Selective removal of heavy metals from metal-bearing wastewater in a cascade line reactor

Goal, Scope and Background This paper is a part of the research work on ‘Integrated treatment of industrial wastes towards prevention of regional water resources contamination — INTREAT’ the project. It addresses the environmental pollution problems associated with solid and liquid waste/effluents produced by sulfide ore mining and metallurgical activities in the Copper Mining and Smelting Complex Bor (RTB-BOR), Serbia. However, since the minimum solubility for the different metals usually found in the polluted water occurs at different pH values and the hydroxide precipitates are amphoteric in nature, selective removal of mixed metals could be achieved as the multiple stage precipitation. For this reason, acid mine water had to be treated in multiple stages in a continuous precipitation system-cascade line reactor. Materials and Methods All experiments were performed using synthetic metal-bearing effluent with chemical a composition similar to the effluent from open pit, Copper Mining and Smelting Complex Bor (RTB-BOR). That effluent is characterized by low pH (1.78) due to the content of sulfuric acid and heavy metals, such as Cu, Fe, Ni, Mn, Zn with concentrations of 76.680, 26.130, 0.113, 11.490, 1.020 mg/dm³, respectively. The cascade line reactor is equipped with the following components: for feeding of effluents, for injection of the precipitation agent, for pH measurements and control, and for removal of the process gases. The precipitation agent was 1M NaOH. In each of the three reactors, a changing of pH and temperature was observed. In order to verify efficiency of heavy metals removal, chemical analyses of samples taken at different pH was done using AES-ICP. Results Consumption of NaOH in reactors was 370 cm³, 40 cm³ and 80 cm³, respectively. Total time of the experiment was 4 h including feeding of the first reactor. The time necessary to achieve the defined pH value was 25 min for the first reactor and 13 min for both second and third reactors. Taking into account the complete process in the cascade line reactor, the difference between maximum and minimum temperature was as low as 6°C. The quantity of solid residue in reactors respectively was 0.62 g, 2.05 g and 3.91 g. In the case of copper, minimum achieved concentration was 0.62 mg/dm³ at pH = 10.4. At pH = 4.50 content of iron has rapidly decreased to < 0.1 mg/dm³ and maintained constant at all higher pH values. That means that precipitation has already ended at pH=4.5 and maximum efficiency of iron removal was 99.53%. The concentration of manganese was minimum at pH value of 11.0. Minimum obtained concentration of Zn was 2.18 mg/dm³ at a pH value of 11. If pH value is higher than 11, Zn can be re-dissolved. The maximum efficiency of Ni removal reached 76.30% at a pH value of 10.4. Discussion Obtained results show that efficiency of copper, iron and manganese removal is very satisfactory (higher than 90%). The obtained efficiency of Zn and Ni removal is lower (72.30% and 76.31%, respectively). The treated effluent met discharge water standard according to The Council Directive 76/464/EEC on pollution caused by certain dangerous substances into the aquatic environment of the Community. Maximum changing of temperature during the whole process was 6°C. Conclusion This technology, which was based on inducing chemical precipitation of heavy metals is viable for selective removal of heavy metals from metal-bearing effluents in three reactor systems in a cascade line. Recommendations and Perspectives The worldwide increasing concern for the environment and guidelines regarding effluent discharge make their treatment necessary for safe discharge in water receivers. In the case where the effluents contain valuable metals, there is also an additional economic interest to recover these metals and to recycle them as secondary raw materials in different production routes. ESS-Submission Editor: PhD Hailong Wang, hailong.wang@ensisjv.com     

Distribution and fractionation of heavy metals in the Tisa (Tisza) River sediments

Introduction In this work, sediments of the River Tisa (Tisza) are studied to assess their environmental pollution levels for some major heavy metals, as well as to predict the investigated elements’ mobility on the basis of their association type with the substrate. The Tisa River catchments area is a subbasin of the River Danube. Part of this river, 166 km long, belongs to the Serbian province of Vojvodina, before it flows into the Danube. It has been chosen for our investigation, because it has been exposed to intense pollution in the last decades. Materials and Methods The river sediment samples were collected at 32 locations. The proportions of sand, silt and clay fractions were determined. The sequential extraction procedure following a modified Tessier method was applied for speciation of the metal forms in the collected samples. The metal concentrations of Zn, Cd, Pb, Ni, Cu, Cr, Fe and Mn in extracts were determined by atomic absorption spectroscopy. Results and Discussion Granulometric analysis showed that some 50% of the Tisa River sediments were silt and clay, while the rest was sand with quartz, as the main constituent. The average metal content of the surface river sediment samples for every fraction of sequential extraction was presented and discussed in relation to pH, Eh and metal fractionation. The average metal content from the Tisa River sediments, obtained as an average of the metal’s concentration released in all five sequential extraction fractions was compared with: average metal contents of the Tisa River sediments in Hungary, metal content in soils formed on the Tisa River alluvium of Vojvodina, average metal content in soils of Vojvodina, and average metal content in soils of Hungary. An assessment of metal pollution levels in Tisa River sediments was made by comparing mean values for obtained results for the Tisa River sediments with the freshwater sediment’s Quality Guidelines as published by US EPA, Environment Canada and soil standards for Serbia. Conclusion According to US EPA and Canadian Quality Guidelines for freshwater sediments, the concentration of heavy metals in Tisa sediments were: (a) much higher than defined concentrations below which harmful effects on river biota are unlikely to be observed, (b) below defined concentrations above which harmful effects on river biota are likely to be observed. The concentration levels of Pb, Ni, Cu and Cr in Tisa River sediments are safe when compared with Serbian MAQ (Maximum Allowed Quantity) standards for soils, but they are unsafe in the case of Zn and Cd. Recommendations and Outlook The quality of sediments in the Tisa River was on the border line between potentially polluted and polluted. This line could very easily be exceeded since the quality of sediments in the Tisa River in Hungary was already worse than in Serbia. These results indicated the need for further monitoring of heavy metals in that locality.     

Levels of PAHs in the soils of Belgrade and its environs

Polycyclic aromatic hydrocarbons (PAHs) were analysed in 39 soil samples (0–10 cm upper layer) collected in Belgrade, the capital of Serbia. The sampling sites were randomly selected from urban, urban/recreational and rural areas; the samples were collected in April and December 2003 and July and October 2004. The sum of the 16 PAHs corresponding to the recreational zone (298 μg/kg) was close to the urban zone (375 μg/kg). Mean soil ΣPAH concentration from rural areas was 18 μg/kg dry weight. Comparing to values observed in the urbanized locations around the world, the overall levels of PAHs in this study are low. The PAH ratios obtained pointed to a domination of pyrogenically formed PAHs in the examined soils. The dominant PAHs in soil samples in urban zones were fluoranthene, benz[a]anthracene, phenanthrene and pyrene, mostly emitted from noncatalyst vehicles which are still in use in Serbia. The total carcinogenic potency for each sampling site was calculated. Regardless of the used carcinogenic activity factors, carcinogenic potency of 7 sites were 3–9 times higher than the reference ones indicating the increased carcinogenic burden of soils from these sites.     

Bioaccumulation of Metals in Fish of Salmonidae Family and the Impact on Fish Meat Quality

The study was aimed at determining the levels of metals in water samples and muscles of the fish caught in the Una River basin, located in the northwestern part of Bosnia and Herzegovina. For that purpose, three fish species: Brown Trout (Salmo trutta m. fario), Grayling (Thymallus thymallus) and Californian Trout (Salmo gairdneri), together with stem water samples, were analyzed for metal concentrations (Pb, Hg, Cd, As, Mn, Ni, Cu, Cr, Se, Co, Sn, Zn, Fe, Ca, P) during a 2-year period. The fish was captured using electric fishing, nets or fishing equipment. The capture was undertaken on three sites (the river source, the middle flow and the river mouth) of each of the five biggest rivers belonging to the Una River basin (Unac, Krušnica, Sana, Klokot, and Una). The concentrations of metals in each sample were determined via atomic absorption spectrophotometry. In the tested waters, the presence of Mn in concentrations higher than permitted (0.07 mg/l) had been detected. In the tested meat, the following average concentrations of metals (mg/kg) had been found: Pb (0.67), Cd (0.06), Mn (0.65), Ni (0.15), Cu (0.79), Cr (1.05), Se (0.03), Zn (8.92), Fe (5.40), Ca (14.68), and P (10.85). The correlation between Mn concentrations identified in the tested waters and those identified in the meat of Brown Trout was revealed to be statistically significant, which confirms that, over time, bioaccumulation of metals took place. Even though the results were not indicative of contamination, they strongly suggest that constant monitoring of the ecosystems in reference should be implemented.     

REP-LECOTOX: an example of FP 6 INCO project to strengthen ecotoxicological research in WBC (Western Balkan countries)

Background

In order to map exceedances of critical atmospheric deposition loads for nitrogen (N) surface data on the atmospheric deposition of N compounds to terrestrial ecosystems are needed. Across Europe such information is provided by the international European Monitoring and Evaluation Programme (EMEP) in a resolution of 50 km by 50 km, relying on both emission data and measurement data on atmospheric depositions. The objective of the article at hand is on the improvement of the spatial resolution of the EMEP maps by combining them with data on the N concentration in mosses provided by the International Cooperative Programme on Effects of Air Pollution on Natural Vegetation and Crops (ICP Vegetation) of the United Nations Economic Commission for Europe (UNECE) Long-range Transboundary Air Pollution (LTRAP) Convention.

Methods

The map on atmospheric depositions of total N as modelled by EMEP was intersected with geostatistical surface estimations on the N concentration in mosses at a resolution of 5 km by 5 km. The medians of the N estimations in mosses were then calculated for each 50 km by 50 km grid cell. Both medians of moss estimations and corresponding modelled deposition values were ln-transformed and their relationship investigated and modelled by linear regression analysis. The regression equations were applied on the moss kriging estimates of the N concentration in mosses. The respective residuals were projected onto the centres of the EMEP grid cells and were mapped using variogram analysis and kriging procedures. Finally, the residual and the regression map were summed up to the map of total N deposition in terrestrial ecosystems throughout Europe.

Results and discussion

The regression analysis of the estimated N concentrations in mosses and the modelled EMEP depositions resulted in clear linear regression patterns with coefficients of determination of r ² = 0.62 and Pearson correlations of r _p = 0.79 and Spearman correlations of r _s = 0.70, respectively. Regarding the German territory a nationwide mean of 18.1 kg/ha/a (standard deviation: 3.49 kg/ha/a) could be derived from the resulting map on total N deposition in a resolution of 5 km by 5 km. Recent updates of the modelled atmospheric deposition of N provided a similar estimate for Germany.

Conclusions

The linking of modelled EMEP data on the atmospheric depositions of total N and the accumulation of N in mosses allows to map the deposition of total N in a high resolution of 5 km by 5 km using empirical moss data. The mapping relies on the strong statistical relationship between both processes that are physically and chemically related to each other. The mapping approach thereby relies on available data that are both based on European wide harmonized methodologies. From an ecotoxicological point of view the linking of data on N depositions and those on N bioaccumulation can be considered a substantial progress.     

Assessment of PAH pollution in the southern Baltic Sea through the analysis of sediment, mussels and fish bile

The concentrations of fifteen PAH compounds in samples of sediment and blue mussel tissue (Mytilus trossulus) were measured. In addition, the biliary polycyclic aromatic hydrocarbon metabolites present in flounder (Platichthys flesus) were analysed. Two methods were used in the analysis of PAH metabolites; high performance liquid chromatography (HPLC) and fixed wavelength fluorescence (FF). The major PAH metabolite which could be measured using the HPLC method was 1-OH pyrene. It was possible to detect 1-OH Phe and 3-OH B[a]P in 70 and 24 samples respectively, of the 87 samples analysed. However, the concentrations of 1-OH Phe and 3-OH B[a]P were below or near to the LOQ (0.002 μg ml(-1) bile). The bile of flounder samples from the Gulf of Gdańsk had 1-OH Pyr concentrations which ranged from 0.019 to 0.066 μg ml(-1) bile. The high linear correlation observed between the quantity of 1-OH pyrene determined by the HPLC-F method and the content of the sum of pyrene-type PAHs obtained by the FF method indicated the FF method of determination of pyrene-type PAH metabolites can be used as a screening method. The content of ∑(15)PAHs in sediments collected in the Gulf of Gdansk, in 2008, ranged from 29.3 to 103 μg kg(-1) dw. In mussel tissue ∑(15)PAHs concentrations were between 173.2 μg kg(-1) dw and 237.7 μg kg(-1) dw. All concentrations measured in the current study, in mussel tissue, were below the OSPAR toxicity threshold values.     

Carcass disposal and siting controversy: Risk,dialogue and confrontation in the 2001 foot-and-mouth Outbreak

Abstract

This paper examines controversy during the 2001 foot-and-mouth outbreak after mass carcass burial sites were selected at two sites in northeast England, and focuses on shortcomings in public consultation surrounding the carcass disposal policy. The slaughter of six million animals necessitated a national disposal strategy on a hitherto unknown scale. The belated decision to concentrate carcass disposal in a small number of mass burial sites provoked more opposition in the two ex-mining localities selected in the northeast than anywhere else. In both cases local liaison committees were established to manage dialogue between residents and public authorities. We argue that, although seen by the authorities primarily as a vehicle for risk communication and public reassurance, for residents these functioned chiefly as a vehicle for holding public authorities to account. These divergent purposes were overshadowed by the chaotic circumstances in which the early stages of the mass burial policy were implemented, and the way in which the carcass disposal policy was dictated by the operation of the slaughter policy, whose draconian form precluded any but the most cursory public consultation.     

An assessment of organizational resilience potential in SMEs of the process industry,a fuzzy approach

In order to establish adequate tools for the modern business environment, and with a need for new mechanisms with the goal of overcoming crisis and emerging disorder, the concept of organizational resilience has emerged. A high level of organizational resilience represents one of an organization's target values during a normal period of operation. In a period of crisis, the presence of resilience is even more needed; this is emphasized in the process industry because in these conditions when one process fails it may cause significant problems in other processes. The contribution of this paper is shown through a fuzzy mathematical model for assessment of organizational resilience potential in SMEs of the process industry. The model is verified through an illustrative example where obtained data suggest measures which should enhance business strategy and improve organizational resilience factors. This study forms the basis for a survey that may include a significant number of organizations from one region and future improvement based on benchmark and knowledge sharing.