Article

A Review of Approaches and Techniques Used in Aquatic Contaminated Sediments: Metal Removal and Stabilization by Chemical and Biotechnological Processes

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

The contamination of aquatic sediments with metals is a widespread environmental problem. Coastal aquatic ecosystems with low hydrodynamics need to be periodically dredged in order to maintain the navigation depth and facilitate sailing; consequently large volumes of contaminated sediments need to be managed. Conventional remediation strategies include in-place sediment remediation strategies (e.g. in situ-capping) and relocation actions; in particular, landfill disposal and dumping at sea are still widely applied. Both this options are becoming unsustainable, due to problems associated with contaminant transport pathways, the uncertainties about long-term stability under various environmental conditions, the limited space capacity, costs and environmental compatibility. Alternative approaches have received increased attention; treatment and reuse of contaminated sediments is politically encouraged, but its application is still very limited. Because of the potential human health and environmental impacts of contaminated sediment, different chemical treatments are conventionally applied for contaminated sediments before reuse in other environmental settings. Environmentally friendly techniques developed for soils and other environmental matrices have been investigated for applications with sediments. Biotechnological approaches are gaining increasing prominence in this field and they are often considered as a promising strategy for the eventual treatment of contaminated sediments. In this paper an overview of the main treatment strategies potentially available for sediment contaminated with metals is given, together with a brief overview of the issue associated with the problem of the sediment management.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Currently, to detoxify chromate polluted environment, various conventional physicochemical methods could be utilized such as soil washing, land filling, physicochemical extraction etc., however, all the procedures demand high chemical inputs, making them quite expensive and cumbersome with drawbacks of sludge production (Jeyasingh and Philip, 2005). In this regard, bioremediation offers an inexpensive, innovative and eco-friendly approach to detoxify metal contaminated environment with the help of indigenous microorganisms (Akcil et al., 2015). Native microbiota in the heavy metal polluted wastewater have established the strategies for their survival to fight off the metal generated hazards by various methods such as metal adsorption, absorption, oxidation, reduction and methylation (Mangaiyarkarasi and Geetharamani, 2014;Liu et al., 2020). ...
... The bacterial strains which have been endowed with the ability to reduce chromate are regarded as chromium-reducing bacteria (CRB), which could be easily found in the effluents discharged by the industries, especially from textile, tanneries, and chrome electroplating manufacturing as well as the soil polluted with these effluents (Elahi and Rehman, 2019a). The chromate resistance strains belongs to Staphylococcus, Microbacterium, Ochrobactrum, Bacillus and Brevibacterium have already been reported previously in Cr 6+ reduction and bioremediation scenario (Zahoor and Rehman, 2009;Mangaiyarkarasi and Geetharamani, 2014;Akcil et al., 2015;Li et al., 2020;Li et al., 2021). ...
Article
Full-text available
The chromate resistant Gram-positive Bacillus cereus strain b-525k was isolated from tannery effluents, demonstrating optimal propagation at 37°C and pH 8. The minimum inhibitory concentration (MIC) test showed that B. cereus b-525k can tolerate up to 32 mM Cr⁶⁺, and also exhibit the ability to resist other toxic metal ions including Pb²⁺ (23 mM), As³⁺ (21 mM), Zn²⁺ (17 mM), Cd²⁺ (5 mM), Cu²⁺ (2 mM), and Ni²⁺ (3 mM) with the resistance order as Cr ⁶⁺ > Pb²⁺ > As³⁺ >Zn²⁺ >Cd²⁺ >Ni²⁺ >Cu²⁺. B. cereus b-525k showed maximum biosorption efficiency (q) of 51 mM Cr⁶⁺/g after 6 days. Chromate stress elicited pronounced production of antioxidant enzymes such as catalase (CAT) 191%, glutathione transferase (GST) 192%, superoxide dismutase (SOD) 161%, peroxidase (POX) 199%, and ascorbate peroxidase (APOX) (154%). Within B. cereus b-525k, the influence of Cr⁶⁺ stress (2 mM) did stimulate rise in levels of GSH (907%) and non-protein thiols (541%) was measured as compared to the control (without any Cr⁶⁺ stress) which markedly nullifies Cr⁶⁺ generated oxidative stress. The pilot scale experiments utilizing original tannery effluent showed that B. cereus b-525k could remove 99% Cr⁶⁺ in 6 days, thus, it could be a potential candidate to reclaim the chromate contaminated sites.
... Practical restoration method(s). Removal of sediment through various methods of careful dredging and/or coverage of damaged soft bottoms with a clean substrate or active carbon can lower the environmental effects from toxic compounds in polluted sediments, e.g. in harbours, marinas or in industrial recipients (Akcil et al. 2015, Rostmark et al. 2015. Similar methods could possibly be used for removal of anoxic or nutrient rich sediments for example in shallow bays in order to combat macroalgal mats (Hulth & Sundbäck 2009). ...
... Wasserman et al. (2013) estimated costs around 22 euro per dredged m 3 of polluted sediment and 14 euro per dumped m 3 (Rio de Janeiro, Brazil). Stocks & Grassle 2001, Bolam et al. 2006, Norkko et al. 2006, Hulth & Sundbäck 2009, Apler & Nyberg 2011, Cooper et al. 2013, Nyberg et al. 2013, Apler et al. 2014, Wasserman et al. 2016, Akcil et al. 2015, Rostmark et al. 2015. ...
Technical Report
Full-text available
This publication has been produced as part of the project “Actions to evaluate and identify effective measures to reach GES in the Baltic Sea marine region (HELCOM ACTION)”. Running from January 2019 to December 2020, HELCOM ACTION is a Helsinki Commission (HELCOM) coordinated project that is co-funded by the European Union. The project is designed to contribute to the update of the HELCOM Baltic Sea Action Plan by 2021 and can also be used by HELCOM Contracting Parties that are also EU Member States in updating and implementing their MSFD Programme of Measures. Information and views expressed in this publication are the authors’ own and might vary from those of the Helsinki Commission or its members. This publication is a deliverable of the HELCOM ACTION project’s work package WP2 - Impacts on the seabed: evaluating restoration measures in coastal areas and impacts of spatial regulation of offshore fisheries, including effects on benthic communities and costs of measures.
... Biological-based processes (e.g. biosorption, bioaccumulation) are therefore promising for the treatment of contaminated sediments [72]. The S/S popularity is based on the rapid, versatile (in situ or ex situ), broad range of contaminants immobilized and low-cost achievement of treatment objectives. ...
... However, stabilization of contaminants without matrix solidification could also sometimes prove sustainable, especially when coupled to a controlled release of reactants/microbes for enhanced remediation in the long term [73] or to green/alternative binders for diverting hazardous wastes from disposal following an life-cycle assessment [74]. In this sense, the literature shows a slow but steady evolution towards environmentally sustainable solutions: from high impact (thermal treatment and cementification) to low impact (chemical and biological) processes [72]. Moreover, in some countries (Denmark, South Korea) the S/S technology is prohibited because removal of contaminants from soils is required over their stabilization [73]. ...
... The main ex-situ approaches for the treatment of contaminated sediments (e.g., after dredging) include chemical-physical, thermal, and biological treatments [14][15][16][17][18][19][20][21]. The chemical-physical treatments can be used to (i) promote the solubilization of metals from the sediments by aqueous solutions containing chemical or chelating agents and by electrochemical processes; (ii) reduce the mobility of contaminants through complexation with stabilizing agents (like lime or cement, [8,22]). ...
... The chemical-physical treatments can be used to (i) promote the solubilization of metals from the sediments by aqueous solutions containing chemical or chelating agents and by electrochemical processes; (ii) reduce the mobility of contaminants through complexation with stabilizing agents (like lime or cement, [8,22]). Thermal treatments can be used either to desorb HM from the sediment or to induce their immobilization into the sedimentary matrix [19,23]. Nevertheless, all these approaches are limited mainly due to high economic costs, low specificity, and the generation of large amounts of toxic wastes [24][25][26][27]. ...
Article
Full-text available
The contamination of coastal marine sediments with heavy metals (HMs) is a widespread phenomenon that requires effective remediation actions. Bioremediation based on the use of bacteria is an economically and environmentally sustainable effective strategy for reducing HM contamination and/or toxicity in marine sediments. However, information on the efficiency of marine-derived fungi for HM decontamination of marine sediments is still largely lacking, despite evidence of the performance of terrestrial fungal strains on other contaminated matrixes (e.g., soils, freshwater sediments, industrial wastes). Here, we carried out for the first time an array of parallel laboratory experiments by using different combinations of chemical and microbial amendments (including acidophilic autotrophic and heterotrophic bacteria, as well as filamentous marine fungi) for the bioremediation of highly HM-contaminated sediments of the Portman Bay (NW Mediterranean Sea), an area largely affected by long-term historical discharges of mine tailings. Our results indicate that the bioleaching performance of metals from the sediment is based on the addition of fungi (Aspergillus niger and Trichoderma sp.), either alone or in combination with autotrophic bacteria, was higher when compared to other treatments. In particular, fungal addition allowed obtaining bioleaching yields for As eight times higher than those by chemical treatments and double compared with the addition of bacteria alone. Moreover, in our study, the fungal addition was the only treatment allowing effective bioleaching of otherwise not mobile fractions of Zn and Cd, thus overtaking bacterial treatments. We found that the lower the sediment pH reached by the experimental conditions, as in the case of fungal addition, the higher the solubilization yield of metals, suggesting that the specific metabolic features of A. niger and Trichoderma sp. enable lowering sediment pH and enhance HM bioleaching. Overall, our findings indicate that fungi can be more effective than acidophilic autotrophic and heterotrophic bacteria in HM bioleaching, and as such, their use can represent a promising and efficient strategy for the bioremediation of marine sediments highly contaminated with heavy metals.
... Non-toxic sediments can be directly used in land for soil filling, construction purposes, coastal nourishment and as an amendment in agriculture, horticulture, and forestry as long as they comply with the pollutant-specific regulations or are classified in the appropriate category (as explained in Section 4). In these cases, they could be also disposed directly in landfills or oceans, which are common and simple techniques but present considerably high environmental impacts (Akcil et al., 2015;Barjoveanu et al., 2018;Bhairappanavar et al., 2018). In case of landfilling of toxic sediments, apart from the huge land requirements, dredged sediments can be only disposed in facilities that present appropriate soil characteristics and rigorous dumpsite management to assure their safe deposit, avoiding toxic emissions (Mehdizadeh et al., 2021;Pal and Hogland, 2022;Pellenz et al., 2020;Wang et al., 2019). ...
... However, there is still a long way to make this process feasible at large scale since metal extraction is complex and dependant on multiple factors such as the level of pollution in the sediments, the metal speciation and the properties of the sediment matrix. Moreover, metal extraction processes usually present high risks of environmental pollution (Akcil et al., 2015;Norén et al., 2020). ...
Article
Dredging is an essential technique to maintain proper water depths in ports and bays. Many dredged sediments are considered as toxic waste due to their significant amounts of metals and other pollutants. In consequence, they need to be treated to reduce this toxicity and avoid pollutant resuspensions. Physical operations and chemical, thermal and biological processes have been conventionally used to this aim, but the traditional linear sediment approach is often unsustainable and economically and environmentally demanding. Considering the increasing people’s awareness in environmental issues, more efficient dredged sediment management schemes are required. Some authors are making significant efforts to improve circularity in sediment management processes by taking advantage of the mineral composition of sediments to obtain products for the building and road construction sectors, therefore decreasing the need of raw materials while reducing the amounts of sediments wasted to landfills. However, information related to the characteristics of these products, their mechanical behaviour and their functionality is still scarce, being sediment-based by-products developed mainly at low Technological Readiness Level (TRL), showing low global impact in the market. To implement circular economy in the dredged sediment sector, some technical and socio-political barriers must be still overcome. To this aim, further research and technological applications must be developed, with the support of decision makers and stakeholders. This review aims at giving an overview of the circular trends applied to toxic dredged sediment management, pointing at current opportunities, barriers and constraints that hinder its wide development.
... The ability of microorganisms to adsorb heavy metals or change the forms of their presence in the environment attracts wide attention of researchers in connection with the possibility of biotechnological use of heavy metal resistant bacteria or archaea for wastewater treatment, bioremediation of contaminated environments, as well as in biogeotechnology of metals (Volesky 1994;Gadd 2005;White and Gadd 2000). Bioremediation using microorganisms is receiving much attention due to their good performance and employed in order to transform toxic heavy metals into a less harmful state (Ndeddy Aka and Babalola 2016; Akcil et al. 2015) or using microbial enzymes to clean-up polluted environment (Okoduwa et al. 2017). The technique is environmentally friendly and cost effective in the revitalization of the environment (Turpeinen et al. 2004;Ma et al. 2016). ...
Chapter
Metal-rich natural and artificial habitats are extreme environments for the development and evolution of unique microbial communities, which have adapted to the toxic levels of the metals. Diverse bacterial groups have developed abilities to deal with the toxic metals by bioaccumulation of the metal ions inside the cell actively or passively, extracellular precipitation, efflux of heavy metals outside to the microbial cell surface, biotransformation of toxic metals to less toxic forms, and metal adsorption on the cell wall. Metalophilic microbes are found in all bacterial and archaeal groups studied, but mostly appear among aerobic and facultative anaerobic chemoheterotrophic and chemolithoautotrophic microorganisms of the Bacillus, Pseudomonas, Staphylococcus, Actinobacteria, Cuprividus, Acidobacterium, Acidithiobacillus, Thiobacillus, Ferroplasma, and Sulfolobus genera. The phenomenon of microbial heavy metal resistance has fundamental importance and is particularly relevant in microbial ecology, especially in connection with the roles of microbes in biogeochemical cycling of heavy metals and in the bioremediation of metal-contaminated environments. The heavy metal resistance mechanisms and different applications of metal resistant/metalophilic bacteria and archaea have been expounded deeply in this chapter.
... Conventional physical or chemical remediation strategies of the tailing soils are uneconomical or may generate large volumes of chemical waste (Ayangbenro and Babalola 2017). Bioremediation strategy using microorganisms as the "cleaners" seems to be an efficient alternative for elimination of the heavy metals from the polluted environments, and has been attracting extensive interest over the years (Mani and Kumar 2014;Akcil et al. 2015;Dixit et al. 2015;Katiyar et al. 2020). It has been shown that microbes can usually perform the remediation process through three different pathways, i.e., biosorption and bioaccumulation, siderophore formation and biosurfactants production (Mosa et al. 2016;Ayangbenro and Babalola 2017). ...
Article
Full-text available
We evaluated the variations of bacterial communities in six heavy metal contaminated soils sampled from Yanzi Bian (YZB) and Shanping Cun (SPC) tailings located in northwestern China. Statistical analysis showed that both the heavy metals and soil chemical properties could affect the structure and diversity of the bacterial communities in the tailing soils. Cd, Cu, Zn, Cr, Pb, pH, SOM (soil organic matters), TP (total phosphorus) and TN (total nitrogen) were the main driving factors of the bacterial community variations. As a consequence, the relative abundances of certain bacterial phyla including Proteobacteria, Chloroflexi, Firmicutes, Nitrospirota and Bacteroidota were significantly increased in the tailing soils. Further, we found that the abundance increasement of these phyla were mainly contributed by certain species, such as s__unclassified_g__Thiobacillus (Proteobacteria), s__unclassified_g__Sulfobacillus (Firmicutes) and Leptospirillum ferriphilum (Nitrospirota). Thus, these species were considered to be strongly heavy metal tolerant. Together, our findings will provide a useful insight for further bioremediations of these contaminated areas.
... 44 Such poor management resulted in economic loss due to the free discharge of valuable materials, as well as damage to the environment and human health. 45,46 Various national and international initiatives have been implemented to tackle this low recovery problem such as the 2006 EU battery directive 47 and the proposed new EU regulation which concerns batteries and waste batteries. 48 The key challenge, however, is the lack of recycling infrastructure around the world, there are only a few full-scale recycling facilities (Table 1). ...
Article
Full-text available
There is a growing demand for lithium-ion batteries (LIBs) for electric transportation and to support the application of renewable energies by auxiliary energy storage systems. This surge in demand requires...
... The THg levels of the whole sediment across various depths and treatments were not significantly different in AC treatments compared to control treatments. These results were expected, as sorbent amendment in sediments basically serves to increase immobilization and not for removing contaminants (e. g., less THg available in pore water) (Akcil et al., 2015). Furthermore, MeHg concentration was higher in unamended sediment with increasing depth, and the amended sediment MeHg content was significantly reduced as compared to control sediment. ...
Article
Activated carbon (AC) amendment is considered as one of the alternatives for managing and remediating mercury (Hg) contaminated sediments because of its high sorptive capacity and potential to immobilize the contaminant. For this study, the underlying mechanisms that control the reduction of Hg bioavailability in AC-amended estuarine sediments were investigated in box microcosm set-ups with 28-day Asian clam bioassay experiments. The application of diffusive gradients in thin film technique (DGT) revealed that the total mercury and methylmercury levels in sediment pore water decreased by 60%–75% in 1%–3% AC-amended sediments. This decrease subsequently led to a linear reduction in the Hg body burden in Asian clams, even at 1% sorbent mixing. These observations implied that AC amendment reduced the net flux of Hg into the pore water and overlying water, resulting in reduced Hg bioaccumulation in benthic organisms. The addition of AC to sediment also led to reduced dissolved organic carbon and several biogeochemical indicators (HS⁻, Mn, and Fe) in the pore water. Furthermore, the 16 S rRNA gene amplicon sequencing analysis revealed noticeable alterations in the microbial communities after AC amendment. The predominant phylum was Firmicutes in control sediment, Bacteroidetes in 1% AC-amended sediment, and Proteobacteria in both 2% and 3% AC-amended sediment samples. The genera-level analysis showed that the relative abundance of the Hg-methylators decreased as the level of AC amendment increased. These observations suggested that AC amendment decreased Hg bioavailability not only by physicochemical sorption but also by changing geochemical species and shifting the microbial community composition.
... Contamination of heavy metals in agricultural land increased rapidly due to mining activity, urbanization, industrialization, and chemical fertilizer (Zhang et al. 2013). Heavy metals, such as Cu, Zn, Pb, Mn, and Cd are the most common pollutants (Akcil et al. 2015;Mohanty et al. 2017;Bal et al. 2019) and all of these metals are often found in soil as individual ions or compounds (Bannon et al. 2009). Heavy metal contamination of soil causes serious risk to human being and animal through the food chain (Kołtowski et al. 2016). ...
Article
Soil amendment with biochar is evaluated globally as a means to improve soil fertility, restoration of the ecological functions for anthropogenically polluted soils and also is a potential candidate to mitigate climate change. Application of biochar, a carbon-rich material developed from the combustion of biomass under no or limited oxygen supply has been found to ameliorate some of the negative effects of soil. Biochar modifications can lead to an increase in the water holding capacity as well as pH modification may also be used as a soil amendment. There are various other physical, chemical, and biological properties of biochar that can impact soils. However, the effects of biochar on soil biota have received much less attention than its effects on soil chemical properties. This review highlights essentially the various methods of preparation of biochar from waste biomasses and its usage as a potential soil amendment agent with a special emphasis on the effect of biochar on soil microbiology. A well-accepted mechanism of the effect of biochar on soil microbe environment still needs more focus. Therefore, the current review will further help in understanding the feasibility, safety, and effectiveness of biochar utilization for improving the fertility of the soil.
... Metal soil contamination is recognized as one of the biggest environmental concerns worldwide and constitutes a permanent threat to ecosystems, agricultural sustainability, and human health [1]. The agricultural sector suffers horribly from the increase over time of metal pollution, such as lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), and Arsenic (As) causing a significant decrease in plant growth and crop yield [2]. Heavy metals are also used in various terrestrial chemical fungicides and fertilizers, wastewater irrigation, and sewage sludge causing heavy metal contamination of water resources and agricultural soils [2,3]. ...
Article
Full-text available
Background: Soil pollution by heavy metals increases the bioavailability of metals like hexavalent chromium (Cr (VI)), subsequently limiting plant growth and reducing the efficiency of phytoremediation. Plant growth-promoting rhizobacteria (PGPR) have substantial potential to enhance plant growth as well as plant tolerance to metal stress. The aim of this research was to investigate Cr (VI) phytoremediation enhancement by PGPR. Results: The results showed that the 27 rhizobacterial isolates studied were confirmed as Cr (VI)-resistant PGPR, by using classical biochemical tests (phosphate solubilization, nitrogen fixation, indole acetic acid, exopolysaccharides, hydrogen cyanide, siderophores, ammonia, cellulase, pectinase, and chitinase production) and showed variable levels of Cr (VI) resistance (300-600 mg/L). The best four selected Cr (VI)-resistant PGPR (NT15, NT19, NT20, and NT27) retained most of the PGP traits in the presence of 100-200 mg/L concentrations of Cr (VI). The inoculation of Medicago sativa with any of these four isolates improved the shoot and root dry weight. The NT27 isolate identified using 16S rDNA gene sequence analyses as a strain of Pseudomonas sp. was most effective in terms of plant growth promotion and stress level decrease. It increased shoot and root dry weights of M. sativa by 97.6 and 95.4%, respectively, in the presence of Cr (VI) when compared to non-inoculated control plants. It also greatly increased chlorophyll content and decreased the levels of stress markers, malondialdehyde, hydrogen peroxide, and proline. The results of the effect of Pseudomonas sp. on Cr content and bioaccumulation factor (BAF) of the shoots and roots of M. sativa plants showed the increase of plant biomass concomitantly with the increase of Cr root concentration in inoculated plants. This would lead to a higher potential of Cr (VI) phytostabilization. Conclusions: This study demonstrates that the association M. sativa-Pseudomonas sp. may be an efficient biological system for the bioremediation of Cr (VI)-contaminated soils.
... Thus, a key concern for researchers was to find a holistic remediation technique for the restoration of degraded aquatic environs, which after proper testing in laboratories, can be commercialized in the future. Although several conventional physicochemical pollutant cleanup approaches are effective but, they are not feasible for large-scale application under natural conditions (Akcil et al., 2015). In contrast to this, bioremediation has emerged as the most desirable, efficient, safe, economical, practicable, sustainable, and environment-friendly mode of degradation or transformation and immobilization of recalcitrant environmental pollutants into non-harmful or less-harmful form, primarily by means of selected microorganisms (Tegli et al., 2014;Mishra and Sarma, 2017;Varjani and Patel, 2017;. ...
... The application of biochar in the serpentine soils in small-scale pilot trials observed that they promote the immobilization of toxic heavy metals (Cr, Ni, Co, and Pb), the absorption of essential nutrients, and the reduction of phytotoxicity [179]. Some common pollutants that are also reduced, such as Cd, Pb, Zn, and Cu, coexist as compounds or divalent ions in the soil, sediments, and water [180,181]. The elimination of Cu, Cd, and Pb could be due to functional groups and the properties of the surface which promote the binding Content courtesy of Springer Nature, terms of use apply. ...
Article
Full-text available
Serpentine soils are contaminants of naturally occurring metal-rich agricultural and fallow lands due to erosion of the serpentine site with consequences and deterioration of soil, water quality, and water sources in the ecosystem. The harsh climatic conditions due to the high concentration of potential toxic elements, organic pollutants, and acidity make it difficult to cultivate and establish vegetation on serpentine or adjacent land. Recently, biochar amendments have emerged in the area of soil remediation technology with the suitability and potential to promote seed emergence, plant growth, biomass productivity, and vegetation cover on contaminated soils such as serpentine soil. By enhancing the buffering capacity of the soil through pH, soil nutrients and water holding capacity stimulate the diversity and function of microbes. In this review, we have conferred the physicochemical aspects of serpentine soil, heavy metal contaminants, and their consequences, especially in crop production and phytotoxicity. Another, the assessment of biochar preparation using various types of feedstock, their characteristics, and the application for the amendment of serpentine soils has been deliberated. The restoration of sites with a high fraction of heavy metal contaminents and organic pollutants associated with serpentine soils using biochar has been highlighted for its importance. In line with the possibility of expanding the cultivated area, future research directions have been suggested in field trials, advances in biochar production, and environmental risk assessment. In addition, the applicable mechanisms have prerequisites to accelerate the efficiency of biochar amendments.
... Increasing population, the speedy growing mine tailings and industrial waste, the disposal of metal and land application of chemical fertilizers, waste sludge, and wastewater irrigation may result in heavy metal pollution of agricultural lands and water resources [2,8,9,12,13]. Soil contamination with heavy metals like cadmium, arsenic, nickel, copper, lead, zinc, aluminum, and mercury is one in every of the world's major environmental issues, leading to major negative concerns on ecosystems, crop yield, and human health [6,17,21]. ...
Article
The aim of the study was to isolate and characterizations of heavy metal tolerate rhizobacteria from rhizosphere soil near plant growing near mining area and landfill site. A total of 91 rhizobacterial colonies isolated, 51 rhizobacteria were isolated from Zawar mines area, Udaipur, Rajasthan, India and 40 rhizobacteria were isolated from Pirana landfill site. Ahmedabad, Gujarat, India. Total Six rhizobacteria (SMHMZ2, SMHMZ4, SMHMZ46, SMHMP4, SMHMP23, and SMHMP38) showed higher tolerances against heavy Metals, which was subjected to biochemical characterization and extracellular enzyme production. Optimized growth conditions for all six isolates were at temperature 37°C and pH 7. Maximum Inhibition Concentration was performed using Nutrient enriched Media (Nutrient Agar and Luria Bertani Media) and Nutrient Deficient Media (Minimal salt media) in both solid agar plate and liquid broth condition. The rhizobacterial isolate SMHMZ4 could resist the higher concentration of Cd 2+ up to 1500 µg/ml in all three liquid broths and 1100 µg/ml, 1500 µg/ml, and 900µg/ml on NA, LB, and MSM agar plate respectively. The SMHMZ46 isolates could resist higher concentrationsofPb 2+ and Ni 2+ up to 2000 µg/ml and 5000 µg/ml, respectively in all three liquid broths and on solid agar plate Pb 2+ 1700 µg/ml, 2100 µg/ml, and 800 µg/ml on NA, LB, and MSM agar plate respectively and Ni 2+ up to 4500 µg/ml, 4500 µg/ml, and 2100 µg/ml on NA, LB, and MSM agar plate respectively. Also, Antibiotic sensitivity of rhizobacterial isolates was performed. Isolated heavy metal tolerates rhizobacteria may be advantageous for potential agents for bioremediation and in groups with phytoremediation of heavy metals in the contaminated environment.
... Similarly, sedimentation and flotation strategies have also been followed for the removal of contaminants. But the efficiency of these processes is lowered due to the high costs and production of secondary pollutants (Akcil, Erust, Ozdemiroglu, Fonti, & Beolchini, 2015). Hugar and Marol (2020) studied electrocoagulation using iron electrodes for the treatment of wastewater obtained from the paper and pulp industry. ...
Chapter
The paper and pulp industry is considered to be major energy- and assets-consuming industry, among others. Along with the production of valuable products, the effluents obtained from this industrial sector are also higher in numbers contributing directly to greenhouse gas production. The production of such contaminants has adverse effects on humans, animals, and plants (both terrestrial and aquatic). The waste products like sulfur compounds, oxides of nitrogen, chlorinated products being produced as a result of pulp manufacturing and bleaching processes are significantly harming the environment. Many steps need to be taken to minimize the hazard being caused by the paper industry-byproducts. The presented chapter covers the root causes of these harmful byproducts' production, their negative impact on the surrounding environment, and treatment approaches.
... Such situation drew the attention of scientists to innovate proper technologies for heavy metals bioremediation. Bioremediation is management biotechnology that makes use of a variety of microorganisms and hyper-accumulator plants solely or in associations for removing and/or neutralizing pollutants from soil ecosystems (Akcil et al., 2015). In contrast to "traditional" soil remediation technologies, biological methods are environmentally friendly and particularly attractive because of their low cost and relatively simple maintenance (Mirsal, 2008). ...
Article
Bioremediation technologies are environmentally friendly and cost-effective approaches for potential toxic elements (PTEs) in polluted soil ecosystems. Results indicated that Kafr-el-Sheikh soil had a risky concentrations of the studied PTEs according to permissible limits according to FAO and WHO and the index of Geoaccumulation (Igeo). In a pot experiment, four major bioremediation strategies, i.e., phytoremediation, natural attenuation, bio augmentation and bio augmentation with bio stimulation were tested. The experiment was performed using soil ecosystem exposed to pollution with PTEs for long periods, collected from Kafr-El-Sheikh Governorate. Tested bacterial strains used in bioremediation showed close proximity with Pseudomonas aeruginosa KY549647 and Enterobacter cloacae JX 885522 according to 16S rRNA gene sequence analysis and the yeast isolate showed close proximity with Saccharomyces cerevisiae KF747750 according to universal fungal ITS gene analysis. Results indicated that tested microorganisms showed signs of growth promotion that might be proved on all tested treatments accompanied by decreasing soil pH. The highest reduction was recorded under the application of rock phosphate (RP) plus Enterobacter cloacae (PH 7.4). Radish was used as a test plant. Enhancement in radish growth, represented by increase in the total fresh biomass, which was observed under application of soluble organic matter amended with mixed culture consortium (T 2) (131g). Results also showed that some treatments enhanced phytoextraction of tested potential toxic elements leading to a reduction in their total concentration in the soil under the permissible limits set by FAO and WHO, as observed in mixed culture consortium treatment (T 1) and in soluble organic matter amended with mixed culture consortium (T 2). Other protocols led to a decrease PTEs uptake by radish plant as in Saccharomyces cerevisiae KF747750 a (T 5) and Pseudomonas aeruginosa KY549647 plus a mixture of kaolinite and bentonite (T 3) and these treatments are efficient in rapid decontamination of heavily contaminated soils for safe food production. Results confirmed that used microorganisms were promissing tools for heavy metals bioremediation.
... Contamination of heavy metals in agricultural land increased rapidly due to mining activity, urbanization, industrialization, and chemical fertilizer (Zhang et al. 2013). Heavy metals, such as Cu, Zn, Pb, Mn, and Cd are the most common pollutants (Akcil et al. 2015;Mohanty et al. 2017;Bal et al. 2019) and all of these metals are often found in soil as individual ions or compounds (Bannon et al. 2009). Heavy metal contamination of soil causes serious risk to human being and animal through the food chain (Kołtowski et al. 2016). ...
... When the pH, oxygen-reduction potential, or salinity of the water body changes, heavy metals easily leach from the sediment and become soluble contaminants in soil environments (Peng et al., 2009). Relative to physicochemical treatment, heavy metal bioremediation of sediment is inexpensive and environmentally friendly (Akcil et al., 2015). ...
Article
This study used polyvinyl alcohol (PVA) as the proton exchange membrane (PEM) of sediment microbial fuel cells (SMFCs) to assess the oxygen diffusion and proton transfer performance of two types of PEMs, i.e. PVA elastomer (PVA-E) and PVA hydrogel (PVA-H). The oxygen diffusion coefficient of the PVA-E (0.42 × 10⁻⁴ cm ²/s) was 36.7% of that of the PVA-H. By reducing the amount of oxygen diffused from the cathode to the anode, a favorable water absorption rate (74.7%), 2.10–3.55 times of those obtained in previous studies, was achieved, enabling the rate of proton transfer by the PVA-E to reach 200.7 μM H+/s/m. The Cu2+ removal efficiency of the SMFCs with oxygen separation membranes was 1.21 times that of the SMFCs without oxygen separation membranes. With high external resistance, the SMFCs generated low currents under high voltage output, which was conducive to Cu2+ migration. This explains the voltage output peak (168.0 mV) under an external resistance of 1000 Ω. Furthermore, under the same external resistance, the Cu2+ removal (55.1%) was 1.14–1.38 times that of the corresponding rates achieved under external resistances of 20 and 510 Ω, respectively. X-ray diffraction revealed that electrocoagulation constituted the main mechanism of Cu2+ removal from sediment with SMFCs. Integrating PVA-E and SMFC can facilitate the fabrication of a device with high power output and potential for use in removing Cu2+ from sediment.
... Marine sediments need to be regularly removed for safe navigation (Baltic Marine Environment Protection Commission, 2015; Akcil et al., 2015). However, dredged masses of the marine sediments should be treated before the reuse. ...
Article
Full-text available
The seabed in the ports needs to be regularly cleaned from the marine sediments for safe navigation. Sediments contaminated by tributyltin (TBT) are environmentally harmful and require treatment before recycling. Treatment methods include leaching, stabilisation and solidification to remove toxic chemicals from the sediments and improve their strength for reuse in the construction works. This study evaluated the effects of adding three different binder components (cement, cement kiln dust (CKD) and slag) to treat sediment samples collected in the port of Gothenburg. The goal of this study is to assess the leaching of TBT from the dredged marine sediments contaminated by TBT. The various methods employed for the treatment of sediments include the application of varied ratios of binders. The project has been performed by the Swedish Geotechnical Institute (SGI) on behalf of the Cementa (HeidelbergCement Group) and Cowi Consulting Group, within the framework of the Arendal project. An experiment has been designed to evaluate the effects of adding CKD while reducing cement and slag for sediment treatment. Methods that have been adopted include laboratory processing of samples for leaching using different binder combinations, followed by statistical data processing and graphical plotting. The results of the experiment on leaching of TBT for all samples are tested with a varied ratio of cement, slag, CKD and water. Specimens with added binders 'cement/CKD' have demonstrated higher leaching compared to the ratio 'cement/slag/CKD' and 'cement/slag'. The 'CKD/slag' ratio has presented the best results followed by the 'cement/slag/CKD', and can be used as an effective method of s/s treatment of the sediments. The results have shown that the replacement of cement and slag by CKD is effective at TBT leaching for the treatment of toxic marine sediments contaminated by TBT.
... Several technologies including isolation, mechanical separation, phytoremediation, bioremediation, chemical leaching, chemical fixation, permeable reactive barriers (PRB), and electrokinetics (EK) have been applied for the remediation of heavy metals-contaminated soils (Akcil et al., 2015;Dhaliwal et al., 2020;Srivastava and Gupta, 2021). Among these, EK has been considered as a promising remediation technology due to its higher efficiency and reliability for treating the toxic heavy metals (Rahman et al., 2021). ...
Article
Research on electrokinetics-permeable reactive barrier (EK-PRB) remediation to date has mainly focused on homogeneous soils or soils with micro-scale heterogeneities. The potential impact of macro-scale physical heterogeneities, such as stratified layers or lenses, on EK-PRB remediation has not received much attention. This study investigates the effect of a low permeability stratum on EK-PRB remediation of hexavalent chromium (Cr(VI)). Sandbox experiments were conducted to treat Cr(VI)-contaminated kaolinite/sand media, consisting of vertically-layered high permeability (HPZ) and low permeability zones (LPZ), where distance between LPZ and anode (DLA) was 3, 9, or 15 cm. Parameters including current, moisture content (MC), pH, and removal of Cr(VI) were evaluated. With 72 hours of EK-PRB treatment, tests with larger DLA (15 cm) had greater Cr(VI) migration from contaminated area to modified-zeolite PRB. Cr(VI), Cr(III), and Cr(Total) removal and energy utilization efficiency followed the trend as: DLA-15>DLA-9>DLA-3. MC generally decreased from anode towards cathode and pH was alkaline in all the zones for DLA-3 and DLA-15. In DLA-9 (LPZ in the middle), MC increased and pH was alkaline in HPZs near cathode whereas HPZs near anode were very dry (MC <1%) and acidic (pH <5.5). Our results show that the location of LPZ relative to electrode locations has a significant influence on Cr(VI) removal efficiency and macro-scale physical heterogeneity is an important factor to be considered during EK-PRB remediation.
... Together, these properties make heavy metals a major threat to global food security. The major sources that add metals to agronomic soils include: (i) surface runoff from mine tailings (Rzymski et al., 2017), (ii) application of agrochemicals (Gonçalves Jr et al., 2014), (iii) industrial discharge (Al Moharbi et al., 2020), (iv) metal plating (Bai et al., 2016), (v) paint manufacturing (Woldeamanuale and Hassen, 2017), (vi) use of sewage sludge (Akcil et al., 2015) and poor-quality (polluted) water in crop cultivation practices, (vii) specks of dust and aerosols discharged from mining and smelting activities (Shu et al., 2021;Ray and Dey, 2020), (viii) vehicle use (Zhang et al., 2015), and (ix) cement manufacture (Dong et al., 2015) and electronic-waste processing unit (Debnath et al., 2018). Besides these, the natural sources such as volcanic activity, metal corrosion, metal evaporation from soil and water and sediment resuspension, soil erosion, and geological weathering also cause soil pollution. ...
Chapter
Full-text available
Bioremediation among many cleanup technologies, considered an attractive and affordable remediation technology with no side effects on agroenvironment, is adopted to circumvent polluted soils making ecologically disturbed soils cultivable again. Soil microbes spanning different genera and groups evade the toxicity of various environmental contaminants like heavy metals, pesticides, and hydrocarbons. Biofertilizer organisms, among soil microbiomes, have been used in the management of abiotic and biotic stresses and as a formulation to optimize yields and quality of food crops. The exploitation of soil microbes both as pollution alleviating agents (bioremediation) and as crop stimulants (biofertilizers) has provided solutions to both the challenges of environmental stresses and expensive chemical fertilizers. Considering the impactful role of biofertilizers in soil amelioration and plant growth promotion, the priority of current research has been directed toward finding unexplored microbes with dual features as bioremediating materials and as biofertilizers. Despite the growing interest in biofertilizer-based remediation technology, the full potential of this technology has not yet been realized. Recent developments in bacterial biofertilizer (especially nitrogen and phosphate biofertilizers)-based bioremediation of polluted soils and sustainable crop production are reviewed. Here, the microbial formulations, biofertilizer-based strategies for stress management, and their prospects for sustainable crop production are surveyed and presented. Collectively, the information provided herein is desirable to fully explore the bioremediation potential of bacterial biofertilizers and is likely to generate interest for adoption and application of this microbiological technology for remediation of contaminated soils vis-à-vis crop production under both conventional and stressful conditions to satisfy global “food and feed” demands.
... This has inspired modern researchers to look into natural resources for both industrial and domestic applications [1,2]. Among diverse synthetic products, surface-active compounds are widely employed throughout the globe, with an increasing trend of their synthesis and subsequent application [3]. Owing to their distinguished properties, for example dispersion, emulsification, biological activity, surfactants have found several industrial applications [4,5]. ...
Article
This review discusses the classification, characteristics, and applications of biosurfactants. The biosynthesis pathways for different classes of biosurfactants are reviewed. An in-depth analysis of reported research is carried out emphasizing the synthetic pathways, culture media compositions, and influencing factors on production yield of biosurfactants. The environmental, pharmaceutical, industrial, and other applications of biosurfactants are discussed in detail. A special attention is given to the biosurfactants application in combating the pandemic COVID-19. It is found that biosurfactant production from waste materials can play a significant role in enhancing circular bioeconomy and environmental sustainability. This review also details the life cycle assessment methodologies for the production and applications of biosurfactants. Finally, the current status and limitations of biosurfactant research are discussed and the potential areas are highlighted for future research and development. This review will be helpful in selecting the best available technology for biosynthesis and application of particular biosurfactant under specific conditions.
... Hence, remediation of metal pollution from soils is critical (Rathour et al., 2022). Numerous remediation strategies depending on their mobilization or immobilization mechanisms have indeed been established to address these issues (Akcil et al., 2015;Wang et al., 2021). However, they are typically very expensive, and planned remediation is often delayed due to the absence of sufficient funds (Yrjälä and Lopez-Echartea, 2021). ...
Article
A number of anthropogenic and weathering activities accumulate heavy metals in soils, causing adverse effects on soil characteristics, microbial activity (diversity), agricultural practices, and underground aquifers. Controlling soil heavy metal pollution is difficult due to its persistence in soils, resulting in the deposition and transmission into the food web via agricultural food products, ultimately affecting human health. This review critically explores the potential for remediation of metal-contaminated soils using a biochar-based responsible approach. Plant-based biochar is an auspicious bio-based residue substance that can be used for metal-polluted soil remediation and soil improvement as a sustainable approach. Plants with rapid growth and increased biomass can meet the requirements for phytoremediation in large quantities. Recent research indicates significant progress in understanding the mechanisms of metal accumulation and contaminant movement in plants used for phytoremediation of metal-contaminated soil. Excessive contamination reduces plant biomass and growth, which has substantial hyperaccumulating possibilities and is detrimental to the phytoremediation process. Biochar derived from various plant sources can promote the growth and phytoremediation competence of native or wild plants grown in metal-polluted soil. Carbon-enriched biochar encourages native microbial growth by neutralizing pH and providing nutritional support. Thus, this review critically discusses the influence of plant and agricultural waste-based biochar on plant phytoremediation potential in metal-contaminated soils.
... Copper (Cu) is an essential mineral element for plant growth, but it is toxic to plants and animals, including humans when the concentration of copper reaches or exceeds a certain level (Kim et al. 2020;Rakhra et al. 2017;Shahid et al. 2016). At present, the remediation measures of heavy metal pollution mainly include physical (Yuvaraj et al. 2021), chemical remediation (Rambabu et al. 2019), and biological remediation (Akcil et al. 2015;Ndeddy Aka and Babalola 2016). Biochar has the ability to adsorb and passivate heavy metals in soil, which can be used as a remediation approach for heavy metal contaminated soil (Li et al. 2019;Namgay et al. 2010). ...
Article
Full-text available
Copper (Cu) pollution in soils has received considerable research attention globally, and biochar has been widely used as an adsorbent for soil pollution of Cu. However, most of the studies focused on the adsorption capacity of biochar, the bioavailability of Cu absorbed by biochar remains unclear. In this work, rice straw biomass was pyrolyzed under oxygen-limited conditions at 400°C (BC400) and 600°C (BC600), their apparent structure, group characteristics, and basic physical and chemical properties were determined. The isothermal and kinetics adsorption of Cu by BC400 and BC600 were analyzed. A pot experiment was used to evaluate the passivation of Cu in the soil by biochar and the bioavailability of Cu adsorbed by biochar in the soil. The smooth surfaces of BC400 evolved into more rough surfaces for BC600, and both types of surfaces may give active sorption sites for Cu, according to SEM pictures. FTIR analysis suggested that BC600 is endowed with more condensed aromatic carbon structures and more available polar functional groups. The adsorption processes of Cu²⁺ by biochar were better fitted Langmuir equation and pseudo-second-order kinetic model. The adsorption isotherms showed monolayer adsorption of Cu²⁺ on biochar. The maximum adsorption capacities of BC600 and BC400 on Cu²⁺ were 43.75 and 30.70 mg g⁻¹, respectively. Moreover, the pot experiment showed that BC400 and BC600 not only have a strong “passivation” effect on Cu in soil but also prevent the release of adsorbed Cu. Overall, more aromatic carbon structure, more polar functional groups, and higher pH are associated with BC600’s increased Cu immobilization ability in soil.
... Furthermore, the chemical bond formation between biochar's functional groups and Hg demonstrates the removal mechanism. Meanwhile, Pb, Cd, and Cu are common HMs in soils and often co-exist as divalent cations [101]. For instance, Lu et al. [102] stated that co-precipitation and complexation were the dominant mechanisms in Pb removal with sewage sludge-derived biochar, while ion exchange followed by surface complexation on water hyacinth biochar dominantly immobilized the Cd [103]. ...
... Soil remediation is necessary to minimize the impacts on the environment. Both ex situ and in situ remediation require a high efficacy material for the treatment of polluted soil (Akcil et al., 2015). Additionally, considerable costs and time should be taken into account in terms of large-scale implementation. ...
Chapter
Contaminated soils have negative impacts on human health and the environment in many countries. Stabilization/solidification (S/S) as a time- and cost-effective approach is widely used in the remediation of contaminated soil/sediment. However, there are two main limitations for the conventional S/S method: the high carbon footprint and low compatibility. Waste-derived biochar is a carbon-rich, porous, and fine-grained material that has a high sorption capacity for potentially toxic elements. A green and sustainable remediation strategy that utilizes waste-derived biochar for soil/sediment S/S has attracted great attention among scientists. This chapter systematically summarizes mechanisms of biochar-based S/S and S/S performance of various types of biochar, and discusses the benefits, limitations, challenges, and future trends of biochar-based S/S techniques.
... soluble, insoluble and less toxic species (Akcil et al., 2015). ...
Article
Full-text available
Heavy metal contamination of soils has generated two major problems, namely, loss of land value and health risk for people near contaminated sites. Studies on soil remediation are typically conducted on a pilot scale under very controlled conditions. This is a misleading approach, once the complexity of the actual biogeochemical soil conditions may causes inefficiency in full scale real-world application. In addition, environmental impacts of remediation practices themselves are often ignored, which may make them unfeasible. In 2002, an occurrence of mercury in an abandoned old gold mine was detected in a rural area of Descoberto, Brazil. In 2014, the State Public Prosecutor required from the responsible State Environment Agency, a remediation project to the area. This study compares alternatives for remediation of the contaminated area. Also a historical approach on mercury amalgamation in gold mining in the region, in order to estimate the amount of mercury remaining in the site. The geochemical characterization of the contaminated area was performed to describe the contamination process. The results were compared with the remediation proposal advocated by the Brazilian Ministry Public, and some alternatives for decontamination of the area were studied. The electrokinetic method has displayed the lowest overall unit cost, between US$ 120.00/t and US$ 260.00/t. The residual Hg concentration after four cycles of the electrokinetic technique was estimated at 1.28 mg (Hg)/kg (soil), slightly higher than the intervention value for agricultural soil, which is 1.20 mg (Hg)/kg (soil).
... As a result, biochars could be employed as cheap adsorbents to remove organic pollutants as well as heavy metal cations out of the water, including Al and Mn, As, Cd, Cu, Ni, and Pb (Qambrani et al., 2017). According to Beesley et al. (2011), Akcil et al. (2015, heavy metals including Cd, Cu, Pb, and Zn were common contaminants that were present in the sediment, water, and soil systems. More noticeably, the above-mentioned heavy metals' behaviors and characteristics were identical since they always existed as compounds or divalent ions. ...
Article
Wastewater treatment may help to reduce water shortages, whilst concurrently recover energy and nutrients, leading to some of the exploitation of important sources being offset. Compared to other approaches, wastewater purification via adsorption is highly-desirable. The reason is that with this simple and better-to-regenerate technique, heavy metals could be removed even under lower concentration of metal ions. Due to numerous advantages and tunable physicochemical properties, biochar has received most attention for the control of water contamination. This contributes to the solving ecology issues. Significantly, the link between biochar and the rehabilitation of resources should be studied, so that the role of biochar during the wastewater and environmental treatment is well-comprehended and scale-up. In this review, the biochar production from biomass through different routes and their critical properties are critically reviewed and presented. In addition, the activation methods of biochar are also presented and thoroughly compared. More importantly, the application of biochar in heavy metal removal is scrutinized. The factors that affect the heavy metal adsorption capacity and performance are critically evaluated. Finally, limitations and future perspectives for biochar production and application in the removal of heavy metal from wastewater are highlighted in this review.
... Th e growing urbanization and industrialization in the present world have resulted in serious environmental situations due to the discharge of pollutants especially heavy metals pollutants released regularly into the soil environment [1]. Th e contamination of normal water resources and agricultural soil is aff ected by multiple heavy metals due to the use of diff erent fungicides, land chemical fertilizers, wastewater irrigation, and sewage sludge [2,3]. Th us, the protection of the environment from toxic eff ects is necessary for heavy metals through bioremediation [4]. ...
... The treated sediments can be recycled as fill material and blocks (Wang et al., 2015a), aggregates for road construction (Kasmi et al., 2017), cemented mortars (Couvidat et al., 2016), raw materials in brick production (Cappuyns et al., 2015), and at last disposed in sanitary landfills for not hazardous waste. It is noteworthy that S/S treatments generally do not remove the pollutants from the dredged material, but prevent them from leaching, by sealing pollutants inside as transformed less mobile and harmful species (Akcil et al., 2015). ...
Chapter
Full-text available
Contaminants with toxic concentrations in bottom marine sediments represent a serious threat to the environment and human health. Dredging of contaminated sediments with subsequent treatment off-site represents one way to remediate environmentally impacted areas. Among ex situ remediation approaches, stabilization/solidification (S/S) represents a key technology for the production of innovative materials for civil engineering, by treatment and reuse of dredged contaminated sediments. S/S involves the addition of binders and additives to a contaminated material in order to produce more chemically stable constituents and to improve the mechanical behavior of sediment. This chapter explores the main aspects of S/S application to contaminated marine sediments: characterization methods; examples of chemical–physical characterization output; main binders and additives used; examples of S/S application to sediments with only organic and mixed inorganic/organic contamination. Finally, the current lines of research will be outlined.
... Dredged sediments are becoming increasingly considered as a source of construction materials and a suitable solution for sustainable development [4]. Nonetheless, a limited quantity of dredged sediment is used and recycled [5][6][7]. These sediments have a diverse range of characteristics. ...
Article
Full-text available
The valorization of dredged sediments is a promising solution to reduce the strain on natural resources, which is in line with sustainable development goals. This study aims to evaluate the potential valorization of dredged sediment in manufacturing compressed earth blocks (CEBs). The CEBs were stabilized by a combination of fly ash (FA) with sodium hydroxide (NaOH). The stabilization was achieved by partial substitution of sediment for fly ash with six different percentages 10, 20, 30, 40, and 50% by weight. The CEBs samples were characterized in terms of structural, microstructural, mechanical, and thermal properties. The results showed that increasing FA content significantly improves the mechanical strength of CEBs, dry compressive strength ranges from 2.47 MPa to 9 MPa, whereas wet compressive strength ranges from 0.95 MPa to 6.9 MPa. The mechanical performance is related to the amount of alkali-activated fly ash gels, which bind the sediment grains and makes the CEBs more compact and resistant. The optimal dosage of alkali-activated fly ash to replace the sediment was between 10 and 20%. In this substitution range, mechanical performance and physical properties improved significantly. In addition, the thermal properties varied slightly with alkali-activated FA content.
Article
Worldwide, sediments are dredged from water bodies to guarantee proper water levels and remediate aquatic ecosystems. Dredged sediments contain metals that could interfere with recycling if the concentrations overpass permissible limits. Washing of elements from sediments represents a technique to decrease the concentration of metals, and it could introduce a new source of elements. The current study aimed to employ ethylenediamine-tetraacetic acid (EDTA) and ethylenediamine-disuccinic acid (EDDS) and investigate the effect of operational parameters (concentration and pH) on the chemical extraction of metals from dredged sediments. Core sediments were extracted from sampling stations around Malmfjärden bay, Sweden. The results suggested that lead, zinc and copper were the elements with higher extraction rates, followed by arsenic and nickel. Chromium was poorly extracted. EDTA was more efficient than EDDS in dissolving the elements. Moreover, acidic conditions offered higher extraction rates for As using both chelators and for Pb employing EDTA. The 0.05 M concentration presented a higher mean extraction rate than 0.01 M for Cu, Cr and Ni for EDTA and EDDS. The findings in this study suggest that sediment washing is a promising technique to decrease metal concentrations in sediments and enhancing the feasibility to use the material for beneficial uses.
Chapter
Sediments contamination by organic and inorganic pollutants presents a serious risk to human health, fauna, and flora. Stabilization/solidification (S/S) is one of the most used techniques for the management of contaminated sediments. It aims to improve the mechanical and geochemical properties of contaminated sediments by adding cementitious materials. Cement hydration enhances workability, mechanical resistance, and cohesion, while decreasing the permeability of contaminated sediments. Consequently, the inorganic contaminants (e.g., heavy metals) are physically immobilized by decreasing: (1) the available surface area of reactive grains and (2) the contact time between oxidizing agents and reactive grains (enhancing surface runoff). Moreover, the contaminants are also chemically immobilized by (1) their uptake during cement hydration and (2) their precipitation as low-solubility secondary products (e.g., oxyhydroxides). However, contaminants can be remobilized if (1) the physical properties of stabilized sediments are altered due to climatic conditions and/or (2) the geochemical conditions become acidic which may lead to the dissolution of the precipitated contaminants-bearing phases. The efficiency of S/S technology may vary from laboratory to field scale.
Article
The present work discusses the problems and management options of beach wrack and dredged sediments. Beach wrack and dredged sediments near the shores have affected the coastal ecosystem, badly. The piles of beach wrack residues might be a significant emitter of greenhouse gases (GHGs) and dredged sediment is a substantial source of heavy metals and other pollutants. The recovery of valuable resources such as metals and nutrients from these so-called "wastes" is a sustainable strategy to enhance the resilience of the coastal ecosystem and management. The beach wrack meadows can be a potential source for green energy production. Even the demand for biodegradable polymers can be supplied by utilizing the waste beach wracks. The residues of beach wrack species like Posidonia oceanica, Zostera marina, Ulva spc. and Enhalus acorodies can be very beneficial species in terms of economic growth. Red algae have been the most favored and efficient candidate for methane yield. In case of dredged sediment, dewatering of sediment is an essential step for successful resource extraction. Although, extraction methods are almost similar to that applied for soil treatment, which includes pretreatment, physical partitioning, washing, thermal treatment, biological extraction, and immobilization. The fractionation study can be a beneficial tool for determining the metal species present in the sediment. Immobilization techniques are successful but continuous monitoring is required. The vitrification technique is highly effective but very expensive. Thermal treatment is useful for volatile metals such as mercury (Hg), but costs are high. Biological extractions are comparatively cheap but time-consuming. Henceforth, very few extraction methods are available for sediment and required further advancement in this field.
Article
Heavy metal-containing wastes pose long-term environmental threats. In the present work, cementitious binders in the presence of halloysite nanotubes (HNTs) at 1 wt%, 3 wt%, and 5 wt% by mass were used to immobilize lead (Pb(II)). Semi-dynamic leaching tests were used to quantify the Pb(II) leaching up to 64 days. The results showed that the addition of 1 wt%, 3 wt%, and 5 wt% HNTs particles strongly reduced the Pb(II) release. The optimal dosage of HNTs was 3 wt%, which decreased the cumulative release of Pb(II) by around 40.5% after 64 days. Isothermal calorimetry, X-ray diffractometry (XRD), thermogravimetry (TG), mercury intrusion porosimetry (MIP) and compression tests were then used to investigate better immobilization effect with HNTs addition. The results showed that HNTs particles promoted cement hydration, refined the pore structure of the hardened cementitious binders, decreased permeability, and enhanced mechanical strength. Zeta potential measurements indicated that the negative surface charge of the HNTs particles could adsorb Ca²⁺ ions from the pore solution of cement hydration, then facilitating adsorption of Pb(OH)3⁻.
Article
The bioleaching technology has been considered as a promising green technology for remediation of contaminated sediments in recent years. Bioleaching technology was generally conducted in the batch bioreactor; however, the continuous bioreactor should be developed for the application of bioleaching technology in the future. The purposes of this study were to establish a continuous bioleaching process, and to evaluate the effects of sulfur dosage on the efficiency of metal removal during this continuous bioleaching process. The obtained results show that the pH decrease, sulfate production and metal removal efficiency all increased with increasing sulfur dosage in the continuous bioleaching process due to high substrate concentration for sulfur-oxidizing bacteria. After 30 days of operation time, the maximum solubilization efficiencies for Zn, Ni, Cu and Cr were found to be 78%, 90%, 88% and 68%, respectively, at 5% of sulfur dosage. After the bioleaching process, heavy metals bound in the carbonates, Fe-Mn oxides and organics/sulfides in the sediment were effectively removed and the potential ecological and toxic risks of treated sediment were greatly reduced. The results of bacterial community analyses demonstrated that this continuous bioleaching process were dominated by several acidophilic sulfur-oxidizing bacteria; S. thermosulfidooxidans, At. thiooxidans/At. ferrooxidans, S. thermotolerans and At. albertensis, whereas the percentage of less-acidophilic sulfur-oxidizing bacteria (T. thioparus and T. cuprina) was lower than 15% of total bacteria. In addition, the cell numbers of sulfur-oxidizing bacteria increased as the sulfur dosage was increased in the continuous bioleaching process.
Article
A cost-efficient attapulgite-hydrochar composite (APHC) was prepared by a facile one-step hydrothermal treatment and evaluated for cadmium (Cd) immobilization in contaminated soils. The results showed that APHC could effectively reduce the leaching Cd content by 32.1%, and the immobilization efficiency was significantly improved by 70.2% compared to pristine hydrochar (HC). By the introduction of APHC, the contaminated soils showed the highest reduction rate of 91.0% for acid-soluble Cd, and the ecological risk of amended soils was remarkably reduced from high-risk polluted grade to low-risk rank compared to original contaminated soils. The pot experiments indicated that APHC could effectively decrease the adsorbed amount of Cd in paddy rice by 71.2% and reduce the inhibition effect of Cd on plant growth and biomass production. The mechanism study showed that surface complexation, cation exchange and electrostatic attraction played significant roles in immobilizing Cd in contaminated soils. The present study offered a potentially promising approach to prepare cost-effective and eco-friendly amendments from waste biomass for in situ immobilization of heavy metal contaminated soils.
Article
Treating sediment is essential for restoring black-odorous water because it holds many pollutants. High-efficiency chemical methods and low-cost biological methods are usually used for the ex-situ treatment of black-odorous sediment. However, the cost of chemical treatments is high and biological treatment needs a long period. This study involved a combined process coupling pre-biological treatment with post-chemical treatment to treat the raw black-odorous sediment. Two types of waste activated sludge from a secondary sedimentation tank (SST) and a digestion tank (DT) were used for the pre-biological treatment, and hydrogen peroxide was used for post-chemical treatment. Sediment treatment was improved by the combination process, with the SST + 10 mL H2O2/(L sediment) treatment working the optimal. The removal of total nitrogen and total phosphorus reached approximately 71.2% and 52.2%, respectively, and the removal of water and organics reached 29.3% and 17.6%, respectively. MiSeq sequencing found that adding SST sludge improved the microbial community diversity of the sediment, and obviously increased the abundance of microorganisms related to nitrification (such as Nitrospira) and sulfur metabolism (such as Sulfurovum) to 0.6% and 1.2%, respectively. This promoted treatment performance. However, the microbial diversity was reduced after adding the oxidant. This study identified a cost-effective process for treating black-odorous sediment, greatly decreasing the treatment period and cost.
Article
Full-text available
Large quantities of sediment must be dredged regularly to enable marine transport and trade. The sediments are often polluted, with e.g. metals, which limits the management options. The aim of this study has been to assess costs and environmental impacts (impact on climate, marine organisms, etc.) of different management options for polluted dredged sediment, by combining life-cycle assessment (LCA) of the climate impact, scoring of other environmental aspects and a cost evaluation. This approach has been used to study both traditional and new management alternatives for a real port case. The studied options include landfilling, deep-sea disposal, construction of a port area using a stabilization and solidification (S/S) method, and a combination of the aforementioned methods with the innovative option of metal recovery through sediment electrolysis. The LCA showed that deep-sea disposal had the lowest climate impact. The assessment of the other environmental impacts showed that the result varied depending on the pollution level and the time perspective used (short or long-term). Using sediment for construction had the highest climate impact, although other environmental impacts were comparably low. Electrolysis was found to be suitable for highly polluted sediments, as it left the sediment cleaner and enabled recovery of precious metals, however the costs were high. The results highlight the complexity of comparing different environmental impacts and the benefits of using integrated assessments to provide clarity, and to evaluate both the synergetic and counteracting effects associated with the investigated scenarios and may aid early-stage decision making.
Technical Report
Full-text available
Ecological restoration is a set of actions that are conducted to restore nature to a previous state after harmful human impacts. In coastal and marine environments, it may concern transplanting eelgrass shoots or coldwater corals, reconstructing coastal wetlands, or adding nutrient binding substances to counteract remaining eutrophication effects from earlier human activities. Restoration is an active measure, which aims at restoring ecosystems to historically pristine conditions and can be seen as the process to assist the recovery of an ecosystem that has been degraded, damaged or detroyed. The experience with ecological restoration in marine environments is, however, limited, and a rule of thumb is that it is less costly to prevent environmental damage in the coastal zone than to later restore environments. Another rule of thumb is that the activities and pressures originally causing the disturbance/loss should first be remedied in order for restoration measures to be effective. This report aims to provide a rather detailed overview of experiences with ecological restoration in coastal and marine environments, with a particular focus on Sweden. Hopefully, the report will be useful for managers and decision makers and constitute the basis for future restoration projects.
Article
Bioleaching is considered a promising technology for remediating heavy metals pollution in sediments. During bioleaching, the pressure from the metals bioleached is more likely to cause the spread of antibiotic resistance genes (ARGs). The changes in abundance of ARGs in two typical heavy metal bioleaching treatments using indigenous bacteria or functional bacteria agent were compared in this study. Results showed that both treatments successfully bioleached heavy metals, with a higher removal ratio of Cu with functional bacteria agent. The absolute abundances of most ARGs decreased by one log unit after bioleaching, particularly tetR (p = 0.02) and tetX (p = 0.04), and intI1 decreased from 10⁶ to 10⁴ copies/g. As for the relative abundance, ARGs in the non-agent treatment increased from 3.90 × 10⁻⁴ to 1.67 × 10⁻³ copies/16S rRNA gene copies (p = 0.01), and in the treatment with agent, it reached 6.65 × 10⁻² copies/16S rRNA gene copies, and intI1 relative abundance was maintained at 10⁻³ copies/16S rRNA gene copies. The relative abundance of ARGs associated with efflux pump mechanism and ribosomal protection mechanism increased the most. The co-occurrence network indicated that Cu bioleached was the environmental factor determining the distribution of ARGs, Firmicutes might be the potential hosts of ARGs. Compared to bioleaching with indigenous bacteria, the addition of functional bacteria agent engendered a decrease in microbial alpha diversity and an increase in the amount of Cu bioleached, resulting in a higher relative abundance of ARGs. Heavy metal pollution can be effectively removed from sediments using the two bioleaching treatments, however, the risk of ARGs propagation posed by those procedures should be considered, especially the treatment with functional bacteria agents. In the future, an economical and efficient green technology that simultaneously reduces both the absolute abundance and relative abundance of ARGs should be developed.
Chapter
Full-text available
Metal-rich natural and artificial habitats are extreme environments for the evolution of unique microbial communities, which have adapted to deal with the toxic levels of the metals. Diverse microbial groups belonging to Archaea and Bacteria domain possessing different metal-resistance strategies have been found in different metal-contaminated environments using cultivation and molecular approaches. Various metal-resistant bacteria belonging to Bacillus, Arthrobacter, Pseudomonas, Ralstonia, Stenotrophomonas, Desulfovibrio, and other genera were demonstrated a high capacity to the bisorbtion of the different heavy metals. Bacteria and archaea belonging to the genera Acidithiobacillus, Leptospirillum, Sulfobacillus, and Ferroplasma are mostly associated with metal minerals and are involved in the bioleaching processes. Thus, the microbial resistance to toxic heavy metals has fundamental importance in the bioremediation of metal-contaminated natural habitats and bioleaching of valuable metals from complex minerals.
Chapter
Sediments are routinely dredged from harbors, ports, marinas, canals, lakes, lagoons and reservoirs and much of this material is deposited in land-based storage areas. Sediments act as a reservoir for anthropogenic contaminants such as heavy metals which enter the aquatic system both in solution and associated with particulate matter. In sediments, metals exist in forms predominantly adsorbed to metal hydrous oxides, Fe sulfides, calcite and organic matter. After dredged sediments are deposited on land they are dried and converted from a muddy, waterlogged anaerobic material into an aerobic, soil-like medium through a process known as “ripening.” This involves the interaction of physical, chemical and biological processes. Where sediments contain substantial quantities of Fe sulfides (e.g., tidal marine and estuarine environments and eutrophic lakes) pronounced acidification commonly occurs during sulfide oxidation and this can greatly increase metal solubility and mobility. If sediments contain calcite they can have a substantial buffering capacity which counteracts acidification. Where they do not, lime needs to be applied and mixed with the sediment. Most environmental agencies establish regulations for the use of sediments based on total metal contents. To improve interpretation, total contents can be compared with background levels (continental shale levels or those for uncontaminated sediments nearby). In addition, sequential extraction schemes can be used to give an indication of the physico-chemical forms in which metals are present. Common uses for dredged sediments include land reclamation, landscape restoration, and geomaterials for construction. Where levels of metals are considered potentially environmentally damaging, metal mobility can be limited (physical containment, solidification/stabilization, vitrification, phytostabilization) and where levels are excessive metals can be removed from the sediment (washing, thermal extraction, electrokinetics, phytoextraction).
Article
The contamination of aquatic environments with heavy metals is an important issue, and in turn, it is crucial to study remediation techniques that can be applied in situ. In this work, the use of a containment system with macrophytes Limnobium laevigatum is explored in the laboratory to evaluate the remotion of Cr in contaminated sediments. The roots of the plants were placed in contact with the bottom sediment through a containment system. The concentration of Cr in macrophyte and sediment samples exposed to different exposure times (1, 4 and 7 days) was determined by laser-induced breakdown spectroscopy technique. The initial concentration of Cr in the sediment was 112 ± 5 mg/kg and decreased by 65% to the control (p <0.05) after 24 hours of exposure. The removal continued throughout the study time until reaching values of 23 ± 1 mg/kg. In macrophytes, the Cr concentration increased from 20 ± 5 mg/kg to 2066 ± 216 mg/kg after seven days of exposure. The correlation coefficient between Cr concentrations in both matrices was -0.96. Finally, the bioaccumulation factor of Cr in L. laevigatum was 95.22 ± 8.51. Therefore, the system studied could be a potential tool to remedy the bottom sediments of streams and lakes contaminated with heavy metals in situ.
Article
Full-text available
The development of mankind and its necessities inadvertently lead to pollution of various natural resources. The industrial and domestic effluents are greatly contaminated with heavy metal (loid) s. Heavy metals are potential biohazards as they are not degradable and require specially designed sustainable means for detoxification. Biosorption of heavy metals has proved useful in in situ remediation of contaminated resources with minimum generation of toxic sludge. Biosorption depends on the qualities of the metal ions and the biosorbents used in treatment of contaminated sites. The purpose of this review is to identify sources of these pollutants and their effect on biosystems. The review summarises heavy metal toxicity, development of biosorption as a strategy to remove heavy metal contaminants and various available materials for use as biosorbent.
Article
Biochar composites have been widely applied to wastewater and soil remediation due to their advantages of high efficiency, controllability and recyclability. Many studies have demonstrated the application potential of biochar, but little is known about the process and mechanism of surface functionalization of biochar. In this study, an amine-functionalized magnesium ferrite-biochar composite (MgFe2O4–NH2@sRHB) was first synthesized by coprecipitation and then used as a remediation agent to remove heavy metals from aqueous solution and immobilize heavy metals in polluted soils. The results revealed the performance and mechanisms for MgFe2O4–NH2@sRHB to remove or immobilize heavy metals from wastewater or in polluted soils. In wastewater treatment, the mechanisms primarily involved complexation and ion exchange as well as pore filling and electrostatic attraction, and Cd(II) and Pb(II) were adsorbed through a monolayer on the surface of MgFe2O4–NH2@sRHB, with the maximum adsorption capacity reaching 195.50 and 198.93 mg g–1, respectively. In the treatment of soils polluted by heavy metals, MgFe2O4–NH2@sRHB facilitated the transformation of exchangeable Cd to residual and Fe-Mn bound Cd. The addition of 1% MgFe2O4–NH2@sRHB decreased the concentration of exchangeable Cd from 21.0% to 15.2%, 14.8%, 14.8% and 14.6% after 7, 14, 21 and 35 days of treatment, respectively. Electrostatic attraction, precipitation and complexation contributed substantially to the immobilization of heavy metals in the soil. This study provides a new type of biochar composite that can effectively remove and immobilize heavy metals in wastewater and soil at the same time.
Chapter
This chapter focuses on the adsorption of hexavalent uranium (U(VI)), tetravalent thorium (Th(VI)), trivalent samarium (Sm(III)) and divalent copper (Cu(II)) by chemically modified biochar fibers (e.g. luffa, pine needles etc). According to these studies, the adsorption of the four studied (radio)toxic metal ions on different biochar adsorbents, seems to be affected by a set of physicochemical parameters such as the pH, the initial concentration, temperature etc. Generally, the maximum adsorption capacity and kinetic parameters have been evaluated by what best described the experimental data. Comparison of the results indicates that chemical modification of biochars (e.g. oxidation, magnetization etc.), increases their adsorption capacity and chemical affinity for the metal ions. Furthermore, the adsorption of studied metal ions is favored even under acidic conditions and in most cases is an entropy-driven process.
Article
The engineering characteristics of remediated soil are easily affected by CO 2 erosion in nature. However, there are limited investigations on the mechanical and microscopic properties of heavy metal-contaminated soil. This study introduces effect of accelerated carbonization on the mechanical and microscopic properties of nickel–copper-contaminated soil, and the soil has been treated with a novel curing agent, formed by mixing cement, fly ash and desulfurization gypsum (CFG). The objective of the study is to ascertain CO 2 erosion resistance of nickel–copper-contaminated soil solidified by CFG. Using unconfined compressive strength (UCS) tests, carbonization depth, X-ray diffraction, and scanning electron microscopy, the sample’s characteristics are investigated under different carbonization times and heavy metal ion concentrations. The results demonstrate that the UCS of samples of Ni0Cu0, Ni0.02, and Ni0.4 decrease with the increasing carbonization time, while that of Ni1, Cu1, and Ni1Cu1 increase initially and then decrease; in addition, when the concentration of heavy metals is lower, the effect of carbonization on UCS of samples is more significant. Moreover, the carbonization depth of samples increases with the increasing carbonization time, and the prediction model is given. Furthermore, the microscopic analysis demonstrates that calcium carbonate is the main carbonization product. The decomposition of hydrated calcium silicate gel leads to poor integrity of the structure and more pores produced in samples, which is the main reason for the decrease of the UCS in the process of carbonization. The outcomes of this investigation provide a reference for the durability in practical engineering of heavy metal-contaminated soil solidified by CFG.
Article
Full-text available
Preliminary experimental results on the solification/stabilzation of dredged marine sediments (MS) and the non-metallic fraction of automotive shredder residues (NMASR) with coal fly ashes (CFA) are reported. Lab scale experiments of wet granulation at room temperature of these wastes are presented and discussed: cement was used as a binder, while water addition was dosed to optimize granules amount and size. The obtained granules were then subjected to standard leaching tests according to Italian regulation. The results of the leaching tests showed, for all the experimented wastes, a good level of stabilization: heavy metals and ions content was within the limits provided by Italian regulation for landfill disposal as not dangerous waste, while a COD content exceeding the above mentioned limit was detected. This was attributed to plastics and an organic contamination by vehicles fluids in the case of NMASR, and to sulphides and iron content in the case of marine sediments.
Article
Full-text available
Heavy metals are stable and persistence environmental contaminant of marine sediments. The vast increase in population growth, urbanisation and industrialisation leads to increase in of marine discharges, which results in total loads of pollutants being delivered to the sea. Heavy metal pollution in aquatic environment and subsequent uptake in food chain by aquatic organisms and humans put public health at risks. However, even at lower concentrations heavy metals like Cd, Hg, Cr and Pb may exhibit extreme toxicity under certain condition. Thus, this makes regular monitoring of aquatic environment to be more imperative and necessary. This paper therefore, review the occurrence of heavy metals and various speciation methods used for heavy speciation in soil and sediments.
Article
Full-text available
This review presents developments and applications in bioleaching and mineral biooxidation since publication of a previous mini review in 2003 (Olson et al. Appl Microbiol Biotechnol 63:249-257, 2003). There have been discoveries of newly identified acidophilic microorganisms that have unique characteristics for effective bioleaching of sulfidic ores and concentrates. Progress has been made in understanding and developing bioleaching of copper from primary copper sulfide minerals, chalcopyrite, covellite, and enargite. These developments point to low oxidation-reduction potential in concert with thermophilic bacteria and archaea as a potential key to the leaching of these minerals. On the commercial front, heap bioleaching of nickel has been commissioned, and the mineral biooxidation pretreatment of sulfidic-refractory gold concentrates is increasingly used on a global scale to enhance precious metal recovery. New and larger stirred-tank reactors have been constructed since the 2003 review article. One biooxidation-heap process for pretreatment of sulfidic-refractory gold ores was also commercialized. A novel reductive approach to bioleaching nickel laterite minerals has been proposed.
Article
Full-text available
Nonlinear dynamic rolling forces in the vertical and horizontal directions are, respectively, established, considering the impact of vertical and horizontal directions vibration of rolls. Then a vertical-horizontal coupling nonlinear vibration dynamic model of rolling mill rolls is proposed, based on the interactions between this dynamic rolling force and mill structure. The amplitude-frequency equations of the main resonance and inner resonance are carried out by using multiple-scale method. The characteristics of amplitude frequency under nonlinear stiffness, damping, and amplitude of the disturbance are obtained by adopting the actual parameters of 1780 rolling mills. Finally, the bifurcation behavior of the system is studied, and it is found that many dynamic behaviors such as period, period-3 motion, and chaos exist in rolling mill, and this behavior could be restrained effectively by choosing proper system parameters.
Article
Full-text available
Biosorption is a physico-chemical and metabolically-independent process based on a variety of mechanisms including absorption, adsorption, ion exchange, surface complexation and precipitation. Biosorption processes are highly important in the environment and conventional biotreatment processes. As a branch of biotechnology, biosorption has been aimed at the removal or recovery of organic and inorganic substances from solution by biological material which can include living or dead microorganisms and their components, seaweeds, plant materials, industrial and agricultural wastes and natural residues. For decades biosorption has been heralded as a promising cost-effective clean-up biotechnology. Despite significant progress in our understanding of this complex phenomenon and a dramatic increase in publications in this research area, commercialization of biosorption technologies has been limited so far. This article summarizes existing knowledge on various aspects of the fundamentals and applications of biosorption and critically reviews the obstacles to commercial success and future perspectives.
Article
Full-text available
The ability of heavy metals bioaccumulation to cause toxicity in biological systems—human, animals, microorganisms and plants—is an important issue for environmental health and safety. Recent biotechnological approaches for bioremediation include biomineralization (mineral synthesis by living organisms or biomaterials), biosorption (dead microbial and renewable agricultural biomass), phytostabilization (immobilization in plant roots), hyperaccumulation (exceptional metal concentration in plant shoots), dendroremediation (growing trees in polluted soils), biostimulation (stimulating living microbial population), rhizoremediation (plant and microbe), mycoremediation (stimulating living fungi/mycelial ultrafiltration), cyanoremediation (stimulating algal mass for remediation) and genoremediation (stimulating gene for remediation process). The adequate restoration of the environment requires cooperation, integration and assimilation of such biotechnological advances along with traditional and ethical wisdom to unravel the mystery of nature in the emerging field of bioremediation. This review highlights better understanding of the problems associated with the toxicity of heavy metals to the contaminated ecosystems and their viable, sustainable and eco-friendly bioremediation technologies, especially the mechanisms of phytoremediation of heavy metals along with some case studies in India and abroad. However, the challenges (biosafety assessment and genetic pollution) involved in adopting the new initiatives for cleaning-up the heavy metals-contaminated ecosystems from both ecological and greener point of view must not be ignored.
Article
Full-text available
The efficiency and mechanism of nano-hydroxyapatite (nHA) in immobilizing Pb and Cd in contaminated soil were assessed in this work. The X-ray diffraction analysis indicated that the key mechanisms for Pb/Cd immobilization in the soil involve both surface complexation on the surface of nHA and dissolution of the nHA amendments and precipitation of Pb/Cd-containing phosphates. We tested the effects of different nHA dose (the molar ratio of P/(Pb+Cd)) on the water extraction of heavy metals, and phytoavailability of soil metals. The nHA application could significantly reduce water soluble Pb with 72% and Cd with 90%, bioaccessible Pb with a reduction of 12.5-27.5% and Cd with a reduction of 17.66-34.64%, respectively. The nHA reduced phytoavailability of Pb and Cd with 65.3% and 64.6% in contaminated soil, respectively. In addition, the treatment efficiency increased along with the nHA dose (based on the molar ratio of P/(Pb+Cd)) increased, and most effective ratio was molar ratio of P/(Pb+Cd) at 5:1. The results in this study showed that nHA can immobililize Pb and Cd in contaminated soil effectively.
Article
Full-text available
Bioleaching of metal sulfides is performed by a diverse group of microorganisms. The dissolution chemistry of metal sulfides follows two pathways, which are determined by the mineralogy and the acid solubility of the metal sulfides: the thiosulfate and the polysulfide pathways. Bacterial cells can effect this metal sulfide dissolution via iron(II) ion and sulfur compound oxidation. Thereby, iron(III) ions and protons, the metal sulfide-attacking agents, are available. Cells can be active either in planktonic state or in forming biofilms on the mineral surface; however, the latter is much more efficient in terms of bioleaching kinetics. In the case of Acidithiobacillus ferrooxidans, bacterial exopolymers contain iron(III) ions, each complexed by two uronic acid residues. The resulting positive charge allows an electrostatic attachment to the negatively charged pyrite. Thus, the first function of complexed iron(III) ions is the mediation of cell attachment, while their second function is oxidative dissolution of the metal sulfide, similar to the role of free iron(III) ions in non-contact leaching. In both cases, the electrons extracted from the metal sulfide reduce molecular oxygen via a redox chain forming a supercomplex spanning the periplasmic space and connecting both outer and inner membranes. In this review, we summarize some recent discoveries relevant to leaching bacteria which contribute to a better understanding of these fascinating microorganisms. These include surface science, biochemistry of iron and sulfur metabolism, anaerobic metabolism, and biofilm formation. The study of microbial interactions among multispecies leaching consortia, including cell-to-cell communication mechanisms, must be considered in order to reveal more insights into the biology of bioleaching microorganisms and their potential biotechnological use.
Article
Full-text available
Bottom sediments in coastal regions have been considered the ultimate sink for a number of contaminants, e.g., toxic metals. In this current study, speciation of metals in contaminated sediments of Oskarshamn harbor in the southeast of Sweden was performed in order to evaluate metal contents and their potential mobility and bioavailability. Sediment speciation was carried out by the sequential extraction BCR procedure for As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn and the exchangeable (F1), reducible (F2), oxidizable (F3), and residual (R) fractions were determined. The results have shown that Zn and Cd were highly associated with the exchangeable fraction (F1) with 42-58 % and 43-46 %, respectively, of their total concentrations in the mobile phase. The assessment of sediment contamination on the basis of quality guidelines established by the Swedish Environmental Protection Agency (SEPA) and the Italian Ministry of Environment (Venice protocol for dredged sediments) has shown that sediments from Oskarshamn harbor are highly contaminated with toxic metals, especially Cu, Cd, Pb, Hg, As, and Zn posing potential ecological risks. Therefore, it is of crucial importance the implementation of adequate strategies to tackle contaminated sediments in coastal regions all over the world.
Article
Full-text available
An account is presented of a series of investigations and collaborative studies, initiated by BCR, on current methods of metal speciation by extraction of soils and sediments with chemical reagents. It was established by extensive consultation with European experts that the diverse procedures used could be harmonized into agreed methods. These methods, including both single extractant and sequential extraction procedures were subjected to collaborative, interlaboratory trials and the results, presented briefly here, showed that it was both possible and desirable that reference soils and sediments, characterised by certified values for extractable contents, be prepared. As a consequence of these studies two soils have been prepared and will shortly be the subject of interlaboratory analysis with a view to certification of their EDTA and acetic acid extractable contents of some heavy metals. Following this workshop a feasibility study of the agreed sequential extraction procedure will, it is believed, shortly lead to certification of sediments for contents extractable by a defined sequential extraction procedure.
Article
Full-text available
Most sediment dredged in Italian harbours is discharged into coastal areas. Italian legislation provides physical and chemical characterisations of dredged material. However, to determine whether materials are discharged to a dumping site, used for coastal nourishment or other beneficial use, toxicological assessment should be required. In 1995, 12 sediment cores were taken from dredged areas of Viareggio harbour (Tyrrhenian coast). Nine superficial sediments were collected in two coastal areas: a disposal site and a potential nourishment site. Particle size, total organic matter, heavy metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls were analysed. In order to assess sediment toxicity and evaluate the best destination, three bioassays were performed on two harbour and one offshore superficial samples using Vibrio fisheri, Corophium volutator and larvae of Crassostrea gigas.The different harbour areas showed an increase of contaminant levels from the entrance to the inner zones. A comparison of sediment quality of the harbour and coastal areas (physical, chemical and ecotoxicological characteristics) suggested that materials dredged from different areas should be handled in different ways depending on contaminant types and loads. Dredged sediments could be dumped off-shore without decontamination or further use, used to build up eroded areas or be subjected to on-site decontamination treatment.
Article
Full-text available
This study deals with laboratory-scale investigations to evaluate the efficiency of different chemical leaching agents (i.e. sulfuric, oxalic and citric acids) and bioleaching processes (based on different acidophilic bacterial strains) on the mobilisation of metals/semi-metals in contaminated harbour sediments. A simplified life-cycle assessment was also performed in order to compare the investigated strategies in terms of their main environmental impacts. The different chemical leaching agents provided different extraction efficiencies of toxic metals. Among the investigated chemical leaching agents, citric acid 0.5 M and sulfuric acid pH 2 were the most effective, with average mobilisation efficiencies of 30% for Zn and Cr, 40% for Ni, and 35 and 58% for As, under citric and sulfuric acid, respectively. Similar higher extraction efficiencies of metals were also observed in bioleaching experiments with the presence of ferrous iron. The life-cycle assessment revealed that treatments based on diluted sulfuric acid are a better option considering both resource requirements and emissions, leading to lower environmental impacts compared with the other treatment strategies. Overall results from this study provide new insights for the definition of the most efficient and environmentally friendly strategies to be used for dredged sediments contaminated with metals.
Article
Full-text available
The Microbial hydrometallurgy and microbial mineral processing of metal sulphides is currently a well established technology. Over past years there has been a huge amount of developments with regards to the understanding of its both engineering perspective as well as fundamental approach with regards to the microorganisms. The huge diversity of the microorganisms, which has come into picture over the years of research and development have made the engineers to go beyond several limitations of working temperature to salt tolerance of the microorganisms in harsh conditions to deliver better technologies for the future operative plants. Today scientists have been able to deliver the various mechanisms involved in bioleaching but still there are facets to be really understood and more importantly on the front how lab scale research can be turned out into full scale operation by scaling up the research and optimizing the engineering aspects of the research. Most of the bioleaching operation has shown their productivity in commercial application of refractory gold concentrates using mesophilic microorganisms followed by the cyanide leaching to recover optimum amount of gold with an environment friendly method compared to the conventional method of roasting. Research in the area of chalcopyrite bioleaching is still continuing o solve the mysteries of jarosite precipitation and formation of passivation layer, which inhibits the copper recovery in a heap leaching of chalcopyrite by biological methods. Use of extreme thermophiles in chalcopyrite bioleaching is making a revolutionary movement to solve the mystery behind the scaling up the process, which could be possible to be solved in future. Bioleaching with other sulphide minerals together with Acid Mine Drainage (AMD) mitigation, which is a serious concern today, is taking is taking shape today in order to cater the needs of the mankind. However the biohydrometallurgy research seems to contribute to a greater extent in framing environmental friendly process with regards to hydrometallurgical operations in future and establish a developed technology to benefit human beings needs by its upcoming research and development. Keywords: Biomining, refractory gold, copper, chalcopyrite, bioleaching, nickel sulphide, biooxidation, acid mine drainage
Article
Full-text available
Filamentous fungi and lithotrophic bacteria were used to leach heavy metals from dredged sediments in semi-pilot scale air-lift bioreactors. A preliminary physico-chemical characterization of the sediments comprising a sequential extraction study revealed their high metallic contamination and a predominant association of the metals with sulphides and organic matter. The mobility of heavy metals from sediments was ranked by decreasing order as follows: Mn > Zn > Cd > Cu > Pb. The conditions that favoured the solubilization of heavy metals by filamentous fungi turned out to be also favourable for the activity of the sediment organotrophic bacteria. The latter produced organic acids under temporary hypoxic conditions and resulted in the solubilization of 77% of manganese, 44% of zinc, 12% of copper, and less than 2% of cadmium or lead. In general, the fungal organotrophic treatments were limited to the relatively mobile metals due to the weak nature of the organic acids produced and to their microbial consumption under limited saccharose conditions. The lithotrophic treatments yielded higher solubilization results than the organotrophic experiments. Sulphur resulted in a faster, and for some metals such as copper and cadmium, in better bioleaching results compared with reduced iron or with a combination of reduced iron and sulphur. The bioleaching percentages varied between 72 and 93% for cadmium, copper, manganese and zinc, except for lead because of the poor solubility of lead sulphate. The sediment's lithotrophic bacteria acidified the matrix through sulphur oxidation, and leached both loosely and tightly bound metals.
Article
Full-text available
The present study was aimed at assessing the per-formance of different nonliving macrophytes sampled in the Adriatic coast in arsenic(V) sorption. Full factorial experiments were carried out where the main factors were the macrophyte species (brown algae: Cystoseira, Dictyopteris, and Eisenia; green algae: Caulerpa and Ulva; red algae: Ceramium, Gracilaria, and Porphyra; and seagrass: Zostera), biosorbent washing pre-treatment (deionized water, acid pH 2 and basic pH 10), equilibrium pH (in the range 1 to 8), under relatively high (10 mg L −1) and relatively low (100 μg L −1) arsenic concentration. All species exhibited significant adsorption. Indeed, they showed a good performance, with the highest observed value of about 1.3±0.1 mg g −1 for the red alga Ceramium and the seagrass Zostera, comparable with those of activated carbon and other low-cost adsorbents reported in the literature under similar experimental conditions. Moreover, red algae known in the literature to be bad cationic metal sorbents showed very good arsenic sorption performance. This work shows that the performance of arsenic biosorption depends on many factors: the different composition and struc-ture of outer layer of the macrophytes, arsenic speciation and functional group availability under different pH, and eventual counter-ion interactions with arseniate.
Article
The removal of heavy metals from contaminated river sediments was studied using suspension leaching under laboratory conditions and percolation leaching in a pilot plant. The leaching potential of indigenous sulfur-oxidizing bacteria was compared with acid treatment. Bioleaching with elemental sulfur as substrate was found to be better than treatment with sulfuric acid for the solubilization of all metals tested. The physical and chemical properties of the sediments used in this study did not affect leaching capacity under optimum conditions in the laboratory. Under the practical conditions in the pilot plant, the redox state of sludge had a considerable influence on leaching efficiency. In a deposited oxic sediment with good permeability, about 62% of the metals tested were removed by percolation leaching after 120 days. Zn, Cd, Ni, Co and Mn were sufficiently leached to enable treated sediments to be reused as soil. In a freshly dredged anoxic sediment, only a total of 9 % of metals were removed. The results indicate that freshly dredged sediments need to undergo pretreatment before percolation leaching to improve mass transfer and to activate the leaching active bacteria.
Article
The effects of sulfur concentration on the bioleaching of heavy metals from the sediment by indigenous sulfuroxidizing bacteria were investigated in an air-lift reactor. Increasing the sulfur concentration from 0.5 to 5 g/l enhanced the rates of pH reduction, sulfate production and metal solubilization. A Michaelis-Menten type equation was used to explain the relationships between sulfur concentration, sulfate production and metal solubilization in the bioleaching process. After 8 days of bioleaching, 97-99% of Cu, 96-98% of Zn, 62-68% of Mn, 73-87% of Ni and 31-50% of Pb were solubilized from the sediment, respectively. The efficiency of metal solubilization was found to be related to the speciation of metal in the sediment. From economical consideration, the recommended sulfur dosage for the bioleaching of metals from the sediment is 3 g/l.
Article
Management of contaminated sediments, i.e. linking risk assessment and problem solutions, needs both quality criteria respecting recent findings on the bioavailability of pollutants and in-depth knowledge on processes controlling their particular hydrological and biogeochemical dynamics. To understand bioavailability is the key issue for managing contaminated sediments. Therefore, scrutiny of the geochemical situation, toxicity, and biodegradability is needed. The first part of this review refers to the new insights into ‘diagenetic’ mechanisms on particles including ageing and their effects on biological interactions. Chemical and physical methods are described to quantify the retarded desorption behaviour of hydrophobic organic substances and toxic metals. Results of analyses on the extractability of particle-bound pollutants (e.g. solid phase micro-extraction) can be correlated with the bioavailability. Some techniques recently developed to mimic bioavailabilty are briefly summarised. As can be derived from this review, there is a clear need to refine bioavailability models including equilibrium partitioning. A set of bioassays is a powerful supplement to assess sediment quality. Consequently, a paradigm shift should be initiated for the evaluation of biological data. All information of a survey have to be implemented in an assessment scheme. Multivariate statistics and fuzzy mathematics provide promising means to interpret multiple data pattern.
Article
The leaching characteristics of zinc and lead in two contaminated sediments were studied, and the effect of low molecular weight organic acids (LMWOAs) and pH value on the leaching of zinc and lead from two contaminated sediments were examined. The results showed that zinc and lead in the sediments were partly dissolved by three LMWOA solutions under different concentrations in batch experiment. The leaching of heavy metals from two sediments followed the descending order: citric acid > malic acid > tartrate acid (for zinc); citric acid > tartrate acid > malic acid (for lead). The leaching concentrations of heavy metals in solution were enhanced with the increasing of LMWOA concentration and the decreasing of pH value. In addition, all LMWOAs leached more heavy metals than inorganic salt did. The leaching capability under the condition of LMWOAs followed the order: zinc > lead.
Article
Three laboratory experiments investigating the feasibility of extracting lead from saturated Norwegian marine clay by electrokinetic remediation is presented. Cylindrical specimens of 10 cm in diameter and 5 cm in length were treated under constant direct current with electrodes placed at each side of the specimens in a liquid. Electrokinetic remediation enhancement techniques were also investigated by using acetic acid depolarization of the cathode reaction and an ion-selective membrane that veils hydroxyl ion back-transport at the cathode. The results were compared with electrokinetic remediation without enhancement after 52 days of treatment.
Chapter
This article outlines the important biogeochemical roles that fungi play in the degradation, utilization, and transformation of organic and inorganic substrates. Fungal populations are intimately involved in biogeochemical transformations at local and global scales and such processes have major implications for other aspects of living organisms, notably plant productivity and human health. While most prior attention has focused on carbon and nitrogen cycling, the involvement of fungi in almost all other elemental cycles is emphasized. Of special significance are the mutualistic relationships with phototrophic organisms, lichens (algae, cyanobacteria) and mycorrhizas (plants). Some of these fungal transformations have beneficial applications in environmental biotechnology, for example, in metal leaching, recovery and detoxification, and xenobiotic and organic pollutant degradation. Adverse effects may also result when these processes are associated with the degradation of foodstuff, natural products, and building materials.
Article
Most sediment dredged in Italian harbours is discharged into coastal areas. Italian legislation provides physical and chemical characterisations of dredged material. However, to determine whether materials are discharged to a dumping site, used for coastal nourishment or other beneficial use, toxicological assessment should be required. In 1995, 12 sediment cores were taken from dredged areas of Viareggio harbour (Tyrrhenian coast). Nine superficial sediments were collected in two coastal areas: a disposal site and a potential nourishment site. Particle size, total organic matter, heavy metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls were analysed. In order to assess sediment toxicity and evaluate the best destination, three bioassays were performed on two harbour and one offshore superficial samples using Vibrio fisheri, Corophium volutator and larvae of Crassostrea gigas.
Article
The search for cheap and environmentally friendly materials is essential for remediation of heavy-metal-contaminated agricultural soils. A pot experiment was undertaken to evaluate the application of rice straw and filamentous fungus Penicillium chrysogenum (P. chrysogenum) on the fractionation of copper (Cu) and cadmium (Cd), soil microbial properties, and Cu and Cd uptake by romaine lettuce (Lactuca sativa) in a contaminated agricultural soil. Rice straw was applied at three rates (0, 7.8, and 11.7 g kg−1 soil), and in combinations with P. chrysogenum (1.0 × 106 spores g−1 soil). It was found that the combined treatment of rice straw and P. chrysogenum significantly decreased the acid-extractable Cu and Cd by 15.4–25.1% and 20.2–27.3%, and increased the oxidizable Cu and Cd by 16.1–18.0% and 72.1–98.4%, respectively. Soil microbial biomass and fresh weight of lettuce were also remarkably enhanced after rice straw plus P. chrysogenum addition. Rice straw combined with P. chrysogenum was more effective in reducing Cu and Cd uptake by lettuce than rice straw alone. The joint application of rice straw and P. chrysogenum remarkably reduced Cu and Cd concentrations in lettuce shoots by 13.6–21.9% and 32.9–41.7%, respectively. These results indicate that the combined application of P. chrysogenum and rice straw is a promising method to alleviate the bioavailability of metals, and to improve soil microbial properties and plant yield in heavy-metal-polluted agricultural soils.
Article
Economic and environmental assessments of products are commonly performed at product level in a comparative way to identify possible improvement solutions. The problem with this approach is that introduction of new technologies leads to increased functionality that alters the economic and environmental impacts. In addition, a growing market leads to the demand for higher volume of products. When these factors are combined, overall increase in economic and environmental impacts occurs in the society even though improvements were made at product level. Therefore, this research article proposes a new approach to product assessment to cater for technology changes and increasing volume. Using Axiomatic Design Theory, the drivers of economic and environmental impacts are identified by characterising these impacts as a function of product features. The assessment method is applied for a range of functionality and increasing volume to determine the total economic and environmental impact caused in society. Furthermore, ratio analysis is used to determine the economic and environmental impact changes over product generations to identify additional environmental improvements needed to reach target score. The methodology is validated using a comparative case study of different battery technologies for a range of functionality and assumed volume increase in the next generation of batteries to be produced.
Article
The aim of the current work is to develop an environmentally friendly process for the removal of heavy metals (Cu, Zn, Ni, Cd, Al, Cr, Pb) from recycling industry electronic waste with a consortium of Sulfobacillus thermosulfidooxidans and Thermoplasma acidophilum. The performances of commercial S0 powder and biogenic S0 sludge as substrates for the bio-removal of heavy metals were compared. Empirical models for the bioleaching process based on a statistical analysis were developed to evaluate the individual and combined effects of critical variables including S0 dosage, particle size, pulp density and bacterial feed formulation (inoculum size and inoculation style) in shaken flasks while specifying the effective variable ranges. Upscale feasibility experiments in a stirred tank reactor demonstrated a maximum metal bio-removal efficiency (92%) at a 1% dosage of biogenic S0 sludge and 2% dosage of commercial S0 powder (82%), given a 15% pulp density and 150 μm particle size with an intermittent low-concentration addition of inoculum (1x106 cells/mL). Biogenic S0 sludge showed a higher degree of S0 oxidation (95%) in a shorter time period (12 days) compared to commercial S0 powder (82% in 24 days), thereby reducing the process cost. Risk assessments of discarded electronic wastes before and after bioremediation by the toxicity characteristic leaching procedure (TCLP), waste extraction test (WET), synthetic precipitation test (SPLP) and total threshold limit concentration (TTLC) indicated that the leaching/toxicity of bio-remediated residue was well within the regulatory limits.
Article
The driving force behind sustainable behaviour in remediation is poorly understood.•We used factor analysis to classify 27 sustainability considerations.•We used structural equation model to analyse determinants of sustainable behaviour.•The effects of stakeholder influence and institutional pressure were quantified.•The study identified key areas for improvement to promote sustainable practices.
Article
Sandy loam soil polluted with heavy metals (As, Cu, Pb and Zn) from an ancient Mediterranean Pb mining and metallurgy site was treated by means of wet high-intensity magnetic separation to remove some of the pollutants therein. The treated fractions were chemically analysed and then subjected to magnetic characterisation, which determined the high-field specific (mass), magnetic susceptibility (κ) and the specific (mass) saturation magnetisation (σS), through isothermal remanent magnetisation (IRM) curves. From the specific values of κ and σS, a new expression to assess the performance of the magnetic separation operation was formulated and verified by comparison with the results obtained by traditional chemical analysis. The magnetic study provided valuable information for the exhaustive explanation of the operation, and the deduced mathematical expression was found to be appropriate to estimate the performance of the separation operation. From these results we determined that magnetic soil washing was effective for the treatment of the contaminated soil, concentrating the majority of the heavy metals and peaking its separation capacity at 60% of the maximum output voltage.
Article
Several methods to evaluate the environmental process impact assessment of industrial chemical processes have been presented in the literature. Although these methods follow the same steps (usually, characterisation, normalisation and weighting), each method addresses different impact categories, considering specific nomenclatures and using different taxonomies to classify their outputs. When industrial chemical processes are being assessed by several methods, different results are obtained. The comparison of these non-standardised results turns out to be a difficult task. This work has two main contributions that help in the choice of the most appropriate method to be used. First, standardise the taxonomy used by the different methods and second, propose a quantitative framework that combines different methods into a final score. Therefore, it is suggested a standard taxonomy, which allows to report the output of the different methods in a systematic way. A new concept called impact categorical groups is also proposed. These groups aggregate similar impact categories presented by different methods, and therefore allow the comparison of the obtained results by different methods. A framework to aggregate impact category indicators from different methods into a final score (index) is also presented. This framework also suggests a path to determine the best method to be applied and provides an insight on the weighting factors that should be considered in the aggregation of the different indicators into the final index. The basis for the proposed achievements was an extensive literature review, which includes 25 methods for environmental process impact assessment.