Bacillus sp. Abq, belonging to Bacillus cereus sensu lato, was isolated from an aquifer in New Mexico, USA and phylogenetically classified. The isolate possesses the unusual property of precipitating Pb(II) by using cysteine, which is degraded intracellularly to hydrogen sulfide (H2S). H2S is then exported to the extracellular environment to react with Pb(II), yielding PbS (galena). Biochemical and growth tests showed that other sulfur sources tested (sulfate, thiosulfate, and methionine) were not reduced to hydrogen sulfide. Using equimolar concentration of cysteine, 1 mM of soluble Pb(II) was removed from Lysogeny Broth (LB) medium within 120 h of aerobic incubation forming black, solid PbS, with a removal rate of 2.03 µg L−1 h−1 (∼8.7 µM L−1 h−1). The mineralogy of biogenic PbS was characterized and confirmed by XRD, HRTEM, and EDX. Electron microscopy and electron diffraction identified crystalline PbS nanoparticles with a diameter <10 nm,  localized in the extracellular matrix and on the surface of the cells. This is the first study demonstrating the use of cysteine in Pb(II) precipitation as insoluble PbS and it may pave the way to PbS recovery from secondary resources, such as Pb-laden industrial effluents.

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INSTRODUCTIONWhen determining the impact of a sewage treatment plant on particular elements of an aqueous environment, it is often improperly assumed that the receiver waters are mixed with purified sewage at the point of discharge or not far from that site. The route of total mixing of pollutants with receiver waters may be several hundred times longer than the width of the riverbed. In fact, the total mixing of wastewater with receiver waters does not always occur at a short distance from the discharge. Determining the distance, at which full mixing should be considered in a given river cross-section in vertical and transverse dimensions [Rutherford, 1994, Miakoto, 2005. Determining the distribution of pollutants within the mixing zone is essential to understand the impact of purified wastewater on aquatic organisms, fish migration, and the health of people using the surface water. Due to this, it is also possible to simulate changes in the quality of river water and to obtain information on the possibility of discharging the purified sewage to surface waters. When forecasting changes in surface water quality, it is very important to learn the concentration distribution within the mixing zone because a large area of excessive concentration of harmful and hazardous components can be found within it. This would result in a reduction in water intake for utility purposes and disturbance of habitats responsible for biodiversity conservation [Adamski, 2000, Ostroumov, 2004, Miakoto, 2005.Mixing of wastewater with receiver waters is possible due to the advection and turbulent and molecular diffusion. The result of these processes is balancing the concentrations of wastewater constituents in the whole volume of water [Ru- Research Article ABSTRACT Discharges from wastewater treatment are among the key sources of pollution, if norms included in the applied legal acts are exceeded. In determining the impact of these objects on water environment it is often assumed that complete mixing wastewater with surface water is in the point or close to the discharge. In fact, the complete mixing of waste water in a short distance from the discharge occurs incidentally depending on the type of sewage receiver. The size and type of specific sewage receiver determines the conditions of self-purification. Complete mixing zone has a huge impact on the intensity of self-purification processes. Therefore, the possibility to determine the size zone of complete mixing of the waste water from the water receiver is important. The issue involves a series of methods, the most computational, which more or less allows to evaluate the distance of mixing waste water. advection, turbulent and molecular diffusion affect mixing wastewater with surface waters. The article discusses the factors influencing the mixing process and the impact of mixing on the self-purification surface waters. The aim of the article is a review of several methods for determining the distance of the segment mix completely discharged wastewater, with regard to the location o...

The aim of the work was to analyze the content of Ni, Pb and Cd in organs (root, stem, leaf) Typha latifolia L. and Nuphar lutea as well as bottom sediments of the Ełk River and selected tributaries. An attempt was also made to indicate the factors and processes governing the behavior of the investigated metals in the water environment of the examined rivers. The research object was the Ełk River with its three tributaries-the Gawlik River, the Binduga River and the Kuwasy Canal. Samples of bottom sediments, leaves, stems and roots of Typha latifolia L. and Nuphar lutea were collected in August of 2015. The content of metals was determined by flame atomic absorption spectrometry (F-AAS). The results of analyses of sediments and plant material indicate a lack of environmental pollution by nickel (2.58-8.50 mg•kg −1) and lead (3.82-15.99 mg•kg −1) of the Ełk River and its tributaries whereas the cadmium content ranged from 0.16-0.76 mg•kg −1. Nuphar lutea and Typha latifolia L. showed a varied capacity to accumulate nickel (1.20-10.51 mg•kg −1) and lead (0.04-14.16 mg•kg −1), occurring primarily in the roots. The smallest concentration of nickel and lead was recorded in the stems. The highest concentration of cadmium (2.56 mg•kg −1) was noted in the roots and the lowest (0.01 mg•kg) in the leaves. Factor analysis pointed to the processes of mobilizing elements from bottom sediments as a result of pH drop and their uptake by macrophyte roots and sorption processes of metal ions by macrophytes from river waters and their intensive accumulation in bottom sediments.

Significance and Impact of the Study: This study provides evidence of the medium-to-high removal of metals and metalloids present in real industrial effluents by using naturally sourced metal-resistant bacterial inocula. Apart from the applied research significance, the coupling of cysteine degradation to metal removal sheds light into the microbially driven natural attention of industrial pollution in specific geochemical settings. The results warrant the scaling up of the process to treat larger effluent volumes and potentially recover valuable metals in the form of metal sulphides.