Sustainable utilization of Pistia stratiotes for phytoremediation of heavy metals and nutrients contaminated drainage water.

Heavy metal contamination in aquatic ecosystems poses significant environmental and public health risks. This study aimed to evaluate the of water lettuce (Pistia stratiotes) to remove Copper (Cu) and Lead (Pb) from highly polluted water in laboratory settings, with the goal of applying it to areas heavily contaminated with Cu and Pb. A second objective was to investigate its potential use in removing heavy metals and nutrients from the Bahr El Baqar drain. Also assessed the Pb adsorption capacity of its dry roots. This is due to its remarkable ability to accumulate high concentrations of lead in its roots. Samples of P. stratiotes were collected, acclimated and tested for the accumulation of Pb and Cu at 0.0, 25, 50, 100, 200, 400, and 800 mg L-1 for 14 and 18 days. The BCF, TF and BAC were determined. Also, samples of P. stratiotes were examined for reducing or purifying the water of Bahr El Baqar Drain (a mixture of agricultural, industrial and sewage water), which is one of the largest major drains in Egypt polluted with heavy metals. Chlorophyll contents were estimated in P. stratiotes treated in Bahr El-Baqar drainage water, water polluted with 50 µg ml-1 of each Pb Cu and water control for 6-day. A batch system was used for the kinetics and equilibrium biosorption of dry roots with Langmuir and Freundlich models. Results demonstrated that P. stratiotes effectively accumulated Pb in roots (67,379.69 mg kg-1 at 800 mg L-1 after 14 days) with minimal translocation to leaves (TF: 0.0003), whereas Cu showed significant shoot translocation (2,851.61 mg kg-1, TF: 0.74). Despite chlorophyll reduction (26.31% at 50 mg L-1 Pb) and carotenoid decline (99.3% at 50 mg L-1 Cu), the plant exhibited high bioconcentration (BCF: 41.39 for Pb) and bioaccumulation (BAF: 7.03-29.29 for Cu), highlighting its suitability for phytostabilization and phytofiltration in contaminated systems. Dry roots outperformed conventional adsorbents in Pb adsorption (1,666.67 mg kg-1 via Langmuir model). In Bahr El-Baqar water, P. stratiotes removed 100% of Pb, Cu, and Ni, and 94.47% of Zn within 18 days, while reducing electrical conductivity (33.2%), pH (3.35%), and nutrient levels (Ca: 79%, K: 91.74%, Mg: 21.43%). These findings confirm that P. stratiotes is a cost-effective solution for remediating metals and nutrients.