The Green Side of Produced Water Management: can we use Microalgae to Clean up Produced Water?
Crude oil extraction generates vast amounts of water known as produced water (PW). The US Department of Energy estimates that globally two to three barrels of water are produced for every barrel of oil and that over 200 million barrels of water are produced daily worldwide. The majority of PW is used for re-injection for improved oil recovery; however, in the US, more than one third is injected for disposal at a cost of $0.05-2.65 per barrel.
With global water supplies becoming ever scarcer, we have investigated the technical and economic issues surrounding the use of microalgae in cleaning up PW for beneficial reuse, with concurrent production of energy from biomass. Our findings suggest that factors such as salinity (up to 200k TDS) or organic contaminants (e.g. benzoate) are unlikely to be problematic. Microalgae thrive at high CO2 concentrations and produce oxygen, which may be beneficial for symbiotic biodegradation of soluble hydrocarbons that are difficult to remove chemically or physically. Microalgae can be used in open ponds or photobioreactors and algal ‘oxidation ponds’ are already widely used in municipal waste-water treatment. However, a number of factors mean that algal produced water treatment should only be considered under specific conditions.