1439 In the reference state, mine water discharged from the facility is characterized by high salinity, resulting in substantial chloride and sulfate loads entering the receiving surface water body. Assuming an average discharge of 10,000 m³/day and a total dissolved solids concentration of 30–60 g/dm³, the annual salt load released into the environment is estimated at approximately 110,000–220,000 tonnes per year. In the transformation scenario, the application of nanofiltration (NF) and reverse osmosis (RO) technologies results in a 60–85% reduction in salt loads in the discharged effluent. This corresponds to a reduction of approximately 70,000–185,000 tonnes of salts per year. The treated permeate achieves a quality suitable for partial reuse as process or industrial water, thereby reducing abstraction from surface water resources. As a result, the salinity of discharged water is significantly reduced (to below 10–15 g/dm³ in the reference configuration), and the overall environmental pressure at the catchment scale is substantially mitigated. A comparative summary is presented in Table 2. Table 2 – Comparison of environmental impacts (before and after) Parameter Reference state (before) Transformation variant (after) Mine water flow 10,000 m³/day 10,000 m³/day Mean salinity 30 – 60 g/dm³ <10 – 15 g/dm³ Salt load into the receiver 110 – 220 thousand tons/year 25-90 thousand tons/year Salt load reduction - 60 – 85% Process water utilization None Partial In the reference configuration, mine water drainage, treatment, and discharge are fully supplied by electricity from the national grid. The annual energy demand of the water management system is estimated at 20–25 GWh, corresponding to indirect CO₂ emissions of approximately 10,000–12,000 tonnes per year. In the transformation scenario, integration of a 5–10 MWp photovoltaic (PV) installation enables the generation of approximately 5–10 GWh of electricity annually. This corresponds to 25–40% coverage of the system’s energy demand and reduces indirect CO₂ emissions by an estimated 4,000–7,000 tonnes per year. In addition to emission reductions, partial energy self-sufficiency decreases operating expenditures associated with electricity purchases from the external grid. A further improvement is achieved through the implementation of a methane capture and utilization module. In the reference state, methane emissions are only partially controlled and are not fully utilized for energy purposes. The assumed capture potential of 0.5–2.0 million m³ CH₄ per year enables its use in combined heat and power (CHP) systems or as process fuel. Methane utilization leads to: ● direct reduction of methane emissions to the atmosphere, ● generation of additional electricity and/or heat, ● increased stability of water supply, especially during periods of limited renewable energy production. From a system-wide perspective, the methane module functions as a dispatchable energy source that complements variable renewable generation and further improves the overall greenhouse gas (GHG) balance. Depending on the final energy configuration and the volume of methane captured, total GHG emission reductions are estimated at approximately 40–60% relative to the reference state. A comparative summary is presented in Table 3.
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