JPS5855019A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To prevent a rise of pressure difference in filtration caused by a clogging of pores and to prevent a mixing of fine cruds at the resumption of operation, by precoating the inner surface of a porous tube filter with fine particles of ferrous oxides, etc. prior to the filtration, in a titled treatment of an atomic power station, etc. CONSTITUTION:Prior to the treatment of waste water containing cruds discharged from an atomic power station, etc. by a parallel flow filtering device 1 using porous tube-filters 6, fine particles of ferrous oxides, having particle size of >= the degree of pore size of the filter 6, are suspended in demineralized water, etc., and the treated water is supplied to a circulation tank 7 or sub-tank 10 to be transferred to an inlet chamber 3 by a pressure with the aid of a pump 8, then the fine particles are precoated on the inner surface of the filter 6 by circulating the suspension in the same condition as that of a normal operation. Next, waste water, flowing into the tank 7, is transferred by a pressure to the chamber 3 with the aid of the pump 8, and the treated water without cruds is filtered in a filtering tank 9 to be recovered to the outside, and the waste water with highly concentrated cruds, flowed out to a chamber 5, is returned to the tank 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating wastewater, particularly a method for treating wastewater using a parallel flow device using a porous portshape filter suitable for treating wastewater in nuclear power plants.

This parallel flow device is used to recover treated water that does not contain crud from the wastewater containing crud discharged from nuclear power plants, etc., and reuse it, as shown in Figure 1. At one end of the inside of the filtration side L, there is a partition plate, and at the other end there is an inlet chamber J1, and at the other end there is an exit chamber S, and each end of the plurality of tube fittings 4 is connected to each end of the partition plate J1. The OII water from a nuclear power plant, etc., which flows into a differential tank supported in communication with the inlet chamber JK, is passed through the inlet chamber JK by a circulation pump T, and the wastewater passes through each channel filter base to the outlet JK.
While flowing out, the water containing %A passes through the partition plate, the F water chamber between the sections, and is collected outside, and the content concentration of the crud that flowed out of the outlet chamber SK is The highly concentrated wastewater is returned to the circulation tank 7, and together with the wastewater that has newly flowed into the circulation tank, it is again forced into the inlet chamber 3 by the pump S, and the treated water is recovered by circulation.

The filtration pressure difference in the device is the inlet pressure value P1 indicated by the pressure gauge connected to the pipe to the inlet chamber 3, and the outlet pressure value P1 indicated by the pressure needle connected to the pipe from the outlet chamber j! It is expressed as the difference in the treated water pressure value P1 indicated by the pressure gauge connected to the pipe from the filtrate water chamber with respect to the average of .

Therefore, a large amount of treated water can be recovered when the filtration pressure difference ΔP is close to OK.
The inner surface of the filter has a filter bore (porous opening).
If this is the case, a cake layer is formed by large crud in the wastewater, and smaller crud is trapped in the gap between the two large plates forming the cake layer, or is trapped inside the bore. Since it prevents deep penetration, stable filtration is performed. In fact, if a filter with a bore of 0.177% is operating stably at 4. The cladding down to μS is almost completely removed. The flow rate of wastewater passing through the tube filter increases as it moves away from the inner surface of the filter, so when the cake layer grows and increases in thickness, its surface comes into contact with the high-speed flow of wastewater and is peeled off. Depending on the flow rate, the cake layer can maintain a predetermined constant thickness.

However, as the operating time passes, more and more fine crud is trapped in the gaps between the cruds in the cake layer, and as the cake layer becomes compacted, the differential pressure ΔP gradually increases, and the treated water Since the amount recovered is decreasing, it is necessary to backwash the cake layer to loosen it when the filtration differential pressure reaches a certain value or more.

This backwashing may be performed at regular intervals regardless of the rise in the f excess pressure ΔP. For backwashing, repeat the r-filtration process for several seconds, e.g.
After stopping for 0 seconds, filtered water, compressed air, or a gas-liquid mixture is supplied to the filtration chamber and passed through the tube filter in the opposite direction to the water flow direction during filtration.

Now, when I test run a brand new equipment, I still have a tank i.
°The cake layer is not formed due to O violation, and the re-formation is due to the bore diameter during the trial run! When passing wastewater containing a large amount of fine particles or rad, small crud will enter the pores, some of which will come out into the treated water and deteriorate the treated water quality. Because of the stones deposited in the bore, the filtration differential pressure rises rapidly, resulting in a phenomenon in which the expected amount of treated water cannot be recovered.

In general, clad particles in wastewater fluctuate rapidly, so in order to prevent this kind of phenomenon, it is necessary to pass wastewater that contains a large amount of fine cladding to the bore diameter, or to increase the bore diameter excessively. Unless it is made smaller to prevent the penetration of crud, it becomes a major constraint on the operation of the equipment.

The present invention investigates the above-mentioned phenomenon and develops a countermeasure against it, thereby making it possible to obtain treated water that does not contain fine particles or particles almost from the beginning of operation, thereby reducing wasted energy and improving the operating efficiency of the equipment. It is.

The above phenomenon occurs at the beginning of operation using a new tube filter, before the bore and PI@degree or even larger cladding forms an effective cake layer on the inner surface of the filter, small fine cladding forms in the bore. The main cause of this problem is that water enters the bore and clogs the bore, or leaks through the bore into the filtration ice chamber. For example, the bore diameter is Q,! If it is a μ cake, pre-coat the inner surface of the tube filter with 0.3μ bait or larger particles, and when the operation is started, this pre-coat will cause the fine crud to clog the bore with a layer of cake. By increasing the filtration differential pressure, preventing fine crud from entering the treated water, and performing steady operation from the beginning of operation, we were able to recover a large amount of high-quality treated water.

It is preferable that the fine particles for precoating form an incompressible cake layer and prevent themselves from becoming filtration resistance.For this purpose, F'5lo4.7
Iron oxides such as 1201, other metal oxides, and 0GO
It is preferable to use one or more of poorly soluble salts such as OB and B6EIO4, and organic polymer substances such as powdered resin. In addition, the particle size must be the same as or larger than the bore, and optimally it is 1 to 1 to the inner diameter of the bore.
It is 5 times more. Incidentally, the particles which are finer than the bore diameter are adjusted in advance to such an extent that they do not cause shadow change during pre-coating, for example, to a size of 5 or less.

In order to pre-coat, the above-mentioned fine particles are mixed with pure water or water from which BB (suspended solids) have been sufficiently removed. Suspend the suspension at a degree of immersion (preferably around 100 PI) l', add an appropriate dispersant if necessary, force this suspension to the inlet chamber 3 with a circulation pump j, and operate under the same conditions as steady operation. Yes.

The suspension of particles for pre-coating is placed in a circulation tank 7, or a small-capacity auxiliary tank 10 is provided in parallel with the circulation tank 7, and both tanks 7 and i are connected.

can be alternatively connected to the outlet chamber j and the circulation pump via valves Vs and vt, and the suspension is placed in this auxiliary tank IO and circulated. In either case, during the circulation of the suspension, the filtrate obtained in the filtrate water chamber should be returned to the tank 7 or IO. For the embodiments and effects of the present invention, refer to the diagram in Figure 2.3. The condition of the filtration differential pressure when all the bore 410.7 pm tube filters were replaced with new ones and wastewater containing about aoppm of crud containing about 7016 particles of 1 particle size o, jpm or less was passed for 200 hours was as follows. In the passage shown in Figure 2, a rapid rise in the transient differential pressure was observed 100 hours after the start of operation.

On the other hand, if the particle size is about 0.1-2.0 pm or less, the total α-1-! 01 in pure water with 100 ppm f
I Suspended at 11 degrees and added tripolyphosphoric acid O, S as a dispersant.
cs was added and the suspension was circulated for 5 minutes under the same operating conditions.
Iron oxide was precoated on the inner surface of each new tube filter.

Next, water was passed through the same folding liquid under the same conditions for 500 hours.

The filtration differential pressure at this time was constant as shown in B in Figure 2, which was constant from the beginning of the wastewater operation, and as shown in Figure 3B, the yield of treated water was also constant. Since no crud was detected in the treated water from the beginning of the wastewater operation, it was possible to reuse it immediately.

In addition, in both cases, the filtration area of the tube filter is 1 hourly.
The filtration process was stopped and backwashing was performed using 10 liters of treated water.

From the above, it is clear that in Europe, according to the present invention, the transient pressure difference does not rise at the beginning of restarting operation or at the beginning of test operation, so the planned amount of treated water can be recovered from the beginning, and the cladding can be removed. It is possible to use an OK circulation tank that contains the suspension, or to attach a separate small-capacity auxiliary tank and piping and connect a valve, so the present invention can be used for new construction. , can be easily implemented regardless of the existing installation.

Furthermore, if the operation of the present invention is continued, a cake layer of cladding will be successively formed on the cake layer formed of fine particles, and if the surface of the cladding cake layer is at a distance from the inner surface of the tube filter, then Part of the cake layer is peeled off, and the cake layer grows again.In this way, one peeling and regeneration are repeated, so no growth occurs on a certain plate. The flow sheet of the filtration device, FIG. 2 is a diagram showing the state of 1-pass differential pressure during operation of the conventional example and an embodiment of the present invention, and FIG. 3 is a diagram showing the recovery state of treated water. In the figure, / is the filtration network of the parallel flow filtration device, 3 is the inlet chamber, ! t indicates the outlet chamber, t indicates the porous tube filter, and ria indicates the filtration ice chamber.

Claims (1)

[Scope of Claims] (1) Wastewater is supplied from the inlet at one end parallel to the filtration surface of the portscape filter and discharged from the outlet at the other end while being circulated and filtered. In a wastewater treatment method using a parallel flLfl filtration device that discharges in a direction perpendicular to the flow, fine particles such as iron oxide are removed from the above-mentioned prior to filtration.
A wastewater treatment method characterized by pre-coating the surface of the hot water. (2. In the method described in claim (1), the particle size of the fine particles has a minimum diameter of 04h0, which is the same as the inner diameter of the bore of the porous shape filter, and is larger than that. (3) ) Claim 11(1) or (In the method i, mold spores are suspended in pure water or water from which s and g have been removed, and this suspension is passed through a port step filter. A wastewater treatment method in which wastewater is supplied from an inlet and circulated while being discharged from an outlet at the other end to form a pre-coat layer.