1 Analysis of aluminum waste water. The production process of aluminum profiles mainly includes degreasing, alkali etching, pickling, oxidation, sealing and coloring of the formed aluminum profiles. The profiles after the above-mentioned T-sequence treatment need to be cleaned with water. The cleaning water is discharged from the cleaning tank in the form of overflow, which is the main source of wastewater from the aluminum profile factory. In addition to the aluminum ions in the aluminum profile factory, the production wastewater also contains some metal ions such as zinc, nickel, and copper. The pH of the wastewater varies depending on the production requirements, but most of it is acidic.
For the characteristics of aluminum profile wastewater mainly containing various metal ions and suspended solids, the process of neutralization adjustment and coagulation sedimentation is adopted. The aluminum profile production wastewater is discharged from the workshop and flows into the neutralization adjustment tank. The tank is equipped with air stirring to balance the water quality. After the wastewater is balanced in the water quality and water in the adjustment tank, alkali is added to adjust the pH value to 6-9, and then pumped into the sedimentation tank, and the flocculant (PAM) is added during the pumping process. After the metal ions in the wastewater react with alkali to form hydroxides, under the action of the flocculant, larger particles of alum bloom are formed; under the action of gravity, the upper half of the clear liquid can be directly discharged outside. The sludge in the sedimentation tank is concentrated in the sludge tank and pumped into the plate and frame filter press for dewatering and then used for sanitary landfill or comprehensive utilization.
3 process principle
3.1 Regulating pool
In the treatment of aluminum profile wastewater, the tank type of the adjustment tank is divided into two types: intermittent and continuous. When manual adjustment, the adjustment tank needs to be divided into two cells. The residence time of each cell is 1~2 hs in turn for intermittent use. Manual adjustment; automatic adjustment requires only one adjustment tank. V Use an automatic pH meter to control the pH value of the wastewater. Since the wastewater from aluminum profiles contains large amounts of aluminum, the aluminum is in an amphoteric state in the solution. When pH<3, the main form of aluminum is Al(H20)3+63. When pH=7, aluminum hydroxide becomes the main form of A13+. 5 When pH≥>8.5, most of the aluminum hydroxide is hydrolyzed into bands. Negatively charged complex anion. Therefore, the pH value must be controlled in an appropriate range during engineering commissioning so that aluminum can fully precipitate in the form of aluminum hydroxide.
3.2 Reaction cell
The function of the reaction tank is mainly to make the A13+ and OH- in the aluminum profile wastewater fully react to form insoluble Al(OH)3 precipitation.Usually vertical flow sedimentation tanks use vortex reactors, and advection sedimentation tanks use baffle reactors. .
3.3 Coagulation sedimentation tank
After the metal ions in the wastewater react with the alkali in the conditioning tank, insoluble hydroxides are formed, but because the formed particles are small, they are not easy to settle under the action of water flow, so polyacrylamide flocculant must be added to make these particles stick to each other Agglomerate into larger particles, which are removed by solid-liquid separation in the sedimentation tank. ○The sedimentation tank adopts advection or vertical flow, especially the latter is most widely used. Vertical flow sedimentation tank is particularly suitable for floc settlement, and is simple to operate, easy to manage, and the supernatant can be drained directly. The retention time of the sedimentation tank is 2h, and the surface load is 1m3/(m2-h).
3.4 Polyacrylamide for aluminum wastewater, sludge treatment, the aluminum profile sludge that is also discharged after precipitation has a moisture content of more than 90% and needs to be dehydrated. According to the factory's production capacity and sewage scale, two methods of natural drying and mechanical dehydration are selected to treat the sludge.
Natural drying is the use of drying to also contain sludge and use the sun to dry it. The advantages of this method are labor saving and economical, but it is only suitable for small enterprises in the sludge, and it is very troublesome in rainy weather; mechanical dewatering includes the use of centrifuges, belt filter presses, plate and frame filter presses. However, due to the loose structure of aluminum sludge and its corrosiveness, only the plate and frame filter press has the best effect. Therefore, in the engineering design, the sludge is discharged from the sedimentation tank to the sludge thickening tank by static pressure. After being concentrated, it is pumped to the pressure source of the plate and frame filter. After treatment, the water content of the sludge can be reduced to about 70%, and the sludge can be transported or comprehensively utilized.