Methodological approach to characterizing pollution of natural water bodies using satellite data with account of aggregation of finely dispersed mineral processing waste

The level of the environmental impact of the mining industry specifies the urgency of ecological management of the natural resources based on the satellite monitoring data. The high content of the suspended mineral particles in the industrial waters and the requirement to reduce their access to the natural water reservoirs determine the need to characterize the mininginduced pollution that can be carried out correctly with due account of the aggregate stability of dispersions. In spite of the theoretical concepts, prediction of the particles aggregation is limited by a lack of data on their interaction parameters. In order to parametrize the interactions in the mineral-water-mineral system it is proposed to use experimental data on aggregation of finely dispersed particles, obtained by the laser diffraction method in the equilibrium conditions. For this purpose the procedure of the experimental appraisal of the effective Hamaker constants has been elaborated using ores of developed deposits of the Kola mining complex as an example. The authors have studied the conditions of the surface layer of natural water reservoirs in the most industrially developed central part of the Murmansk region and defined characteristics of pollution with finely dispersed by-products of the mineral raw material treatment, according to the satellite observation data of the spatial distribution of the normalized difference turbidity index. The authors have established that the least propagation of the pollution into the natural water reservoirs is observed in the case of the apatite-nepheline ores processing by-products, which is explained by the effective aggregation of the finely dispersed nepheline particles. The proposed approach to apply data on mineral particles aggregation for interpretation of the satellite observations does not require carrying out in-situ observations and makes it possible to identify the mining-induced pollution of natural water reservoirs in industrial territories using suspended particles.

Alleviation of Ultrafiltration Membrane Fouling by ClO2 Pre-Oxidation: Fouling Mechanism and Interface Characteristics

In order to alleviate membrane fouling and improve removal efficiency, a series of pretreatment technologies were applied to the ultrafiltration process. In this study, ClO2 was used as a pre-oxidation strategy for the ultrafiltration (UF) process. Humic acid (HA), sodium alginate (SA), and bovine serum albumin (BSA) were used as three typical organic model foulants, and the mixture of the three substances was used as a representation of simulated natural water. The dosages of ClO2 were 0.5, 1, 2, 4, and 8 mg/L, with 90 min pre-oxidation. The results showed that ClO2 pre-oxidation at low doses (1–2 mg/L) could alleviate the membrane flux decline caused by humus, polysaccharides, and simulated natural water, but had a limited alleviating effect on the irreversible resistance of the membrane. The interfacial free energy analysis showed that the interaction force between the membrane and the simulated natural water was also repulsive after the pre-oxidation, indicating that ClO2 pre-oxidation was an effective way to alleviate cake layer fouling by reducing the interaction between the foulant and the membrane. In addition, ClO2 oxidation activated the hidden functional groups in the raw water, resulting in an increase in the fluorescence value of humic analogs, but had a good removal effect on the fluorescence intensity of BSA. Furthermore, the membrane fouling fitting model showed that ClO2, at a low dose (1 mg/L), could change the mechanism of membrane fouling induced by simulated natural water from standard blocking and cake layer blocking to critical blocking. Overall, ClO2 pre-oxidation was an efficient pretreatment strategy for UF membrane fouling alleviation, especially for the fouling control of HA and SA at low dosages.

Geochemical Markers as a Tool for the Characterization of a Multi-Layer Urban Aquifer: The Case Study of Como (Northern Italy)

The analysis of geochemical markers is a known valid tool to explore the water sources and understand the main factors affecting natural water quality, which are known issues of interest in environmental science. This study reports the application of geochemical markers to characterize and understand the recharge areas of the multi-layer urban aquifer of Como city (northern Italy). This area presents a perfect case study to test geochemical markers: The hydrogeological setting is affected by a layered karst and fractured aquifer in bedrock, a phreatic aquifer hosted in Holocene sediments and connected with a large freshwater body (Lake Como); the aquifers recharge areas and the water geochemistry are unknown; the possible effect of the tectonic setting on water flow was overlooked. In total, 37 water samples were collected including water from two stacked aquifers and surface water to characterize hydrochemical features. Moreover, six sediment samples in the recent palustrine deposits of the Como subsurface were collected from cores and analyzed to understand the main geochemistry and mineralogy of the hosting material. The chemical analyses of water allow to observe a remarkable difference between the shallow and deep aquifers of the study area, highlighting different recharge areas, as well as a different permanence time in the aquifers. The sediment geochemistry, moreover, confirms the differences in trace elements derived from sediment-water interaction in the aquifers. Finally, an anomalous concentration of As in the Como deep aquifer was observed, suggesting the need of more detailed analyses to understand the origin of this element in water. This study confirms the potentials of geochemical markers to characterize main factors affecting natural water quality, as well as a tool for the reconstruction of recharge areas.

Cloud point extraction associated with differential pulse voltammetry: preconcentration and determination of trace uranyl in natural water

A procedure for electroanalytical determination of the uranyl ions pre-concentrated from natural water by cloud point extraction (CPE) was developed in this work. The CPE parameters, such as surfactant concentration,...

Chemical and membrane desalination of natural water with high content of iron-organic compounds

Under the conditions of modernization of Russian thermal power plants (TPP), water treatment plants based on imported membrane technologies are often put into operation without consideration of the quality of the source (natural) water and variable-performance operating modes. At the same time long-running water treatment plants and their capabilities are not considered. In this regard, the cost of additional water is three or more times higher, and the average output is respectively lower than at traditional water treatment plants. Often, one doesn’t take the advantages of reverse osmosis installations based on the rejection of the use of aggressive reagents such as sulfuric acid, etc. The aim of the study is to increase the efficiency of desalinated water production. It is especially important to conduct studies of natural waters with high content of iron-organic compounds characteristic of the regions of the center and north of Russia. The authors have carried out laboratory studies of various, primarily new filter materials, regents, and devices, both at the stages of pre-purification of water i.e., clarification, and at the stages of demineralization of clarified water. Water treatment plants of Ivanovo combined-cycle plant (CCP) and Cherepovets state district power station (GRES) are considered as the subject of the research. It is found out that if one applies ion-exchange and membrane water treatment technologies to treat water with high content of iron-organic compounds, high-quality desalinated water can be obtained. The properties of water are the following: specific electrical conductivity of no more than 0,2 mcm/cm and permanganate oxidizability of no more than 1 MgO/l. Results of studies at the Ivanovo CCP and Cherepovets GRES have shown practicability to coagulate water with aluminum sulfate using an anionactive flocculant, for example, during the flood period. Application of coagulation and ultrafiltration units before reverse osmosis installation ensures removing organic impurities from the water. Based on the obtained research results, recommendations are given for the implementation of the results at Ivanovo water treatment plants.

3D Impedimetric Biosensor for Cyanobacteria Detection in Natural Water Sources

The excessive growth of cyanobacteria in freshwater sources produces the development of toxic blooms mainly due to the production of cyanotoxins. Here, a novel impedimetric biosensor based on a three-dimensional interdigitated electrode array (3D-IDEA) for detection of cyanobacteria cells is reported. The 3D-IDEA sensor surface biofunctionalization was performed by means of the layer-by-layer method using polyethyleneimine (PEI) as the anchoring layer and concanavalin A (Con A) as the bioreceptor to lipopolysaccharides of cyanobacteria cells. The developed PEI-Con A 3D-IDEA sensors show a linear response (R2 = 0.992) of the impedance changes (RS) versus the logarithm of cyanobacteria concentrations in the range of 102–105 cells·mL−1 with the detection limit of 100 cells·mL−1. Moreover, to prevent the interference from components that may be present in real water samples and minimize a possible sample matrix effect, a filtration methodology to recover cyanobacterial cells was developed. The proposed methodology allows 91.2% bacteria recovery, permitting to obtain results similar to controlled assays. The developed system can be used in aquatic environments to detect cyanobacteria and consequently to prevent the formation of blooms and the production of cyanotoxins. Con A can bind to most polysaccharides and so react with other types of bacteria. However, currently, on the market, it is not possible to find specific biorecognition elements for cyanobacteria. Taking into consideration the specificity of samples to be analyzed (natural water resources), it is difficult to expect high concentration of other bacteria. In this sense, the developed methodology may be used as an alarm system to select samples for more thorough and precise laboratory analysis.