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A. Z. Yaser and N. N. Safie
However, microalgae are reported by Aksman and Tukaj (2004) to be sensitive
with hazardous contaminants and special care must be taken to improve the microbial
activity. In addition, the presence of heavy toxic metals like cadmium, mercury or
zinc in industrial wastewater can interfere with the microalgae growth metabolic
pathway (Zhen-Feng et al. 2011). Moreover, nutrients present in wastewater might
support the growth of other microorganisms (fungus, bacteria, protozoa, metazoa and
other microlife) that would compete with the microalgae for nutrients (Gebremedhin
et al. 2018). As a result, one has to consider the composition of wastewater and
optimize it in such a way that it would be more suitable for the enhanced microalgae
biomass yield (Zhang et al. 2014). Furthermore, the optimum biomass concentration
is dependent on the reactor configuration and light intensity whereby higher biomass
concentration is recorded at high light intensity.
Phytoremediation
Phytoremediation has also been used to treat sewage in campus. Phytoremediation is
a well-established environmental protection technique that has received increasing
attention since the term has been coined two decades ago (Vamerali et al. 2010).
According to Susarla et al. (2002), phytoremediation can be accomplished by three
methods of applications which are in situ, in vivo and in vitro. In situ phytoremediation is conducted by placing the selected living plants in the contaminated surface
water, soil, or sediment for the purpose of remediation which is also applied in most
wetland. In vivo phytoremediation is applicable for plants that are inaccessible to
the contaminants such as wastewater in deep aquifer. It is done by transferring out
the wastewater by using mechanical means prior to treatment. The treatment is done
outside by using the living plants and transferred back to its original location. Lastly,
in vitro phytoremediation is done by applying the components of the living plants
instead of the whole living plants, for instance, the extracted enzymes to treat contaminated pond or wetland. Living plants that were used in treating campus sewage
namely Brassica napus (rapeseed), Glycine max (soybean) and Helianthus annuus
(sunflower), and Hymenachne grumosa (Nees) Zuloaga.
The mechanism of phytoremediation is explained by Zhang et al. (2010) whereby
all the contaminants are amenable to one of these actions which are phytoransformations, rhizosphere bioremediation, phytoextraction, rhizofiltration, and phytostabilization. Furthermore, the rate of biodegradation and mineralization of contaminants
during phytoremediation is usually affected by the nature and concentrations of contaminants present as well as surrounding soil/air moisture, pH, temperature, soil
elemental composition, and their bioavailability and the supporting microbial media
(McCutcheon et al. 2008). The advantages and disadvantages of phytoremediation
are tabulated in Table 5.
Wetland is one of the common in situ phytoremediation treatments that are widely
being used. The mechanism of treatment using wetland is contaminant plumes from
the sewage water flow into the wetland may travel downgradient into the ground and
as it approaches shallower depths, the contaminants will encounter the rhizosphere
of upland plant communities in wetland where initial in situ phytoremediation may
occur (Randerson 2006).
A. Z. Yaser and N. N. Safie
However, microalgae are reported by Aksman and Tukaj (2004) to be sensitive
with hazardous contaminants and special care must be taken to improve the microbial
activity. In addition, the presence of heavy toxic metals like cadmium, mercury or
zinc in industrial wastewater can interfere with the microalgae growth metabolic
pathway (Zhen-Feng et al. 2011). Moreover, nutrients present in wastewater might
support the growth of other microorganisms (fungus, bacteria, protozoa, metazoa and
other microlife) that would compete with the microalgae for nutrients (Gebremedhin
et al. 2018). As a result, one has to consider the composition of wastewater and
optimize it in such a way that it would be more suitable for the enhanced microalgae
biomass yield (Zhang et al. 2014). Furthermore, the optimum biomass concentration
is dependent on the reactor configuration and light intensity whereby higher biomass
concentration is recorded at high light intensity.
Phytoremediation
Phytoremediation has also been used to treat sewage in campus. Phytoremediation is
a well-established environmental protection technique that has received increasing
attention since the term has been coined two decades ago (Vamerali et al. 2010).
According to Susarla et al. (2002), phytoremediation can be accomplished by three
methods of applications which are in situ, in vivo and in vitro. In situ phytoremediation is conducted by placing the selected living plants in the contaminated surface
water, soil, or sediment for the purpose of remediation which is also applied in most
wetland. In vivo phytoremediation is applicable for plants that are inaccessible to
the contaminants such as wastewater in deep aquifer. It is done by transferring out
the wastewater by using mechanical means prior to treatment. The treatment is done
outside by using the living plants and transferred back to its original location. Lastly,
in vitro phytoremediation is done by applying the components of the living plants
instead of the whole living plants, for instance, the extracted enzymes to treat contaminated pond or wetland. Living plants that were used in treating campus sewage
namely Brassica napus (rapeseed), Glycine max (soybean) and Helianthus annuus
(sunflower), and Hymenachne grumosa (Nees) Zuloaga.
The mechanism of phytoremediation is explained by Zhang et al. (2010) whereby
all the contaminants are amenable to one of these actions which are phytoransformations, rhizosphere bioremediation, phytoextraction, rhizofiltration, and phytostabilization. Furthermore, the rate of biodegradation and mineralization of contaminants
during phytoremediation is usually affected by the nature and concentrations of contaminants present as well as surrounding soil/air moisture, pH, temperature, soil
elemental composition, and their bioavailability and the supporting microbial media
(McCutcheon et al. 2008). The advantages and disadvantages of phytoremediation
are tabulated in Table 5.
Wetland is one of the common in situ phytoremediation treatments that are widely
being used. The mechanism of treatment using wetland is contaminant plumes from
the sewage water flow into the wetland may travel downgradient into the ground and
as it approaches shallower depths, the contaminants will encounter the rhizosphere
of upland plant communities in wetland where initial in situ phytoremediation may
occur (Randerson 2006).