This article appears in the Q2 2018 of District Energy magazine.
Two projects demonstrate the use of biogas to cogenerate heat and power, boosting the sustainability of wastewater treatment operations.
Water reclamation facilities – an important and often less visible component of public infrastructure – are charged with a significant task: treating sanitary flows, protecting and maintaining environmental health, and improving wellness and quality of public health. It should then come as no surprise how critical these facilities are to our way of life and that their reliable, uninterrupted operation is crucial – a factor often making them prime candidates for combined heat and power systems. Not only is CHP a good idea in general, but the wastewater treatment plant process also allows for CHP to be utilized with biogas. While wastewater treatment processes vary, many reclamation facilities employ anaerobic digestion – a process whose byproduct, biogas, can often provide fuel for CHP systems. Once appropriately cleaned and treated, this gas can be used to generate power, just like commercially available natural gas.
The most common form of anaerobic digestion is a biological process that uses bacteria (in the absence of oxygen) to break down organics into liquid or slurry form. As the organics are broken down, biogas is released. This gas, which consists of approximately 60 percent methane and 40 percent carbon dioxide, can be recovered, treated and used on-site. The digesters also reduce the solids content of the feedstock and produce an effluent that is low in odor and rich in nutrients.
Mario Vecchiarello, PE, Senior Vice President and Senior Electrical Engineer, CDM Smith
Matthew Goss, PE, Vice President and Technical Strategy Leader for Infrastructure and Energy, CDM Smith
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