| Ecosystem | (Environmental Engineering) An organism or group of organisms and their surroundings. The boundary of an ecosystem may be arbitrarily chosen to suit the area of interest or study. |
| Effluent based standards | (Environmental Engineering) Standards which set concentration or mass per time limits on the effluent being discharged to a receiving water. |
| Electrostatic precipitator | (Environmental Engineering) A device which uses an electric field to trap particulate pollutants. |
| Equivalent | (Environmental Engineering) The mass of the compound which will produce one mole of available reacting substance. Thus, for an acid, this would be the mass of acid which will produce one mole of H+, for a base, one mole of OH-. |
| Eucaryotic organisms | (Environmental Engineering) Organisms which possess a nuclear membrane. This includes all known organisms except viruses and bacteria. |
| Facultative | (Environmental Engineering) A group of microorganisms which prefer or preferentially use molecular oxygen when available, but are capable of suing other pathways for energy and synthesis if molecular oxygen is not available. |
| Fermentation | (Environmental Engineering) Energy production without the benefit of oxygen as a terminal electron acceptor, i.e. oxidation in which the net effect is one organic compound oxidizing another. See respiration. |
| Fixed suspended solids | (Environmental Engineering) (FSS) is the matter remaining from the suspended solids analysis which will not burn at 550°C. It represents the non-filterable inorganic residue in a sample. |
| Flocculant settling | (Environmental Engineering) Settling in which particle concentrations are sufficiently high that particle agglomeration occurs. This results in a reduction in the number of particles and an increase in average particle mass. As agglomeration occurs higher settling velocities result. |
| Global warming | (Environmental Engineering) The long-term warming of the plant due to increases in greenhouse gases which trap reflected light preventing it from exiting to space. |