Showing posts with label contamination. Show all posts
Showing posts with label contamination. Show all posts

Monday, April 7, 2008

Water 102: Water Distribution


Men, women, and children rush to get water from a well in Ethiopia (photo credit: Andrew Heavens)

Now that we've covered the processes involved in water treatment, the next stage is water distribution.

As stated in the Water 101: What is the Water Problem post, a huge part of the larger "water problem" is the transportation, storage, and distribution of clean water. In developed countries like the U.S, Canada, and most European countries, and urban parts of some developing countries, water is generally treated and distributed the same way. Its generally treated at a treatment plant, then distributed in pipes. The water usually comes disinfected and ready for drinking. People don't need to store the water, because the distribution system keeps the water clean and disinfected until you need it.* Once water comes in contact with contaminated areas or is exposed to the air, it gets contaminated.


Water flows out of a pipe in the UK countryside (photo credit: Martin Anataman)

*This may NOT be true of developing countries. Quite often there are water shortfalls, or the water distribution is so low that even in urban centers, families have their own boreholes that they pump water out of for use. They then regularly boil the water for drinking or order drinking water from wholesale providers.

In most developing countries, particularly in peri-urban, slum, semi-rural, and rural communities, water needs to collected from a central point (either from a tap, tubewell, borehole, river, lake, pond or other open water source), then carried to their homes. This is generally the work of women and children, who walk six miles (9.6 kms) to and from the water collection area. Water is heavy, weighing approximately 1 kg per litre or 8.34 lbs per gallon of water. Often the water collection and storage units are contaminated; if not, the pots or other collection units are open to the air and easily get contaminated. And finally when drinking the water, they dip their hands into the pots to get the water. Essentially, its very easy for water to get contaminated at any point.

In developing countries, people are responsible for the water collection, storage, and decontamination, which is why this is a major problem for them. The risk for illness and health issues resulting from lack of clean water or neck/head/back problems are very high. Therefore, besides availability of water, transportation and decontamination are major issues that need to be addressed when designing technology for developing countries.



L-R: A water truck carrying water into the periurban areas in Kenya (photo credit: Stig Nygaard); A line of colorful pots mark the queue for women and children in line to collect water in India (photo credit: McKay Savage).


Young women carry water back to their homes in Somalia (Copyright: Heather Arney / WaterPartners International)

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...

sources:
[1]: www.assam.org
[2]: www.unicef.org
[3]: http://www.martiinc.com/arsenic.htm
[4]: http://www.lenntech.com/turbidity.htm
[5]: credit: W.Eugene Smith
[6]: credit: William Hartz