Aerobic Bioremediation Research Articles

In situ microbial bioremediation of obsolete pesticides at their disposal sites

Soil pollution by pesticides is a global problem in many countries, including Kyrgyzstan. Currently, 50 storage facilities for obsolete banned pesticides exist, severely threatening the surrounding populations and environment. In this study, in situ bioremediation technology was used to remove pesticide contamination from soil around the storage facilities. Three conditions were tested: application of fertile soil and bioproduct, application of fertile soil and no bioproduct (Control 1), and application of fertile soil and no bioproduct (Control 2). An aerobic bioremediation approach was used: the treatment was applied directly to the contaminated soil. For the bioaugmentation, three selected active degrading bacterial species were used: Stenotrophomonas sp. (Ps-B strain), L. fusiformis (SA-4 strain) and E. cloacae (SB-2 strain). Regular aeration, loosening and watering were performed during the subsequent months to create the conditions required to activate the local microflora and the degrading activity of the bacterial species in the bioproduct. The bioproduct of three active bacteria species has demonstrated a high pesticide decomposition effect. The pesticides were degraded from 85.6 to 99.0 ± 0.05% within six months of initiating the bioremediation process. The efficiency of the degradation process depended on optimum atmospheric conditions, that is, temperature, pH, and moisture content of the soil. Our study recommends using the agrotechnical and biotechnological approach for moderately pesticide-polluted soils and pesticide storage areas.

Simulated bio-slurry reactor for bioremediation of highly contaminated soils by 2,4,6-trinitrotoluene (TNT)

The widespread use of 2,4,6-trinitrotoluene (TNT) in military sites causes serious soil contamination problems. In this study, various additions of glucose, glycerol, and activated sludge were tested under laboratory conditions in a simulated bio-slurry reactor for bioremediation of soil from highly TNT-contaminated sites. The results showed that the addition of both glucose and glycerol as electron donors could efficiently promote microbial degradation of TNT. The co-addition of glycerol and sludge resulted in 65.2% total removal of TNT in the soil (2.76 × 102 mg/kg) and 79.8% total removal of TNT in the soil (1.35 × 102 mg/kg), respectively. After 39 days of incubation with glucose and sludge, the removal of TNT reached 86.3% in the most seriously polluted soil (2.83 × 103 mg/kg). 16S rRNA sequencing for bacteria showed that the addition of glucose and glycerol significantly stimulated the growth of Enterobacteriaceae and Pseudomonas populations, respectively, which dominated the post-degradation soil microbial community. The bioavailability concentration of TNT extracted with (2-Hydroxypropyl)-β-cyclodextrin (HPβCD) rapidly decreased to very low levels during remediation seems to provide an explanation for complete degradation of TNT could not be achieved even in soils with relatively lower contamination. In addition, adequate electron donors are necessary to ensure the sustainable bioremediation of TNT-contaminated soil with high concentrations compared to surfactant. This work suggests that co-addition of glycerol (or glucose) and sludge is a desirable strategy for aerobic bioremediation of sites contaminated with high concentrations of TNT.

Aerobic biodegradation of chlorinated ethenes by Pseudonocardia sp. D17: Biodegradation ability without auxiliary substrates and concurrent biodegradation with 1,4-dioxane

Bioremediation is a promising approach for mitigating commingled contaminations of chlorinated ethenes (CEs) and 1,4-dioxane (DX). However, aerobic bioremediation to simultaneously remove CEs and DX remains challenging. This study aimed to explore the ability of Pseudonocardia sp. D17 (D17) to aerobically degrade CEs and its applicability for concurrent removal of CEs and DX. Aerobic degradation experiments of individual CEs revealed that D17 could degrade trichloroethene (TCE), three isomers of dichloroethene (DCE), and vinyl chloride (VC), and the trend of its degradation ability was cis-1,2-DCE (cDCE) > VC > TCE >trans-1,2-DCE > 1,1-DCE. Notably, the CE-degrading activity of D17 was expressed even without any auxiliary substrates. Further, when TCE, cDCE, or VC was co-present with DX (each at 1 mg/L), D17 could degrade both compounds without any significant inhibition (for TCE and cDCE) or with only a transient and reversible suspension of its DX degradation ability (for VC). These findings indicated that D17 is a promising agent for the aerobic bioremediation of CEs and DX co-contamination and provide novel insights into the future development of efficient aerobic bioremediation strategies.

Dual metabolic pathways co-determine the efficient aerobic biodegradation of phenol in Cupriavidus nantongensis X1

Phenol, as an important chemical raw material, often exists in wastewater from chemical plants and pollutes soil and groundwater. Aerobic biodegradation is a promising method for remediation of phenolic wastewater. In this study, degradation characteristics and mechanisms of phenol in Cupriavidus nantongensis X1 were explored. Strain X1 could completely degrade 1.5 mM phenol within 32 h and use it as the sole carbon source for growth. The optimal degradation temperature and pH for phenol by strain X1 were 30 °C and 7.0. The detection of 3-oxoadipate and 4-hydroxy-2-oxopentanoate indicated that dual metabolic pathways coexist in strain X1 for phenol degradation, ortho- and meta-pathway. Genome and transcriptome sequencing revealed the whole gene clusters for phenol biomineralization, in which C12O and C23O were key enzymes in two metabolic pathways. The ribosome proteins were also involved in the regulation of phenol degradation. Meanwhile, the degradation activities of enzyme C23O was 188-fold higher than that of C12O in vitro, which indicated that the meta-pathway was more efficient than ortho-pathway for catechol degradation in strain X1. This study provides an efficient strain resource for phenol degradation, and the discovery of dual metabolic pathways provides new insight into the aerobic biological metabolism and bioremediation of phenol.

Piloting Activities for the Design of a Large-scale Biobarrier Involving In Situ Sequential Anaerobic–aerobic Bioremediation of Organochlorides and Hydrocarbons

In situ bioremediation (ISB) is a widely accepted method for eradicating petroleum hydrocarbons (PHCs) and chlorinated aliphatic hydrocarbons (CAHs) from contaminated aquifers. To achieve full removal of all toxic compounds that originated from microbial degradation, sequential anaerobic/aerobic bioremediation systems are recommended. While several works based on laboratory analyses targeting sequential bioremediation have been documented, examples of sequential ISB are limited. The purpose of this study is to report and analyze the results obtained from the multiscale characterization activities propaedeutic to the construction of Italy’s largest (> 400 m long) sequential ISB system. The rich wealth of information produced during this study provides a useful example that can be followed for the construction of new sequential ISBs. The system was set up to remediate a solute plume containing PHCs and CAHs in an alluvial aquifer in Italy. Microcosm experiments were carried out to determine the biodegradation potential under anaerobic and aerobic conditions. In situ tests were performed by installing two 40-m-long pilot biobarriers for sequential anaerobic and aerobic degradation intercepting part of the contamination plume. These experiments pointed out the need of adding biostimulating compounds to accelerate the biodegradation process, under both aerobic and anaerobic conditions. In situ tests showed removal efficiencies of up to 95 and 99% for total CAHs and PHCs, respectively, proving the feasibility of the full-scale ISB system. Apparent discrepancies between laboratory and in situ tests can be ascribed to scale effects and aquifer heterogeneities.

Opportunities and critical issues related to the use of amendments as sustainable remediation techniques

This study aims to analyse the opportunities and critical issues related to the use of amendments as remediation techniques. The performance of amendments (Aerobic Bioremediation, In Situ Chemical Oxidation and Surfactants) was compared with the performance of other groundwater remediation technologies (Air Sparging, Pump&Treat, Multi-Phase Extraction, Pump&Reinjection, Monitoring Natural Attenuation) based on a dataset of 180 contaminated sites. The considered factors are: effectiveness of the remediation; cost to remediate; operational time; environmental sustainability. The occurrence and types of amendment-related issues analyzed were studied on the 40 sites where the amendments had been applied. Issues occurred in 20% of the 40 analyzed cases and consisted of: a) partial or total occlusion of the monitoring wells and by-product formation, for example heavy metals (5%); b) uncontrolled increase in contaminant concentrations and potential downstream migration (8%); c) byproduct formation without well obstruction (7%). For each critical event, a detailed analysis was conducted to understand the processes (pH-Eh equilibria, contaminant desorption, hydraulic conductivity reduction), to highlight the design and procedural gaps (surplus of amendment, injection method selection, contaminant removal by purge). However, it has been observed that the issues can be avoided or mitigated with an accurate design, pilot tests performance, with the application of delivery and monitoring protocols, and at least with a prompt response adopting a corrective action plan, if necessary. The use of amendments turns out to be an effective solution: in 64% of the analyzed sites, it led to a significative reduction of the contamination within one year from the application. The cost is about one third if compared to the average of the other technologies. The operational time is about half the average operational time of the other technologies. Based on the results of sustainability analysis, amendments technologies reduce the production of waste, energy and water consumption, and they minimize air emissions. Considering the sustainability in its broadest sense (environmental, economic, and temporal), it is possible to state that the remediation by amendments is the most sustainable and would meet the interest of all the stakeholders.

Sulfolane in contaminated sites: environmental toxicity and bioremediation technologies

Sulfolane is widely used around the world as an industrial solvent for purifying sour natural gas. However, because of accidental spillage and improper on-site storage/disposal procedures, reports of groundwater, aquifer, and soil contaminations have raised concerns about its potential impacts on humans and the ecosystem. As a contaminant of emerging concern, there is a lack of information on the human toxicity of sulfolane. Several bioremediation technologies have been conducted to assess the biodegradation potential of sulfolane in contaminated groundwater and soils. This review presents and discusses the available literature on the toxicity of sulfolane, which could be useful for developing proper sulfolane guidelines in different media. The oral LD50 of sulfolane varies from 0.6 to 3.5 g·(kg body mass)–1 for different mammalian species, including guinea pig, mouse, rabbit, and rat. In addition, we also review the various sulfolane bioremediation studies to date, highlighting the efficacy of aerobic versus anaerobic bioremediation of sulfolane at contaminated sites. The zero-order biodegradation rate of sulfolane varies from 0.033 to 190 mg·L–1·day–1 depending on the initial concentration of sulfolane, nutrients, oxygen levels, temperature, and other parameters. Effective aerobic treatment technologies can lead to the complete mineralization of sulfolane with sulfuric acid as its major end by-product. Furthermore, the application of aerobic granulation as a promising biotechnology for sulfolane biodegradation is also discussed. This review further discusses the significance of utilizing sulfolane-degrading bacteria to reduce treatment times and presents information for future researchers and scientists on the specific isolates recorded.

In Situ Aerobic Bioremediation of Sediments Polluted with Petroleum Hydrocarbons: A Critical Review

Oil pollution has been a worldwide concern especially in environments where treatment is quite difficult to apply. Marine polluted sediments, in particular, constitute one of the most recalcitrant environments for bioremediation and are often the final repository of petroleum contaminants, as a result of runoff and deposition. Aerobic hydrocarbon degraders present in the sediments are tackling the pollution under oxygen-limited or oxygen-depleted conditions. Research has focused on new ways to enhance bioremediation under anoxic conditions, however aerobic bioremediation is faster, and hence more effort should be made to sustain oxygen concentration levels. In this review, the different bioremediation techniques used for the decontamination of marine sediments are briefly discussed, and focus is primarily given to the different oxygenation methods used for enhancing aerobic bioremediation and the aeration methods that are suitable for in situ application, as well as state of the art technologies that make in situ aeration an appealing approach. Based on the technologies analyzed, suggestions are made for sediment bioremediation techniques in different marine environments.

Integrated use of chemical and geophysical monitoring to study the diesel oil biodegradation in microcosms with different operative conditions

This study aimed to monitor the aerobic bioremediation of diesel oil-contaminated soil by measuring: a) the CO2 production; 2) the fluorescein production; 3) the residual diesel oil concentration. Moreover, the complex dielectric permittivity was monitored through an open-ended coaxial cable. Several microcosms were prepared, changing the water content (u% = 8–15% by weight), the carbon to nitrogen ratio (C/N = 20–450), and the soil amount (200 and 800 g of dry soil). The cumulative CO2 and fluorescein production showed similar trends, but different values since these two parameters reflect different features of the biological process occurring within each microcosm. The diesel oil removal efficiency depended on the microcosm characteristics. After 84 days, in the microcosms with 200 g of dry soil, the highest removal efficiency was achieved with a water content of 8% by weight and C/N = 120, while in the microcosms with 800 g of dry soil the best result was achieved with the water content equal to 12% by weight and C/N = 100. In the tested soil, the bioremediation process is efficient if the water content is in the range 8–12% by weight, and C/N is in the range 100–180; under these operative conditions, the diesel oil removal efficiency was about 65–70% after 84 days. The dielectric permittivity was monitored in microcosms with 200 g of dry soil. The open-ended coaxial cable detected significant variations of both the real and the imaginary component of the dielectric permittivity during the bioremediation process, due to the physical and chemical changes that occurred within the microcosms.

Selective Removal of Diesel Oil Hydrocarbons in Aerobic Bioremediation

In soil bioremediation, the main target is the removal of pollutants to the maximum extent. Careful monitoring of pollution concentration provides information about the process efficacy and removal efficiency. Moreover, a detailed analysis of residual pollution composition provides a detailed picture of single compound removal or presence, especially of interest when pollution is constituted by a mixture of chemical species. This paper shows the first results of a study on the speciation of diesel oil compound removal from soils by aerobic remediation. The experimental study was carried out in a microcosm using indigenous microorganisms and adopting the biostimulation strategy with a mineral salt medium for bacteria. The microcosm contained 200 g of dry soil and 14 g of diesel oil with a carbon to nitrogen ratio (C/N) equal to 180 and water content (u%) equal to 12% by mass. The residual pollution concentration in soil was monitored for 138 days to evaluate both the overall removal efficiency and that for the main groups of hydrocarbons. The results showed that the pollution composition changed during the test because of the different rate of metabolization for the single compounds: the overall removal efficiency was about 65%, and that of different hydrocarbon clusters was between 53% and 88%. The monitoring data also allowed the kinetic study of the degradation process, which was better modeled by a second-order kinetic model than by a first-order one. These findings were confirmed by analyzing other microcosms with different operative conditions (C/N = 120, 180 and u% = 8%, 12%, 15% by mass). The proposed methodology may be useful for the evaluation of compliance to concentration limits imposed by law.

Application of the Principal Component Analysis (PCA) to aerobic biodegradation process

The Principal Component Analysis (PCA) is a method widely used to process experimental data. The PCA aims to reduce the dimensionality of a data set composed of many interrelated variables, preserving the variation as much as possible. This can be achieved by transforming the data set to a new one, containing the principal components (PCs), which are uncorrelated, and which maximize the variance of the original data. In this study, the PCA was applied to experimental tests on aerobic bioremediation of soil polluted with diesel oil. Twelve microcosms (200 g of soil) were prepared, polluted with commercial diesel oil (70 g/kg of dry soil), and hydrated with a mineral salt solution suitable to stimulate the indigenous bacteria. The aerobic process for diesel oil degradation was studied changing two operative parameters, namely, water content (u%) and carbon to nitrogen ratio (C/N). Three values of water content (u% = 8%, 12% and 15% by weight) and four of carbon to nitrogen ratio (C/N = 60, 120, 180 and 300) were tested. The microcosms were monitored for 30 days by the measurements of these parameters: 1) the CO2 production, to evaluate the microbial respiration, 2) the fluorescein production, to check the microbial activity, and 3) the diesel oil concentration, to assess the pollutant degradation and calculate the removal efficiency. The Principal Component Analysis was done considering the water content values as variables and the carbon to nitrogen ones as systems to be analyzed. By a linear transformation, two principal components were achieved, namely PC1 and PC2. There sults for the CO2 production, fluorescein production, and diesel oil removal efficiency were used, and overall variances always over 94% were obtained. The results showed that two microcosms stood out from the others, namely:-the microcosm with u% = 12% b.w. and C/N = 180,sinceit gave the highest amount of CO2 and fluorescein;- the microcosm with u% = 8% b.w. and C/N = 120,due to the highest diesel oil removal efficiency.

New Frontiers of Anaerobic Hydrocarbon Biodegradation in the Multi-Omics Era.

The accumulation of petroleum hydrocarbons in the environment substantially endangers terrestrial and aquatic ecosystems. Many microbial strains have been recognized to utilize aliphatic and aromatic hydrocarbons under aerobic conditions. Nevertheless, most of these pollutants are transferred by natural processes, including rain, into the underground anaerobic zones where their degradation is much more problematic. In oxic zones, anaerobic microenvironments can be formed as a consequence of the intensive respiratory activities of (facultative) aerobic microbes. Even though aerobic bioremediation has been well-characterized over the past few decades, ample research is yet to be done in the field of anaerobic hydrocarbon biodegradation. With the emergence of high-throughput techniques, known as omics (e.g., genomics and metagenomics), the individual biodegraders, hydrocarbon-degrading microbial communities and metabolic pathways, interactions can be described at a contaminated site. Omics approaches provide the opportunity to examine single microorganisms or microbial communities at the system level and elucidate the metabolic networks, interspecies interactions during hydrocarbon mineralization. Metatranscriptomics and metaproteomics, for example, can shed light on the active genes and proteins and functional importance of the less abundant species. Moreover, novel unculturable hydrocarbon-degrading strains and enzymes can be discovered and fit into the metabolic networks of the community. Our objective is to review the anaerobic hydrocarbon biodegradation processes, the most important hydrocarbon degraders and their diverse metabolic pathways, including the use of various terminal electron acceptors and various electron transfer processes. The review primarily focuses on the achievements obtained by the current high-throughput (multi-omics) techniques which opened new perspectives in understanding the processes at the system level including the metabolic routes of individual strains, metabolic/electric interaction of the members of microbial communities. Based on the multi-omics techniques, novel metabolic blocks can be designed and used for the construction of microbial strains/consortia for efficient removal of hydrocarbons in anaerobic zones.

Effects of Mercury II on Cupriavidus metallidurans Strain MSR33 during Mercury Bioremediation under Aerobic and Anaerobic Conditions

Mercury is a toxic element that harms organisms and disturbs biogeochemical cycles. Mercury bioremediation is based on the reduction of Hg (II) to Hg (0) by mercury-resistant bacteria. Cupriavidus metallidurans MSR33 possesses a broad-spectrum mercury resistance. This study aims to establish the effects of mercury on growth, oxygen uptake, and mercury removal parameters by C. metallidurans MSR33 in aqueous solution during aerobic and anaerobic mercury bioremediation. A new culture medium (GBC) was designed. The effects of mercury (II) (20 ppm) on growth parameters, oxygen uptake, and mercury removal were evaluated in GBC medium in a bioreactor (3 L) under aerobiosis. The anaerobic kinetics of mercury removal was evaluated by nitrogen replacement during mercury bioremediation in a bioreactor. Strain MSR33 reached a growth rate of µ = 0.43 h−1 in the bioreactor. Mercury inhibited oxygen uptake and bacterial growth; however, this inhibition was reversed after 5 h. Strain MSR33 was able to reduce Hg (II) under aerobic and anaerobic conditions, reaching, at 24 h, a metal removal of 97% and 71%, respectively. Therefore, oxygen was crucial for efficient mercury removal by this bacterium. Strain MSR33 was capable of tolerating the toxic effects of mercury (II) during aerobic bioremediation and recovered its metabolic activity.

Large-scale Application of Klozur® CR for the Treatment of an Aquifer Contaminated with Heavy Hydrocarbons and MTBE in Southern Italy

Klozur® CR is a combined remedy treatment technology consisting of Klozur® SP and PermeOx® Ultra. Klozur CR is a single, all-in-one formulated product that can be readily applied to either source areas or plumes with mixed petroleum and chlorinated solvents contamination. Klozur CR destroys contaminants in soil and groundwater by promoting three modes of action: Klozur activated persulfate chemical oxidation, aerobic bioremediation and anaerobic bioremediation. This technology was successfully applied to a site in southern Italy, contaminated by the storage and sale of fuels. The groundwater was contaminated by heavy chain hydrocarbons (TPH> 2500 μg / l) and MTBE (> 150 μg / l) in proximity to the reservoir park. During the site maintenance activities, the qualitative status of adjacent coastal waters was also verified, which, however, were found to be compliant. Previously the site used a pump and treat system, but it was unable to achieve remedial goals. Klozur CR was injected and within 4 months, the concentrations of the contaminants were found to have reached the remedial goals. In addition, monitoring data also confirmed enhanced ISCO conditions and enhanced aerobic bioremediation were present at the site.

Laboratory tests for aerobic bioremediation of the contaminated sites in the Czech Republic

Laboratory-scale testing methods applicable to evaluation of contaminated subsurface microbial communities are discussed in relation to their potential in supporting effective site bioremediation. Both culture-dependent and culture-independent techniques are considered here with special emphasis on their capacity to contribute to bioremediation system design, in optimal cases by providing information on contaminant degradation rates. In this regard, microbial soil respiration tests seem to be the most useful tool since microbial soil respiration is a sensitive and easily measurable parameter for determination of metabolic activity within the sample and is closely related to other microbial parameters such as microbial biomass.

Kinetics and Optimization by Response Surface Methodology of Aerobic Bioremediation. Geoelectrical Parameter Monitoring

This study aimed to investigate the kinetics of an aerobic bioremediation process of diesel oil removal by indigenous microorganisms, and to define the optimal operative conditions by means of response surface methodology. This was carried out by setting up a series of microcosms (200 g of soil), polluted with the same diesel oil concentration (70 g·kg−1 of soil), but with different water contents (u%) and carbon to nitrogen (C/N) ratios. The process was monitored by: (1) residual diesel oil concentration, to measure the removal efficiency, and (2) fluorescein production, to check the microbial activity. These two parameters were the objective variables used for the analysis of variance (ANOVA) and response surface methodology (RSM). The results allowed the interactions between u% and C/N to be defined and the optimal range to be adopted for each. The process kinetics was modeled with first- and second-order reaction rates; slightly better results were achieved for the second-order model in terms of parameter variability. Biological processes like degradation may have effects on dielectric properties of soil; an open-ended coaxial cable was used to measure the dielectric permittivity of microcosm matrices at the start and after 130 days of bioremediation. The evolution of the real and the imaginary components of dielectric permittivity provided results that supported the evidence of a biodegradation process in progress.

Distribution of Colloidal and Powdered Activated Carbon for the <i>in Situ</i> Treatment of Groundwater

The use of in situ technologies for the treatment of groundwater containing various compounds of concern are widely accepted. These technologies include chemical reduction, chemical oxidation, anaerobic and aerobic bioremediation, and adsorption, among others. One requirement for the successful application of these technologies is the delivery of the remedial reagent(s) to the compounds of concern. A rapidly evolving in situ technology is the injection of adsorptive media such as activated carbon and ion-exchange resin including powdered or colloidal activated carbon. Activated carbon has a long-demonstrated history of effectiveness for the removal of various organic and inorganic compounds in above ground water treatment systems. However, due to constraints related to the particle size and physical properties of the activated carbon, the in situ application of activated carbon has been limited. Recent developments in the manufacturing of activated carbon have created a smaller particle size allowing activated carbon to be applied in situ. To evaluate if powdered and colloidal activated carbon can be effectively distributed in aquifers, the two types of carbon were injected using direct push technology adjacent to each other at four sites with varying geology. Evaluation of distribution was completed by sampling the aquifer prior to and post-injection for total organic carbon. The results of the studies indicated that both forms of activated carbon were effectively delivered to the targeted injection zones with both carbon types being detected at least seven meters away from the point of injection. The colloidal form of the activated carbon showed good distribution throughout the four targeted zones of injection with 93 percent of the samples collected having colloidal activated carbon present within them whereas the powdered activated carbon cells were more susceptible to aquifer heterogeneity with only 67 percent of the samples collected having activated carbon present. Preferential accumulation of activated carbon was observed in high horizontal hydraulic conductivity seams, especially within the powdered activated carbon cells. These results suggested that the powdered form of activated carbon was more suspectable at the four sites to heterogeneity within the aquifer than the colloidal form of activated carbon. Sampling of monitoring well screens installed prior to the injection of the two forms of activated carbon showed preferential accumulation of powdered activated carbon within the sand pack, which could result in sampling bias.

Study of Environmental Concerns of Dyes and Recent Textile Effluents Treatment Technology: A Review

The textile industry is one of the significant industries which produces large amount of wastewater effluents all year. The kind of these effluents has the features of higher rate of BOD, COD, complex structure, color, great emission and hard degradation. If being directly discharged without treatment, it will cause a potential hazard to the aquatic ecosystem and human. This paper provides the literature information about the environmental concern and their toxicity effects as well as classification of dyes. This review will present the methods for the removal of dyes from aqueous solution and wastewater effluents. The various dye removal techniques are classified into biological, chemical, physical methods, in addition to combination treatments. Biological methods include aerobic and anaerobic degradation bioremediation by bacteria & fungi and algae, while chemical methods comprise coagulation or flocculation combined through floatation and filtration, precipitation, electro floatation, electro kinetic coagulation, conventional oxidation methods by oxidizing agents such as ozone, irradiation or electrochemical processes. Furthermore, physical technologies as adsorption, ion exchange and filtration coagulation methods.

Microremediation of tannery wastewater by siderophore producing marine bacteria

ABSTRACT The present study evaluated the microremediation potential of nine siderophore producing marine bacteria for hazardous raw tannery wastewater from common effluent treatment plant (CETP). Most of the pollutants detected in the wastewater were diminished after the bioremediation process. Further, among the three potent isolates selected for aerobic and anaerobic bioremediation study, Marinobacter hydrocarbonoclasticus demonstrated the highest bioremediation aerobically with a reduction in chromium (88%), sulphate (71%), phosphate (68%) and nitrate (57%). Notably, Nitratireductor kimnyeongensis could attack the effluent under both aerobic and anaerobic conditions as substantiated by statistically significant (p < .05) reduction in the pollutants [chromium (85%), sulphate (63%), Chemical Oxygen Demand (COD) (69%), phosphate (76%)]. From the study it is evident that the pollutant load reduction was achieved under both aerobic and anaerobic conditions, however, aerobic environment was more effective in reducing chromium, Biochemical Oxygen Demand (BOD), sulphate, nitrate and phosphate. The bioremediation efficiency was further confirmed by the bioassay experiments with plant and animal models where higher seed germination, greater plant length and biomass, as well as improved survival rate of Artemia nauplii for bioremediated wastewater was observed as compared to the untreated effluent indicating a significant reduction in toxicity. The results for simultaneous removal of multiple-toxicants thus signify effectiveness and ease of using the robust properties of these marine bacterial strains suggesting their potential application for bioremediation. Hence this could pave a promising way for an environment-friendly and economically feasible clean-up strategy for safer disposal of tannery wastewater.

In-situ bioremediation of soil pollution with electric heating temperature regulation Bio-Ventilation

The relation between activity of soil indigenous microorganisms and temperature is an important research topic. The method of low rate flow nutrition and oxygen injection to a soil by an electrokinetic technique is studied to be used in aerobic polluted soil bioremediation treatments. The proper temperature nutrient solution and oxygen could be heated and poured into the polluted soil to promote the growth of indigenous bacteria in the soil and improve the efficiency of degrading inorganic pollutants. The present study was conducted to clarify oxygen levels and soil temperature influence on Bio-Ventilation bioremediation technology.