Imagine you just discovered the local water supply contains mercury. Of course, the water department assures you the mercury level is not high enough to kill you, but you have young children and want to limit their exposure to mercury. Use hydroponics to absorb most or all of the mercury from your water. The Arabidopsis thaliana plant has been shown to effectively absorb mercury, and is used to clean toxic spills. Arabidopsis thaliana thrives in a hydroponic system, and within two weeks produces water free from mercury.
Prepare the Rockwool Cubes
Place the 5-gallon bucket where it can sit undisturbed for 24 hours. Fill the bucket two-thirds with water and let it sit for one hour. This allows any chlorine in the water to dissipate.
Use the pH meter or liquid test kit to test the pH of the water. It should be around 7.0. Add 1 to 3 drops of phosphoric acid and mix well. Retest the pH of the water. Continue to add small amounts of phosphoric acid until the water reaches a pH between 4.5 and 5.0.
Submerge the rockwool cubes in the acidic water. Allow them to soak for 24 hours.
Set Up the Hydroponic System
Set up the hydroponic system according to the manufacturer's instructions.
Fill the nutrient reservoir with fresh water and add concentrated nutrient solution, following the manufacturer's instructions.
Use the pH meter or liquid test kit to test the pH of the diluted nutrient solution. Arabidopsis thaliana grows best at a neutral pH around 7.0. Use small amounts of phosphoric acid or potassium hydroxide to adjust the pH.
Put a net pot in each hole in the lid of the nutrient reservoir. Put one rockwool cube in each net pot.
Place 3 or 4 Arabidopsis thaliana seeds in each rockwool cube. Use your fingers to fluff the rockwool and cover the seeds. If you are working with seedlings, plant one seedling in each cube. Water from the top with the concentrated nutrient solution.
Test the Water
Use the water test kit to test the mercury level in the hydroponic water. Take note of this reading.
Check the water level daily and replenish with fresh water as needed. Continue to water seeds from the top until the roots grow through the rockwool cube into the nutrient reservoir.
Perform a water test every two weeks. When the water test shows no mercury, the water is safe for use in the household. Drain the nutrient reservoir into a holding container.
Replenish the nutrient reservoir with fresh water and concentrated nutrient solution.
Arabidopsis thaliana has a very short growth cycle, about six weeks. At week four, start a new batch of seeds in rockwool cubes. These will be ready to transfer into your working hydroponic system when the old plants begin to die.
About this Author
Tricia Ballad has written professionally since 2004. She has authored three books, as well as numerous articles on parenting and website content involving green living. Her work has appeared in Natural Family Online and Budget Artists. She holds a Bachelor of Arts in English with a creative writing specialization from Bradley University.