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Water glossary



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Water Glossary - O

  • Offstream use: Water withdrawn or diverted from a ground- or surface-water source for public-water supply, industry, irrigation, livestock, thermoelectric power generation, and other uses. Sometimes called off-channel use or withdrawal.

  • Oligotrophic: Having a low supply of plant nutrients. Compare eutrophic.

  • Oligotrophic lake: Deep, clear lakes with low nutrient supplies. They contain little organic matter and have a high dissolved oxygen level.

  • Once-through cooling water: Water (fresh or saline) that is withdrawn from a river, stream or other water body (manmade or natural), or a well, that is passed through a steam condenser one time, and then returned to the river or stream or other water body some distance from the intake. Once-through cooling water is used to exchange the heat from the steam condensers to the cooler water.

  • Open system: System in which energy and matter are exchanged between the system and its environment, for example, a living organism.

  • Organic: (1) Referring to or derived from living organisms. (2) In chemistry, any compound containing carbon.

  • Organic chemicals: Chemicals containing carbon.

  • Organic matter: Substances of (dead) plant or animal matter, with a carbon-hydrogen structure.

  • Organism: A living thing.

  • Orogeny: Period of mountain-building.

  • Orographic precipitation: Rainfall that occurs as a result of warm, humid air being forced to rise by topographic features such as mountains. Precipitation on the edwards plateau is slightly higher because of the orographic effect of the escarpment and hills.

  • Osmosis: Water molecules passing through membranes naturally, to the side with the highest concentration of dissolved impurities.

  • Other water use: Water used for such purposes as heating, cooling, irrigation (public-supplied only), lake augmentation, and other nonspecific uses. The water can be obtained from a public supply or be self-supplied.

  • Outcrop: Exposed at the surface. The edwards limestone outcrops in its recharge zone.

  • Outfall: The place where a wastewater treatment plant discharges treated water into the environment.

  • Outfall: The place where a wastewater treatment plant discharges treated water into the environment.

  • Outwash: A deposit of sand and gravel formed by streams of meltwater flowing from a glacier.

  • Overflow rate: One of the guidelines for design of the settling tanks and clarifiers in a treatment plant to determine if tanks and clarifiers are used enough.

  • Oxidation: A chemical reaction in which ions are transferring electrons, to increase positive valence.

  • Oxidation pond: A man-made body of water in which waste is consumed by bacteria.

  • Oxidation-reduction potential: The electric potential required to transfer electrons from the oxidant to the reductant, used as a qualitative measure of the state of oxidation in water treatment systems.

  • Oxygen demanding waste: Organic water pollutants that are usually degraded by bacteria if there is sufficient dissolved oxygen (DO) in the water.

  • Oxygen depletion: The reduction of the dissolved oxygen level in a water body.

  • Ozonation: A new technology using a form of oxygen, instead of chemicals, to treat cooling water.

  • Ozone: An unstable oxidizing agent, that consists of three oxygen atoms and can be found in the ozone layer in the atmosphere. It is produced by electrical discharge through oxygen or by specifically designed UV-lamps.

  • Ozone generator: A device that generates ozone by passing a voltage through a chamber that contains oxygen. It is often used as a disinfection system.

Water glossary