Better ways to protect water resources and the environment must be implemented in the papermaking industry to help Canada achieve its strategic target in maintaining a healthy environment and ecosystems. Closing down paper machine whitewater systems is the only way to reach that goal. However, under such conditions, a build-up of dissolved and colloidal substances in whitewater occurs. This results in lower paper quality and paper machine runnability problems. A fluidized bed reactor with modified solid sorbents is proposed to remove contaminants from paper machine whitewater prior to recycling. However, the whitewater fibre content significantly modifies bed expansion creating a major impact on the terminal particle velocity and the Richardson and Zaki expansion coefficient. Fibre flocculation was identified as a key characteristic that must be included in the classical equations describing fluidization. A modification for Newton's terminal velocity law and a new model for the expansion coefficient have been developed.