Examples of engineered wetlands are those currently constructed for remediation applications: as surface flow systems for the removal of pollutants from liquid effluents such as sewage and petroleum wastes. The systems rely primarily on microbial communities, which grow as biofilms in the plant root zone. Their construction relies on an understanding of the relationship between the selection of vegetative species and soil, hydrology, grading/site preparation, and installation methods. Construction of wetlands involves an understanding of the various scientific, legal, and technical components of wetland ecology.
An engineered wetland with areas of open water is similar to that of a natural marsh. These systems are typically designed to support the growth of emergent wetland plants, interspersed with lagoons. These surface flow systems are more tolerant of wastewaters with high suspended solid concentrations than gravel-bed systems, and they support a higher biodiversity than subsurface flow water treatment systems. They model the ecology of natural habitats such as salt scrub, pine savannahs, estuarine tidal marshes, forested wetlands, shrub-scrub wetlands, emergent wetlands, freshwater tidal wetlands, brackish tidal wetlands, and open marshes. Construction requires an understanding of the relationship between the selection of vegetative species and soil, hydrology, grading/site preparation, and installation methods. The management system involves an ecological rationale for maintaining a high clearance rate of pollutants.
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