VACUUM DISTILLATION: Distillation that occurs at a pressure somewhat below atmospheric pressure. Lowering the pressure also lowers the boiling point of water, thus conserving energy by requiring less heat to bring about distillation.
VALIDATION: Determination upon testing that a representative sample of a water treatment product/model has meet the requirements of a specific standard.
VAPOR: The gaseous form of any substance whose usual form is liquid or solid. Visible particles of moisture suspended in air, such as mist or fog.
VELOCITY: The time measurement of linear motion (flow) in a given direction. For example, water flowing 60 feet in a conduit each minute has a velocity of 60 feet per minute (fpm) or one foot per second ( 1 fps).
VIABLE: capable of living independently and being reproductive.
VIABLE WATER TREATMENT PROCESS: A water or wastewater treatment process capable of accomplishing the desired water quality.
VIRUS: A parasitic infectious microbe, composed almost entirely of protein and nucleic acids, which can cause disease(s) in humans. Viruses can reproduce only within living cells. They are 0.004 to 0.1 micron in size, about 100 times smaller than bacteria.
VOCs: Volatile organic chemicals.
VOLATILE: Capable of becoming vapor at relatively low temperatures.
VOLATILE ORGANIC CHEMICAL (VOCs): Synthetic organic chemicals that turn into vapor at relatively low temperatures.