Understanding Goals for these lessons:

Dissolved Oxygen:

• What is Dissolved Oxygen (DO)
• Why is it relevant in water quality measurements?
• How oxygen gets in the water
• How it is used up / what things affect its concentration
• The dependence of the solubility of DO on temperature
• The meaning of the terms "saturated", "unsaturated", "supersaturated"
• How DO is measured / the relevance of various DO values

Fecal Coliform:

• What is Fecal Coliform (FC)
• How these bacteria can get in the water
• What health concerns there are with fecal coliform
• How the levels of fecal coliform are measured in water and their significance

Total Hardness: (TH)

• What is "water hardness" in terms of chemical substances
• How Ca and Mg ions get in the water
• Some of the concerns with hard water
• Hard water is not a health hazard
• Some concerns with soft water / what MWRA does to adjust the hardness
• How TH is tested for / the significance of various TH values

Handouts:

• DO Handout
• TH Handout
• FC Handout

Homework:

Lesson 5:

• Read the CBL handout on DO (pages 5.1 - 5.7, including data forms)
• Answer: The owner of a small pond hires you as a consultant to help him solve a problem with the pond. He says that all the fish in the pond are dying and the pond is becoming slightly overgrown; yet he knows that there are no pollutants in the pond. What is happening and what would you advise this person to do?

Lesson 6:

• Read CBL Handout on Fecal Coliform (pages 9.1 - 9.7)
• On the MWRA site, find information on how drinking water is treated for fecal coliform.

Lesson 7:

• Read the CBL handout on Total Hardness (p. 14-1 - 14-5 including forms)
• Which areas of the US have the softest water / which have the hardest water?
• Suppose that you conducted a titration as described in the Total Water Hardness handout, and you used 5.5 ml of titrant to get to the equivalence point. What is the total hardness of this sample?

Lesson 8:

• From the compilation of class data on DO, answer the following questions:

  - Calculate the average DO values for tapwater and Charles River water for each class.

  - Were there significant differences in DO levels in tapwater and Charles River water? How would you explain these?

  - Look at the average Charles River DO values for each class. Do these differ from class to class? How do they differ? Explain why this might be.