Constructed wetlands for boron removal: A review

• We reviewed current knowledge regarding to the CWs for boron (B) removal.
• We presented general information about B, related problems in ecological components.
• B removal mechanism in sediment and the role of plants in CWs were also discussed in detail and updated.
• We identified data need that would contribute our understanding of possible use of CWs for B removal.

Boron (B) contamination in the environment still increases because of various natural sources and anthropogenic activities. Therefore, the problem of removing B from water becomes a worldwide concern due to its toxicity and chronic effects on plants, animals and human health. This situation has generated increasing interest in the use of several wastewater treatment technologies in order to remove B from contaminated water. Constructed wetlands (CWs) present friendly alternative methods to treat wastewater around the world, and are used for removing various contaminants including metals and metalloids. This paper reviews current knowledge regarding the removal process of B, discusses application of B removal, and identifies critical knowledge study fields of future and gaps. Despite the fact that the sediment is a major sink for the removal of B, plants can play a significant role under favorable environmental conditions. The most important environmental factors that affect B removal in CWs are climatic conditions (e.g. transpiration rates), pH, temperature, solutions composition and competing species, hydraulic retention time and supporting media. Further research is needed on the major removal mechanism of B in CWs, namely the applicability of surface flow system, hybrid systems and vertical flow systems to remove B from wastewaters, the role of microorganism in order to enhance B removal efficiency.