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Environmental engineering is the branch of engineering that applies principles from chemistry, biology, hydrology, and civil engineering to protect human health and the natural environment — designing the systems that supply clean water, treat wastewater and drinking water, control air pollution, manage solid and hazardous waste, and remediate contaminated soil and groundwater. It grew directly out of civil engineering’s sanitary-engineering tradition in the late nineteenth and early twentieth centuries, when engineers first connected municipal water treatment to the control of waterborne disease, and it now sits at the intersection of engineering design, environmental science, and public health. Where environmental science is primarily concerned with understanding how natural and human systems interact, environmental engineering is concerned with designing the built systems and interventions that change those interactions for the better — a treatment plant, a landfill liner, an emissions-control system, a remediation strategy.
What environmental engineering actually studies
At its core, environmental engineering asks a recurring set of questions: How much of a given contaminant is present, where is it moving, and how fast? What physical, chemical, or biological process will remove or neutralize it at the scale required? What does that process cost to build, operate, and maintain, and how does it perform under real-world variability rather than laboratory conditions? Answering these questions draws on a shared technical core: mass and energy balances (tracking how much of a substance enters, leaves, and accumulates in a system), reaction kinetics and unit-process design (the engineered steps — coagulation, filtration, disinfection, biological treatment — that make up a treatment train), fluid mechanics and hydrology (how water and contaminants move through natural and engineered systems), and environmental chemistry and microbiology (the reactions and organisms that treatment processes rely on or must control). Environmental engineers apply these principles to design and operate the infrastructure that keeps water, air, and soil safe for human use, and to assess and manage the environmental impact of other engineered systems and industrial activity.
Environmental engineering’s closest relationship is with civil engineering, from which it historically emerged and with which it still shares core coursework in fluid mechanics, hydrology, and structural design for infrastructure like treatment plants and stormwater systems; many environmental engineers train within civil engineering departments, and the two fields are frequently co-located academically. It sits within the broader discipline of engineering as an applied, design-oriented field distinct from environmental science’s more observational and analytical orientation, though the two overlap heavily in practice and in the environmental-science coursework most environmental engineering programs require.
Major subfields within environmental engineering
Environmental engineering is organized around the environmental medium or problem it addresses: water and wastewater engineering designs the treatment trains that produce safe drinking water and treat sewage and industrial wastewater before discharge or reuse — the field’s largest and oldest subfield. Air quality engineering designs and evaluates the control technologies (scrubbers, filters, catalytic systems) and atmospheric dispersion models used to limit and predict pollutant emissions and ambient concentrations. Solid and hazardous waste engineering covers landfill design, waste-to-energy systems, and the handling, treatment, and disposal of hazardous and industrial waste streams. Environmental remediation addresses contaminated soil and groundwater, using physical, chemical, and biological methods (including bioremediation, which draws directly on microbiology) to restore contaminated sites. Water resources engineering overlaps substantially with civil engineering and covers stormwater management, watershed hydrology, and flood control. Industrial ecology and sustainable/green engineering applies life-cycle thinking to industrial processes and products — a subfield that overlaps with industrial engineering‘s systems-and-process-optimization perspective — while environmental impact assessment is the regulatory-facing practice of evaluating a proposed project’s environmental effects before it proceeds.
Who funds environmental engineering research
In the United States, environmental engineering research is funded predominantly by federal agencies rather than private foundations. The National Science Foundation’s Directorate for Engineering is a major funder, supporting environmental engineering research through its programs on energy, water, and resource engineering — work explicitly framed around clean water, resource management, and efficient use of energy and materials. The Environmental Protection Agency’s Office of Research and Development is the agency most directly aligned with the field’s applied and regulatory mission, historically funding extramural environmental engineering and science research (including through its STAR grants program) alongside its own intramural research program. The National Institutes of Health’s National Institute of Environmental Health Sciences (NIEHS) funds research at the intersection of environmental exposures and human health, which increasingly includes engineering approaches to exposure reduction. The Department of Energy funds environmental engineering research tied to subsurface science and the remediation of legacy contaminated sites, and the U.S. Department of Agriculture’s National Institute of Food and Agriculture funds water-quality and agricultural-runoff research relevant to environmental engineers working on nonpoint-source pollution. Among nonprofit funders, the Water Research Foundation is a well-known industry-funded nonprofit supporting applied drinking-water and wastewater research specifically for utilities and the water-treatment sector, distinct from the broader disciplinary funding federal agencies provide.
Typical research methods, tools, and equipment
Environmental engineering research spans bench-scale, pilot-scale, and full-scale work. Laboratory research commonly uses bench-scale and pilot-scale reactors to test treatment processes (coagulation-flocculation jars, membrane filtration rigs, bioreactors) before scaling to full treatment plants, alongside analytical instrumentation — chromatography and mass spectrometry for trace contaminant analysis, spectrophotometry for water quality parameters, and molecular biology tools for characterizing the microbial communities that drive biological treatment and bioremediation. Field work relies on environmental sampling and monitoring equipment (water and air samplers, groundwater monitoring wells) and increasingly on sensor networks for continuous data collection. Modeling is central to the field: fate-and-transport models predict how contaminants move through air, water, and soil; hydrologic and hydraulic models simulate watershed and treatment-system behavior; and life-cycle assessment (LCA) quantifies the full environmental footprint of a treatment process, material, or system from a sustainability-engineering perspective. Geographic information systems (GIS) support watershed analysis and environmental impact assessment, and statistical and computational methods underpin the exposure and risk assessments that connect engineering design decisions to public-health outcomes.
Career and training pathways
Most environmental engineers enter the field with a bachelor’s degree from an ABET-accredited environmental engineering program, or a civil engineering program with an environmental concentration, since the two fields share substantial core coursework. As in civil engineering, professional licensure as a Professional Engineer (PE) — earned via the Fundamentals of Engineering (FE) and PE exams administered by the National Council of Examiners for Engineering and Surveying (NCEES), plus qualifying work experience — is generally required to submit engineering designs to a public authority, and is standard for practicing environmental engineers working on regulated infrastructure. Research-oriented and advanced design roles typically require a master’s or PhD, following the same coursework-plus-thesis (MS) or coursework-plus-dissertation (PhD) structure common across engineering disciplines, often housed within a civil and environmental engineering department. Well-known professional and academic societies in the field include the Association of Environmental Engineering and Science Professors (AEESP), which represents academic researchers and educators in the field; the Environmental & Water Resources Institute (EWRI) of the American Society of Civil Engineers; the Water Environment Federation (WEF), focused on water quality and wastewater; and the American Academy of Environmental Engineers and Scientists (AAEES), which administers the Board Certified Environmental Engineer (BCEE) credential for practitioners.
What is the difference between environmental engineering and environmental science?
Environmental science is primarily an observational and analytical discipline focused on understanding how natural systems and human activity interact, while environmental engineering is a design discipline focused on building the systems — treatment plants, control technologies, remediation strategies — that change those interactions for the better. Many environmental engineering programs require substantial environmental-science coursework, and the two fields work closely together in practice.
What is the difference between environmental engineering and civil engineering?
Environmental engineering grew out of civil engineering and the two remain closely linked, sharing core coursework in fluid mechanics and hydrology, but environmental engineering focuses specifically on water and wastewater treatment, air quality, and waste management and remediation, while civil engineering more broadly covers structures, transportation, and geotechnical work in addition to water resources. Many environmental engineers train within civil engineering departments.
What degree do you need to become an environmental engineer?
A bachelor’s degree from an ABET-accredited environmental engineering (or civil engineering with an environmental focus) program is the standard entry credential, followed by PE licensure for engineers who need to certify designs submitted to a public authority. Research careers typically require a master’s or PhD.
Who funds environmental engineering research?
In the United States, the National Science Foundation’s Directorate for Engineering and the Environmental Protection Agency’s Office of Research and Development are the primary federal funders, with the National Institute of Environmental Health Sciences, the Department of Energy, and the USDA’s National Institute of Food and Agriculture funding related work at the edges of the field, alongside nonprofit funders like the Water Research Foundation for utility-focused applied research.
Related CASRAI resources
Environmental engineering is one of many major scientific and engineering disciplines covered in CASRAI’s overview guide to the branches of science, which maps how it relates to neighboring fields across the natural and applied sciences. For the broader parent discipline, see CASRAI’s guide on what engineering is, and for the closely related field it grew out of, see CASRAI’s guide on what civil engineering is. Bioremediation and water-quality microbiology draw directly on microbiology, and emerging biological approaches to environmental treatment overlap with biotechnology; industrial ecology and sustainable-process design connect environmental engineering to industrial engineering‘s systems-optimization perspective.
