Water treatment before use — Dies and applications

The previous two dossiers examined the various unit treatments for particulate matter. and dissolved substances . The question now is to see how they can be combined in more or less complex processes, the purpose of which may sometimes be limited to simple clarification and disinfection of the water, while in other cases it will also be necessary to provide for its refinement (elimination of micropollutants and improvement of organoleptic characteristics), the lowering of its hardness by decarbonation with lime or softening on resin, its demineralization on ion exchangers and/or membranes, to mention only the overall treatments ; more specific treatments can be added, such as the removal of certain dissolved gases (O ₂ , N ₂ , CO ₂ , H ₂ S), iron and manganese, ammonium or nitrates, etc.

This dossier describes how unit processes are arranged in treatment chains, and how they can be applied in a variety of industries. It is obviously not possible to deal with the subject exhaustively, given the wide diversity :

• water resources (including seawater and brackish water, where these are readily available and can be used); in some cases, the industrialist may also only need to carry out additional treatment if he connects to the drinking water network; the following is mainly concerned with the treatment of natural fresh water, whether surface or ground; for seawater or brackish water desalination techniques, please refer to ; another type of resource, already considered in the introduction to this "Water" section. , is made up of recycled or reused plant effluent, which sometimes requires highly advanced treatment, as described in ;

• water quality requirements depending on the type of industry and water use within the same plant (cf. ) ;

• the range of treatments and processes available.

We should therefore limit ourselves to the most classic cases, which may include :

• or simple roughing (e.g. sieving, settling only, direct filtration without reagents) for washing, transport or cooling water;

• or clarification and/or refining treatment to obtain industrial water of a quality similar to that of drinking water (e.g. food processing industries, bottled water, paper mills, textile industries);

• or much more advanced treatment than in the previous category,...