Body

Module 1: The Quality of Water

Introduction

Water makes up four-fifths of the earth's surface and about 75% of our total body weight. Without water we could not survive. Thus, the concerns about water purity and safety are high on our list of priorities. In recent years many of our water sources have become polluted by sewage, chemicals, oil spills, etc. A case in point is the recent pollution of the James River due to industrial dumping of the chemical, keypone. In addition, the deterioration of the quality of water in the Chesapeake Bay is of great concern both locally and regionally. In this module, students are asked to perform library and Internet searches on the history and background of the pollution of the waterways in Virginia including the Chesapeake Bay and to catalogue actual and proposed solutions to these pollution problems. Students will then analyze water quality problems from a number of perspectives using mathematical models.

A. Pollution in the Chesapeake Bay & Other Waterways

This section begins with a lecture by a representative of the Chesapeake Bay Foundation, a nonprofit organization whose mission is to clean up the Bay.

1. Give some estimate of the size and scope of the Chesapeake Bay.

2. How polluted is the Chesapeake Bay? What are some of the causes of this pollution?

3. What role does algae play in the quality of the Bay?

4. What effect does the presence of oysters have on the quality of the Bay?

5. What has been the trend over the years relative to the number of oysters in the Bay?

6. Give a brief description of where and how oysters reproduce in and around the Bay.

7. What is the Chesapeake Bay Foundation doing to increase the number of oysters in the Bay?

8. The attached chart provides actual data on the density of oysters (number per square meter at

the bottom) for various rivers that feed the Chesapeake Bay. If certain other factors such as

the fertility and fecundity rates are known for a river, one can project the number of new

oysters that will be produced in the river in a year's time. (See the example that is worked out for the James River.) Develop a spread sheet which projects the number of new oysters in

one year for each of the other rivers on the chart.

9. Make a two year projection based on your results in #8.

10. Which of the factors related to oyster production can be controlled by human efforts?

11. List some of the ethical issues related to water pollution, and describe attempts to resolve

these issues.

B. Water Treatment

This investigation requires a visit to a water treatment plant. One plant is located on 37th Street in Norfolk; another is located on Battlefield Blvd. in Chesapeake. During the visit students should seek answers to the following questions.

1. What, generally is the function of the plant?

2. What sources provide water for the plant?

3. Describe what happens to the water after it enters the plant. (Ask for a diagram.)

4 Describe the purification process in the plant. Include the chemical reactions.

5. How many millions of gallons per day (MGD) does the plant produce? What is the

maximum capacity of the plant?

6. Water leaves the plant in two 36" diameter mains. How fast must the water travel to pump

37 MGD?

7. A large cylindrical storage tank at the plant has a storage capacity of 4 million gallons. The

tank extends 10 feet below ground surface. Estimate the height of the tank and compute the

diameter of the tank. What must be the weight or mass of the water in the tank?

8. How much chlorine is added to the water on the average? (Refer to monthly logsheets .)

9. What are average readings for turbidity, alkalinity, and ph? (Refer to monthly logsheets.)

10. If a 7.0 ph reading is neutral, how close to neutral does the water at the plant come?

11. Using logsheet data, make graphs to find relationships between turbidity, alkalinity, and ph at the plant. What is the correlation between these items over the period of say one month?

12. What impact will the Lake Gaston Pipeline Project have on the plant?

13. What are some of the ethical issues raised in our discussions with the plant manager?

C. Lake Gaston Project

In this investigation students will study the politically charged Lake Gaston Project and the solution that it provides for the Virginia Beach water problem.

1. What are the sources of Tidewater drinking water?

2. Why does the City of Virginia Beach have a problem supplying its residents with water?

3. What is the Lake Gaston Water Supply Project and how would the project remedy Virginia

Beach's water problems?

4. How many MGD does Virginia Beach propose to pump from Lake Gaston?

5. How long will the pipeline be? Will it be built on a straight line from Gaston to Tidewater?

6. How large will the pipeline be in diameter and cross sectional area?

7. How much water will the pipeline hold? What is the weight or mass of all that water?

8. How fast must the water t ravel in the pipeline to supply Virginia Beach's daily need of

approximately 60 MGD?

9. What will be the total cost of the pipeline? How much per mile? How much has been spent

so far?

10. Since Virginia Beach is on the ocean, is desalting of ocean water a viable option?

11. How much would Norfolk's proposed settlement cost Virginia Beach?

12. How much would Virginia Beach's proposed settlement cost? Which is fairer?

13. One argument that has been used to oppose the Lake Gaston Project is as follows: Building

the pipeline would affect the striped bass population of the lake. Striped bass eggs must

settle near the bottom of the lake in order to hatch. If large amounts of water are disturbed in

the lake the increased velocity of the particles in the water would affect the settling velocity of the eggs and interfere with the striped bass harvest. Use data provided by the Virginia

Beach Department of Public Utilities and the Steering Committee for Roanoke River Studies

to prove or disprove the argument. Use graphs and charts as necessary.

D. Laboratory Experiments

The following experiments are designed to give students hands-on, scaled down versions of water quality problems and solutions. The laboratory exercises are supervised by the chemistry instructor.

1. How Clean is Your water?

Many rivers and lakes are polluted. They may contain household waste, sewage,

chemicals, and detergents. Some rivers and streams may contain soil particles which

make the water cloudy and hinder plant growth. In this experiment you will analyze

water samples from different sources and determine how turbid (cloudy) they are, how

much solid material each contains, and the detergent content of each.

2. Water Fit To Drink

In many areas drinking water is obtained from local rivers and lakes. In other cases,

it may be transported over long distances from reservoirs. In any case, the water must

be treated to remove solids and bacteria to make it fit for human consumption

(potable). In this experiment you will investigate the use of aluminum sulfate (alum)

and a sand/gravel filter bed to remove solids and harmful bacteria from water samples.

Final removal of harmful bacteria requires treatment with chlorine.

3. Iodine Treatment

The use of iodine crystals is a popular way of making small quantities of nonpotable

water safe to drink. Crystals placed in a 1 ounce bottle of water will dissolve until the

solution is saturated. After saturation, half of the solution is poured into a quart

container of nonpotable water, and after about an hour, the water usually safe to drink. The half empty 1 ounce bottle is then refilled to be used again in the same way. Suppose the concentration of iodine in the 1 ounce bottle t minutes after the crystals

are introduced can be approximated by the equation

C(t) = 250(1 - e^-t) t > 0

where C(t) is the concentration of iodine in micrograms per milliliter (mg/ml).

(a) Make a graph of C(t) for 0 < t < 5.

(b) How does the concentration change from minute to minute?

(d) What is this maximum?

(e) Can you verify this in the lab?

3. Chemistry of Water Pollution

With the help of the chemistry instructor make a survey of some of the chemical

reactions associated with water pollution and water cleansing. If possible replicate as

some of these reactions in the laboratory. For example, experiments in breakpoint

chlorination (least amount of chlorine required to achieve complete disinfestation of

water samples) are particularly instructive.