Growing Picochlorum oklahomensis in Hydraulic Fracturing Wastewater Supplemented with Animal Wastewater

Abstract

Hydraulic fracturing is used to enhance oil and gas extraction from tight shale formations and generates millions of gallons of wastewater which needs to be cleaned up prior to disposal or reuse. The current technologies used for the management of this wastewater present technical, economic, and environmental challenges. Hence, the main objective of this study was to examine the potential of algal remediation of hydraulic fracturing wastewater (PW) as an alternative method. Considering that PW contains very low concentration of the nutrients needed for algae growth PW supplemented with animal wastewater (AW-PW) was also examined. Biomass production capacity, average biomass productivity, and specific growth rate of the microalgae strain used in the study, Picochlorum oklahomensis, were 1.87 g L−1, 268 mg L−1 day−1, and 0.35 day−1, respectively, when grown in PW. Complete nitrate, ammonia, and phosphate removal could be achieved by growing algae in PW. Supplementation of PW with animal wastewater enhanced biomass production (1.87–2.40 g L−1) and lipid content (15–25% wt) in the produced algal biomass. A mathematical model with a correlation coefficient of greater than 0.94 was developed to describe the growth kinetics of algae grown in AW-PW.