Glossary of Water Treatment Terms & Definitions - O

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Ohm

A unit of measure determining the resistance to passage of an electrical current. In a solution, it is related to the electrolyte concentration in the solution.

Operating Pressure

The range of pressure, usually expressed in pounds per square inch, over which a water conditioning device or water system is designed to function. Usually 30-100 psi.

Organic

Having the characteristics of or being derived from plant or animal matter, as opposed to inorganic matter derived from rocks and minerals. Organic matter is characterized by its carbon-hydrogen structure.

Organics ( i.e., Organic Chemicals)

Term used to describe any or all of the compounds with chemical structures based on carbon. Examples are hydrocarbons, wood, sugars, proteins, methane, petroleum-based compounds, solvents, pesticides, herbicides, trihalomethane (THM) and trichloroethylene (TCE).

Osmosis

A process of diffusion of a solvent such as water through a semi-permeable membrane which will transmit the solvent but impede most dissolved substances. The normal flow of solvent is from the dilute solution to the concentrated solution. Osmosis causes the stronger solution to become more diluted and tends to equalize the opposing solutions.

Osmotic Pressure

The pressure and potential energy difference that exists between solutions on either side of a semi-permeable membrane. This pressure is caused by the tendency of water to flow in osmosis. Every 100 ppm (mg/L) of TDS produces about one pound per square inch of osmotic pressure. Osmotic pressure must first be overcome by water pressure in the reverse osmosis process.

Oxalic Acid

Can be used for the removal of iron stains from most washable fabrics. Oxalic acid crystals can be obtained at most drug stores. It is poisonous and a skin irritant, therefore precautions must be used.

Oxidation

A chemical process in which electrons are removed from an atom, ion or compound. The addition of oxygen is a speciform of oxidation. Combustion is an extremely rapid form of oxidation, while the rusting of iron is a slow form. Oxidation never occurs alone but always as a part of the oxidation-reduction (redox) reaction.

Oxidizing Agent

A chemical substance that brings about the oxidation of other substances in chemical oxidation and reduction reactions. Examples of oxidizing agents include oxygen, ozone, chlorine and peroxide.

Oxidizing Filter

A type of filter used to change the valence state of dissolved molecules, making them insoluble and therefore filterable. For example, a filter that oxidizes ferrous iron, manganous manganese, and/or anionic sulfur by use of a catalytic media such as manganese oxide and then filters the oxidized precipitant out of the water.

Ozone

An unstable form of oxygen (03), which can be generated by sending a high voltage electrical discharge through air or regular oxygen. It is a strong oxidizing agent and has been used in water conditioning as a disinfectant. It can be also produced by some types of ultraviolet lamps and during lightning storms.