| Toxicity | (Environmental Engineering) A U.S. EPA hazardous waste characteristic defined with a rigorous test procedure, the TCLP (for Toxicity Characteristic Leaching Procedure). In the procedure, a waste is extracted for 24 hours with an acetic acid solution. The acid extract is then analyzed for the presence of any of the contaminants listed in the procedure. |
| Trace contaminants | (Environmental Engineering) Contamination found in trace (very low) levels. |
| Trophic level | (Environmental Engineering) A level in the food chain. The first trophic level consists of the primary producers, autotrophs. The second trophic level is vegetarians which consume autotrophic organisms. |
| Troposphere | (Environmental Engineering) The lower atmosphere, from the earth's surface to approximately 12 km. This portion of the earth's atmosphere contains about 95 percent of the atmospheric gases. The temperature gradually declines through this region. |
| Virus | (Environmental Engineering) A submicroscopic genetic constituent which can alternate between two distinct phases. As a virus particle, or virion, it is DNA or RNA enveloped in an organic capsule. As an intracellular virus, it is viral DNA or RNA inserted into the host organisms DNA or RNA. |
| Waste minimization | (Environmental Engineering) The elimination or reduction of a waste prior to its generation. This is accomplished by process changes rather than waste treatment methods. |
| Wastewater | (Environmental Engineering) Consumed or used water from a municipality or industry that contains dissolved and/or suspended matter. |
| Weak acid | (Environmental Engineering) An acid that does not ionize completely under the conditions of interest. Examples include acetic acid, carbonic acid, and hypochlorous acid. See strong acid. |
| Wetland | (Environmental Engineering) Semi-aquatic land, that is land that is either inundated or saturated by water for varying periods of time during each year, and that supports aquatic vegetation which is specifically adapted for saturated soil conditions. |
| Abstraction - | (Software Engineering) (1) the level of technical detail of some representation of software; (2) a cohesive model of data or an algorithmic procedureAction (also called Software engineering action) - |