bio sand filter and sodis solar disinfection.

How to clean the water you harvest
This is what they do to clean the water they harvest off their roofs in India and Pakistan.    
Sand filters filter the pathogens out of water and i have even heard reports of them  reducing metals in water and hydrocarbons from roofing material in the water, though it is to reduce pathogens that they are installed, not to get out heavy metals.

  filtering water through sand i sthe way that many cities clean up on city waste water only of course in the cse of cities they are using sand on a large area of grund.
  bio sand filters are called slow sand filters the difference between slow sand filters and quick ones i¡s whether the water perculates through the sand dripping through it or whether it is driven through the sand.

     Part of the sand filter system has to do with  the soil  microbe thread because ht etop layers of the san dfilter are full of microbes as the earth is and these kill unhealthy microbes. The top layers of sand, after two weeks use, fill with a healthy community of microbes that do for any pathogens in your water. rtain gareeens are built into the landscape near lakes an drivers so run off water from our roas¡ds and such gets cleans up because earth and plants work like a sand filter does.
   One part of having a healthy population of microbes in your earth is that they keep down unhealthy ones and so increase the health of your crops and live stock by reducing their expos¡ure to pathogens.
   They also break down organic matter returning this to its basic minerals that the plants can use as nutrients.

    The Samaritans Purse Canada  charity  use these filters and say, as does everyone else, that they cut out 99 percent of pathogens. parasites. cysts and e-coli and such.
.
  Sand filters filter out pathogens but zenrainman uses them in conjunction with solar disinffection, sodis, using sodis on hte water filtered by the sand filter.
   Sodis is ultra violet disinfection using the suns rays to penetrate water in a transperent bottle or, more portable when empty, plastic bag .
   ultra violet light kills pahtogens, and is used by hspitals and public amenties to do so, there is a instrument called a steripen a pen torch that sterilises water with its ultra violet light makieng ultra violet light sterilisation easily availiable to treavelers and campers.

   zenrainman in the case of the small plastic PEt 2 litre bottle sand filter, uses the sand filter to filter out particles in the water. If you have an alternative it is better to put  pretty clear water in the sand filter. A sediment trap could be used to get rid of the sediment in water.

    A sedimant trap is a container in which water may stand till the sediment settles out.

    Zenrainman does a test on the water from the sand filter and if the water turns dark wine coloured then he puts the water in the sun for the ultra violet radiation to do for the pathogens.
   
     How a sand filter works.
    The top layer of a sand filter works through bio filtration, through the work of a healthy cummunity of microrganisms that eat up pahtogens.

   The under layers of sand work to filter out pahtogens  through-:
    Mecanical trapping the pathogens get caught in the sand. sand as a seive.
    Absorption the static electricity on the sand attracts the particles, pahtogens, to sand sticking them to the sand.
     Lastly death through starvation, because there is no food in the deeper layers of sand or air. agri rose macaskie.

  the main components of a sand filter are a container a biggish container 34 inch barrel is one size given, you need room at the top to put in water. about a third of the barrel, a few inches of gravel at the bottom oof hte bar and then filled a about two thirds full of sand.

You have a plate a betwwen the top ofbarrel and the sand  to seperate the sand from the water, so the  the water you put in will drip through the perforated plate onto the sand,  so the top layer of sand wont be disturbed by the water you pour in.

      The top two cemtimetres of  sand is the biolayer, that fills full of microbes that will eat the pahtogens in the water you filter.  The biolayer can get too full of life which stops the water running through it and then you have to stir it up a bit to break up the filter it forms. You should not stir up the lower layers that also have pathogens but in lesser quantities that don't block up the sand.
 
      The filtered water comes out of the bottom of the barrel, but the pipe that comes out of the bottom of the barrel is taken up to the level of the top of the sand so that the water in the barrel does not sink below the level of the top of the sand and so the sand is always kept wet. It is called a riser pipe.

      If you seldom use the filter you should put water in it every so often so that it does not dry out.  agri rose macaskie.

      The smalest sand filter is the two litre bottle, used for water you can buy in a shop, sand filter. It clears sediment off water and cleans out ninety porcent of pathogens, a big filter should clean out nintey nine percent of pathogens.

      It can be used before sodis, solar disinfection.

      You use 1 mm and smaller sand  in it. You can seive sand to get the smaller grains out from among the bigger ones.
      You should wash the sand to get out the particles that are too small. Put the sand in a container with water to cover it well and move it around,  as the heavy particles sink and the clay sort of particles remain suspended in the water, every time you pour off water you pour off the small dirt particles in the sand. then you refill the container full of water untill the san dno longer dirties your water. That can be fifteen to twenty waters. Do it a lot of times and you get clean sand.
  You need two and a half to three inches of sand in your bottle for it to work.

    You can see this mini water filter on you tube  under zenrainman bio sand filter PET bottle there are other videos on its use in you tube.
    There are lots of videos on ordinary bio sand filters too.

            Sodis solar disinfection uses the sun to do what hospitals and other public places have done for years, which is to use ultra violet light to disinfect the water they use. As the sun has ultra violet rays, if you leave watter in the sun, in a transparent bottle, the sun will disinfect your water.
     
            There is a instrument for campers, a ultra violet torch, that will disinfect their water or the water of those traveling to places where the water supply is not necessarily safe to drink, called a steripen.n PUt the steri pen on introduce it in the water when it will light up out of the water its rays aren't safe for its owner, an dyou stir the water with the pen which will clean thwater in a minute. It is powered by bateries.
              For sodis.
            You should use a bottle that is not too old and scratched, that lets through plenty of sunlight.
            You should use water that is clear so as to let through the sunlight.

            You clean the bottles.
              FIll them full of water and put them lying down in a place that recieves plenty of sunlight, full sunlight, like the top of a roof, on a table, on a stand made specially for them, on the ground.

            For how long.
            One video said that  in strong sulight the water would be disenfected in two hours but on a day that combines clear followed by a cloudy, followed by clear sky, you should leave them in the sun for two days. Another instruction from a sunny country was to leave them in the sun from sun up to sunset. agri rose macaskie.

I have a drawing that is drawn not as a drawing of the structure of the container of the sand filter and it riser pipe but to explain the differnt thing the sand in th efilter does to kill pathogens.
  i read some where tha tcanadias samaritans purse have known a filter of this sort to go on working e¡well for i think it was eleven years and they did not talk of changing the sand in it. agri rose macaske.

                  If you are collecting water off your roof you might want to stop the first water of the first rains that will fall on a dusty roof, so as to stop all  all the dust that has accumulated in between rains getting  into your sand filter with the water . there are lots of ways of taking off this first rain, full  of particles and dirt, this picture shows one of them ht eone in one of zen rainmans videos.The pipe that takes a certain amount of water, the first that falls reserving it so it does not enter into the sand filter.
                This pipe would stop a lot more water from entering the sand filter if you left the cap off the bottom of the pipe, so the water that had been caught in the drain on the roof fell on the ground. If the rains are the first in the season you might want to let a lot of water fall off your roof without being collected, so as to let the rain wash your roof really well. By leaving the cap off the end of the pipe which takes the first water to fall on the roof you will assure that none of the rain water that falls goes into the sand filter till you replace the cap on the pipe. agri rose macaskie.

  A way to get the sediment out of the water that you want to clean in your sand filter is to have a sediment trap.
  A sediment trap is a pond or tank or any container that will hold the water still for long enough ¡for the sediment in the water to fall to the bottom of the container and leave the water above clear. You can then carefully take the clear water from the top without stirring up the sediment in the bottom of the trap. agri rose macaskie.

What types of sand have you used for this purpose?  Does it matter?  I don't happen to live by a lot of beach sand but do have a bag of pre-washed builder's sand.

I usually catch rainwater in 5 gallon buckets from the leaks in the gutters of my rental home and think it would be nice to try some filtration on it.  I'm sure my plants won't mind one way or another but would be handy for other applications.

Thank you for posting this info Rose, it answered a lot of questions in my mind.

  Well the video on the pet bottle sand filter talks about sand of 1mm and less and the other indication i have heard is 7 mesh grains.
i have written all about it so anyone who is on the threads can read it easily but if you put in the words bio sand filter into you tube you can whatch lots of videos on it. YOu need to whatch lots to collect all this information but if you can get down videos fast and you are interested in making one, you would probably enjoy whatching all the videos.
    It seems to be widely used in places like india and installed by lots of very famouse charities, to make drinking water less dangerouse so it must be pretty safe but then they live among people with experience with the sand filters.
  Some people put another barrel full of sand on top of the main one to prefilter the water especially for summer, the sand filter is not meant to work well in heat but still pepole report on its working fairly well.
  Some people put all sorts of other material into this pre filter barrel, indeed some people put a layer of charcoal in a sand filter. THey put in materials like charcoal and gravel as well as sand. agri rose macaskie.

Great Imfo Rose.  Our Rotary Club has been buying sand filters for many years and giving them to Third world countrys for safe drinking water.  Rotary International has a big push for safe drinking water world wide,  here is one link http://www.rotary3270.org/rotarians-use-simple-bio-sand-filter-to-change-the-health-of-a-country-914 ; The article talks about what they can do.  Your 1st drawing shows the type we give to familys to supply safe water to a family.  Thanks for the info and the drawings.  They definately work,  and I am sure they can filter and help clean rain water.  The size of the filter and the vol of rain water would be a major concern in setting up a system like that. 

pa_friendly_guy,  could you give more information on the volum of rain and the size of the filter. and I do wonder about the upkeep of the filter and its life before you have to change the sand say. I did not hear much about upkeep on the videos i whatched on sand filters.
  i know its a bit different writting about things if you have experience doing it yourself and of others doing it  than if you dont and so it would be good if you with experience filled in on things you had learned from experience.
        Like i suppose if i did it without direct experience I would be worried about whether the bio layer had developed, i would want to get things started by putting in a bit  of rubbish or yogurt say even though no site says to do thi,s just to let the biolayer develop from what evers in the water though apparently nothing is in the water. What mistakes do people make? agri rose macaskie.

  If there is a lot of rain water then you would want comewhere to store the water that had been through the sand filter leaving room for more water to go through the filter.
   
In India there is a tradition of having a large underground water tank in the courtyard of your house, like a cellar . I suppose the fact that they had, in many parts of India, so much water during the monsoons, as they do get and then so many mounths of drought, made the idea of storing rain water evident. The american people who i have seen on internet just have a series of barrels to collect the filterered rain water in . if you were building a house in  adry area and wanted to do water harvesting it would be a good idea to build in an underground tank i should think.
  the advantage of drinking rain water instead of ground water is that it is less likely to be full of other poisons, none biological ones like lead and arsenic, that might be in the ground and so in water from wells.
      If there is lead in the air from metal foundries or some such, rain water may contain a bit of lead but water from the gronund is likely to have the lead that the rain might have picked up in the air and that which has settled on the ground between rains. agri rose macaskie.

The filters that the Rotary gives away are small plastic units,  maybe 40 gal.  The family hauls water from a spring , stream, or river in most cases.  That is why the filters are needed,  the streams are polluted.  I have not been there personally,  my involvmant has been to donate money.  From what I understand the Bio layer can build up and get thick over time.  They just scoop some of it off the top and continue to use the filter.  The sand lasts for several years befor it needs replaced.  The people have to be trained to use them,  as an example,  when you haul the water in one bucket,  you dont use that same bucket to catch the water from the filter.  The filters are gravity flow,  as you pour a new bucket of water in the top,  water is forced down through the filter and out the spicket that is att to a line that runs from the gravel botton of the tank to the top.  Your 1st drawing showed that design very well I thought.  The water line is not separate though.  It runs along the inside of the tank.  That way the tank is always full of water being filtered. 
  Haveing an in-ground cistern is not uncommon.  I live in western pa and we get alot of rain and have a good water table here.  There are still some people for one reason or another use cistern water to run their homes.  In most cases they do not drink it,  they drink bottles water of some sort,  or haul drinking water from a spring.  The cistern water is not general filtered much at all,  maybe a settling area to take out large particles and leaves,  that is about it.  The water is used for bathing,  washing both you and your cloths,  cleaning and flushing.  If the cistern gets low in Aug,  there are milk truck drivers that will bring you a load of water pretty cheap.

Here is a Link that a good friend of mine in Rotary sent me for the group.  It is the Manufacture of some of the units that we give out in 3rd world countrys.  It has alot of info about the operation and maintanance of the units.  Hope it's a help. 


  http://www.hydraid.org

There is a quaker group with folks from our meeting doing similar work, with some information available:

http://www.friendlywaterfortheworld.com/

I talked about whether or not people might not be tempted to feed the sand filter to get the bacteria going, i am pretty sure you should not nothing i have read on the e topic suggests anything of the sort, it is just that though it is hard to imagine, water seems to have food in it, it goes stagnante after all. agri rose macaskie.
 

someone mentions the need to keep the sand wet and so use it often rather than when it rains which might not be so often. the riser pipe helps with tha tmaikng sure the water never flows out below the level of the high up tap,  so maybe it would be best to use it to clean the water you were about to use from your cistern or from where ever you could get water instead of just when it rains, to clean the rain water, as it may not rain very often. agri rose macaskie.

  From whatching videos on the problems of getting clean water to places that dont have it in the tap, I have learnt that though boiling the water sounds so easy it is not.
      We in the west type countries who always have gas coming out of our stoves when we want it may feel that boiling is easy but if we had to go for wood and light a fire every time we boiled water we would realise taht it is not so easy and also if everyone is to drink two litres a day that is a lot of water to boil up and always have ready. In deserts the wood you use is a reduction of the plants you have so it must cause you a bit of sorrow using wood. This is the reason it is necessary to find other ways of killing microbes in water.  agri rose macaksie.

The Bio Layer that filters the water and kills the bad stuff does just sort of come naturally,  you dont add it or buy it,  it just grows after about 2 weeks.  That Bio Layer does have to be kept wet to live.  Filtering water from a cistern does sound like a good idea to me.  The only question I would have is how to put the water through the filter?  Pump,  gravity flow or by hand by carring buckets.  The longer the water stays in the filter  [ up to a point at least ]  the better the water will be cleaned.  So running a continuous flow through the filter as it rains would not work the best.  Filtering the water after it has been collected makes more sense to me.  Doug

hey... thank you for providing the information here.

did any of the readers rebuild one of these? has anybody experience with these?


thank you!