The Role of Macrophytes in Constructed Surface-flow Wetlands for Mine Water Treatment: A Review

Constructed wetlands are a standard sustainable technology in waste and mine water treatment. Whereas macrophytes actively contribute to decomposition and/or removal of wastewater’s organic pollutants, removal of hydrolysable metals from mine water is not attributable to direct metabolic, but rather various indirect macrophyte-related mechanisms. These mechanisms result in higher treatment efficiency of (vegetated) wetlands relative to (unvegetated) settling ponds. Contribution of macrophytes to treatment predominantly includes: enhanced biogeochemical oxidation and precipitation of hydrolysable metals due to catalytic reactions and bacterial activity, particularly on immersed macrophyte surfaces; physical filtration of suspended hydrous ferric oxides by dense wetland vegetation down to colloids that are unlikely to gravitationally settle efficiently; scavenging and heteroaggregation of dissolved and colloidal iron, respectively, by plant-derived natural organic matter; and improved hydrodynamics and hydraulic efficiency, considerably augmenting retention and exposure time. The review shows that constructed surface-flow wetlands have considerable advantages that are often underestimated. In addition to treatment enhancement, there are socio-environmental benefits such as aesthetic appearance, biotope/habitat value, and landscape diversity that need to be considered. However, there is currently no quantitative, transferrable approach to adequately describe the effect and magnitude of macrophyte-related benefits on mine water amelioration, let alone clearly assign optimal operational deployment of either settling ponds or wetlands. A better (quantitative) understanding of underlying processes and kinetics is needed to optimise assembly and sizing of settling ponds and wetlands in composite passive mine water treatment systems.

INTELLECTUALIZATION OF THE PROCESSES OF MONITORING THE STATE OF THE MOBILE TECHNOLOGICAL COMPLEX OF MINE WATER TREATMENT

The research is aimed at solving some problems of controlling the processes of monitoring the process of mine water purification by mobile technological complexes with variations in its costs and physical and chemical characteristics. The initial data are the results of discrete and continuous monitoring of the characteristics of the treated water and the technological mode of reagent-free water treatment by a mobile technological complex. The analysis of the problems that arise when choosing the observation procedures necessary to solve the problem of predicting a non-stationary random process with varying mathematical expectation, variance, and the type of distribution laws itself is performed. To ensure the stability of the water treatment process in the statistical sense, a procedure for parametric identification of the predictive model from a limited sample is proposed. The requirements for monitoring the quality of process management at the upper hierarchical level of the mine water treatment management system are formulated.

Active Treatment of Contaminants of Emerging Concern in Cold Mine Water Using Advanced Oxidation and Membrane-Related Processes: A Review

Responsible use and effective treatment of mine water are prerequisites of sustainable mining. The behavior of contaminants in mine water evolves in relation to the metastable characteristics of some species, changes related to the mine life cycle, and mixing processes at various scales. In cold climates, water treatment requires adaptation to site-specific conditions, including high flow rates, salinity, low temperatures, remoteness, and sensitivity of receiving waterbodies. Contaminants of emerging concern (CECs) represent a newer issue in mine water treatment. This paper reviews recent research on the challenges and opportunities related to CECs in mine water treatment, with a focus on advanced oxidation and membrane-based processes on mine sites operating in cold climates. Finally, the paper identifies research needs in mine water treatment.

Data Support in the Choice of Mine Water Treatment Technology

Mathematical modeling is used in this work in the analysis of options for the implementation of acid mine water treatment technology. Ta technological scheme of metal-bearing mine water treatment is proposed and includes two stages. The first stage, the treatment of mine water to the required degree to extract solid insoluble sediment for further processing, is implemented in a mobile technological complex installed in places of mine water outpouring. Selective extraction of individual metal powders is delivered in a stationary complex in applying the centrifugal conversion method using plasmatron. In the first step, the metal ions contained in the mine water should be complete recovered with maximum energy-saving. The condition for complete extraction of useful components from mine waters is pH values corresponding to the beginning of precipitation of hydroxides of various metals and complete precipitation, which depend on the nature of metals, their concentration in solution, temperature, impurity content. The process regime must be manageable to ensure its adequacy in the quality of raw materials under conditions of changing mine water flow rates and concentrations of ingredients. The technological mode must be manageable to ensure its adequacy in the raw material quality under changing mine water discharges and concentrations of ingredients. Keywords: technological complex, mine water, treatment, modeling

Electrodialysis desalination and limiting concentration of highly mineralized waters

We study the regularities of the process of desalination of sodium chloride solutions with a limiting concentration of 10.2 to 37.7 g/dm3, which simulate chloride wastewater of some mining enterprises. We use an electrodializerconcentrator with advanced design developed at A.V. Dumansky Institute of Colloid Chemistry and Water Chemistry of the NASU. The need to develop such device is caused by the necessity of the deep concentration of concentrates obtained during the wastewater treatment in order to facilitate their further processing into secondary material resources. The electrodialyzers produced by the industry are unsuitable for a significant concentration, since the concentration chambers in such devices and the desalination chambers are pumped with the initial solution. This leads to a significant reduction in the concentration of the resulting brine. Studies have shown that the use of the specified electrodializer-concentrator allowed one to obtain for 100 min from solutions with a concentration of 10.2, 18.8, and 37.7 g/dm3 Cl-ion diluents containing them, respectively, 0.2, 0.6, and 1.0 g/dm3 and to concentrate the brine by 10.6, 6.7, and 4.0 times, respectively. Based on this research and the experience gained at the Institute in the field of mine water treatment, a basic block diagram of the mine water treatment is developed. It is based on a combination of advanced electroodialysis and reverse osmosis. The complex processing of substances removed during the mine water treatment involves their use in relevant industries; additional desalination diluent can be used for technical purposes, and its excess is discharged into reservoirs.

Removal of Fluoride Ions from the Mine Water

Murmansk Region is home to some major mining and mineral sites. One of the most challenging environmental problems in themining industry is mine water treatment. For example, the rocks of the deposit operated by Lovozero Mining and Mineral ProcessingCompany contain villiomite (NaF). It is highly soluble in water, and the mine waters at the site have a high content of fluoride ions –significantly above the maximum permissible values.Lab-scale experiments were conducted to test various reagents and different initial concentrations of fluoride ions in the treatment ofmodel solutions and mine water. Depending on the initial concentrations, magnesium and calcium-containing sorbents are proposedfor the defluorization of water. Using scanning electron microscopy and microprobe analysis, it was found that fluorine can be boundin poorly soluble compounds, such as, for example, fluorite.Pilot trials are planned.