International journal of mine water

Acid mine drainage (AMD) with a pH of 3.7–4.1 seeps from an abandoned sulphide mine in Smolnik, Slovakia at a flow rate of 5–10 L/s. Metals precipitate as the AMD mixes with the higher pH Smolnik Creek, adversely affecting the stream’s water quality and ecology. Multivariate statistics were used to interpret surface water and sediment quality effects. Factor analysis generated three significant factors that explained 79.9 % of the variance in the data: the pH is indirectly proportional to the concentration of dissolved metals; Fe precipitation is associated with a decrease in Al in the sediment; and increased Cu concentrations are associated with more Zn in the sediment. High rainfall events increase the flow of Smolnik Creek, which ranges from 0.3 to 2.0 m3/s (monitored 2000–2012). Increased flow is associated with a pH increase and precipitation of metals (Fe, Al, Cu, and Zn). The dependence of pH on flow in Smolnik Creek was evaluated using regression analysis, which confirmed the significance of the exponential relationship between pH and flow rate.

Acid mine water production as well as dissolution of several metals in the same are due to an important contribution from the activity of microorganisms. The dissolution and precipitation of the metals from acid mine water seem to be especially controlled also by oxyhydroxides of Fe/Mn. Interference of specific microorganisms can lead to dissolution and precipitation of specific metals. This ability of the microorganisms could be used to prevent pollution by acid mine water.

Although many approaches have been proposed for flood risk assessment in urban areas, an equivalent methodology for remote mine sites with poor hydrological data records is still needed. This paper provides a fuzzy methodology based on calculating the hydrological return period discharge and the resistance-load theory for embankment failure risk assessment of an existing drainage storage system (lake) at the Golgohar mine site. The uncertainty of the two uncertain components, load and resistance, were endowed with triangular fuzzy numbers (TFNs) describing possible values the two components may have. First, based on a comparison of two consecutive Sentinel-2A images and the model water volume, a new manual storm water management model (SWMM) calibration technique was introduced. Then, three well-known synthetic rainfall hyetograph generation methods based on a single point of the rainfall curve were input into the calibrated SWMM model. Second, the BRCH-J model was used to calculate the maximum water level in the lake if an embankment breach occurs in two scenarios, with an unprotected and a fully riprap-protected downstream face. Afterward, the SWMM and BRCH-J outputs were used to define the TFN parameters representing the load (surface flow) and resistance (lake capacity). Finally, on the basis that both TFNs must match, a fuzzy risk product with alpha-cut principles was defined, as was the difference between the TFNs representing the load and resistance. The result indicates that the available stormwater storage volume exceeded the expected capacity; the risk of embankment failure was 0.15%, which was less than the design risk (1%, based on the hydrological return period concept).

Uncontrolled release of thiosulfate can cause high oxygen demand, or generate toxic compounds under anaerobic scenarios. Biooxidation of thiosulfate in a biotrickling filter (BTF) colonized by an alkaliphilic sulfide-oxidizing bacterial consortium was studied at pH ≈10. Inlet thiosulfate concentrations were varied from 3.5 to 21.3 g L−1, with a residence time of 216 s, emulating conditions encountered in wastewater from mining processes. Sulfate production, oxygen concentration, and biomass in both packing and effluent were periodically analyzed to characterize bioreactor performance. Removal efficiencies near 100 % were obtained during the entire experimental period, with a maximum elimination capacity of 242 g thiosulfate m−3 h−1. Although the BTF was able to transfer large amounts of oxygen to biooxidize thiosulfate to sulfate, under high initial thiosulfate loads, thiosulfate was not completely oxidized to sulfate, since biooxidation was conditioned to oxygen supply. Respirometric tests performed to investigate biomass adaptation and activity revealed oxygen consumption values of 0.5 mmol O2 (g protein)−1 min−1 for the period with the highest thiosulfate inlet load.

To investigate the mechanism of water–sediment inrush during coal mining, the characteristics of water–sediment flow in rock fractures were quantitatively analyzed by computational fluid dynamics (CFD). Based on the two-phase flow theory, a resistance model of water–sediment flow in fractures was established and verified by a laboratory-scale test. The results showed that: (1) With increases sediment particle diameter, volume fraction, and initial water phase velocity, the resistance of sediment particles grows gradually. (2) The drag force of sediment particles is mainly generated from the collision of the water phase and fracture wall. The velocity distribution of sediment particles can be divided into three stages, i.e., continuous increase, rapid decrease, and slow fluctuation. (3) The numerical model was shown to have high predictive accuracy by comparison with the test results. The model’s predictive accuracy decreases with increased water phase velocity and decreases of the sediment particle diameter and volume fraction. (4) The smaller the fracture width, the larger the inclination and bending angles, and the greater the resistance of the two-phase flow in the fracture. Collisions between the particles and fracture wall cause velocity attenuation of the sediment particles. We propose water–sediment inrush prevention and control technology based on the numerical analysis results.

The co-treatment of AMD with other common liquid wastes is a promising synergistic approach, fusing characteristics of active and passive AMD treatment for a sustainable remediation strategy. This paper discusses existing literature on AMD co-treatment approaches, focusing on factors that influence the feasibility of co-treatment, such as mixing proportions, microbiological elements, reactor design, and mixed-water chemistry. Finally, this paper highlights future possibilities, drawing attention to prospects that require exploration.