Glossary

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I

Impermeable

Not easily penetrated by water.

Impounding reservoir

The traditional form of upland reservoir produced by damming water courses.

Indicator organisms

Microrganisms, such as coliforms, whose presence is indicative for pollution or for the presence more harmful microrganisms.

Indicator tests

Tests for a specific contaminant, group of contaminants, or constituent which signals the presence of something else.

Indirect discharge

Introduction of pollutants from a non-domestic source into a publicly owned wastewater treatment system. Indirect dischargers can be commercial or industrial facilities whose wastes enter local sewers.

Industrial wastewater

Any wastewater which is discharged from trade or industrial premises, other than domestic wastewater and run-off rainwater.

Industrial water use

Water used for industrial purposes in such industries as steel, chemical, paper and petroleum refining.

Infiltration

Penetration of water into a medium, for instance the soil.

Influent

The stream of water that enters any system or treatment unit.

Infrastructure assets

Mainly underground assets, such as water mains and sewers, also dams and reservoirs that last a long time. A distinction is drawn between the infrastructure and non-infrastructure assets because of the way in which they are managed, operated and maintained by appointed water companies.

Infrastructure charges

Developers pay infrastructure charges to appointed water companies when a new property is connected to either a public water supply or a public sewer. The infrastructure charge provides a contribution to the investment required as a result of the demand that new developments generally place on the local distribution or sewerage network.

Integrated Pollution Prevention and Control (IPPC)

The control of discharges from specified industrial premises, whether to land, air or water.

Ion exchange

The replacement of undesirable ions with a certain charge by desirable ions of the same charge in a solution, by an ion-permeable absorbent.

Irrigation

Applying water or wastewater to land areas to supply the water and nutrient needs of plants.

IUD

Integrated Urban Drainage.

IUDM

Integrated Urban Drainage Management.

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