A passive treatment system is a method for removing metals from acid mine drainage. There are several types of passive treatment systems, each of which may be used on their own or in combination to treat effluents. The type of system selected is dependent upon the chemistry of the acid mine drainage and the flow of the discharge, as well as relevant regulations. Passive treatment systems do not require power and are less expensive than active treatment systems. They also require less maintenance, which is an advantage in remote locations.[1]