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Treatment process of aluminum profile wastewater

Treatment process of aluminum profile wastewater

  • Categories:Industry News
  • Author:
  • Origin:
  • Time of issue:2018-12-06
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(Summary description)Aluminum profile wastewater treatment process is simple, easy to operate and manage, and suitable for other metal wastewater,

Treatment process of aluminum profile wastewater

(Summary description)Aluminum profile wastewater treatment process is simple, easy to operate and manage, and suitable for other metal wastewater,

  • Categories:Industry News
  • Author:
  • Origin:
  • Time of issue:2018-12-06 16:37
  • Views:
Information

The aluminum profile production process mainly includes degreasing, alkali etching, pickling, oxidation, sealing and coloring of the formed aluminum material, and the profiles processed by the above processes are all washed with water, and the profile cleaning water is discharged as an overflow. The cleaning tank is the main source of wastewater from the aluminum profile plant. In addition to containing a large amount of aluminum ions, the aluminum profile 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 it is mostly acidic. Table 1 Aluminum profile wastewater quality table item pH suspension (mg / L) copper (mg / L) zinc (mg / L) nickel (mg / L) concentration 2 ~ 4300 ~ 10000.5 ~ 31.5 ~ 41.5 ~ 4

2 Wastewater treatment process

The aluminum profile wastewater mainly contains various metal ions and suspended solids, and adopts a neutralization adjustment and a coagulation sedimentation process. The aluminum profile production wastewater is discharged from the workshop and flows into the neutralization adjustment tank. The pool is equipped with air agitation to balance the water quality. After the wastewater is adjusted to balance the water quality and the amount of water, the alkali is added to adjust the pH to 6-9, and then pumped into the sedimentation tank, and a flocculant (PAM) is added simultaneously in the pumping process. The metal ions in the wastewater react with the alkali to form a hydroxide, and under the action of the flocculant, a large particle sputum is formed, which rapidly settles under the action of gravity. The upper part of the sedimentation tank can be directly discharged, and the effluent water quality It has reached the second-level emission standard of the second-class area of ​​Guangdong Province local discharge standard DB4426-89.

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

3 process principle

3.1 adjustment pool

In the treatment of aluminum profile wastewater, the pool type of the adjustment tank is divided into two types: intermittent and continuous. In the manual adjustment, the adjustment tank should be divided into two compartments. The residence time of the wastewater in each grid is 1~2h, which is used intermittently to facilitate manual adjustment. The automatic adjustment requires only one adjustment tank, and the pH of the wastewater is controlled by the pH automatic regulator. Value, because aluminum profile wastewater contains a large amount of aluminum, and aluminum is in a bisexual 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 band. Negatively charged complex anion. Therefore, the pH must be controlled within an appropriate range during engineering commissioning so that aluminum can be sufficiently precipitated in the form of aluminum hydroxide.

3.2 reaction pool

The role of the reaction cell is mainly to fully react Al3+ and OH- in the aluminum profile wastewater to form a poorly soluble Al(OH)3 precipitate. Usually, the vertical flow type sedimentation tank uses a vortex reactor, and the flat flow type sedimentation tank uses a baffled reactor.

3.3 Coagulation sedimentation tank

The metal ions in the wastewater react with the alkali to form insoluble hydroxides. However, since the formed particles are small, they are not easy to settle under the action of water flow. Therefore, flocculants must be added to bond the particles to each other and aggregate. Larger particles are removed by solid-liquid separation in the sedimentation tank. The sedimentation tank is of the advection or vertical flow type, especially the latter. The vertical flow sedimentation tank is especially suitable for flocculation sedimentation, and the operation is simple, easy to manage, and the supernatant liquid can be directly discharged. The residence time of the sedimentation tank was 2 h, and the surface load was 1 m3/(m2?h).

3.4 sludge treatment

The aluminum profile sludge discharged through the sedimentation tank has a moisture content of more than 90% and needs to be dehydrated. According to the production capacity of the factory and the scale of sewage discharge, the sludge is treated by two methods: natural drying and mechanical dehydration.

Natural drying is to use a drying tank to hold the sludge and use the sun to dry it. The advantage of this method is that it is economical and economical, but it is only suitable for enterprises with small amount of sludge, and it is very troublesome to encounter rainy weather; mechanical dewatering includes the use of centrifuges, belt filter presses, and plate and frame filter presses. However, due to the loose structure of the aluminum profile 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 by static pressure into the sludge concentration tank, and after being concentrated, it is pumped to the plate and frame filter press for pressure filtration. After treatment, the moisture content of the sludge can be reduced to about 70%, and the mud cake can be transported or comprehensively utilized.

3.5 key to debugging

in the debugging of aluminum profile wastewater treatment, the most important thing is to control the pH value of the wastewater to make various metal ions form insoluble hydroxides, so as to achieve the best removal effect. Table 2 The optimum pH value of various metal ions removal Metal ion pH range Residual concentration (mg/L) Remarks Aluminum 5.5~8≤3pH6.5 or more Redissolved copper 7~14≤1Zinc 9~10.5≤1pH10.5 Redissolved nickel>9≤1

From Table 2 and the debugging effect of a number of aluminum profile wastewater projects, for general aluminum profile wastewater, the pH value is controlled at 7.5-8.5 to obtain the best precipitation effect; for a certain metal ion wastewater, it needs The pH is adjusted according to the characteristics of the metal ion. 4 monitoring results and analysis

The aluminum profile wastewater treatment process has been put into operation in more than 90% of aluminum plants in Nanhai City. The equipment works well and the effluent water quality is stable. Table 3 shows the sampling results of some enterprises. Table 3 Aluminum profile plant wastewater monitoring results table unit water sample pH suspension (mg / L) copper (mg / L) zinc (mg / L) nickel (mg / L) Xingfa aluminum plant water into the water 1.8614540.550.242.12 Effluent 6.2920.80.020.020.08 Fengchi Wastewater Treatment Plant Inflow 9.9738040.400.511.70 Effluent 7.9412.80.040.000.26 Inlet Wastewater Plant Inlet Water 4.3429521.613.224.92 Effluent 7.137.20.040.150.26 Guangdong Emission Standard 6~9100121 Note above data Provided for the Nanhai Environmental Monitoring Station, the effluent implementation standard is Guangdong Province “Three Industrial Waste Emission Standards” DB4426-89.

5 summary

1 Engineering practice shows that the process is reasonable and feasible.

2 Due to the amphoteric state of aluminum in the solution, aluminum ions also act as a water purifier in the wastewater, and also contain a large amount of aluminum in various flocculants and coagulants added, so the water quality project after treatment There is no requirement for the concentration of aluminum.

3 Aluminum profile wastewater treatment process is simple, easy to operate and manage, and suitable for other metal wastewater, acid and alkali wastewater treatment. The current problem is the treatment of waste residue. After the aluminum sludge is dehydrated by the filter press, it still contains more hydroxide, which will cause secondary pollution. In fact, the precipitate of aluminum waste water contains a large amount of aluminum hydroxide. If it is developed and utilized, it can extract very pure aluminum hydroxide as a chemical raw material and has a wide range of uses.

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