Biosurfactant production during saline oilfield produced water treatment: a prospect for coupling wastewater management with enhanced oil recovery applications

Considerable efforts have been made by the oil industry to develop sustainable strategies for managing produced water (PW) and enhancing oil recovery. This study evaluated biosurfactant (BS) production during PW treatment (0.26 g L1 of total petroleum hydrocarbon (TPH) and 3.5% salinity) using Alcanivorax borkumensis SK2 as an inoculum. In batch experiments (24 and 96 h of incubation), nitrogen concentration was a key factor influencing BS production. A cell-bound and an extracellular BS were produced during the exponential and stationary growth phases, resulting in a surface tension (ST) decrease of up to 27%. BS production scaled up in a sequencing batch airlift reactor (23 days of operation, 3 cycles) showed ST reduction from 72 to 49.6 ± 0.5 mN m1 (in a 166 h cycle duration), coupled with a TPH removal efficiency of 97%. BS (crude extract) production yield (YP/S) of 0.059 g g1 was attained (15 mg L1 of BS). Chemical characterization identified the BS as a glycine-glucolipid. BS production from PW treatment is a promising strategy for its valorization in applications such as microbial enhanced oil recovery, supporting a circular economy in which the wastewater generated is simultaneously treated, valued, and reused.