Water treatment before use. Particulate matter

The treatment of boiler and cooling water is the subject of another article, this one and the next two. , [G 1 172] relate only to water directly involved in industrial processes (and possibly general service water when it is prepared in the plant); as the various quality criteria required for process water are detailed elsewhere, we now turn to the means available to achieve these objectives, when the raw material is natural water (recycling and reuse techniques are reviewed in another article). ). Only freshwater is taken into consideration, as seawater is the result of specific desalination techniques using distillation or reverse osmosis.

Whether the resource is surface (river, natural or artificial lake) or groundwater, the raw water it supplies to the user will, in the most general case, have all the following unfavorable characteristics:

• organoleptic criteria: turbidity, color, taste, odor ;

• chemical criteria, corresponding to components :

  • or naturally present in water: mineral salts (e.g. hardness, sulphates, chlorides...), iron, manganese, ammonium, fluorides, arsenic, organic matter (in particular humic substances responsible for color)...,

  • or brought in by pollution: mineral micropollutants (heavy metals, nitrates) or organic pollutants (pesticides, hydrocarbons, phenols, detergents, etc.);

• biological criteria: these are mainly pathogenic germs brought in by fecal pollution, but also organisms whose natural habitat is water (planktonic microalgae or phytoplankton, microinvertebrates or zooplankton, environmental bacteria).

To eliminate or correct all these unfavorable parameters, the water treatment company has a number of tools at its disposal, which must first be reviewed: decanters; flotation devices; beds of granular materials with a filtering, adsorbing and/or neutralizing effect; flocculation or oxidation reactors; ion exchangers; membranes, etc. These tools will be combined in more or less complex processes, depending on the industry in question and the use to which the water is to be put. These tools are combined in more or less complex systems, depending on the industry and water use