Microcosm Study on the Potential of Aquatic Macrophytes for Phytoremediation of Phosphorus-Induced Eutrophication

Phosphorous (P) is one of the primary nutrients to cause the eutrophication of water bodies. This process leads to algal blooms and anoxic conditions which have consequences in the form of mortality of aquatic animals, and impaired water quality. Aquatic macrophytes could be the promising candidates that can filter P from water contaminated with high levels of nutrients. In the present microcosm research, two types of floating macrophytes, i.e., salvinia floater (Salvinia natans) and water lettuce (Pistia stratiotes) were deployed to compare their P-removal rates and efficiency under different incubation times (72, 168, and 264 h intervals). Plants were exposed to different treatments, i.e., (1) P-fed plants, (2) P-starved plants, (3) control treatments, and (4) synthetic wastewater treatment. Both plant species showed substantial P-removal efficiency from P-eutrophicated solutions and removed P-amounts were significantly correlated (R2 ≅ 1 at p ≤ 0.05) with P-accumulated in plant biomass. Plants in the P-starved state showed significantly higher P-removal rates and removal efficiency compared to plants without P-starvation. When Salvinia natans was exposed to 10 mg L−1 of P for 264 h of incubation, 21 g of fresh biomass was recorded during the P-starved phase, more than P. stratiotes (14 g) under similar conditions. The P. stratiotes removed 86.04% of P from 5 mg L−1 P solution, 53.76% from 10 mg L−1 P solution and 66.84% from SWW in the P-starved phase whereas, removal efficiency without the P-starvation phase was 33.03% from 5 mg L−1 P solution, 39.66% from 10 mg L−1 P solution, and 31.64% from SWW after 264 h interval. Compared to S. natans, P. stratiotes removed 86.0% P from a 5 mg L−1 P solution, whereas S. natans removed 56.6% when exposed to the same P solution (5 mg L−1 P solution). Bioconcentration factor (BCF) values were higher in Salvinia natans 10.5 (0.5 mg L−1 P solutions) and 1.5 (5 mg L−1 P solutions) compared to 9.9 and 1.3 of Pistia stratiotes under P-starved conditions. The present work highlighted that these aquatic plants can be a potential green sustainable solution for purifying water with excessive nutrients (N and P), especially waters of wetlands, lagoons, and ponds.