SUSTAINABLE ALGAE-BASED PRODUCED WATER TREATMENT: ENHANCING TREATMENT EFFICIENCY AND VALUE-ADDED PRODUCT GENERATION

Abstract

The treatment of produced water (PW) can help alleviate water scarcity and enhance the recovery of sustainable resources from oil and gas fields. After further processing, algae technology can remediate the toxic effects of pollutants in produced water and utilize nutrient supplements and beneficial chemicals to make water available for additional uses. The produced biomass can also be employed for the production of biofuel. The degradation method utilizing local marine mixed culture algae to remove BTEX present in different wastewater resources, specifically produced water with various concentrations and tackling their harmful impacts on the environment and ecosystem, had an effective influence by using cost-effective and sustainable sources with low-cost and low energy. The results examined the growth ability of a mixed algal culture in the presence of varying concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX) added to the cultivation medium. The results revealed that both mixed-culture marine algae and the isolated Tetraselmis sp. KC820794.1 could thrive in seawater with varying concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX). The mixed culture achieved approximately 96% benzene removal efficiency, while Tetraselmis sp. QUCCCM152 obtained 95% of the higher consumption value from p-xylene. Moreover, the results showed that marine algae and Tetraselmis sp. QUCCCM152 could be a promising candidate for BTEX degradation as a mixture. The results showed a negative correlation between BTEX concentrations and biomass's dryweight, indicating that higher BTEX concentrations led to a reduction in biomass. The increase in BTEX concentrations significantly impacted both the final biomass and the growth rate of the algae. Moreover, microalgae effectively break down organic compounds from raw produced water, indicating that bioremediation was high at low produced water concentrations, achieving higher removal efficiency. Also, microalgae notably uptake different constituents from produced water and use them as a growth medium. The mixed culture successfully degraded all BTEX compounds from raw produced water. Filamentous cyanobacterium Geitlerinema sp.was observed as the dominant algal strain, which thrives significantly on produced water at different concentrations. The finding indicates the potential utility of the isolated strain in various wastewater treatment processes. Further treatment needs to utilize Geitlerinema sp. in the PW to enhance the removal of harmful components. Consequently, algae-treated generated water offers substantial benefits in terms of water availability and optimization of growing conditions. In addition, it examines the impact of advanced oxidation processes (AOPs) on mixed culture marine algae, including ultraviolet radiation (UV), UV/H2O2, ozone, and the Fenton reaction (Fe+2/H2O2). The process focuses on generating hydroxyl radicals (OH) to disrupt algal cell walls and enhance their permeability. The production of ethanol, methanol, and fusel alcohol (by-products), including 1-butanol, 1-propanol, and 1-pentanol (Amyl alcohol), after 24 and 48 hr of fermentation was determined. The effectiveness of various pretreatments in enhancing carbohydrate liberation was analyzed. Ozone produced initial carbohydrates of 0.05 g/gDCW at a reaction time of 30 min ( flow rate of 0.33 L/min). Following the Fenton reaction, the maximum initial carbohydrate of 0.046 g/gDCW was released at 11.09 mM of Fe+2, yielding a 67.4 and 89.1% reduction after 24 and 48 hr, respectively. Among the pretreatment processes, the highest ethanol yield was obtained using the Fenton reaction with a yield of 1.12 g ethanol/g carbohydrate after 48 hr of fermentation at 30 °C. Followed by ozone pretreatment, yielding 0.65 g ethanol/g after 24 hr of fermentation at 30 min exposure time. A 0.3668 g ethanol/g was attained at 30 min of ultraviolet radiation (UV) pretreatment after 48 hr. However, a reduction in the ethanol yield was observed after 24 hr of fermentation, resulting in 0.251 g ethanol/g after UV/H2O2 pretreatment. The results emphasize the importance of AOPs for tackling the limitations of conventional pretreatment techniques and improving the viability of algae-based biofuels as an alternative energy source. Integrating advanced oxidation pretreatment with algal-based treatment of produced water increases biofuel yield and aids in the sustainable remediation of industrial effluents. The approach demonstrates significant technical feasibility and offers a potentially economical, scalable solution for tackling energy and environmental issues.