Constructed Wetlands for Wastewater Treatment: A Review

The first experiments on the use of wetland plants to treat wastewaters were carried out in the early 1950s by Dr. Käthe Seidel in Germany. The first full scale systems were put in operation during the late 1960s and since then constructed wetland systems have been spreading throughout the world. At present, there are several types of constructed wetlands used for wastewater treatment. Free water surface systems with various types of vegetation free-floating, floating-leaved, submerged and emergent – are used in many countries. Subsurface flow systems are primarily built with horizontal flow, however the increased need for ammonia removal initiated a fast development and spread of vertical flow systems which are intermittently fed. This allows higher oxygenation of the bed and consequently higher nitrification. Also, various types on constructed wetlands may be combined in order to achieve higher treatment efficiency. Most constructed wetlands around the world are still primarily used to treat municipal and domestic wastewaters but treatment of many types of industrial and agricultural wastewaters, stormwater runoff and landfill leachate has recently become also common. Despite the mistrust of many civil engineers and water authorities constructed wetlands have been widely accepted around the world and have become a suitable solution for wastewater treatment.