Chemistry

Chemical reaction based on an exchange of electrons between the compound to be eliminated and the injected agent (chlorine, ozone, chlorine dioxide, potassium permanganate), the objective being to obtain an oxidised compound that is either more easily eliminated or less or non-toxic. However, certain reactions sometimes generate more troublesome or dangerous oxidised compounds. The position in the process and the choice of reagent is therefore variable and must be studied on a case-by-case basis.

A membrane separation process designed to extract a solvent from a solution, used in seawater desalination.

It consists, by reversing the natural process of osmosis, in applying to a solution in contact with a semi-permeable membrane a pressure higher than the osmotic pressure and collecting the solvent on the other side of the wall.

Overall content of mineral salts expressed in mg/L. The corresponding analysis is the "dry residue".

A membrane that is permeable to a liquid (solvent) and impermeable (or only slightly permeable) to substances dissolved in the liquid, of natural (certain animal and plant tissues) or synthetic (polyamides, cellulose acetate) origin.

Applications: membrane filtration (microfiltration, ultrafiltration, nanofiltration, reverse osmosis)

Shows a strong repulsion to water, repels water.

Showing a strong affinity for water. Attracts, dissolves in or absorbs water.

Insoluble granular substance, generally organic and synthetic, containing acid (cation exchanger) or basic (anion exchanger) radicals in its structure, and capable of permuting, without being altered, the positive or negative ions fixed to these radicals, against ions of the same sign in solution in the liquid with which it is in contact.

The permutation, called ion exchange, makes it possible to modify the ionic composition of the liquid to be treated.

Applications: softening, decarbonation, demineralisation, denitration

Bipolar molecule with the chemical formula H2O, very stable with strong covalent bonds between two hydrogen atoms H and one oxygen atom O, which gives it a moisturising attraction to many natural bodies and compounds.

A substance that dissociates more or less completely in aqueous solution to produce OH- ions. A base is stronger the more OH- ions it produces in water.

Bases react with acids to produce a salt and water.

Some bases: lime Ca(OH)2, soda NaOH, sodium carbonate Na2CO3...

Balance between the sum of cations and the sum of anions in the results of a water analysis, when the contents are expressed in milli-equivalents per litre (mEq/L) or in French degrees (°f).

In an aqueous saline solution, the sum of the cations is equal to the sum of the anions. Depending on the uncertainties of the analyses, a difference of up to 6% between the two sums is accepted.