Recently, opinions on the need for revision regarding the nitrogen effluent standard of nitrogen from sewage
treatment plant(STP) are consistently suggested. However, it is axiomatic that if nitrogen effluent standard is
strengthened without a clear basis, it will cause confusion in domestic STP. In this research, nitrogen fraction
was analyzed based on a long-term incubation method, according to STP capacity, and the linked treatment of
industrial wastewater. As a result, NBDDON, which is difficult to treat in STP, ranged from 1.0 to 1.9 mg/L.
larger DON and NBDDON/DON was detected in small STP (under 10,000 m3/d) as opposed to the large
STP. NBDDON/DON in industrial STP was about 0.7 and it was higher than municipal STP. This research
result will be used in the important raw data for revision of nitrogen effluent standard of nitrogen from STP.