Pit water, mine water or mining water is water that collects in a mine and which has to be brought to the surface by water management methods in order to enable the mine to continue working. It can be divided into five types: pure pit water, pit water containing suspended solids, highly mineralized pit water, acidic pit water, and special polluted mine water. It has the characteristics of groundwater, but due to artificial pollution, it also shares some characteristics of surface water.

Many countries treat pit water appropriately, and part of it reaches the discharge standard and is discharged into the surface water system, while the rest is reused as industrial water for ore processing (coal preparation) plants and mine water.

Ultrafiltration (UF), Nanofiltration (NF) and Reverse Osmosis (RO) have already demonstrated the ability to produce clean permeate for water reuse and a retentate stream for further downstream processing.

Typical STRO/DTRO Process for Treatment of Coal Mining Pit Wastewater and Coal-washing Wastewater