Salinity Reduction and Biomass Accumulation in Hydroponic Growth of Purslane (Portulaca oleracea)

Industrial wastewater treatment by plant-based bio-filtration

Constructed wetlands (CWs) represent a natural wastewater treatment process, offering economic and environmental advantages. These systems can remove several components that may cause negative impacts on the environment. Media types and plant species are crucial influencing factors for the removal of contaminants in CWs. The goal of this study is to evaluate the capacity of a CW using Tamarix spp. with three filter media to treat FGD wastewater. Planted and unplanted CWs were set up with varying types of biofilm support media: 3 bioreactors were operated with 50% gravel and 50% zeolite (v/v), 3 with 100% gravel, and 3 with 50% gravel, 25% zeolite, and 25% silage. Planted CWs had the greatest potential to reduce the concentrations of B, K, and NH4+-N in 64.9%, 91.1%, and 92.5%, respectively, when used in addition to the filter composed by 50% gravel + 50% zeolite, which was the only media keeping the plants alive for 60 days. The results showed that the optimal selection of filter media depends on the purpose for which the treatment has been projected for, considering that the types of substrates influenced the nature of the contaminant removal in the CW.

Screening Wetland and Forage Plants for Phytoremediation of Salt-Affected Soils in the Vietnamese Mekong Delta

This study evaluated the salt tolerance and sodium (Na) bioaccumulation of Typha orientalis, Lepironia articulata, Eleocharis dulcis, Scirpus littoralis, Brachiaria mutica, Paspalum atratum and Setaria sphacelata at five salinity levels of 0, 5, 10, 15 and 20‰ (corresponding to 0, 2.4, 6.9, 12.6 and 18 g NaCl L^-1). S. littoralis showed zero-reduction in total dry biomass and was classified as a salt tolerant plant based on the membership function value. The highest Na⁺ accumulation was observed in S. sphacelata (307.9 mg plant^-1) in spite of its salt sensitivity, followed by S. littoralis and T. orientalis at concentration of 155 mg plant^-1. Consequently, the Na⁺ phytoextraction potential of these species can be estimated as 46.2, 23.3 and 23.3 kg ha^-1 over 49 days, respectively. Taken together, they show high potential as Na⁺ hyperaccumulators, and can be selected in the national reclamation program for salt-affected soils in the context adaptation to climate change.

Giving waterbodies the treatment they need: A critical review of the application of constructed floating wetlands

Water quality is declining worldwide and an increasing number of waterbodies lose their ecological function due to human population growth and climate change. Constructed floating wetlands (CFWs) are a promising ecological engineering tool for restoring waterbodies. The functionality of CFWs has been studied in-situ, in mesocosms and in the laboratory, but a systematic review of the success of in situ applications to improve ecosystem health is missing to date. This review summarises the pollutant dynamics in the presence of CFWs and quantifies removal efficiencies for major pollutants with a focus on in situ applications, including studies that have only been published in the Chinese scientific literature. We find that well designed CFWs successfully decrease pollutant concentrations and improve the health of the ecosystem, shown by lower algae biomass and more diverse fish, algae and invertebrate communities. However, simply extrapolating pollutant removal efficiencies from small-scale experiments will lead to overestimating the removal capacity of nitrogen, phosphorus and organic matter of in situ applications. We show that predicted climate change and eutrophication scenarios will likely increase the efficiency rate of CFWs, mainly due to increased growth and pollutant uptake rates at higher temperatures. However, an increase in rainfall intensity could lead to a lower efficiency of CFWs due to shorter hydraulic retention times and more pollutants being present in the particulate, not the dissolved form. Finally, we develop a framework that will assist water resource managers to design CFWs for specific management purposes. Our review clearly highlights the need of more detailed in situ studies, particularly in terms of understanding the short- and long-term ecosystem response to CFWs under different climate change scenarios.

Heavy-metal-contaminated industrial soil: Uptake assessment in native plant species from Brazilian Cerrado

Plants of the Cerrado have shown some potential for restoration and/or phytoremediation projects due to their ability to grow in and tolerate acidic soils rich in metals. The aim of this study is to evaluate the tolerance and accumulation of metals (Cd, Cu, Pb, and Zn) in five native tree species of the Brazilian Cerrado (Copaifera langsdorffii, Eugenia dysenterica, Inga laurina, Cedrela fissilis, Handroanthus impetiginosus) subjected to three experiments with contaminated soils obtained from a zinc processing industry (S1, S2, S3) and control soil (S0). The experimental design was completely randomized (factorial 5 × 4 × 3) and conducted in a greenhouse environment during a 90-day experimentation time. The plant species behavior was assessed by visual symptoms of toxicity, tolerance index (TI), translocation factor (TF), and bioaccumulation factor (BF). C. fissilis has performed as a Zn accumulator by the higher BFs obtained in the experiments, equal to 3.72, 0.88, and 0.41 for S1, S2, and S3 respectively. This species had some ability of uptake control as a defense mechanism in high stress conditions with the best behavior for phytoremediation and high tolerance to contamination. With economical and technical benefits, this study may support a preliminary analysis necessary for using native tree species in environmental projects.

Biodesalination-On harnessing the potential of nature's desalination processes

Water scarcity is now one of the major global crises, which has affected many aspects of human health, industrial development and ecosystem stability. To overcome this issue, water desalination has been employed. It is a process to remove salt and other minerals from saline water, and it covers a variety of approaches from traditional distillation to the well-established reverse osmosis. Although current water desalination methods can effectively provide fresh water, they are becoming increasingly controversial due to their adverse environmental impacts including high energy intensity and highly concentrated brine waste. For millions of years, microorganisms, the masters of adaptation, have survived on Earth without the excessive use of energy and resources or compromising their ambient environment. This has encouraged scientists to study the possibility of using biological processes for seawater desalination and the field has been exponentially growing ever since. Here, the term biodesalination is offered to cover all of the techniques which have their roots in biology for producing fresh water from saline solution. In addition to reviewing and categorizing biodesalination processes for the first time, this review also reveals unexplored research areas in biodesalination having potential to be used in water treatment.