Closing the loop in a constructed wetland for the improvement of metal removal: the use of Phragmites australis biomass harvested from the system as biosorbent

Abstract

Among the numerous clean-up techniques for water treatment, sorption methods are widely used for the removal of trace metals. Phragmites australis is a macrophyte commonly used in constructed wetlands for water purification, and in the last decades, its use as biosorbent has attracted increasing attention. In view of a circularly economy approach, this study investigated improvement of trace metal removal by recycling the biomass of P. australis colonizing a constructed wetland, which operates as post-treatment of effluent wastewater from an activated sludge plant serving the textile industrial district of Prato (Italy). After the annual mowing of the reed plants, the biomass was dried and blended to derive a sustainable and eco-friendly biosorbent and its sorption capacity for Fe, Cu, and Zn was investigated comparing the batch system with the easier-to-handle column technique. The possibility of regeneration and reuse of the biosorbent was also evaluated. The biomaterial showed an interesting sorption capacity for Cu, Fe, and Zn, both in batch and in column experiments, especially for Fe ions. The immobilization of the biosorbent in column filters induced some improvement in the removal efficiency, and, in addition, this operation mode has the advantage of being much more suitable for practical applications than the batch process.

Potential Use of Constructed Wetland Systems for Rural Sanitation and Wastewater Reuse in Agriculture in the Moroccan Context

“…Coal slag also showed the best removal efficiency of TP (86%) and TN (80%), unlike snail shells, which showed a lower removal rate of TP and TN (20% and 44%, respectively). In a similar approach, Bianchi et al [66] reported that harvested Phragmites australis from constructed wetlands could be dried and tested as a bio-sorbent to optimize the treatment efficiency of a CW on landfill leachates. Effectively, this bio-sorbent showed an important adsorption capacity for Fe (70-100%), Zn (65-85%), and Cu (46-80%) in a column filtration system.…”

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

“…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). Previously, Southichak et al ( 2006 ) also reported the biosorption of Ni, Pb, and Zn through reed biomass.…”

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

“…The dead leaves of tall fescue which contribute 12.6%–16% of the total shoot biomass significantly removed 73.4%–87.2% of total Cd in wastewater. Biosorbent through macrophytes species, such as Phragmites australis (Bianchi et al, 2021; Southichak et al, 2006), Juncus effuses (Ladislas et al, 2015), Carex riparia (Ladislas et al, 2015), Melocanna baccifera (Lalhruaitluanga et al, 2010), and Moringa oleifera (Gautam et al, 2020) were also studied and reported by scientific community. Bianchi et al (2021) investigated the role of reed biomass as a biosorbent material for the removal of Fe, Cu, and Zn from industrial wastewater.…”

“…Biosorbent through macrophytes species, such as Phragmites australis (Bianchi et al, 2021; Southichak et al, 2006), Juncus effuses (Ladislas et al, 2015), Carex riparia (Ladislas et al, 2015), Melocanna baccifera (Lalhruaitluanga et al, 2010), and Moringa oleifera (Gautam et al, 2020) were also studied and reported by scientific community. Bianchi et al (2021) investigated the role of reed biomass as a biosorbent material for the removal of Fe, Cu, and Zn from industrial wastewater. The removal of Fe, Cu, and Zn was observed to be 61%, 93%, and 73%, respectively, under optimum dose and experimental conditions.…”