Dissolved oxygen (DO) and pH sensors were added to sequence batch reactor (SBR) to achieve highly efficient and reliable discharge water quality and treatment time. In this study, the fuzzy expert system was used to improve existing DO and pH control unit for effective sewage disposal control. The system utilized settled sludge layer in influent wastewater to maximize denitrificaton rate by controlling DO and pH levels in a tank. By providing adequate solids retention time, elimination of floating materials as well as denitrification and phosphorus removal were achieved in small wastewater treatment system. The system also reduced odor by controlling the production of ammonia in a sewage disposal equipment.