FE Environmental Glossary
Key terms and definitions for the Environmental Engineering exam.
BOD (Biochemical Oxygen Demand)
The amount of dissolved oxygen consumed by microorganisms while decomposing organic matter in water over a specified period, typically 5 days at 20 degrees C. A measure of organic pollution.
COD (Chemical Oxygen Demand)
The amount of oxygen required to chemically oxidize all organic and inorganic matter in a water sample using a strong chemical oxidant. Always equal to or greater than BOD.
Turbidity
A measure of water cloudiness caused by suspended particles. Measured in Nephelometric Turbidity Units (NTU) using the scattering of light. Drinking water standards require less than 1 NTU.
Sedimentation
The process of settling suspended particles from water by gravity. Used in both water and wastewater treatment. Design is based on overflow rate (surface loading rate) and detention time.
Activated Sludge
A biological wastewater treatment process that uses aeration to maintain a suspension of microorganisms that consume organic matter. The mixed liquor is separated in a secondary clarifier.
Dissolved Oxygen
The concentration of oxygen gas dissolved in water. Critical for aquatic life and wastewater treatment processes. Saturation depends on temperature, pressure, and salinity.
Coagulation
A chemical treatment process that destabilizes colloidal particles in water by neutralizing their surface charges, typically using alum or ferric chloride. Precedes flocculation in water treatment.
Flocculation
A gentle mixing process that promotes the aggregation of destabilized particles into larger flocs that can be removed by sedimentation or filtration. Follows coagulation in water treatment.
pH
The negative logarithm (base 10) of the hydrogen ion concentration in a solution. Ranges from 0 to 14, with 7 being neutral. Controls chemical reactions and biological processes in water.
Darcy Law
Describes groundwater flow through porous media. The volumetric flow rate is proportional to the hydraulic conductivity, cross-sectional area, and hydraulic gradient.
Leachate
Liquid that has percolated through solid waste in a landfill and contains dissolved and suspended contaminants. Must be collected and treated to prevent groundwater contamination.
Nitrification
The biological oxidation of ammonia to nitrite and then to nitrate by autotrophic bacteria (Nitrosomonas and Nitrobacter). An important step in wastewater treatment for nitrogen removal.
Denitrification
The biological reduction of nitrate to nitrogen gas by heterotrophic bacteria under anoxic conditions. Requires a carbon source and removes nitrogen from wastewater.
Hydraulic Retention Time
The average time that water or wastewater remains in a treatment reactor. Calculated as the reactor volume divided by the flow rate. A key design parameter for treatment processes.
Chlorination
The addition of chlorine or chlorine compounds to water for disinfection. Free chlorine (HOCl and OCl-) is the active disinfectant. Contact time and residual concentration determine effectiveness.
Total Suspended Solids
The dry weight of particles trapped by a filter from a water sample. A standard measure of water quality in both drinking water and wastewater treatment.
Eutrophication
Excessive nutrient enrichment of a water body, primarily by nitrogen and phosphorus, causing algal blooms, oxygen depletion, and degradation of aquatic ecosystems.