JPH01258791A - Waste water treating device for electrodeposition painting line - Google Patents

Abstract

PURPOSE:To inexpensively recover the waste water from a final rinsing tank of an electrodeposition painting line by separating the waste water from the final rinsing tank by a reverse osmosis membrane, supplying a concd. liquid to either of a 1st rinsing tank or 2nd rinsing tank and using the filtrate for rinsing the final rinsing tank. CONSTITUTION:The waste water from the final rinsing tank 10 having 0.05-0.2% solid content is guided to an adjusting tank 20 and is separated by a reverse osmosis membrane (e.g., polyamide membrane) module (e.g., spiral module) 22 under the pressure increased by a high-pressure pump 21 for circulation. The concd. liquid is supplied to either of the 1st rinsing tank 11 or the 2nd rinsing tank 12 and the filtrate is guided to a storage tank 23. The filtrate of the storage tank 23 is used as water of a rinsing shower 24. The waste water overflowing from the storage tank 23 is released as it is. As a result, the waste water from the final rinsing tank is recovered with the low equipment cost and small energy.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention is designed to treat wastewater from the final washing tank of an electrodeposition coating line! ! It is a device that pulls.

"Prior Art" Electrodeposition coating is widely used as a coating method for automobile bodies, parts, and household products. In particular, cationic electrolyte coating, which does not leave metal ions in the coating film, is used for undercoating automobile bodies.

In this equipment, the paint removed from the electrodeposition tank is separated using an ultrafiltration device in order to improve the coating rate of the electrodeposition paint and prevent pollution of the washing water. The concentrated liquid is returned to the electrodeposition tank, and the permeated liquid is supplied to the second washing tank. However, in the final pure water rinsing process, the paint is taken out from the second rinsing tank and the rinsing water from the rinsing tank always produces waste water with a solid content of about 0.1%. .

[Problems to be Solved by the Invention] This wastewater has a high concentration of BOD of 4000 m'J/e, so it cannot be discharged as it is, so it is treated after being discharged. As a method for treating wastewater, aerobic biological treatment and evaporation drying treatment using a drum dryer are carried out after coagulation and sedimentation. These methods have the disadvantage of large and expensive equipment and considerable energy consumption.

[Means for Solving the Problems] The present invention relates to an apparatus for recovering wastewater from a final flushing tank with low equipment costs and less energy.

The solid content in the wastewater from this final washing tank is O905%~
0.2%, BOD 2000-4000mg/l 4
However, since the concentration of BOD is low compared to the paint from the electrodeposition tank, it is expected that the removal rate of BOD will be low with the ultrafiltration membrane. It was not applied to wastewater treatment from the final washing tank. As for reverse osmosis membranes, it was thought that they would be unsuitable for wastewater treatment because a rapid drop in flux was expected. In fact, solids content 2
When 0.7% cadion type Dennuri is separated using the ultrafiltration module NTU2120 manufactured by Nitto Denko, the solid content is 0.
．． Only about 6% of permeated water was obtained.

"Function" Drainage from the final washing tank (10) with a solid content of 0.05% to 0.2% is led to the adjustment tank (20), and the high-pressure pump for circulation (
21) and increase the pressure for 21 minutes using the reverse osmosis membrane module (22).
I do. The concentrated liquid is supplied to the second washing tank (12), and the filtrate is led to the storage tank (23). ! ! The filtrate from the 7-reservoir tank is used as water for the washing machine (24). The wastewater that overflows from the storage tank will be discharged as is.

Types of reverse osmosis membranes include cellulose acetate membranes, polyamide-based membranes, polyvinyl alcohol-based membranes, and polycyclic (rimer-based membranes), but polyamide-based membranes are particularly excellent.As reverse osmosis membrane modules, spiral Any module may be used, such as a hollow module, a tubular module, a play 1~and frame module, or a pleated 7 joule module, but the spiral module is superior in terms of operability and economy.

When introducing the wastewater from the final washing tank (10) with a solid content of 0.05% to 0.2% to the adjustment tank (20), a feed, I! Even if air is injected through the air diffuser from llA, filtration with a low BOD can be achieved (q).

Before introducing the waste water from the adjustment tank to the circulation high-pressure pump, a microfilter or an ultrafiltration membrane module may be installed instead of the strainer.

"Example" [Final water replenishment washing of an electrodeposition coating line using 1 paint (cationic type electronic paint Power 1 to Tsubutu TJ-500 manufactured by... Boosted U/: After, Nitto Denko's spiral reverse osmosis membrane N
It was separated using TR-7197. Reverse osmosis membrane [Gile's population pressure 30'! , /lri, permeation rate of filtrate18. ON
, /Tl1-h are shown in Table 1.

In this process, after the painted Lean Pull was baked and dried, no peeling of the paint film occurred even when a top coat was applied.

The waste water from the same adjustment tank was separated using a spiral type ultrafiltration membrane module NTU-2120 manufactured by Nitto Denko <ti> using a pump. Inlet pressure of ultrafiltration membrane module 4 K3,
/ crA, filtrate permeation rate 76.34! Table 1 shows the results when operating at /bo/h.

``Effects of the Invention'' As described in section 1, by separating the waste water from the final washing tank using a reverse osmosis membrane, the BOD of the filtrate can be reduced to 10m3.
7f! Since it can be lowered to , it is possible to release WLJ as it is. A part of this filtrate can be used as washing water for the final washing tank, so it is possible to avoid reducing the amount of pure water used in the final washing tank. In this way, this device can contribute to reducing electrodeposition coating costs.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment 70 in which the wastewater treatment apparatus of the present invention is installed in a conventional electrodeposition coating line. 11 is a first washing tank, 12 is a second washing tank, 14 is an electrodeposition coating tank, 8 is a limit filtration device, 9 is a storage tank for the filtrate of the limit filtration, 10 is a final washing tank, and 20 is a drainage adjustment tank. , 2] is a high-pressure pump for circulation, 22 is a reverse osmosis filtration device, 23 is a filtrate storage tank, 24 is a flush shower with water for reprinting, 25 is a precision filter, 26 is discharge water, 27 is a pressure regulating valve, 2B is Flowmeter,
29 is the waste water from the final washing tank, 30G, which is washed with pure water.

Claims (1)

[Claims] The wastewater from the final washing tank (10) of the electrodeposition coating line is separated by a reverse osmosis membrane, and the concentrated liquid is supplied to either the first washing tank (11) or the second washing tank (12), where it is filtered. A device that supplies liquid as a final flush to the final flush tank.