A characteristic of natural water due to presence of dissolved calcium and magnesium. Water hardness is responsible for most scale formation in pipes and water heaters and forms insoluble “curd” when it reacts with soaps. Hardness is usually expressed in grains per gallon (gpg), parts per million (ppm) or milligrams per liter (mg/l), all as calcium carbonate equivalent.

Water that contains a great number of positive ions. The hardness is determined by the number of calcium and magnesium atoms present. Soap usually dissolves badly in hard water.

A component that is utilized to remove heat from or ad heat to a liquid.

Metals that have a density of 5.0 or higher and a high elemental weight. Most are toxic to humans, even in low concentrations.

Water in which all the hydrogen atoms have been replaced by deuterium.

A way of calculating the solubility of a gas in a liquid, based on temperature and partial pressure, by means of constants.

A pond or reservoir, usually made of earth, built to store polluted runoff.

A water system that supplies piped water to a single residence.

The addition of water vapour to air.

The rate at which water can move through a permeable medium.

In general, the direction of groundwater flow due to changes in the depth of the water table.

Organic compounds that are built of carbon and hydrogen atoms and are often used in petroleum industries.

The use of water in the generation of electricity at plants where the turbine generators are driven by falling water.

A gas emitted during organic decomposition by a select group of bacteria, which strongly smells like rotten eggs.

The science of chemistry and movement of groundwater.

A chart that measures the amount of water flowing past a point as a function of time.

The decomposition of organic compounds by interaction with water.

The natural cycle of water passing through the environment, including evaporation, condensation, retention and run-off.

Having an affinity for water.

Having an aversion for water.

Region that includes all the earth’s liquid water, frozen water, floating ice, frozen upper layer of soil, and the small amounts of water vapour in the atmosphere.

An anion that forms products such as calcium and sodium hypo chlorite. These products are often used for disinfection and bleaching.

Waters with dissolved oxygen concentrations of less than 2 mg/L, the level generally accepted as the minimum required for life and reproduction of aquatic organisms.