Keats personifies the Nile first by addressing the river directly in the second person. He does this insistently throughout the poem, calling the Nile "thee" and "thou," terms that were already rather archaic at the beginning of the nineteenth century but that also suggest familiarity.
The poet gives the Nile various human functions. It is a son, a chief, and a nurse. He questions the Nile and endows it with emotion and intention as well as the capacity for experience when he says that the river "tastes" the "pleasant sunrise."
Throughout the poem, Keats contrasts the great river itself with those who observe and comment on it. He asks if the Nile, which is surrounded by desert, is truly fruitful, or if it merely beguiles the traveler into thinking so. This questioning is itself a form of personification, but Keats goes beyond this effect to make the river wiser than the men, who fail to understand it.
Keats, therefore, personifies the Nile in a number of ways but ultimately presents the river as something that has human qualities but goes beyond humanity in some mysterious way. This gives the poem the quality of a prayer, which is increased by the use of thee and thou, forms of the second-person pronoun often reserved for God.