Miljana Prica

Correlation between the results of sequential extraction and effectiveness of immobilization treatment of lead- and cadmium-contaminated sediment.

The assessment of the quality of sediment from the Great Backi Canal (Serbia), based on the pseudo-total lead (Pb) and cadmium (Cd) content according to the corresponding Dutch standards and Canadian guidelines, showed its severe contamination with these two metals. A microwave-assisted BCR (Community Bureau of Reference of the Commission of the European Union) sequential extraction procedure was employed to assess their potential mobility and risk to the aquatic environment. Comparison of the results of sequential extraction and different criteria for sediment quality assessment has led to somewhat contradictory conclusions. Namely, while the results of sequential extraction showed that Cd comes under the high-risk category, Pb shows low risk to the environment, despite its high pseudo-total content. The contaminated sediment, irrespective of the different speciation of Pb and Cd, was subjected to the same immobilization, stabilization/solidification (S/S) treatments using kaolinite, montmorillonite, kaolinite-quicklime, montmorillonite-quicklime, fly ash, zeolite, or zeolite-fly ash combination. Semi-dynamic leaching tests were conducted for Pb- and Cd-contaminated sediment in order to assess the long-term leaching behavior of these metals. In order to simulate “worst case” leaching conditions, the semi-dynamic leaching test was modified using 0.014 M acetic acid (pH = 3.25) and humic acid solutions (20u2009mg TOC l-1) as leachants instead of deionized water. The effectiveness of S/S treatment was evaluated by determining diffusion coefficients (De) and leachability indices (LX). The standard toxicity characteristic leaching procedure (TCLP) was applied to evaluate the extraction potential of Pb and Cd. A diffusion-based model was used to elucidate the controlling leaching mechanisms. Generally, the test results indicated that all applied S/S treatments were effective in immobilizing Pb and Cd, and the treated sediments may be considered acceptable for “controlled utilization” based on LX values, irrespective of their different availability in the untreated samples. In the majority of samples, the controlling leaching mechanism appeared to be diffusion, which indicates that a slow leaching of Cd and Pb could be expected when the above S/S agents were applied. The TCLP results showed that all S/S samples were nonhazardous.

Quantifying the environmental impact of As and Cr in stabilized/solidified materials.

The assessment of the quality of sediment from the Great Backi Canal (Serbia) based on the pseudo-total As and Cr content according to the corresponding Dutch standards and Canadian guidelines showed its severe contamination with these two elements. Microwave assisted BCR sequential extraction procedure was employed to assess their potential mobility and risk to the aquatic environment. Comparison of the results of sequential extraction and different criteria for sediment quality assessment has led to somewhat contradictory conclusions. While the results of sequential extraction showed that Cr comes under the medium risk category, As shows no risk to the environment, despite of its high pseudo-total content. The contaminated sediment, irrespective of the different distribution of As and Cr, was subjected to the same immobilization, stabilization/solidification (S/S) treatment. Semi-dynamic leaching test was conducted for As and Cr contaminated sediment in order to assess the long-term leaching behavior of these elements. In order to simulate worst case leaching conditions, the test was modified using acetic acid and humic acid solution as leachants instead of deionized water. The effectiveness of S/S treatment was evaluated by determining diffusion coefficients. Four different single-step leaching tests were applied to evaluate the extraction potential of As and Cr. A diffusion-based model was used to elucidate the controlling leaching mechanisms. The test results indicated that all applied S/S treatments were effective in immobilizing As and Cr, irrespective of their different availabilities in the untreated samples. In most treated samples, the controlling leaching mechanism appeared to be diffusion, which indicates that a slow leaching of As and Cr could be expected.

Degradation of Anthraquinone Dye Reactive Blue 4 in Pyrite Ash Catalyzed Fenton Reaction

Pyrite ash (PA) is created by burning pyrite in the chemical production of sulphuric acid. The high concentration of iron oxide, mostly hematite, present in pyrite ash, gives the basis for its application as a source of catalytic iron in a modified Fenton process for anthraquinone dye reactive blue 4 (RB4) degradation. The effect of various operating variables such as catalyst and oxidant concentration, initial pH and RB4 concentration on the abatement of total organic carbon, and dye has been assessed in this study. Here we show that degradation of RB4 in the modified Fenton reaction was efficient under the following conditions: pH = 2.5; [PA]0 = 0.2u2009gu2009L−1; [H2O2]0 = 5u2009mM and initial RB4 concentration up to 100u2009mgu2009L−1. The pyrite ash Fenton reaction can overcome limitations observed from the classic Fenton reaction, such as the early termination of the Fenton reaction. Metal (Pb, Zn, and Cu) content of the solution after the process suggests that an additional treatment step is necessary to remove the remaining metals from the water. These results provide basic knowledge to better understand the modified, heterogeneous Fenton process and apply the PA Fenton reaction for the treatment of wastewaters which contains anthraquinone dyes.

Correlation of different pollution criteria in the assessment of metal sediment pollution.

In this article an assessment of the sediment metal pollution (cadmium, copper, chromium, lead, nickel, zinc) in the Veliki Backi canal (Serbia) was carried out using pseudo-total metal content, contamination factor (CF), pollution load index (PLI) and enrichment factor (EF). The study also encompassed pore-water metal concentrations and an assessment of sediment pollution based on the analysis of simultaneously extracted metals (SEM), acid volatile sulphides (AVS) and the sequential extraction procedure. The concentrations of metals are likely to result in harmful effects based on the comparison with sediment quality guidelines (Dutch, Canadian, US EPA - United States Environmental Protection Agency). The ratio of simultaneously extracted metals and volatile acid sulphides was found to be greater than 1 in only one location, which is already recognized as a place of high risk based on the criteria applied. Other samples had Σ[SEM]/[AVS] < 1, despite their high risk classification based on the applied criteria. According to the sequential extraction procedure, zinc and nickel exhibit high risk in most samples, whereas other metals show low and medium risk. The CF values for Cr, Cu and Zn were > 6 in most samples, which denotes very high contamination by these metals. The PLI values indicated moderate and high pollution. The EF values for all metals studied except for Cd in some cases were >1.5, suggesting anthropogenic impact. The obtained results will be invaluable for future activities regarding sediment monitoring and will facilitate the selection of appropriate criteria when evaluating sediment quality.

Influence of pH and ozone dose on the content and structure of haloacetic acid precursors in groundwater

This study investigated the effects of pH (6–10) and ozone dose [0.4–3.0xa0mg O3/mg dissolved organic carbon (DOC)] on the content and structure of haloacetic acid (HAA) precursors in groundwater rich in natural organic matter (NOM; DOC 9.85u2009±u20090.18xa0mg/L) during drinking water treatment. The raw water was ozonated in a 2 L glass column. NOM fractionation was carried out using XAD resins. HAA formation potential (HAAFP) was determined according to standard EPA Method 552. NOM characterization revealed it is mostly hydrophobic (65xa0% fulvic and 14xa0% humic acids). Hydrophobic NOM significantly influences HAA formation, as confirmed by the high HAAFP (309u2009±u200915xa0μg/L). Ozonation at pHxa06–10 led to changes in NOM structure, i.e. complete humic acid oxidation, and increased the hydrophilic NOM fraction content (65–90xa0% achieved using 3.0xa0mg O3/mg DOC). The highest degree of NOM oxidation and HAA precursor removal was achieved at pHxa010 (up to 68xa0% HAAFP). Ozonation pH influenced the distribution of HAA precursor content, as increasing the pH from 6 to 10 increased the reactivity of the hydrophilic fraction, with the HAAFP increasing from 19.1u2009±u20096.0xa0μg/mg DOC in raw water to 152u2009±u20098xa0μg/mg DOC in ozonated water. The degree of HAA precursor removal depends on the dominant oxidation mechanism, which is related to the applied ozone dose and the pH of the oxidation process. Ozonation at pHxa010 favours the mechanism of radical NOM oxidation and was the most effective for HAAFP reduction, with the efficacy of the process improving with increasing ozone dose.

Immobilization of Cadmium from Contaminated Sediment Using Cardboard Mill Sludge

Abstract Sludge from cardboard mill is most commonly landfilled, but it could also be recycled on-site into production or reused in some other way. In this study the use of sludge from cardboard mill as stabilizing agent in the stabilization treatment of cadmium polluted sediment was examined. The effectiveness of treatment and long-term leaching behavior of cadmium was evaluated by determining the cumulative percentage of cadmium leached, diffusion coefficients (De) and by applying different leaching tests (semi-dynamic test, toxicity characteristic leaching procedure, waste extraction test). In order to simulate the “worst case” leaching conditions, the semi-dynamic leaching test was modified using 0.014 M acetic acid (pH = 3.25) and humic acids solution (20 mg l-1 TOC) as leachants instead of deionized water. A diffusion-based model was used to elucidate the controlling leaching mechanisms. Applied treatment was effective in immobilizing cadmium irrespective of high availability in the untreated sample. The controlling leaching mechanism appeared to be diffusion, which indicates that a slow leaching of cadmium could be expected when the cardboard mill sludge as stabilization agent is applied.

Evaluating the necessity for thermal treatment in clay-based metal immobilization techniques as an environmentally acceptable sediment remediation process

PurposeThe objective of this research was to apply the same immobilization (stabilization/solidification) clay-based treatments to sediment contaminated with different metals (Pb, Cd, Ni, Zn, Cu, Cr) with different distributions and availabilities in sediment. We also examined the possibility of using clay as an immobilization agent without the application of thermal treatment, in order to reduce the economic cost of this expensive remediation procedure.Materials and methodsClay from a canal in Vojvodina, Republic of Serbia, was used as the immobilization agent in a stabilization/solidification treatment to remediate metal-contaminated sediment. Semi-dynamic and toxicity characteristic leaching tests were conducted to assess the effectiveness of the nonthermal and thermal immobilization treatments with clay, and the long-term leaching behavior of these metals was determined using the following parameters: cumulative percentage of metals leached; diffusion coefficients; leachability indices; and toxicity characteristic leaching test concentration.Results and discussionBased on these parameters, both clay-based treatments were effective in immobilizing metals in the contaminated sediment. Results suggest that both heating temperature and clay proportion in the sediment–clay mixture impact the degree of metal immobilization.ConclusionsClay-based products are potentially good immobilization materials for metal-contaminated sediments, with the distribution of metals in the original sediment not influencing the efficacy of the treatments. Even without the thermal treatment, the metals were effectively immobilized. The leaching of metals was largely inside the regulatory limits and the treated samples can be regarded as nonhazardous materials. This justifies the choice of not applying the more expensive thermal treatment during remediation, especially when treating sediments containing a mixture of pollutants.

Preliminary evaluation of galvanic sludge immobilization in clay-based matrix as an environmentally safe process.

This study attempts to determine the possibilities and limitations of the immobilization of galvanic wastes by their incorporation into clay-based materials. It focuses on the effects of several processing parameters such as the temperature of thermal treatment, the relative amount of sludge, and the physico-chemical aspects of the sample, on the fixing level of relevant metals (Zn, Ni, Fe, Mn, Pb, Cu, Cr) in thermally treated clay-based samples. The effectiveness of sludge inactivation was assessed by water-leaching test and conductivity measurements. In view of the potential use of the sludge stabilization products as construction materials, the linear shrinkage and bending strain of the fired samples was investigated. To characterize their morphology, mineralogy and composition, fired samples of clay and its mixtures with galvanic sludge were studied on a scanning electron microscope (SEM) coupled with an energy dispersive X-ray analyser (EDS) and X-ray diffractometer (XRD). It was found that the efficiency of metal immobilization is dependent on the clay composition and the temperature of the thermal treatment of the prepared mixtures. The thermal treatment of all samples at all temperatures resulted in the stabilization of all heavy metal ions (copper, nickel, iron, lead, manganese and zinc) with the exception of chromium.

Influence of Electric Field Operation Modes on Nickel Migration during Electrokinetic Treatment

ABSTRACT Nickel-contaminated sediment can be remediated by electrokinetic techniques. In practical application, nickel may migrate into deep layers and potentially pollute unpolluted layers. In this study, the influence of different types of electric field operation modes on nickel migration in sediment layers was studied. The following experiments were conducted: without current application (NC), with horizontal electric field (HEF), with vertical electric field (VEF), and 2D electric field (horizontal and vertical). The following Ni overall removal efficacies were achieved: 48.9, 49.4, 55.7, and 58.1 after VEF, NC, 2D, and HEF, respectively. Using a vertical electric field in 2D and VEF resulted in less Ni found in the vertical sediment bed (25% and 60%, respectively). The available Ni content in a contaminated sediment bed decreased significantly after using the electrokinetic treatments: 46%, 62%, and 79% after HEF, VEF, and 2D, respectively. Vertical electric field is the most efficient for Ni removal in terms of the amount of Ni that migrated into deeper layers of sediment bed and its amount in mobile form. Thus, the vertical electric field is a promising and practical method for the remediation of nickel-contaminated sediments. Risk analysis indicated the efficiency of EK treatment as available Ni content was reduced after the applied treatments to a degree that poses no risk for the environment.