ABSTRACT

This study aims at determining the optimal conditions for pollutants removal in wastewater using Eichhornia crassipes (E. crassipes) and Pistia stratiotes (P. stratiotes) as appropriate aquatic plants for a post-treatment by phytoremediation. From factors such as residence time, plant density and initial PO₄³⁻ concentration, four responses, i.e. the removal efficiency of PO₄³⁻, NO₃⁻, NH₄⁺ and the chemical oxygen demand (COD) were followed, using complete factorial design. After validation of the regression models by the statistical analyses, optimal conditions were obtained by using the global desirability function. Global desirabilities of 0.96 and 0.97 were respectively obtained for E. crassipes and P. stratiotes, for a residence time of 30 days, a plant density of 60 feet/m² and an initial PO₄³⁻ concentration of 10 mg/L. Using E. crassipes, this corresponds to the elimination of 94.2% of PO₄³⁻; 93.3% of NO₃⁻; 95.0% of NH₄⁺ and 63.6% of COD. In the case of P. stratiotes, 93.9% of PO₄³⁻; 83.4% of NO₃⁻, 99.5% of NH₄⁺ and 84.4% of COD were removed. Finally, under the used conditions, E. crassipes are able to better eliminate phosphorus and nitrates, while P. stratiotes are very effective in removing NH₄⁺ and COD.

摘要

本研究旨在确定使用凤眼莲 (E. crassipes)和Pistia stratiotes (P. stratiotes)作为合适的水生植物进行植物修复后处理的废水中污染物去除的最佳条件。从停留时间、植物密度和初始PO ₄ ^3-浓度等因素，四个响应，即PO ₄ ^3-、NO ₃ ^-、NH ₄ ^{+的去除效率}并采用完全析因设计跟踪化学需氧量 (COD)。通过统计分析验证回归模型后，通过使用全局意愿函数获得最佳条件。对于 30 天的停留时间、60 英尺/米²的植物密度和10 毫克/升的初始 PO ₄ ^3-浓度，分别获得了 0.96 和 0.97 的全局期望值。使用E. crassipes，这相当于消除了 94.2% 的 PO ₄ ^3-；NO ₃ ^- 93.3% ；95.0% 的 NH ₄ ⁺和 63.6% 的 COD。如果是P. striotes , 93.9% 的 PO ₄ ³⁻ ; 去除了83.4% 的 NO ₃ ^-、99.5% 的 NH ₄ ⁺和 84.4% 的 COD。最后，在所使用的条件下，E. crassipes能够更好地去除磷和硝酸盐，而P. stratites在去除NH ₄ ⁺和COD方面非常有效。