In only cause harm to human and nature, and

In current world, there are still a lot of countries
facing insufficient safe drinking water issue. In many instances, water is
unsafe to drink due to too high contamination level, even though the quantity
of water is sufficient. Contamination of water supplies can be in various
forms, including inorganic heavy metal pollutants, organic pollutants such as
nutrients and phosphorus which is the main cause of eutrophication, and also
pathogenic organisms. A vital contributor to worldwide water contamination is
nitrogen and phosphorus. They are difficult to control as industrial revolution
is continuously happening all around the world and they contribute to the
common sources of cultural eutrophication. For instance, intensive fertilizer
usage, increasing waste disposal from industries and improper management of
discarded waste. Excessive nutrients in water bodies are critical to plant
growth, but they are toxic to water and can cause severe ecosystem imbalance,
harming aquatic lives.

            Eutrophication
has many negative consequences; one of them is reducing oxygen availability in
water. The growth of plant materials is harmful to a pond system, because of
the domination of the plants, blocking the penetration of sunlight into the
pond to a greater depth. Besides, eutrophication also can cause unpleasant
smells to the surrounding. Not only that, when nitrogen is being converted to
ammonia, it is toxic to aquatic lives. This may cause food web alterations and
imbalance ecosystem nearby. As a result, eutrophied water bodies only cause
harm to human and nature, and the society cannot make use of the water sources.
To reverse this ecosystem change, phytoremediation is a useful and less
expensive way. When compared to chemical and physical approaches, it is more
ecologically advantageous (Schenker & Harfmann, 2010).

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Phytoremediation method make use of
various plants to extract, contain, immobilize, remove or degrade contaminants
from surface water by direct uptake, followed by transformation, transport and
accumulation in a non-phytotoxic form. The diverse approaches in
phytoremediation include phytodegradation, phytoextraction, phytostabilization,
phytovolatilization and rhizofiltration. Phytoremediation is a useful method to
remove nitrogen and phosphorus from water bodies, and in turn played a vital
role in solving eutrophication problem. Phytoremediation is still actively
being researched and plant-microbial associations seem to be the key to enhancing
removal of inorganic and organic pollutants (Singh & Ward, 2004).

Phytoremediation has various
techniques which are applicable in wastewater treatment, in surface water or
groundwater purification. One of them will be phytoextraction. Phytoextraction
allows removal of contaminants from soil, groundwater or surface water, but
with condition that the plants must have high capacity for accumulation of
toxic substances, should grow at fast rate and is able to produce large amount
of biomass. Meanwhile, phytodegradation also limited to plants which are able
to produce enzymes that catalyze the degradation reactions of xenobiotics.
Phytodegradation may occur within or outside of the plant while the plant
produces, and secretes the enzyme into the soil of the root zone. This
technique can be applied on the treatment of soil, river sediments as well as
surface water.  Besides,
phytovolatization technique uses plants to absorb contaminants from the water,
then metabolize and release them to the atmosphere as volatile and less toxic
gases. Other than that, rhizofiltration as known as phytofiltration is used for
the treatment of surface water mainly produced by industry or agriculture. The
conditions for this technique include the plants should be highly tolerant to
high concentration of toxic substances, resistant to low oxygen concentration
and having extensive root system. This technique is mainly used in the removal
of heavy metals (Materac, Wyrwicka & Sobiecka, 2015).

In recent years, floating
macrophytes have been actively used in water bodies to remove effluents and to
achieve secondary treatment effluent quality from primary sewage effluent. This
phytoremediation technology is new yet interesting as it potentially plays
important roles in nutrient uptake and has great effect towards the biomass and
biochemical content. Macrophytes are aquatic plants that dominate wetland,
shallow lakes, and ponds. They can be emergent, submerge or floating on the
surface water. They take an important role in healthy ecosystems by acting as
primary producers of oxygen through photosynthesis, helping nutrients recycling
to and from sediments, providing shelter for fish and many invertebrates. Moreover, scientists surprisingly found another great value of
macrophytes in recently years which is serves as a potential phytoremediator in
water bodies or soil. They grow on water with relatively high levels of
nitrogen, phosphorus, potassium and concentrate the minerals then accumulate
high nutrients concentration in the plant.

Metabolic
functions of these aquatic plants including nutrient uptake and oxygen release
from roots into the rhizosphere. To be well adapted to
anaerobic conditions, macrophytes developed internal air sacs (aerenchyma) that
transport oxygen to the root zone. Researchers believe that the aquatic plants
are able to release the oxygen from roots to surrounding rhizosphere and
providing aerobic conditions for incidence of nitrification (Reddy,
Patrick & Lindau, 1989). These aquatic macrophytes are important in
maintaining the healthy community of aquatic environments.

The macrophytes ability and
capability in the nutrient removal from water bodies are currently a concern
among the researchers since the last two decades. One study demonstrated the
nitrate removal efficiency from synthetic medium and groundwater in different
areas in India (Ayyasamy et al., 2009). In their study, water hyacinth,
water lettuce and Salvinia were used. Water hyacinth achieved
high nitrate removal efficiency of 83% in synthetic medium with initial nitrate
concentration of 300 mg/l. This efficiency decreased as the initial
nitrate concentration increased as the osmotic pressure at higher concentration
suppresses the uptake of the nitrate. Water lettuce and Salvinia showed
lower nitrate removal efficiencies in the same medium. In another research in
China, Xu and Shen found that the duckweed, Spirodela oligorrhiza system
was able to remove 83.7% total nitrogen and 89.4% of total phosphorus from
swine lagoon water in eight weeks at a harvest frequency of twice a week. Total
biomass harvested achieved 5.3 times that of the starting amount. 

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