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The Codiga Center wastewater treatment research site

Stanford's Codiga Center Aims to Transform Water Treatment

14 June 2017

Treating wastewater is an energy-intensive business. The Water Research Foundation, a research organization, estimates that the United States devoted over 30 million megawatt-hours per year to treating municipal wastewater—three times the yearly energy consumption of New York City. All that electricity is expensive. The EPA reckons that up to 35% of many cities’ electricity budgets go to treating wastewater. It would be great, then, if there were a way to treat sewage without expending so much energy. That ability is just what the Codiga Resource Recovery Center, an experimental wastewater treatment facility on Stanford’s campus, aims to prove.

 

The Codiga Center has recently started pilot-scale testing of a new technology, the Staged Anaerobic Fluidized Membrane Bioreactor (SAFMBR), that holds the promise of treating wastewater at net-zero or even net-positive energy usage. Waste-water treatment relies on bacteria to do the dirty work of turning waste into more innocuous compounds. And while traditional water-treatment processes use aerobic bacteria, which require oxygen, to remove waste, SAFMBR uses anaerobic ones that require an oxygen-free environment. That matters, because most of the electricity that is used to run treatment plants today goes to making sure the water has enough oxygen for the waste-removing microbes to flourish. This is done by either by injecting oxygen into it through a practice called gas sparging, or by mixing the water enough that atmospheric oxygen diffuses into it from the air. Because the anaerobic bacteria in the SAFMBR system don’t require oxygen, the need to aerate the water, and therefore the energy demand, is eliminated.

 

Director of Operations, Sebastien Tilmans, shows student operators the new bacterial sludge.

 

What’s more, while aerobic bacteria convert carbon in the wastewater to CO2, the anaerobes populating the SAFMBR turn that same carbon into methane­, the primary constituent of natural gas. Unlike CO2, methane is combustible, so it can be captured and burned to generate heat and electricity that can be recycled back into the operation of the plant. It can also be used to make other valuable materials; Mango Materials, a Bay Area company cofounded by two Stanford CEE alumni, turns biogas methane into a biopolymer called polyhydroxybutyrate, or PHB. In addition to its use as a replacement for conventional petroleum-based plastics, PHB commands a high price as an additive to fish feed in aquaculture settings, where it has proven to be a cost-effective way of improving fish health.

 

The water-treatment industry is used to operating on forty-year time spans, and is notoriously conservative when it comes to technology adaptation. But today’s infrastructure, mostly built in the 1970s, is aging rapidly and needs replacement. Regardless of the environmental benefits, many utilities will likely be enticed by the prospect of technology that promises to cut their operating expenses by a third. If the pilot testing goes well, the future of wastewater treatment may very well start at Stanford’s Codiga Center.

 

 

David Zweig is a graduate student studying Chemical Engineering at Stanford.