What Happens When You Flush

What Happens When You Flush

Introduction SWOOSH! You hear this sound every time you flush a toilet. But did you ever stop to wonder where everything that you flush down winds up? Getting rid of waste takes more than just pushing the handle on a toilet. In fact, it is often a complex process. That process can stretch over (or under) many miles in your city or town.

Where Does Waste Come From? Where Does It Go? Human waste is called sewage. In most homes, it is created by using the toilet, taking showers, doing the dishes, washing clothes, or doing anything that makes water dirty. The average American turns about 100 gallons (380 L) of water into sewage each day. Factories and restaurants create sewage, too. In time, all this sewage could reach our drinking water, making it unsafe.

More than two billion people around the globe have no flush toilets or sewerage systems. Most of their waste either piles up on the land or runs into lakes and rivers. Millions of people die each year from diseases that come from sewage. Sewage treatment experts are working hard to solve this problem, but it is a huge task. Fortunately, the sewer pipes in our homes don't just empty into our drinking water. Instead, in many cities and towns, all of this dirty water ends up in the local sewerage system. Small sewer pipes join up to form bigger and bigger pipes. Some are so big that humans can walk through them!

Inside the Treatment Plant The sewage moves through this large group of pipes to a sewage treatment plant. Here, the water is cleaned. Organisms that can cause disease and other pollutants are removed. Not all sewage treatment systems are alike. One common type cleans sewage in the following way: STEP 1 A big screen (think of a giant kitchen strainer) removes large items such as rocks, sticks, and garbage. That way, they don't jam the treatment plant's machines.

STEP 2 What is left over after this process is called sludge, which is thick, dirty water. The treatment plant pumps air into the sludge, which helps bacteria grow. These helpful bacteria eat the sludge to break it down. STEP 3 Next, the broken-down sludge is sent to another machine. Here, all of the solid waste settles to the bottom. The water at the top is sent to a filter that cleans it further.