Energy management in wastewater treatment plants has recently become a key issue in both facilities design and operation owing to rapidly rising energy costs and possible energy supply interruptions. This two part series of articles focuses primarily on major energy management approaches and options, especially as they pertain to existing facilities, recognizing that many of the same considerations should now be a routine part of new facilities planning and design. The first article emphasized energy costs and use associated with wastewater treatment and pointed out how energy audits could be used to identify and reduce in plant energy consumption. Part one also presented some examples of how energy is being saved in existing plants. This concluding article discusses alternative energy sources that may cut costs while reducing dependence on conventional energy sources.