NOVELTY - Wastewater from fiberboard factory is treated by introducing wastewater input into a filter and a centrifuge, flowing wastewater into a horizontal sedimentation tank, a pre-aeration adjusting tank, an iron aeration tank or a vertical sedimentation tank, and performing dissolved air flotation; pumping water into a turn back anaerobic tank with filtering material while performing nitration; and adding aluminum sulfate solvent into the water, flowing water into an inclined tube sedimentation tank, removing suspending materials, and discharging water after standards are met.    USE - Method for treating wastewater from fiberboard factory.    ADVANTAGE - The wastewater after filtering, centrifuging and deslagging is used for washing wood chips. The method is highly efficient in removal of suspending material, recycles water, saves water consumption and reduces wastewater discharge amount by more than 300 tons per day. The device occupies little space while the operation is simple and the running cost is low. The extruded wood dreg and mud could be sent to power source center to be combusted as energy without secondary pollution. The standard of the wastewater treatment can meet the first grade of the Wastewater Discharge Standard GB8978-1996.    DETAILED DESCRIPTION - Treatment of wastewater from fiberboard factory comprises:    (A) in a pre-treatment system: introducing wastewater input into a filter and a centrifuge, respectively to remove slag, flowing the wastewater into a horizontal sedimentation tank, a pre-aeration adjusting tank, an iron aeration tank or a vertical sedimentation tank, and performing dissolved air flotation on wastewater;    (B) in a biochemical treatment system: pumping the water output from pre-treatment into a turn back anaerobic tank with filtering material and an oxidation tank and while a nitration processing is performed;    (C) in a post-treatment system: adding aluminum sulfate solvent into the water output after biochemical processing to decolor the water in a mixer, flowing the water into an inclined tube sedimentation tank to be deposited, removing suspending materials in water by a filtering tank, and then discharging water after standards are met.