algal-based heavy metal removal strategies with the effect of physicochemical
parameters. Use of transgenic approaches to further enhance the heavy metal
specificity and binding capacity of algae with the objective of using these algae for
the treatment of heavy metal-contaminated wastewater is also focused in this article.
Keywords Phycoremediation · Heavy metals · Passive and active algal biomass ·
Mechanism
1 Introduction
Heavy metals (HMs) are defined as metallic element with higher density and have
toxicity at lower concentration. Heavy metals belong to the group of metal or
metalloids with atomic density higher than 4 g cm
À3 or five times or more greater
than water (Kumar et al. 2015). However, in biochemistry HMs are defined as
metallic elements with Lewis acid behavior, i.e., electron pair acceptor. About
53 chemical elements are considered as heavy metal, and most of these HMs are
found as natural constituent of the earth crust and soil. From environmental perspective, any metals or metalloid that poses potential harmful effects to the living
organism even at lower concentration can be termed as heavy metals. Most of these
heavy metals (Zn, Cu, Mn, Ni, and Co) have vital function in plants, while other
metals such as Cd, Pb, Hg, and Cr are found to cause toxic effects in biological
system. The combined influence of urbanization, industrialization, and chemical
consumption in agrarian practices has raised the heavy metal concentration up to
the toxic level; hence its remediation is now considered as global concern. HM
contamination in water is one of the most critical environmental problems, which
include Cd, Cr, Cu, Hg, and Zn as common contaminants (Pathak et al. 2019;
Ahmad et al. 2018; Kothari et al. 2012).
Heavy metal contamination in wastewater depends on industrial processing and is
stated an as anthropogenic activity. HMs are classified as conservative pollutants,
and their accumulation in the environment causes various negative impacts such as
inhibition of photosynthesis and seed germination, decreased enzymatic activity,
reduction of chlorophyll production, etc. In order to prevent the negative impacts of
heavy metals, adequate treatment of wastewater is desired prior to its disposal or
discharge in receiving water bodies. Chemical and biological treatment methods are
available for HM removal, but biological methods are preferred because of limitation
and drawbacks in chemical treatments. Bioremediation is a key process that utilizes
microbes to tackle heavy metal pollution (Pathak et al. 2015). Biological processes
to remove heavy metals are well explored by various researchers as a part of
phycoremediation. However, remediation of heavy metals via algae gained substantial attention due to its effectiveness and feasibility in implementation. Algae offer
potential solution for treatment of industrial wastewater containing heavy metals in a
natural way. Algal-based remediation can be termed as phycoremediation, which not
only resolves the challenges associated with conventional treatment methods but is
54
S. Ahmad et al.
parameters. Use of transgenic approaches to further enhance the heavy metal
specificity and binding capacity of algae with the objective of using these algae for
the treatment of heavy metal-contaminated wastewater is also focused in this article.
Keywords Phycoremediation · Heavy metals · Passive and active algal biomass ·
Mechanism
1 Introduction
Heavy metals (HMs) are defined as metallic element with higher density and have
toxicity at lower concentration. Heavy metals belong to the group of metal or
metalloids with atomic density higher than 4 g cm
À3 or five times or more greater
than water (Kumar et al. 2015). However, in biochemistry HMs are defined as
metallic elements with Lewis acid behavior, i.e., electron pair acceptor. About
53 chemical elements are considered as heavy metal, and most of these HMs are
found as natural constituent of the earth crust and soil. From environmental perspective, any metals or metalloid that poses potential harmful effects to the living
organism even at lower concentration can be termed as heavy metals. Most of these
heavy metals (Zn, Cu, Mn, Ni, and Co) have vital function in plants, while other
metals such as Cd, Pb, Hg, and Cr are found to cause toxic effects in biological
system. The combined influence of urbanization, industrialization, and chemical
consumption in agrarian practices has raised the heavy metal concentration up to
the toxic level; hence its remediation is now considered as global concern. HM
contamination in water is one of the most critical environmental problems, which
include Cd, Cr, Cu, Hg, and Zn as common contaminants (Pathak et al. 2019;
Ahmad et al. 2018; Kothari et al. 2012).
Heavy metal contamination in wastewater depends on industrial processing and is
stated an as anthropogenic activity. HMs are classified as conservative pollutants,
and their accumulation in the environment causes various negative impacts such as
inhibition of photosynthesis and seed germination, decreased enzymatic activity,
reduction of chlorophyll production, etc. In order to prevent the negative impacts of
heavy metals, adequate treatment of wastewater is desired prior to its disposal or
discharge in receiving water bodies. Chemical and biological treatment methods are
available for HM removal, but biological methods are preferred because of limitation
and drawbacks in chemical treatments. Bioremediation is a key process that utilizes
microbes to tackle heavy metal pollution (Pathak et al. 2015). Biological processes
to remove heavy metals are well explored by various researchers as a part of
phycoremediation. However, remediation of heavy metals via algae gained substantial attention due to its effectiveness and feasibility in implementation. Algae offer
potential solution for treatment of industrial wastewater containing heavy metals in a
natural way. Algal-based remediation can be termed as phycoremediation, which not
only resolves the challenges associated with conventional treatment methods but is
54
S. Ahmad et al.