Environmental Engineering Glossary

A biological wastewater treatment process using aeration to maintain a suspension of microorganisms that metabolize dissolved organic pollutants.

The process by which molecules adhere to the surface of a solid material such as activated carbon, used in water and air treatment to remove contaminants.

A biological process in which microorganisms break down organic matter in the absence of oxygen, producing biogas (methane and carbon dioxide) and a nutrient-rich residue (digestate).

An underground layer of water-bearing permeable rock, sand, or gravel from which groundwater can be extracted using wells.

The amount of dissolved oxygen required by aerobic microorganisms to decompose organic matter in a water sample over a specified period, typically 5 days at 20 degrees C.

The use of microorganisms or biological processes to degrade, transform, or remove environmental contaminants from soil, water, or air.

A measure of the total oxygen equivalent of organic and oxidizable inorganic matter in water, determined through chemical oxidation with a strong oxidant such as potassium dichromate.

The process of adding chemicals (coagulants) to water to destabilize colloidal particles, allowing them to aggregate into larger clumps (flocs) for removal.

The concentration of molecular oxygen (O2) dissolved in water, critical for the survival of aquatic organisms and a key indicator of water quality.

Treated or untreated wastewater that flows out of a treatment plant, sewer, or industrial outfall into a receiving body of water.

Excessive nutrient enrichment of a water body, typically by nitrogen and phosphorus, leading to algal blooms, oxygen depletion, and ecological degradation.

The gentle mixing process following coagulation that encourages destabilized particles to collide and form larger, settleable aggregates called flocs.

A synthetic membrane liner used in landfills, ponds, and containment systems to prevent the migration of fluids into the surrounding soil and groundwater.

A property of soil or rock that describes the ease with which water can move through pore spaces or fractures, expressed in units of length per time (e.g., m/s).

Water, wastewater, or other liquid flowing into a treatment plant, reservoir, or process unit.

Liquid that has percolated through solid waste in a landfill and extracted dissolved or suspended contaminants, requiring collection and treatment to prevent environmental contamination.

The highest level of a contaminant allowed in drinking water under the Safe Drinking Water Act, set as close to the health goal as feasible using the best available treatment technology.

Water pollution originating from diffuse sources without a single identifiable discharge point, such as agricultural runoff, urban stormwater, and atmospheric deposition.

The use of living plants to remove, degrade, or contain contaminants in soil, sediment, or water.

The process of cleaning up environmental contamination from soil, groundwater, sediment, or surface water to reduce risk to human health and ecosystems.

The planning, design, and implementation of systems to control the quantity and quality of rainwater runoff from developed areas, using infrastructure such as detention basins, bioswales, and permeable pavement.

The Comprehensive Environmental Response, Compensation, and Liability Act, a US federal law enacted in 1980 that authorizes the cleanup of sites contaminated with hazardous substances and establishes liability for responsible parties.

The dry weight of particles trapped by a filter from a known volume of water, expressed in milligrams per liter (mg/L).

A measure of the cloudiness or haziness of water caused by suspended particles. It is measured in nephelometric turbidity units (NTU) and is an important indicator of water treatment effectiveness.

Organic chemicals with high vapor pressures that easily evaporate at room temperature, many of which are toxic or carcinogenic and are common soil and groundwater contaminants.