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

Abstract

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.

Removal of Copper, Nickel, and Zinc Ions from an Aqueous Solution through Electrochemical and Nanofiltration Membrane Processes

“…According to the United Nations, an estimated 80% of all industrial and municipal wastewater in the developing world is released into freshwater bodies without any prior treatment [18]. Heavy metal removal can be achieved through different physical, chemical and biological methods such as fungal remediation [19], microbial remediation [12,20], phytoremediation [21,22], adsorption [23,24], flotation, coagulationflocculation [25], chemical precipitation or ion exchange [26]; selection between these may be based on the nature and quantum of the pollution load and merits/demerits of decontamination processes along with other factors. It is noted that removal of heavy metals from water/wastewater is still an evolving research area, and there is wide scope for case-specific evaluation, optimization and integration of new and/or available technologies.…”

Two constructed wetlands within a Mediterranean natural park immersed in an agrolandscape reduce most heavy metal water concentrations and dampen the majority of pesticide presence

“…However, the water concentrations of Al, and the rest of the elements, are efficiently reduced as water flows through the different sectors of the CW. Several studies have reported the reduction of heavy metals through microbial and plant biomass in CWs, by means of two main mechanisms: the active one being energy-dependent bioaccumulation, and the passive one energy-independent biosorption (by the adsorption mechanism) (Malyan et al 2021 ; Yu et al 2021 ). For example, Bianchi et al ( 2021 ) reported biosorption through macrophyte species, such as Phragmites australis (the role of reed biomass as a biosorbent material yields the removal of Zn by 73%, under optimum dose and experimental conditions).…”

“…But the water course throughout the different sectors of the CWs causes the decrease in the prevalence of most pesticides. Several processes occurring within the CWs, such as adsorption, hydrolysis, microbial degradation, sedimentation, photolysis, and plant uptake play an important role in said removal of pesticides in CWs (Vymazal and Březinová 2015 ; Malyan et al 2021 ). Moreover, the concentrations of pesticides that have been quantitatively analyzed (Table 2 ) are far below the toxic concentrations for aquatic organisms that have been reported in several studies.…”

“…Moreover, the precipitated oxyhydroxides of Fe and Mn can absorb other heavy metals, such as Pb, Ni, and Cr (Matagi et al 1998). Mn is also oxidized by the microorganisms from the bivalent Mn (II) to tetravalent Mn (IV) and then Mn (IV) is precipitated as manganese oxide (Malyan et al 2021). Moreover, in wetlands, the complexation of metals can be facilitated by the presence of organic molecules (e.g., tannic, fulvic, and humic acids) which are nucleophile or mostly multidentate ligands that interact with heavy metals, influencing their solubility and mobility (Weng et al 2002).…”

Pesticide sorption and mitigation efficiency of a detention pond in a Champagne vineyard catchment

“…A solution to mitigate pesticide pollution from vineyard runoff water is detention ponds (DPs) (e.g., Maillard et al., 2011 ; Maillard and Imfeld 2014 ; Liu et al., 2019 ; Malyan et al., 2021 ). DPs are engineered systems designed to use nature-based solutions such as adsorption followed by sedimentation, physicochemical and microbial degradation and plant uptake ( Vymazal 2005 ), depending on the hydraulic residence time (HRT) and thus water inputs.…”