REVIEW
Phycoremediation of wastewaters: a synergistic approach using
microalgae for bioremediation and biomass generation
N. Renuka
•
A. Sood
•
R. Prasanna
•
A. S. Ahluwalia
Received: 17 April 2014 / Revised: 18 September 2014 / Accepted: 22 October 2014 / Published online: 18 November 2014
Islamic Azad University (IAU) 2014
Abstract Discharge of untreated domestic and industrial
wastewater into aquatic bodies is posing a serious eutrophi-
cation threat, leading to a slow degradation of the water
resources. A number of physical, chemical and biological
methods have been developed for the treatment of wastewa-
ters; among these, the use of microalgae is considered as a
more eco-friendly and economical approaches. Microalgae
are versatile organisms which perform multiple roles in the
environment—bioremediation of wastewater, gleaning of
excess nutrients and in turn, generate valuable biomass which
finds applications in the food, biofuel and pharmaceutical
industries. They are currently being utilized to reduce the high
nutrient load (especially N and P) from wastewaters, which
fulfill the growth requirements of microalgae, making it a
suitable cultivation medium for biomass production. The
present review represents a comprehensive compilation of
reports on microalgal diversity of wastewaters, followed by a
critical overview of their utilization, suitability and potential
in bioremediation vis-a-vis biomass production. This review
also emphasizes the superiority of polyalgal and consortial
approaches in wastewater treatment, as compared to the use of
unialgal inocula, besides providing useful pointers for future
research needs in this area.
Keywords Wastewater Eutrophication Microalgal
diversity Consortia Nutrient removal Biomass
production
Introduction
Issues related to environmental pollution are becoming
more serious with the increasing population, urbanization,
industrialization and their indirect effects on ecosystem
services (Rawat et al. 2011; Sood et al. 2012). The con-
sequences include excessive generation of wastes/waste-
water, release of untreated water into the freshwater
resources and global warming, which are posing serious
challenges for the scientific community, in terms of sus-
tainability of our planet for the present as well as future
generations. Each facet of environment pollution has its
own list of problems which require specified know-how
and technologies to meet and overcome the challenge. In
this context, mixing of untreated wastewater in aquatic
bodies is emerging up as one of the major issues that is
challenging the stability of nations (Renuka et al. 2014;
Yang et al. 2008). This is mainly due to the reason that the
majority of populations in developing countries are directly
or indirectly dependent on the freshwater resources for
their day-to-day activities.
In developing countries like India, water scarcity is
presenting serious issues, because of population explosion
resulting in large quantities of sewage wastewater. Coupled
with this, increasing industrialization, indiscriminate and
excessive usage of fertilizers and pesticides is resulting in
contamination/mixing of untreated wastewater with the
available water resources (El-sheekh et al. 2000; Ghosh
et al. 2012). The report of World Health Organization
(WHO 2000) and a survey of Central Pollution Control
Board, India (CPCB 2009) stated that only 31 and 35 % of
the total sewage wastewater is treated up to secondary level
in Asia and urban cities of India, respectively, with a
capacity gap of 65–69 %. Further, the presence of excess
nutrients (N and P) in untreated wastewater is resulting in
N. Renuka A. S. Ahluwalia (&)
Department of Botany, Panjab University,
Chandigarh 160014, India
e-mail: aas.aca2012@gmail.com
A. Sood R. Prasanna
Division of Microbiology, Indian Agricultural Research
Institute, New Delhi 110012, India
123
Int. J. Environ. Sci. Technol. (2015) 12:1443–1460
DOI 10.1007/s13762-014-0700-2
eutrophication, algal blooms, uncontrolled spread of cer-
tain aquatic macrophytes, oxygen depletion and loss of key
floral and faunal species, leading to the total degradation of
water bodies (Khan and Ansari 2005). Therefore, there is a
need to identify cost-effective, eco-friendly technologies
that require minimal infrastructure, inputs and simple
know-how, which can be utilized by the common man or
less literate population. These technologies should also be
applicable at the small-scale level with potential of
acceptance at commercial level in the future.
The methods applied in the treatment of effluents or
contaminated water are broadly classified into three
types—physical, chemical and biological (Fig. 1). These
can be employed individually or in combination, depending
upon the extent and type of pollution. In order to achieve
the desired levels of contaminant removal, individual
wastewater treatment procedures are grouped into a variety
of systems, classified as primary, secondary and tertiary
wastewater treatments. In general, both physical and
chemical methods are costly. Also, most chemical methods
increase the pH, conductivity and overall load of dissolved
matter in the wastewater. In this respect, biological or bio-
treatment of wastewater is a better option. The most
common biological wastewater treatment applied in the
treatment of municipal and industrial wastewaters is the
use of activated sludge alone (Nyholm et al. 1996; Rad-
jenovic et al. 2009) or in combination with algae (Gonzalez
et al. 2008; Su et al. 2012a). However, problems related to
dewatering and disposal of sludge have made researchers
look for other alternatives.
Phytoremediation, the use of plants (including algae or
lower plants) and associated microflora for the removal or
biotransformation of pollutants including nutrients, heavy
metals etc. from wastewater seems to be a promising option
(Ali et al. 2013; Franchino et al. 2013; Richards and Mullins
2013; Sood et al. 2012). Oswald and Gotaas (1955) are the
pioneers in this area, especially in terms of illustrating the
potential of algae in the wastewater treatment. Oswald et al.
(1957) reported designs of natural treatment systems
empowered primarily by solar energy, making wastewater
treatment more affordable and sustainable. Wastewater
treatment with microalgae, also referred to as Phycoreme-
diation, is a term coined recently by John (2000), as given
by Souza et al. (2012). Phycoremediation is particularly
attractive because it has the ability to deal with more than
one problem on-site. The promising attributes of microal-
gae, such as (1) higher photosynthetic capabilities as com-
pared to higher plants (Bhatnagar et al. 2011), (2) ability to
convert solar energy and CO
2
emissions from power plants,
hence, lower energy requirements (Razzak et al. 2013), (3)
capacity to incorporate excess nutrients such as nitrogen
and phosphorus from sewage water for their growth, mak-
ing disposal easy (Bhatnagar et al. 2011; Mata et al. 2012),
(4) tolerance to extreme conditions (Makandar and
Bhatnagar 2010), (5) ability to reduce greenhouse gas
emissions (Bhola et al. 2014; Singh and Ahluwalia 2013),
(6) wide applications of harvested biomass (Gupta et al.
2013). These useful features of microalgae have further
strengthened their exploitation in wastewater treatment, as
compared to the use of higher aquatic macrophytes
(Table 1). Therefore, the cultivation of algae in wastewater
offers the combined advantages of mitigation of greenhouse
gases, treatment of the wastewaters, and simultaneously
producing algal biomass. This biomass can be exploited for
multiple uses—as protein supplements and food additives
(animal and human feed), bioenergy resources (biogas and
biofuels), bio-ore for precious heavy metals, pharmaceuti-
cals, cosmetics and other valuable chemicals (Gupta et al.
2013; Pittman et al. 2011; Sahu et al. 2013; Singh et al.
2011; Spolaore et al. 2006).
This review is, therefore, an attempt to summarize the
reports available on the diversity of microalgae in various
wastewaters and critically evaluate their role in wastewater
treatment, besides exploring the potential of wastewaters
for efficient microalgae biomass production. Since, various
microalgae differ in their nutrient sequestration ability and
competitive potential in different wastewaters under natural
environments, the significance of consortial approach is
also discussed.
Microalgal diversity in wastewater
The release of industrial and municipal wastewater poses
serious environmental challenges to the receiving water
bodies (Yang et al. 2008). Wastewater is usually rich in
contaminants in the form of nutrients, heavy metals,
hydrocarbons etc. The presence of nutrients especially
nitrogen (N) and phosphorus (P), in the form of nitrate,
nitrite, ammonia/ammonium or phosphorus in wastewa-
ter leads to eutrophication (Liu et al. 2010;Yangetal.
2008). Microalgae represent an integral part of the
microbial diversity of wastewaters, which can also play a
role in the self-purification of these wastewaters (Sen
et al. 2013).
Microalgae constitute a broad category of organisms
encompassing photoautotrophic eukaryotic microalgae and
prokaryotic cyanobacteria, which are distributed both in
fresh and marine environments, with a wide range of
diversity in their thallus organization and habitat (Lee
2008). The biodiversity of microalgae is enormous and
estimated to be about 200,000–800,000 species, out of
which about 50,000 species are only described (Starckx
2012). This enormous diversity and propensity to adapt to
extreme and inhospitable habitats has led the scientific
community to screen, identify promising strains/species/
genera and develop promising microalgae-based
1444 Int. J. Environ. Sci. Technol. (2015) 12:1443–1460
123
technologies for wastewater treatment (Fouilland 2012).
The available literature relevant in relation to research
undertaken in terms of microalgal diversity in various types
of wastewaters is summarized in Table 2.
Hussein and Gharib (2012) analyzed the phytoplankton
diversity in sewage water mixed with drain water and observed
a total of 152 taxa, including Bacillariophyceae (60), Chloro-
phyceae (20), Cyanophyceae (20), Euglenophyceae (17) and
Fig. 1 Schematic representation of wastewater treatment using microalgae: overview of advantages and applications
Int. J. Environ. Sci. Technol. (2015) 12:1443–1460 1445
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Dinophyceae (9). Bacillariophyta was the dominant group,
constituting 39.4 % of overall diversity in the drain. However,
in an open sewage-contaminated channel, Renuka et al.
(2013a) observed the dominance (58 %) of Cyanophycean
members comprising species of Chroococcus (Fig. 2a, b),
Lyngbya (Fig. 2c) Phormidium (Fig. 2d), Limnothrix
(Fig. 2e), Oscillatoria (Fig. 2f), and Planktothrix (Fig. 2g),
followed by members of Chlorophyta (25 %) and Bacilla-
riophyta (17 %). Bernal et al. (2008) studied the change in
microalgal community in batch reactors of municipal waste-
water treatment containing dairy sewage water and observed
that microalgae from Cyanophyta, Chlorophyta and Eu-
glenophyta groups were present during all the phases of the
treatment process; Arthrospira jenneri (Cyanophyta) and
Coccomonas sp. (Chlorophyta) were the most common
members (Table 2).
In a study on the wastewater treatment plant (WWTP) at
Shimoga Town, Karnataka State, India, seventy-one spe-
cies belonging to Cyanophyceae, Chlorophyceae, Euglen-
ophyceae, Bacillariophyceae and Desmidiaceae were
recorded by Shanthala et al. (2009). Chlorella and Scene-
desmus (Chlorophyta) were the dominant forms throughout
the year, and the high pollution load was observed to have
a negative impact on the total phytoplankton diversity. In
another study from a wastewater stabilization pond, Fur-
tado et al. (2009) isolated ten cyanobacterial genera as the
dominant forms, including Synechococcus, Merismopedia,
Leptolyngbya, Limnothrix and Nostoc, which represented
more than 90 % of the total phytoplankton diversity of
waste stabilization pond, during the periods of summer and
autumn (Table 2).
Cyanobacteria also constitute an important part of the
phytoplankton diversity of WWTP, due to the existence of
warm, stable and nutrient-enriched water (Badr et al. 2010;
Martins et al. 2010; Vasconcelos and Pereira 2001). Va-
sconcelos and Pereira (2001) studied the phytoplankton
communities of two ponds (facultative and maturation) of
the WWTP of Esmoriz (North Portugal) and reported that
cyanobacteria constitute 15.2–99.8 % of the total phyto-
plankton diversity. Among these, Planktothrix mougeotii,
Microcystis aeruginosa and Pseudoanabaena mucicola
were the dominant species (Table 2
). Similarly, in another
report, Badr et al. (2010) noticed that cyanobacteria in
facultative and maturation ponds of WWTP of El-Sadat
city, Egypt constituted 2–97.8 % of the total phytoplankton
density. Martins et al. (2010) isolated 51 strains of cya-
nobacteria belonging to Phormidium autumnale, Plankto-
thrix mougeotii, Limnothrix sp. and Synechocystis sp.
during a 12-month study from WWTP located in the north
of Portugal. Ghosh and Love (2011) reported a high level
of algal diversity comprising diatoms, green algae, cya-
nobacteria, Eustigmatophycean members, and unknown
heterokonts using rbcL gene as a marker, in a wastewater
treatment plant situated at Tampa, Florida and Northfield,
Michigan.
Apart from wastewater treatment plants, reports are
also available on the distribution and diversity of micro-
algae in industrial effluents (Dubey et al. 2011; Vija-
yakumar et al. 2007). Vijayakumar et al. (2007) observed
that among the different effluents studied, cyanobacterial
species comprise 93 % in sugar mill effluent, 91 % in dye
effluent, and 76 and 50 % in paper mill and pharmaceu-
tical effluents, respectively. In all these effluents, the
cyanobacterial genus Oscillatoria was the dominant form,
followed by Phormidium, Lyngbya, Microcystis and Syn-
echococcus (Table 2). Dubey et al. (2011) recorded a total
of 25 species of cyanobacteria in paper mill and phar-
maceutical effluents. Microcystis aeruginosa, Oscillatoria
curviceps, O. princeps, Phormidium ambiguum and
Table 1 Comparison of wastewater treatment potential of microal-
gae and higher aquatic macrophytes
Characteristics Microalgae Higher aquatic
macrophytes
Doubling time Microalgae double their
biomass within
1–2 days
Much higher time is
required by aquatic
macrophytes to double
their biomass
CO
2
sequestration
potential
Much higher
photosynthetic
efficiency provides
them with relatively
higher CO
2
mitigation
potential. Therefore,
help in reduction of
greenhouse effect to
solve the problem of
global warming
Relatively lower
photosynthetic
efficiency hence,
lower CO
2
mitigation
potential
Space
requirement
Smaller dimensions
require less space for
the growth of
microalgae as
monoculture or
consortia
Large size of
macrophytes require
more space for their
maintenance and
growth
Processing Relatively easy to scale
up of process because
they can be harvested
with relative ease
(because of
filamentous nature or
flocculation ability)
Difficult to scale up
process at commercial
levels because of
rooted nature of
macrophytes
Biomass
disposal and
its
applications
Smaller size of
microalgae results in
easy disposal and
transport of biomass
for other
biotechnological
applications from their
site of production to
their utilization sites
Lesser number of
applications of
biomass are explored
as their huge biomass
is difficult to dispose
and transport
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Table 2 Microalgal diversity in selected types of wastewaters
Types of wastewater Geographical region Cyanobacteria Other microalgae References
Drain West of Alexandria,
Egypt
Melosira variance, Cylindrotheca closterium, Cyclotella
glomerata, Cyclotella kuetzingiana, Cyclotella
meneghiniana, Ankistrodesmus falcatus, Skeltonema
costatum, Aulacoseira distans, Acutodesmus acuminatus,
Planktolyngbya limnetica, Pseudoanabaena limnetica,
Lyngbya contorta, Ankistrodesmus falcatus, Merismopedia
punctata, Thalassiosira subtillis
Chlorella vulgaris, Scenedesmus bijugus,
Euglena caudata, Phacus triqueter
Hussein and Gharib
(2012)
Municipal and dairy
wastewater
Central Veracruz,
Mexico
Arthrospira jenneri, Geitlerinema, Synechocystis, Cyanobium
and Glaucospira
Polytomella sp., Polytoma tetraolare,
Chlamydomonas caeca, Carteria sp.,
Lepocynclis ovum and Euglena clavata
Bernal et al. (2008)
Facultative waste
stabilization pond
Sao Paulo State, Brazil Synechococcus sp., Merismopedia sp., Leptolyngbya sp.,
Limnothrix sp., and Nostoc sp.
NA Furtado et al. (2009)
Facultative and maturation
ponds of wastewater
treatment plant
Esmoriz, North Portugal Planktothrix mougeotii, Microcystis aeruginosa,
Pseudanabaena mucicola
, Oscillatoria sp.
NA Vasconcelos and
Pereira (2001)
El-Sadat city, Egypt Oscillatoria spp. NA Badr et al. (2010)
Wastewater treatment plant North Portugal Phormidium autumnale, Planktothrix mougeotii, Limnothrix
sp. and Synechocystis sp.
NA Martins et al. (2010)
Sugar and paper mill, dye
and pharmaceutical
effluent
Tamil Nadu, India Oscillatoria sp., Phormidium sp., Lyngbya sp., Microcystis sp.,
Synechococcus sp.
NA Vijayakumar et al.
(2007)
Paper mill and
pharmaceutical effluent
Madhya Pradesh, India Microcystis aeruginosa, Oscillatoria curviceps, Oscillatoria
princeps, Phormidium ambiguum, Phormidium corium
NA Dubey et al. (2011)
Pulp and paper mill effluent
(secondary treatment
basin)
Brazil, Canada, New
Zealand, USA
Phormidium, Geitlerinema, Pseudanabaena and Chroococcus NA Kirkwood et al. (2001)
Carpet mill effluent Athens, USA Anabaena sp., Aphanocapsa spp., Calothrix braunii, Lyngbya
sp., Nostoc sp., Oscillatoria sp., Limnothrix spp.,
Phormidium sp., Chroococcus sp., Synechocystis sp.,
Chlorella vulgaris, Chlamydomonas sp.,
Scenedesmus spp., Ulothrix
sp.,
Chlorococcum sp., Gloeocystis
vesiculosa, Chlorococcum humicola,
Nitzschia sp., Navicula sp.
Chinnasamy et al.
(2010a)
NA not available
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