Unfortunately, nowhere in the Bible does Satan ever have a trident. But this is Slashdot... sigh let the Christian bashing begin if it must! :(
True. However, the Book of Revelations does refer to Satan's realm as Hades. The early Christians carried a lot of baggage from ancient Rome and thereby from ancient Greece. The Roman god of the underworld, Pluto (Greek = Hades) was frequently depicted carrying a bident - a two pronged staff. As any reader of the Percy Jackson series knows, the trident is carried by Hades' brother, the god of the sea (Roman name = Neptune, Greek = Poseidon).
Since Pluto/Hades was the god of the underworld, he became associated with Satan in many early Christians' minds, and the Book of Revelations referred to the underworld as Hades. At some point, for reasons unknown to me, some depictions of Pluto/Hades began to carry the trident. I guess it's cooler. Or maybe crueler. Hence the Satan - trident connection.
"Its rider was named Death, and Hades was following close behind him." Revelation 6:8, New International Version, also New American Bible.
"Then death and Hades were thrown into the lake of fire. The lake of fire is the second death." Revelation 20:14, New International Version, also New American Bible.
For another fine example of the early Christians inheriting from the ancient Romans and Greeks, take a look at the 1633 trial of Galileo for heresy for suggesting that his observations prove the Earth revolves around the Sun. The bible never says explicitly that the Sun revolves around the Earth (though the creation story is implicitly terracentric), but the Church, through its tradition of Scholasticism, was at the time still committed to many of the theories of Aristotle who explicitly supported the implicit terracentrism of the bible. Aristotle/Scholasticism won the early rounds, but today Galileo and the scientific method are the heavyweight tag-team champs, and the Catholic church has admitted is error vis-a-vis Galileo.