A laboratory investigation was carried out on treating wastewater containing an aromatic nitro-compound, nitrobenzene, by the acidogenic-aerobic and aerobic processes. The removal efficiency of nitrobenzene was between 75 and 85% when the wastewater was treated by the aerobic process alone. However, the acidogenic-aerobic process resulted in more than 95% removal of nitrobenzene. During the acidogenic process, nitrobenzene was presumed to be converted to aniline which was more readily biodegradable in the subsequent aerobic process. The existence of an easily metabolized carbon source (sucrose) helped in the bioreduction of nitrobenzene to aniline and nitrobenzene bioreduction to aniline was improved as the sucrose concentration was increased.