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Improved microalgae biomass production and wastewater treatment: Pre-treating municipal anaerobic digestate for algae cultivation

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2018 ASABE Annual International Meeting  1801333.(doi:10.13031/aim.201801333)
Authors:   Qichen Wang, Brendan T. Higgins, Haodong Ji, Dongye Zhao
Keywords:   microalgae, anaerobic digestate, biofuel, wastewater treatment, nutrient removal

Abstract. The cost from algae cultivation is one of the major problems which is limiting the commercialization of algae derived biofuels. On the other hand, the aqueous portion of anaerobic digestate, which contains nutrients that pollute the environment, also contains the nutrients required for algae growth. In that case, using anaerobic digestate as the nutrient source for algae growth becomes very attractive for both waste treatment and biofuel production. However, full strength anaerobic digestate is very inhibitory to algae growth. Large amounts of freshwater are typically used to dilute the inhibitors down to a tolerable concentration for algae growth, with dilution factors of 10-30 fold being typical. Therefore, removing these inhibitors by pretreatment instead of using freshwater dilution becomes a reasonable solution for algae cultivation in anaerobic digestion. Chlorella. sorokiniana, a very robust and ammonium tolerant green algae species, was used in this study. An enhanced biomass production was observed after culturing C. sorokiniana in activated sludge pretreated municipal anaerobic digestate. Nanomaterials developed from titanium dioxide on an activated carbon support were also tested as a means of oxidizing organic inhibitors but algae growth did not improve. Further efforts will be undertaken to improve both the activated sludge and nanomaterial pre-treatment approaches to reduce algal growth inhibition on full-strength anaerobic digestates.

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