Strategy for Bioremediation and pollution Management for Sustainable Ecosystem

Agiri .G.O., Adimula H.A., Akumagba P.E., Mamah S. and Okpala K .

Industrial Safety and Environmental Technology DepartmentPetroleum Training Institute, Effurun, Delta State, Nigeria.

Federal University of Technology, Owerri, Imo State.

Abstract

Soil artificially contaminated with crude petroleum wastreated with hydrocarbon degrading microorganisms. Thebacteria consortium used consists of streptococcus, themophilus,micrococcus varians and bacillus sp. immobilized in coconut fibres(carrier). The results show that the immobilizedmicroorganisms have good shelf life of 5.90 × 109 CFU/g after120 days. After seven weeks of application of the immobilizedmicroorganisms in bioremediation of crude petroleumcontaminated soils the concentration of PAHs, TPH, BTEXs,were reduced by 95.86%, 83.01% and 95.02% respectively ascompared to 1.56%, 1.81% and 3.26% of the reduction in thecontrol. Therefore the immobilized bacteria system usingcoconut fibres as a carrier can serve as an effective and fastbioremediation tool for cleaning up crude petroleumcontaminated soil at low cost.

Introduction/Background Information

In the Niger Delta area of Nigeria there has been severalreported cases of oil spills which have led to thecontamination of available land for arable farming. The oilexploration, producing and processing companies attempts inthe past to clean and treat the contaminated soil have notyield the required result. The methods adopted are usually notfriendly to the environment after treatment. However, due

to the raise of environmental problems emerged from theprocessing or discard of petroleum and its products, there isthe need to look for biodegradable and renewable rawmaterials.

In pursuance for new materials that could be used as aneffective hydrocarbon degrading agent with little or noenvironmental problems, hence the interest in researchfor the development of compounds that use natural fibres asalternatives to replace products that damage theenvironment, (Agiri, et al., 2011). In recent years much interesthas been shown in the microbial biodegradation of pollutantsas a sustainable way to remediate contaminated environments.The bioremediation and biotransformation methods are employedto degrade, transform hydrocarbon and hydrocarbon derivativessuch as crude oil: Polyaromatic hydrocarbons (PAHS),Polychlorinated biphenyls (PCBs), Polyaromatic Hydrocarbons(PAHs), pharmaceutical substances, radionuclides and heavymetals. The elimination of a wide range of pollutants andwastes from the environment is an absolute requirement topromote a sustainable development of our society with lowenvironmental impact. Biological processes play a major rolein the removal of contaminants and they take advantage of theastonishing catabolic versatility of microorganisms todegrade/convert such compounds. Bioremediation Process

Bioremediation is natural process utilizing microbes,(microorganisms) or bacteria to remove environmentalpollutants from water, soil, or gas. Bioremediation destroysor renders harmless various contaminants using naturalbiological activity. Many bacteria are capable of degradingthe constituents of Crude oil (Gimsing, et al., 2010). However,the rate at which degradation occurs is slow (Atlas andBartha, 1972). The slow rate of natural biodegradation is dueto the following reasons: low counts of hydrocarbon-degradingmicrobes, toxicity of some components and limited crudeoil/soil interface.

Immobilization of Microbial Cells in Cellulosic Materials

Immobilization of microorganisms has the potential to overcomesome problems associated with natural bioremediation process.It overcomes problem of limited crude oil/substrateinterfacial area (Wilson and Bradley, 1977).The carrier actsas an intermediary between the crude oil and cell surface.There in an increase contact between the crude oil andmicroorganism and a corresponding increase on the surface areaof the substrate available for cell attachment ( Rosevear et al.,1987; Heitkamp et al., 1990). Immobilizing agents offer cellularprotection against adverse environmental conditions (Tope et al.,1999).

Immobilized Microbial Cells in Carriers

Immobilized Pseudomonas fluorescent in Drizit to enhance biodegradation ofpetrol was carried out by Wilson and Bradley (1977). Immobilizedcrude oil utilising bacteria in alginate, was reported byRahman et al., (2006). Manikandan et al., (2007) immobilizedPseudomonas aeruginosa on sodium alginate beads to biodegradechlorobenzene. Agiri et al., (2011) immobilised consortium ofStreptococcus themophilus, micrococcus varians and bacillus sp. in groundnuthusk and coconut fibres to biodegradation of soil contaminatedwith crude oil.

Materials and Method

Cellulosic materials used as carriers for crude oil degradingmicroorganisms. Amongst which are: cassava peels, sugarcanebagasse, ground nut husk, coconut fibres, and corn cobs.Factors considered in screening are: readily available, do notserve as nutrient source for microorganism, not easilyattacked by other microorganism (resistant to fungi and rot),high biomass retention, easy immobilization technique, non-biodegradable by crude oil degrading microorganisms,(Agiri et al., 2011), and biodegradable after application.

Cultivation, Isolation, Identification and Characterization ofCrude Oil Degrading Microorganisms

This involved the cultivation of Hydrocarbon Degrader inmineral salt broth (with crude oil as carbon source) byadopting the enrichment technique of Schlegel (1993). MineralSalt Medium (MSM) solution was prepared according to thecomposition of Mills et al., as modified by Okpakwasili and Okorie(1988). Bacterial isolates were examined for colonialmorphology as well as cell morphology and biochemicalcharacteristics. Tests were carried out according to themethods described by Carpenter (1977), Cruickshank et al., (1975)and Gerhadt et al., (1981). Identification of the bacteria to thegeneric level followed the schemes of MacFaddin (1979) andHolt (1983).

A parcel of land measuring 144 m2 was contaminated with 380litres of crude oil (Escavos light). One week aftercontamination, the soil was tilled to a depth of 15cm withgarden fork and shade. After tilling, a consortium of crudeoil degrading microorganism immobilized in coconut fibres in aratio of 1:1 was applied to the soil. Nutrient (fertilizer NPK15-15-15) was added to the soil thrice weekly and tilled twicea week to a depth of 15cm using garden fork after addition ofnutrient. Soil samples were collected on a weekly intervalwith soil auger for laboratory analysis of physico-chemicalproperties of the soil, microbial count and other parameters.

Results and Discussion

The results of the characterization and identification of theisolates showed that the microbial isolates that could utilizethe hydrocarbon were: Micrococcus roseus, Leuconostoc mesenteriodes,Streptococcus thermophilus, Aerococcus viridans, Flavobacterium thalpophilium,Micrococcus varians and Bacillus sp. (Agiri et al., 2011). Consortium ofbacteria was created consist of Streptococcus thermophilus,Micrococcus varians and Bacillus sp. The values of the determinedparameters of the crude oil carrier (Coconut fibre) shown inTable 1 clearly demonstrates its suitability as a carrier forhydrocarbon utilizing bacteria.

The results of the GC analysis of the uncontaminated andcontaminated soil samples are as shown in Tables 2 and Table3. The tables showed the determined values of total petroleumhydrocarbon (TPH), total organic carbon (TOC), Polyaromatichydrocarbons (PAHS) and benzene, toluene, ethylbenzene andxylene (BTEXs), and pH of the uncontaminated and contaminatedsoil after seven weeks of treatment. Others were TotalHeterotrophic Bacteria count, Hydrocarbon Utilizing Bacteriacount, Nitrate and Total Phosphorus. The trend in degradationprocess as observed from the data before and after biologicaltreatment showed a gradual reduction in the total amount oftotal petroleum hydrocarbon (TPH), total organic carbon (TOC),Polyaromatic hydrocarbons (PAHS) and benzene, toluene,ethylbenzene and xylene (BTEXs) present in both theuncontaminated and contaminated soils over a treatment periodof seven weeks. About 91.29% of hydrocarbon content in theoriginal crude oil was removed after seven weeks treatmentwith the consortium of bacteria immobilized in the cellulosicagricultural harvest material (coconut fibre). The percent ofTPH, PAHS, BTEX degraded in crude oil in the contaminated soilwere 83.01%, 95.86%, and 95.02% respectively after seven weeksof treatment as shown in Fig.7, Fig. 8 and Fig.9. The pH,

TOC, Nitrate and total phosphorous levels in soil were raisedslightly after remediation as shown in Fig. 10, Fig. 15 andFig. 16. The result also show that there a gradual increase inthe amount of total heterotrophic bacteria Fig.13 and anincrease in the amount of the hydrocarbon utilizing bacteriawas recorded (Fig. 14). The increase in the amount of thehydrocarbon utilizing bacteria was slight initially andsuggests that bacteria start degrading after about three weeksof treatment. The quality of soil was not adversely affectedby remediation with the immobilized products. The results showthat the consortium of these isolates has high proficiency inbioremediation processes.

Crude oil being a complex mixture of hydrocarbon and non-hydrocarbon molecules when spilled affects the soil adverselyas shown in Fig.2. After one week of contamination, the plantsand probably some others microorganisms could have beendestroyed as the soil is laid bare. Treatment of thecontaminated soil with the immobilized microorganism incoconut fibre is intended to reduce these hydrocarbonmolecules which are toxic and major pollutants to theimmediate environment. The potentiality of the bacteria indegrading hydrocarbon is based on the fact as it serves asenergy source to the hydrocarbon utilizing bacteria. Based onthe ease of application of the immobilized microorganism onthe crude oil contaminated soil Fig. 6 and steady recovery ofthe soil and consequent growth of plants Fig.21 and Fig.22after eleven weeks and thirteen weeks of treatmentrespectively. Therefore, bioremediation an effective, low costprocess for rapid remediation of contaminated soil could beadopted as a process for sustainable ecosystem management.

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Conclusion

The research project has succeeded in developing a bacterialproduct that possesses certain distinct advantages over thecommon methods of bioremediation. The product developed couldbe rapidly deployed for bioremediation of crude oil pollutedsoil and the application of the product has shown that it ismore effective in the remediation of soils contaminated withcrude oil having removed about 91.29% content of the crudepetroleum pollution in seven weeks compared to removal ofabout 17.36% crude petroleum content by the free residencebacteria cells. The products developed have great potentialfor use as product of choice to remediate crude oil pollutedsoils. And can serve as an effective and fast bioremediationtool for cleaning up crude petroleum contaminated soil at lowcost.

Acknowledgement

We wish to express our profound gratitude to the PTDF for providing the fund for this research. We also thank the

management of the Petroleum Training Institute, Effurun, DeltaState their support and encouragement.

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