English to Polish Tech/Engineering Mining & Minerals / Gems Coal mining

Chodzi o rodzaj płynnych odpadów, które powstają w procesie oczyszczania węgla, podaję opis po angielsku - "liquid waste" to właśnie ów "sludge".

Before being transported to market, coal must be washed to separate it from the surrounding soil and rock--the more impurities a company can remove from coal, the higher its market value and the lesser the transportation costs. The washing process generates huge volumes of liquid waste, while the mining process generates millions of tons of solid waste. The cheapest way for coal companies deal with this some of this waste is by constructing dams from the solid mining refuse (that is, rocks and soil) to impound the liquid waste.