Use of direct object pronoun in “que l'on peut”

Question

I came across the phrase from the title while listening to a French song, the full verse was:

Que l'on peut boire au creux des ruisseaux

Could anyone explain why the phrase in the title uses a direct object pronoun? It seems to have the same meaning of Que on peut, though is the pronoun mandatory here?

Answer 1

It's actually the definite article, as opposed to the direct object, but regardless it has no meaning. It's an optional, formal addition for euphony, to avoid qu'on (which is pronounced like con).