Flocculants: The First Step to Cleaner Water!
For the flocculation portion of drinking water treatment in Mesa, AZ, aluminum sulfate (alum) is mixed into the water, causing small impurities to stick together and form "flocs."Copyright (top) City of Mesa, AZ, and (bottom) 2004 Microsoft Corporation, One Microsoft Way, Redmond, WA 98052-6399 USA. All rights reserved. http://www.mesaaz.gov/water/water_treatment_process.aspx
Students experience firsthand one of the most common water treatment types in the industry today, flocculants. They learn how the amount of suspended solids in water is measured using the basic properties of matter and light. In addition, they learn about the types of solids that can be found in water and the reasons that some are easier to remove than others. Encompassing the concepts of force and motion, attraction and repulsion of charged particles, and properties of matter, during the associated activity students see scientific concepts they already understand through the eyes of engineers who apply them to the removal of solids from water via chemical flocculants.
Almost a billion people do not have access to clean drinking water. Engineers help solve this problem by using flocculants to clean water before and after it is used in households around the world. Several different flocculants are currently used to clean water, and engineers continue to design more effective and less expensive ways to remove particles from water.
After this lesson, students should be able to:
- Define reflection, absorption and transmission of light, in terms of matter.
- Explain how the properties of light and matter assist in measuring the water turbidity.
- Identify the two main types of suspended solids found in water.
- Define colloids and explain why they are difficult to remove from water based on size and surface charge.
- Describe flocculants and how they work to remove colloids.