Bio-inspired energy and water recovery from low substrate wastewaters

Author(s): Gude, V.; Stuart-Dahl, S.

The energy and water production issues are intertwined and cannot be addressed in isolation. Wastewater treatment and desalination, in particular, are energy consuming processes which can have detrimental effects on the environment. Integrated solutions that utilize waste sources to generate energy, which in turn, can be used to produce freshwater are attractive options to address current energy and water issues. In this context, bioelectrochemical systems have evolved as a novel technology to convert wastes into valuable forms of energy. Bioelectrochemical systems can be employed to generate clean electricity, or high value energy or chemical products from various wastewater sources and organic or inorganic wastes that can serve as fuel feedstock for electroactive bacteria. Microbial desalination cells (MDCs) are based on an integrated configuration in which, wastewater and saline water sources can be treated simultaneously without any external power input or mechanical energy or pressure application. This process offers multiple benefits of energy and resource (water and nutrients) recovery while eliminating environmental pollution. In this research, low substrate synthetic wastewaters with chemical oxygen demand (COD) less than 300 mg/L were treated at different concentrations in microbial desalination cells. A process optimization model was utilized to study the performance of the photosynthetic microbial desalination cells. The variables include substrate concentrations, total dissolved solids, and algae concertation in the cathode chamber. Relationships between the COD concentrations, algae and salt concentrations was evaluated. Power densities and potential energy benefits from algal biomass growth were calculated. This presentation will provide a discussion on the suitability of MDCs for treating low substrate wastewaters such as agricultural wastewaters, anaerobic digester effluents and septic tank effluents for net energy production and water desalination.

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