4.4 - Phytoremediation

Definition of Phytoremediation

• Phytoremediation is a treatment method that uses plants for the degradation, extraction or elimination of pollutants from soil and water.
• The term comes from phyton (plant) and remediate (repair).
• In wastewater treatment, aquatic plants absorb heavy metals and nutrients and trap harmful nutrients and microorganisms.

Key Phytoremediation Plants and Their Functions

Water Hyacinth (Eichhornia crassipes)

• Its long roots accumulate heavy metals such as copper and lead in water.
• Excessive growth in water can reduce dissolved oxygen until fish cannot live.

Sunflower

• Used to remediate soil polluted by the nuclear power plant explosion in Chernobyl, Russia.
• Acts as a hyperaccumulator that eliminates zinc, chromium, copper, lead and nickel, and radioactive substances such as caesium and strontium.

Water Lettuce (Pistia stratiotes)

• Grows rapidly, accumulates heavy metals and absorbs nutrients in wastewater treatment plants.

Water Spinach

• Roots of ground water spinach absorb mercury from soil.
• Roots of river water spinach absorb cadmium from water.

Applications of Phytoremediation in Life

• Removes heavy metals, nutrients and pollutants from wastewater.
• Remediates soil contaminated with heavy metals and radioactive substances.
• Treats wastewater in wastewater treatment plants using suitable aquatic plants.

Effectiveness in Controlling Water and Soil Pollution

Water Pollution Experiment

• Aim: Study the effectiveness of phytoremediation plants in controlling water pollution.
• Hypothesis: Water hyacinth roots absorb ammonia in lake water.
• Manipulated variable: Presence of water hyacinths.
• Responding variable: Ammonia reading at the end of the experiment.
• Constant variable: Volume of lake water.
• Add equal volumes of lake water and 10% ammonium chloride solution to containers A and B; place six cleaned water hyacinths in A only.
• Record initial ammonia readings, leave both containers at room temperature for seven days, then record final readings.

Soil Pollution Experiment

• Aim: Study the effectiveness of phytoremediation plants in controlling soil pollution.
• Hypothesis: Water spinach roots absorb nutrients such as ammonia in soil.
• Manipulated variable: Presence of water spinach.
• Responding variable: Ammonia reading in the soil at the end of the experiment.
• Constant variable: Mass of black soil.
• Prepare equal masses of black soil and food waste in containers A and B; plant 20 water spinach stalks in A and leave B without plants as the control.
• Water both containers equally for two weeks and compare their initial and final ammonia readings.