Study of Enhanced Bioremediation in Treatment of Gas Condensates Contaminated Soil

Transcription

1 Iranian Journal of Chemical Engineering Vol. 9, No. 4 (Autumn), 2012, IAChE Study of Enhanced Bioremediation in Treatment of Ga Condenate Contaminated Soil J. Shayegan, A. Babaee School of Chemical and Petroleum Engineering, Sharif Univerity of Technology, Tehran, Iran Abtract In recent decade, large amount of hydrocarbon derivation have contaminated the environment due to indutrial development and neglecting the environmental iue. In thi tudy, the ability of biological removal of hydrocarbon pollution from contaminated oil around Sarkhun ga refinery wa invetigated. Thi tudy wa done for even ample with three different nutrient ratio and by moiture controlling and continuou aeration. During experiment, concentration of Total Petroleum Hydrocarbon (TPH) wa meaured. eult howed that with a nutrient ratio of 100:5:1 for C:N:P during an 18-day remediation period, the mean contaminant removal wa about 50%. By uing thee reult a practical plan wa uggeted for running in real cale ituation. Developing a model wa done by conidering the Monod model a microbial growth model. eult howed good accordance to empirical data. Keyword: Enhanced Bioremediation, Contaminated Soil, TPH, Ga Condenate, Sarkhun Ga efinery, Monod model 1. Introduction Hydrocarbon contamination reult from leakage of aboveground and underground torage tank, pillage during tranport of petroleum product, petroleum and ga refinerie, and other accidental releae. Petroleum contain hazardou chemical uch a benzene, toluene, ethylbenzene, xylene, and naphthalene that can be hazardou to the health of plant, animal, and human [1-4]. Petroleum-contaminated oil i currently being treated uing phyical, chemical, and biological procee. Mot of the phyical method currently ued for treatment of contaminated oil are expenive [3]. Chemical treatment include direct injection of oxidizing agent into contaminated oil and groundwater [5], thereby altering native aquatic chemitry [5]. So, the ue of microbial potential for the remediation of toxic compound from oil (bioremediation) i now accepted a an alternative to conventional method [6]. Bioremediation i a proce in which the microorganim conume organic Correponding author: hayegan@harif.edu 16

2 Shayegan, Babaee contaminant and convert them to innocuou end product. The activity of naturally occurring microbe i timulated by circulating water-baed olution through contaminated oil. Thi proce enhance initu biological degradation of organic contaminant or immobilization of inorganic contaminant. Nutrient, oxygen, or other amendment may be ued to enhance bioremediation and contaminant deorption from uburface material [7]. Bioremediation of contaminant can be accomplihed by two method: bioaugmentation and biotimulation. The proce of bioaugmentation, a it applie to remediation of petroleum hydrocarbon contaminated oil, involve the introduction of microorganim that have been cultured to degrade variou chain of hydrocarbon into a contaminated ytem. The culture may be derived from the contaminated oil or they may be obtained from a tock of microbe that have been previouly proven to degrade hydrocarbon. Once introduced into the ytem, the cultured microorganim electively conume the hydrocarbon. The proce of biotimulation introduce additional nutrient in the form of organic and/or inorganic fertilizer into a contaminated ytem which increae the population of the indigenou microorganim [8]. Bioremediation of petroleum-contaminated oil ha been invetigated ince the late 1940 but interet in the field did not become widepread until the Exxon Valdez oil pill in 1989 [9 and 10]. Conequently, there have been a large number of tudie conducted and bioremediation ha almot alway been found to be an effective treatment of hydrocarbon-contaminated ite [1, 2, 11 and 12]. In the field of biotimulation, nutrient upplementation for hydrocarbon degradation ha traditionally focued on addition of N and P, either organically or inorganically. Becaue carbon (C) i a major contituent of petroleum fuel, it traditional role in bioremediation reearch ha typically been an index to determine the amount of N and P that need to be added to reach the optimal C:N:P ratio [5]. Several tudie have reported poitive effect of biotimulation by nutrient amendment on oil decontamination [13]. However, an undertanding of nutrient effect at a pecific ite i eential for ucceful bioremediation [13]. Biodegradation rate were reported to depend mainly on the concentration of nitrogenou nutrient in the ediment pore water, the oil loading and the extent to which natural biodegradation had already taken place [14]. Xu et al., in 2010 compared the efficiency of variou biotimulation and bioaugmentation trategie in reducing oil petroleum contamination under laboratory condition. In hi tudy, inorganic nutrient uch a (NH4) 2 SO 4 and K 2 HPO 4 were added to the treatment, 27% of TPH, to give a final C:N:P ratio of 100:10:1 [15]. Previou reearch ha hown that nutrient addition enhance the microbial activity, which caue an increae in the bioremediation rate. However, optimal nutrient timulate the microorganim. The objective of thi tudy wa to identify the effect of nutrient ratio on the extent of enhanced hydrocarbon biodegradation and develop a uitable model to predict the growth rate of microorganim and removal rate of total petroleum hydrocarbon from the contaminated oil. Iranian Journal of Chemical Engineering, Vol.9, No. 4 17

3 Study of Enhanced Bioremediation in Treatment of Ga Condenate Contaminated Soil 2. Material and method 2-1. Soil ample Sarkhun ga refinery i located at about 50km north-eat of Bandar Abba and refine 15 million STD cubic meter of natural ga per day. For the lat 20 year, the urrounding oil of the refinery have been gradually contaminated by ga condenate leaked from pipe, burn pit area and watewater collection network. It wa concluded that after more than 20 year, environmental adaptation ha reulted in growing bioremediation microorganim within the oil. Seven ample from variou highly contaminated location around the refinery were picked up Experimental deign and treatment method Three different boxe with a capacity of 1290 cm 3 were ued to run the experiment. The dimenion and the function of each box are hown in Fig. 1. For each experiment, 1 kg of contaminated oil and nutrient olution were added to each box. Knowing the initial TPH (X) a mg C/kg oil and conidering the C:N:P ratio (C mole of carbon, N mole of nitrogen, and P mole of phophorou a main nutrient), the amount of nutrient needed can be calculated. NH 4 NO 3 and KH 2 PO 4 were ued a nitrogen and phophorou ource. Uing a imple tet, the required amount of makeup water for recovering moiture lot due to evaporation wa calculated for moiture control. The makeup water wa added on an everyday bai in the treatment period. Aeration wa done by mixing the oil everyday. The TPH wa meaured every three day. TPH meaurement were baed on olvent extraction and aborption againt I ray in a 2940 cm-1 frequency which i taken from EPA41302 and ASTM D3921 tandard, and proceed with a TPH/TOG Analyzer (Infracal) [16,17]. For further tudy on biodegradation capability of microorganim in ample, contaminant removal percent () wa tudied and an empirical model wa obtained, a follow: A1 time( day) + A2 ( %) = (1) time( day) + B In which A 1 i final removal efficiency, A 2 i a factor preenting the initial removal percent (that i zero in all ample here) and B repreent the Nitrogen to Phophorou ratio which i the mot important parameter in the above equation. Figure 1. Specification of boxe ued in treatment 18 Iranian Journal of Chemical Engineering, Vol. 9, No. 4

4 Shayegan, Babaee 2-3. Model decription Model Developing tage were a follow 1. epreenting kinetic model of microbial growth and obtaining parameter needed. 2. Developing bioremediation and pollution degradation model. For thee purpoe, the following aumption were made: The biological proce i aerobic. Available oxygen and nutrient needed are contant. Temperature and Humidity are contant. Pollution i uniformly pread in oil. Growth of microorganim follow Monod model. The only limited material for biological reaction i organic carbon from contamination Kinetic model of microbial activity ate of microorganim growth can be repreented by equation (2). μ = μ max S (4) Where μ max i the maximum pecific growth rate (time -1 ), S i the limited ubtrate concentration (ma/volume), and K i the half rate contant or the ubtrate concentration at a pecific growth rate which equal to half μ max (ma/volume). Therefore g = μ max S X (5) Microbial indigenou Decay rate can be defined by equation (6) = K X (6) d d Where K d i the indigenou decay coefficient (time -1 ). Hence, the net rate of bioma growth i g dx = = μx dt (2) Where g i the rate of bioma growth (ma per volume per time), X i the bioma concentration (ma per volume), and μ i the pecific growth rate (time -1 ). μ can be defined by the following equation: S net = μmax X KdX Thi equation can be written a KS net = Y X KdX (7) (8) dx / dt growth rate μ = = X unit of bioma ma of new cell yntheized = ma of cell preent in the reactor 1 ΔX X Δt time (3) In which Y i the yield coefficient and K i the maximum ubtrate utilization rate coefficient (time -1 ). Y bacterial growth rate = = ubtrate utilization rate g u (9) Monod model that wa choen for microbial growth i: μ K = max Y (10) Iranian Journal of Chemical Engineering, Vol.9, No. 4 19

5 Study of Enhanced Bioremediation in Treatment of Ga Condenate Contaminated Soil Therefore u KS = X (11) in which u i ubtrate utilization rate (ma per volume per time) Calculation of biokinetic parameter To calculate Biokinetic parameter, equation (11) hould be rearranged a follow u ΔS KS XΔt K 1 1 = = X = + Δ t K + S ΔS K S K (12) Therefore, it i poible to obtain K and K by plotting (XΔt/ΔS) v. (1/S). Alo, the net rate of microbial growth (equation (8)) hould be rearranged a follow KS ΔS = K + Δ S X t 1 ΔS = Y K ΔX KS Δt XΔt = = net XY KdX Δ t K + S d (13) Therefore, it i poible to obtain Y and K d by plotting (1/Δt) v. (ΔS/XΔt). Ma balance around the whole box could be implified a follow: dc dt r = C (14) Uing the above information thi equation can be written a follow: r r C ds KS = = X dt (15) dx KS rx = = YX KdX dt (16) The integration of the above equation would reult in the following equation: = 0 exp KS X X Y Kd dt + K S ( ) = St (17) t KS t KS S + 0 X 0 exp Y Kd dt 0 K S 0 K + S (18) Numerical method were ued to olve thee equation. 3. eult and dicuion Meaurement reult in the 18-day treatment period are hown in Fig. 2. It can be een in Fig. 2 that oil around Sarkhun refinery ha a high capability to remediate hydrocarbon contaminant and can reduce the amount of pollutant only by providing proper condition uch a aeration, moiture content control and ufficient nutrient addition. Alo, during the 18-day treatment period in laboratory cale, removal efficiency wa at leat 50% in all ample. Therefore, it i poible to reduce the TPH to the tandard level in a few month treatment period. According to the reult, the removal efficiency at 100:5:1 and 100:9:1 nutrient ratio wa almot imilar. However, thi reult doe not mean the higher the ratio the more optimal, due to the larger nutrient requirement at higher nutrient ratio. Therefore, with repect to the economical treatment, the optimum nutrient ratio in all ample i 100:5:1. 20 Iranian Journal of Chemical Engineering, Vol. 9, No. 4

6 Shayegan, Babaee Figure 2. TPH reduction in an 18-day treatment period According to equation 1 for a nutrient ratio of 100:5:1, B i equal to 5 and for a 100:9:1 nutrient ratio B i 9. The reult obtained from thi model are hown in Fig. 3. It i obviou that the mot important feature of thi model i the prediction of the time needed to reach the final removal efficiency. However, thi data can not be predicted from the tarting time of remediation. Extrapolating on thee graph by uing the empirical model howed that at the end of the 3 rd month (after a 90-day treatment period), all ample will reach the final removal efficiency, which i about 70 to 90 percent Modeling In thi tudy the limiting ubtrate (S) i TPH (mg C/kg oil). Meauring of bioma concentration (MLVSS) and TPH change are needed for calculating the parameter of the model. In Table 1, the Biokinetic parameter in all 7 ample are repreented. Iranian Journal of Chemical Engineering, Vol.9, No. 4 21

7 Study of Enhanced Bioremediation in Treatment of Ga Condenate Contaminated Soil Figure 3. TPH removal efficiency, experimental data and empirical model Table 1. Biokinetic parameter in all 7 ample 1 t ample 2 nd ample 3 rd ample 4 th ample 5 th ample 6 th ample 7 th ample K (d -1 ) K (mg C/kg oil) K d (d -1 ) Y μ max (d -1 ) Iranian Journal of Chemical Engineering, Vol. 9, No. 4

8 Shayegan, Babaee Comparing experimental and modeling reult The comparion between experimental data and modeling reult i repreented in Fig. 4. Thi comparion how that the reult of modeling can imulate the behavior of bioremediation in contaminated oil with a partly uitable accuracy. 4. Concluion In thi tudy, it i hown that oil around Sarkhun refinery, which ha been contaminated for more than 20 year, ha a high capability for bioremediation. By providing the minimum proper condition in laboratory, mean removal percent in all even ample wa at leat 50% during an 18-day treatment period. The optimum nutrient ratio wa 100:5:1 for C:N:P. Alo, the obtained empirical model how that in a 90-day treatment period, it i poible to reach a final removal efficiency which i about 70 to 90%. Developing a model by taking Monod equation a bioma growth model, revealed that it i poible to predict the TPH biological removal. Figure 4. Comparing experimental and modeling reult Iranian Journal of Chemical Engineering, Vol.9, No. 4 23

9 Study of Enhanced Bioremediation in Treatment of Ga Condenate Contaminated Soil Acknowledgment The author would like to thank the Company of Sarkhun and Ghehm ga refinery for their financial upport of thi tudy. eference [1] Zhou, E. and Crawford,., "Effect of oxygen, nitrogen, and temperature on gaoline biodegradation in oil", Biodegradation, 6, 127 (1995). [2] Liebeg, E. W. and Cutright, T.J., "The invetigation of enhanced bioremediation through the addition of macro and micronutrient in a PAH contaminated oil", International Biodeterioration and Biodegradation, 44, 55 (1999). [3] Ting, H. L. Hu and Tan, H. M., "Bioremediation of petroleum hydrocarbon in oil microcom", eource and Environmental Biotechnology, 2, 197 (1999). [4] Vaudevan, N. and ajaram, P., "Bioremediation of oil ludgecontaminated oil", Environment International, 26, 409 (2001). [5] ier-obert, E., "emediation of petroleum contaminated oil: Biological, phyical, and chemical procee", CC Pre LLC, Boca aton, FL (1998). [6] Pirie, P., Naeimpoor, F. and Hejazi, P., "A microcom tudy on P-Nitrophenol biodegradation in oil lurry by Alcaligene faecali: Plackett-Burman deign", Iranian Journal of Chemical Engineering, 8, 2 (2011). [7] FT, "emediation technologie creeening matrix and reference guide", Ver. 4.0 (2007), frtr.gov. [8] Pankrantz, T. M., "Environmental engineering dictionary and directory", CC Pre, Boca aton, FL (2001). [9] Margein,. and Schinner, F., "Laboratory bioremediation experiment with oil from a dieel-oil contaminated ite ignificant role of cold-adapted microorganim and fertilizer", Chemical and Biotechnology, 70, 92 (1997). [10] Jackon, W. A. and Pardue, J. H., "Potential for enhancement of biodegradation of crude oil in Louiiana alt marhe uing nutrient amendment", Water, Air, and Soil Pollution, 109, 343 (1998). [11] Hueemann, M. H. and Moore, K. O., "Compoitional change during landfarming of weathered Michigan crude oil-contaminated oil", Journal of Soil Contamination, 2 (3), 245 (1993). [12] Li, K.Y., Zhang, Y. and Xu, T., "Bioremediation of oil-contaminated oil - a rate model", Wate Management, 15, 335 (1995). [13] Braddock, J. F., uth, M. L., Walworth, J. L. and McCarthy, K. A., " Enhancement and inhibition of microbial activity in hydrocarboncontaminated Arctic oil: Implication for nutrient- amended bioremediation", Environmental Science and Technology, 31, 2078 (1997). [14] Bragg, J.., Prince,. C., Harner, E. J. and Atla,. M., "Effectivene of bioremediation for the Exxon Valdez oil pill", Nature, 368, 413 (1994). [15] Xu, Y., Lu, M., "Bioremediation of crude oil-contaminated oil: Comparion of different biotimulation and bioaug-mentation treatment", Hazardou Material, 183, 395 (2010). [16] D3921. htm. [17] contaminant/index.cfm. 24 Iranian Journal of Chemical Engineering, Vol. 9, No. 4