Performance of Chlorella sorokiniana in bioremediation of organic pollutants from produced water under heavy metal stress

Produced water (PW), a byproduct of oil and gas exploration, contains hazardous dissolved organic pollutants (DOPs) and heavy metals (HMs), posing significant environmental risks. This study investigates the bioremediation potential of Chlorella sorokiniana ( C. sorokiniana ) in synthetic produced water (SPW) with varying organic pollutants concentrations, both with and without lead (Pb²⁺) as heavy metal (HM). The microalga was cultivated for eight days across PW gradients (10–100%) in photobioreactors supplemented with synthetic municipal wastewater (SMW) as nutrient source. Growth kinetics, pollutant removal efficiency, and lipid accumulation were analyzed. Total organic carbon (TOC) was measured as an aggregate parameter to quantify the removal of DOPs. The results showed that C. sorokiniana achieved optimal growth and biomass productivity at 10–30% PW, with enhanced adaptation under mild Pb²⁺ exposure in 20% PW (124.63 mg/l/d biomass productivity). Maximum TOC removal (95%) was observed at 50% PW. Pb²⁺ mostly eliminated through pH-induced precipitation and biosorption followed by partial bioaccumulation. Conversely, extreme salinity and HM toxicity at 100% PW substantially hindered microalgal metabolism. These findings exhibit the potential of C. sorokiniana as a sustainable bioremediation agent for supplemented PW treatment, offering an integrating wastewater remediation with biomass valorization for bioenergy applications.