Recycling and Purifying Grey Water for Shower?

So here is my idea: have shower water go through a slow sand filter, then through a UV filter to be recycled into the shower, dishwasher and washer machine. I figure this is safe, but I am wondering if I can recycle the water from the washer machine, dishwasher and kitchen sink, as well. Basically, since we will be using composting toilets, I would like to recycle all the rainwater that we collect, over and over again. Will the combination of the slow sand filter and UV filter make it safe enough to shower? to drink?

The sand would take care of most particulates the UV would do some sterilization. You'd still have a lot of biologicals. Washing machine use? probably. Uses where it could be possibly ingested, I would be extremely leery. I'm pretty sure it would need more cleaning. However, you make an experiment of it and have it tested before you used it for potable purposes. The results could net you information on what further cleaning was necessary.

Here's a system that says it does "progressive filtration for both Mechanical filtration and Biological filtration plus UV-C disinfection. Treated greywater can be reuse for indoor-toilet flushing, laundry as well as outdoor garden irrigation!" But even they don't say to use it for potable water. And honestly, you could do all of that without this system as well. (and I'd hate to clean those filters - ick!)

http://www.aqua2use.com/products/gwts1200.html

SLOW sand is a biological filter and doesn't adapt to rapid changes very well. They really need consistent feed source. I would be worried about the heat from the water cooking/killing the biology. Maybe if you have a holding tank to temper or recover the heat.

R - thanks for that! I actually didn't know there were different kinds of sand filters. Proving once again that you learn something every day...

http://en.wikipedia.org/wiki/Slow_sand_filter

How much rain do you get?
Assuming that you get enough and you plan on watering your plantings anyway, a large tank and/or catchment surface might be simpler.
Use the water once and then irrigate.
I am planning on flushing toilets with grey water, and washing cloths with rainwater , along with grey water irrigation.

We get plenty of rain 6 months out of the year, but almost nothing from Dec to May. We are planning on building a 20,000 gallon cistern below ground and a 10,000 liter water tower, for about 20 people living on site during the dry season. I just don't have enough experience to know if this will be enough.

Does anyone know how much water we should plan for? Also, I am looking for a zero input filter for the shower. From my understanding, it looks like the shower uses the most water, and there should be a low tech way to filter that water for reuse in the appliances and even the showers.

Is this filtration system just for your house? If so, there are a couple of methods you COULD do for drinking water.

1. Reverse Osmosis filter. Things like a Sawyer filter is guaranteed for 1 million gallons. It's relatively quick at filtering, and will remain steady if you're doing a sand filter for particulate first. It will need to be backwashed every once in a while, and it isn't for high pressure systems. This option is meant for a gravity-fed system with half a gallon sitting on top of it. There are lots of ways to make this work, it's just one option.

2. Passive solar distillation. This is mentioned second because it is inordinately slower. Most setups only produce a maximum of 1 gallon of water on a sunny day. The larger it is or the more you have, the more you'll get out of it. On the plus side, this is DISTILLED, and you wont have any particulate or bacteria afterwards.

For non drinking water, I'd recommend adding a layer of charcoal. This will help filter more of the particulate. It'll work fine for flushing toilets, but I probably still wouldn't want to shower in it or wash my clothes. (just my two cents.)

Well, FEMA says you need 1 gallon per day per person--but that is EXTREME emergency rationing.

A typical fast shower is 5 gallons on-grid, probably more like 10--figure 2 gallons for a decent solar shower, 3-4 if they have long hair. How often you take a shower (daily, every other, weekly, etc)? That can be unfiltered rainwater clean, as long as you don't get any in your mouth or eyes. How much do you need for laundry? That number can go all over the place, but for 20 people it will add up fast. You need a gallon+ of CLEAN drinking water and probably a gallon for cooking. Another gallon for handwashing per day. You want your dishes water to be CLEAN, too. Do the math, it is a LOT.

Go to velacreations.com and look at how they built cheap cisterns. There is a thread here about them, and Abe is a member here---he has a lot of experience in farming through the dry season.

How much do you need for irrigation? If you need a lot of irrigation water, it doesn't make sense to recycle when it can all go to greywater irrigation anyway.