De or het ontzouting?

The correct Dutch article is:

de ontzouting

Rule Words ending in -ing: almost always de. See the rule
Meaning (Dutch) het ontzouten

How to use ontzouting

the ontzoutingde ontzouting
this ontzoutingdeze ontzouting
that ontzoutingdie ontzouting
our ontzoutingonze ontzouting
your ontzoutingjouw ontzouting
every ontzoutingelke ontzouting
which ontzouting?welke ontzouting?
a big ontzouting / the big ontzoutingeen grote ontzouting, de grote ontzouting

Meaning, plural, diminutive, pronunciation and translations: WikiWoordenboek (Dutch Wiktionary) (CC BY-SA 4.0). Example sentences: Tatoeba (CC BY 2.0 FR).