Innovative Remediation Technologies Research Articles

ENHANCEMENT OF DECONTAMINATION OF PETROLEUM HYDROCARBONS IN CRUDE OIL POLLUTED SOIL BY USING CYCLODEXTRINS

Soil contaminated by total petroleum hydrocarbons is a well-recognized worldwide problem because of its strong persistence in the environment and its potentially toxic effects on human beings, animals and microorganisms. During the past three decades, the research and development of remediation technology for petroleum hydrocarbons-contaminated soil have been systematically studied such as the physical, chemical and bioremediation technologies. To address the associated environmental concerns, innovative remediation technologies are urgently needed. Cyclodextrins are nonhazardous and environmentally acceptable organic substances that have been shown to be biodegradable in soil and water after their introduction into an environmental system. The decontamination technique based in cyclodextrin extraction has been developed to eliminate petroleum hydrocarbons. Cyclodextrins have successfully been used in soil cleaning technologies as solubiliser–carrier molecules. These molecules can transfer continuously the insoluble contaminants from the soil surface to the aqueous phase by complex formation. In the aqueous phase the microorganisms can degrade the contaminants much easier partly because these molecules become available for the microbial cells, partly because the entrapment of contaminants by cyclodextrins reduces their toxicity.

Experimental upscaling analyses for a surfactant-enhanced in-situ chemical oxidation (S-ISCO) remediation design

Surfactant-enhanced in-situ chemical oxidation (S-ISCO) is an emerging innovative remediation technology for the treatment of dense non-aqueous phase liquids (DNAPLs). S-ISCO combines the solubilization of contaminants by means of surfactants with the chemical oxidation by an oxidizing agent, thus, potentially increasing the efficiency of the state-of-the-art ISCO technique. Scientific investigations are needed to enable the technology transfer for potential field applications based on the development of a remediation design under well-defined boundary conditions.For this purpose, experimental upscaling analyses were performed using the special infrastructure of the research facility for subsurface remediation (VEGAS). Batch tests showed that oxidation of the selected surfactant E-Mulse 3® (EM3) by activated persulfate (Na-PS) reduced the solubilization of the model contaminants 1,4-DCB, naphthalene, and PCE. As a consequence, the processes of contaminant solubilization and degradation were temporally and spatially separated in the developed remediation design.A proof of concept was provided by performing an S-ISCO medium-scale experiment (100 cm length, 70 cm height, 12.5 cm width), with 1,2-DCB as model DNAPL contaminant to be treated. A groundwater circulation well (GCW) was used to inject a 60 g/L Na-PS solution and to effectively mix the reagents. Sampling of the experiment's outflow and the soil material after treatment showed that neither rebound effects nor residual mass loadings on the soil material could be detected after termination of the S-ISCO treatment.To further evaluate the S-ISCO remediation design under field-like conditions, a large-scale S-ISCO experiment was conducted (6 m length, 3 m height, 1 m width), allowing for an extensive sampling campaign to monitor relevant processes. An efficient contaminant removal from the former source zone could be reached by surfactant solubilization, decreasing contaminant levels from initially over 2000 mg/L 1,2-DCB to final concentrations below 5 mg/L 1,2-DCB. The heterogeneously distributed contaminant degradation, implemented by a three-filter GCW, was attributed to density-induced migration processes that impeded an optimal reaction zone. A density-dependent numerical transport could qualitatively match the observations. By comparing different simulation scenarios, an adapted operation of the GCW was established that provides for a more efficient distribution of the density-influenced oxidant injection.

An antibiotic-destructase-activated Fenton-like catalyst for synergistic removal of tetracycline residues from aquatic environment

Environmental tetracycline (TC) residues are deemed as persistent contamination that threats to public health, underlining the necessity for innovative remediation technologies. Herein, TET(X), a TC destructase we identified previously, was found to produce H2O2 during degrading TC. Therefore, a Cu-based metal − organic framework (Cu-MOF) was incorporated with TET(X) to catalyze the Fenton-like reaction in response to TET(X)-produced H2O2, which eminently promoted non-enzymatic breakdown of TC. The designed composite (TET(X)-MOF) was functionally characterized to produce reactive radicals in presence of TC and be able to eradicate 50 ppm TC rapidly in a synergistic manner. The response surface method identified environmental pH as critical factor to TET(X)-MOF efficiency, suggesting that enzymatic activity of TET(X) controlled the degradation catalysis. To verify the in situ efficiency, the TET(X)-MOF was utilized to remove the TC from various environmental matrices including pond water, livestock sewage, urine and pharmaceutic effluent. High efficiency of the composite was observed as 47.9 %-100 % TC was eliminated in matrices within 3 h. Moreover, the degradation pathways of TC were proposed according to the intermediates. Eventually, the in vivo toxicity assessment indicated that the TET(X)-MOF enjoys desirable biosafety without further introduction of hazardous substance. Overall, this is the first study reporting the Fenton-like catalyst activated by and synergistically collaborated with antibiotic destructase for antibiotic decontamination. Such composite, as concept-of-principle, is of great potential to eradicate TC residues and opens up novel perspectives to develop strategies for environmental remediation.

A data-driven modeling approach for the sustainable remediation of persistent arsenic (As) groundwater contamination in a fractured rock aquifer through a groundwater recirculation well (IEG-GCW®)

Persistent arsenic (As) pollution sources from anthropogenic activities pose a serious threat to groundwater quality. This work aims to illustrate the application of an innovative remediation technology to remove As from a heavily contaminated fractured aquifer at a historically polluted industrial site. Groundwater circulation well (GCW) technology was tested to significantly increase and accelerate the mobilization and removal of As in the source area. The GCW extracts and re-injects groundwater at different depths of a vertical circulation well. By pumping out and reinjecting in different screen sections of the well, the resulting vertical hydraulic gradients create recirculation cells and affect and mobilize trapped contaminants that cannot be influenced by traditional pumping systems. The first 45-m deep IEG-GCW® system was installed in 2020, equipped with 4 screen sections at different depths and with an above-ground As removal system by oxidation and filtration on Macrolite (Enki). A geomodeling approach supports both remediation and multi-source data interpretation. The first months of operation demonstrate the hydraulic effectiveness of the IEG-GCW® system in the fractured rock aquifer and the ability to significantly enhance As removal compared to conventional pumping wells currently feeding a centralized treatment system. The recirculation flow rate amounts to about 2 m3/h. Water pumped and treated by the GCW system is reintroduced with As concentrations reduced by an average of 20%–60%. During the pilot test, the recirculating system removed 23 kg As whilst the entire central pump-and-treat (P&T) system removed 129 kg, although it treated 100 times more water volume. The P&T plant removed 259 mg As per m3 of pumped and treated groundwater while the GCW removed 4814 mg As per m3 of the treated groundwater. The results offer the opportunity for a more environmentally sustainable remediation approach by actively attacking the contamination source rather than containing the plume.

Analytical solution for soil flushing using PVD system with rectangular pattern

Soil flushing using prefabricated vertical drains (PVDs) is an innovative subsurface remediation technology for contaminated fine-grained soils. An analytical solution is presented to investigate the performance of a PVD-enhanced system arranged in a rectangular pattern for soil remediation. The analytical solution is derived based on a simplified equivalent model in which PVDs are substituted by drain walls. The results of the analytical solution are shown to be roughly consistent with those obtained from the finite-element method. Using the proposed solution, the remediation efficiency for a rectangular layout is demonstrated to be higher than that for a parallel layout. Furthermore, the effects of distance between injection and extraction PVD, injection rate, distribution coefficient, and dispersivity are investigated. Results indicate that a square pattern is the optimal layout of PVDs compared to other rectangular patterns. Increasing the injection rate of individual PVDs is an effective way to improve the remediation efficiency. The increase of distribution coefficient of contaminant leads to a significant increase in the remediation time, and the increase of longitudinal and transverse dispersivity results in a more uniform spatial distribution of contaminant concentration during the flushing process.

Recent Advances in Functional Materials for Wastewater Treatment: From Materials to Technological Innovations

The growing concerns about climate changes and environmental pollution have galvanized considerable research efforts in recent years to develop effective and innovative remediation technologies for contaminated soils and water caused by industrial and domestic activities. In this context, the establishment of effective treatment methods for wastewater has been critically important and urgent, since water pollution can take place on a very large scale (e.g., oceanic oil spills) and have massive impacts on ecosystems and human lives. Functional materials play a central role in the advancement of these technologies due to their highly tunable properties and functions. This article focuses on reviewing the recent progress in the application of various functional materials for wastewater treatment. Our literature survey is first concentrated on new modification methods and outcomes for a range of functional materials which have been actively investigated in recent years, including biofilm carriers, sand filters, biomass, biopolymers, and functional inorganic materials. Apart from the development of modified functional materials, our literature survey also covers the technological applications of superhydrophilic/superhydrophobic meshes, hybrid membranes, and reusable sponges in oil–water separation. These devices have gained significantly enhanced performance by using new functional materials as the key components (e.g., coating materials), and are therefore highly useful for treatment of oily wastewater, such as contaminated water collected from an oil spill site or oil–water emulsions resulting from industrial pollution. Based on our state-of-the-art literature review, future directions in the development and application of functional materials for wastewater treatment are suggested.

Remediation of emerging contaminated sites due to uncontrolled e-waste recycling

• Uncontrolled e-waste recycling produces multiple toxic pollutants. • Highly essential to prohibit illegal imports, and centralize up-to-standard recycling. • Small and efficient gas treatment plants are recommended before air emission. • Low-cost pollutant barriers and ex-situ water treatment are encouraged. • Soil washing with biodegradable agent and microbe-assisted vegetation are suggested. The use of primitive techniques in recycling electronic waste (e-waste) has led to severe soil pollution in recent decades, posing great threats to environmental and human health. It is urgently needed to remediate e-waste-contaminated sites effectively. This is especially true for the new e-waste-receiving countries/regions, after China has banned import of e-waste since 2016. The major aim of this article is to provide a comprehensive review of the policy, management, and remediation techniques (of contaminated sites) related to e-waste recycling, based on the information gained in two mega e-waste recycling sites in China (i.e., Guiyu town and Taizhou city). The article focuses on the remediation techniques developed to decontaminate soil/sediment/water contaminated by mixtures of toxic metals and persistent organic pollutants. Recommended innovative remediation technologies include: 1) integrating the techniques of spray tower, electronic precipitation, and photocatalysis significantly reduces health risk (e.g., VOC: ∼39%; bromomethane: ∼46%) due to the gas emitted by e-waste recycling; 2) enhanced ex-situ soil washing (using biodegradable vegetable oil) with pollutant removal efficiencies of 30–97%, depending on types of agents and pollutants; 3) enhanced phytoremediation using suitable plants, microbes, and/or soil amendments. Hyperaccumulators can extract metals, e.g., cadmium up to 14.8 kg/km 2 . Proper vegetation further extracts, stabilizes, and degrades pollutants and restores soil functions and health. Approximately 25–90% of the residual organic pollutants can be degraded depending on types of pollutants and plant species. Since the primary principle of remediation is universal, it is hoped that remediation techniques are applicable to emerging e-waste sites in other countries/regions.

Ecological and Health Risks Assessment of Potentially Toxic Metals and Metalloids Contaminants: A Case Study of Agricultural Soils in Qatar.

In recent years, Qatar has witnessed exponential growth in the human population, urbanization, and increased anthropogenic activities, including agriculture. Potentially toxic environmental contaminants, including metals and metalloids, are commonly found in emerging economies. At high concentrations, elements such as As, Cr, and Ni can be hazardous and may lead to various health problems in humans, including cancer. The current study measured As, Cd, Cr, Cu, Ni, Pb, V, and Zn concentrations in agricultural soils. Pollution levels and potential negative impacts on human and environmental health were determined using the United States Environmental Protection Agency (USEPA) standard methodologies. According to the study’s findings, the studied element concentrations descended in the following order: Zn > Cr > V > Ni > As > Cu > Pb > Cd. Of these, As (27.6 mg/kg), Cr (85.7 mg/kg), Ni (61.9 mg/kg), and Zn (92.3 mg/kg) concentrations were higher than average world background levels. Each of these elements also had an enrichment factor (EF > 1), indicating their anthropogenic origin. The combined pollution load index (PLI > 1) and geo-accumulation index (Igeo) range values of −0.2–2.5 further indicated that the soil was up to 58% polluted. However, the ecological risk factor (Er ≤ 40.6) and potential ecological risk index (PERI = 79.6) suggested low ecological risk. A human health risk evaluation showed that only As, with a hazard index (HI) of 1.3, posed a noncarcinogenic risk to infants. Additionally, As, Cr, and Ni, with total carcinogenic risk (TCR) values of 1.18 × 10−4 and 2.06 × 10−4 for adults and children, respectively, proved carcinogenic to both age groups. The elements’ carcinogenic risk (CR) potential descended in the following order: Ni > As > Cr. Additionally, for both adults and children, oral ingestion is the most likely exposure pathway. Our findings support the need for closer monitoring of potentially toxic metals and metalloids levels in cultivated soils and farm produce in Qatar. Reducing the elements’ bioavailability in soil and developing innovative remediation technologies is needed to limit potential risks to human health. Further studies on As, Cr, and Ni gastrointestinal bioaccessibilities are needed to fully understand the effects after long-term exposure and the cancer-causing potential of these elements over a lifetime.

Application of chemical reagents as innovative remediation technologies for groundwater impacted by petroleum hydrocarbons in Italy

Innovative technologies with injection of chemical compounds were applied in order to remediate 28 contaminated sites with petroleum hydrocarbon impacted groundwater spread in the Italian territory. The used reagents can be classified into three main technologies: enhanced bioremediation products with oxygen released, In Situ Chemical Oxidation (ISCO) and surfactants. The analysis of these technologies allowed to better understand how to conduct the design, the execution and monitoring phases of the remediation. For the design phase soil and groundwater samples were collected from each site in order to identify the magnitude of the contamination and different calculation methods were tested to quantify the reagents needed for the remediation. For the execution phase the following application methods were performed and analysed: reagents injection into monitoring wells, injection by direct push into the soil, injection into devoted injection wells, application of the reagents into filter socks, application of the reagents into a dig. Pros and cons of each method were so identified. During the monitoring phase the remediation efficacy was evaluated using, not only chemical concentration of contaminants, but also chemicalphysical parameters spatial distribution as a valid support. In the wide range of remediation technologies, the use of chemical reagents has been progressively more appreciated by the designers and by public authorities and is now extensively applied because it is in some cases more effective, cheaper or quicker. These technologies, in fact, proved to be a solid and sustainable alternative to plant technologies, and they were very effective also in fine aquifers. For 62% of the analysed sites, chemical injections led to a reduction of the contamination within 1 year from the application.

Pilot scale applications of microwave heating for soil remediation

Thermal remediation technologies are very efficient for the removal of lipophilic organic contaminants from solid waste or soil. Compared to conventional heating method that is energy consuming due to the low thermal conductivity of contaminated material, microwaves bring several benefits for thermal solids treatment. There are three different approaches for the application of microwave heating for remediation - 1) contaminated material heating in a kiln, 2) the in-situ heating of contaminated surfaces and 3) the in-situ heating of subsurface soil environment. We developed and tested the pilot units for these applications including efficient off-gas treatment system. The pilot remediation tests were performed using 6 kW 2.45 GHz industrial microwave generators for the treatment of materials from several contaminated sites. During the tests, we measured detailed spatial temperature and contaminants mass distribution in the tested material. The achieved results confirmed promising data from laboratory tests and the high efficiencies of different contaminants removal were achieved at mild temperatures and with low energy consumption. Moreover, we gained important empirical knowledge about these innovative remediation technologies that has allowed to determine practical limitations for further scale-up and field applications or to validate future numerical models.

Cathodic microbial community adaptation to the removal of chlorinated herbicide in soil microbial fuel cells

The microbial fuel cell (MFC) that uses a solid electrode as the inexhaustible electron acceptor is an innovative remediation technology that simultaneously generates bioelectricity. Chlorinated pollutants are better metabolized by reductive dechlorination in proximity to the cathode. Here, the removal efficiency of the herbicide metolachlor (ML) increased by 262 and 176% in soil MFCs that were spiked with 10 (C10) and 20mg/kg (C20) of ML, respectively, relative to the non-electrode controls. The bioelectricity output of the C10 and C20 increased by over two- and eightfold, respectively, compared to that of the non-ML control, with maximum current densities of 49.6 ± 2.5 (C10) and 78.9 ± 0.6mA/m2 (C20). Based on correlations between ML concentrations and species abundances in the MFCs, it was inferred that Azohydromonas sp., Sphingomonas sp., and Pontibacter sp. play a major role in ML removal around the cathode, with peak removal efficiencies of 56±1% (C10) and 58±1% (C20). Moreover, Clostridium sp., Geobacter sp., Bacillus sp., Romboutsia sp., and Terrisporobacter sp. may be electricigens or closely related microbes due to the significant positive correlation between the bioelectricity generation levels and their abundances around the anode. This study suggests that a directional adaptation of the microbial community has taken place to increase both the removal of chlorinated herbicides around the cathode and the generation of bioelectricity around the anode in bioelectrochemical remediation systems.

Influence of selected cyclodextrins in sorption-desorption of chlorpyrifos, chlorothalonil, diazinon, and their main degradation products on different soils.

Cyclodextrins (CDs) can improve the apparent solubility and bioavailability of a variety of organic compounds through the formation of inclusion complexes; accordingly, they are suitable for application in innovative remediation technologies of contaminated soils. However, the different interactions in the tertiary system CD/contaminant/soil matrix can affect the bioavailability of the inclusion complex through the possible sorption of CD and CD complex in the soil matrix, as well as with the potential of the sorbed CD to form the complex, concurrent with the desorption processes. This work focuses in changes produced by three different CDs in soil sorption-desorption processes of chlorpyrifos (CPF), diazinon (DZN), and chlorothalonil (CTL), and their major degradation products, 3,5,6-trichloro-2-pyridinol (TCP), 2-isopropyl-6-methyl-4-pyrimidinol, and hydroxy-chlorothalonil (OH-CTL). Cyclodextrins used were β-cyclodextrin (β-CD), methyl-β-cyclodextrin (Mβ-CD), and 2-hydroxypropyl-β-cyclodextrin(HPβ-CD). The studied soils belong to the orders Andisol, Ultisol, and Mollisol with different organic matter contents, mineral composition, and pH. The apparent sorption constants were significantly lower for the three pesticides in the presence of all CDs. The highest displacement of sorption equilibria was produced by the influence of Mβ-CD, with the most pronounced effect for CPF, a pesticide strongly sorbed on soils. The same was obtained for TCP and OH-CTL, highlighting the need to assess the risk of generating higher levels of groundwater contamination with polar metabolites if degradation rates are not controlled. The highest desorption efficiency was obtained for the systems CPF-β-CD, DZN-Mβ-CD, and CTL-Mβ-CD. Since the degree of adsorption of the complex is relevant to obtain an increase in the bioavailability of the contaminant, a distribution coefficient for the complexed pesticide in all CD-soil-pesticide system was estimated by using the apparent sorption coefficients, the stability constant for each CD-pesticide complex, and the distribution coefficients of free pesticide.

Studies on application of Fe based binary oxide nanoparticles for treatment of lead (Pb2+) contaminated water- A batch study

Water & wastewater remediation using nanoparticles has received increasing interests in recent years. In the present study, a binary metal oxide of Fe-Cu was synthesized & used for the removal of Pb2+ from aqueous solution. Batch technique was performed to investigate the effects of variation of initial Pb2+ concentration, adsorbent dose and pH of solution on the removal efficiency of Pb2+. The synthesized nanostructured material presented an outstanding ability to remove Pb2+ due to high surface area, low particle size and high inherent activity The extent of Pb2+ removal increased with increasing dosage of nanoparticles (0.5 g/L – 2.5 g/L) whereas decreased with initial Pb2+ concentration (1 mg/L – 20 mg/L) and pH of (4-8). The results obtained from this research provides compelling evidence that the Fe-Cu binary oxide nanoparticles may be used for in situ reductive ability of Pb2+ contaminated groundwater which may lead to an innovative remediation technology proving to be cost effective and less environmental concerning. The prepared material was characterized using powder XRD & SEM. It showed that the Fe-Cu binary oxides were formed in single phase. SEM micrograph showed aggregates with many nano-sized particles.

泥水式シールド一体型の自然由来砒素汚染土壌浄化技術の実証と性能評価

本研究では，新しく開発した泥水式シールド一体型の自然由来砒素汚染土壌浄化技術の実証実験を実施し，(1)迅速で安定した浄化処理が可能であり，(2)浄化土が砒素溶出量基準(0.01mg/L)に確実に適合し，(3)濃縮汚染土が約10%に減容化されること等の実証を目的に行なった。各浄化プロセスの土量と砒素全含有量の収支を検討した上で，新浄化技術による浄化効果と減容化効果の評価を行なった。砒素溶出量基準の4～6倍の汚染土壌に本技術を適用したところ，常に基準を満足する浄化土が得られた。砒素の全含有量と溶出量が高い微細粒分を取り除くことが，効率的な浄化処理に大きく寄与していると考えられた。浄化土の回収割合が約90%，濃縮汚染土の発生割合が約10%であり，非常に高い減容化が可能であることが認められた。浄化土のコーン指数は679～1,128 kN/m2であり，建設資材として利用できることが確認された。

Modeling the Diffusion of Contaminated Site Remediation Technologies

The present study developed epidemic models to predict the diffusion of remediation technology. Hypotheses were derived from the models and then tested using data collected from a questionnaire survey (n = 223) and a qualitative interview (n = 28) mainly conducted in the USA, UK, and China, as well as data from the US Superfund program. Hypothesis testing results indicate that: (1) tacit knowledge in innovative remedial technologies leads to logistic rather than exponential growth in their adoption, and (2) social-economic and regulatory factors affect the adoption of remediation technologies. For specific remedial technologies adopted in the US Superfund program, it was found that in-situ bioremediation (ISB) has a higher maximum adoption rate than in-situ chemical treatment (ISC), likely due to lower cost and higher social acceptance associated with ISB. The diffusion of ISC was found to be more rapid than that of ISB due to a greater degree of tacit knowledge associated with ISB.

Remediation of polycyclic aromatic hydrocarbon and metal-contaminated soil by successive methyl-β-cyclodextrin-enhanced soil washing–microbial augmentation: a laboratory evaluation

Polycyclic aromatic hydrocarbon (PAH) and metal-polluted sites caused by abandoned coking plants are receiving wide attention. To address the associated environmental concerns, innovative remediation technologies are urgently needed. This study was initiated to investigate the feasibility of a cleanup strategy that employed an initial phase, using methyl-β-cyclodextrin (MCD) solution to enhance ex situ soil washing for extracting PAHs and metals simultaneously, followed by the addition of PAH-degrading bacteria (Paracoccus sp. strain HPD-2) and supplemental nutrients to treat the residual soil-bound PAHs. Elevated temperature (50 °C) in combination with ultrasonication (35 kHz, 30 min) at 100 g MCD L(-1) was effective in extracting PAHs and metals to assist soil washing; 93 % of total PAHs, 72 % of Cd, 78 % of Ni, 93 % of Zn, 84 % of Cr, and 68 % of Pb were removed from soil after three successive washing cycles. Treating the residual soil-bound PAHs for 20 weeks led to maximum biodegradation rates of 34, 45, 36, and 32 % of the remaining total PAHs, 3-ring PAHs, 4-ring PAHs, and 5(+6)-ring PAHs after washing procedure, respectively. Based on BIOLOG Ecoplate assay, the combined treatment at least partially restored microbiological functions in the contaminated soil. The ex situ cleanup strategy through MCD-enhanced soil washing followed by microbial augmentation can be effective in remediating PAH and metal-contaminated soil.

Innovative Technologies for Sustainable Environmental Remediation in Poor and Middle Income Countries

Innovative Technologies for Sustainable Environmental Remediation in Poor and Middle Income Countries

Remediation technologies using cyclodextrins: an overview

Nowadays, the human activity and the modern way of life are responsible for the increase of the environmental pollution. Industrial processes generate a variety of molecules that may pollute air, water, and soils due to negative impacts for ecosystems and humans. The development of innovative remediation technologies has thus emerged as a significant environmental priority. Within this scope, supramolecular chemistry, which is a recent discipline, could provide solutions. In particular, cyclodextrins (CDs) are a family of cyclic oligosaccharides having a low-polarity cavity in which organic compounds of appropriate shape and size can form inclusion complexes. This unique property makes them suitable for application in environmental protection. Here, we review the use of cyclodextrins and cyclodextrin derivatives in remediation technologies. Accordingly, the present review shows the advantages of using CDs in soil, groundwater, wastewater, and atmosphere remediation. Resulting processes are highly versatile, since the complexing ability of CD is applicable to a wide range of pollutants. They may also been referred to green processes, according to the CD innocuity. Moreover, as inclusion phenomena correspond to reversible equilibriums, a major trend in the CD environmental application field is to develop methods, which combine supramolecular chemistry and irreversible processes, as advanced oxidation or biodegradation. Such processes might lead to a complete remediation of pollutants and eventually to the CD recycling.

Biogenic metals in advanced water treatment

Microorganisms can change the oxidation state of metals and concomitantly deposit metal oxides and zerovalent metals on or into their cells. The microbial mechanisms involved in these processes have been extensively studied in natural environments, and researchers have recently gained interest in the applications of microbe-metal interactions in biotechnology. Because of their specific characteristics, such as high specific surface areas and high catalytic reactivity, biogenic metals offer promising perspectives for the sorption and (bio)degradation of contaminants. In this review, the precipitation of biogenic manganese and iron species and the microbial reduction of precious metals, such as palladium, platinum, silver and gold, are discussed with specific attention to the application of these biogenic metals in innovative remediation technologies in advanced water treatment.

In-well air sparging efficiency in remediating the aquifer of a petroleum refinery site

Air sparging represents an innovative groundwater remediation technology, which has been proved to be capable of restoring aquifers that have been polluted by volatile and (or) biodegradable contaminants, such as petroleum hydrocarbons. This paper presents the design, the installation, and the pulsed operation of an in-well air sparging system at the site of a Greek petroleum refinery. The geographical position, the hydrologeoly, and the contamination features of the chosen study area develop special conditions that, along with the fact that the existing refinery is still active, greatly determine the applicability and the effectiveness of the specific technology. The area that was used for the application of the technology covered almost 600 m2 and included five air injection wells and four additional monitoring wells. The pulsed operation of the installed system lasted about 5 months and the results of frequent groundwater sampling and analysis indicate an important decline in total petroleum hydrocarbons (TPH) and benzene–toluene–ethylbenzene–xylene (BTEX) concentrations (up to 99%). However, prior to any attempt to expand the application of air sparging within the facilities of the refinery, special attention should be given to the eccentricities of the site and the ability of the technology to confront more persistent contaminants, such as methyl tertiary-butyl ether (MTBE).