Wastewater Treatment Plants: Utilizing Methane for Power Production

Many wastewater treatment operations use waste sewage gas from facility processes as a generator set fuel source. Comprised primarily of methane and carbon dioxide, the gas is generated by wastewater digesters used in the water treatment process, and captured to provide the plant with electricity and heat for the digester or other thermal loads. Benefits from methane-to-energy projects include:

• Increased energy efficiency
• Reduced electricity costs
• Decreased environmental impact

Cat^® Dealers can provide expert consultation on the design, installation and maintenance of power plants designed especially for wastewater treatment facilities.

How It Works

Cat low-energy fuel generator sets are engineered to handle fuel with variations in methane content, which is typical of sewage gas. These specially designed generator sets also offer features to protect against moisture and the contaminants in sewage gas. They include:

• Crankcase ventilation pump to eject potentially acidic blow-by gases
• Specially designed aftercooler cores, cylinder heads, main bearings and connecting rod bearings that are hardened against corrosive elements
• Differentiated cooling systems to operate at elevated jacket water temperatures to prevent condensation of contaminants

Heated engine jacket water passes through a plate-and-frame heat exchanger that is connected to the treatment plant's process heat loop. Additional heat can be recovered from the aftercooler circuit and engine exhaust. The system is electrically integrated into the facility using Cat utility-grade paralleling switchgear with PLC-based controls that allow electricity to be exported to the grid or used exclusively by the facility.