| Complexation | (Environmental Engineering) The ionic bonding of one or more central ions or molecules by one or more surrounding ions or molecules. |
| Dump | (Environmental Engineering) An illegal and uncontrolled area where wastes have been placed on or in the ground. See Landfill. |
| 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. |
| Groundwater | (Environmental Engineering) Water which is contained in geologic strata. Also properly written as two words, ground water. |
| Landfill | (Environmental Engineering) A legal and controlled area for the placement of wastes into the ground. |
| Landfilling | (Environmental Engineering) The placement of wastes into the land under controlled conditions to minimize their migration or effect on the surrounding environment. |
| Ligand | (Environmental Engineering) The ion or molecule which surrounds or complexes with the central atom or ion. |
| Saltwater intrusion | (Environmental Engineering) The gradual replacement of freshwater by saltwater in coastal areas where excessive pumping of groundwater occurs. |
| Secured landfill | (Environmental Engineering) A landfill which has containment measures such as liners and a leachate collection system so that materials placed in the landfill will not migrate into the surrounding soil, air and water. |
| System | (Environmental Engineering) An arbitrarily defined area or volume surrounded by a boundary and possessing specific inputs, outputs, and reactions. |