A pilot plant (Q=5 $m^3/d$) study was implemented for small and medium sized personal wastewater treatment plant effluent to evaluate MBR and A/O processes utilizing self-sufficient energy composed of wind and solar energy. The removal efficiencies of BOD, SS, turbidity and color were sufficient for legal water quality standards for gray water. However, those of nitrogen and phosphorus could not meet legal regulations which suggested that further removal of those contaminants were needed for reuse of the treated water. Self-sufficient energy rate was 100 % for the pilot plant due to excessive design capacity. In this research, wind and solar energy system was applied considering geological characteristics, which significantly improved energy self-sufficiency. Substantial improvement on energy self-sufficiency can be obtained by optimized investment and operation at a full scale wastewater treatment plant.