Abstract
This paper presents the results of the technological and economic analysis of mine water treatment systems before their discharge into the environment. The following analysis enabled us to determine the profitability of the investment, taking into account the TSS (total suspended solids) concentration in mine water. The simulation results showed that it is economically profitable to apply a water treatment system if natural sedimentation carried out in underground mine water passages, or in sedimentation tanks located on the ground, is ineffective for TSS removal. Economic and financial parameters allow us to conclude that all analyzed variants of the application of a pre-treatment system are characterized by high economic effectiveness. This mainly results from the high profitability of an analyzed investment, comparatively low capital expenditure, and present low market percentage rates. The most profitable variant (TSS concentration is 1000 mg/dm3) brings significant economic indicators, i.e., high NPV–Net Present Value (100 319 270.28 PLN), a high NPVR–Net Present Value Ratio (8.96 PLN/PLN), and a short discount payback period (1 year 236.6 days). A high internal rate of return (157.8%) for this variant reduces the risk of losing profitability in a situation of growing capital costs in the monetary market.
Highlights
The exploitation of hard coal and the resumption of the abandoned coal mines are connected with the compulsory drainage of underground aquifers and the disposal of mine water into the environment, causing a serious hazard to the ecosystem
Mine waters are characterized by high salinity, suspended solids, and sometimes, the presence of heavy metals and radioactive isotopes
Coal mines systems monitoring the quantity and quality of drainage water are limited to monitoring the concentrations of chloride and sulphate ions and total suspended solids (TSS)
Summary
The exploitation of hard coal and the resumption of the abandoned coal mines are connected with the compulsory drainage of underground aquifers and the disposal of mine water into the environment, causing a serious hazard to the ecosystem. In most hard coal mines, the removal of total suspended solids from underground water pumped onto the mine surface is carried out in sedimentation ponds These ponds are usually designed for a 2-day hydraulic retention time (HRT). According to the current regulatory requirement (regulation of the Minister of the Environment on 18th November 2014 regarding the conditions that must be met during the discharge of waste into water or ground), the total suspended solids (TSS) concentration in water discharged to the environment should not exceed 35 mg/dm3 If this value was exceeded, the mines would be charged by increased environmental fees. In this article, based on the assumed hard coal mine exploitation data, the cost of operation and construction of TSS removal treatment installation in relation to the cost of mine water discharge directly into the environment were analyzed This analysis does not concern other types of contamination
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