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Pipes which carry treated drinking water.

Mechanical aeration

Use of mechanical energy to inject air into water to cause a waste stream to absorb oxygen.


Materials that form a barrier to the passage of certain suspended solids or dissolved liquids in filters.


A thin barrier that allows some compounds or liquids to pass through, and troubles others. It is a semi-permeable skin of which the pass-through is determined by size or special nature of the particles. Membranes are commonly used to separate substances.


A device for measuring the quantity and flow rate of water.

Meter optants

Consumers who opt voluntarily to have a meter installed in their property. The Water Industry Act 1999 placed a duty on the appointed water companies to provide a free meter for any domestic consumers who wanted one, where it is practicable and not unreasonably expensive to do so.

Modern equivalent asset values

The cost of replacing all existing assets of whatever vintage by a 'modern equivalent' asset. This value exceeds both the historic cost and the RCV (see jargon section R).

Municipal sewage

Liquid wastes, originating from a community. They may have been composed of domestic wastewaters or industrial discharges.

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