This chapter discusses the energy production potential of different wastewater sources and various treatment processes with an aim of establishing sustainable energy management systems. The refractory fraction of wastewater can be converted to energy through thermal, chemical, or electrical processes. The importance of knowing the potential energy available lies in the choice of treatment methods so that most of the energy can be recovered. Some wastes that may be high in energy value, such as halogenated wastes, may be unsuitable or unattractive to some treatment methods. The chapter discusses several systems for energy recovery with simultaneous treatment of wastewater. Some of the systems include anaerobic treatment, microbial fuel cell (MFC), simultaneous algal biomass production, and wastewater treatment. The adverse environmental impacts associated with anaerobic treatment or MFC are mainly because of electricity consumption in the various process units and transportation/disposal of biosolids.