Thursday, February 28, 2008

DIY Water Purification Systems


With nearly 2/3rds of the planet being covered by water, you'd think that getting a drink of fresh water would be easy! However, there's less than 5% of fresh drinking water to feed the world who's demand is increasing as populations explode! So, how does one go about purifying water?

And by fresh water we mean:

"Freshwater refers to bodies of water containing low concentrations of dissolved salts and other total dissolved solids. Freshwater is an important renewable resource, necessary for the survival of most terrestrial organisms, and is required by humans for drinking and agriculture, among many other uses. Despite its importance, freshwater continues to be wasted and degraded all over the world. The UN estimates that about 1.2 billion people (18 percent of the world's population) lack access to safe drinking water." - Wikipedia

There are several ways to purify water:

  1. Boiling: Water is heated hot enough and long enough to inactivate or kill micro-organisms that normally live in water at room temperature. Near sea level, a vigorous rolling boil for at least one minute is sufficient. At high altitudes (greater than two kilometers or 5000 feet) three minutes is recommended.[1] In areas where the water is "hard" (that is, containing significant dissolved calcium salts), boiling decomposes the bicarbonate ions, resulting in partial precipitation as calcium carbonate. This is the "fur" that builds up on kettle elements, etc., in hard water areas. With the exception of calcium, boiling does not remove solutes of higher boiling point than water and in fact increases their concentration (due to some water being lost as vapour). Boiling does not leave a residual disinfectant in the water. Therefore, water that has been boiled and then stored for any length of time may have acquired new pathogens.
  2. Carbon filtering: Charcoal, a form of carbon with a high surface area, absorbs many compounds including some toxic compounds. Water passing through activated charcoal is common in household water filters and fish tanks. Household filters for drinking water sometimes contain silver to release silver ions which have an anti-bacterial effect.
  3. Distillation involves boiling the water to produce water vapour. The vapour contacts a cool surface where it condenses as a liquid. Because the solutes are not normally vaporised, they remain in the boiling solution. Even distillation does not completely purify water, because of contaminants with similar boiling points and droplets of unvaporised liquid carried with the steam. However, 99.9% pure water can be obtained by distillation. Distillation does not confer any residual disinfectant and the distillation apparatus may be the ideal place to harbour Legionnaires' disease.
  4. Reverse osmosis: Mechanical pressure is applied to an impure solution to force pure water through a semi-permeable membrane. Reverse osmosis is theoretically the most thorough method of large scale water purification available, although perfect semi-permeable membranes are difficult to create. Unless membranes are well-maintained, algae and other life forms can colonize the membranes.
  5. Ion exchange: Most common ion exchange systems use a zeolite resin bed to replace unwanted Ca2+ and Mg2+ ions with benign (soap friendly) Na+ or K+ ions. This is the common water softener.
  6. Electrodeionization: Water is passed between a positive electrode and a negative electrode. Ion selective membranes allow the positive ions to separate from the water toward the negative electrode and the negative ions toward the positive electrode. High purity deionized water results. The water is usually passed through a reverse osmosis unit first to remove non-ionic organic contaminants.
  7. The use of iron in removing arsenic from water. See Arsenic contamination of groundwater.
  8. Direct contact membrane distillation (DCMD). Applicable to desalination. Heated seawater is passed along the surface of a hydrophobic polymer membrane. Evaporated water passes from the hot side through pores in the membrane into a stream of cold pure water on the other side. The difference in vapor pressure between the hot and cold side helps to push water molecules through.
These are great tried and true methods after you've removed heavy materials from the water as well! However, what if you don't want to go to the trouble of building these devices from scratch?
Grass Roots Castle store provides all you'll need for your fresh water needs. So you're next logical question is how much water does an average house hold need per day? The average human requires at least one gallon of water per day for cooking, cleaning and consumption.

Thank you for your attention and time! Have a great Grass Roots Castle Day!


1 comment:

wsofteners said...

It is that time of year when the weather gets warm enough that you start to enjoy the outdoors more or you head to your lakeside getaway water purification systems canada It’s also an important time of the year to stay hydrated – and what better way to do that than by drinking fresh water.