Oil and gas produced water as a growth medium for microalgae cultivation: A review and feasibility analysis

Scale-up of microalgal biotechnology to provide large quantities of biofuel, lipids, and coproducts is not fully developed because of the large needs for nutrients, water, land, solar insolation, and CO2/carbon supplies. Wastewaters, including oil and gas produced water (PW), may supply a portion of these needs in regions with insufficient fresh water resources. PW is a challenging water resource for this use because of variable salinity, geochemical complexity, and the presence of biologically toxic components. In this paper we review PW volumes, quality, and use in media for microalgae production in the southwestern US, Australia, and Oman. We also include data from the southwestern US, referencing previously unpublished results from the National Alliance for Biofuels and Bioproducts (NAABB) consortium research project. We include a Supplementary Information section that explores cultivation of multiple microalgae species in PW and examines the carbon utilization process, all work performed in support of the NAABB field program. Strains of algae tested in the reviewed papers include Nannochloropsis, Dunalliella, Scenedesmus, and several mixed or unknown cultures. We conclude that the use of PW in algae cultivation is feasible, if the additional complexity of the water resource is accounted for in developing media formulations and in understanding metals uptake by the algae. We recommend additional work to standardize growth testing in PW, better and more thorough chemical analysis, and geochemical modeling of the PW used in media. Expanded strain testing in PW media will identify improved strains tolerant of PW in algae cultivation.