A constructed wetland is a natural process involving wetland vegetation, soils, and their associated microbial assemblages to improve water quality. It is a lot cheaper and requires less energy than standard water filtration and sewage systems that many developed countries use. It is also more environmentally friendly as it only requires natural processes to filter contaminated water. The concept of the constructed wetland was developed in the 1960s by Käthe Seidel in Germany. Before that, between 1952 and 1956, Seidel carried out numerous experiments on the use of wetland plants for the treatment of various types of wastewater, including phenol, dairy, or livestock wastewater . The ability of wetlands to transform and store organic matter and nutrients has resulted in the widespread use of wetlands for wastewater treatment worldwide. Wetland plants are an important component of wetlands, and the plants have several roles in relation to the wastewater treatment processes. The filtration of water contaminants in a constructed wetland relies on the plant's root systems and plant tissues, particularly the processes of phytoremediation and phytoaccumulation where the plants uptake contaminants and particles as they use that as their nutrients to grow and perform photosynthesis . The plant tissues are responsible for filtering out large pieces of debris, providing a surface area for attached biofilms, an excretion of photosynthetic oxygen, which leads to increased aerobic degradation, and uptaking nutrients from the water. Within the plant tissues, there are dense amounts of photosynthetic algae, bacteria, and protozoa. Likewise, the roots and rhizomes that are buried in the wetland soil provide a substrate for the attached growth of microorganisms . These biofilms along with including dead macrophyte tissues are responsible for the majority of the microbial processing that occurs in wetlands. Later researchers have conducted experiments testing the effectiveness of constructed wetlands in various parts of society, such as putting sewage water from agricultural, industrial, petrochemical, and power plant industries into a constructed wetland to determine if water quality improved after the process. In addition, researchers have also tested various aquatic plants, also known as macrophytes, such as reed (Phragmites australis), water spinach (Ipomoea aquatica), bulrush (Scirpus), Timothy grass (Phleum pratense) and bamboo (Phyllostachys heteroclada) to determine their root system's effectiveness in filtering contaminated water.