Water Treatment: How Can We
Module written by Susan E. Kegley, Doug
Session 1: How can we purify our water?
Dissolved substances in natural waters and their sources; concentration units; bar diagrams.
Exploration 1A: The Storyline
Exploration 1B: What substances do you typically find in natural waters?
Exploration 1C: How do dissolved substances get into a water supply?
Exploration 1D: How can we obtain a quantitative profile of the ionic constituents in a water supply?
Session 2: How do you determine how much of a constituent
is in a water supply?
Analytical methods for fluoride (ion-selective electrode); water hardness (EDTA titration); iron (colorimetric method); total alkalinity (acid-base titration); total dissolved solids (conductimetric or gravimetric).
Exploration 2A: The Storyline
Exploration 2B: How do you determine how much fluoride is in a water supply?
Exploration 2C: How do you determine how much calcium and magnesium is in a water supply?
Exploration 2D: How do you determine how much iron is in a water supply"
Exploration 2E: How do you determine the total alkalinity in a water supply?
Exploration 2F: How do you determine the concentration of Total Dissolved Solids in a water supply?
Session 3: Why do substances dissolve in water?
Polarity; solubility of organic and inorganic constituents in water; thermodynamics of the dissolution process.
Exploration 3A: The Storyline
Exploration 3B: What do we mean by the word "dissolve"?
Exploration 3C: What characteristics of a substance affect its solubility in water?
Session 4: How can we best describe the extent of a chemical
Introduction to equilibrium; dynamic nature of equilibrium; equilibrium expressions and calculations; the reaction quotient, Q; solubility product constant, Ksp; and the relationship of the equilibrium constant to free energy.
Exploration 4A: The Storyline
Exploration 4B: What is equilibrium?
Exploration 4C: What does a chemical system at equilibrium look like at the microscopic level?
Exploration 4D: How can equilibrium reactions be described mathematically?
Exploration 4E: How can we use the equilibrium expression to predict equilibrium concentrations?
Exploration 4F: How can you tell whether a reaction has reached equilibrium?
Exploration 4G: How is free energy related to the extent of a reaction?
Session 5: How can we remove contaminants from a water
Le Chatelier's principle and the effects of concentration, temperature, and pressure on the position of an equilibrium; common ion effect.
Exploration 5A: The Storyline
Exploration 5B: How can we drive an equilibrium reaction to one side?
Exploration 5C: Which precipitating reagent will remove the most contaminant?
Exploration 5D: How much precipitating reagent is required for effective water treatment?
Session 6: What procedures can you design to remove contaminants
from a water supply?
Applying the principles of equilibrium and precipitation to remove contaminants from a water sample.
Exploration 6A: The Storyline
Exploration 6B: How can excess fluoride be removed from a water supply?
Exploration 6C: How can excess water hardness be removed from a water supply?
Exploration 6D: How can excess iron be removed from a water supply?
Session 7: What are acids and bases?
Definitions of acids and bases and their relative strengths; the pH scale; calculations involving strong and weak acids and bases; relationship of acid strength to structure and composition of the acid; thermodynamics of acid-base reactions.
Exploration 7A: The Storyline
Exploration 7B: How are acid and base strengths correlated to the extent of the acid-base reaction?
Exploration 7C: How can we best quantify acid and base concentrations?
Exploration 7D: How do you determine equilibrium concentrations of strong and weak acids and bases?
Exploration 7E: How is acid strength related to the structure and composition of the acid?
Session 8: What is the role of acids and bases in water
Effects of pH on solubility; neutralization reactions; analytical method for measuring pH.
Exploration 8A: The Storyline
Exploration 8B: How can we selectively remove ions from solution?
Exploration 8C: How do you measure the pH of a water supply?
Exploration 8D: How do you change the pH of a water supply?
Session 9: What are your results?
Project 1: Poster Presentation
Project 2: Scientific Report
Project 3: Community Education
Copyright © 2004 by the trustees of Beloit College and the Regents of the University of California. This Module has been developed under the direction of the ChemLinks Coalition, headed by Beloit College, and the ModularChem Consortium, headed by the University of California at Berkeley. This material is based upon work supported by the National Science Foundation grants No. DUE-9455918 and DUE-9455924. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation, Beloit College, or the Regents of the University of California.
Published through exclusive license with W. W. Norton.
Water Treatment: How Can We Make Our Water Safe to Drink? ISBN 0-393-92434-3
Water Treatment | ChemConnections