It is understood that environmental pollution problems have occurred to varying degrees around the world, including atmospheric pollution, marine pollution and urban environmental pollution. As we all know, the production process of aluminum profiles is also quite polluting to our environment, so how to deal with the wastewater of aluminum profiles?

First, the wastewater characteristics of aluminum profiles

The production process of aluminum profiles mainly includes: degreasing, alkali etching, pickling, oxidation, sealing and coloring of formed aluminum profiles, and the profiles treated by the above processes need to be cleaned with water, and the cleaning water of this part of profiles is discharged in the form of overflow. The cleaning tank is the main source of wastewater in the aluminum profile factory. In addition to a large amount of aluminum ions, the wastewater produced by aluminum profile manufacturers also contains some metal ions such as zinc, nickel and copper. The pH of the wastewater varies depending on the production requirements, and most of them are acidic.

2. Process flow of aluminum profile wastewater treatment

According to the characteristics of aluminum profile wastewater mainly containing various metal ions and suspended solids, the neutralization adjustment and coagulation sedimentation process are adopted.

The aluminum profile production wastewater is discharged from the workshop and flows into the neutralization adjustment tank, which is equipped with air agitation to balance the water quality. After the wastewater is adjusted in the tank to balance the water quality and quantity, the pH value is adjusted to 6-9 by adding alkali, and then pumped into the sedimentation tank with a pump, and a flocculant (PAM) is added during the pumping process. After the metal ions in the wastewater react with the alkali to form hydroxides, and under the action of the flocculant, they form larger particles of alum, which settle rapidly under the action of gravity. The clear liquid in the upper half of the sedimentation tank can be directly discharged. It has reached the second-level emission standard of the second-class area of the square emission standard DB 4426-89.

The sludge in the sedimentation tank is concentrated in the sludge tank and then pumped into the plate and frame filter press for dehydration for sanitary landfill or comprehensive utilization.

3. Process principle of aluminum profile wastewater treatment

1. Regulating pool: In the treatment of aluminum profile wastewater, the pool type of the regulating pool is divided into two types: intermittent and continuous. In manual adjustment, the adjustment tank needs to be divided into two compartments. The residence time of wastewater in each compartment is 1-2 h, and it is used intermittently in turn to facilitate manual adjustment; only one compartment is required for automatic adjustment, and the pH automatic regulator is used to control the wastewater. pH value, because aluminum extrusion wastewater contains a large amount of aluminum, and aluminum is in an amphoteric state in solution. When pH<3, the main form of aluminum is Al(H2O)3+6; when pH=7, aluminum hydroxide becomes the main form of Al3+; when pH>8.5, most of the aluminum hydroxide is hydrolyzed into a Negatively charged complex anion. Therefore, the pH value must be controlled in an appropriate range during engineering debugging, so that aluminum can be fully precipitated in the form of aluminum hydroxide.

2. Reaction pool: The main function of the reaction pool is to fully react Al3+ and OH- in the aluminum profile wastewater to form insoluble Al(OH)3 precipitation. Usually, the vertical flow sedimentation tank adopts a vortex reactor, and the horizontal flow sedimentation tank adopts a baffled flow reactor.

3. Coagulation sedimentation tank: After the metal ions in the wastewater react with alkali in the adjustment tank, insoluble hydroxides are formed, but because the particles formed are small, it is not easy to settle under the action of water flow, so a flocculant must be added to make the These particles are bonded to each other and aggregated into larger particles, which are removed by solid-liquid separation in the sedimentation tank. The sedimentation tank adopts horizontal flow or vertical flow, especially the latter is more widely used. The vertical flow sedimentation tank is especially suitable for floc sedimentation, and is simple to operate, easy to manage, and the supernatant can be directly discharged. The residence time of the sedimentation tank is 2h, and the surface load is 1m3/(m2•h).