Mechanistic understanding of the pollutant removal and transformation processes in the constructed wetland system

• Published in: Water environment research 2021-10, Vol.93 (10), p.1882-1909
• Main Authors: Malyan, Sandeep K., Yadav, Shweta, Sonkar, Vikas, Goyal, V. C., Singh, Omkar, Singh, Rajesh
• Format: Article
• Language: English
• Subjects: affecting factors; Aquatic plants; Artificial wetlands; Biological activity; Charcoal; Climatic conditions; constructed wetland system; Contaminants; Denitrification; Design factors; Design parameters; Efficiency; Emergent aquatic plants; Emergent vegetation; Freshwater plants; Genetic transformation; Heavy metals; Hydraulic retention time; macrophytes; Marshes; Metals; Microorganisms; Mineral nutrients; Municipal wastewater; Nitrification; Nitrogen; Nonpoint source pollution; Nonpoint sources; Nutrient removal; Nutrients; Pesticides; Phragmites australis; Plant cover; Plant species; Pollutant removal; Pollutants; Pollution sources; Removal; removal mechanisms; Retention time; Substrates; Typha angustifolia; Typha latifolia; Uptake; Vegetation cover; Wastewater treatment; Water flow; Water treatment; water‐flow regime; Wetlands; Zeolites
• ISSN: 1061-4303; 1554-7531
• DOI: 10.1002/wer.1599

Constructed wetland systems (CWs) are biologically and physically engineered systems to mimic the natural wetlands which can potentially treat the wastewater from the various point and nonpoint sources of pollution. The present study aims to review the various mechanisms involved in the different types of CWs for wastewater treatment and to elucidate their role in the effective functioning of the CWs. Several physical, chemical, and biological processes substantially influence the pollutant removal efficiency of CWs. Plants species Phragmites australis, Typha latifolia, and Typha angustifolia are most widely used in CWs. The rate of nitrogen (N) removal is significantly affected by emergent vegetation cover and type of CWs. Hybrid CWs (HCWS) removal efficiency for nutrients, metals, pesticides, and other pollutants is higher than a single constructed wetland. The contaminant removal efficiency of the vertical subsurface flow constructed wetlands (VSSFCW) commonly used for the treatment of domestic and municipal wastewater ranges between 31% and 99%. Biochar/zeolite addition as substrate material further enhances the wastewater treatment of CWs. Innovative components (substrate materials, plant species) and factors (design parameters, climatic conditions) sustaining the long‐term sink of the pollutants, such as nutrients and heavy metals in the CWs should be further investigated in the future. Practitioner points Constructed wetland systems (CWs) are efficient natural treatment system for on‐site contaminants removal from wastewater. Denitrification, nitrification, microbial and plant uptake, sedimentation and adsorption are crucial pollutant removal mechanisms. Phragmites australis, Typha latifolia, and Typha angustifolia are widely used emergent plants in constructed wetlands. Hydraulic retention time (HRT), water flow regimes, substrate, plant, and microbial biomass substantially affect CWs treatment performance. The graphical illustrates the range of mechanisms and processes involved in pollutant transformation and removal (when comes in contact with the wetland media: soil/substrate, microbes, and vegetation) in the constructed wetland system.