gender question: Spanish

So I get (or at least I thought I did) how agua is masculine but takes feminine adjectives, and how it's el agua, yet agua fría, where the final letter in fría "matches" the final letter in agua, not the gender. Makes sense.

But here's where I'm tripped up. Can someone explain why in this article from today's El Mercurio (www.elmercurio.cl) about water desalination plants, potabilizarla is with la and not lo at the end?

1860: año en que se prueba en el norte chileno el primer sistema para sacarle la sal al agua de mar y potabilizarla.

It makes it sound like they're trying to make the salt potable. Any thoughts? Thanks in advance


(here's the whole article: http://diario.elmercurio.com/2008/11/11/nacional/nacional/noticias/D59BB703-0D66-4204-AA9F-045033DBA8DC.htm?id=D59BB703-0D66-4204-AA9F-045033DBA8DC )