Effects of Constant Electric Field on Biodegradation of Phenol by Free and Immobilized Cells of Bradyrhizobium japonicum 273

It is shown that bacteria Bradyrhizobium japonicum 273 were capable of degrading phenol at moderate concentrations either in a free cell culture or by immobilized cells on granulated activated carbon particles. The amount of degraded phenol was greater in an immobilized cell preparation than in a free culture. The application of a constant electric field during cultivation led to enhanced phenol biodegradation in a free culture and in immobilized cells on granulated activated carbon. The highest phenol removal efficiency was observed for an anode potential of 1.0 V/S.H.E. The effect was better pronounced in a free culture. The enzyme activities of free cells for phenol oxidation and benzene ring cleavage were very sensitive to the anode potential in the first two steps of the metabolic pathway of phenol biodegradation catalyzed by phenol hydroxylase—catechol-1,2-dioxygenase and catechol-2,3-dioxygenase. It was observed that at an anode potential of 0.8 V/S.H.E., the meta-pathway of cleavage of the benzene ring catalyzed by catechol-2,3-dioxygenase became competitive with the ortho-pathway, catalyzed by catechol-1,2-dioxygenase. The obtained results showed that the positive effect of constant electric field on phenol biodegradation was rather due to electric stimulation of enzyme activity than electrochemical anode oxidation.

The Effectiveness of Biostimulation, Bioaugmentation and Sorption-Biological Treatment of Soil Contaminated with Petroleum Products in the Russian Subarctic

The effectiveness of different bioremediation methods (biostimulation, bioaugmentation, the sorption-biological method) for the restoration of soil contaminated with petroleum products in the Russian Subarctic has been studied. The object of the study includes soil contaminated for 20 years with petroleum products. By laboratory experiment, we established five types of microfungi that most intensively decompose petroleum hydrocarbons: Penicillium canescens st. 1, Penicillium simplicissimum st. 1, Penicillum commune, Penicillium ochrochloron, and Penicillium restrictum. One day after the start of the experiment, 6 to 18% of the hydrocarbons decomposed: at 3 days, this was 16 to 49%; at 7 days, 40 to 73%; and at 10 days, 71 to 87%. Penicillium commune exhibited the greatest degrading activity throughout the experiment. For soils of light granulometric composition with a low content of organic matter, a more effective method of bioremediation is sorption-biological treatment using peat or granulated activated carbon: the content of hydrocarbons decreased by an average of 65%, which is 2.5 times more effective than without treatment. The sorbent not only binds hydrocarbons and their toxic metabolites but is also a carrier for hydrocarbon-oxidizing microorganisms and prevents nutrient leaching from the soil. High efficiency was noted due to the biostimulation of the native hydrocarbon-oxidizing microfungi and bacteria by mineral fertilizers and liming. An increase in the number of microfungi, bacteria and dehydrogenase activity indicate the presence of a certain microbial potential of the soil and the ability of the hydrocarbons to produce biochemical oxidation. The use of the considered methods of bioremediation will improve the ecological state of the contaminated area and further the gradual restoration of biodiversity.

SORBENT (GRANULATED ACTIVATED CARBON) REACTIVATION IN DUALMEDIA RAPID FILTERS TO OPTIMIZE THE QUALITY OF DRINKING WATER

Introduction. Water supply organizations are currently in need of innovative solutions and technologies based on the concept of the closed-loop resource cycle. The need for sustainable use of resources serves as the basis for changing the existing approach where worn-out resources are considered wastes. Materials and methods. In this paper, we show that it is expedient to restore the sorption properties of granulated activated carbon (GAC) by its reactivation and reuse in closed-loop recycling. We also present methods to study GAC properties and technology of reactivation. Results and discussion. Based on the results of the GAC samples’ analysis, it was found that, during reactivation, the mass content of each fraction changes with a strongly pronounced decrease in the content of large granules with a size of 1.18–2.00 mm and an increase in the content of small granules with a size of 0.60–1.00 mm. Besides, the apparent density of the sorption material changes and the volume of carbon that underwent two reactivations falls below 75%. Conclusion. GAC reactivation in dual-media rapid filters allows us to optimize not only the operating and financial expenses of the company but also those natural resources that would have been spent for the production of new carbon.

Adsorption performance and mechanisms of mercaptans removal from gasoline oil using core-shell AC-based adsorbents: Role of intra-particles space

Sulfur compound detection such as mercaptans in liquid fuels is undesirable because sulfur is the main sourcing emission of sulfur oxide (SOx) into the air. The use of activated carbon (AC) has proven to efficiently remove mercaptans. In the meantime, it is limited by the generation of the second pollution in oil, and the difficulties of recovery and regeneration. To address these issues, a core-shell structured AC with high mechanical strength and big intra-particles space were synthesized and demonstrated to efficiently remove organic pollutants from an aqueous solution without generation of the second pollution in our previous work. However, the performance, characteristics, and mechanism of mercaptans adsorption from gasoline oil by core-shell structured AC was still unclear. In this study, the mercaptans adsorption behaviors using core-shell powdered activated carbon (CSAC) and core-shell granulated activated carbon (CSGAC), along with raw PAC, PAC-core, raw GAC, and GAC-core were carried out. The results showed that both the CSAC and CSGAC adsorbents effectively removed sulfur-based pollutants and were provided with good recovery and recyclability without second pollution in gasoline oil. The CSGAC exhibited a higher mercaptans removal efficiency compared to those of CSAC as a result of the bigger intra-particles space. PAC-based adsorbents, presented the shrinking of removal efficiency after regeneration. The Pseudo-second-order kinetics and Langmuir isotherms models were dominated for mercaptans adsorption by both CSAC and CSGAC. Furthermore, the interactions between mercaptans and the composites were probably ascribed to the Van der Waals force, hydrophobic compatibility, pore texture, and π-π dispersion interaction.

THE DEVELOPMENT OF A NEW ADSORPTION-DESORPTION DEVICE

The aim of this work was to construct a new adsorption-desorption device based on the principle of separation of volatile organic compounds, e.g., ethanol. As an adsorbent, it is possible to use granulated activated carbon (GAC) in the adsorption and desorption process. In this study, two kinds of GACs were used and marked as GAC1 and GAC2. A particle size distribution and water vapour sorption for the selected GACs were measured. An experiment with distilled water was performed as a preliminary study of the new device’s functionality. After the determination of the time necessary for the adsorption and desorption, the experiments were carried out with a model mixture (5% v/v ethanol-water mixture), which resulted in a product with the ethanol content of 39.6 %. The main advantage of this device would be the potential competition of conventional distillation.

Rapid Two Stage Anaerobic Digestion of Nejayote through Microaeration and Direct Interspecies Electron Transfer

Corn is one of the main food products in Mexico. The elaboration of corn-derived products generates wastewater with a high organic load (nejayote). Anaerobic digestion is an indicated treatment for wastewater with high organic loads. The results of this study show that the application of microaeration in the hydrolysis-fermentative reactor increased the percentage of volatile fatty acids (VFA) available in the medium by 62%. The addition of a conductive material, such as granulated activated carbon (GAC), promotes DIET (Direct interspecies electrons transfer) in the methanogenic UASB reactor increasing the methane yield by 55%. Likewise, a great diversity of exoelectrogenic bacteria, with the ability to donate electrons DIET mechanisms, were developed in the GAC biofilm, though interestingly, Peptoclostridium and Clostridium (17.3% and 12.75%, respectively) were detected with a great abundance in the GAC biofilm. Peptoclostridium has not been previously reported as a participant in DIET process.

Research on the Development of Technologies for the Production of Granulated Activated Carbons Using Various Binders

Activated carbons (ACs) are processed carbon-rich materials with a highly developed inner surface and significant porosity used for different media treatment in municipal and industrial plants. Activated carbon may be manufactured as powdered activated carbon (PAC), gritty activated carbon (in a form of raw angels grains) or granulated activated carbon (GAC). The production of the GAC is based on carbonaceous raw materials and various types of binders. The carbon mass is mixed with the binder and formed in cylindrical granules. The binder’s recognition is in a scientific literature side-topic and still needs wider examination. For many years GAC production have been concentrated on the possibility of using sodium carboxymethylcellulose (SCMC). Therefore, the aim of the research was to develop a new binder, in the available technology of granulated activated carbon production. Such binders were tested such as: tall oil (TO), sugar beet molasses (SBM), sodium carboxymethylcellulose (SCMC), SCMC using a verified technological process and SCMC with the addition of gas tar (GT). The conducted research shows that all the quality requirements were met by activated carbons with SBM as a binder. Additionally they showed very high adsorption properties. The manufacturing process was shorter in comparison to other tested binders and more efficient.

Activated Carbon and Ozone to Reduce Simazine in Water

In this study, the reduction of the pesticide simazine at an initial concentration of 0.7 mg L−1 in water has been investigated using two different technologies: adsorption with powdered and granulated activated carbon, advanced oxidation processes with ozone and finally, the combination of both technologies. The results obtained for a carbon dose of 16 mg L−1 show that powdered activated carbon, with contact times of 60 min, obtained 81% of reduction and in 24 h 92%, while granulated activated carbon at 60 min obtained a reduction of 2%, rising to 34% after 24 h of contact time. Therefore, powdered activated carbon achieves better reductions compared to granulated; when ozone was applied at a dose of 19.7 mg L−1, with a reaction time of 18 min, a reduction of 93% was obtained, achieving a better reduction in less time than with adsorption treatments; however, during oxidation, by-products of simazine were produced. In the combined treatments, with the same doses of carbon and ozone mentioned above, the treatment that starts with ozone followed by activated carbon powder is recommended due to the adsorption in the last phase reaching a 90% reduction of the simazine and its by-products in 38 min of time.