Recent developments in wetland technology for wastewater treatment

Abstract: Constructed wetlands for wastewater treatment have substantially developed in the last decades. As an eco-friendly treatment process, constructed wetlands may enable the effective, economical, and ecological treatment of agricultural, industrial, and municipal wastewater. The present study reviews the recent developments in wetland technology for wastewater treatment from articles published from 2011 to 2012. The papers were searched from Web of Science using the key words constructed wetland and wastewater treatment. Up to 32 articles were selected and a table describes the recent enhancements in wetland treatment technology. Some articles presented notable results, with higher pollutant removal rates or related to some important factors in removal processes. These articles were separated into three main parts, namely, enhancement of nitrogen removal, phosphorus removal and recovery, and wetland contribution to heavy metal removal. The recent trends in the enhancement of wetland treatment were identified. The major enhancement methods for nitrogen, BOD, and COD reduction are hybrid water flow wetland designs and the combination of porous substrates with conventional gravel. Organic substrates, such as wood mulch and rice husk, are a suitable option for the upper porous media. The recent promotion of phosphorus removal involves a solution to internal loading and an inexpensive substrate source. Fragmented Moleanos limestone and alum sludge cake from the water plants present the feasibility of P removal. The main improvement in heavy metal removal depends on the substrate and combination of different treatment methods. Additionally, the free water surface constructed wetland was proven as a stable heavy metal treatment method. Vegetation was confirmed to enhance the removal rate of all wetland types for all kinds of pollutants. However, the species of the vegetation does not significantly influence the removal rates.