Thursday, April 3, 2008

Water 101: Contamination

Little indigenous kids play in a pond just by an oil field in Venezuela. It is highly likely that the water is contaminated with oil and oil drilling chemicals.
source: Raphael Millan

In the previous Water 101 post, we covered what the water problem is - that there ultimately isn't that much potable (drinkable) water available for us. Really, the problems were accessibility (how to get water) and availability (amount of water available).

So how do we solve these??

Well, infrastructure is a major part of it. Infrastructure is the whole piping/plumbing system that gets water out from where the water is to where people are (usually animals and other plant life naturally go to where the water is...its the people that cause problems). So maybe we should improve water infrastructure and that would solve the problem.

Well, only partially...

Because there is the larger issue of contamination. It doesn't matter if we have the piping, if the water being piped is dirty. So let's start with understanding contamination.

How does water get contaminated??

Webster's dictionary defines contamination as "The process of...being made impure or unclean." So water that is made impure or unclean is contaminated water. Water gets contaminated in two ways:

1. Natural Contamination: This means contamination from non-human involvement. The thing is, all life needs water to survive. This includes pests like mosquitoes, and germs like bacteria, viruses and protozoa that are bad for us, who also go and live in the water. They make it impure or unclean for us causing a range of waterborne diseases like diarrhea and dysentery or water-related diseases like malaria, etc . Another way that water gets contaminated naturally is with high mud content (aka turbidity), salts, and minerals that the water picks up when it lands on or travels through the earth. For example, the soils in parts of South Asia and Africa naturally have very high amounts of arsenic and fluoride, which the water picks up when it is traveling through. These high levels of arsenic and fluoride can make people very sick. Or coastlines generally have a high rate of salinity (salt) in the groundwater, which makes it non-potable (drinkable).

Left to Right: man with advanced skeletal fluorosis[1]; girl with dental fluorosis. Both are caused by excess fluoride in drinking water[2]. Woman with acute arsenic poisoning [3]. Water with high mud content (turbidity) [4]

2. Artificial (man-made) Contamination: This type of contamination is primarily human-induced. Dumping chemicals or waste from industries and homes, as well as overdraining the water table can severely contaminate the precious water resources we have. There are far too many examples of this, including the stories highlighted in the award-winning movie, Erin Brockovich. One of the examples that really (in my opinion) brought industrial water poisoning to light was what has been known as the Minamata Tragedy, where mercury poisoning caused a series of mysterious illnesses. Other examples include the Mono Lake's increased salinity, caused by excessive draining of the lake and its feed rivers.

From L-R: Factory dumping in Minamata [5]. A sign we are all too familiar with, one that indicates polluted water [6]

A common mistake people make, particularly in communities with lesser education, is that they think contamination can be seen or tasted. But this is not the case. Most contamination is not visible to the human eye. For example, water with high fluoride, arsenic, bacteria or viruses, for example, can look just like regular purified drinking water. This is because the particles are so small that they can only be seen under a microscope or with testing in a lab. It is also important to note that its the concentration of these (generally measured in ppm or parts per million, as in parts of dirt per million parts of water) that can be lethal. It is generally safe to assume that water you get from an open-water source (like a lake, stream, river or pond) is contaminated. You definitely need to decontaminate these (we'll talk about decontamination in the next post). Groundwater is generally clean. I say generally because if it has been exposed to air or touched contaminated surfaces, or has mineral contamination, then its still not fit to drink.

Next time (and finally), we'll get into decontamination. And then I can show you all the fun technologies I've been storing up...

[5]: credit: W.Eugene Smith
[6]: credit: William Hartz

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