NOVELTY - Processing beryllium wastewater comprises after filter pressing preneutralized pulp water, adding biological agent (10-50 g/L, according to the content of beryllium and arsenic in the filtrate); agitating and reacting for 10-40 minutes; adding milk of lime and regulating pH at 9-11; performing hydrolysis reaction for 10-40 minutes; and adding flocculating agent for separating the pulp water when hydrolysis reaction is completed.    USE - The method is for processing beryllium wastewater by biological agent, where beryllium wastewater is generated from the process of resource development, smelting, processing, and utilizing, especially washing water of extraction slag generated from the process of smelting beryllium, i.e. beryllia wastewater, beryllium hydroxide washing water, iron cake washing water, and/or wastewater on the ground of workshop, which contains beryllium, arsenic, lead, and cadmium metal ions (all claimed). It is useful for complex polymetallic beryllium wastewater.    ADVANTAGE - The method processes beryllium wastewater cleanly and efficiently. Each heavy metal ion stably achieves the National Integrated Wastewater Discharge Standard. The method has low cost and simple process flow.    DETAILED DESCRIPTION - Processing beryllium wastewater by biological agent comprises preneutralizing the high-concentration wastewater having beryllium content of greater than 15 mg/L by alkali; regulating pH to 8-9; filter pressing the preneutralized pulp water by sheet frame, where residue is returned to the production system to recover beryllium, and the filtrate enters to the regulating reservoir; adding biological agent (10-50 g/L, according to the content of beryllium and arsenic in the filtrate); agitating and reacting for 10-40 minutes; adding milk of lime and regulating pH at 9-11; performing hydrolysis reaction for 10-40 minutes; and adding flocculating agent for separating the pulp water when hydrolysis reaction is completed, where alkali for preneutralizing comprises lime, hydroxide and oxide of alkali metal and its solution, or carbide slurry, and the flocculating agent is polyacrylamide, polymeric ferric sulfate, or polyaluminum chloride. The preparation of biological agent comprises (A) culturing chemoautotroph flora comprising Thiobacillus ferrooxidans and T. thiooxidans in 9K culture medium, adding 10-150 g iron sulfate heptahydrate (FeSO4.7H2O) per liter, and controlling temperature at 20-40 degrees C in the culturing process and pH at 1.5-2.5; (B) combining the solution obtained from step (A) and ferric salt and/or ferrous salt, based on 10-85 g:100 ml mass volume ratio of ferric salt and/or ferrous salt to the solution at 20-40 degrees C; agitating for 1-7 hours; and obtaining biological agent solution (100-160 g/L), where ferric salt and/or ferrous salt comprise ferrous chloride, ferrous sulfate, ferric sulfate, polymerized ferric sulfate, ferric chloride, ferrous nitrate, ferric nitrate, ferrous acetate, ferric oxalate, ferrous perchlorate, and/or ferric thiosulfate; and (C) performing solid-liquid separation on the biological agent solution; and drying when the solid phase is at 100-200 degrees C, obtaining solid biological agent.