Abstract
Increasing levels of freshwater contaminants, mainly due to anthropogenic activities, have resulted in a great deal of interest in finding new eco-friendly, cost-effective and efficient methods for remediating polluted waters. The aim of this work was to assess the feasibility of using a green microalga Desmodesmus sp., a cyanobacterium Nostoc sp. and a hemicryptophyte Ampelodesmos mauritanicus to bioremediate a water polluted with an excess of nutrients (nitrogen and phosphorus) and heavy metals (copper and nickel). We immediately determined that Nostoc sp. was sensitive to metal toxicity, and thus Desmodesmus sp. was chosen for sequential tests with A. mauritanicus. First, A. mauritanicus plants were grown in the ‘polluted’ culture medium for seven days and were, then, substituted by Desmodesmus sp. for a further seven days (14 days in total). Heavy metals were shown to negatively affect both the growth rates and nutrient removal capacity. The sequential approach resulted in high metal removal rates in the single metal solutions up to 74% for Cu and 85% for Ni, while, in the bi-metal solutions, the removal rates were lower and showed a bias for Cu uptake. Single species controls showed better outcomes; however, further studies are necessary to investigate the behavior of new species.
Highlights
The rate of human environmental damage is continuously increasing and represents one of the most urgent challenges we face today
The aim of this work was to assess the feasibility of a combined approach using the green microalga Desmodesmus sp. and/or the cyanobacterium Nostoc sp. coupled with the hemicryptophyte A. mauritanicus for bioremediation of polluted waters with an excess of nutrients and heavy metals (HM)
In the bi-metal solution, the Cu and Ni removal by single cultures of Desmodesmus sp. and A. mauritanicus was always higher than that measured in the combined sequential system (Figure 4e,f)
Summary
The rate of human environmental damage is continuously increasing and represents one of the most urgent challenges we face today. Conventional clean-up techniques, i.e., chemical and engineering-based methods, even if effective, are, in general, very expensive and consist of in-situ and ex-situ interventions, like soil excavation, soil washing or burning, pump and treat systems, solidification with stabilizing agents, vitrification at high temperatures and electrochemical separation. These techniques have some disadvantages considering that they can destroy the soil biotic components and are technically difficult, energy intensive and expensive [1]. Among the other remediation methodologies, phytoremediation is one of the most cost-effective, environmentally friendly and low energy consumptions and can be accomplished in situ. Plants have many endogenous genetic, biochemical and physiological properties that make them ideal agents for soil and water remediation [3]
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