Is it possible to recycle gray water by solar evaporation on subtropical desert (Mojave)?

Have anyone successfully used an evaporation pond to turn gray water back to potable water?

60-100 miles north of Los Angeles, Mojave Desert is a vast, largely uninhabited land with relatively nice weather.

Right now the difficulties for homesteading is the lack of water supply and lack of precipitation.

Mojave has very little precipitation during months of April to October, it cost a lot to store enough rainwater for half a year.

Water have to be trucked in. There are city water 10-30 miles away at the grocery store, so it's possible to bring a tanker trailer of maybe 500 gallons to fill up at grocery store.

We can use incineration toilets to save toilet flushing water, so let's only count gray water (everything not toilet)
Even with navy shower of 3 gal/person/day, showering takes 12 gal for a family of 4, 500 gallons don't last long.

What if we use a solar evaporation pond under a greenhouse? A 1ft shallow pond that can be bulldozed up, bury in a layer of anti-seepage film, and have a very low rise (maybe 3ft) greenhouse over it, and then use a dehumidifier inside this green house to condense evaporated water?

My estimates: cost of anti seepage film is $0.5/sqft, cost of greenhouse dome $2/sqft,  1 sqft can evaporate 0.1 gallon of water per day under clear sky.

If 30 gallon is used each day, we need 300sqft of evaporation pond, costing $750 in above ground materials or maybe $1500 if labor is calculated.

Yes its possible, using a pond with a glass roofing apon which the evaporating water can condense and trickle away to a container.
A similar process can be used to catch dew at night.


This web page explains the mechanics of the process
Solar water still

And another which I found by searching for 'grey water distillation'
grey water distillation

John C Daley wrote:Yes its possible, using a pond with a glass roofing apon which the evaporating water can condense and trickle away to a container.
A similar process can be used to catch dew at night.

This web page explains the mechanics of the process
Solar water still

And another which I found by searching for 'grey water distillation'
grey water distillation

The 1st video is not an evaporation pond but a specific water absorbing material. The 2nd video is too expensive, concentrated solar is about 2x more expensive per kw than solar PV.

Douglas, with respect the first video is certainly about a water absorbing material, but the water can be released by evaporation.
The 2nd certainly is expensive, but I am merely demonstarting the extremes of water catchment systems.
Sometimes the mind works out a more suitable manner having seen other systems.
Thast all, regards

Douglas,

Here are some threads that you might find interesting:

https://permies.com/t/75180/greywater-moat

https://permies.com/t/129981/Science-greywater-treatment

https://permies.com/t/68885/Unnatural-Fear-Gray-Water-Systems

https://permies.com/t/89335/Quality-water-coming-constructed-treatment

Here is a book to help:

https://permies.com/wiki/88761/Permaculture-Guide-Reed-Beds-Feidhlim

I would have serious reservations about such a system for potable water. I think technically it should be possible to accomplish, but there are many risks. How do you ensure that your condensation surfaces and pipework remain clean and sterile, given the origin of the water is itself hazardous, and biologically active?

In generally grey water should never be stored, but should be "used" immediately - eg direct draining to irrigate plants. This prevent the nasty stinky build up of bacterial etc... growing in your water. leaving it to sit - especially in a warm light "tent" arrangement sounds like a recipe for nasty. Have you ever left a load of washing sitting in the machine for a few days, so it picks up a nasty stink? That is what your water will likely turn into. Even if it is safe to drink (as in, not actually poisonous), it will likely pick up the aroma of your stinky pond.

Given then need to produce safe drinking water (rather than just safe disposal of grey water) an engineering solution would probably be some combination of mechanical/biological filters.

For example a fast sand filter - which needs pumping, and regular backwashing to remove trapped particulates - might be a good first stage, to trap much of the organic material and particulate waste. These are commonly used in swimming pools to filter particulates, where the biological contaminants are killed by the chlorine.

Then followed by a series of slow sand filters - these are biologically active, remove tiny particulates, and the finished water from a well designed system is usually potable without further processing.  

Caveat - slow sand filters are not normally used for grey water, as they clog too easily and can be hard to clean. You would need to look at detailed design work to determine the sizing of the system for your needs.

Water that had been through both of these systems would probably be sufficiently "clean" to no longer be hazardous to store, but even so I would still be apprehensive about drinking it without further treatment (chlorination etc...).

And then you still have the question, is this cost effective? You would have a system that needs a fair bit of micromanagement, may not be 100% reliable, and would cost money. You might just be better off building a bigger tank  to store more rainwater through the year. Ferro-cement construction is probably the most cost effective for large scale rainwater storage, and you can customise the design to suit your purposes.

We haul water, year-round ... using IBC totes for both storage and hauling. Our family of four uses about 275 gallons (one IBC worth) per month or thereabouts. Contrast with our former city life, where we easily used several thousands per month, and paid high rates for it, twice ... water and wastewater fees.

What we found most on our homestead is that if water is not as freely available, we *use* less. For example, if a tap is just turned on and left running during a task, we'll use more; we have small water dispensers with taps at every sink, so "the faucet doesn't have to be running the whole time" you are using the sink.

Low-flush toilets, which are flushed with greywater from bathroom sinks, for double use of water ... and many more such tricks.

The worst offender was the standard (big) washing machine, at about 25 gallons/load, which we recognize, and use sparingly; we use the little washing machine/spinner combo as much as possible ...

The big dishwasher was removed/recycled, and we have a little countertop version ... 1.5 gallons, the output of which is used for pots & pans.

The point is that, if hauling water, it can benefit from the same design principle as solar power ... if not lots of energy-guzzling devices, no need for massive solar installations. If water conservation techniques are in place, less water will have to be hauled. Try not to look at it as XX gallons/person/day, but as systems and patterns of water use, each of which can be tweaked to get down to almost nothing.

Water hauling is certainly feasible to get by with, until other methods can be implemented, such as rainwater collection ... it's so routine that we've just kept on doing it for years now.

By separating your water uses, the evaporation system seems feasible ...

1. water for drinking/cooking use: only supplied by hauling water (a much smaller hauling load each period of refill); no filtering really necessary, as it comes from a city/county source. Get a berkey as the final filter for drinking/cooking, if possible.

2. (re)capture all non-drinking/cooking water (greywater), and:
 - feed straight into 2nd-water-use devices (toilets, etc) ... no evap needed, and minimal (if any) filtering is needed
 - run remainder through your evap system. and feed this into all other water needs (landscaping, washing machines, etc); possibly showering, with some amount of filtering, depending on evap output quality

3. a buffer system of two tanks, one of which holds hauled water, and one of which holds evap water. each is a buffer targeted at the appropriate devices:
 - evap buffer tank never goes to drinking/cooking needs, and goes to all other needs
 - hauled water buffer tank feeds only drinking/cooking, gardening, etc.

Separation prevents cross-contamination, and filtering (if any) is now sized/scaled to each output as needed.

Seems reasonable so far ...