Characterization of macrophytes for Na+ removal in synthetic Na-salt solution batch under greenhouse conditions

Abstract

Sodium salt contamination in the fresh water due to industrial effluents, underground rock salts and inland aquaculture is a major concern needs to be remediated, and subsequently recycled as sustainable bioeconomic strategy. Treatment of saline wastewater requires efficient, cost-effective, rapid, and green technologies, so as to mitigate the negative impacts of salinity on agricultural land. Green technology of phytodesalination is proposed to reduce salinity in the wastewater using salt tolerant plant species. present study was designed with an aim to investigate the sodium (Na+) removal capacity of salt tolerant and high biomass producing macrophytes on synthetic saline wastewater. Sesuvium portulacastrum (sea purslane), Pluchea indica (Indian camphorweed), Typha angustifolia (narrow leaf cattail) and Heliconia psittacorum (heliconia) were collected, cultivated in the greenhouse, subsequently treated with 0 (control) and 217 mM NaCl (salt stress) for 4 weeks. Overall growth performance, physiological change and Na+ removal rate in root and leaf tissues of the candidate plant species were measured. Plants were able to maintain their growth and physiological abilities except for shoot height in T. angustifolia (reduced by 13.7%) and chlorophyll content in S. portulacastrum (reduced by 64%). Major accumulation of Na+ was recorded in the shoots of S. portulacastrum and P. indica (halophytic plant species) and the roots of T. angustifolia and H. psittacorum (glycophytic plant species). Since T. angustifolia and H. psittacorum have high plant biomass, they showed higher Na+ removal efficiency at 4.4% and 5.7%, respectively; whereas due to lower plant biomass, S. portulacastrum and P. indica resulted in the removal of only 0.6 and 0.8% Na+ from the batch, respectively. Based on the information from this investigation, the selected candidate plant species can further be studied in the constructed wetland together with the controlled environments including optimized flowrate, vertical or horizontal flow system, plant densities and Na-removal rate in relation to swamp habitat. Novelty statement: T. angustifolia and H. psittacorum have high plant biomass, they showed higher Na+ removal efficiency at 4.4% and 5.7%, respectively; whereas due to lower plant biomass, S. portulacastrum and P. indica resulted in removal of only 0.6 and 0.8% Na+ from the batch. Based on the information from this investigation, the selected candidate plant species can further be studied in the constructed wetland together with the controlled environments including optimized flowrate, vertical or horizontal flow system, plant densities and Na-removal rate in relation to swamp habitat.