Recently, the construction of a small size sewage treatment plant is increasing to treat the filthy water which is discharged in the zone of small town at country side instead of big city downtown. The treated water flows again through the small streamlet. So the small streamlet in the small town at country side becomes clean and is made as streamlet of natural state. As one of a small size sewage treatment systems, Sungil Nutrients Removal(SNR) was developed by Sungil corporation and is being used in Gyeongnam, Junlado, Chungchoeng areas. The SNR system is adequate in small size sewage treatment system less than treatment of 300 ton/day. To enlarge of usage of SNR system with more than 300 ton/day, another special measurements are needed like wide area and earth retaining structures to retain the large earth pressure.
In this study, various earth retaining structures design methods are investigated to apply the SNR method in more than 300 ton/day capacity sewage treatment plant. As results of this study, new design techniques are presented to apply the SNR method in large capacity sewage treatment system. L shape earth retaining structures are presented as applicable structures to support earth pressure more than 300 ton/day capacity sewage treatment plant. And also, geotechnical problems are checked to use the large scale SNR system.