According to the US Geological Service, ingesting mercury can effect the central nervous system, immune system, and cause severe birth defects by altering the chromosomal pattern in a developing embryo. The Ecological Engineering Group has identified Arabidopsis thaliana as one of the best ways of naturally removing mercury from contaminated water. Hydroponics is the practice of growing plants in a liquid nutrient solution, without the use of soil. If you grow Arabidopsis thaliana hydroponically, it will absorb the mercury along with other nutrients, leaving you with clean, filtered water.
Prepare the Rockwool
Put the 5-gallon bucket in an out-of-the-way place. It will need to sit, filled with water, for 24 hours. Make sure it will not pose a danger to small children or pets. Fill the bucket two-thirds full with fresh water, and let this sit uncovered for one hour to allow any chlorine to dissipate.
Test the pH of the water--it should be around 7.0. Add a few drops of phosphoric acid. Carefully mix in the acid, then retest the pH. Continue to add acid, a drop or two at a time, until you have lowered the pH to between 4.5 and 5.0.
Submerge the rockwool cubes in the bucket of acidic water. Wear rubber gloves for this step, as the acid can cause skin reactions.
Let the rockwool soak in the bucket of acidic water for 24 hours.
Set Up the Hydroponic System
Assemble the hydroponic system according to the manufacturer's instructions.
Fill the nutrient reservoir with fresh water, and let this sit for one hour to allow the chlorine to dissipate.
Add concentrated nutrient solution to the nutrient reservoir, following the manufacturer's instructions.
Test the pH of the diluted nutrient solution. Arabidopsis thaliana thrives at a neutral pH. Add one or two drops of phosphoric acid or potassium hydroxide to adjust the pH to 7.0.
Perform a water test and note the mercury level. This tells you your starting point.
Add the Plants
Depending on how your hydroponic system was designed, there should be large holes in the lid of the nutrient reservoir or a floating grow tray. Place a net pot in each of these holes.
Put a rockwool cube in each net pot, and sprinkle a few seeds on each cube. Fluff the rockwool with your finger and push it to cover the seeds. If you are using seedlings, gently brush the dirt from the roots and rinse the root system with fresh water. Plant them in the rockwool cubes, fluffing the rockwool to cover the roots.
Water the garden from the top with diluted nutrient solution. You will need to do this until the roots have grown through the rockwool and dangle in the nutrient solution.
Check the water level daily and replenish as needed.
Test the Water
Every two weeks, perform another water test. Note the mercury level--it should be lower than the previous reading. According to the US Environmental Protection Agency, two parts per billion of mercury is a safe level for drinking water.
If the mercury level is within safe levels, siphon off the water and store it for drinking, cooking, etc.
Refill the nutrient reservoir with fresh water and add concentrated nutrient solution, following the manufacturer's instructions.
Arabidopsis thaliana has a life cycle of about six weeks. At week four, start a new batch of seeds, so they will be ready to transplant into your hydroponic system when the first batch dies.
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.