The phytoremediation of water with high concentrations of nitrogen and phosphorus contamination by three selected wetland plants

Abstract

High concentrations of nitrogen (N) (approximately 400 mg L −1) and phosphorus (P) (approximately 50 mg L−1) in wastewater can directly decrease the nutrient uptake rate of aquatic plants. Three floating wetland plants Myriophyllum elatinoides G., Eichhornia crassipes (Mart.) S., and Alternanthera philoxeroides (Mart.) G. were cultivated under different concentrations of N and P in microcosms to measure their potential capacity to absorb N and P. The results showed that M. elatinoides had the highest ammonia nitrogen (NH4+) and phosphate (PO43−) uptake rates at NH4+ and PO43− concentrations of 500 mg L−1 and 80 mg L−1, respectively, while E. crassipes had the highest nitrate (NO3−) uptake rate at NO3- concentrations of 50 mg L−1. These results, indicate that M. elatinoides absorbs NH4+ and PO43− more efficiently than E. crassipes and A. philoxeroides. The N/P ratio in wastewater impacted the removal of N and P by aquatic plants. The optimal N/P ratios for N and P removal by M. elatinoides, E. crassipes, and A. philoxeroides were 10:1, 20:1, and 20:1, respectively, with M. elatinoides having the highest N and P removal efficiency at this N/P ratio in the first 6 days of the experiment. The results indicated that M. elatinoides had a high potential for removal of N and P from wastewater with high concentrations of N and P, especially at the N/P ratio of 10:1 in the study. These results should provide direction in selection of plants for constructed wetland treatment systems of high concentration N and P wastewater.