Potable water from rainwater harvest

Dear all,

I am living in a permaculture community with 11 other people in Belgium. A country where it very often rains. We have a beatiful roof on our communal house with brick tiles on it.
We are looking for a system (above ground, no pumps) to purify our rainwater in to drinking water. I have heard about sytems with plant filters in combination with active coal.
Does anybody know a good rescource to design a system that can fill in our needs.
It just has to be healthy and safe drinking water for 12 people.
It doesn't have to be always available. We do have groundwater backup.
We would love to make it ourself and not use pomps  or electricity.

Hope anyone can help?

Thanks,
Josse from deweegbree.be

Take a look at this other thread.

https://permies.com/wiki/73798/Catch-Rain-rainwater-catchment-book

A "Slow Sand Filter" sounds perfect for you.  
http://www.slowsandfilter.org/

A single 55 gallon (200 liter) barrel should be larger enough to filter drinking water for a dozen people, if you want more clean water for washing, etc. you'll probably want more.

Slow sand filters work best if you can keep them around room temperature (15-25° C) and you need to keep water flowing through it constantly or the biological filter will die.  Early on this might be 350-400 liters a day, but as the filter matures it should slow down to around 200-250 liters a day.  If you let the biological filter die then it can takes weeks before it starts producing safe water again.

If your rain water storage tank is elevated at least 1 meter, then you can just use gravity to flow the water into the slow sand filter (through a float valve).  The outflow could go into a second barrel to temporarily hold the clean water.  You can then use a hand pump to get the water out of the holding barrel.

If you can elevate the rain water tank 2 meters off the ground, then you could elevate the filter and holding tank 1 meter and then just plumb the holding tank into your kitchen faucet, etc. and just let the water flow out by gravity.

A "Slow Sand Filter" sounds perfect for you.  
http://www.slowsandfilter.org/

thanks peter, this system looks suitable for irrigation and cleaning and so on. But the website tells me that it is not suitable for drinking water.

Take a look at this other thread.

https://permies.com/wiki/73798/Catch-Rain-rainwater-catchment-book

Matt, Do you know if the book describes a system to make potable water from rain water?

Thanks

Josse Horsten wrote:

A "Slow Sand Filter" sounds perfect for you.  
http://www.slowsandfilter.org/

thanks peter, this system looks suitable for irrigation and cleaning and so on. But the website tells me that it is not suitable for drinking water.

....
Thanks

No that is not what the website says.  It says that"they" were not using it as drinking water, it doesn't say that it can't be used as drinking water.  As long as you use clean sand (preferably filter sand rated for potable water) and don't have excessive amounts of chemicals coming off your roof, then the filter will produce potable water with little to no bacteria in it.
Also note that the majority of problems they have had with the filters in this study were caused by letting the filters freeze.

Slow sand filters are used to produce potable water for millions of people currently, everything from household level to huge filters used by cities, etc.

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


FWIW millions of people around the globe have been drinking rainwater collected from roofs for centuries, WITHOUT filtering it.  Many still do.

The easy answer is to use a 1st flush gutter/pipe system automatically throw away the 1st gallon of rain that falls that is filled with all 'dirt' from the roof.
Next you needs a tank on elevation to gravity feed.
Then I would use one of those ceramic slow gravity filter in the kitchen.

For showers if the water temp in the tank is over 70F/21C the shower spray will get you lungs infected and sick, but baths are okay.
In the winter the tank/pipe bursting is a real serious concern.

Placing some activated carbon in a sack in the water tank will help with metal in the water
A dark tank will prevent algae growth
And a pre/sediment filter might help the main ceramic filter.

https://www.thoughtco.com/can-you-drink-rain-water-609422 pretty much tells you that rain water is by its nature mostly safe to drink as is. Assuming you are not downwind of a toxic hazard like a chemical plant or Chernobyl.

And it also tells you the relative truth about rain water being 'cleaner' than city water.

"Most rainwater is safe to drink. Actually, rain water is the water supply for much of the world's population. The levels of pollution, pollen, mold, and other contaminants are low -- possibly lower than your public drinking water supply. Keep in mind, rain does pick up low levels of bacteria as well as dust and occasional insect parts, so you may want to treat rainwater before drinking it."

In Australia and other places around the world (Australia being the only first world nation I can think of that does this) the tanks are not light tight, instead they allow a bit of light to filter into the water to promote the growth of the algae that accumulates around the inner surface of the tank. While that may sound like a bad idea, the reality is that it acts much like a biological filter that one would use plants in a pond for.

The first flush system is ideal if you have lots of dust between rains or leaf matter or bird feces. If you get rains on a fairly frequent basis and don't have birds living over/on the roof you most likely will not have to flush the system after every rain.  

The first thing you need to do is get an assessment of the cleanliness of your rainfall.  If you are downwind of industrial/urban places you may want to collect rain water over the course of several months of rain and have it tested for heavy metals and known toxins that would be linked to industry.

If you get a clean bill of health on your water from toxins (lead, uranium, "acid rain" etc), then a simple sand filter should work.  If you have low measurements of toxins then you will want to use this along with activated charcoal.

Frankly, other than a sand filter (simple one) I would just go with a pitcher filter for drinking water or a sink faucet based filter. These are relatively cheap, usually have high quality filter replacements and doesn't require you to build a secondary tank or do more plumbing.

And unless you have radioactive rains, then washing with rain water is perfectly fine.  Note rain water is typically dusty (thus brown) but that dust settles out once the water is in the tank. Sediments are there because rain drops form around dust particles.

My father simply collected rain water from the roof and we used that to shower in. It went from the roof to storage tank to a black 55 gallon drum where it heated in the sunlight and we used it as is. We didn't die or get sick from showering in rain water.

I’ve lived rurally my entire life and the house we’re in now is the first that’s ever had filters of any sort. Best thing is no more little bits of organic matter in my glass of water. But otherwise we’ve never gotten sick. My family holiday home water is straight out of a nearby bush creek.

Water supply is my bread and butter in Australia.
Unless you deal with acid rain, generally tank water is perfect.
The first flush units mentioned work well, but a more important aspect is tank volume.
The greater storage volume you have for your drinking water,compared to your consumption, the greater time will allowed in the tank for the water to clean itself and settle out particulates [ solids]
A trick is the have a floating tube with the inlet hanging say, 6 inches below the water surface and the base connected to the tank valve.
That way you are drawing from the top, which may improve the cloudiness a bit.
We have all sorts of fancy things to clean etc, but generally a top mesh [ fly wire size ] filter with fine mesh to prevent leaves and other bits, including birds, animals etc from getting in is all you need.
Over here we often design the tank size to match the expected flow from the roof.
This involves knowing rainfall data, roof size and then allowing for say a 4 month period without rain, which is common here.
In your case with plenty of rain, make sure its big enough to allow for settlement time.
I will need to think about that for you.
We plan for no rain for up to 12 months and in some cases 10 years.
My average rainfall is 450 mm per annum sometimes 300 mm total.

Have a look here also
Benefits of rainwater collection