Constructed wetlands: a review

The first aim of this invited literature review is critically to review and evaluate hydrological, physical and biochemical processes within natural and constructed wetlands. The second aim is to contribute the thoughts of the authors to the discussion with the help of a case study focusing on gully pot liquor treatment. The performances of constructed treatment wetlands with and without macrophytes, and aggregates of different adsorption capacities will be assessed, principle findings highlighted and conclusions, also relevant to the literature review, will be drawn. The relationships between aggregates, microbial and plant communities as well as the reduction of predominantly biochemical oxygen demand, suspended solids and heavy metals are investigated. After maturation of the biomass, which dominates the litter zone, organic and inorganic contaminants are usually reduced similarly for all wetland types. There appears to be no additional benefit in using macrophytes and expensive adsorption media in constructed wetlands.