Natural Biodegradation Processes Research Articles

Extremophilic Microbes for Environmental Bioremediation: A Review

Bioremediation using extremophilic microbes has gained public attention due to their unique ability to thrive in various extreme environments through their natural biological process. Extremophilic microbes provide an effective, sustainable, and cost-efficient strategy to remediate toxic environmental pollutants under extreme conditions. Extremophilic microbes are categorized based on their capability to adapt and grow in diverse extreme environments, encompassing various microbes with distinct adaptive traits. Some of the extremophilic microbes include thermophiles, hyperthermophiles, psychrophiles, acidophiles, alkaliphiles, halophiles, piezophiles, metallotolerant, toxitolerant, radioresistant, and micro-aerophiles. Several bioremediation techniques include bioaugmentation, bioleaching, biosorption, bioprecipitation, bio-reduction, and many more. Bioaugmentation enhances natural biodegradation processes; bioleaching involves the oxidation of metal sulfides; biosorption focuses on metal adsorption onto biomass surfaces; bioprecipitation is the transformation of metal ions into solid precipitates; bio-reduction is the reduction of metal ions to less toxic or less soluble structures. Despite all the benefits of bioremediation using extremophilic microbes, it still has shortcomings and challenges, including complex maintenance, ethical concerns, and limited scalability, which require ongoing research to optimize their application in environmental pollution treatment. Further studies are needed to focus on understanding their ecology, gene expression, and metabolism to ensure sustainability and effectiveness on a global scale.

Identification and Characterization of a New Serratia proteamaculans Strain That Naturally Produces Significant Amount of Extracellular Laccase.

Natural biodegradation processes hold promises for the conversion of agro-industrial lignocellulosic biomaterials into biofuels and fine chemicals through lignin-degrading enzymes. The high cost and low stability of these enzymes remain a significant challenge to economic lignocellulosic biomass conversion. Wood-degrading microorganisms are a great source for novel enzyme discoveries. In this study, the decomposed wood samples were screened, and a promising γ-proteobacterial strain that naturally secreted a significant amount of laccase enzyme was isolated and identified as Serratia proteamaculans AORB19 based on its phenotypic and genotypic characteristics. The laccase activities in culture medium of strain AORB19 were confirmed both qualitatively and quantitatively. Significant cultural parameters for laccase production under submerged conditions were identified following a one-factor-at-a-time (OFAT) methodology: temperature 30°C, pH 9, yeast extract (2 g/l), Li+, Cu2+, Ca2+, and Mn2+ (0.5 mM), and acetone (5%). Under the selected conditions, a 6-fold increase (73.3 U/L) in laccase production was achieved when compared with the initial culturing conditions (12.18 U/L). Furthermore, laccase production was enhanced under alkaline and mesophilic growth conditions in the presence of metal ions and organic solvents. The results of the study suggest the promising potential of the identified strain and its enzymes in the valorization of lignocellulosic wastes. Further optimization of culturing conditions to enhance the AORB19 strain laccase secretion, identification and characterization of the purified enzyme, and heterologous expression of the specific enzyme may lead to practical industrial and environmental applications.

Nitrofurazone Removal from Water Enhanced by Coupling Photocatalysis and Biodegradation.

(1) Background: Environmental contamination with antibiotics is particularly serious because the usual methods used in wastewater treatment plants turn out to be insufficient or ineffective. An interesting idea is to support natural biodegradation processes with physicochemical methods as well as with bioaugmentation with efficient microbial degraders. Hence, the aim of our study is evaluation of the effectiveness of different methods of nitrofurazone (NFZ) degradation: photolysis and photodegradation in the presence of two photocatalysts, the commercial TiO2-P25 and a self-obtained Fe3O4@SiO2/TiO2 magnetic photocatalyst. (2) Methods: The chemical nature of the photocatalysis products was investigated using a spectrometric method, and then, they were subjected to biodegradation using the strain Achromobacter xylosoxidans NFZ2. Additionally, the effects of the photodegradation products on bacterial cell surface properties and membranes were studied. (3) Results: Photocatalysis with TiO2-P25 allowed reduction of NFZ by over 90%, demonstrating that this method is twice as effective as photolysis alone. Moreover, the bacterial strain used proved to be effective in the removal of NFZ, as well as its intermediates. (4) Conclusions: The results indicated that photocatalysis alone or coupled with biodegradation with the strain A. xylosoxidans NFZ2 leads to efficient degradation and almost complete mineralization of NFZ.

Hydrocarbon-Degrading Bacteria Alcanivorax and Marinobacter Associated With Microalgae Pavlova lutheri and Nannochloropsis oculata.

Marine hydrocarbon-degrading bacteria play an important role in natural petroleum biodegradation processes and were initially associated with man-made oil spills or natural seeps. There is no full clarity though on what, in the absence of petroleum, their natural niches are. Few studies pointed at some marine microalgae that produce oleophilic compounds (alkanes, long-chain fatty acids, and alcohols) as potential natural hosts of these bacteria. We established Dansk crude oil-based enrichment cultures with photobioreactor-grown marine microalgae cultures Pavlova lutheri and Nannochloropsis oculata and analyzed the microbial succession using cultivation and SSU (16S) rRNA amplicon sequencing. We found that petroleum enforced a strong selection for members of Alpha- and Gamma-proteobacteria in both enrichment cultures with the prevalence of Alcanivorax and Marinobacter spp., well-known hydrocarbonoclastic bacteria. In total, 48 non-redundant bacterial strains were isolated and identified to represent genera Alcanivorax, Marinobacter, Thalassospira, Hyphomonas, Halomonas, Marinovum, Roseovarius, and Oleibacter, which were abundant in sequencing reads in both crude oil enrichments. Our assessment of public databases demonstrated some overlaps of geographical sites of isolation of Nannochloropsis and Pavlova with places of molecular detection and isolation of Alcanivorax and Marinobacter spp. Our study suggests that these globally important hydrocarbon-degrading bacteria are associated with P. lutheri and N. oculata.

Community-intrinsic properties enhance keratin degradation from bacterial consortia.

Although organic matter may accumulate sometimes (e.g. lignocellulose in peat bog), most natural biodegradation processes are completed until full mineralization. Such transformations are often achieved by the concerted action of communities of interacting microbes, involving different species each performing specific tasks. These interactions can give rise to novel "community-intrinsic" properties, through e.g. activation of so-called "silent genetic pathways" or synergistic interplay between microbial activities and functions. Here we studied the microbial community-based degradation of keratin, a recalcitrant biological material, by four soil isolates, which have previously been shown to display synergistic interactions during biofilm formation; Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans and Paenibacillus amylolyticus. We observed enhanced keratin weight loss in cultures with X. retroflexus, both in dual and four-species co-cultures, as compared to expected keratin degradation by X. retroflexus alone. Additional community intrinsic properties included accelerated keratin degradation rates and increased biofilm formation on keratin particles. Comparison of secretome profiles of X. retroflexus mono-cultures to co-cultures revealed that certain proteases (e.g. serine protease S08) were significantly more abundant in mono-cultures, whereas co-cultures had an increased abundance of proteins related to maintaining the redox environment, e.g. glutathione peroxidase. Hence, one of the mechanisms related to the community intrinsic properties, leading to enhanced degradation from co-cultures, might be related to a switch from sulfitolytic to proteolytic functions between mono- and co-cultures, respectively.

Petroleum Hydrocarbon Contamination in Terrestrial Ecosystems-Fate and Microbial Responses.

Petroleum hydrocarbons represent the most frequent environmental contaminant. The introduction of petroleum hydrocarbons into a pristine environment immediately changes the nature of that environment, resulting in reduced ecosystem functionality. Natural attenuation represents the single, most important biological process which removes petroleum hydrocarbons from the environment. It is a process where microorganisms present at the site degrade the organic contaminants without the input of external bioremediation enhancers (i.e., electron donors, electron acceptors, other microorganisms or nutrients). So successful is this natural attenuation process that in environmental biotechnology, bioremediation has developed steadily over the past 50 years based on this natural biodegradation process. Bioremediation is recognized as the most environmentally friendly remediation approach for the removal of petroleum hydrocarbons from an environment as it does not require intensive chemical, mechanical, and costly interventions. However, it is under-utilized as a commercial remediation strategy due to incomplete hydrocarbon catabolism and lengthy remediation times when compared with rival technologies. This review aims to describe the fate of petroleum hydrocarbons in the environment and discuss their interactions with abiotic and biotic components of the environment under both aerobic and anaerobic conditions. Furthermore, the mechanisms for dealing with petroleum hydrocarbon contamination in the environment will be examined. When petroleum hydrocarbons contaminate land, they start to interact with its surrounding, including physical (dispersion), physiochemical (evaporation, dissolution, sorption), chemical (photo-oxidation, auto-oxidation), and biological (plant and microbial catabolism of hydrocarbons) interactions. As microorganism (including bacteria and fungi) play an important role in the degradation of petroleum hydrocarbons, investigations into the microbial communities within contaminated soils is essential for any bioremediation project. This review highlights the fate of petroleum hydrocarbons in tertial environments, as well as the contributions of different microbial consortia for optimum petroleum hydrocarbon bioremediation potential. The impact of high-throughput metagenomic sequencing in determining the underlying degradation mechanisms is also discussed. This knowledge will aid the development of more efficient, cost-effective commercial bioremediation technologies.

Modelo matemático para estimativa da depleção natural de hidrocarbonetos de petróleo a partir de perfis verticais de temperatura

Em áreas contaminadas os hidrocarbonetos de petróleo são encontrados na forma de líquido imiscível menos denso que a água (Light Non-Aqueous Phase Liquids – LNAPL). O processo de biodegradação natural desses contaminantes é conhecido como depleção natural na zona da fonte, do inglês Natural Source Zone Depletion (NSZD). Para sua aplicação, é necessária a medição das taxas de NSZD, de forma a demonstrar que a eficácia da biodegradação natural do LNAPL como uma solução eficaz, econômica e sustentável na gestão de passivos. Estudos recentes apresentam relações diretas entre a temperatura do solo e a ocorrência da NSZD. Nesse contexto, o objetivo desse trabalho é apresentar um novo modelo para estimar a depleção da massa de LNAPL em função da variação de temperatura na fonte de contaminação. Com base na geração de dados sintéticos de temperatura do solo, foram comparados os resultados do modelo desenvolvido com os resultados dos modelos propostos por Warren e Bekins (2015) e Stockwell (2015). A análise comparativa revelou que os modelos de Warren e Bekins (2015) e Stockwell (2015) mediram apenas 30 e 51% do calor na zona da fonte de contaminação, respectivamente. Os resultados da comparação apontam para a importância em se considerar a variação vertical dos parâmetros térmicos do meio poroso na zona da fonte, em particular a condutividade térmica, no cálculo do transporte do calor do solo.

Biostimulation of in situ microbial degradation processes in organically-enriched sediments mitigates the impact of aquaculture

Fish farm deposition, resulting in organic matter accumulation on bottom sediments, has been identified as among the main phenomena causing negative environmental impacts in aquaculture. An in situ bioremediation treatment was carried out in order to reduce the organic matter accumulation in the fish farm sediments by promoting the natural microbial biodegradation processes. To assess the effect of the treatment, the concentration of organic matter in the sediment and its microbial degradation, as well as the response of the benthic prokaryotic community, were investigated. The results showed a significant effect of the treatment in stimulating microbial degradation rates, and the consequent decrease in the concentration of biochemical components beneath the cages during the treatment. During the bioremediation process, the prokaryotic community in the fish farm sediment responded to the overall improvement of the sediment conditions by showing the decrease of certain anaerobic taxa (e.g. Clostridiales, Acidaminobacteraceae and Caldilinaceae). This suggested that the bioactivator was effective in promoting a shift from an anaerobic to an aerobic metabolism in the prokaryotic community. However, the larger importance of Lachnospiraceae (members of the gut and faecal microbiota of the farmed fishes) in treated compared to non-treated sediments suggested that the bioactivator was not efficient in reducing the accumulation of faecal bacteria from the farmed fishes. Our results indicate that bioremediation is a promising tool to mitigate the aquaculture impact in fish farm sediments, and that further research needs to be oriented to identifying more successful interventions able to specifically targetalso fish-faeces related microbes.

DNA stable-isotope probing identifies uncultivated members of Pseudonocardia associated with biodegradation of pyrene in agricultural soil.

Identifying functional microorganisms involved in the degradation of high-molecular-mass polycyclic aromatic hydrocarbons (HMM-PAHs) in agricultural soil environments could assist in developing bioremediation strategies for soil PAH contamination. Active populations of HMM-PAH degraders in agricultural soils are currently poorly understood. In this study, we identified aerobic pyrene-degrading bacteria in agricultural and industrial soils by [13C]pyrene incubations followed by DNA stable-isotope probing and high-throughput sequencing. More than 80% of pyrene was degraded during an incubation time of 35 days in both soils, with slower mineralization rates observed in agricultural soil compared with industrial soil. Members of the Pseudonocardia genus, not previously implicated in pyrene degradation, were the dominant pyrene-degrading population in agricultural soil; their relative abundance increased by three orders of magnitude. In industrial soil, Arthrobacter sp. appeared as the major pyrene degraders, while Pseudonocardia was not detectable. Mycobacterium, a group of well-known pyrene degraders, was found to be active in pyrene degradation in both soils. These results highlight the role of uncultivated members of Pseudonocardia in natural PAH biodegradation processes and expand our understanding of the metabolic potential of uncultivated microorganisms for bioremediation applications in agricultural soils.

Self-healing capacity of deep-sea ecosystems affected by petroleum hydrocarbons: Understanding microbial oil degradation at hydrocarbon seeps is key to sustainable bioremediation protocols.

Crude oil or petroleum is a naturally occurring liquid that was formed in geological sediments from organic material under high hydrostatic pressure (HP). It has enormous economic importance as the basis for fuels, plastics, and a huge range of chemicals; the global economy consumes about 30 billion barrels of oil, or 4.8 cubic kilometers, each year. Much of this annual production comes from offshore oilfields and/or is shipped across the world, which poses a considerable risk of accidents and oil spills that contaminate the marine environment. The Exxon Valdez (1989), Prestige (2002), or Deepwater Horizon (DWH) offshore platform (2010) disasters affected huge areas of the oceans and adjacent shores with devastating impact on the fauna and flora. There is therefore huge interest in technologies to clean up spilled oil at shores and in the deep seas. This in turn has triggered interest in natural biodegradation processes by microorganisms that are able to break down oil and thereby remove it from the environment. These oil‐consuming archaea and bacteria thrive around natural marine hydrocarbon seepages, such as the spectacular hydrothermal black smokers or the cold hydrocarbon seeps that were first discovered in the Gulf of Mexico and in subduction zones of the Pacific Ocean [1]. Recent research showed that these hydrocarbon springs at depths of 200–3,500 m below surface level (bsl) fuel fantastic and highly diverse deep‐sea ecosystems, spanning from asphalt and oil seeps, hypersaline lakes, and gas chimneys, to mud volcanoes and pockmarks. The amount of oil that is naturally entering the oceans at these sites is estimated to be more than 700 million liters per year [2]. In contrast, anthropogenic oil spills into marine environments are estimated to amount to more than 120 million liters per year [2]. The main causes are routine operations—drilling, …

Bacteria capable of degrading anthracene, phenanthrene, and fluoranthene as revealed by DNA based stable-isotope probing in a forest soil

Information on microorganisms possessing the ability to metabolize different polycyclic aromatic hydrocarbons (PAHs) in complex environments helps in understanding PAHs behavior in natural environment and developing bioremediation strategies. In the present study, stable-isotope probing (SIP) was applied to investigate degraders of PAHs in a forest soil with the addition of individually (13)C-labeled phenanthrene, anthracene, and fluoranthene. Three distinct phylotypes were identified as the active phenanthrene-, anthracene- and fluoranthene-degrading bacteria. The putative phenanthrene degraders were classified as belonging to the genus Sphingomona. For anthracene, bacteria of the genus Rhodanobacter were the putative degraders, and in the microcosm amended with fluoranthene, the putative degraders were identified as belonging to the phylum Acidobacteria. Our results from DNA-SIP are the first to directly link Rhodanobacter- and Acidobacteria-related bacteria with anthracene and fluoranthene degradation, respectively. The results also illustrate the specificity and diversity of three- and four-ring PAHs degraders in forest soil, contributes to our understanding on natural PAHs biodegradation processes, and also proves the feasibility and practicality of DNA-based SIP for linking functions with identity especially uncultured microorganisms in complex microbial biota.

Value of Dispersants for Offshore-Oil-Spill Response

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper OTC 23359, ’The Value of Dispersants for Offshore-Oil-Spill Response,’ by Tim Nedwed, Tom Coolbaugh, and Greg Demarco, ExxonMobil, prepared for the 2012 Offshore Technology Conference, Houston, 30 April-3 May. The paper has not been peer reviewed. Each oil-spill-response option must be evaluated for operational limitations (e.g., sea state), potential effectiveness, environmental effects of the response option, applicability under various oil-spill scenarios (e.g., size and location of the spill), and health and safety of the responders. Alternative response tools are available to assist mechanical recovery in treating large offshore oil spills more effectively. There are misperceptions and misunderstandings about dispersants and their use; therefore, a description of dispersant use during the Deepwater Horizon incident is presented. Introduction The primary goal of any oil-spill response should be to minimize environmental harm. Although one expectation may be complete physical containment and removal of oil from the environment, this often is not possible (especially with large offshore spills) because of physical limitations of mechanical-recovery systems. Recovery operations during previous offshore spills collected only a small fraction of the spilled oil, even under ideal conditions. The Deepwater Horizon incident was no exception, with estimates indicating that only 3% of the oil was recovered mechanically. Recognizing significant limitations of mechanical recovery has led to developing alternative response tools—one of which is oil-spill dispersants. Oil-spill dispersants facilitate removal of oil from the environment by enhancing the natural biodegradation process. Dispersants break up a surface slick rapidly into micron-sized droplets that move into the water column. This action provides naturally occurring oil-degrading bacteria greater access to the oil by creating a dilute mixture of oil in water rather than a thick surface accumulation. Fortunately, oil-degrading bacteria exist in all marine environments, having evolved to degrade oil released by natural seeps. Dispersed oil dilutes rapidly, and concentrations above known toxicity thresholds persist for no more than a few hours after effective dispersant application. During the Deepwater Horizon incident, the amount of damage to the shorelines was far less than expected initially by the public. In many locations where oil did enter, marsh-grass recovery was apparent soon after the spill. This, and other evidence, suggests that a key reason for the limited shoreline effects during the incident was use of dispersants and, in particular, the subsea injection of dispersants at the wellhead. Oil Behavior During High-Flow Subsea Release The lower the viscosity of the oil, the higher the flow rate, and vice versa. Also, the ability to disperse oil is inversely related to the fluid’s viscosity, and oils remain readily dispersible with viscosities up to several thousand centipoises.

Maximum Saccharification of Cellulose Complex by an Enzyme Cocktail Supplemented with Cellulase from Newly Isolated Aspergillus fumigatus ECU0811

Either the natural biodegradation process or the industrial hydrolytic process requires synergistic interactions between various cellulases. However, it is sometimes impeded by low hydrolytic rate of existing cellulases and the lack of accessory enzymes. Herein, the ability of a commercial cellulase (Spezyme CP, from Genencor) to degrade steam explosion-pretreated corn stover was significantly improved. Firstly, a fungal cellulase producer, Aspergillus fumigatus ECU0811, was isolated from hundreds of soil samples. A 96-deep-well microscale-based platform was developed here to reduce the labor-intensive screening work and proved to be consistent with macroscale screening work. After optimization of fermentation, 3% corn cob could induce A. fumigatus ECU0811 to yield the highest cellulase production. Based on the high activities of β-glucosidase and xylanase by A. fumigatus ECU0811, 0.91 and 125U/mg protein, respectively, an enzyme cocktail was composed with a fixed dosage of Spezyme CP (CPCel) at 14.2filter paper units (FPU)/g glucan and varied dosages of A. fumigatus cellulase (AFCel). Consequently, the glucan-to-glucose conversion of corn stover was increased from 25.6% in the presence of CPCel at a dosage of 14.2FPU/g glucan to 99.5% in the presence of the enzyme cocktail (14.2FPU CPCel plus 1.21FPU AFCel per gram of glucan). On the other side, it reduced the total protein amount of CPCel by as much as tenfold, which extremely improved the hydrolytic rate of Spezyme CP and reduced its dosage.

Capacity of Straw for Repeated Binding of Crude Oil from Salt Water and Its Effect on Biodegradation

Using mass balance studies, we show that wheat straw readily bound several times its own weight in crude oil floating on salt water, the straw was reusable following repeated extractions of the oil with diesel, and its presence significantly increased the rate of biodegradation of the oil without the use of dispersants. Previous studies in this area have indicated a preference for synthetic polymeric materials because of their ability to bind greater amounts of oil and their reusability, as compared to organic materials including straw. However, it is clear that plastic leads to ecological problems in marine environments and does not typically provide bioavailable nutrients such as nitrogen or phosphorus to aid the natural oil biodegradation process. Our results suggest the advisability of using biomass such as straw for crude oil remediation.

In Situ Bioremediation of Naphthenic Acids Contaminated Tailing Pond Waters in the Athabasca Oil Sands Region—Demonstrated Field Studies and Plausible Options: A Review

Currently, there are three industrial plants that recover oil from the lower Athabasca oil sands area, and there are plans in the future for several additional mines. The extraction procedures produce large volumes of slurry wastes contaminated with naphthenic acids (NAs). Because of a “zero discharge” policy the oil sands companies do not release any extraction wastes from their leases. The process-affected waters and fluid tailings contaminated with NAs are contained on-site primarily in large settling ponds. These fluid wastes from the tailing ponds can be acutely and chronically toxic to aquatic organisms, and NAs have been associated with this toxicity. The huge tailings containment area must ultimately be reclaimed, and this is of major concern to the oil sands industry. Some reclamation options have been investigated by both pioneering industries (Syncrude Energy Inc. and Suncor Inc.) with mixed results. The bioremediation techniques have limited success to date in biodegrading NAs to levels below 19 mg/L. Some tailing pond waters have been stored for more than 10 years, and it appears that the remaining high molecular weight NAs are refractory to the natural biodegradation process in the ponds. Some plausible options to further degrade the NAs in the tailings pond water include: bioaugmentation with bacteria selected to degrade the more refractory classes of NAs; the use of attachment materials such as clays to concentrate both the NA and the NA-degrading bacteria in their surfaces and/or pores; synergistic association between algae and bacteria consortia to promote efficient aerobic degradation; and biostimulation with nutrients to promote the growth and activity of the microorganisms.

The nonionic surfactant pollution profile of Israel Mediterranean Sea coastal water

Anionic and nonionic surfactants, as core components of detergent formulations, contribute significantly to the pollution profile of sewage and wastewaters of all kinds. In Israel about 15% of the total amount of ca. 4×108 m3/year of sewage is discharged, directly, or via receiving streams/rivers, into the Mediterranean Sea. Based on our previous findings that about 85% of the nonionic surfactants in the country's sewage are nonbiodegradable alkylphenol-based ethoxylates, we have undertaken this study, aiming at mapping the receiving eastern Mediterranean seawater with respect to its nonionic surfactant pollution profile. The total concentrations of nonionic surfactants were found – via reverse phase HPLC determinations – to be within the range of 4.2–25.0 ppb in seawater samples taken 2–3 m off the coastline at those locations where sewage-containing streams flow into the sea. Thus, neither the existing sewage treatment facilities nor natural biodegradation processes in receiving surface water systems are capable of avoiding this coastal water pollution. The potential estrogenic health risk of such concentrations of the anthropogenic EPEOs is dependent, among other things, on their specific homological distribution, biodegradation rate (slower for those having >10 EO units) and survival.

Evaluation of natural attenuation rate at a gasoline spill site

Contamination of groundwater by gasoline and other petroleum-derived hydrocarbons released from underground storage tanks (USTs) is a serious and widespread environmental problem. Natural attenuation is a passive remedial approach that depends upon natural processes to degrade and dissipate contaminants in soil and groundwater. Currently, in situ column technique, microcosm, and computer modeling have been applied for the natural attenuation rate calculation. However, the subsurface heterogeneity reduces the applicability of these techniques. In this study, a mass flux approach was used to calculate the contaminant mass reduction and field-scale decay rate at a gasoline spill site. The mass flux technique is a simplified mass balance procedure, which is accomplished using the differences in total contaminant mass flux across two cross-sections of the contaminant plume. The mass flux calculation shows that up to 87% of the dissolved total benzene, toluene, ethylbenzene, and xylene (BTEX) isomers removal was observed via natural attenuation at this site. The efficiency of natural biodegradation was evaluated by the in situ tracer method, and the first-order decay model was applied for the natural attenuation/biodegradation rate calculation. Results reveal that natural biodegradation was the major cause of the BTEX mass reduction among the natural attenuation processes, and approximately 88% of the BTEX removal was due to the natural biodegradation process. The calculated total BTEX first-order attenuation and biodegradation rates were 0.036 and 0.025% per day, respectively. Results suggest that the natural attenuation mechanisms can effectively contain the plume, and the mass flux method is useful in assessing the occurrence and efficiency of the natural attenuation process.

The nonionic surfactant pollution profile of Israels Mediterranean Sea coastal water

Anionic and nonionic surfactants, as core components of detergent formulations, contribute significantly to the pollution profile of sewage and wastewaters of all kinds. In Israel about 15% of the total amount of ca. 4 x 10(8) m3/year of sewage is discharged, directly, or via receiving streams/rivers, into the Mediterranean Sea. Based on our previous findings that about 85% of the nonionic surfactants in the country's sewage are nonbiodegradable alkylphenol-based ethoxylates, we have undertaken this study, aiming at mapping the receiving eastern Mediterranean seawater with respect to its nonionic surfactant pollution profile. The total concentrations of nonionic surfactants were found--via reverse phase HPLC determinations--to be within the range of 4.2-25.0 ppb in seawater samples taken 2-3 m off the coastline at those locations where sewage-containing streams flow into the sea. Thus, neither the existing sewage treatment facilities nor natural biodegradation processes in receiving surface water systems are capable of avoiding this coastal water pollution. The potential estrogenic health risk of such concentrations of the anthropogenic EPEOs is dependent, among other things, on their specific homological distribution, biodegradation rate (slower for those having > 10 EO units) and survival.

In Situ Bioremediation Strategies for Oiled Shoreline Environments

Despite advances in preventative measures, recent events have demonstrated that accidental oil spills at sea will still occur. While physical (e.g. booms and skimmers) and chemical (e.g. chemical dispersants) methods have been developed to recover and/or disperse oil spilled at sea, they are not 100% effective and are frequently limited by operational constraints attributed to sea state and/or nature of the contaminant. As a result, oil spills frequently impact shoreline environments. In situ bioremediation, the addition of substances or modification of habitat at contaminated sites to accelerate natural biodegradation processes, is now recognised as an alternative spill response technology for the remediation of these sites. Recommended for use following the physical removal of bulk oil, this treatment strategy has an operational advantage in that it breaks down and/or removes the residual contaminants in place. Laboratory experiments and field trials have demonstrated the feasibility and success of bioremediation strategies such as nutrient enrichment to enhance bacterial degradation of oil on cobble, sand beach and salt marsh environments. With improved knowledge of the factors that limit natural oil degradation rates, the feasibility of other strategies such as phytoremediation, enhanced oil-mineral fines interaction, and the addition of oxygen or alternative electron acceptors are now being evaluated. Laboratory and field test protocols are being refined for the selection of effective bioremediation agents and methods of application. It is recommended that future operational guidelines include real time product efficacy tests and environmental effects monitoring programs. Termination of treatment should be implemented when: 1) it is no longer effective; 2) the oil has degraded to acceptable biologically benign concentrations; or 3) toxicity due to the treatment is increasing.

A Field Experimentation on Bioremediation: Bioren

Most shoreline bioremediation strategies are based on the addition of limiting nutrients to contaminated environments to cause an acceleration of the natural biodegradation process. Before approval for operational use, these products designed to be used in the environment, should be validated in field trials to assure their efficiency in reducing residual contaminant concentrations and toxicity. This paper describes the design, implementation and preliminary results of an experimental field study to evaluate the effectiveness of the bioremediation agents BIOREN 1 and BIOREN 2 of interest to the EUREKA BIOREN program. The agents BIOREN 1 and 2 are proprietary formulations of nutrients synthesised from fish meal and they were proven effective in laboratory studies of the two granular nutrient formulations. BIOREN 1 is unique in that it is augmented with a biosurfactant. To provide equivalent nitrogen concentrations the quantities of BIOREN 1 and 2 added were respectively 10 and 14.4 % of the oil quantity. The results showed a “starter effect” for the formulation BIOREN 1: biodegradation was significantly enhanced during the first five weeks of the experiment; after that the enhancement was weaker and significant differences were not observed between treatments. These results may be attributed to the fact that significant nutrient depletion may not occur in small scale controlled spill experiments. In addition, it has been proven that oxygen availability limited biodegradation. There is a need to develop aeration techniques, such as raking, that aerate the sediment without further burying the pollutant. Final oil balance assessment proved to be very instructive as it is the main practical factor taken into consideration by the operational team: the aim of the shoreline cleaning operation remains to reduce oil sediment content.