Re: Can you filter water to get rid of bad bacteria and impurities? How?

Hi Sam,

It would be great if someone could figure out a solution to this problem. Unfortunately, I don't think filtration is the way to go here.

It is certainly possible to remove bacteria using filtration on a small scale. In the laboratory, we can attach small filters to the end of syringes and force water through them. The filters contain tiny pores, smaller than the diameter of a bacterium and so bacteria are trapped in the filter. However, over time the filter becomes clogged up with bacteria, more and more pressure is required to push the syringe and eventually, the filter is unusable. On a larger scale you would have the same problem - the filtration rate would just be too slow to work with big volumes of flood water.

The problem with a flood like the one in New Orleans is that the water is contaminated with all kinds of things and all of these need to be removed in different ways. There are large pieces of debris or particles which are best removed by allowing them to sink to the bottom of a tank. There are bacteria and toxins made by the bacteria which may be best removed using chemical treatments. There are toxic chemicals and materials such as oil, which require specialised physical and chemical treatments to remove. So filtration alone, even if it were possible, would not make the water drinkable.

The real problem in New Orleans is that the floods have destroyed the water treatment plants. All large towns and cities have a water treatment plant which uses a variety of physical, chemical and biological processes like the ones that I mentioned earlier to purify water for the town. Here are some links about water treatment to look at:

A US EPA webpage about drinking water

How Sewer and Septic Systems Work at How Stuff Works.

Water treatment is a really interesting process - a lot of schools arrange visits to a water treatment plant so if yours does, you should definitely go.

Hope this helps with your question,
Neil