Even though, too automated and mechanized wastewater treatment plants in terms of affordability low operation and management cost, effective in meeting the discharge standards, least nuisance and environment-friendly were installed in the developed nation, the reverse was observed in developing countries particularly in Ethiopia. Many low cost technologies are being developed but the choice of the most appropriate technology depends on a proper evaluation of multi-criteria optimization considering technological, logistic, environmental, financial and institutional factors within a factor y. Therefore, the objective of this study is to evaluate the technology, design and performance of existing wastewater treatment systems and to prepare a scheme of its upgrading, if necessar y . The wastewater generated from Meta Abo brewery factory had high organic abundance; as a result it relies on (micro) biological treatment technology. The design was evaluated based on surface organic loading rate, depth, and geometry. Performance appraisal of the plant has been carried out by comparing the concentrations of pollutants at inlet and outlet of the treatment unit. The samples were analyzed with a descriptive cross-sectional study according to the methods of wastewater quality assessment. The average sewage temperature was ranged 25 – 35 o C and the BOD concentration was 2590 mg/l which was greater than 1000 mg/l and again the COD to BOD ratio was 1.64 which was less than 2.5. The anaerobic ponds should designed with lengths 95 m (2.5x38), width 38 m and depth 4 m in two chambers to achieve around 60% - 70% BO removal efficiency and facultative ponds with lengths 60 m (1.15x52), width 52 m and depth 1.5 m in three chambers to achieve around 70% -80% BO removal efficiency. The actual sizes of Meta Abo anaerobic and facultative ponds were 95 m length, 40 m width and 4 m depth with 67% BO removal efficiency and 60 m length, 50 m width and 1.5 m depth with in three chambers total 75% BO removal efficiency respectively. Both anaerobic and facultative ponds were under the range of the calculated design size. The total performances of the treatment plant at Meta abo brewery factory were not up to the discharge standards specially TSS, nitrogen and phosphorus. In order to achieve these discharge standards I recommend to the factory should had routine preventive maintenance and upgrade the treatment system by constructing a maturation pond. Researchers must continue to discover effective ways to reduce the amount of brewery effluent that is produced annually.