Irrigation with Coal Mining Effluents: Sustainability and Water Quality Considerations (São Pedro da Cova, North Portugal)

Abstract

Two water effluents that drain from the abandoned coal mine of São Pedro da Cova (NW Portugal) were characterized in terms of their physic-chemical properties and suitability for irrigation purposes. Samples were also collected in a local surface stream, upstream and downstream from the mine drainage points, also used for irrigation by local farmers. Water samples were analyzed for major and minor ions and for trace element concentrations. Sampling campaigns started in 2017 and ended in 2019 and there were 46 water quality parameters tested. There were also proposed all-inclusive indices (the Water Quality Index and the Contamination Index, and also the Trace Element Toxicity Index) based on specific groups of 18 and 17 physic-chemical parameters, respectively, to achieve adequate monitoring requirements for mine effluents and surface water from coalfield. From the physical and chemical aspects of mine water it is inferred that the mine is not producing acid mine drainage. The coal mine water is of medium to high salinity, having almost neutral pH and a high thermal stability during the year, which is a distinguishing feature of the effluents. When compared to international irrigation water quality standards, as Food and Agriculture Organization of the United Nations admissible concentrations, the impacted waters are unsuitable for irrigation. The major outliers to the guidelines were iron, manganese, potassium, magnesium and bicarbonates, being also detected carcinogenic polycyclic aromatic hydrocarbons. Cost-effective ways of monitoring water quality parameters are needed to help control and manage the impact of coal mine effluents that should be treated before releasing into a ditch system that could be then used by local farmers to irrigate their crops.

Assessment of water resources for water irrigation purposes in Bintan island

“…Concentration of sodium (Na + ), calcium (Ca 2+ ), and magnesium (Mg 2+ ) is expressed in meq.L -1 . The categories of SAR shows in Table 3 [16,17]:…”

Research Review of Coal Mine Water Treatment Technology

“…The results show that ceramic ultrafiltration membranes have a strong tolerance to shocks, this feature allowed the treatment system can operate smoothly through complex working conditions. In 2021, Catarina Mansilha et al [12] characterized the physicochemical properties and suitability of abandoned coal mine discharge water for irrigation. Samples were collected in a local surface stream, which was analyzed for major and minor ions and trace element concentrations.…”

Effects of Magmatic Fluids in Coals of São Pedro da Cova Coalfield, Douro Carboniferous Basin, Portugal: Insights from Inorganic Geochemistry

“…The São Pedro da Cova Coalfield is part of the Douro Carboniferous Basin (DCB), the most important coal-bearing basin in Portugal, and has been, since the early 1990s, the focus of several geological studies with emphasis on tectono-stratigraphic development, e.g., [1][2][3][4][5], paleobotany, e.g., [6][7][8][9][10][11][12], paleozoology, e.g., [6,7,[13][14][15][16], organic petrology and physical parameters of the coals, e.g., [17][18][19][20][21][22][23][24][25], and coal exploration and its environmental impacts (e.g., [26][27][28][29][30][31][32][33][34][35][36]).…”