Quantitative Estimation of Total Nitrogen and Phosphorus in Lemna sp. Used for The Removal of Congo Red Dye from Contaminated Water

Abstract: This study focuses on the quantitative estimation of total nitrogen (N) and phosphorus (P) in the aquatic plant Lemna sp. (duckweed) and its role in removing Congo red dye from contaminated water. Water pollution is considered one of the most critical environmental issues caused by industrial and agricultural activities. The accumulation of nitrogen and phosphorus in aquatic systems leads to eutrophication, excessive algal blooms, oxygen depletion, and overall water quality deterioration. Biological treatment using aquatic plants has been recognized as a low-cost, eco-friendly, and effective alternative compared to physical and chemical methods. Samples of Lemna sp. were collected from Shatt al-Kufa during four seasons and cultivated in experimental basins with different concentrations of Congo red dye. Results revealed that duckweed exhibited a high ability to absorb and accumulate nitrogen and phosphorus in its tissues. Nitrogen removal efficiency reached about 65% in winter and summer, while it decreased to 28% in spring. Phosphorus, on the other hand, was accumulated in large amounts inside plant tissues, highlighting the necessity of periodic biomass harvesting to achieve effective removal from the aquatic environment. The presence of Congo red dye did not impair the plant’s ability to absorb nutrients but showed seasonal variations in uptake efficiency. The findings confirm that aquatic plants such as Lemna minor represent a promising phytoremediation approach for treating industrial wastewater contaminated with dyes and nutrients, due to their combined capacity for direct uptake and stimulation of microbial activity in the rhizosphere.