Nitrate influence on Scenedesmus Obliquus growth and organic removal from produced water

Microalgae offer a cost-effective solution for treating pollutants in produced water, which contains various hazardous components especially organic compounds. Scenedesmus obliquus is frequently utilized in wastewater treatment applications due to its resilience and efficiency. Recent studies have focused on the benefits of nitrate for microalgae growth in wastewater, but limited attention has been given to its role in aiding pollutant removal by microalgae. This study evaluates the impact of sodium nitrate on the growth of Scenedesmus obliquus in produced water and its effectiveness in removing organic materials. Results indicated that supplementation with 2 g of sodium nitrate yielded the highest growth performance for Scenedesmus obliquus, reaching a dry weight of 4.56 g/L. However, continual addition of raw produced water every three days reduced growth rates. All produced water samples with sodium nitrate supplementation showed low total organic carbon removal, though a gradual reduction in total organic carbon over time suggested that Scenedesmus obliquus began consuming organic compounds once nitrogen sources were depleted. Moreover, produced water with sodium nitrate supplementation contained more detectable organic compounds compared to produced water without sodium nitrate. In conclusion, while sodium nitrate effectively supports Scenedesmus obliquus growth in toxic produced water, it provides limited assistance in organic compound removal.