NOVELTY - An organic-wastewater-treatment system consists of an anaerobic-treatment tank (1), a denitrifying tank (2), an aerobic-treatment tank (3), and a denitrifying reactor. The anaerobic-treatment tank carries out anaerobic treatment of organic substance contained in wastewater. The aerobic-treatment tank aerobically treats ammoniacal nitrogen. The denitrifying reactor is a sprinkler system (6), and comprises a carrier-filled portion (8) comprising sulfur-denitrifying bacteria and denitrifying bacteria which denitrify using organic substance.    USE - System is used for treating organic wastewater from foodstuffs factories, excrement wastewater from hoggery, and city sewage, containing proteins, sulfur content, and nitrogen content.    ADVANTAGE - The organic-wastewater-treatment system improves the dissolution efficiency of hydrogen sulfide and denitrifying efficiency.    DETAILED DESCRIPTION - An organic-wastewater-treatment system consists of an anaerobic-treatment tank, a denitrifying tank, an aerobic-treatment tank, and a denitrifying reactor. Sulfide-containing organic wastewater is introduced into the anaerobic-treatment tank which carries out anaerobic treatment of organic substance contained in wastewater. The denitrifying reactor is arranged in the downstream of the anaerobic-treatment tank. The aerobic-treatment tank is arranged in the downstream of the denitrifying tank and produces aerobically-treated water containing nitrite nitrogen and nitrate nitrogen, by aerobically treating ammoniacal nitrogen. The denitrifying reactor is a sprinkler system for water-sprinkling anaerobically-treated water and aerobically-treated water from the upper portion, and a carrier-filled portion arranged at the lower portion of the sprinkler system. The carrier-filled portion comprises sulfur-denitrifying bacteria which denitrify using sulfide, and denitrifying bacteria which denitrify using organic substance in anaerobically-treated water, symbiotically. The denitrifying reactor is connected with the anaerobic-treatment tank so that biogas containing hydrogen sulfide produced in the anaerobic-treatment tank is blown-in into the gaseous phase of the lower portion of the carrier-filled portion of the denitrifying reactor.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the organic-wastewater-treatment system. (Drawing includes non-English language text)    Anaerobic-treatment tank (1)    Denitrifying reactor (2)    Aerobic-treatment tank (3)    Sprinkler system (6)    Carrier-filled portion (8)