Researcher of this study improved conventional circle secondary settling basin, through the way such as extend of inlet pipe length, introduction of device for inducting uniforming of flow, keeping of height of sludge interface. Also, we compared conventional circle settling basin to improved circle settling basin the water treatment efficiency. Result of research, when SVI is average 117, improvement rate of SS and BOD were 51.0%, 37.0% approximately compared to conventional settling basin. And when SVI is average 178, improvement rate of SS and BOD were 22.7%, 36.0% approximately. Also when SVI is average 196, improvement rate of SS and BOD were 24.7%, 30.3% approximately. When it’s winter, improvement rate of SS, BOD, COD, TN and TP were 20.6%, 17.9%, 13.9%, 13.5%, 12.4% approximately. Therefore, we can be the judge, this improved settling basin can be used as the final settling basin in the waste water treatment plant.

침전지는 수처리 공정에서 중요한 조작 중 하나이며, 침전지내에서는 응집과 침전이 일어남에 따라 입자의 크기분포가 변하는 복잡한 현상이 발생한다. 따라서 침전지의 효율적인 설계나 운영을 위해서는 이러한 현상에 대해 이해해야만 하며, 침전효율의 극대화를 위한 연구가 필요하다. 본 연구에서는 침전지내의 흐름을 모의하기 위하여 범용 CFD 프로그램인 FLUENT를 이용하였으며, 침전효율을 평가하기 위하여 FLUENT에서 제공되는 입자추적기법을 사용하였다. 또한