Energy and water are used in great quantities during the brewing of beer when wastewaters are eventually released into the soil and water bodies, they pose a serious risk to both human health and the normal functioning of ecosystems. The objective of this study was to evaluate the efficacy of pollutant removal from the full-scale wastewater treatment facility of Dashen Brewery by collecting wastewater samples from the influent and outlet of each treatment unit using a laboratory technique and simulating the biogas digestion process using Aspen Plus. The laboratory analysis result and the process simulation model (PSM) result were the two primary findings of the current investigation. Except for temperature, all of the tested parameters of the raw wastewater exceeded the national discharge limit, according to the results of the laboratory examination. The final effluent from the brewery that was treated had a mean value and a standard deviation of 7.8 ± 0.85 (pH), 23.1 ± 3.1 (T), 232.8 ± 14.5 (EC), 229 ± 2.6 (COD), and 16.7± 2.2 (NH4-N)) which were within national industrial wastewater discharge limits. However, the values of some parameters namely, 91.4 ± 2.7(BOD), 41.1 ± 2.6 (TN), 30.4 ± 2.8 (TP), 11.2+2.2(NO3-N) and 50.9 ± 4.2(TSS) were higher than the limits. The overall pollutant removal efficiency of the treatment plant was 92.4 % (BOD), 89.7 % (COD), 90.6 % (TSS), 33.7 % (TN), 15.6 % (TP), 90.4% (NH3 _N) and 55.6% (NO3 _N). The simulation successfully converged, and the stream result shows that the mole percentage of CH4 is 49.39% while that of CO2 is 32.33%. This value corresponds to 9771.28 Kg/day CH4 production. As can be seen from the above simulation result, a daily production of 18,175.39m^3 of biogas can be obtained from AD of the waste. This value corresponds to an energy value of 109.052MJh (or 392,588.4MJ) the wastewater treatment system at the Dashen brewery was recommended by a study. In order to increase the treatment plant's effectiveness, high control response, and compliance with standard discharge limits established by the Ethiopian Environment Protection Authority for industry effluent (2003), the company should implement some technological, technical, and recycling methods. Keywords: Brewery wastewater, Environmental pollution, Aspen Plus®, Energy Efficiency. Anaerobic digestion; Process simulation model; Model validation;