The acidic wastewater produced by aluminum extrusion profiles mainly comes from the acid etching process, neutralization, oxidation process in the oxidation workshop, spraying pretreatment degreasing, pickling and other processes in the aluminum profile manufacturer, which are rich in various harmful substances or heavy metal salts.
The mass fraction of acid is different, the low is less than 1%, and the high is more than 10%. Alkaline wastewater mainly comes from processes such as alkaline corrosion in oxidation workshops, spraying pretreatment, and alkaline washing. The mass fraction of alkali is higher than 5%, and some is lower than 1%. Wastewater also occurs in spraying and dyeing. In addition to being rich in acid and alkali, wastewater is often rich in grease, paint, fluoride salts and other inorganic and organic substances.
Acid-base wastewater is highly corrosive and requires proper management before it can be discharged.
1. For high-concentration acid-base wastewater, priority should be given to recycling and reuse. According to the water quality, water quantity and different technical requirements, try to reuse it as much as possible: if it is difficult to reuse, or the concentration is low and the water volume is large, the method of concentration can be used to recover the acid. alkali.
2. Low-concentration acid-base wastewater, such as cleaning water in pickling tanks, and rinsing water in alkaline cleaning tanks, should be neutralized.
Regarding neutralization disposal, the principle of treating waste with waste should be considered first. For example, the aluminum extrusion profile manufacturers neutralize the alkali wastewater with each other or use waste alkali (slag) to neutralize the acidic wastewater, and use the waste acid to neutralize the alkaline wastewater. In the absence of these conditions, neutralizing agents can be used.
It is mainly divided into three categories: physical disposal method, chemical disposal method and biological disposal method.
1. Physical disposal method is a wastewater disposal method that separates and recovers insoluble suspended pollutants (including oil films and oil beads) in the wastewater through physical effects.
Generally, methods such as sedimentation, filtration, centrifugal separation, air flotation, transpiration crystallization, and reverse osmosis are used. The pollutants such as suspended solids, colloids and oils in the wastewater are separated out, so that the wastewater can be purified.
2. Chemical treatment method is a wastewater treatment method that separates and removes dissolved and colloidal pollutants in wastewater or converts them into harmless substances through chemical reactions and mass transfer effects.
The general selection methods are: neutralization, coagulation, oxidative restoration, extraction, stripping, stripping, adsorption, ion exchange, and electro-infiltration.
3. Biological disposal method is a wastewater disposal method that converts waste water solution, colloid, organic matter, toxic substances and other pollutants in fine suspension into stable and harmless substances through the metabolic effect of microorganisms.
Biological disposal methods are further divided into aerobic disposal and anaerobic disposal. The aerobic disposal methods currently commonly used include activated sludge method, biological filter and oxidation pond. Anaerobic disposal method, also known as biological recovery disposal method, is mainly used to dispose of high-concentration organic wastewater and sludge, and use disposal equipment, mainly digester and so on.
The intent of sludge disposal is to:
① Reduce the moisture content of sludge and create conditions for the disposal, use and transportation of sludge.
② Eliminate harmful substances that pollute the environment.
③ Recover power and capital, and turn harm into profit.