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International Journal of Advancements in Research & Technology, Volume 2, Issue 7, July-2013 211 ISSN 2278-7763 Copyright © 2013 SciResPub. IJOART Petrochemical Industrial Waste: Bioremediation Techniques An Overview Sheetal Koul and MH Fulekar * Department of Life Sciences, University of Mumbai, Santacruz (E), Mumbai- 400 098, India * School of Environment and Sustainable development, Central University of Gujarat, Gandhinagar – 482030, India * Email:
[email protected] ABSTRACT The petrochemical industry is one such major source of hazardous waste, produced during manufacture of Petrochemical products. These wastes are often released in the environment. Petrochemical Solid waste is generally associated with more hazardous constituents and accordingly carries a higher level of public health and environmental risk potential. In the present paper the petrochemical waste compound in particular Polycyclic Aromatic Hyrocarbons (PAH) were described as persistent pollutant in soil-water environment. The microbial sources which have been found and reported for PAH compound degradation have been cited with examples viz: potential species of Bacteria, species of Fungal and actinomycetes have been described for microbial degradation. The factors influencing microbial degradation including the influence of GMO’s on bioremediation have been cited in the paper. This would serve as a bioremediation technique for microbial degradation of petrochemical waste. Keywords: Bioremediation, Polycyclic Aromatic Hydrocarbons’ (PAH), Petrochemical Solid waste, GMO’s International Journal of Advancements in Research & Technology, Volume 2, Issue 7, July-2013 212 ISSN 2278-7763 Copyright © 2013 SciResPub. IJOART 1. Introduction: The persistence of a pollutant in the environment is influenced by the nature of the contaminant, the amount of the contaminant present and the interplay between chemical, geological, physical and biological characteristics of the contaminated site. In the present era, petroleum hydrocarbon contamination is considered a major widespread environmental problem distributed in atmosphere, terrestrial soil, marine waters and sediments [1]. Anthropogenic activities which include improper management and disposal of oil sludge waste results in leaks and accidental spills during the exploration, production, refining, transport and storage of petroleum products. Polycyclic aromatic hydrocarbons (PAHs) are one class of toxic environmental pollutants and perhaps the first recognized environmental carcinogens that have accumulated in the environment whether accidentally or due to human activities [2]. Polycyclic aromatic Hydrocarbons (PAHs) are fused ring hydrocarbon compounds that are highly recalcitrant under normal conditions due to their structural complexity, strong molecular bonds, low volatility and aqueous solubility and high affinity for soil material and particulate matter [3]. Overtime, they accumulate in the surrounding soil sediments and ground water causing extensive damage to animal tissues due to their carcinogenic, mutagenic and potentially immune toxicant properties. [4], [5]. Although in the natural environments they are readily degraded by indigenous microbial communities, these processes are very time consuming. Various physical and chemical applications like mechanical burying, evaporation, dispersion and washing are currently employed to remediate the problems caused by PAHs pollution. However, these forms of treatments are either expensive or can lead to incomplete decomposition of contaminants [6]. The process of bioremediation, defined as the use of microorganisms to detoxify or remove pollutants owing to their diverse metabolic capabilities is an evolving method for the removal and degradation of many environmental pollutants including the products of petroleum industry [7]. In addition, bioremediation technology is believed to be non-invasive and relatively cost effective [8]. Bioremediation by natural populations of microorganisms represents one of the primary mechanisms by which petroleum and other hydrocarbon pollutants can be removed from the environment [9] and is cheaper than other remediation technologies [10].The success of PAH degradation and bioremediation depends on one’s ability to establish and maintain conditions that favour enhanced oil biodegradation rates in International Journal of Advancements in Research & Technology, Volume 2, Issue 7, July-2013 213 ISSN 2278-7763 Copyright © 2013 SciResPub. IJOART the contaminated environment which include the employment of correct population of microorganism [3] with the appropriate metabolic capabilities [6] and ensuring adequate concentration of nutrients, oxygen and optimal pH and temperature [11],[12],[13],[14],[15].The characterization of novel catalytic mechanisms, physiological adaptations of microbes, biochemical mechanisms involved in hydrocarbons accession, uptake and the application of genetically engineered and enhanced microbes for bioremediation are the recent advances employed in the removal of persistent organic pollutants like PAHs. Therefore, the intent of this review is to update information on microbial degradation of Polycyclic Aromatic Hydrocarbons towards the better understanding in bioremediation challenges. 2. Polycyclic Aromatic Hydrocarbons (PAHs) 2.1 Physical and chemical properties : Polycyclic Aromatic Hydrocarbons or PAHs as they are fondly called are chemical compounds made up of two or more fused benzene rings [3] and some “Penta-cyclic Moieties” in linear, angular, and/or cluster arrangements [16]. Many PAHs contain a “bay-region” and a “K-region”. The bays-and K-region epoxides, which can be formed metabolically, are highly reactive both chemically and biologically. Phenanthrene is the simplest aromatic hydrocarbon which contains these regions. The bay-region of phenanthrene is a sterically hindered area between carbon atom 4 and 5 and the K-region is the 9, 10 double bond [17] According to the Schmidt-Pullman, electronic theory K-region epoxides should be more Carcinogenic than the parent hydrocarbon.[17]. PAHs generally accumulate in the environment because they are thermodynamically stable compounds, due to their large negative resonance energies; they have low aqueous solubility’s and they absorb to soil particles [16].Generally solubility decreases and hydrophobicity increases with an increase in number of fused benzene rings also volatility decreases with an increasing number of fused rings [18] High molecular weight [HMW] PAHs (four or more rings) sorb strongly to soils and sediments and are more resistant to microbial degradation. Because of solid state, high molecular weight and hydrophobicity expressed as its log P value between 3 and 5, PAHs are very toxic to whole cells [19]. International Journal of Advancements in Research & Technology, Volume 2, Issue 7, July-2013 214 ISSN 2278-7763 Copyright © 2013 SciResPub. IJOART Figure1 . PAHs representatives and their chemical structures [17] Table 1. Structure and physical-chemical properties of some three-, four-, five- and six-ring polycyclic aromatic hydrocarbons . [20] a mp: melting point; b bp: boiling point; c Sol: aqueous solubility. d log K p : logarithm of theoctanol:water partitioning coefficient. PAH No. of rings mp a ( o C) bp b ( o C) Sol c (mg l -1 ) log K p Vapour pressure (torr at 20( o C) Phenanthrene 3 101 340 1.29 4.46 6.8 x10 -4 Anthracene 3 216 340 4.45 0.07 2.0 x 10 -4 Fluoranthene 4 111 250 0.26 5.33 6.0 x 10 -6 Benz[a ]anthracene 4 158 400 0.014 5.61 5.0 x 10 -9 Pyrene 4 149 360 0.14 5.32 6.8 x 10 - Chrysene 4 255 488 0.002 5.61 6.3 x 10 -7 Benzo[a ]pyrene 5 179 496 0.0038 6.04 5.0 x 10 -7 Dibenz[a,h]anthracene 5 262 524 0.0005 5.97 1.0 x 10 -10 Benzo[g,h,i]perylene 6 222 - 0.0003 7.23 1.0 x 10 -10 Indeno[1,2,3-c,d ]pyrene 6 6163 536 0.062 7.66 1.0 x 10 -10 International Journal of Advancements in Research & Technology, Volume 2, Issue 7, July-2013 215 ISSN 2278-7763 Copyright © 2013 SciResPub. IJOART 2.2 Production, Occurrence and Toxicity of PAHs The major source of PAHs is from the incomplete combustion of organic material (Guerin & Jones., 1988). PAHs are formed naturally during thermal geologic production and during burning of vegetation in forest and bush fires [21].In Industrial countries, anthrogenic combustion activities are a principal source of PAHs in soils where they arise from atmospheric deposition [22]. PAHs have been detected in a wide variety of environmental samples including air [23],soil [22], sediments [24],water, oils, tars and foodstuff [25], [26].Oil leakage from storage tank bottoms, oil-water separators, and drilling operations etc. has led to an increase in soil PAH concentration over the last few decades [17] PAHs are also a major constituent of Creosote (approximately 85% PAH by weight) and anthracene oil, which are commonly used pesticides for wood treatment. [27].These contaminated soils vary in hydrocarbon composition. Table2 . Characteristics of a typical PAH-contaminated soil [28]. PAH-Contaminated areas pose a health risk to humans [29]. One-, two and three-ring compounds are acutely toxic [20]. Low Molecular weight PAH pollutants exert toxic,
