Treated effluents become one of the most significant sources for irrigation and other activities in arid and semi-arid countries such as Oman. There are many conventional methods to deal with the heavy metals and toxic chemicals that are present in the effluents. Bioremediation is one of the methods to treat the effluents. Bioremediation is a process in which the heavy metal content present in the contaminated water is removed using microorganisms like algae or bacteria. This project is an attempt to remove heavy metals like calcium, magnesium and copper using algae from different sites in Oman. The research studies states that the bioremediation using algae is an environment friendly method to treat the heavy metals present in contaminated water. The sorption of metal by the algae is tested using pH meter, Fourier Transform Infrared Spectroscopy, Atomic Absorption Spectrometer and potentiometric titration process. The data obtained from these tests are depicted in graphs to do the comparison and obtains the desired results. The adsorption isotherm graphs will show the metal uptake by the algae over certain interval of time. Thus, this project will be an innovative method to deal with the heavy metals present in water as it is eco-friendly treatment process.
Key words: Treated effluent; conventional method; heavy metals; bioremediation; microorganism; algae; calcium; copper; magnesium; environment friendly; sorption; adsorption isotherm; Oman <>INTRODUCTION
Heavy metals at higher concentration that are present in the aquatic ecosystem will result in contaminating the water, which is considered to be a vital world-wide concern. The water ions that are present in the aquatic system constitutes of heavy metal ions which is toxic and it could be easily absorbed by the human body through the food chain in the ecosystem. There are many conventional methods used to prevent the contamination of heavy metals in the environment. These conventional methods have drawbacks that include incomplete removal of heavy metal, generates toxic sludge and cost inefficiency. The uptake of metal ions by the algae species have been studies for some years. Research studies proves the ability of algae to accumulate the metal ions. Based on the studies and technology related to bioremediation of metal using living and non-living algae has gained more attention due to its cost efficiency and eco-friendly factors. There are some technology like High Rate Algal ponds and Algal Turf Scrubber that are implemented in China and other countries, but still the limitations for big scale application is a concern. This clean up technology primarily depends on ability of bioaccumulation and biosorption of algae which is dominated by the bioremediation process. To determine the metal-algae interactions, there are various adsorption models to represent the potentiality of metal uptake. From the research studies using various algae species for the bioremediation of metal proved as a better metal removal method compared to other conventional methods. However, there are few drawbacks regarding its mechanism and bioremediation applications.
In this project, Copper, Magnesium and Calcium are the heavy metals that gets absorbed by the algae. These heavy metals are mainly present in the effluent from industry as well as in seawater. These metals are essential constituents but in higher concentrations, it adversely affect the aquatic ecosystem and indirectly affect the human health.
In this project, firstly the algae is collected from the site and the identification and analysis of the specie is done. The algae is purified for the bioremediation process. The sorption experiment is carried at different concentration of the metal, 20ppm, 50ppm, 90ppm, 130ppm, 180ppm, 220ppm and CONTROL. The pH of the metal solution is noted at different interval of time, 20mins, 60mins, 1day, 3day and 5day. The comparison will determine the decrease in metal concentration and thus depict the metal ion uptake. The metal concentration in the solution is obtained with the help of atomic absorption spectrometer. The potentiometric titration of the metal solution also been carried out. The data analysis is done using adsorption isotherm. The below chapters include the literature review of past research studies, the experiment methodology, and the future works of the project.
One of the major factor in the adsorption process is pH. Depending on the pH value, the availability of free sites can be determined. With the increasing pH value, the surface charge sites of the metal-algae solution becomes more negative, thus the metal ion uptake increases with increase in pH. Some of the experimental studies have found that with the increase in pH, more negative sites become available for sorption of metal ions, so the metal removal are increased at higher pH, and the pH increases from 0.1-1 unit during the adsorption process (in the case of Cu ions). In this experiment it was found that the increase of metal removal with increased pH was not observed. But there are other experiments were the results were positive. pH meter is a device used to determine pH of a solution. It consists of an electrode linked to an electronic meter that measure and display the pH value.
The sorption of metal ion by the algae is determined using Atomic Absorption Spectrometer (AAS) equipment. With the help of AAS, the concentration of the dissolved metal can be determined based on its absorbance. The experiment is carried for days to compare the concentration degradation. The efficiency of the metal dissolved was calculated using the below equation,
Where, R- removal of metal dissolved, % and Co and Cf are the initial and final concentrations of the heavy metal present in the solution respectively, mg/L.
In this project, bioremediation method is used to remove the heavy metal like Ca, Mg and Cu. Bioremediation is a process where microorganisms like algae or bacteria is used for the removal of heavy metals. The following are the tests to be conducted in this project:
a) Sorption experiments using lab apparatus
The metal uptake by the algae is calculated using pH meter. The pH of the metal solution with the algae is taken at intervals of 20mins, 60mins, 1day, 3days and 5days.
b) Potentiometric titration
The pH of the solution is calculated in an acidic and basic medium over certain interval of time 20mins, 60mins, 1day, 3 days and 5 days.
c) Atomic Absorption Spectrometry Analysis
The filtrate from the sorption experiment test solutions are taken for AAS analysis to obtain the metal uptake.
d) FTIR analysis.
The residue from the centrifugation process is used for FTIR analysis. This analyses the metal uptake by the algae based on its wavenumber.
The overall methodology of this project is shown below:
Project methodology chart.
This project is an effort to provide a solution to the wastewater treatment in Oman. Wastewater treatment is an urgent need for Oman due to its population and the increasing amount of effluents due to the increase in number of manufacturing companies been established in Oman. The bioremediation method to treat the heavy metal is less expensive and an environmentally viable process. The project analyzes the metal uptake by different algae that are been collected from different sites in Oman. The analysis is carried out using an experimental setup to obtain various parameters. The data obtained from the experimental tests are expressed in adsorption isotherm and graphs. The graphs are further studied and the desired results are obtained after comparison. Past research studies are been used to validate the research study in this project. Previous studies show that bioremediation using algae is more convenient method compared to other conventional treatment process. Due to its cost efficiency and environment friendly factors, the process is a positive highlight compared to other conventional methods.
The future works regarding the project include:
a. Identification of other algae and prepare research study to obtain the suitable species for treatment process
b. Comparison of research studies to obtain the optimum result
c. Study on the cultivation of the algae species
d. Prepare a design for small scale or large scale treatment process
BIBLIOGRAPHY Dwivedi, Seema. 2012. Bioremediation of Heavy Metal by Algae: Current and Future Perspective. Research Article. 3 (1-3-July). p. 195-199
Kumar, J.I., et.al 2012. Removal of heavy metals by bosorption using freshwater alga Spirogyra Hyalina. Journal of Environmental Biology[e-journal]. 33 27-31.Available from: www.jeb.co.in. [Accessed:25th November 2014].
Levinson, R., n.d. Atomic Absorption spectrometry. [Online]. Available from: http://www.kau.edu.sa/Files/130002/Files/6785_AAs.pdf. [Accessed: 2nd January 2015].
Zhou, Guang-Jie. et.al., 2012. Biosorption of zinc and copper from aqueous solutions by two freshwater green microalgae Chlorella pyrenoidosa and Scenedesmus obliquus. Environmental Science Pollution Research Article. 19 (2). p. 2918–2929
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