JP5277419B1 - Wastewater recycling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drainage recycling system that can be reused without discharging the drainage into a river or the like.
The reverse osmosis membrane device 9 is separated into concentrated water containing metal ions and the like and water not containing them. The water quality of the water separated by the reverse osmosis membrane device 9 is pH: 6.5 to 7.5, chlorine concentration: 15 ppm or less, conductivity: 110 μs / cm or less, COD: 13.3 ppm or less, and industrial water Water quality level. For this reason, the water separated by the reverse osmosis membrane device 9 is sent to the pure water device 10 where it is mixed with new industrial water and used for pre-coating water washing and electrodeposition water washing.
[Selection] Figure 1

Description

  The present invention relates to a drainage recycling system that purifies and reuses drainage generated in a painting process or the like.

  FIG. 3 is a diagram showing the overall configuration of the current paint drainage treatment system. In the current system, industrial water (pH: 6.5 to 7.5, chlorine: 15 ppm or less, conductivity: 110 μs / cm or less, Part of COD: 13.3 ppm or less) is sent to the cooling tower and the paint circulation tank, and the remaining industrial water is sent to the pure water device.

The water treated with this pure water device is used for pre-treatment water washing and electrodeposition water washing.
The water used for this pretreatment washing and electrodeposition washing is stocked in a paint drainage tank, pH is adjusted using hydrochloric acid and caustic soda, and then metal is adsorbed using calcium chloride and a polymer flocculant. The sludge is divided into sludge and concentrated water. The sludge is treated for industrial waste and concentrated water is returned to the stock tank.

  Further, the supernatant of the metal adsorbed is adjusted again with hydrochloric acid and caustic soda and then sent to a transfer tank. The chlorine concentration of the water sent to this transfer tank is 2000-2500 ppm, the conductivity is 1000-5000 μs / cm, and the COD is 100-150 ppm, so that it cannot be discharged into the river as it is. For this reason, bio-treatment, chemical treatment, precipitation treatment, etc. are performed at dedicated facilities and the final water quality is kept below a certain standard and released into rivers.

  In the above-mentioned current treatment system, the waste water is purified before it can be discharged into the river and then discharged. Not only does this purification cost a lot, it also wastes valuable water resources without recycling them.

  Therefore, Patent Document 1 has been proposed as a reusable system. This patent document 1 discloses a wastewater reuse management system that adjusts the pH of clarified water that has been separated by a sedimentation device from the wastewater generated by the surface treatment, and converts the pH-adjusted water into a numerical value corresponding to each tank. As described above, it is disclosed that pH adjusted water is supplied at about pH 8.5 to 10.5 for washing after the alkaline degreasing tank, and is supplied at about pH 4 to 7 for washing after the acid treatment tank.

JP 2002-129398 A

  In the system proposed in Patent Document 1 described above, the main treatment is pH adjustment, and the chlorine concentration, conductivity, and COD values remain unsuitable for reuse only by this adjustment. Therefore, it is necessary to further improve the water quality by performing bio-treatment and the like, resulting in an increase in cost.

  In order to solve the above problems, a drainage recycling system according to the present invention includes a drainage stock tank that stocks drainage, a first chemical treatment unit that adjusts the pH of the wastewater from the drainage stock tank, and the first chemical treatment unit. The metal adsorbing part that adsorbs the metal in the wastewater whose pH is adjusted in step 2, the second chemical treatment part that adjusts the pH of the supernatant of the metal adsorption part, and the wastewater whose pH is adjusted in the second chemical treatment part A reverse osmosis membrane device for separating the concentrated water into water for reuse and a drying device for separating the concentrated water into steam and sludge cake.

  In addition to the above, the drainage recycling system according to the present invention can be provided, for example, with a transfer tank to the coating circulation tank downstream of the second chemical treatment section, or a filter section using a filter or activated carbon. It is.

  In addition, the water separated by the reverse osmosis membrane device is sent to the deionized water device in the same way as the current system, and is used as washing liquid for pre-coating water washing and electrodeposition water washing. Sent.

  The drying device preferably includes, for example, a disk that rotates in a high temperature state, a nozzle that sprays the concentrated water onto the disk, and a scraper that scrapes off the sludge adhering to the surface of the disk.

  Furthermore, the chlorine concentration can be reduced by replacing the oxidizing agent added in the first and second chemical treatment sections from hydrochloric acid to dilute sulfuric acid, and replacing calcium chloride used in the metal adsorption section with slaked lime.

According to the drainage recycling system of the present invention, the chlorine concentration, conductivity, and COD (chemical oxygen demand) are brought to the water quality level of industrial water while maintaining the pH within a predetermined range without incurring a large cost. be able to. Therefore, since it can be reused as it is, it is not discharged into the river, which is preferable in terms of cost and environmental sanitation.

In the drainage recycling system according to the present invention, since wastewater / drainage is not discharged outside the factory, it is possible to design the final treatment equipment (coagulation sedimentation tank, biological treatment tank, etc.) compactly, It is also possible to greatly reduce the capital investment. In addition, it is possible to reduce operating costs such as power and chemicals at the final processing facility.

In this recycling system, it is possible to treat high concentration drainage (block isocyanate) of electrodeposition coating that is cured by pH zone and heating temperature without requiring special pretreatment. Processing was performed by mixing the polymer flocculant in a coagulation sedimentation tank or its biological treatment tank little by little, but this recycling facility can improve the processing cost and work efficiency of these.

Overall configuration diagram of drainage recycling system according to the present invention Overall view of a drying apparatus that is a part of the drainage recycling system according to the present invention. Overall configuration diagram of conventional drainage treatment system

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the illustrated example, the paint drainage is recycled as an example, but the drainage is not limited to the paint drainage.

  The drainage recycling system according to the present invention includes a drainage stock tank 1 for stocking paint drainage used for cleaning in a painting process. A first chemical treatment unit 2, a metal adsorption unit 3 and a second chemical treatment unit 4 are arranged downstream of the waste water stock tank 1 as primary treatment units for adjusting pH, removing SS, removing heavy metals, removing fluorine and removing oil. ing.

  In the first chemical treatment unit 2 and the second chemical treatment unit 4, dilute sulfuric acid or caustic soda is used as an agent for adjusting the pH. Conventionally, hydrochloric acid is used instead of dilute sulfuric acid, but dilute sulfuric acid is used to lower the chlorine concentration.

The metal adsorbing unit 3 adsorbs and precipitates heavy metals using slaked lime and a polymer flocculant. Conventionally, calcium chloride is used instead of slaked lime, but slaked lime is used to lower the chlorine concentration.
Concentrated water containing heavy metals and the like is sent to a CD dryer 11 described later, and the supernatant is sent to the second chemical treatment unit 4 to adjust the pH again.

  The water exiting the second chemical treatment unit 4 is transferred to a transfer tank 5 (relay tank), a part of the water in the transfer tank 5 is sent to a painting circulation tank, and the rest is a secondary that performs COD reduction and chlorine reduction. It is sent to the processing unit. The secondary processing unit includes a first filter 6, an activated carbon layer 7, a second filter 8, and a reverse osmosis membrane device 9 (RO device). The activated carbon layer 7 mainly reduces COD, and the reverse osmosis membrane device 9 mainly reduces chlorine.

  Since the treated water generated from the CD dryer can be recovered with a quality close to that of pure water, it can be recycled without an RO (reverse osmosis membrane) device when used at an industrial water level.

  The reverse osmosis membrane device 9 is separated into concentrated water containing metal ions and the like and water not containing them. The water quality of the water separated by the reverse osmosis membrane device 9 is pH: 6.5 to 7.5, chlorine concentration: 15 ppm or less, conductivity: 110 μs / cm or less, COD: 13.3 ppm or less, and industrial water Water quality level. For this reason, the water which does not contain heavy metals separated by the reverse osmosis membrane device 9 is sent to the pure water device 10, where it is mixed with new industrial water and used for pre-coating water washing and electrodeposition water washing. In pre-treatment water washing, degreasing water and chemical conversion water washing are performed, and in electrodeposition water washing, dip water washing and post-water washing are performed.

On the other hand, the concentrated water from the reverse osmosis membrane device 9 is sent to the CD dryer 11. In this embodiment, a CD dryer is used as a drying device.
As shown in FIG. 2, the CD dryer includes a rotating disk 12, a nozzle 13 that sprays the concentrated water onto the disk 12, and a scraper 14 that scrapes off the sludge adhering to the surface of the disk 12.

  A circulation tank 15 with a weight scale is disposed below the rotary disk 12, and the concentrated water is fed into the circulation tank 15. The concentrated liquid in the circulation tank 15 is sent to the nozzle 13 by a circulation pump 16.

Further, high temperature steam is blown onto the surface of the disk 12, and the surface of the disk 12 is heated to about 120 ° C. When the scale of the CD dryer is large, it is possible to recycle steam, which is a heat source, by installing a steam recycling system, and energy costs and CO ₂ can be reduced. Therefore, the concentrated water sprayed on the disk 12 is dried and adheres to the disk surface. This deposit (sludge) is scraped off by the scraper 14 and sent to the paint soot treating apparatus.

  Further, steam generated by heating the concentrated water is collected by the hood 17 and a part thereof is discharged to the outside through the odor countermeasure shield 18, and the remaining steam is separated from the mist in the mist separator 19. 13 is sent in the middle.

  Moreover, the vapor | steam which exited the mist separator 19 is condensed with the condenser 20, and is collect | recovered as condensed water, and the remaining vapor | steam is discharge | released from an exhaust fan.

In this way, industrial water taken into the system, but some in the cycle is lost becomes steam, since part of the remaining industrial water and the level that is newly added hardly changes, circulation Used and never discharged into rivers.

  For this reason, the environmental load can be reduced. The solid matter discharged from this recycling system treatment contains a lot of paint and synthetic resin discharged from the coating factory, and the waste oil treated in the same way is also thermally recycled as a fuel with a high calorie and a very low moisture content. Is possible.

The drainage recycling system according to the present invention can be applied not only to coating drainage but also to drainage generated in a factory.

  DESCRIPTION OF SYMBOLS 1 ... Waste water stock tank, 2 ... 1st chemical | medical agent processing part, 3 ... Metal adsorption part, 4 ... 2nd chemical | medical agent processing part, 5 ... Transfer tank, 6 ... 1st filter, 7 ... Activated carbon layer, 8 ... 2nd filter, DESCRIPTION OF SYMBOLS 9 ... Reverse osmosis membrane apparatus, 10 ... Pure water apparatus, 11 ... CD dryer, 12 ... Rotary disk, 13 ... Nozzle, 14 ... Scraper, 15 ... Circulation tank, 16 ... Circulation pump, 17 ... Hood, 18 ... Odor countermeasure shield , 19 ... Mist separator, 20 ... Condenser.

Claims (3)

Waste water stock tank for stocking waste water, first chemical treatment section for adjusting pH of waste water from this waste water stock tank, and metal adsorption section for adsorbing metal in waste water whose pH is adjusted by this first chemical treatment section A second chemical treatment unit that adjusts the pH of the supernatant of the metal adsorbing unit, and a reverse osmosis membrane that separates the wastewater adjusted in pH by the second chemical treatment unit into concentrated water and water for reuse And a drying device for separating the concentrated water into steam and sludge, and a hood for collecting steam generated by heating the concentrated water is provided above the drying device, and collected by this hood. A part of the steam is discharged to the outside through the odor countermeasure shield, the remaining steam is separated into mist by a mist separator, the separated mist is sent again to the drying device, and the steam exiting the mist separator is condensed. Drainage recycling system, characterized in that in is condensed and recovered. 2. The drainage recycling system according to claim 1, wherein the drying device includes a disk that rotates in a high temperature state, a nozzle that sprays the concentrated water onto the disk, and a scraper that scrapes off the sludge adhering to the surface of the disk. A drainage recycling system characterized by this. 3. The drainage recycling system according to claim 1 or 2, wherein dilute sulfuric acid is used as an oxidizing agent in the first and second chemical treatment sections, and slaked lime is used in the metal adsorption section. .

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