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Produced water (PW) is an effluent from the petrochemical industry that has a significant environmental impact due to its high salinity and presence of chemical compounds and heavy metal. Microalgae have been considered promising to phytoremediation of this effluent and producing biomass with high added value. Therefore, this study aimed to stimulate the production of biomass and biomolecules from Chlorella vulgaris by supplementation with PW and evaluate the synergistic effect of sources of physical and chemical stress. C. vulgaris was cultivated in different PW concentations of PW (not autoclaved) and BG11 medium under a 24 h photoperiod, with inoculum pre-adapted the same photoperiod. The culture containing 70% of BG11 and 30% PW (PW 30%) was the most viable, with a biomass production of 1.35 g/L and a higher concentration of carbohydrates (37.46%) and ash (18.21%) than the control culture (100% BG11). Furthermore, PW 30% also resulted in considerable amounts of lipids (9.92%), proteins (21.94%), chlorophyll-a (6.64 μg/mL), chlorophyll-b (10.57 μg/ mL), and carotenoids (21.38 μg/mL). The major fatty acids were C18:3n6 (21.50%), C20:0 (19.96%), C16:0 (17.12%), and C18:0 (12.15%). The PW 30% treatment showed removal efficiencies for iron (61.80%), chlorides (79.64%), phosphates (97.18%), and petroleum hydrocarbons including total petroleum hydrocarbons (TPH; 45.39%) and resolved petroleum hydrocarbons (RPH; 57.57%). The analyzed fuel properties presented an ideal profile for the production of biodiesel and bioethanol, which can be obtained from carbohydrates. Simultaneously, treatment PW 30% resulted in the production of biomolecule-rich in biomass in addition to the bioremediation effect. [ABSTRACT FROM AUTHOR]

The present work aimed to give an economical destiny to the produced water, a residue generated by the oil and gas industry by means of producing bioactives such as xanthan gum and ramnolipid. These compounds are often used in combination during enhanced oil recovery strategies. On the other hand, reports on co-culture of bacterial strains that are responsible for their production are rare. This research shows a factorial design method associated with surface response analysis to optimize carbon sources, sucrose and crude glycerin, and fermentation agents for culturing Xanthomonas campestris and Pseudomonas aeruginosa using the described conditions. After the critical point validation resulting in xanthan and ramnolipid production of 8.69 and 4.80 g L−1, quality tests showed an apparent viscosity of 1006 cP with an emulsifying activity abouve 50% for 94 h. [ABSTRACT FROM AUTHOR]

• Lauryl glucoside is efficient at 2% (w/v) during oil recovery. • SRBs can grow on surfactant or oil as sole carbon sources. • Surfactant concentrations cause distinct impact on biogenic souring. • Low surfactant concentrations increase biogenic souring. • High surfactant concentrations inhibit biogenic souring. The aim of this work is to quantify the effect of using alkyl polyglycoside (APG) surfactant as the main agent for oil recovery and to quantify its potential impact on biogenic souring. Sand-pack column replicates were subjected to two surfactant concentration injection events both in the presence and absence of oil. The activity of sulphate-reducing bacteria (SRB) was tested using the distinct resultant produced waters (PWs) or with surfactant solutions as the additional carbon source. The results suggested that a surfactant concentration of 2% (w/v) can recover 7.7 fold more oil than 0.1% (w/v). The PWs SRB-activity testing identified that surfactant concentrations below 1% (w/v) can significatively increase microbial activity (256μgSO 4 /L/h) - which enhances biogenic souring. PWs with higher surfactant concentrations inhibited SRB-activity in the presence of oil. SRB-microbes can utilize surfactant as the sole carbon source (concentrations below 2% w/v). Thus, the mixture of surfactant and oil increased or decreased SRB-activity depending on their concentration (low/high, respectively). Surfactant can not only assist in enhancing biogenic souring but, at a higher concentration, may control it without the need of employing significant amounts of biocide. [ABSTRACT FROM AUTHOR]