A collapsible liquid storage tank for use in an elongated trailer for selectively carrying solid freight and bulk liquid freight, comprising a first side frame configured for movement between a retracted position against a first trailer side wall for carrying solid freight and a deployed position for carrying liquid freight, a second side frame configured for movement between a retracted position against a second trailer side wall for carrying solid freight and a deployed position for carrying liquid freight, a rear frame positioned between the first and second side frames when the first and second side frames are in the deployed position, a liner having side walls connected to the first and second side frames and the rear frame, a liquid impermeable bladder disposed within the liner, and at least one baffle operatively arranged to be positioned between the first and second side frames.