Sustainable Remediation Method Research Articles

Harnessing the power of nonthermal Plasma: A breakthrough in stabilizing Thallium contaminants in soil and unveiling the mechanism

Thallium (Tl) is a highly toxic element and can accumulate in human body through food, water, or air and cause damage to multiple organs. In this study, the nonthermal plasma (NTP) was employed to irradiate the potassium dihydrogen phosphate (KH2PO4) and sodium diethyldithiocarbamate trihydrate (SDDC) to solve the issues brought by their poor stability and insufficient chelation capabilities in soils to intensify their performance on immobilizing monovalent Tl contaminants in soils. Both an orthogonal design (OD) and a central composite design (CCD) were adopted to arrange the multi-parametrical modification and stabilization experiments. The leaching toxicities ranging from 5.11 to 52.37 µg/L of Tl+ ions were obtained in the OD experiments. The changes in both NTP time and the molar ratios of KH2PO4 to SDDC had a significant effect on the activation procedure. The leaching concentration ranging from 0.37 to 7.34 µg/L was achieved in the CCD stabilization experiments. NTP activation and the rearrangement of the stabilization conditions both were beneficial to the transformation of physicochemical states of Tl pollutants in soils, which proved the existence of chemical immobilization brought by the irradiated stabilizers (NTP-PK-SDDCs) to the Tl contaminants. The stabilization process was targeted between only Tl contaminants and NTP-PK-SDDCs in soils. The NTP irradiation enhanced the physicochemical characteristics of stabilizers, further intensifying the immobilization of Tl species in the soils. The enhancement mechanism was attributed to the free radicals-induced doping, oxidation, and polycondensation and the bombards of electrons, which strengthened the electrostation and chemisorption of NTP-PK-SDDCs towards Tl ions. The potential impact of this study includes the development of more effective and sustainable remediation methods for Tl-contaminated soils, contributing to environmental protection and human health.

Engineered Bacillus subtilis Biofilm@Biochar living materials for in-situ sensing and bioremediation of heavy metal ions pollution

The simultaneous sensing and remediation of multiple heavy metal ions in wastewater or soil with microorganisms is currently a significant challenge. In this study, the microorganism Bacillus subtilis was used as a chassis organism to construct two genetic circuits for sensing and adsorbing heavy-metal ions. The engineered biosensor can sense three heavy metal ions (0.1–75 μM of Pb2+ and Cu2+, 0.01–3.5 μM of Hg2+) in situ real-time with high sensitivity. The engineered B. subtilis TasA-metallothionein (TasA-MT) biofilm can specifically adsorb metal ions from the environment, exhibiting remarkable removal efficiencies of 99.5% for Pb2+, 99.9% for Hg2+and 99.5% for Cu2+ in water. Furthermore, this engineered strain (as a biosensor and absorber of Pb2+, Cu2+, and Hg2+) was incubated with biochar to form a hybrid biofilm@biochar (BBC) material that could be applied in the bioremediation of heavy metal ions. The results showed that BBC material not only significantly reduced exchangeable Pb2+ in the soil but also reduced Pb2+ accumulation in maize plants. In addition, it enhanced maize growth and biomass. In conclusion, this study examined the potential applications of biosensors and hybrid living materials constructed using sensing and adsorption circuits in B. subtilis, providing rapid and cost-effective tools for sensing and remediating multiple heavy metal ions (Pb2+, Hg2+, and Cu2+).

A comprehensive assessment to offer optimized remediation method for mercury contamination in Musa Bay by using hybrid Fuzzy AHP-VIKOR approach.

Musa Bay, the largest wetland in Iran and one of the most important Hg-polluted media, plays a significant role in the ecosystem of the area and supports many forms of life. Mercury pollution has detrimental effects on the human body and at high levels leads to the loss of microorganisms in marine ecosystems. Hence, a comprehensive assessment for selecting an effective and sustainable remediation method is crucial to restoring the ecosystem promptly. The determination of a proper and practical treatment method not only is a case-based approach, but could be challenging due to its multi-criteria decision-making nature. Considering preferred crucial factors involved in the effectiveness of remedial actions, in this study a questionnaire is designed to assess the opinion of environmental experts, stakeholders, and some occupants of the area on remedial actions based on the importance weights of criteria. Subsequently, practical remediation and management strategies ranked by hybrid FVIKOR as a multi-criteria decision making (MCDM) method. Ranking results show that dredging and stabilization could offer a promising solution for the remediation of the case study. The results of the study demonstrate that the development of MCDM methods along with effective criteria and considering the analysis of the questionnaires, could offer the best remediation strategy for a specific contaminated site.

EFFECTS OF VERMICAST TEA ON THE REMEDIATION OF SPENT ENGINE OIL CONTAMINATED SOIL

The need to maintain the rising numbers of both serviceable and degenerating automobiles in Nigeria has led to the springing up of vehicle workshops in approved and unapproved locations, where mechanics discharge spent engine oil indiscriminately into the soil and water environments. It is therefore desirable to explore potentially affordable and sustainable remediation methods. This study examined the efficacy of vermicast tea for the remediation of spent engine oil contaminated soil. Spent engine oil contaminated soil was collected from an automobile workshop, and mixed with different concentrations (20%, 50%, and 100%) of vermicast tea. The total petroleum hydrocarbon (TPH), moisture content, organic matter content, pH, and cation exchange capacity (CEC) in the contaminated soils were determined on day one, day 21, and day 42, using standard procedures. It was found that the TPH concentrations reduced in both vermicast tea treated and untreated soils, but percentage reductions were higher in contaminated soils treated with vermicast tea (63.65% – 74.74%) than in soil without vermicast tea (59.85%). The moisture content, organic matter content, pH, and cation exchange capacity of the spent engine oil contaminated soil were impacted due to the presence of vermicast tea. Moreover, remediation was observed to be significantly higher (p<0.05) at day 42 of exposure to vermicast tea, than at day 21. These results imply that vermicast tea can hasten natural remediation of soil contaminated with spent engine oil. It is recommended that future studies on the use of vermicast tea to remediate spent engine oil-contaminated soil for a...

The microbiome of a brownfield highly polluted with mercury and arsenic

Abandoned brownfields represent a challenge for their recovery. To apply sustainable remediation technologies, such as bioremediation or phytoremediation, indigenous microorganisms are essential agents since they are adapted to the ecology of the soil. Better understanding of microbial communities inhabiting those soils, identification of microorganisms that drive detoxification process and recognising their needs and interactions will significantly improve the outcome of the remediation. With this in mind we have carried out a detailed metagenomic analysis to explore the taxonomic and functional diversity of the prokaryotic and eukaryotic microbial communities in soils, several mineralogically distinct types of pyrometallurgic waste, and groundwater sediments of a former mercury mining and metallurgy site which harbour very high levels of arsenic and mercury pollution. Prokaryotic and eukaryotic communities were identified, which turned out to be more diverse in the surrounding contaminated soils compared to the pyrometallurgic waste. The highest diversity loss was observed in two environments most contaminated with mercury and arsenic (stupp, a solid mercury condenser residue and arsenic-rich soot from arsenic condensers). Interestingly, microbial communities in the stupp were dominated by an overwhelming majority of archaea of the phylum Crenarchaeota, while Ascomycota and Basidiomycota fungi comprised the fungal communities of both stump and soot, results that show the impressive ability of these previously unreported microorganisms to colonize these extreme brownfield environments. Functional predictions for mercury and arsenic resistance/detoxification genes show their increase in environments with higher levels of pollution. Our work establishes the bases to design sustainable remediation methods and, equally important, to study in depth the genetic and functional mechanisms that enable the subsistence of microbial populations in these extremely selective environments.

Asymmetrical alternating current electrochemically-mediated washing method for sustainable remediation of Cr(VI)-contaminated soil

The demands for genuine remediation of heavy metal contaminated soil have triggered extensive studies in the soil washing method. However, numerous soil washing methods show poor sustainability for target soil, due to the tremendous cost, hidden secondary pollution and severe soil deterioration. Here, an asymmetrical alternating current electrochemically-mediated remediation platform (ACRP) is developed by fabricating an amidoxime-functionalized electrode (Ami-electrode). The real soil contaminated with 1200 mg/kg Cr(VI) is remediated efficiently to less than safety level (30 mg/kg), meanwhile no exorbitant soil nutrient loss is observed and no secondary pollution occurs. Furthermore, the consumption of washing effluents for the ACRP method is 24 times lower than the traditional washing method. Ami-electrode with asymmetrical alternating current promote the electrocatalytic efficiency by inhibiting the Coulomb repulsion between Cr(VI) species and cathode. With the aid of Ami-electrode and positive bias, Cr(VI) species in effluents are adsorbed on chelating site. By subsequent negative bias, Cr element is reduced and recycled in the less hazardous form of amorphous Cr(III) hydroxide, and effluents are regenerate concurrently in a cyclic system. Durability experiment and cost calculation verify the exceptional sustainability and feasibility for remediation practices. This work provides a sustainable remediation method for Cr(VI)-contaminated soil, and then paves the way to develop electrochemically soil remediation platform for practical applications.

The role of nitrogen metabolism on polyethylene biodegradation

Polyethylene (PE) is the most widely used plastic and its accumulation on natural environments has reached alarming levels causing severe damage to wildlife and human health. Despite the significance of this global issue, little is known about specific metabolic mechanisms behind PE biodegradation—a promising and sustainable remediation method. Herein, we describe a novel role of nitrogen metabolism in the fragmentation and oxidation of PE mediated by biological production of NOx in three PE-degrading strains of Comamonas, Delftia, and Stenotrophomonas. Resultant nitrated PE fragments are assimilated and then metabolized by these bacteria in a process assisted by nitronate monooxygenases and nitroreductases to support microbial growth. Due to the conservation of nitrogen metabolism genes, we anticipate that this oxidative mechanism is potentially shared by other nitrifier and denitrifier microbes.

Degradation of 4-nonylphenol in marine sediments using calcium peroxide activated by water hyacinth (Eichhornia crassipes)-derived biochar

The contamination of marine sediments by 4-nonylphenol (4-NP) has become a global environmental problem, therefore there are necessaries searching appropriate and sustainable remediation methods for in-situ applications. Herein, water hyacinth [(WH) (Eichhornia crassipes)]-derived metal-free biochar (WHBC) prepared at 300–900 °C was used to promote the calcium peroxide (CP)-mediated remediation of 4-NP-contaminaed sediments. At [CP] = 4.37 × 10−4 M, [WHBC] = 1.5 g L−1, and pH = 6.0, the degradation of 4-NP was 77% in 12 h following the pseudo-first order rate law with rate constant (kobs) of 4.2 × 10−2 h−1. The efficient 4-NP degradation performance and reaction mechanisms of the WHBC/CP system was ascribed to the synergy between the reactive species (HO• and 1O2) at the WHBC surface on which there were abundant electron-rich carbonyl groups and defects/vacancies in the catalyst structure provides active sites, and the ability of the graphitized carbon framework to act as a medium for electron shuttling. According to microbial community analysis based on amplicon sequence variants, bacteria of the genus Solirubrobacter (Actinobacteria phylum) were dominant in WHBC/CP-treated sediments and were responsible for the biodegradation of 4-NP. The results showed great promise and novelty of the hydroxyl radical–driven carbon advanced oxidation processes (HR-CAOPs) that relies on the value-added utilization of water hyacinth for contaminated sediment remediation in achieving circular bioeconomy.

Critical Review of Bioadsorption on Modified Cellulose and Removal of Divalent Heavy Metals (Cd, Pb, and Cu)

Heavy metal contamination in soil and water has become a serious threat to all forms of life. Finding a sustainable remediation method is the prime concern of researchers worldwide. In this quest, cellulose has emerged as a biocompatible, biodegradable, renewable, tunable, and cost-effective bioadsorbent for heavy metal removal from polluted water. Cellulose is rich in hydroxyl groups which can be chemically modified to enhance the reactivity, binding sites, and mechanical strength. Cellulose in nano size, i.e., nanofibers and nanocrystals, offer myriad opportunities to improve the aspect ratio, surface area, pore size, and hydrophilicity for effective adsorption. In this review, chemical and physical modifications in cellulose (functional group transformations, nanocellulose, nanocomposites, hydrogels, aerogels, beads, and membranes) with respect to adsorption of divalent heavy metal ions, in particular, Pb2+, Cu2+, and Cd2+, have been extensively discussed. This review also examines the effect of pH, concentration, temperature, and contact time on the adsorption process. Different mechanisms for heavy metal removal such as ion exchange, electrostatic interactions, complexation, chelation, precipitation, and reduction have been discussed. Theoretical insights into the mechanisms of adsorbent–adsorbate binding are critically examined in the context of modified cellulose. The authors, in the concluding section, summarize potential research directions toward developing sustainable biosorbents.

Biological-Based Produced Water Treatment Using Microalgae: Challenges and Efficiency

Produced water (PW) is the most significant waste stream generated in the oil and gas industries. The generated PW has the potential to be a useful water source rather than waste. While a variety of technologies can be used for the treatment of PW for reuse, biological-based technologies are an effective and sustainable remediation method. Specifically, microalgae, which are a cost-effective and sustainable process that use nutrients to eliminate organic pollutants from PW during the bioremediation process. In these treatment processes, microalgae grow in PW free of charge, eliminate pollutants, and generate clean water that can be recycled and reused. This helps to reduce CO2 levels in the atmosphere while simultaneously producing biofuels, other useful chemicals, and added-value products. As such, this review focuses on PW generation in the oil and gas industry, PW characteristics, and examines the available technologies that can be used for PW remediation, with specific attention to algal-based technologies. In addition, the various aspects of algae growth and cultivation in PW, the effect of growth conditions, water quality parameters, and the corresponding treatment performance are presented. Lastly, this review emphasizes the bioremediation of PW using algae and highlights how to harvest algae that can be processed to generate biofuels for added-value products as a sustainable approach.

Biochar applications enhance the phytoextraction potential of Salix smithiana [Willd.] (willow) in heavily contaminated soil: potential for a sustainable remediation method?

Biochar applications enhance the phytoextraction potential of Salix smithiana [Willd.] (willow) in heavily contaminated soil: potential for a sustainable remediation method?

Heavy Metal Pollution of Environment by Mine Tailings and the Potential Reclamation Techniques: A Review

Environmental pollution through heavy metal has alarmingly been increased due to industrial and economic development worldwide. Since the industrial revolution started throughout the world, mining activities are being developed, generating huge amount of metal-rich hazardous wastes like tailings and thereby posing potential threat to terrestrial and aquatic ecosystems. The small tailings particles can easily be spread out of the tailings ponds to the surrounding environment because of erosion driven by rain water and strong wind. Subsequently, heavy metals of tailings particles enter into the food chain in different ways and result in serious health issues in humans and animals. Therefore, ecological restoration of mine wastelands is of paramount concern. Different methods for the remediation of mine sites have been developed so far, most of which are expensive and difficult to implement. Countries having severe heavy metal pollution issues are spending huge money every year for the management purpose of these pollution sources and still scientists are doing research to establish eco-friendly, cost-effective, easily-applicable and sustainable remediation strategies for the metal-rich mine tailing sites. This review describes the way of heavy metal contamination of environment by mine tailings, negative effects of heavy metals, research development regarding remediation methods as well as suggests some ideas for the future research direction. Keywords: Mine tailings, heavy metal contamination, sustainable remediation method, phytoremediation, amendments DOI: 10.7176/JBAH/10-16-05 Publication date: August 31 st 2020

Nanotechnology in soil remediation - applications vs. implications.

Engineered nanomaterials (ENMs) and nanotechnology have shown great potential in addressing complex problems and creating innovative approaches in soil remediation due to their unique features of high reactivity, selectivity and versatility. Meanwhile, valid concerns exist with regard to their implications towards the terrestrial environment and the ecosystem. This review summarizes: (i) the applications and the corresponding mechanisms of various types of ENMs for soil remediation; (ii) the environmental behavior of ENMs in soils and their interactions with the soil content; (iii) the environmental implications of ENMs during remedial applications. The overall objective is to promote responsible innovations so as to take optimal advantage of ENMs and nanotechnology while minimizing their adverse effects to the ecological system. It is critical to establish sustainable remediation methods that ensure a healthy and safe environment without bringing additional risk.

Proposal for an optimized method for sustainable remediation evaluation and application: implementation of a multi-criteria process.

As sustainable remediation methods do not yet have a consolidated approach, a detailed assessment of the level of satisfaction for sustainability prospects is necessary. So, this study aims to evaluate the sustainability level of sustainable remediation methods according to the visions of decision makers in this field, in order to propose an optimized method that best represents its approach. We considered eight methods applied to sustainable remediation and nine decision criteria for evaluation. The analytical hierarchy process (AHP) of multi-criteria decision analysis (MCDA) was applied to judge and weigh the criteria by stakeholders. These weights were used to calculate the degrees of sustainability for all the methods, to classify these within a ranking, and to optimize the one that obtained the best performance. The results indicated that when the criteria were weighted, the criterion (C7), protection of human health and the environment in general, obtained the best placement, and the degree of sustainability achieved by each method indicates that ITRC (Interstate Technology and Regulatory Council) had the best performance. Finally, the proposal method resulted in an explicit approach of all the considered criteria. This article presents a new approach compared with those already applied in this context and provides more robust resources to examine to what extent the methods integrate the premises of sustainable remediation. Graphical Abstract .

Multi-criteria decision analysis of optimal planting for enhancing phytoremediation of trace heavy metals in mining sites under interval residual contaminant concentrations

As one of the most cost-effective and sustainable methods for contaminants' removal, sequestration and/or detoxification, phytoremediation has already captured comprehensive attention worldwide. Nevertheless, the accurate effects of various spatial pattern in enhancing phytoremediation efficiency is not yet clear, especially for the polluted mining areas. This study designed nine planting patterns (monocropping, double intercropping and triple intercropping) of three indigenous plant species (Setaria viridis (L.), Echinochloa crus-galli (L.) and Phragmites australis (Cav.) Trin. ex Steud.) to further explore the effects of plants spatial pattern on phytoremediation efficiency. Considering the uncertainties of the residual contaminants' concentration (RCC) caused by soil anisotropy, permeability and land types, the interval transformation was introduced into the plant uptake model to simulate the remediation efficiency. Then multi-criteria decision analysis (MCDA) were applied to optimal the planting patterns, with the help of criteria of (a) the amount of heavy metal absorption; (b) the concentration of residual contaminant in soil; (c) root tolerance of heavy metals; (d) the total investment cost. Results showed that (1) the highest concentrations of Zn, Cd, and Pb of the polluted area were 7320.02, 14.30, 1650.51 mg kg−1 (2) During the 180 days simulation, the highest RMSE of residue trace metals in soil are 3.02(Zn), 2.67(Pb), 2.89(Cd), respectively. (3) The result of IMCDA shows that the planting patterns of Setaria viridis, Echinochloa crus-galli and Phragmites australis in alternative a9 (269 mg kg−1 year−1) had the highest absorption rate of heavy metals compared with a7 (235 mg kg−1 year−1) and a2 (240 mg kg−1 year−1). After 20 years of remediation, the simulated RCC in a9 is far below the national standard, and the root toxicity is 0.12 (EC ≤ EC20). In general, the optimal alternative derived from interval residual contaminant concentration can effectively express the dynamic of contaminant distribution and then can be effectively employed to evaluate the sustainable remediation methods.

Efficacy and limitations of low-cost adsorbents for in-situ stabilisation of contaminated marine sediment

Recycling waste materials as adsorbents for stabilising contaminated marine sediment is a low-cost and sustainable remediation method. The objective of this research was to evaluate the efficacy of organic (lignite and green waste compost) and inorganic wastes (acid mine drainage sludge (AMDS) and coal fly ash (CFA)) on metal stabilisation and assess the leachability of minerals from the adsorbents. The kinetic results illustrated that Zn (0.21 mg L−1) and Cu (0.16 mg L−1) quickly released from the sediment within 30 min. The continuous column leaching tests showed that the addition of carbonaceous lignite effectively reduced leaching of Zn (4.5–7.0 mg L−1) and Pb (0.05–0.06 mg L−1) after 100 pore volumes, although the stabilisation capacity was lower than that of activated carbon. In comparison, two inorganic industrial by-products (AMDS and CFA) outcompeted the stabilisation performance of organic materials, which reduced the long-term leaching concentrations of Cu and Zn to below 1 mg L−1. The AMDS even provided comparable efficiency to the commercial zero-valent iron due to its abundant sorption sites and alkaline earth metals for contaminant adsorption and precipitation. However, the addition of waste adsorbents resulted in elevated leaching of Mn, Fe, and Al from the lignite- and AMDS-amended sediment, which may pose toxic risks to benthic organisms. the proposed waste adsorbents present a low-cost and low-carbon treatment for in-situ contaminated sediment remediation.

Low-thermal remediation of mercury-contaminated soil and cultivation of treated soil

In this study, low-thermal technology was used to treat the mercury contaminated farmland soil from a chemical plant in Guizhou Province, China. A series of field planting experiments were also aimed at determining the content of total and methyl-Hg in crop plants after thermal treatment. The results showed that the mercury concentration in soils was reduced about 70% from 255.74mg/kg to 80.63mg/kg when treated at 350°C for 30min in engineering-scale experiments, and the treated soil retained most of its original soil. Organic-bound and residual mercury in treated soil were reduced by 64.1 and 56.4% by means of a sequential extraction procedure, respectively. The total and methyl-mercury concentrations in crops decreased significantly, and the degree of soil mercury accumulation to crop roots has been reduced significantly. The total Hg concentrations in potato and corn were lower than the mercury tolerance limits for food in China, and the Hg concentration of radish was close to the limit. The technology provides a more sustainable remediation method for treating mercury-contaminated farmland soil in future engineering applications.

Pesticide Pollution in Agricultural Soils and Sustainable Remediation Methods: a Review

An increasing number of pesticides have been used in agriculture for protecting the crops from pests, weeds, and diseases but as much as 80 to 90% of applied pesticides hit non-target vegetation and stay as pesticide residue in the environment which is potentially a grave risk to the agricultural ecosystem. This review gives an overview of the pollution in agricultural soils by pesticides, and the remediation techniques for pesticide-contaminated soils. Currently, the remediation techniques involve physical, chemical, and biological remediation as well as combined ways for the removal of contaminants. The microbial functions in rhizosphere including gene analysis tools are fields in remediation of pesticide-contaminated soil which has generated a lot of interest lately. However, most of those studies were done in greenhouses; more research work should be done in the field conditions for proper evaluation of the efficiency of the proposed techniques. Long-term monitoring and evaluation of in situ remediation techniques should also be done in order to assess their long-term sustainability and practical applications in the field.

A novel method for remediation of nickel containing wastewater at neutral conditions

Heavy metals contained in wastewater are generally removed by adding antalkaline to increase the pH, and Ni is commonly precipitated as Ni-hydroxides at pH 10. However, a more sustainable remediation method of treatment at neutral conditions would be attractive due to the high cost of chemical reagents and inefficient treatment at present. Based on natural attenuation, the method of adding Al ions has been used in wastewater treatment to precipitate layered double hydroxides (LDH). Here, we investigated the use of Al ion addition in the Ni containing wastewater treatment, experimentally and thermodynamically. By co-precipitation experiments adding Al ions to Ni-containing water, Ni was selectively incorporated into the structure of LDH, and the removal efficiency of Ni was close to 100% even in pH 7 and 8 samples (lower pH than conventional methods) with initial Ni concentrations of 200–10,000mg/L. Geochemical modeling results replicate the experimental results well when the Al/Ni ratio of LDH is assumed to be 0.33. This model makes it possible to estimate the amount of Al ions and additive agents necessary for use in treatment of wastewater containing different Ni concentrations.

In Situ-mobilization of Arsenic in Groundwater – an Innovative Remediation Approach?

In order to evaluate an inefficient pump & treat remediation at a contaminated site in Germany, processes of arsenic release into groundwater were studied. Groundwater and aquifer material sampling indicated elevated mobility of arsenic and a differentiated spatial distribution of As(V) and As(III). An artificial increase of arsenic mobilization in addition to the ongoing pump & treat remediation was supposed to be a suitable and sustainable remediation method for the contaminated site. Typically, arsenic mobility is increased under iron-reducing conditions, yet a number of water ingredients trigger arsenic mobility, e.g phosphate. The affinity of phosphate to sorb onto mineral phases leads to a competitive surface-complexation of phosphate and arsenic. In column tests, the release of arsenic from the contaminated aquifer material was significantly enhanced by the addition of phosphate. Under oxic and anoxic redox conditions the geochemical processes led to elevated release of mobile arsenic fractions up to a total of 50–60% and almost 100% in a period of 90 days, respectively. Eventually, the amendment of phosphate is able to enhance the efficiency of a pump & treat remediation and is currently investigated on field scale on-site.