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Thursday, January 22, 2015

Water Purification, Part 4 - Water Sources

A few weeks ago I was asked to explore urban water sources and its treatment To answer that question, first I need to explore some of the possible water sources and what type of treatment would be best for each. A very technical description of the various types of water found in the ground can be found on the USGS website, but I'll try to make it a bit more understandable. I'll start with the worst and work my way through to the cleanest sources.


Surface Water
Surface water is literally water found exposed on the surface. No digging of a well is required to get to it, which means that surface water is likely to be your first choice as a source of drinking water during an emergency. Surface water is also more likely to be contaminated than other sources because of the fact that it is exposed to animals, air, runoff, and sewage discharge.

Here's an aerial photo-map of the county I live in with the lakes, rivers, streams, and drainage ditches shown in blue. The legend didn't save with the picture, but for about 90% of the county you can't travel more than about a mile without finding water of some sort. For a rough estimate, the left (West) border has squared off bumps that are scaled in one mile increments. I am blessed with an abundance of surface water where I live, but I know that others aren't as lucky.

This photo-map came from an online service (beacon.schneidercorp.com) that provides GIS (Graphical Information Service) data to local county and State agencies. It is free to use and they cover a lot of the central US. There are other sites with similar data for other states. The maps are very detailed and you can select the information presented (roads, waterways, political subdivisions, etc.) 

Here's a resource for finding a similar photo map of an area in your area. Road maps and atlases can often give you a good idea of the waterways in your area, and a topographical map will give you details on lakes, ponds, swamps, rivers, and streams.

Photo my own work and copyrighted
Surface water can be contaminated with just about anything and everything you can imagine. Unless you can see the source of the water (spring, glacier, etc.), you should expect that it is contaminated. Somewhere upstream of you could be a dead beaver or raccoon laying in that crystal-clear mountain stream, or the field next to that lake might have been sprayed with 13 different chemicals in the last year. Your choice of filters must have excellent biological removal, and a charcoal filtration step would be prudent in areas where agriculture and industry are found. A good prefilter followed by chlorine or iodine treatment will take care of most surface water if you don't have a filter for removing the biological contaminants. A solar still (like this one) will take care of most of the contaminants and produce potable water in a stationary situation.
 
Photo my own work and copyrighted
How long you expect to rely on surface water will be a determining factor in the size of the filter you will need. My needs would be a filter that would allow me to travel to a place with safe water, which in my normal daily routine would be no more than 30 miles. Even on foot I can travel that far in 72 hours or less, so a small filter with high efficiency is in my GHB. Once at my bug-out location my water needs are taken care of, so my choice of filters is a lot simpler than some of you may have.

Where you are, and to where you are trying to get, are also important;
  • If you're in a metropolitan area, traveling through one, or sheltering in place in one, the water you find in drainage ditches, mud puddles, and storm sewers is going to be the surface water you'll find. 
  • Runoff from roads will have oil from vehicles, rubber from the tires, trash, salt and sand from de-icing, and roadkill remnants, so the treatment option you choose should be capable of removing all of them. 
  • If you see an oil sheen on the water, it's best to look elsewhere for water if you don't have a reverse osmosis system or an excellent filter system capable of removing petroleum from the water.
  • Water stored in a rain barrel or stock tank should be treated as surface water, since it is open to the air and animals. There are few things worse than getting to the bottom of a rain barrel and finding a dead mouse or squirrel. 
  • Rainwater that has run off of a roof will probably contain some bird droppings, leaves, and anything else that could land on the roof so it should be treated before drinking. 
  • Seawater is a special class of surface water, in that it contains enough dissolved salt to be unfit to drink untreated. Distillation and reverse osmosis (RO) are the only good methods of making seawater drinkable, and there are several units designed for this purpose out there. 
  • Brackish water refers to the water found where fresh water streams mix with seawater and should be treated as seawater. By the time the water in a river makes it to the sea it has picked up all of the run-off and discharges upstream and it will need a very good filter to clean it up.

Groundwater
Groundwater is the water trapped or contained in the soil between the surface and the bedrock of an area. Groundwater sources are recharged by water seeping through the soil and porous rock above it, and the water is filtered in the process:  if water can travel through a few inches of ceramic and come out clean, then a few feet of soil and then a few yards of rock will have the same effect. Ground water recharge takes time, though, which varies with the local weather patterns and the make-up of the geology underfoot. Dirt and rocks are capable of desalinating sea water -- if given enough of the right type of rocks and enough pressure.

Photo my own work and copyrighted
If you see a windmill or irrigation system, you will find a well attached. The old windmills may not be working, but if you see a center pivot irrigation system in the field, it is hooked up to a good well. Irrigation systems are fed by pumps run on electricity or an internal combustion engine (usually with a large fuel tank or propane tank next to the motor).

If you have the time and equipment to dig, drill, or drive a well, then you'll need to know if you have a chance of hitting water. The well-drillers around my area have always kept detailed records of their successes and failures at finding water, and pass that information on to each other. If you need to know how far you'd have to dig or drill to find water, try checking this page. Dowsing is another option, but would be best attempted before an emergency.


Photo my own work and copyrighted
If your water table is close to the surface -- within 20 or 30 feet -- a simple well is easily driven with a “sand point”, some pipe and a sledge hammer. Instructions are available online, and the parts can be ordered or purchased at farm supply or plumbing supply store.

Groundwater comes pre-filtered by the soil that it had to percolate through, so it will be free of most of the biological contaminants unless your well is open enough for animals to enter. You can get by with a slightly less efficient biological filter (or no filter at all) depending on the quality of the source. I grew up drinking water from a well and the only reason we ever wanted to treat it at all was to remove the iron and lime content. The chemical filtration step (carbon or RO) becomes more important with shallow wells, especially in areas where agricultural chemicals are used, there are leaking underground storage tanks, or industrial chemicals have been stored/dumped. In general, the deeper the well is, the cleaner the water will likely be. Sand point wells are commonly used for livestock and irrigation purposes in areas where the water table is high, but drinking it untreated may expose you to chemicals and pollutants because the water doesn't have as much soil to travel through.


Deep Water
Water that is below impermeable bedrock or clay is “deep” water. Usually part of an underground aquifer this water has been where it is for thousands of years, cut off from exposure to the air and any other source of contamination. Drilling through several layers of rock to reach this deep water usually takes professional equipment and several thousand dollars, but will provide a source of clean water for many years. The deeper the well, the harder it will be to draw the water up to the surface. Without electricity for a submersible pump, deep wells need good hand pumps to be useful. Bison Pumps have gotten good reviews, but I have no personal experience with them.

Deep wells will provide water that needs no filtration unless the aquifer itself has been contaminated. This is possible through blown-out oil/natural gas wells, severe earthquakes, and other things that may occur in a major catastrophe.


Trapped or Stored Water
Water that is locked up inside plants or left in pipes/containers is what I call “trapped” water.

Plants filter water by drawing groundwater through pores in their roots and carrying up into the body of the plant. The pores and capillaries inside most plants are small enough to filter out bacteria but not chemicals, and a lot of plants will actually concentrate metals in their flesh. Depending on the metals in question this can be good or bad; magnesium, iron, and calcium are good for your body but lead, arsenic, and mercury would be bad. Plants found in the wild would be safer to use than some random weed growing on top of a landfill or next to a factory building. Know the plants in your area and avoid the poisonous ones.

Cactus plants store water, as do the other succulents, and make a handy source of emergency water. Eating or tapping a cactus is pretty straightforward and has been covered in desert survival instructions for many years.


Foliage (leaves) are another plant source of water. Plants lose water through their leaves in a process known as “transpiration”, where water evaporates from the leaves into the surrounding air. Wrapping a clear, clean plastic bag around a tree branch overnight will provide a little bit of water for drinking. Another method is to place cut plants into a solar still and collect the moisture produced as they dehydrate.

Water trapped in pipes or containers is usually water that has been treated by a municipal plant or came from a well that is no longer under pressure. If used within a reasonable amount of time (a few weeks for most sources) no treatment will be needed. However, once it has sat stagnant for a long while, it will start to absorb materials from the container or pipes that it is sitting in, and any bacteria present has a good chance of reproducing and reaching levels of contamination that may be dangerous.  

Bottled water is usually treated with ozone or run through an RO unit (drinking water vs, purified water) and will last months on the shelf, but it can leach chemicals from the plastic bottle into the water. Toilet tanks (not the bowl!) hold 3 to 5 gallons of water; water heaters hold 30 to 50 gallons of water; and standard ½ inch water pipes contain a gallon of water in about 100 feet of pipe (this chart gives values for other pipe sizes). Since the water is trapped, you'll probably need to open the pipe/container at top (vent) and bottom (drain) to get the water out.


Fresh Water 
Fresh water is captured rainwater, snow melt, or other source of condensation or precipitation. Unless your collection system is contaminated, or the air itself is unsafe, this is the best source of water as it needs no treatment. Ice harvested from a frozen lake or river is clean enough to drink once melted, as is freshly fallen snow.




These are the main sources that I think about when I think of water. I haven't given any brands or suggestions for a specific situation because I am not able to test your water sources and then test the resulting water in a proper manner. I am also not getting paid by the makers of water filters, so I am not going to promote any one brand over the other. Check the specifications, reviews, and the maker's claims and compare more than one brand before you buy. You are going to have to do your own research and figure out what treatment method makes the most sense for your situation. If you have question about specific methods, let me know and I will do what I can to help clarify things for you.

The Fine Print


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