on veg beds regularly.

I can’t find the environment agency link but this covers the rough points but in less details

Reusing Rainwater and Greywater

UK water is highly variable in price. One of the biggest costs (and CO2 productive) is pumping. At Welsh Water the cheap water came from upland sources which required little treatment and little pumping. The next most expensive came from lowland river gravel extraction – not much treatment but very expensive pumping. Lowland river extraction required both elaborate treatment and high pumping costs.

And chalk aquifer extraction in the South East, usually from the deep chalk aquifer so typically below 30m.