WHAT DETERMINES THE WATER QUALITY

In natural waters as a highly complex environment, a different matter, regardless of whether they are natural water ingredients or substances which mature in water by man activity, are subject to one or several different processes. Physical, chemical or biochemical processes are determining finding shapes, behavior and fate of substances in the aquatic environment. Particularly important are: dissolution, adsorption, evaporation, photolysis, hydrolysis, oxidation-reduction, metabolic processes, and bioaccumulation. Depending on which processes are dominant in a given locality, what is the chemical composition of soil, biological activity, and human influence will determine quality of water, whether it is surface, underground or atmospheric. This paper presents the underlying processes that affect water quality. All processes are illustrated by example

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 (20 mg 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

Organic pollution in sediment-water systems on the Ratno Ostrvo location in Novi Sad, Serbia and Montenegro

ABSTRACT: Two-year (2001Two-year ( -2002 monitoring was conducted to determine residues of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides in sediment-water systems of three types of watercourses on the location of Ratno Ostrvo in Novi Sad (Serbia and Montenegro). Types of watercourses were established on the basis of the flow regime: drainage ditches with 1-2 m 3 /s (four sampling points), the DTD Canal with up to 10 m 3 /s (three sampling points) and the Danube River with 1500-3000 m 3 /s (five sampling points). Water quality was compared with the requirements given by the national and Dutch regulations, and the quality of sediment with the Dutch and Canadian quality guidelines, due to the lack of national legislaton. Based on the concentrations of organic pollutants in the samples of sediments and water from selected sampling points, average annual values were computed for the three types of watercourses. Great differences regarding the level of pollution between two years of monitoring were in smaller watercourses -drainage ditches and the DTD Canal, which might be a consequence of water flow, increased anthropogenic activity, decrease of self-purification potential. Concentrations of both PAHs and pesticides were below national maximum permissible levels in water and below Dutch intervention levels in sediment. Standard deviations of average annual concentrations were very high (up to 30-300%), probably because of the increased anthropogenic effect

Photochemical degradation of alachlor in water

This study investigates the photochemical degradation of alachlor, a chloroacetanilide herbicide. All experiments were conducted in ultra-pure deionized water (ASTM Type I quality) using direct ultraviolet (UV) photolysis and the UV/H2O2 advanced oxidation process. The direct UV photolysis and UV/H2O2 experiments were conducted in a commercial photochemical reactor with a quartz reaction vessel equipped with a 253.7 nm UV low pressure mercury lamp (Philips TUV 16 W). The experimental results demonstrate that UV photolysis was very effective for alachlor degradation (up to 97% removal using a high UV fluence of 4200 mJ/cm2). The UV/H2O2 process promoted alachlor degradation compared to UV photolysis alone, with a high degree of decomposition (97%) achieved at a significantly lower UV fluence of 600 mJ/cm2 when combined with 1 mg H2O2/L. The application of UV photolysis alone with a UV fluence of 600 mJ/cm2 gave a negligible 4% alachlor degradation. The photo degradation of alachlor, in both direct UV photolysis and the UV/H2O2 process, followed pseudo first-order kinetics. The degradation rate constant was about 6 times higher for the UV/H2O2 process than for UV photolysis alone

Immobilization of Cadmium from Contaminated Sediment Using Cardboard Mill Sludge

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

Solidification/stabilization of metal polluted sediment of Krivaja river

The Krivaja River is the longest natural water body (109 km) that flows completely within the borders of Serbian province of Vojvodina. In the absence of national legislation, the sediment quality was assessed in accordance with the Dutch classification methodology. It was found that the river sediment is highly contaminated with copper and zinc (192 mg kg-1 and 1218 mg kg-1 respectively), and as such is an extreme risk to the environment and human health. The solidification/stabilization (S/S) treatment with local clay, that has high capacity of cation exchange 70.2 meq/100 g and specific surface area of 630 m2 g-1, was employed for remediation of the contaminated sediment. The sequential extraction procedure showed that the copper and zinc have medium risk for the environment, with the percentage in the carbonate fraction of 18 and 22% respectively. The results of sequential extraction are not in full agreement with the results of pseudo-total metal concentration in the sediment, which only confirms that the total metal concentration is not sufficient to define the real danger to the environment. Based on the pseudo-total metals concentration, the sediment is of Class 4 (Dutch standards). However, judging from the results of sequential extraction, the metals show medium risk. Obviously, these results have to be taken into account in the assessment of the sediment quality, remediation procedures and sediment disposal in general. After the treatment, the proportion of these two metals in the first fraction is significantly reduced (Cu less than 2%, Zn 10%) in most of samples. In order to determine the long-term behavior of S/S mixtures, leaching tests were conducted in accordance with semi-dynamic ANS diffusion test for 90 days. The results indicated that clay can effectively immobilize Cu and Zn: the cumulative leached fraction of copper in mixtures with clay was in the range from 0.001% (mixture with 80% clay) to 0.15% (mixture with 10% clay), and the cumulative leached fraction of zinc in the range of 0.06% (mixture with 80% clay) to 0.10% (mixture with 10% clay). The diffusion coefficients, ranging from 1.5×10-12 cm2s-1 to 3.7×10-14 cm2s-1, showed an effective immobilization of both metals which suggests that these metals are practically immobilized in S/S mixtures even if the level of clay is low. From the point of LX values, all S/S mixtures can be used for the controlled utilization, because the leaching indices ranged from 11.8 to 13.4 for both metals. In all clay and sediment mixtures the dominant leaching mechanism is diffusion (slope values of 0.35 to 0.60), which once again confirms the effectiveness of the applied treatment and can be expected that only a very small amount of contaminants would leach into the environment over time. Future research is heading in the direction of troubleshooting the accumulation of used natural adsorbent after treatment, the possibility of permanent disposal, its regeneration or the possibility of its application as construction material

Toxic metal immobilization in contaminated sediment using bentonite- and kaolinite-supported nano zero-valent iron

This paper reports from a pilot study conducted in an ongoing research project focusing on how users and their needs are being part of the development of smart grid services. The project aims to explore how development and use of services related to smart grids in homes might affect practices involving electricity consumption. The empirical material centers around an urban development project with a focus on social sustainability. So far only preliminary remarks can be made, and these points to that smart grid services are not in the center of attention, but rather taken for granted, and that the users are rather absent from the discussions. This indicates that the practices of which electricity consumption are part are not taken into consideration, but instead it is taken for granted that users shall adjust their needs based on information about electricity consumption patterns and prices