Fundamentals of Environmental Engineering

Danny Reible

• Publisher: CRC Press
• Year: 2017
• ISBN:
  9781351446594
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Environmental Science
• Index: Biological Sciences

The field of environmental engineering is rapidly emerging into a mainstream engineering discipline. For a long time, environmental engineering has suffered from the lack of a well-defined identity. At times, the problems faced by environmental engineers require knowledge in many engineering fields, including chemical, civil, sanitary, and mechanical engineering. Increased demand for undergraduate training in environmental engineering has led to growth in the number of undergraduate programs offered. Fundamentals of Environmental Engineering provides an introductory approach that focuses on the basics of this growing field.
This informative reference provides an introduction to environmental pollutants, basic engineering principles, dimensional analysis, physical chemistry, mass, and energy and component balances. It also explains the applications of these ideas to the understanding of key problems in air, water, and soil pollution.

1	Introduction

1.1 WHAT IS ENVIRONMENTAL ENGINEERING?

Engineering involves the application of fundamental scientific principles to the development and implementation of technologies needed to satisfy human needs. For environmental engineering the body of knowledge whose application defines the discipline is environmental science and the goal of the discipline is satisfying present and future human needs through protection of the environment. Such a broad definition, however, does little to define the actual function of an environmental engineer. Even the core science, environmental science, includes aspects of each of the physical, natural, and life sciences. This has made it difficult to characterize environmental engineering and has led to widely varying views as to its focus and responsibilities.

The environmental engineer is often presumed to focus on technologies for the elimination of environmental pollution. Of growing interest and concern, however, are the broader issues of sustainable development, environmental equity, habitat loss, and biodiversity. The protection of the environment thus involves social, political, economic, and legal issues far beyond the domain of any single scientific or engineering discipline. These issues are broader in scope than environmental engineering, but they are issues about which an environmental engineer should be knowledgeable and are issues which are likely to be a component of the work of the environmental engineer.

This text, however, remains largely directed toward the more narrow issue of the technical basis for assessing and eliminating the effects of pollutants in the environment. The engineering science which underpins this effort represents the fundamental knowledge base required of environmental engineers. Environmental pollution is the contamination of the environment with substances that are potentially injurious to human, plant, and animal life or the quality of that life. The polluting substances may arise naturally, for example, in the eruption of volcanoes, or artificially, through the actions of humankind. Generally, we will reserve the term pollution for substances introduced as a result of human activities, but it is important to recognize that natural sources of pollution exist and, on a global scale, account for the majority of many important pollutants. The term contaminant is sometimes interchangeably used with pollution, but generally we will reserve the term pollutant for a substance that has a demonstrated adverse effect on human or ecological health. A contaminant is a substance that is not a component of the natural or “clean” system, but it may or may not pose a hazard. One task of an environmental engineer is to help differentiate between harmless contaminants and pollutants.

Environmental pollution might be in the form of hazardous chemicals released into the environment from a chemical processing plant, by transportation spills, or during the application of pesticides on an agricultural property. Environmental pollution might also be the result of erosion and sediment-laden runoff to a water body as a result of agricultural, residential, or commercial development. It also might be odor or noise problems associated with an industrial or commercial activity. We will often employ pollutants from industrial facilities as examples of pollution, but environmental pollution and environmental problems are much broader. Regardless of the form of the pollution, Seinfeld (1975) pointed out that it involves three important components.

$\text{Pollutant Release}\Rightarrow \text{Environmental Processes}\Rightarrow \text{Receptors/Effects}$

The most important of these components is the receptors, i.e., plants, animals, and/or people. Pollution only occurs when adverse receptor effects exist, whether it be toxicity, habitat loss, or elimination of an important resource. Pollutant emissions, at the opposite end, are the source of the problem and generally the most convenient element to control. This is especially true of point sources, where the pollutants are released from a single location or facility. This is also true, however, if the pollutant source is distributed in space; for example, nonpoint source emissions such as agricultural runoff. Linking the source to be controlled and the receptors are the mixing and transformation processes that occur in the environment.

The identification, evaluation, and resolution of a particular pollution problem typically evolves in the reverse of the direction implied by the above, that is

1. Identification of an adverse receptor effect.

2. Determination of the substance of substances causing that effect and estimation of the threshold concentration below which the effect is no longer important.

3. Identification of the source of the polluting substance or its precursors.

4. Estimation of the mixing and transformation processes between source and receptor so that the threshold receptor level (the no-effects or acceptable effects level) can be translated into a safe emission level.

5. Control of the source to achieve the safe emission level.

An environmental engineer is the type of engineer that must work with each of these problems and assist in their evaluation and resolution. Although an environmental engineer should be able to contribute to each of these areas, some of these may be better addressed by other professionals. If the adverse receptor effect is a human health problem, for example, physicians and the affected public can generally more effectively identify the problem. Similarly, life scientists are better equipped to identify the causes and effects of environmental pollution on the flora and fauna of a particular ecosystem. An environmental engineer might be asked to help assess the cause of the problem, however, both as to the chemical and its source.

Source control is often thought of as the defining activity of an environmental engineer, but it is also sometimes better addressed by someone other than an environmental engineer. It is often the engineer trained in a core engineering discipline that has the knowledge and experience to identify, design, and implement a control strategy or technology within an industry served by that discipline. If the pollutant source is a chemical production facility requiring, for example, a gas scrubber to reduce emissions of a particular pollutant, it is often a chemical or mechanical engineer that may design and construct the treatment system. It is also a chemical engineer that is likely to have sufficient knowledge about a chemical facility to identify process changes that will lead to minimization or reuse of the waste streams. Similarly, it is probably inappropriate to expect all environmental engineers to develop the detailed design of a drinking water piping system, a rainwater collection system, or a municipal wastewater treatment system, traditional activities of civil or sanitary engineers.

An environmental engineer would, however, be expected to have a greater understanding of the environmental impact of engineering activities than traditionally trained engineers. In addition, the environmental engineer should exhibit a greater understanding of the availability and feasibility of control and waste minimization technologies than an environmental scientist. Thus an environmental engineer serves in an integrating role, meshing traditional engineering activity with environmental concerns. This is depicted in Figure 1.1 where the environmental engineer is seen to hold a central position between the environmental scientist with a traditional focus on the ecosystem and the impacts of development and the industry engineer with a traditional focus within the fenceline of such a development. The greater breadth of the ideal environmental engineer encourages them to see on both sides of the fence. It is from this perspective that the environmental engineer may be best able to resolve environmental issues while balancing all external constraints, whether they be technical, economic, or societal constraints such as moral, social, political, or legal constraints.

FIGURE 1.1 Relationship between an environmental engineer and other disciplines and constraints.

The defining activity of an environmental engineer is thus the application of engineering science to the analysis of environmental processes and effects and the design of control systems designed to minimize adverse effects on those processes. Among the technical functions that fit this definition of an environmental engineer are

• Identifying sources of a pollution problem on the basis of a knowledge of viable migration pathways in the environment

• Evaluation of the fate and transport processes of a pollutant between source and receptor to assess exposure or identify a rate of emission that would achieve desired exposure goals

• Evaluation, design, and implementation of systems designed to remediate contaminated soil, sediments, or water

• Interacting with science disciplines in the identification of a pollution problem and the human or ecological response

• Interacting with other engineering disciplines in the evaluation, design, and implementation of systems designed to control pollutants in industrial facilities

In addition to these technical issues are the legal, societal, political, and economic issues alluded to above. Although these issues are not completely within the control of the environmental engineer, the nature of the issues confronting an environmental engineer are such that a significant fraction of his activity is likely to be associated with addressing these issues. Although not the primary focus of this text, these issues will be included where appropriate.

It is important to recognize that complete elimination of pollution is an unachievable goal. L.J. Thibodeaux (1992) stated the problem succinctly when he stated, “I am, therefore I pollute.” Control can only approach but not achieve 100% efficiency. It thus becomes the task of the engineer to balance the cost of environmental degradation with the cost required to control that degradation. Because these costs are often paid by different segments of the community, they have rarely been considered together. It is also generally much more difficult to identify and assess the costs associated with uncontrolled pollution or environmental degradation. Costs of pollution might include increased medical costs for sensitive people or loss of a quantifiable resource or material. It might also include the less easily quantifiable factors of premature death and reduction in the quality of life or habitat for sensitive species. Especially difficult is establishing these “costs” to future generations. The long-term environmental effects of any activity are difficult to estimate. This information is needed, however, if the goal of producing maximum environmental benefit at least cost is to be realized.

FIGURE 1.2 Cost of pollution vs. cost of control. (From Seinfeld, J.H. (1975) Air Pollution, Physical and Chemical Fundamentals, McGraw-Hill, New York. With permission.)

Typically, most of the pollution from a particular source may be controlled relatively inexpensively. The increasing cost of further control must be balanced against the comparatively small environmental benefit to be realized. There exists, at least in principle, a minimum total cost for any activity as depicted in Figure 1.2. A desirable goal for the environmental engineer is to define that minimum cost. If these total costs were defined in relation to a particular industrial or commercial development it would then be possible, again in principle, to make an informed decision whether to go ahead with the development. For the reasons outlined above and discussed in more detail in Chapter 2, however, this ideal is rarely, if ever, achieved.

1.2 THE ENVIRONMENTAL ENGINEERING PROCESS — MODELING

As indicated above, environmental engineering is largely about evaluating environmental processes and effects and designing or constructing systems to minimize any potential adverse effect of more traditional engineering activities. A key component of this process is modeling. Modeling is used to demonstrate understanding of past system behavior and to project that understanding for the prediction of future behavior or to design appropriate control measures. A model can be conceptual and qualitative, but generally it is not possible to demonstrate understanding of a process and make appropriate decisions influenci...

Table of contents

• Cover
• Title Page
• Copyright Page
• Table of Contents
• Chapter 1 Introduction
• Chapter 2 Environmental Hazards and Their Management
• Chapter 3 Introduction to Environmental Engineering Calculations
• Chapter 4 Physical and Chemical Equilibrium
• Chapter 5 Rate Processes
• Chapter 6 Air Pollution and Its Control
• Chapter 7 Water Pollution and Its Control
• Chapter 8 Soil Pollution and Its Control
• Appendix
• Index