Viktor Schauberger, the Austrian “water wizard”, says natural springs provide the healthiest water, full of vitality. Rain water in undisturbed forests, will seep underground, connect with the aquifers, absorb minerals, rise up, and emerge as clear, cool springs. Water from such springs, collected a little distance away, so that it has a chance to absorb some oxygen from the air, is the healthiest.
Using earth as a water filter is something most people intuitively understand. After all, well water is filtered through the organic matter, soil, gravel and rocks. They are springs, but exposed by digging the well.
In river beds, people collected water, by digging the sand, and getting the water that seeps out. This is cleaner and free from sediments.
One can also get fresh water near the sea shore, by digging the sand. This photo from https://geocene.files.wordpress.com/2012/09/img_3745.jpg.
We normally see only the overland flows in a river. A stream or river flows for a long time after the rains stop, or is perennial, because it is supplied by underground springs. In Tamaraparani river, during our younger days, we could feel the cooler spring water, coming out from the river bed, and mixing with the rest of the river water. A river flows because of that. It doesn’t recharge the groundwater. Also along with the overland flow, there is in some cases massive underground flow of water. This freshwater is sometimes detected in the sea, miles away from the shore.
Drinking water from rivers or dams, that was supplied, to small towns, in olden days, was sent through a sand filter, after initial sedimentation. Now chemicals are used to hasten sedimentation, and water is then heavily chlorinated.
The inspiration for bio-sand filter, came from seeing one model (not a working version), by a couple of higher secondary school girls in an exhibition a few years back. This was the best thing that I saw, among all the exhibits, that day.
The bio-sand filter was developed by Dr. David Manz in the 1990s at the University of Calgary, Canada. He also cofounded CAWST, the Centre for Affordable Water and Sanitation Technology. This is open source, details are found at http://www.cawst.org.
Interestingly it has been the Christian missionaries who have promoted it worldwide. Somehow the charity work by the missionaries either in Africa, Asia, or may island nations, have always had questionable results. One of course, should be grateful, that the likes of Bill Gates, are not promoting this. Giving, without empowering, while enriching oneself, the way Gates does, is not good.
About 300k of the bio-sand filters are in operation. One would assume that lot more people would be using this, since it does clean, and reduce pathogens in water. And in a sense, bring a fresh mountain spring, right inside the house. Sort of.
Drinking water here is either chlorinated corporation water, drawn from dammed rivers. Or purchased 20 liter bottles. The bottled water could come straight from borewells, or could be treated through RO (reverse osmosis), or it could just be corporation water, that is let to stand, to reduce chlorine smell. Most bottled water, one should assume is dubious. Sometimes the water is filled from borewells near agricultural fields with heavy chemical usage, or from places with industrial activity that contaminates groundwater. Or these borewells could be near former creeks, or streams, now straightened, and used to carry sewage. Even corporation drinking water gets contaminated with sewage. Smart cities dump garbage and sewage into straightened, and concrete lined creeks. Where previously people used soak pits to locally handle grey water. Trees and shrubs used up this water, and it got further processed and cleaned up by soil microorganisms. Now with smart city paradigms, cities are made to stink, not for the next few months or years, but for decades.
When we think of infinity, or something that is available in abundance, we think of sand. Today we have “sand smugglers” and “sand mafia”, and rules and laws about “sand mining”. All that “puccafication” of houses, and building several crore new houses, using concrete, by our weepity weepy leaders is heroism, but getting sand for such activity is “smuggling”. Why not let people who like mud houses, and tiled roofs, live the way they think fit, instead of providing pucca concrete houses?
One good thing with all this construction activity, is that, quarry sand is easily available. I needed about one pan, and the guy refused to take money for it. When I insisted, he took 20 rupees. Quarry sand with particles of all sizes is the best for bio-sand filter.
This sand has to be sieved, size 0.7mm and less for the filtration layer, 0.7 to 6mm for separation layer, and 6mm to 12mm for the drainage layer.
I got a handful of small gravel 1 to 2 cms, to add to the drainage layer, since quarry sand had only smaller gravel less than 1 cm.
You have to make sure that the filtration sand is not washed too well. Some fine clay/silt should remain, for biological activity to work.
I’m not sure if I cleaned the sand too much. When put in a glass jar, shaken and left to settle, there was a thin layer of very fine silt.
CAWST model uses a concrete container about a meter high. Some use plastic containers. Recently people have been trying stainless steel containers. But we decided to go for a clay pot. The pot was small, only about 40cm (14 inches) high. The suggested filtration layer depth is 55cm, but with this pot, only about 15cm is possible. These pots are made with a hole about an inch wide to fit a drinking water tap. Since taps are fitted locally, you can find a pot without the tap.
A stainless steel (304 steel) pipe bent into an “S” shape is needed. Should have slightly bent down the top, but it is ok for now. The top of this pipe should be a few centimeters below the top of the pot. Since I was working with tight tolerances, I had only about 5 cms, this is where the “extra” water that is poured remains, gets filtered and drains out through the pipe.
The diffuser is outside (unlike the CAWST model), since we have just a small pot to work with. I took a steel utensil, put holes in it, and put gravel and sand in it. This diffuser makes water drip slowly, without disturbing the top surface of the sand.
I used cement and sand to fix the pipe. Also put a hex nipple at the bottom end, to get a better fit, and make the concrete stick to the pipe for better seal. Normally m-seal (epoxy resin) is used, but this is not recommended for drinking water. The cement has to set for several days. We couldn’t test the pot for leakage, until the cement got set. It seems there is a bit of leakage at the bottom. Next time we have to be a little more careful with pot selection. Pot is a major expense – 450 rupees, about $7. The bent steel pipe cost 300 rupees.
It is easier to get steel pipes here, since they are used, not for drinking water, but for steel railings in houses. All the construction activity makes these items easily available.
The bio-sand filter, as the name implies, uses biological activity of bacteria, to eliminate other harmful bacteria, or viruses. Parasites, worms that infest our intestines, and their eggs are too big to pass through the fine sand.
CAWST defines the biolayer as “The biological layer formed in the top few centimeters of the sand in slow sand filters and biosand filters. The biolayer contains micro- organisms including bacteria, protozoa, algae, and diatoms. It is also called the schmutzdecke. The biolayer helps the filter treat water.”
Now using biology means that we need to feed the organisms. Smart people might try feeding minute quantities of sprouts, greens, medicinal barks, etc. Although CAWST recommends no such thing. The girls had sea shells and charcoal, these might provide additional surface for biological activity, but no organic nutrients. The only way to see if this is good, is to use biology itself to check. May be use the filtered water to sprout grains, see if there is any difference between the filtered water, and un-filtered water (both from same source).
The first cup of water from the filter turned out to be surprisingly clear.
Need to add an activated carbon layer in the diffuser, to remove any pesticides in the water. Coconut shells are available in plenty. Fire up the rocket stove, get the charred shells.
After 30 days or so, when biological activity reaches the maximum, the water should be healthy and live, like the water from mountain springs.