According to the BioScience journal, The roots of water hyacinth naturally absorb pollutants, including lead, mercury, and strontium-90, as well as some organic compounds believed to be carcinogenic, in concentrations 10,000 times that in the surrounding water. Water hyacinth is found to remove 60-80% of nitrogen and 69% of potassium from the water.
In 1985, the royal project initiated by King Bhumibol of Thailand initiated the use of water hyacinth for water treatment along with the oxidization pond. An oxidation pond is a pond that contains partially treated wastewater which is then left to allow the growth of algae and bacteria which decompose the waste.
According to Principle of Microbiology by Mosby, within an oxidation pond, heterotrophic bacteria (bacteria that use organic carbon as food) degrade organic matter in the sewage which results in production of cellular material and minerals. The production of these supports the growth of algae in the oxidation pond. Growth of algal populations allows further decomposition of the organic matter by producing oxygen. The production of this oxygen replenishes the oxygen used by the heterotrophic bacteria. The oxidation pond should be about 0.5-2 meters in dept and filled with the water hyacinth in the middle of the pond to treat water. The daily water treatment amount is 30,000-100,000 cubic meters.
During the day time, algae in the oxidation pond will go through the process of photosynthesis which created oxygen. Then, bacteria will use oxygen to decompose waste in the water. This process will keep going until the water is cleaned. What to bear in mind is that there must not be too much of the water hyacinth in the water because it would block the sunlight which stops the process of photosynthesis. Therefore, it is important to control the overpopulated water hyacinth by removing it every 10 weeks. In the study done by the Thai king, the BOD in the water increased by 19-85% or 51% on average.