Sunday, November 11, 2012

Sustainable Drinking Water Treatment: Biosand Filter

Something is better than nothing when it comes to treating drinking water. There's probably an asterisk in there that I can't think of right now. The essence of that statement is true though. If you need to get a drink, it is better to use one of many simple treatment techniques to purifiy the water before ingesting it. It can be one or a combination of pretreatment (ie. settling), filtration, and chemical or ultraviolet (UV) disinfection.

Unassisted gravity settling is the simplest requiring nothing but a container and letting water sit still. Filtration requires some medium or filter to pass water through, be it a cloth or sand. And chemical or UV disinfection requires a chemical like chlorine bleach or a UV source like a UV lamp or the sun. Now, go through that list again and pick out the techniques that require advanced technology, electricity, or a supply of chemicals. The answer may be none with the exception being disinfection. We'll go into this in more detail in the future, but an acceptable means of disinfection using UV from only the sun is possible.

As you may guess, none of these simpler methods are perfect. There is a reason that licensed operators and qualified engineers are usually required to design and operate drinking water purification plants. With groundwater that many drink directly, the water is cleaned by passing through many layers of fine sand and/or clay, which removes many contaminants. Even if groundwater isn't perfectly clean, we usually have access to water testing labs that can determine if there are problems - all of which require infrastructure, money, education, technical knowledge, etc.

So, where does that leave the millions, if not billions, of people around the world who do not have access to advanced water treatment?

These are people that usually live in developing countries. Their governments may not have the money to fund large infrastructure projects, and the people do not have the money or know-how about how to clean water, let alone what constitutes clean water. Unfortunately, many of these people literally shit where they eat or drink. Almost everything that residents of developed countries know about cleanliness and sanitation is taught. Education in developing countries is lacking and many don't even go to school. I'm starting to sound like an advertisement for UNICEF, but it's all true.

Way back when, people recognized this problem. And over the years, they have helped to export our know-how to developing countries. There are still limitations though. You can not export a treatment plant to a developing country. That is, you can build and operate one for them, but it would require substantial and ongoing investments. The ultimate goal should be to help residents of those countries become self-sufficient, and doing all the work for them is both uneconomical and not helpful long-term (i.e. what happens when the money or funding gets cut?). We haven't even gotten into piping, billing, and other infrastructure requirements - advanced water treatment requires a steady supply of chemicals, electricity, and knowledge.

Any solution then must be cheap and require few, if any, chemicals and technical knowledge. One simple and effective invention is the biosand filter that was developed by Dr. David H. Manz a few decades ago. The only things that one needs to create such a filter are a container, a few feet of pipe, sand, and a bucket or two. All should be readily available around the world for relatively cheap.