Nonsense. He didn't need to get that from the Bible - no seafaring society truly believed that the Earth was flat. The evidence to the contrary was right before them.
That's a myth invented to make later societies feel superior to older ones. They might have been wrong about a lot of the natural world, but not about that.
If Columbus had to learn that the Earth was round from the Bible, he was a pretty poor sailor.
Well, there just might be some truth in what you say. Take a look at this excerpt:
The myth that people of the 15th century believed that the earth was flat was popularized by 19th century atheists in order to use science in their war against religion. What better way to discredit religion than to attribute an obviously false idea to religious people!
This myth can be traced directly to two very influential 19th century books: History of the Conflict Between Religion and Science by John William Draper (a physician) published in 1874 and History of the Warfare of Science With Theology in Christendom by Andrew Dickson White (the first president of Cornell University) published in 1896. Both men used the flat-earth myth to help spread their arguments against religion. These books started the false and dangerous ideology that there is a war between science and religion, and that science is the only source of truth. The flat-earth myth did not appear in schoolbooks before 1870, but nearly all textbooks included it after 1880.
The attempt to make Columbus into a hero of the battle between science and religion is particularly ridiculous. Columbus was a deeply committed Christian whose own writings prove that his desire to carry the message of Jesus Christ to faraway lands was the primary motivation of his historic voyage to the New World.
http://www.eagleforum.org/educate/columbus/columbus.shtml