Microalgae are considered as a viable and attractive third generation feedstock for bioenergy production due to their rapid growth rate and high lipid content as well as their ability to remove carbon dioxide from the atmosphere. The production of munitions in industrial facilities generates energetic-laden nitrogen-rich wastewater streams, which undergo physical-chemical/biological treatment in order to meet current regulatory standards. In this study, an approach is developed to valorize nutrients and reclaim water from energetic-laden wastewater streams by generating algal biomass for bioenergy production (Figure 1). Initial toxicity assessments and laboratory-scale studies showed promising results on sustaining growth of the freshwater microalgae Scenedesmus obliquus (S. obliquus, ATTC® 11477) using a blend of untreated industrial wastewater streams from a munitions production facility. Biomass production was scaled-up to 100L open pond reactors operated on a semi-continuous mode with 50 rpm paddle-mixing speed, 14:10 hours light:dark photoperiod, and 68-95 μmol/m2/s of fluorescent light intensity. Continuous monitoring of pH and temperature of the growth medium, periodic analysis of cell density and dry weight of microalgae, and analysis of nutrients over time were performed. In addition, the harvested algal biomass was tested for its oil content and composition. Different conditions such as nutrient availability, light penetration, hydraulic retention time and frequency of harvesting were evaluated in order to optimize the biomass growth as well as the oil content of S. obliquus. The results showed that biomass production improved 3-fold when the harvesting frequency was increased while nitrogen starvation increased the lipid content from 13% to 26%, based on the dry weight of biomass. Conversely, no significant increment in oil or biomass production was observed with the increase of light penetration for the two different retention times tested. This study demonstrates the feasibility of the production of microalgae biomass and its utilization as a feedstock alternative for cost-effective biofuel production by reclaiming water and nutrients from the wastewater streams of a munitions production facility.

Algal biofuel: Culture and optimization of Scenedesmus obliquus in untreated energetic–laden wastewater streams

2019 Fall National Meeting

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