1. Acid-Alkaline Wastewater
Main Characteristics:
Acidic wastewater primarily originates from industries such as steel plants, chemical plants, dye factories, electroplating facilities, and mines. It contains various harmful substances or heavy metal salts, with the mass fraction of acid varying significantly-it can be less than 1% or exceed 10%.
Alkaline wastewater mainly comes from printing and dyeing mills, tanneries, paper mills, and oil refineries, containing either organic or inorganic alkalis. The alkali content ranges from below 1% to over 5%.
Besides acids and alkalis, this type of wastewater also contains acid salts, basic salts, and other inorganic and organic pollutants, exhibiting strong corrosiveness.
Treatment Methods:
High-concentration acid-alkaline wastewater should be prioritized for recovery and reuse. Low-concentration wastewater, such as rinse water from pickling or alkali washing tanks, requires neutralization treatment. The principle of "waste control by waste" should be applied first-for instance, neutralizing acidic and alkaline wastewater against each other, or using waste alkali (slag) to treat acidic wastewater and waste acid to treat alkaline wastewater. If such options are unavailable, neutralizing agents should be used.
2. Mineral Processing Wastewater
Main Characteristics:
Mineral processing wastewater is characterized by large volumes and high suspended solids content. It contains numerous heavy metal ions (such as copper, zinc, lead, nickel, barium, cadmium, arsenic) and beneficiation reagents, resulting in a complex composition with various harmful substances.
Treatment Methods:
Heavy metal ions can be removed using the lime neutralization method or roasted dolomite adsorption. For flotation reagents, ore adsorption or activated carbon adsorption methods can be employed. Cyanide-containing wastewater is suitable for treatment by chemical oxidation.