bio treatment of hydrocarbon polluted soil with agriculture residues

Available online at www.sciencedirect.com Energy Procedia (2011) 1558–1562 IACEED2010 Bio-treatment of Hydrocarbon Polluted Soil with Agriculture Residues Gao Dongmei, Xu Ying*, Farhana Maqbool, Xu Zhenhua Key Laboratory of Marine Environment & Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China Abstract Agriculture residues were used effectively during the bio-treatment of severely hydrocarbon polluted soil After 90 days of research, the hydrocarbon concentration of the soil significantly decreased in the bio-treatment mound (Soil + Agriculture residues, SAR) compared with the control treatment (Soil only) The activity and functional diversity of the soil microorganisms were also monitored, and they were both higher in the bio-treatment soil (SAR) The active microbial community did a good contribution to the hydrocarbon decline The data gathered from this study not only conveys important information for reuse of the local agriculture residues, but also provides a suitable, economical and effective way of bioremediation of severely hydrocarbon polluted soil © 2011 Published by Elsevier Ltd Selection and peer-review under responsibility of RIUDS Keywords: biodegradation; microbial activity; hydrocarbon; remediation Introduction The area of oil polluted soil increased continuously, as many petroleum exp lorations, extractions, and storage places, the refinery subsoil were polluted due to the tank and tubing leakages To xicity of petroleum hydrocarbon has been a motivating force in finding sustainable biological methods of remediation of these compounds [1] Bioremediation d iffered fro m physical and chemical approaches emerged as a cost-effective treatment method for hydrocarbon polluted soil [2] While, some bioremediation approach (such as phytoremediation) could only be conducted at lightly polluted site, as the high concentration of hydrocarbon inhibited seed germination and plant growth [3] Thus, suitable biological method to deal with the severely contaminated soil should be exploited Namkoong et al [2] demonstrated that the added organic amendments including manure, yard wastes, * Corresponding author Tel.: +86-532-66782092; fax: +86-532-66782092 E-mail address: xuying19840907@163.com 1876–6102 © 2011 Published by Elsevier Ltd doi:10.1016/j.egypro.2011.03.266 Gao Dongmei et al / Energy Procedia (2011) 1558–1562 and food processing wastes could supplement the amount of nutrients and readily degradab le matters during soil remed iation However, the amount of additions should be d etermined properly according to the local soil characteristics and conditions The aim of present study was to test the added agriculture residues effects on the degradation of the hydrocarbon in the polluted soil Microbial activ ity and diversity were also determined to find their functions during the hydrocarbon degradation Results of present study would also provide basis for the further extension and application of b io -treat ment technology at the highly polluted site Materials and methods 2.1 Bio-treatment process The bio-treatment mound was prepared by mixing oil polluted soil with mixed agricu lture residues used as bulking agents (maize straw, rice straw, sawdust and bean cake) in a proportion of 1:2 (volu me: volume): S – So il; SA R – Soil + Agriculture residues The mound was turned once a month The turnings allo wed the aeration and stimulated the microbial activ ities The mo isture of the mixture was controlled by adding the necessary amount of water to keep at about 50% Three representative samples were co llected at 90 days of bio-treat ment by mixing several subsamples taken fro m the three layers (upper, middle and bottom layer) of the mound, and expressed as Under Layer (UL), Middle Layer (M L) and Bottom Layer (BL) The temperature was measured every days until the end of the process (after 90 days of bio-treatment) 2.2 Physical-chemical analysis Soil organic carbon was determined by the Walkley and Black dichro mate o xidation method Soil pH was measured with a soil-to-solution ratio o f 1:2.5 using a pH meter Electrical conductivity (EC) was determined by the soil mult i-parameter analy zer Water content was determined by dry ing at 105 ºC for h Hydrocarbon in the soil was extracted ultrasonically as described by Gurska et al.[1], then analyzed with the method of Phillips et al.[4] 2.3 Soil microbial activity Fluorescein diacetate [3’, 6’-d iacetylfluorescein (FDA )] hydrolysis was determined as a measure of total microbial activ ity of the soil The amount of FDA hydrolyzed was measured on a spectrophotometer set at a wavelength of 490 n m [5] The value of A 490 per gram of dry soil was referred to the soil microbial activity 2.4 Microbial community functional diversity In present study, microbial co mmunity functional diversity was determined using BIOLOG ECO p lat e (Biolog, Inc., Californ ia, USA ) Cell suspensions were prepared by extracting the soil samples with sterile NaCl solution, and a 150-μL suspension of 10-3 dilution was inoculated into each micro-p late well The absorbance of wells was measured at 590 n m every 24 h interval Shannon index, Simpson index and Pielou index were calculated according to Dunbar et al [6] 1559 1560 Gao Dongmei et al / Energy Procedia (2011) 1558–1562 2.5 Statistical analysis All results are exp ressed as mean ± standard deviation (SD) Statistical analyses were performed using one-way ANOVA and followed by the LSD test The level of significance was assessed at a level of 0.05 Results and discussion 3.1 Soil characteristics The soil physicochemical characteristics before and after 90 days of bio -treatment are presented in Table Init ially, the soil carbon content was greatly higher in the control treat ment (Soil only), wh ich resulted from the severely oil contamination After the bio -treat ment carried out for 90 days, the organic matter/carbon content dropped to different levels The soil pH decre ased significantly during the biotreatment process, and the soil pH in SA R mound was much lo wer than that of the control, which was good for helping relieve the local soil alkalizat ion Similarly, the electrical conductivity (EC) of the SAR treatment also decreased from 0.11 to 0.07 s m -1 , and subsequently increased the soil microorganism activity As many microbes could not tolerate high salt level T able Some physicochemical characteristics of each soil layer Organic Matter (g kg-1 ) Organic Carbon (g kg-1 ) EC values (s m -1 ) pH values 0-day 90-day 0-day 90-day 0-day 90-day 0-day 90-day SAR-UL 19.8 13.7 11.5 7.9 0.11 0.07 8.26 8.10 SAR-ML 16.3 13.3 9.5 7.7 0.12 0.07 8.24 8.16 SAR-BL 22.9 15.7 13.3 9.1 0.12 0.07 8.24 8.22 S-UL 24.1 12.0 14.0 7.0 0.15 0.21 8.41 8.48 S-ML 23.0 14.0 13.3 8.1 0.14 0.22 8.42 8.45 S-BL 23.4 12.8 13.6 7.4 0.14 0.14 8.43 8.47 T reatment 3.2 Temperature changes during the bio-treatment process Temperature was used to monitor the performance of this process Like many b io -treat ment processes, there was a rap id increase of the temperature during the first few days (Fig 1a) However, the temperatures of different layers were not as high as previous researches, as this study was conducted in late autumn, when the ambient temperature was about 10-18 ºC Co mpared with the control mound (Soil only), the temperature of the SAR mound rose about 10 ºC during the process This could be due to the active microorganism activities 3.3 Microbial activity Soil microbial activity provided a general measure of organic matter turnover in natural habitats, owing to about 90% of energy in soil environment flowed through microbial decomposers [5] In present study, after 90 days of treat ments, the microbial activ ities of the three layers in SA R mound were significantly higher than that of the control mound (Fig 1b) Agriculture residues (AR) mixed with soil could supply much mo re co-metabolis m matters to the soil microorganisms, which subsequently 1561 Gao Dongmei et al / Energy Procedia (2011) 1558–1562 stimulated the microbial activit ies and hydrocarbon bio degradation In addition, Namkoong et al [2] suggested that excessive addition of the organic amend ments would retard degradation rate of the target pollutants Thus, adding suitable amount of readily degradable organic matters (such as agriculture residues) was of vital important for successful bio-treatment of polluted soil 35 (b) A490 /Abs g -1 dry soil Temperature ºC 30 (a) 25 20 15 10 0 10 20 30 40 50 60 70 Days 80 90 90 Days Fig (a): Soil temperature changes of each level during the bio-treatment Symbols stand for Soil + Agriculture residues-Upper Layer (SAR-UL) ( ), Soil + Agriculture residues-Middle Layer (SAR-ML) ( ), Soil + Agriculture residues-Bottom Layer (SARBL) ( ), Soil-Upper Layer (S-UL) ( ), Soil- Middle Layer (S-ML) ( ) and Soil-Bottom Layer (S-BL) ( ), respectively; (b): FDA activity in the bio-treatment soil after 90 days of bio-treatment Data presented as means ± SD (n=3) Symbols stand for SARUL ( ), SAR-ML ( ), SAR-BL ( ), S-UL ( ), S-ML ( ) and S-BL ( ), respectively 3.4 Microbial community diversity The microbial co mmunity in the selected samples was expressed by the functional diversity indices (Fig 2a) Co mpared with the control treatment (So il only ), Shannon and Simpson indices of the SAR treatment were both significantly higher (p < 0.05) The microbial co mmunity diversity responded to oil residues differently, wh ich was probably due to that the oil residues were important factor in the flu x of substrate [7] Thus, with the addition of agriculture residues, much more nutrients and co -metabolisms presented and stimulated the microbial co mmunity functional diversit ies and activities, which subsequently enhanced the biodegradation of petroleum hydrocarbons Index value 3.0 30000 (a) 2.5 2.0 1.5 1.0 0.5 0.0 Shannon Pielou Simpson Functional diversity index Oil concentration /mg kg-1 3.5 25000 (b) 20000 15000 10000 5000 0 90 Days Fig (a): Functional diversity index of the soil after 90 days of bio-treatment Symbols stand for Soil ( ) and Soil + Agriculture residues (SAR) ( ), respectively Asterisks indicate significant difference from control treatment (soil without agriculture residues) (p < 0.05) (b): Hydrocarbon concentration of the soil after 90 days of bio-treatment Data presented as means ± SD (n=3) Symbols stand for SAR-UL ( ), SAR-ML ( ), SAR-BL ( ), S-UL ( ), S-ML ( ) and S-BL ( ), respectively 1562 Gao Dongmei et al / Energy Procedia (2011) 1558–1562 3.5 Hydrocarbon degradation The oil content in each layer was monitored during the 90 days of bio-treatment (Fig 2b) For the control treatment, the o il concentration decreased from about 18800 mg kg -1 to 13800 mg kg -1 , most of which might volat ilize naturally While for the SAR treat ment, the concentration sharply declined to about 4200 mg kg -1 at the end of the experiment In summary, proper organic matters (agricu lture residues) and active microorganism contributed greatly to the biodegradation process of hydrocarbons However, after 90 days of bio-treat ment, there were still so me hydrocarbon residues left in the soil, wh ich still need further effective degradations Conclusion The use of agriculture residues in bio-treatment caused effective hydrocarbon degradation After 90 days of study, the soil microbial activ ity and functional diversity were both significantly imp roved in the bio-treat ment mound (So il + Agriculture residues, SAR) co mpared with the control treat ment (Soil only) The hydrocarbon concentration was greatly decreased from severe level (18800 mg kg -1 ) to relat ively low level (4200 mg kg -1 ) Thus, this bio-treatment process could be recommended for biodegradation of highly hydrocarbon polluted soil, and the reuse of agriculture residues in soil bioremediat ion is cost effective strategy for the sustainable development of environment Acknowledgements This research was supported by the Foundation for Key Program of the Education Min istry, Ch ina (No 308016), and the National Major Special Technological Program Concerning Water Pollution Control and Management (No 2008ZX07010-008) References [1] Gurska J, Wang W, Gerhardt KE, Khalid AM, Isherwood DM, Huang XD, et al Three year field test of a plant growth promoting rhizobacteria enhanced phytoremediation system at a land farm for treatment of hydrocarbon waste Environmental Science & T echnology, 2009, 43(12): 4472-4479 [2] Namkoong W, Hwang E, Park J, Choi J Bioremediation of diesel-contaminated soil with composting Environmental Pollution, 2002, 119(1): 23-31 [3] Gerhardt KE, Huang X, Glick BR, Greenberg BM Phytoremediation and rhizoremediation of organic soil contaminants: potential and challenges Plant Science, 2009, 176(1): 20-30 [4] Phillips LA, Greer CW, Farrell RE, Germida JJ Field-scale assessment of weathered hydrocarbon degradation by mixed and single plant treatments Applied Soil Ecology, 2009, 42(1): 9-17 [5] Green VS, Stott DE, Diack M Assay for fluorescein diacetate hydrolytic activity: optimization for soil samples Soil Biology and Biochemistry, 2006, 38(4): 693-701 [6] Dunbar J, T icknor LO, Kuske CR Assessment of microbial diversity in four southwestern United States soils by 16S rRNA gene terminal restriction fragment analysis Applied and Environmental Microbiology, 2000, 66(7): 2943-2950 [7] Zhang Q, Zhou Q, Ren L, Zhu Y, Sun S Ecological effects of crude oil residues on the functional diversity of soil microorganisms in three weed rhizospheres Journal of Environmental Sciences, 2006, 18(6): 1101-1106  ... (4200 mg kg -1 ) Thus, this bio- treatment process could be recommended for biodegradation of highly hydrocarbon polluted soil, and the reuse of agriculture residues in soil bioremediat ion is cost... 90 90 Days Fig (a): Soil temperature changes of each level during the bio- treatment Symbols stand for Soil + Agriculture residues- Upper Layer (SAR-UL) ( ), Soil + Agriculture residues- Middle Layer... index of the soil after 90 days of bio- treatment Symbols stand for Soil ( ) and Soil + Agriculture residues (SAR) ( ), respectively Asterisks indicate significant difference from control treatment