(204c) Using Produced Water to Grow Microalgae

Produced water – also known as hydraulic fracking fluid, is a byproduct of the oil and gas production process and is water that is naturally contained in sedimentary formations. This water has a salinity ranging from as low as 1,000 ppm to greater than 100,000 ppm of total dissolved solids (TDS) and has bicarbonate, other essential micronutrients.

The goal of our research is to evaluate produced water as a potential growth medium for microalgae. Our preliminary lab scale studies with the microalgae species Chlamydomonas reinhardtii, Dunaliela sp. and Nannochloropsis salina, which are known to grow in saline conditions have shown promise. Pre-treatment of produced water was performed by means of centrifugation to remove solids along with vacuum filtration to remove suspended particles (>5 microns). Experiments were then conducted by growing algae cultures in varying proportions of the diluted, pre-treated PW and a standard growth medium specific to each species. The growth performance in each of the cultures was monitored by the measurement of absorbance at 750 nm each day. Initial growth of algae with low concentrations of produced water was similar to the standard growth medium, however, higher produced water concentrations became growth limiting. These studies also indicate that the algae can thrive in produced water even without any necessity of further treatment. The algae-based biomass grown in the produced water could be used as a feedstock to produce biofuels.