Glossary

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Decantation (sedimentation)

Gravity separation of water suspension solids. Laminar decantation supports a sedimentation rate up to one hundred times higher than classical procedures and reduces soil impregnation considerably.

Denitrification

The second stage in the biological elimination of nitrogen, carried out in particular in sewage plants. Denitrification is the reduction of nitrates (NO3-) into nitrogen gas (N2) by anoxic bacteria (lacking oxygen in its dissolved form).

Desalination

An operation used to transform seawater into vapour without any dissolved impurities by heating it or reducing its pressure.

Desanding

Gravitational separation in wastewater, of gravel, sand, and other materials with a density higher than that of water.

Dioxin

Chemical compound resulting from the combustion of organic matter. 210 types of dioxin exist, 17 of which are considered to be harmful.

Disinfection

Treatment designed to reduce pathogenic activity under a defined threshold. Example: a curing process using medium-pressure ultraviolet lamps.

Distillation

Distillation uses evaporation to separate the impurities from water. The drawback is that it consumes large quantities of thermal energy. This explains why the techniques involved have developed to a greater degree in the gas and oil-producing countries. The advantage of the technique is that in order to evaporate, water does not require pre-processing.

DW (domestic waste)

Waste resulting from household consumption and collected by traditional or selective collection.