NOVELTY - Processing riboflavin wastewater comprises adding diluted sulfuric acid to riboflavin wastewater; sending wastewater to multi-effect evaporator; drying concentrated slurry; sending condensed water into combined regulation tank, mixing with domestic sewage, heating, and removing more than 85% chemical oxygen demand (COD) and five-day biochemical oxygen demand (BOD5); absorbing and sending tail gas to anoxic/oxic (A/O) tank, aerating, and oxidizing sulfur ion (S2-) into monomer S; settling, discharging supernatant, filling semisoft filler, adding aerobic sludge, oxidizing and decolorizing.    USE - Method for processing wastewater.    ADVANTAGE - The method effectively separates solid in riboflavin wastewater, reduces sewage treatment difficulty, solves BOD5/COD value of sewage, makes the sewage easy to biochemically degrade, and meets the wastewater emission standard. The solid protein feed is recovered, and the standard wastewater is recovered for preparing materials, fermenting and supplying water, extraction section and/or greening, which further saves water resources. The biogas generated by anaerobic treatment is comprehensively used after collecting, thus saving energy resources and realizing comprehensive use of the resource.    DETAILED DESCRIPTION - Processing riboflavin wastewater comprises:    (A) adding diluted sulfuric acid having concentration of 30-50% to riboflavin wastewater, and regulating pH to 4.5-6.0;    (B) sending the wastewater to multi-effect evaporator, where temperature of condensed water in the evaporator is 25-40 degrees C;    (C) drying the concentrate slurry of wastewater concentrated in the evaporator to obtain protein feed grains;    (D) sending the condensed water to combined regulation tank, uniformly mixing with domestic sewage or other sewage, heating at 35-40 degrees C, pumping to upflow anaerobic sludge blanket (UASB) tank, and removing more than 85% COD and BOD5;    (E) absorbing tail gas generated in the evaporator by water, sending to A/O tank when COD reaches 400 mg/L, supplying water, adding aerobic sludge to the A/O tank, aerating, removing COD and BOD5, oxidizing S2- into monomer S;    (F) settling the wastewater treated by A/O tank in secondary settling tank, sending the precipitate in the sludge storage tank, discharging the precipitated supernatant to contact oxidization tank through decanter, filling semisoft filler to the contact oxidization tank, adding aerobic sludge to form active biological bed, removing COD and ammonia-nitrogen (NH3-N), oxidizing and decolorizing.