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     

Occurrence and distribution of novel botryococcene hydrocarbons in freshwater wetlands of the Florida Everglades

A high abundance of isoprenoid hydrocarbons, the botryococcenes, with carbon numbers from 32 to 34 were detected in the Florida Everglades freshwater wetlands. These compounds were present in varying amounts up to 106microg/gdw in periphyton, 278microg/gdw in floc, and 46microg/gdw in soils. Their structures were determined based on comparison to standards, interpretation of their mass spectra and those of their hydrogenation products, and comparison of Kovats indexes to those reported in the literature. A total of 26 cyclic and acyclic botryococcenes with 8 skeletons were identified, including those with fewer degrees of unsaturation, which are proposed as early diagenetic derivatives from the natural products. This is the first report that botryococcenes occur in the Everglades freshwater wetlands. Their potential biogenetic sources from green algae and cyanobacteria were examined, but neither contained botryococcenes. Thus, the source implication of botryococcenes in this ecosystem needs further study.     

Abundance, behavior, and movement patterns of western gray whales in relation to a 3-D seismic survey, Northeast Sakhalin Island, Russia

A geophysical seismic survey was conducted in the summer of 2001 off the northeastern coast of Sakhalin Island, Russia. The area of seismic exploration was immediately adjacent to the Piltun feeding grounds of the endangered western gray whale (Eschrichtius robustus). This study investigates relative abundance, behavior, and movement patterns of gray whales in relation to occurrence and proximity to the seismic survey by employing scan sampling, focal follow, and theodolite tracking methodologies. These data were analyzed in relation to temporal, environmental, and seismic related variables to evaluate potential disturbance reactions of gray whales to the seismic survey. The relative numbers of whales and pods recorded from five shore-based stations were not significantly different during periods when seismic surveys were occurring compared to periods when no seismic surveys were occurring and to the post-seismic period. Univariate analyses indicated no significant statistical correlation between seismic survey variables and any of the eleven movement and behavior variables. Multiple regression analyses indicated that, after accounting for temporal and environmental variables, 6 of 11 movement and behavior variables (linearity, acceleration, mean direction, blows per surfacing, and surface-dive blow rate) were not significantly associated with seismic survey variables, and 5 of 11 variables (leg speed, reorientation rate, distance-from-shore, blow interval, and dive time) were significantly associated with seismic survey variables. In summary, after accounting for environmental variables, no correlation was found between seismic survey variables and the linearity of whale movements, changes in whale swimming speed between theodolite fixes, mean direction of whale movement, mean number of whale exhalations per minute at the surface, mean time at the surface, and mean number of exhalations per minute during a whales surface-to-dive cycle. In contrast, at higher received sound energy exposure levels, whales traveled faster, changed directions of movement less, were recorded further from shore, and stayed under water longer between respirations.     

Environmental risks of farmed and barren alkaline coal ash landfills in Tuzla, Bosnia and Herzegovina

The disposal of coal combustion residues (CCR) has led to a significant consumption of land in the West Balkan region. In Tuzla (Bosnia and Herzegovina) we studied previously soil-covered (farmed) and barren CCR landfills including management practises, field ageing of CCR and the transfer of trace elements into crops, wild plants and wastewaters. Soil tillage resulted in mixing of cover soil with CCR. Medicago sativa showed very low Cu:Mo ratios (1.25) which may cause hypocuprosis in ruminants. Total loads of inorganic pollutants in the CCR transport water, but not pH ( approximately 12), were below regulatory limits of most EU countries. Arsenic concentrations in CCR transport water were <2microgl(-1) whereas reductive conditions in an abandoned landfill significantly enhanced concentrations in leachates (44microgl(-1)). The opposite pattern was found for Cr likely due to large initial leaching of CrVI. Public use of landfills, including farming, should be based on a prior risk assessment due to the heterogeneity of CCR.     

The effect of the Sars-Cov-2 pandemic on the use of personal protective equipment in hospitals

The Covid pandemic has strongly affected the use of personal protective equipment (PPE) in the medical sector. Our aim was to assess the influence of Covid on PPE use within a German hospital by analyzing PPE use in four years prior to Covid and in 2020/2021. Numbers of items and mass of different types of PPE were determined based on procurement data. The results show that for the use of gloves the pandemic only had a small effect on the number of items. For body protection there was a clear trend toward a decrease in the number of items used in the years before the pandemic due to actions by the hospital toward a better environmental footprint which was partially reversed by the pandemic. The number of masks on the other hand doubled during the pandemic. Expressed in mass of PPE per patient and day, 15 g of masks, 121 g of gloves, and 183 g of body protection are used, resulting in a total of 319 g of PPE per patient and day. As medical waste has a specific treatment, no direct environmental effects of PPE use in hospitals in a region with well-developed waste treatment system are expected.

     

Combined application of marble waste and beneficial microorganisms: toward a cost-effective approach for restoration of heavy metals contaminated sites

Environmental Science and Pollution Research - Heavy metal (HM) pollution and the need to preserve the environment have gathered increasing scientific attention. The immobilization of HMs into...