Bioremediation of PAHs - Limitations and soultions

Introduction 1.1 Occurrence of polycyclic aromatic hydrocarbons (PAH) in the environment Worldwide industrial and agricultural developments have released a large number of natural and synthetic hazardous compounds into the environment due to careless waste disposal, illegal waste dumping and accidental spills. As a result, there are numerous sites in the world that require cleanup of soils and groundwater. Polycyclic aromatic hydrocarbons (PAHs) are one of the major groups of these contaminants (Da Silva et al., 2003). PAHs constitute a diverse class of organic compounds consisting of two or more aromatic rings with various structural configurations (Prabhu and Phale, 2003). Being a derivative of benzene, PAHs are thermodynamically stable. In addition, these chemicals tend to adhere to particle surfaces, such as soils, because of their low water solubility and strong hydrophobicity, and this results in greater persistence under natural conditions. This persistence coupled with their potential carcinogenicity makes PAHs problematic environmental contaminants (Cerniglia, 1992; Sutherland, 1992). PAHs are widely found in high concentrations at many industrial sites, particularly those associated with petroleum, gas production and wood preserving industries (Wilson and Jones, 1993). 1.2 Remediation technologies Conventional techniques used for the remediation of soil polluted with organic contaminants include excavation of the contaminated soil and disposal to a landfill or capping - containment - of the contaminated areas of a site. These methods have some drawbacks. The first method simply moves the contamination elsewhere and may create significant risks in the excavation, handling and transport of hazardous material. Additionally, it is very difficult and increasingly expensive to find new landfill sites for the final disposal of the material. The cap and containment method is only an interim solution since the contamination remains on site, requiring monitoring and maintenance of the isolation barriers long into the future, with all the associated costs and potential liability. A better approach than these traditional methods is to completely destroy the pollutants, if possible, or transform them into harmless substances. Some technologies that have been used are high-temperature incineration and various types of chemical decomposition (for example, base-catalyzed dechlorination, UV oxidation). However, these methods have significant disadvantages, principally their technological complexity, high cost , and the lack of public acceptance. Bioremediation, on the contrast, is a promising option for the complete removal and destruction of contaminants. 1.3 Bioremediation of PAH contaminated soil & groundwater Bioremediation is the use of living organisms, primarily microorganisms, to degrade or detoxify hazardous wastes into harmless substances such as carbon dioxide, water and cell biomass Most PAHs are biodegradable unter natural conditions (Da Silva et al., 2003; Meysami and Baheri, 2003) and bioremediation for cleanup of PAH wastes has been extensively studied at both laboratory and commercial levels- It has been implemented at a number of contaminated sites, including the cleanup of the Exxon Valdez oil spill in Prince William Sound, Alaska in 1989, the Mega Borg spill off the Texas coast in 1990 and the Burgan Oil Field, Kuwait in 1994 (Purwaningsih, 2002). Different strategies for PAH bioremediation, such as in situ , ex situ or on site bioremediation were developed in recent years. In situ bioremediation is a technique that is applied to soil and groundwater at the site without removing the contaminated soil or groundwater, based on the provision of optimum conditions for microbiological contaminant breakdown.. Ex situ bioremediation of PAHs, on the other hand, is a technique applied to soil and groundwater which has been removed from the site via excavation (soil) or pumping (water). Hazardous contaminants are converted in controlled bioreactors into harmless compounds in an efficient manner. 1.4 Bioavailability of PAH in the subsurface Frequently, PAH contamination in the environment is occurs as contaminants that are sorbed onto soilparticles rather than in phase (NAPL, non aqueous phase liquids). It is known that the biodegradation rate of most PAHs sorbed onto soil is far lower than rates measured in solution cultures of microorganisms with pure solid pollutants (Alexander and Scow, 1989; Hamaker, 1972). It is generally believed that only that fraction of PAHs dissolved in the solution can be metabolized by microorganisms in soil. The amount of contaminant that can be readily taken up and degraded by microorganisms is defined as bioavailability (Bosma et al., 1997; Maier, 2000). Two phenomena have been suggested to cause the low bioavailability of PAHs in soil (Danielsson, 2000). The first one is strong adsorption of the contaminants to the soil constituents which then leads to very slow release rates of contaminants to the aqueous phase. Sorption is often well correlated with soil organic matter content (Means, 1980) and significantly reduces biodegradation (Manilal and Alexander, 1991). The second phenomenon is slow mass transfer of pollutants, such as pore diffusion in the soil aggregates or diffusion in the organic matter in the soil. The complex set of these physical, chemical and biological processes is schematically illustrated in Figure 1. As shown in Figure 1, biodegradation processes are taking place in the soil solution while diffusion processes occur in the narrow pores in and between soil aggregates (Danielsson, 2000). Seemingly contradictory studies can be found in the literature that indicate the rate and final extent of metabolism may be either lower or higher for sorbed PAHs by soil than those for pure PAHs (Van Loosdrecht et al., 1990). These contrasting results demonstrate that the bioavailability of organic contaminants sorbed onto soil is far from being well understood. Besides bioavailability, there are several other factors influencing the rate and extent of biodegradation of PAHs in soil including microbial population characteristics, physical and chemical properties of PAHs and environmental factors (temperature, moisture, pH, degree of contamination). Figure 1: Schematic diagram showing possible rate-limiting processes during bioremediation of hydrophobic organic contaminants in a contaminated soil-water system (not to scale) (Danielsson, 2000). 1.5 Increasing the bioavailability of PAH in soil Attempts to improve the biodegradation of PAHs in soil by increasing their bioavailability include the use of surfactants , solvents or solubility enhancers.. However, introduction of synthetic surfactant may result in the addition of one more pollutant. (Wang and Brusseau, 1993).A study conducted by Mulder et al. showed that the introduction of hydropropyl-ß-cyclodextrin (HPCD), a well-known PAH solubility enhancer, significantly increased the solubilization of PAHs although it did not improve the biodegradation rate of PAHs (Mulder et al., 1998), indicating that further research is required in order to develop a feasible and efficient remediation method. Enhancing the extent of PAHs mass transfer from the soil phase to the liquid might prove an efficient and environmentally low-risk alternative way of addressing the problem of slow PAH biodegradation in soil.

Proceedings of the Twenty-Fifth Annual Biochemical Engineering Symposium

The Annual Biochemical Engineering Symposium Series started in 1970 when Professors Larry E. Erickson (Kansas State University) and Peter J. Reilly (then with University of Nebraska-Lincoln) got together in Manhattan, KS along with their students for a half-day powwow and technical presentation by their students. Ever since then, it has been a forum for Biochemical Engineering students in the heartland of USA to present their research to their colleagues in the form of talks and posters. The institutions actively involved with this annual symposium include Colorado State University, Kansas State University, Iowa State University, University of Colorado, University of Kansas, University of Missouri-Columbia, and University of Oklahoma. The University of lowa and University of Nebraska-Lincoln have also participated in the conference in recent years. The host institutions for the different symposia have been: Kansas State University (1, 3, 5, 9, 12, 16, 20), Iowa State University (6, 7, 10, 13, 17, 22), University of Missouri-Columbia (8, 14, 19, 25), Colorado State University (II, 15, 21), University of Colorado (18, 24), University of Nebraska-Lincoln (2, 4), University of Oklahoma (23). The next symposium will be held at Kansas State University. Proceedings of the Symposium are edited by faculty of the host institution and include manuscripts written and submitted by the presenters (students). These often include works-in-progress and final publication usually takes place in refereed journals. ContentsPatrick C. Gilcrease and Vincent G. Murphy, Colorado State University. Use of 2,4,6-Trinitrotoluene (TNT) As A Nitrogen Source By A Pseudomonas florescens Species Under Aerobic Conditions. Marulidharan Narayanan, Lawrence C. Davis, and Larry E. Erickson, Kansas State University. Biodegradation Studies of Chlorinated Organic Pollutants in a Chamber in the Presence of Alfalfa Plants. S.K. Santharam, L.E. Erickson, and L.T. Fan, Kansas State University.Surfactant-Enhanced Remediation of a Non-Aqueous Phase Contaminant in Soil. Barry Vant-Hull, Larry Gold, and Robert H. Davis, University of Colorado.The Binding of T7 RNA Polymerase to Double-Stranded RNA. Jeffrey A. Kern and Robert H. Davis, University of Colorado.Improvement of RNA Transcription Yield Using a Fed-Batch Enzyme Reactor. G. Szakacs, M. Pecs, J. Sipocz, I. Kaszas, S.R. Deecker, J.C. Linden, R.P. Tengerdy, Colorado State University.Bioprocessing of Sweet Sorghum With In Situ Produced Enzymes. Brad Forlow and Matthias Nollert, University of Oklahoma.The Effect of Shear Stress ad P-selectin Site Density on the Rolling Velocity of White Blood Cells. Martin C. Heller and Theodore W. Randolph, University of Colorado.The Effects of Plyethylene Glycol and Dextran on the Lyophilization of Human Hemoglobin. LaToya S. Jones and Theodore W. Randolph, University of Colorado.Purification of Recombinant Hepatitis B Vaccine: Effect of Virus/Surfactant Interactions. Ching-Yuan Lee, Michael G. Sportiello, Stephen Cape, Sean Ferree, Paul Todd, Craig E. Kundrot, and Cindy Barnes, University of Colorado.Application of Osmotic Dewatering to the Crystallization of Oligonucleotides for Crystallography. Xueou Deng, L.E. Erickson, and D.Y.C. Fung, Kansas State University.Production of Protein-Rich Beverages from Cheese Whey and Soybean by rapid Hydration Hydrothermal Cooking. Pedro M. Coutinho, Michael K. Dowd, and Peter J. Reilly, Iowa State University.Automated Docking of Glucoamylase Substrates and Inhibitors. J. Johansson and R.K. Bajpai, University of Missouri.Adsorption of Albumin on Polymeric Microporous Membranes.

Associação de sistema biológico do tipo lodo ativado com reatores air lift e fotocatálise heterogênea com TiO2 para a remediação de efluente oriundo da produção industrial de TNT

Trinitrotoluene in the purification step (TNT) produced in industries, are carried out two washes at the end of the process. The first wash is done with vaporized water, which originates from the first effluent called yellow water, then the second washing with the use of sodium sulfite is performed (Na2SO3), generating a second effluent red water. This study aimed to study the individual effects, as well as the association of heterogeneous photocatalysis using TiO2 and biological treatment in air lift reactor using activated sludge (bacterial biomass) for the remediation of wastewater contaminated with nitroaromatic compounds in order to reduce toxicity and adjust the legal parameters according to regulatory agencies for disposal in waterways. The photocatalytic treatment was conducted by factorial design obtaining the best reaction conditions (pH 6.5 and concentration of TiO2 0.1 gL-1), with best results obtained at 360 minutes of reaction, reducing the absorbance 97.00%, 94.20% of the chemical oxygen demand (COD), 67.70% of total phenols, as well as a total reduction of observed peaks and assigned to nitroaromatic compounds by high-performance liquid chromatography. In the biological treatment, there was a 53.40% reduction in absorbance at 275 nm 10.00% 36.00% COD and total phenols in a short time (3 days), while for extended periods (48 days) there was an antagonistic influence on the results so that was the elevation of these parameters (COD and total phenols) instead of reducing. Chromatographic analysis confirmed the effectiveness of the biological degradation by reducing the peaks corresponding to compounds DNT and TNT. The Association of photocatalytic and biological treatments decreased results in the order of 91.10% absorbance, 70.26% of total phenols and 88.87% of COD. While the combination of biological and photocatalytic treatments generated relatively lower efficiencies, with 77.30% of absorbance reduction, 62.10% reduction of total phenols and a decrease of 87.00% of COD. In general, when comparing the chemical and biological processes in isolation, the photocatalytic treatment showed the best results. However, comparing the results of isolation and established associations, the association biological x photocatalysis showed more promising results in the treatment of red water effluent.

Integration of virus-like particle macromolecular bioreceptors in electrochemical biosensors

Rapid, sensitive and selective detection of chemical hazards and biological pathogens has shown growing importance in the fields of homeland security, public safety and personal health. In the past two decades, efforts have been focusing on performing point-of-care chemical and biological detections using miniaturized biosensors. These sensors convert target molecule binding events into measurable electrical signals for quantifying target molecule concentration. However, the low receptor density and the use of complex surface chemistry in receptors immobilization on transducers are common bottlenecks in the current biosensor development, adding to the cost, complexity and time. This dissertation presents the development of selective macromolecular Tobacco mosaic virus-like particle (TMV VLP) biosensing receptor, and the microsystem integration of VLPs in microfabricated electrochemical biosensors for rapid and performance-enhanced chemical and biological sensing. Two constructs of VLPs carrying different receptor peptides targeting at 2,4,6-trinitrotoluene (TNT) explosive or anti-FLAG antibody are successfully bioengineered. The VLP-based TNT electrochemical sensor utilizes unique diffusion modulation method enabled by biological binding between target TNT and receptor VLP. The method avoids the influence from any interfering species and environmental background signals, making it extremely suitable for directly quantifying the TNT level in a sample. It is also a rapid method that does not need any sensor surface functionalization process. For antibody sensing, the VLPs carrying both antibody binding peptides and cysteine residues are assembled onto the gold electrodes of an impedance microsensor. With two-phase immunoassays, the VLP-based impedance sensor is able to quantify antibody concentrations down to 9.1 ng/mL. A capillary microfluidics and impedance sensor integrated microsystem is developed to further accelerate the process of VLP assembly on sensors and improve the sensitivity. Open channel capillary micropumps and stop-valves facilitate localized and evaporation-assisted VLP assembly on sensor electrodes within 6 minutes. The VLP-functionalized impedance sensor is capable of label-free sensing of antibodies with the detection limit of 8.8 ng/mL within 5 minutes after sensor functionalization, demonstrating great potential of VLP-based sensors for rapid and on-demand chemical and biological sensing.

Detection of explosive vapors using organic thin-film transistors

Field effect transistors (FETs) based on organic materials were investigated as sensors for detecting 2,4,6-trinitrotoluene (TNT) vapors. Several FET devices were fabricated using two types of semiconducting organic materials, solution processed polymers deposited by spin coating and, oligomers (or small molecules) deposited by vacuum sublimation. When vapors of nitroaromatic compounds bind to thin films of organic materials which form the transistor channel, the conductivity of the thin film increases and changes the transistor electrical characteristic. The use of the amplifying properties of the transistor represents a major advantage over conventional techniques based on simple changes of resistance in polymers frequently used in electronic noses.