Author Options:

Greywater reusing Answered

hello everyone some time ago I started some research about greywater reuse because I understood that it can be very helpful for everybody after some research Icame up with a concept wich is like this:

1-the water enters a container after going through a filter wich gets larg particles

2-it goes through a ceramic filter for smaller particle for smaller particles

3-A RO filter gets the chemicals and super-small-particles

4-A container with a UV lamp wich kills the bacteria

But there are some problems

1-I cant be sure about the water quality

2-I am concerned about the chemicals in detergents


The forums are retiring in 2021 and are now closed for new topics and comments.
Jack A Lopez
Jack A Lopez

Best Answer 1 year ago

You have written an outline for a process to turn greywater back into drinkable whitewater.

And I think that is an approach that only makes sense if drinkable water is expensive, or unavailable. Like for example, if you are Matt Damon, trying to grow potatoes on Mars.


Or if you're living a neighborhood without municipal water, or a water table close enough to drill wells into. As an example, there is a neighborhood outside of Taos, New Mexico, consisting entirely of Earthship style houses.


For people living there, drinkable water is either captured snow or rainwater, or water that has been transported in, e.g. by truck.

If you are wondering how Matt Damon (I mean, Mark Watney, the astronaut played by Matt Damon) was getting his drinking water, I am kind of guessing the "hab" he was living in, had some kind of machine that removed water from the air, and maybe also a machine that recovers water from urine.

The reason for my guesses about these machines, is the International Space Station's ECLSS (Environmental Control and Life Support System) has machines that recover water in this manner. I mean, I've never been there, but the Wikipedia article for, "ISS ECLSS" has a section titled, "Water recovery systems"


Actually the Wiki article for "Earthship" also had a section just about water (including water collection and disposal as graywater, blackwater, etc) here:


Also Wikipedia has an article titled, "Atmospheric water generator," about machines that recover water from air.


Regarding your, what you call, "some problems"

1-I cant be sure about the water quality

Well, then don't drink it. Unless you have to. I am hoping you do not have to.

2-I am concerned about the chemicals in detergents

Detergents are usually sodium salts of anionic surfactants. Actually these are analogs of old fashioned soap, which is a sodium salt of a fatty acid. In other words, for a true sodium soap, the cation is Na+, and the anion is this long hydrocarbon chain (CH3(CH2)n), truncated with a carboxylic acid group (COO-)

If you're using your greywater for irrigation, for growing plants, the microbes in the soil can deal with most anionic surfactants. Of course they can deal with fatty acid anions, like from a true soap, because fatty acids occur in nature. The sodium ions (Na+) are not great for plants, to the extent they will raise soil pH; i.e. alkalinity.

Actually, I am just copy-paste the "Irrigation" section from Wikipedia's article on greywater, because it is pithy. Here:


Most greywater should be assumed to have some blackwater-type
components, including pathogens. Greywater should be applied below the
surface where possible (e.g., via drip line on top of the soil, under
mulch; or in mulch-filled trenches) and not sprayed, as there is a
danger of inhaling the water as an aerosol.

In any greywater
system, it is important to avoid toxic materials such as bleaches, bath
salts, artificial dyes, chlorine-based cleansers, strong acids/alkali,
solvents, and products containing boron, which is toxic to plants at
high levels. Most cleaning agents contain sodium salts, which can cause
excessive soil alkalinity, inhibit seed germination, and destroy the
structure of soils by dispersing clay. Soils watered with greywater
systems can be amended with gypsum (calcium sulfate) to reduce pH.
Cleaning products containing ammonia are safe to use, as plants can use
it to obtain nitrogen.[14] A 2010 study of greywater irrigation found no
major health effects on plants, and suggests sodium buildup is largely
dependent on the degree to which greywater migrates vertically through
the soil.[15]

Some greywater may be applied directly from the
sink to the garden or container field, receiving further treatment from
soil life and plant roots.

The use of non-toxic and low-sodium
soap and personal care products is recommended to protect vegetation
when reusing greywater for irrigation purposes.[16]

Obviously the main way to keep unwanted chemicals out of your graywater, is to avoid putting them there in the first place.

But can this be done without sacrificing the effectiveness of your existing detergents? I mean sure, you could switch all your 'tergents over to just plain soap and ammonia-water, but will you still be able to get the same level of cleanliness for your skin, hair, dishes, clothes... and other things typically washed at home?

By the way, there are examples of surfactants that are persistent pollutants, i.e. cannot be metabolized by microbes, cannot be broken down in soil,


but these days, such chemicals are hard to find in ordinary consumer products, thankfully.

Although one that comes to mind is PFOA (perfluorooctanoic acid)

and the similar PFOS (perfluorooctanesulfonic acid)

In the bad old days (BOD) these were used in some kinds of fire fighting foam, apparently used in large amounts for fire fighting practice drills at military bases all across the Former United States.


Also I think they used to put PFOS in Scotchgard (R), which was this consumer waterproofing product, but I think they changed the formula years ago, presumably to something more easily broken down by the natural environment.

Electronic guy
Electronic guy

Reply 1 year ago

Thanks for your nice answer I actually got my answer after reading your answer and some other sources.

Jack A Lopez
Jack A Lopez

Reply 1 year ago

I am glad I could help, even if just in a small way.


1 year ago

Don’t use detergent, instead use biodegradable dish soap, shampoo, etc.

Jack A Lopez
Jack A Lopez

Reply 1 year ago

How do you tell the difference?

I mean, between detergent and not detergent? Or between biodegradable and not biodegradable?

You make it sound very easy. Like a binary choice. Just pick one or the other.

Are there some clues on the product's label I should be reading?

If it is that simple, then perhaps I have been overthinking the problem.