An aquatic plant used in wastewater treatment is which plant?

• A. Kelp
• B. Cattail
• C. Duckweed
• D. Arrowhead

Answer: (C)

Using aquatic plants to clean wastewater relies on phytoremediation: plants remove nutrients and contaminants from the water, improving effluent quality. Duckweed is especially effective because it forms a dense, floating mat on the water surface, giving it rapid access to light and enabling very fast growth. That quick growth means a high rate of nutrient uptake, particularly nitrogen and phosphorus, which are the main pollutants in municipal wastewater. By regularly harvesting the duckweed biomass, you physically remove a large amount of these nutrients from the system, helping to reduce nutrient loads and prevent downstream issues like algal blooms. Duckweed also tolerates a wide range of wastewater conditions and is easy to manage in ponds or constructed wetlands, making it a practical, low-cost option for wastewater treatment. Other plants may not provide the same combination of fast growth, surface area for nutrient uptake, and ease of harvest in typical wastewater setups, so duckweed is the best choice.