Water UK

demand management
Measures taken by water companies and others to manage households and non-household demand for water. Measures include leakage management, water efficiency and metering.

depreciation
The accounting measure of the consumption or wearing-out of an asset over its useful life. Depreciation is a key component of price limits. For 2000-05 it accounts for 20% of the average household bill.

desalination
The removal of dissolved salts from water by distillation, reverse osmosis, de-ionization, electrodialysis or freezing.

descriptive consent
A consent under which discharges are controlled by imposing general rather than numerical standards.

discharge consent
A legal document which gives permission to discharge and sets out the terms under which the discharge should be made.

disconnection
Separation of a customer's supply from the public water network.

discretionary investment
The extra investment on behalf of customers undertaken by a company over and above that allowed for by the regulator in setting price limits.

disinfection
The destruction of pathogens by physical or chemical means.

disinfection by-products (DBPs)
The residual substances formed by disinfection.

dissolved air flotation
A process which can be used for grease removal, for concentrating activated sludge, or a pre-treatment stage in physico-chemical methods of treatment.

dissolved oxygen (DO)
Oxygen dissolved in a liquid, the solubility depending on temperature, partial pressure and salinity, expressed in milligrams per litre. Tables giving values for the solubility of oxygen in water have been published in standard methods.

dividends
The payments by a company to its shareholders.

dividend cover
The number of times dividends could be paid out of profits (usually profits after tax and interest).

drought
A prolonged period of dry weather; said to exist if, for at least 15 days, on each day, rainfall has been less than 0.25mm.