CHAPTER 1

INTRODUCTION

 

As our ability to examine the natural and engineered environment becomes more sophisticated, we must necessarily be confronted with more and more complex environmental problems. To properly address these problems, the environmental engineer, especially the water resources engineer, must be familiar with many aspects of chemistry. One of these branches of chemistry, chemical modeling, is important for the intelligent use of chemical treatment processes with water and wastewater. This area of chemistry is also critical for the understanding of natural aquatic systems. Courses in aquatic chemistry or water chemistry are part of most graduate-level environmental engineering curricula. The text by Stumm and Morgan (Aquatic Chemistry) has long been considered the standard reference for this branch of chemistry.

The second area of chemistry that is important to the environmental engineer is environmental analytical chemistry. As with aquatic chemistry, many environmental curricula include a laboratory course on the measurement of pollutants. The importance of chemical analysis to the environmental movement cannot be overemphasized. Since the discovery of widespread pesticide residues, and the publishing of Rachael Carson's Silent Spring, the environmental movement has depended heavily on analytical chemistry. Today, significant resources are devoted to the analysis of water and wastewater samples. Some of the purposes of water quality analyses are outlined below.

 

A. PURPOSE FOR WATER QUALITY ANALYSIS

Data from water quality analyses are used for:

A. Regulatory

1. clean water

a. drinking water

b. natural waters

-fresh water organisms

-wildlife

-marine and estuarine organisms

c. waters for agricultural use

-farm water supplies

-livestock

-irrigation

d. industrial process waters

-textiles

-paper

-chemicals

-iron and steel

-misc.

2. wastewater

a. municipal

b. industrial

-dozens of categories

B. Impact Assessment

1. on human health

a. acute

b. chronic

2. on natural systems

a. fresh water

b. marine

c. terrestrial

C. Process Design and Control

1. chemical additions

2. sizing of units and treatment time

3. needs for supplementary processes

D. Process Development

1. performance

2. optimization

E. Fundamental Environmental Research

 

B. Reasons for studying chemical analysis

Why do environmental engineers need to know about water and wastewater analysis? Arenít most chemical analyses conducted by analytical chemists in commercial laboratories? The answer is yes and no. Most sophisticated chemical analysis requiring advanced instrumental analysis is conducted by analytical chemists or chemical technicians. However, tests intended for process performance are more commonly run by environmental engineers. It is quite common for new engineers of all levels to find themselves conducting their own process testing and optimization. Even those who donít get involved with such field work will find an understanding of analytical methodology of great importance in their professional work.

 

 

C. Some Definitions:

Analytical Method:

A series of steps, or a protocol by which a chemical analysis is conducted.

Analyte:

The target substance of an analytical method; i.e., what you are trying to measure.

Qualitative Analysis:

Determination of the presence or absence of an analyte

Quantitative Analysis:

Determination of the amount of analyte present (usually as a concentration in solution)

Verification:

A process by which one demonstrates that the analytical procedures measure what the analyst says it measures

Interference:

The disruption of a quantitative analysis (resulting in poor accuracy) due to the presence of some interfering chemical substance (interferent), or some unwanted physical or electromagnetic effect.

Interferent:

A chemical substance which causes an interference