Green Buffalo.
Phytoremediation Plants
All over the Houston area, as Harvey's floodwaters receded, they left behind sludge – a mix of grit and debris picked up from streets and sewers and eroded bayou banks. [1] This has been a recent problem that has impacted the bayou. As a solution, the use of aquatic plants to purify water, but further in the research, treating the surroundings with living green plants will also help to reduce the problems of contamination in Buffalo Bayou. One way not only treat the water, but also the land is implementing Phytoremediation plants.
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Phytoremediation is a generic term for the group of technologies that use plants for remediating soils, sludges, sediments and water contaminated with organic and inorganic contaminants [2]. Plants have evolved a great diversity of genetic adaptations to handle the accumulated pollutants that occur in the environment. Growing and, in some cases, harvesting plants on a contaminated site as a remediation method is a passive technique that can be used to clean up sites with shallow, low to moderate levels of contamination [3]. Plants that are identified as degrading species are then evaluated in controlled greenhouse and field experiments. A second approach is to use axenically cultured plants to eliminate the possibility that microorganisms associated with the plant are responsible for the degradation. To date several plants (aquatic and terrestrial) have been identified as containing the enzyme that reacts to degrade 1,3,5-trinitrotoluene (TNT), a munition that contaminates many military sites. Another study has shown that many aquatic and land plants can degrade chlorine compounds. Still other plants including parrot feather Mariophyllum aquaticum), duckweed (Spirodela oligorrhiza), and elodea (Elodea canadensis) have been shown to uptake and degrade organophosphate compounds such as pesticides to innocuous products [4].
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Figure 1 Approach for sustainable water treatment & management
There are several different types of phytoremediation mechanisms that can be implemented in the bayou.
These are:
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1. Rhizosphere biodegradation. In this process, the plant releases natural substances through its roots, supplying nutrients to microorganisms in the soil. The microorganisms enhance biological degradation.
2. Phyto-stabilization. In this process, chemical compounds produced by the plant immobilize contaminants, rather than degrade them.
3. Hydroponic Systems for Treating Water Streams (Rhizofiltration). Rhizofiltration is like phyto-accumulation, but the plants used for cleanup are raised in greenhouses with their roots in water. This system can be used for ex-situ groundwater treatment. That is, groundwater is pumped to the surface to irrigate these plants. Typically, hydroponic systems utilize an artificial soil medium, such as sand mixed with perlite or vermiculite. As the roots become saturated with contaminants, they are harvested and disposed of.
4. Phyto-volatilization. In this process, plants take up water containing organic contaminants and release the contaminants into the air through their leaves.
5. Phyto-degradation. In this process, plants metabolize and destroy contaminants within plant tissues.
6. Hydraulic Control. In this process, trees indirectly remediate by controlling groundwater movement. Trees act as natural pumps when their roots reach down towards the water table and establish a dense root mass that takes up large quantities of water. A poplar tree, for example, pulls out of the ground 30 gallons of water per day, and a cottonwood can absorb up to 350 gallons per day.
There are still many questions arises regarding affectivity of the phytoremediation process. The product produced during degradation may be accumulated in the animals via food materials obtained by plants or it may be again stored in ground water, as atmospheric layer stored the degraded materials for short vial and via rain water it may again store in ground water. The toxic effect remediation of contaminants through the phytoremediation process is still has many concerns.
The potentiality of the phytoremediation has some limitations, as the tree or plants roots how much extended in the deep and absorb contaminants from there is doubtful. The effectiveness mainly limits to surface or shallow soils and stream water.
In case of ground water treatment, pumping method is needed to collect the water, which is also added cost. In case of deep penetration, it is suggested that the usages of tree are more effective than plants, as the roots of trees are extended much than the plant [6].
Plants That Can Be Used For Phytoremediation:
1. Indian mustard (Brassica juncea L.) Info: Brassica juncea (L.) Czern. – Indian Mustard 2. Willow (Salix species). (White Willow)
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3. Indian grass (Sorghastrum nutans) 4. Sunflower (Helianthus Annuus L.) (Helianthus annuus L. common sunflower)
