Before starting this lesson, you may want to watch the video below entitled What is Engineering.
How is Drinking Water Treated?
The largest cities in the United States get their water from surface water - lakes, rivers and reservoirs. Water taken from any surface source usually has some amount of debris (i.e., sticks, leaves, dirt) in it. It can also contain small amounts of pathogens or contaminants. "Raw water" is sent to a drinking water treatment facility to make it potable. At the drinking water treatment facility, the water flows through many different processes to remove any contaminants.
Point source pollution is the leading cause of water pollution. Point source pollution is pollution that comes from a definite source, such as: direct industrial discharge and dumping, accidents, deep-well injection, leaky landfills, leaking underground storage tanks, abandoned hazardous waste sites, septic tanks, etc. Point source pollution can usually be measured and there is strict government regulations on its discharge (i.e., permits must be obtained from the local government for permission to discharge such pollutants into the environment).
Nonpoint source pollution follows point source pollution in terms of its cause for polluting our waters, but is still a major contributing factor. Nonpoint source pollution is described as water that runs over the ground and picks up — and then carries away — natural and human-made pollutants. This water is then deposited into our lakes, streams, coastal waters and even underground sources of drinking water, resulting in harmful effects on drinking water supplies, recreation and wildlife. Sources for nonpoint source pollution include: agricultural runoff, urban runoff, mining, logging, grazing, etc.
People have been treating water to make it safe to drink for a long time. Originally, people thought water was safe to drink if it was clear, so they worked to remove turbidity. Federal regulation of drinking water in the United States started in the early 1900s, but regulation did not become strict until the Safe Water Drinking Act of 1974. This law underwent changes in 1986 and 1996 and is now governed mostly by the United States Environmental Protection Agency (US EPA).
Today, environmental engineers are concerned about making drinking water safe for people to drink. They design the treatment facilities for drinking water processes, and they are responsible for getting rid of the contaminants and bacteria in untreated water that may make people sick. There are several processes that they use, including: coagulation, in which a powdery chemical, called a coagulant, is added to the water; and flocculation. After clumps or flocs begin to form, the water flows into a large basin so that the big clumps can settle to the bottom, where they are removed. Sedimentation is the settling process that removes most of the big particles from the water, but there may still be some small particles left in the water. To remove these remaining particles, the water flows through a filter. Lastly, engineers in the United States also disinfect the water. Disinfection is often performed by adding chlorine to the water to kill germs. After all these steps, it is now clean enough to drink!
The following video explains what IBM engineers are dong to protect our water supply. You may choose to share this with students to help inform the lesson:
- Mad Science: Making Water Smarter
In addition to designing ways to treat water, environmental engineers are called on when water quality in a drinking water facility changes or the design/machinery is not cleaning the water properly. These engineers figure out how to fix the problem and clean up the contaminated water.
Water engineering is a large and diverse branch of civil and environmental engineering. In one way or another, civil engineers are involved in almost every part of the water cycle – from the time water falls as rain until it is returned to the sea. Water engineers design and help build dams to create water storage reservoirs; use hydropower to generate electricity; and divert water through tunnels, canals and pipelines to provide irrigation, transport water to cities, and supply safe drinking water to homes and industries. To learn more about what civil engineers do, visit the Institution of Civil Engineers.