Nowadays, water is deteriorating for several reasons, such as an increase in wastewater that flows into rivers and the limitation of water resources. Therefore, we have concentrated our plans on securing water resources by reusing wastewater treatment effluent. In this study the reuse system was organized using a submerged membrane bioreactor (SMBR) consisting of an anoxic, select, and aerobic tank. Our plan to solve the problems mentioned above involved optimizing the operating hydraulic retention time (HRT), which was done by comparing the characteristics of water treatment for several HRTs. Also, the simple and vertical double membrane modules were analyzed to find more effective operating condition in SMBR. The Specific characteristics of the SMBR system were represented as follows. We could know below 10 mg/L of BOD, below 5 mg/L of COD, 0 mg/L of SS without changes of HRT, which was satisfied with the standard of reuse water. Optimized HRT was 2.3 h and by composing the vertical double membrane modules, air flow rate could be reduced by 28.5%, lower than that of the simple membrane module.