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Comparision of phytoremediation with bioremediation for atrazine removal from waste water.

Introduction

Pesticides being used in agricultural tracts are released into the environment and come into human contact directly or indirectly, results in acute and chronic health problems. Many common farm and household products may be classified as hazardous. These wastes, if improperly used, degraded or disposed of can be harmful to human and animal health and can contaminate ground and surface water. Minimizing the amounts of hazardous products in households and on farms, along with practicing proper use and degrading methods, can reduce health risk, financial liability and potential ground and surface water contamination. Atrazine (2-chloro-4-ethylamino-6-isopropylamino1,3,5-triazine). Both soil organic matter and clay minerals are effective sorbents for atrazine. The treatment of environmental problems through biological means is known as bioremediation and the specific use of plants is known as phytoremediation. Atrazine is one of the toxic pesticides that are found frequently in ground water. The main objective of the present study is to remove atrazine from water to a maximum efficiency. For this atrazine is subjected to phytoremediation i.e. removal by using a plant and to bioremediation i.e. subjecting it to microbial degrading. The efficiencies from both the technique is compared to derive an efficient technique that remove Atrazine to a maximum.

Phytoremediation

Phytoremediation is a general term used to describe various mechanisms by which living plants alter the chemical composition of the soil matrix in which they are growing. Essentially, it is the use of green plants to clean-up contaminated soils, sediments, or water. Phytoremediation is the technical term used to describe the treatment of environmental problems through the use of plants [5].

Bioremidiation

Bioremediation can be defined as any process that uses microorganisms or their enzymes to return the environment altered by contaminants to its original condition. Bioremediation may be employed in order to attack specific contaminants or a more general approach may be taken [3]. These bioremediation and biotransformation methods endeavour to harness the astonishing, naturally occurring, microbial catabolic diversity to degrade, transform or accumulate a huge range of compounds including hydrocarbons, polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), pharmaceutical substances, radionuclides and metals [2].

Materials

Sweet Flag

Sweet flag Acorus calamus is a native of Asia and North America, is known as Vacha in Sanskrit and Vasampu in Tamil. The plant is an aromatic, semi-aquatic herb with a long creeping underground rhizome producing erect, 0.5-1 meter long, linear, sword-like leaves. The rhizome is pale pink internally and contains an essential oil responsible for its medicinal value [7]. Acorus calamus is a perennial, semi-aquatic and smelly plant, found in both temperate and sub temperate zones.

Atrazine

Atrazine is the flagship of the triazine class of herbicides, which includes cyanazine and simazine. Registered in 1958, it has become the most widely used herbicide on corn and sorghum. Atrazine premixes for effective and economical weed control.

Water Sample

The water sample for the performance is prepared in the laboratory itself. Small quantity of atrazine is mixed in a liter of distilled water that is sterilized in the laboratory. About 20ml of distilled water is taken in a flask and it is sterilized and a calculated amount of atrazine solution prepared before is added to each the required flask to get an atrazine concentration of 5mg/l to9mg/l .since industrial water contain only trace amount of atrazine its difficult to collect samples for the needed concentration we prepare it in the laboratory.

Analytical Measurements

Samples resulting from each of the treatment were analyzed for atrazine concentration using high performance liquid chromatography (HPCL). The instrument was calibrated with standard solution. The initial concentrations are noted primarily while conducting the experiment and the final concentration of the samples were measured by using high performance liquid chromatography (HPCL) [8]. The difference between the concentrations gave the removal efficiency.

Experimental Work

From the root zone of sweet flag a pinch of soil is taken and mixed in water, serially diluted and plated in an agar medium for isolating microorganism. This is shown in figure 1 .Then the bacteria is cultured in a minimal culture containing salt alone and no growth promoting nutrients, to see the capability of the organism to gain their energy from that salts alone and to confirm that they are enzyme producing organisms capable of deriving their energy from their surrounding. Then a known concentration of atrazine is added in the minimal culture and the isolated microbes are cultured in these medium to isolate that specific micro organism that can degrade the pesticide. Then they are subjected to a test (hydrogen per oxide test) to see weather it's a pathogenic or a non pathogenic organism.

The isolated organism is cultured in a media having the atrazine pesticide in different concentration and at different pH .The experiment is conducted under room temperature and at normal pressure .The sample is allowed for the growth for 15days in a shaker and this has been shown in figure 2. The turbidity of culture is viewed in a turbidity meter .The maximum turbid culture indicates that cell growth is maximum. From this we can conclude that atrazine is effectively utilized (degraded) for their metabolic path. For the analysis of atrazine and its metabolites HPLC [8]. Then the culture is subjected to concentration analysis using HPLC. The graph we get from the HPLC analysis shows the concentration of atrazine remaining in the culture and the efficiency of atrazine removal in each culture is calculated. The concentration of atrazine that is effectively degraded in bioremediation is taken as the atrazine concentration to perform phytoremediation. The arrangement for phytoremediation is shown in figure 7.

Result and Discussion

The results are shown in figures 3 to 5. Figure 3 shows the colonies of microorganism isolated from sweet flags root and figure5 shows the species responsible for atrazine degradation. They are isolated through a series of procedure. The table 1 to 5 shows the degradation result for bioremediation for different pH. Table 6 shows the atrazine removal result through phytoremediation. They are obtained by the graph got by HPLC analysis.

Modeling Using Analysis Moment Structure (AMOS)

AMOS is a combination of multiple regression, ANOVA and factor analysis. Here Maximum Likelihood Estimates is used for the iteration process. It is developed in United Kingdom. We conclude that the model developed is perfect if the root mean square error (RMSEA) is less than 0.05. As we get in the software we have to open the data in excel form. Then click variables in model. Then we have to drag the parameters into the rectangles and the connectivity is made using arrows between the parameters. Then we have to execute the software. If the red icon glows during the execution we can conclude that the model is fit. This is also used as a tool to check weather the experimental values are correct or they are fake. Figure 6 shows the pictorial model for atrazine degradation from AMOS software. From these it is clear that the pH influences the efficiency more compared to concentration.

Conclusion

The degradation of atrazine is about 80% from bioremediation technique and 23% from phytoremediation. Bioremediation technique is effective in removing atrazine. At a room temperature and under normal pressure degradation of atrazine is maximum at pH 6 for an optimum concentration of 5mg/L. By using the experimental data from bioremediation a pictoral model is performed using AMOS .This shows that pH influence the efficiency. Because the pH decreases (acidic) the growth of organism is affected and at a higher pH (alkaline) the atrazine precipitates at the bottom. Precipitation of atrazine can be over come by using solvent like chloroform, n-pentane etc in which atrazine solubility is more thus increasing their removal. If mixed culture is used the metabolites of atrazine will be utilized by other species in the media and the degradation will be increased a fold higher.

Though there are other methods of degradation of atrazine is there, the chlorination method has 95% removal efficiency, it will remain in water (waste) and further action is blocked since the chlorine will disinfect the waste water. so I suggest bioremediation is the effective method of degrading the atrazine. The identification of genes involved in the detoxification of the pesticide within the plant and the identification of the strain that effectively degrades the atrazine that has been isolated from the rhizobium of the plant with the knowledge of the degradation path involved and knowing that the end product or the intermediate product of degradation is non toxic, recombinant strains can be produced through recombinant DNA technology. These technologies will prove useful in environmental cleanup procedures and subsequent restoration of soil fertility.

The understanding of the basic mechanism involved in atrazine uptake, transport, accumulation and detoxification in plants together with its physiological effects is necessary for the phytoremediation of the atrazine-polluted environments using molecular and genetic techniques. These approaches may include the identification of hyper accumulators that can provide efficient phytoremediation of atrazine-polluted soils, the study of biochemical and molecular responses of these plants to atrazine.

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Reference

[1] National Academy of Sciences. "Drinking water and health." Vol. 1.U.S. National Research Council, Washington, DC. p. 533 (1977).

[2] A l Juhasz , G a Stanley , M L Britz (1977) "Microbial degradation and detoxification of high molecular weight polycyclic aromatic hydrocarbons by Stenotrophomonas maltophilia strain VUN 10,003". Bioremediation. Springer Netherlands publication vol 3 pg.234-241

[3] Sundar (1992) "Environmental degradation of chromium by microbes isolated from the chromium affected site"

[4] Pranab Kumar Ghosh and Ligy Philip "Environmental significance of Atrazine in aqueous system and its removal by biological process and Atrazine degradation in anaerobic environment by mixed microbial culture" dated on 01/02/06

[5] Erakhrumen, Andrew Agbontalor "Phytoremediation: an environmentally sound technology for pollution prevention, control and remediation "Department of Forest Resources Management, University of Ibadan, Ibadan, Nigeria.

[6] Worthing, C.R. and Walker, "The pesticide manual: a world compendium. 8th edition. British Crop Protection Council (1987)".

[7] Agro bios ((vol no: 1 editor:Dr.s.s.purohit Jan 2003).

[8] Helena Prosen "Determination of Atrazine and its metabolites in soil using high performance liquid chromatography" Faculty of Chemistry and Chemical Technology, University of Ljubljana, dated on 19/03/2004

T. Sekar (1), S. Arunthathi (2) and M. Suresh karthik kumar *

(1) Prof. & Head, Lecturer (2) and PG Student (3) Dept. of Civil Engg, Kalasalingam University, Srivilliputtur--626 190 Tamil Nadu

E-mail: kareshmkumar@gmail.com
Table 5: Result of biodegradation of Atrazine

pH = 5                            No of Days = 15
Form of atrazine = Powder       Solvent = Methanol

Initial            Peak Area    Final Concentration      Removal
Concentration of   from Graph   of Atrazine (Mg/l)    Efficiency (%)
Atrazine (Mg/l)

3                    129.26            1.04               65.33
4                    177.73            1.43               64.25
5                    226.20            1.82               63.60
6                    292.07            2.35               60.83
7                    359.19            2.89               58.71

pH = 6                            No of Days = 15
Form of atrazine = Powder       Solvent = Methanol

Initial            Peak Area    Final Concentration      Removal
Concentration of   from Graph   of Atrazine (Mg/l)    Efficiency (%)
Atrazine (Mg/l)

3                    73.482            0.591              80.29
4                    98.726            0.794              80.14
5                   123.877            0.996              80.06
6                   150.368            1.209              79.84
7                   180.945            1.455              79.20

pH = 7                            No of Days = 15
Form of atrazine = Powder       Solvent = Methanol

Initial            Peak Area    Final Concentration      Removal
Concentration of   from Graph   of Atrazine (Mg/l)    Efficiency (%)
Atrazine (Mg/l)

3                    76.38             0.614              79.51
4                   109.864            0.883              77.90
5                    140.45            1.130              77.39
6                    189.75            1.526              74.55
7                    229.30            1.844              73.64

pH = 8                            No of Days = 15
Form of atrazine = Powder       Solvent = Methanol

Initial            Peak Area    Final Concentration      Removal
Concentration of   from Graph   of Atrazine (Mg/l)    Efficiency (%)
Atrazine (Mg/l)

3                    95.70             0.770              74.33
4                    128.01            1.029              74.25
5                    161.17            1.296              74.06
6                    211.28            1.699              71.66
7                    254.78            2.049              70.71

pH = 9                            No of Days = 15
Form of atrazine = Powder       Solvent = Methanol

Initial            Peak Area    Final Concentration      Removal
Concentration of   from Graph   of Atrazine (Mg/l)    Efficiency (%)
Atrazine (Mg/l)

3                    107.88            0.868              71.06
4                    145.41            1.17               70.75
5                    185.18            1.49               70.20
6                    224.95            1.81               69.83
7                    265.97            2.14               69.42

Table 4.7 : Phytoremediation of atrazine

No of Days = 25   Form of atrazine = aqueous       solvent =
                  water

Total Amount Of       Atrazine       Atrazine   Atrazine Utilized
Atrazine (Mg/L)   Retained In Soil   Drained      By Vasa Plant
                       (Mg/L)         (Mg/L)         (Mg/L)

5                        2             1.85           1.15
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Article Details
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Author:Sekar, T.; Arunthathi, S.; kumar, M. Suresh karthik
Publication:International Journal of Applied Environmental Sciences
Article Type:Report
Date:Sep 1, 2008
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