Tag Archives: science water experiment

Cleaning Water Up

As I write the water stories for “The City Water Project”, I keep finding and thinking about new things about water. One is about cleaning water up before it is piped to people’s homes.

My house has a private well. The water appears clear and doesn’t taste like mud. Of course I may not notice the taste after drinking it so many years.

just shaken jar of muddy water
Shaking dirt in water makes a thin mud. The water is thick and dark.

That was the case in St. Louis, Missouri, for many years. Amazingly their water system dates back to 1764! There were so few people then the city used wells and cisterns. By 1800 these were inadequate.

If you haven’t looked on a map, St. Louis is flanked by two large rivers: the Mississippi River and the Missouri River. The first can be a mile across normally at this point. The city needed water. The rivers were available and never went dry. They were also full of mud.

cleaning water up takes more than an hour
After an hour sitting on the table a layer of chopped leaves and other organic matter has coated the surface. A layer of heavy mud has formed on the bottom. The water is still dark with suspended mud.

A simple experiment to show the mud problem is to put a handful of dirt in a quart jar, fill it two thirds with water, cap it tightly and shake vigorously for a minute or so. You may laugh. You may say the result is obvious. The dirt is now suspended in the water.

River water digs out dirt along its route and suspends that mud in the water. It flows along carrying the mud with it.

What happens when the water stops moving? Obvious, you say, the mud will drop out of the water. So set your jar on a counter and wait an hour.

cleaning water up takes more than settling
Even several hours after being set on the table, mud remains suspended in the water. These tiny particles are too light to settle out in a day or more. This was the problem faced by cities trying to use river water as a water source.

Like the city water department, you will find a layer of organic matter, leaves and such, floating on the top. These are easily removed. A layer of mud will be on the bottom of the jar.

The water in between is not clear. Even waiting a few more hours doesn’t clear it.

Cleaning water up takes more than letting the mud settle. St. Louis didn’t bother for seventy years and the populace drank water with a muddy tinge.

Then the 1904 Louisiana Purchase Exposition came along. St. Louis found a way of cleaning water up from even this fine silt. Today the city has clear tap water.