Environmental engineering is the application of science and engineering principles to protect and enhance the quality of the environment—air, water, and land resources—to sustain the health of humans and other living organisms. Environmental engineers work on projects to conserve the environment, reduce waste, and clean up sites that are already polluted. In so doing, they have to deal with a variety of pollutants—chemical, biological, thermal, radioactive, and even mechanical. In addition, they may become involved with public education and government policy-setting.
To meet its goals, environmental engineering incorporates elements from a wide range of disciplines, including chemistry, biology, ecology, geology, civil engineering, chemical engineering, mechanical engineering, and public health. Some consider environmental engineering to include the development of sustainable processes.
Development of environmental engineering
Ever since people first recognized that their health and well-being are related to the quality of their environment, they have applied thoughtful principles to attempt to improve environmental quality. For instance, the engineers of ancient Rome constructed aqueducts to combat drought and create a healthful water supply for the Roman metropolis. In the fifteenth century, Bavaria created laws restricting the development and degradation of alpine country that constituted the region's water supply.
Modern environmental engineering began in the nineteenth century, when cities such as London and Paris instituted laws decreeing the construction of sewer systems for the proper collection and disposal of sewage, and facilities to treat drinking water. Consequently, waterborne diseases such as cholera, which were leading causes of death, dropped in incidence and became rarities.
Subsequently, measures to conserve the environment were undertaken. For example, in the early twentieth century, the national park system was created in the United States.
With technological development, various actions intended to benefit societies have had unintended, long-term consequences that have reduced the quality of the environment. One example is the widespread application of DDT (dichloro diphenyl trichloroethane) to control agricultural pests in the years following World War II. The agricultural benefits of using DDT were outstanding, as crop yields increased dramatically and world hunger was substantially reduced. In addition, malaria was controlled better than it had ever been. On the other hand, various species were brought to the verge of extinction due to the impact of DDT on their reproductive cycles—a story told vividly in Rachel Carson's Silent Spring. Consequently, the modern environmental movement began, and the field of environmental engineering was pursued with renewed vigor.
Scope of environmental engineering
There are several divisions in the field of environmental engineering.
Environmental impact assessment and mitigation
This division is a decision-making tool. Engineers and scientists assess the impacts of a proposed project on environmental conditions. They apply scientific and engineering principles to evaluate the project's impacts on:
- the quality of air, water, habitat;
- flora and fauna;
- agricultural capacity;
- traffic; and
- social needs and customs.
They also consider such factors as noise levels and visual (landscape) impacts.
If adverse impacts are expected, they then develop measures to limit or prevent such impacts. For example, to mitigate the filling-in of a section of wetlands during a proposed road development, they may plan for the creation of wetlands in a nearby location.
Water supply and treatment
Engineers and scientists work to secure water supplies for potable and agricultural use. They examine a watershed area and evaluate the water balance in terms of such factors as the availability of water for various needs and the seasonal cycles of water in the watershed. In addition, they develop systems to store, treat, and convey water for various uses. For example, for potable water supplies, water is treated to minimize the risk of diseases and to create a palatable water flavor. Water distribution systems are designed and built to provide adequate water pressure and flow rates to meet various needs, such as domestic use, fire suppression, and irrigation.
Wastewater conveyance and treatment
Most urban and many rural areas no longer discharge human waste directly to the land through outhouse, septic, or honey bucket systems. Rather, such waste is deposited into water and conveyed from households via sewer systems. Engineers and scientists develop systems to carry this waste material away from residential areas and to process it in sewage treatment facilities. In developed countries, substantial resources are applied to the treatment and detoxification of this waste before it is discharged into a river, lake, or ocean system. Developing nations are likewise striving to develop such systems, to improve water quality in their surface waters and reduce the risk of waterborne diseases.
There are numerous wastewater treatment technologies. A wastewater treatment train can consist of several systems:
- A primary clarifier system to remove solid and floating materials.
- A secondary treatment system, consisting of an aeration basin followed by flocculation and sedimentation, or an activated sludge system and a secondary clarifier. This system removes organic material by growing bacteria (activated sludge). The secondary clarifier removes activated sludge from the water.
- A tertiary biological nitrogen removal system and a final disinfection process. This system, although not always included due to costs, is becoming more prevalent. Its purpose is to remove nitrogen and phosphorus and to disinfect the water before discharge to a surface water stream or ocean outfall.
Air quality management
Engineers design manufacturing and combustion processes to reduce air emissions to acceptable levels. For example, devices known as scrubbers, precipitators, and after-burners are utilized to remove particulates, nitrogen oxides, sulfur oxides, and reactive organic gases from vapors, preventing their emission into the atmosphere. This area of work is beginning to overlap with the drive toward energy efficiency and the desire to reduce carbon dioxide and other greenhouse gas emissions from combustion processes. Scientists develop atmospheric dispersion models to evaluate the concentration of a pollutant at a source, or the impact on air quality and smog production from vehicle and flue-gas stack emissions.
Hazardous waste management
Hazardous waste is defined as waste that poses substantial or potential threats to public health or the environment, generally exhibiting one or more of the following characteristics: ignitability, corrosivity, reactivity, and toxicity. Hazardous wastes include:
- Industrial wastes, such as caustic and toxic chemicals used in manufacturing processes
- Agricultural wastes, such as pesticides, herbicides, and excess nitrates and phosphates from fertilizers
- Household wastes, such as paints, flammable solvents, caustic cleaners, batteries, pesticides, drugs, and mercury (from broken thermometers)
- Medical wastes, such as needles, scalpels, glassware, unused drugs, radioactive isotopes, and chemical wastes
- Wastes from illegal drug manufacture, such as various harmful chemicals.
Hazardous wastes are commonly segregated into solid and liquid wastes. Solid hazardous wastes are generally taken to special landfills that are similar to conventional landfills but involve greater precautions to protect groundwater and workers. Liquid hazardous materials require highly specialized liners and treatment for disposal. These wastes are often stored in large outdoor manmade ponds and require extensive monitoring to protect groundwater and safeguard area residents.
Brownfield land management and site remediation
Brownfield lands, or simply "brownfields," are abandoned, idled, or under-used industrial and commercial sites where expansion or redevelopment is complicated by contamination with low levels of hazardous waste or other pollutants. These sites have the potential to be reused once they are cleaned up. Land that is severely contaminated, such as "Superfund" sites in the United States, does not fall under the brownfield classification.
Many contaminated brownfield sites sit idle and unused for decades, because of the cost of cleaning them to safe standards. The redevelopment of brownfield sites has become more common in the first decade of the twenty–first century, as developable land grows less available in highly populated areas, the methods of studying contaminated land become more precise, and techniques used to clean up environmentally distressed properties become more sophisticated and established.
Innovative remedial techniques employed at distressed brownfield properties include:
- Bioremediation - a remedial strategy that uses naturally occurring microbes in soils and groundwater to expedite cleanup.
- In-situ oxidation - a strategy that uses oxygen or oxidizing chemicals to enhance a cleanup.
- Soil vapor extraction - a process in which vapor from the soil phase is extracted and treated, thereby removing contaminants from the soil and groundwater beneath a site.
- Phytoremediation - an approach that utilizes deep-rooted plants to soak up metals in soils. When the plants reach maturity, they are removed and disposed of as hazardous wastes, as the metal contaminants have become part of the plants.
Often, these strategies are used in conjunction with one another, and the brownfield site is prepared for redevelopment.
- Risk assessment
- Environmental policy and regulation development
- Environmental health and safety
- Natural resource management
- Noise pollution
Geographic Information System
The Geographic Information System (GIS) is a useful tool for environmental engineers as well as others. It consists of a computer system for collecting, storing, editing, analyzing, sharing, and displaying geographically-referenced information. GIS technology can be used for many applications, including environmental impact assessment, development planning, and resource management. For example, a GIS might be used to find wetlands that need protection from pollution.
- Engineering geology
- Environmental restoration
- Hydraulic engineering
- Water purification
- Environmental management
All links retrieved January 18, 2008.
- History of sewers
- Aerated Lagoons for Wastewater Treatment
- What happens to all the stuff that goes down the toilet? – (from The Straight Dope)
- Photos of various wastewater treatment plants
- Illustrated explanation of how decentralized wastewater is collected and treated
- Agency for Toxic Substances and Disease Registry
- The EPA's hazardous waste page
- EPA Brownfields Homepage
- The Brownfields Center at Carnegie Mellon University
- Congressional Research Service (CRS) Reports regarding brownfields
- UK Environment Agency – position statement on brownfield land redevelopment
- Bioremediation (Toxic Cleanup) News from Genome News Network
- Bioremediation Discussion Group (BioGroup)
- Phytoremediation Website hosted by the Missouri Botanical Garden
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