Water purification: A newer biopolymer called chitosan has been used for water purification. Chitosan is used as a flocculant that only takes a few weeks or months rather than years to degrade into the environment. Chitosan purify's water by Chelation when it removes metals from the water. Chelation is when binding sites along the polymer chain bind with the metal in the water forming clelates. Chitosan has been used in many situations to clean out storm or waste water that may have been contaminated.