Bioremediation of Aquatic Environments Contaminated with Heavy Metals: A Review of Mechanisms, Solutions and Perspectives

The degradation of water resources is related to anthropic actions such as rapid urbanization and industrial and agricultural activities with inefficient land use and occupation management. Water pollution caused by organic and inorganic contaminants represents a current challenge for researchers and humanity. One of the techniques used to remove pollutants from aquatic environments is bioremediation, through the metabolism of living organisms, and especially phytoremediation, with plants as a decontamination agent. Aiming to demonstrate the current mechanisms, solutions, and perspectives regarding bioremediation, and especially phytoremediation in aquatic environments, a literature review was conducted, highlighting the following subjects: heavy metals as contaminants, phytoremediation, evaluation of resistance mechanisms, removal of heavy metals by microorganisms and biofilters of the artificial floating islands type. From the literature research carried out, it can be concluded that alternatives such as macrophyte plants have proved to be an effective and efficient alternative with a high potential for removal of contaminants in aquatic environments, including concomitantly with microorganisms. There was no mechanism well-defined for specific absorption of heavy metals by plants; however, some results can indicate that if there was sporadic contamination with some contaminants, the plants can be indicators with some adsorption and absorption, even with low concentration in the watercourse by the moment of the evaluation. It is necessary to study bioremediation methods, resistance mechanisms, tolerance, and removal efficiencies for each biological agent chosen. Within the bioremediation processes of aquatic environments, the use of macrophyte plants with a high capacity for phytoremediation of metals, used combined with bioremediating microorganisms, such as biofilters, is an interesting perspective to remove contaminants.