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The influence of waters..

MINERALIZATION OF MINEWATERS

The mineralization of natural minewaters ranges from 0.2 to 372.6 g/m³ (Różkowski 1995; Różkowski, Rudzińska, 1983). M. Rogoż, M. Staszewski and Z. Wilk (1987) estimate that at the beginning of the 80s the amount of minewater from hard coal minę drainage amounted on average to 960,000 m³ per day which madę 11.1 m³/s in four minewater ąuality classes which differed in the content of Cl^- and SO ions (Table 3).

TABLE 3. Amount of water pumped out from mines of hard coal in the area of the Upper Silesian Coal Basin, in particular classes of water ąuality (after Rogoż, Staszewski and Wilk 1987)

Class	Content of Cl and SO 4~ ions kg/m^3	Amount of waters pumped out o thousand m per day	Percentage share
I	<0.6	427	45
II	0.6-1.8	232	24
III	1.8-42.0	278	29
IV	>42.0	23	2
To tal		960	100

Waters of Iow mineralization which belong to the first class originate from upper exploitation horizons (depths to 400 m) and are drinkable but those from the second class can be used only for industrial purposes. Waters of the third class (weakly salinę) which originate from excavations located lower down are only useful to a limited degree so are discharged to the surface hydrographic net. Part of them is utilized at the new station for desalination, located at the existing plant desalinating the "Dębieńsko" hard coal minę. A connected method of desalination is used here which consists in the increase in concentration of weakly salinę waters by reverse osmosis. This way about 13,300 m³ water per day can be utilized. Water of the fourth class (brine), where concentrations of chlorine-sulphate ions exceed 42 g/dm³, cannot be used for economic purposes and is also discharged to the hydrographical net. This brine can only undergo utilization at 2000 m³ per day by way of the thermal-chemical method at the "Dębieńsko" desalination plant in Czerwionka.

On the base of a prognosis for water inflow to the coal mines of the USCB up to 2005, worked out by Main Mining Institute (GIG) in Katowice, I. Węgrzynowska (1993) states that the amount of waters of III and IV classes will increase by 57%, while in class I it decreases by 11% and in II by 23%; the overall salt load discharged to rivers will increase by 28%.

So large an amount of minewater discharged to the surface and especially waters of increased mineralization, is not without influence on river water ąuality. The load of salt which is discharged from the mines to rivers of the