Collaborative Research: Enhancing Bioenergy Recovery from Wastewater in an Integrated Microbial-Algal Photobioelectrochemical System

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Municipal wastewater treatment processes consume significant amounts of energy. However, the organic materials fed into the waste treatment process offer the potential for energy-positive waste water treatment if this waste organic material can be converted into energy. A microbial fuel cell is a device that contains special strains of bacteria which consume organic matter in waste water as a fuel to generate electricity and help clean up the water. Although microbial fuel cells have shown promise for sustainable and energy- positive waste water treatment, their performance is low. An unconventional way to improve their performance is to integrate the microbial fuel cell device into a cultivation chamber which grows algae from sunlight. The project will investigate the synergistic aspects the combined algal-microbial fuel cell for its potential to boost electricity production, reduce operating costs by eliminating the external aeration requirement, and remove inorganic as well as organic materials from waste water. The educational activities associated with this project make use of microbial fuel cell demonstrations to stimulate interest in environmental engineering and waste water treatment topics with undergraduate students, K12 students and teachers, and the public.The overall goal of the research is to study the potentially synergistic interactions of a microbial fuel cell integrated into an algal bioreactor as a new platform for energy-positive waste water treatment. In this combined system, the algae generate oxygen which is needed by the microbial fuel cell electrode to drive aerobic micro-bioelectrochemical processes, whereas this same process generates carbon dioxide needed by the algae. This in situ source of oxygen has the potential to intensify electricity generation and eliminate the aeration requirement. The algae can also remove inorganic nitrogen and phosphorus to help further treat the waste water. The research has four objectives. The first objective is to construct a nutrient budget model based on fundamental understanding of the transformation of inorganic and organic nutrient forms within the algal-microbial fuel cell. The second objective is to examine how different algal species affect the stability of bacteria within the microbial fuel cell electrode and the algal biomass productivity. Towards this end, metagenome analysis will be used to identify metabolic functions related to different taxa which are critical to process performance. The third objective is to quantify treatment of organic materials within the algal-microbial fuel cell using mixotrophic algae. The fourth objective is to conduct system development and optimization with different configurations, including scalable systems. Through these objectives, this research seeks to gain a fundamental understanding of critical algae-bacteria interactions during nutrient uptake and electricity generation, and will also reveal the pathways of carbon, nitrogen, and phosphorous transformation via physical, chemical, and metabolic processes.