Acid waste water mainly comes from iron and steel plants, chemical plants, dye plants, electroplating plants and mines, which contain various harmful substances or heavy metal salts. The mass fraction of acid is very different, the lower is less than 1%, the higher is more than 10%. Alkaline wastewater mainly comes from printing and dyeing plant, leather plant, paper mill, oil refinery, etc. Some of them contain organic alkali or inorganic alkali. The mass fraction of alkali is higher than 5% and lower than 1%. Acid and alkali waste water, in addition to containing acid and alkali, often contains acid salt, alkali salt and other inorganic and organic matters.

    Acid and alkali wastewater has strong corrosiveness and can be discharged only after proper treatment.

    The principle of treating acid and alkali wastewater is as follows:

    (1) High concentration acid and alkali wastewater should be recycled first. According to the water quality, water quantity and different process requirements, the plant or regional dispatching should be carried out to reuse as much as possible: if it is difficult to reuse, or the concentration is low, the water volume is large, the method of concentration can be used to recover acid and alkali.

    (2) Low concentration acid and alkali waste water, such as cleaning water of acid washing tank and rinsing water of alkali washing tank, shall be neutralized.

    For neutralization treatment, the principle of waste treatment should be considered first. For example, acid and alkali wastewater are neutralized with each other, or waste alkali (slag) is used to neutralize acid wastewater, and waste acid is used to neutralize alkaline wastewater. In the absence of these conditions, neutralizer treatment can be used