Characteristics of coal mine wastewater:  

1. High suspended solids and turbidity, with suspended solids mainly consisting of coal dust and rock debris; concentrations typically exceed 200 mg/L and can surpass 1,000 mg/L in extreme cases.

2. Coal mine wastewater includes various types such as mine water, coal preparation wastewater, and coal chemical industry wastewater.

3. The organic pollutants vary greatly; ordinary mine water contains 150–300 mg/L of organic matter, while the COD in coal chemical wastewater can reach several hundred to several thousand mg/L.

4. Contains heavy metal ions such as lead, cadmium, mercury, iron, and manganese.