This research article published by Water Practice & Technology, 2020The present study engaged onsite operations and laboratory analysis for Mwanza City Slaughterhouse (MCS) wastewater to improve the efficiency of wastewater treatment of a newly installed facility. The MCS wastewater treatment facility is integrated with various units-biodigester, aeration unit, retention, clarifier, and a constructed wetland. During the initial runs, the MCS facility removed 87.5%, 92.2%, 43%, and 65.4% of effluent biochemical oxygen demand (BOD5), chemical oxygen demand (COD), ammonium, and nitrate, respectively. After conducting effective plant operations for five months, the removal efficiencies of BOD5, COD, ammonium, and nitrate improved to 97.4%, 98.3%, 97.4%, and 97.6%, respectively. In the present study, the unit-by-unit performance values achieved as a result of alterations to the facility’s running conditions are presented. The MCS wastewater treatment facility was found to be energy-positive, as it produced an average of 158.2 m3 biogas per day. This amount of biogas, if converted to electricity, would be sufficient to run the facility operations. Generally, the MCS wastewater treatment facility attained the best performance as per design, achieving the effluent levels recommended by the Tanzania Bureau of Standards (TBS).