Laboratory Exercise Five Water Pollution

Ecology and Environmental Quality Laboratory Manual

By Dr. Linda Wallace, modified by Dafeng Hui

Objectives:

1. Learn what parameters are usually measured to determine the quality of a body of water.

2. Learn how to measure these parameters.

3. Determine water quality in several major water sources around the Nashville area.

Introduction

According to the World Health Organization (WHO), portable (drinkable) water will be the most limiting factor to human existence by the turn of the century. Not only are we facing a physical lack of water as heavily populated areas face years of drought, but we are also seeing a decrease in usable water due to pollution.

In the United States we have been concerned with water quality for quite some time as shown by passage of the original Clean Water Act in 1972. This act mandated the reduction of polluting discharges into streams, lakes, and oceans. In addition, certain standards were set whereby the quality of water in a particular place could be judged. These standards applied to a large number of different potential pollutants and to a number of water properties that indicate the biological "health" of that body of water.

Each state has its own structure for regulating the health of its water. In Tennessee, what agency is this?

Also, in Tennessee, we will not be concerned with the same types of pollutions as would, say, New Jersey. Therefore, in this lab exercise, we will deal with the issues of greatest local concern. What do you think those are?

One of the water quality criteria that is of most concern is the amount of oxygen that is dissolved in the water. The dissolved oxygen (DO) is needed by many aquatic organisms to survive since they do not "breath" atmospheric oxygen but use the oxygen in the water for their respiration processes. Many species of bacteria require oxygen to help break down organic material that gets in the water. If this level is too low, then organic matter is either not broken down or acted upon by anaerobic bacteria that do not require oxygen. When these organisms are active, hydrogen sulfide ("rotten-egg gas") is produced. When oxygen levels drop so low that these are the only bacteria active, very few other organisms can survive. Thus, DO is a good indicator of biological health of a water body.

In addition, DO is a good indicator of how much organic materials is in the water. If a very high amount of organic matter is added to a water body, then the bacteria will actually start to use up oxygen when they break down these organics. Low DO may indicate that a substantial amount of organic pollution in the water. However, some water bodies will have naturally low DO levels due to their temperature (warm water holds less oxygen than cool), acidity (basic water holds less), or turbulence (calm water has less oxygen mixed into it).

Another natural occurrence that can cause a drop in DO is the death of aquatic plants (algae) following a rapid growth (bloom). After a bloom, bacteria decompose the dead algal mass and thus deplete oxygen. Algal blooms can be caused by excesses of fertilizing nutrients such as nitrate, nitrite, and ammonium and phosphorus reaching the water. Therefore, excess amounts of these nutrients are considered to be pollutants.

Changes in the acidity of water (pH) also can alter DO as well as being directly devastating to aquatic organisms. Other chemicals which may be directly harmful to organisms using the water include chloride, a byproduct of oil exploration; nitrate, a byproduct of fertilizer use or sewage presence.

In this laboratory we will measure the properties of water described above in water samples taken from around the Nashville area.

Sampling

The water samples to be measured will be from the following locations.

Cumberland River near TSU

Tap water in TSU

Harpeth River around Bellevue

Tap water from Bellevue area

You need to make predictions concerning the levels of DO, pH, nitrate, ammonium, phosphate, and chlorine in each of the above sites. You may state which site you think will have the highest, next highest, etc.

Your group will be assigned a water sample from the above list of sample possibilities. After running your analysis and putting the results on the board, the entire laboratory will try to guess which sample came from which location.

Laboratory Activity

No eating, drinking or wearing of contact lenses will be allowed!. Carefully wash your hands after completion of the exercise. Take care not touch your face or eyes without first washing your hands!

We will use a Ph meter and a Hach (R) Water Chemistry Kit to analyze water quality today. Copies of the directions for use of the Hach Kit for each test will be taped onto the lab bench at stations in the laboratory. Follow these carefully for analysis of DO, nitrate-N, ammonia-N, and chlorine. You may also download the instructions from the lab website.

pH: measure 5 ml of water sample into the plastic beaker. Dip the bottom of pH meter into the water and wait until the reading is stable. Record the pH level.

Each group will work on two water samples and measure pH, DO, nitrate-N, ammonia-N, phosphate, and chlorine concentrations.

You will need to write a laboratory report of this exercise.