JPH01115500A - Slurry filtering method - Google Patents

Abstract

PURPOSE:To prevent concn. polarization from being generated and to inhibit scaling by closing a rapid on-off valve provided to a flow route of slurry passed through a filter in a short time. CONSTITUTION:Slurry having non-Newtonian flow characteristics such as activated sludge slurry at a time for treating excretion and marine products working waste liquid is filtered with an ultrafiltration membrane. In this case, an automatic on-off valve 6 is provided between a filter 7 and a circulation pump 4 and when repeating operation for closing and opening this valve 6 in a short time while keeping an interval, pressure pulse is impressed to the filter 7. Since concn. polarization is prevented from being generated by such a way, slurry which is difficult-to filter and has non-Newtonian flow characteristics can be continuously filtered at high filtration velocity.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is useful for treating wastewater, livestock excrement, fishery processing waste liquid, livestock processing waste liquid, etc. using the activated sludge method. A slurry filtration method for efficiently filtering a slurry having Newtonian flow characteristics using an ultrafiltration membrane (hereinafter referred to as UF membrane) or a precision 1 filtration membrane (micro) filtration membrane (hereinafter referred to as MF membrane)) .

[Conventional technology]

When slurry with non-Newtonian flow characteristics, such as activated slurry, is continuously filtered once using a UF membrane or MF membrane, the filtration performance decreases over time, but this is due to the membrane itself. In addition to deterioration, it is known that scaling is mainly caused by concentration polarization (concentration polarization) near the film surface.

Conventionally known methods for removing attached scale include backwashing, water washing, chemical methods, and when the membrane is cylindrical, ball washing and the like are performed.

In addition, methods for preventing concentration polarization include maintaining the linear velocity of the slurry at 1 to 3 m/sec, mixing air, creating turbulent flow by creating an orifice shape or parallel waveform in the flow path, and the reverse flow method. is used. reverse 7
The 0-method is a method in which the flow direction of the slurry at the inlet and outlet is reversed at regular intervals (for example, Japanese Patent Laid-Open No. 51-10
Publication No. 3084).

[Problem that the invention seeks to solve]

However, although the above-mentioned scale removal methods such as backwashing, water washing, and bowl washing have quick effects on removing scale and increasing filtration efficiency, they require temporary suspension of operation and are rough. Scaling cannot be suppressed.

In addition, in the method of generating turbulent flow to prevent concentration polarization, which can be completely prevented in steady flow, accumulation points of gel-like substances occur, which grow and eventually cause the membrane to flow. The entire tract becomes obstructed.

In contrast, the known reverse flow method is effective, but
The structure of the switching valve is complicated and the equipment cost is extremely high.

The present inventors have conducted various studies on the reverse 70-method, and have found that scaling is essentially suppressed when the flow direction is changed, and when the slurry supply is temporarily turned off.
It was found that setting it to N and OFF worked.

The present invention was made based on the above knowledge, and it does not require complicated valves, does not significantly reduce the usage efficiency of the filtration device, and can maintain the filtration efficiency at a high level.Activated sludge etc. An object of the present invention is to provide a method for concentrating a slurry having non-Newtonian flow characteristics using a separation membrane device such as a UF membrane or a MF membrane.

(Means for Solving the Problems) The present invention has been made to achieve the above object, and the gist thereof is to provide a method for filtering a slurry having non-Newtonian flow characteristics at a membrane fraction I11'lA. A method for filtering a slurry in which the supply of the slurry to be filtered is interrupted for a short period of time at predetermined intervals to generate pressure pulses.

[For production]

The method of the present invention prevents concentration polarization from occurring and suppresses scaling by using a pressure pulse generated by closing a rapid opening/closing valve provided in a flow path of slurry flowing through a filter for a short period of time.

(Example) Fig. 1 shows an example of an apparatus for carrying out the method of the present invention, and reference numeral 1 in the figure is an activated sludge treatment slurry tank that receives waste slurry sent by a waste slurry line 2 to be treated. Slurry W!1 slurry 3 is extracted by a circulation pump 4 and guided to a UFgl filter 7 provided with a UF membrane 7a via an automatic opening/closing valve 6 operated at predetermined intervals by a timer 5. .

The slurry introduced into the filter 7 is filtered by the UF membrane 7a, the liquid that has passed through the membrane 7a is led out through the liquid line 8, and the concentrated slurry is returned to the slurry tank 1 through the concentrated slurry line 9. It will be done.

The slurry 3 in the slurry tank 1 is concentrated to a concentration that is balanced by the degree and amount of waste slurry introduced, the slurry slippage and concentration rate sent to the filter 7, and the liquid level of the slurry tank 1 is Excess sludge line 10 while almost maintaining
It is extracted from

In the above device, if no treatment is applied (1) If filtration continues, the liquid permeation rate of the UF membrane will rapidly decrease and 1.
It becomes impossible to filter.

However, when the automatic opening/closing valve is opened and listened to repeatedly at intervals, pressure pulses as shown in Figure 2 are applied to the filter 7, thereby preventing the filtration rate from decreasing. be done.

At this time, the shorter the interval T1 between the pressure pulses, the higher the filtration rate can be maintained, but the shorter the interval T1, the shorter the filtration time of the device. iMLSS of slurry to be filtered is 20,000~
In the case of 30,000, even if 1 is set to 15 minutes or less; no significant difference in filtration rate is observed, but it is practically desirable to set this to a range of 30 to 120 minutes.

If the MLSS of the slurry to be filtered becomes lower, T1 can be made even longer.

Further, the pressure pulse application time T2 is several seconds to several tens of seconds, and is usually around 10 seconds. It is effective for the waveform of this pressure pulse to be close to a rectangular shape to remove the concentration polarization component.

Therefore, it is desirable to use an automatic on-off valve that fully opens and closes instantaneously.

As described above, the method of the present invention can maintain the overspeed level at a high level by briefly cutting off the supply of slurry fed to the first filter and applying a pressure pulse. The decrease in efficiency due to the temporal overflow is small, and commercially available automatic opening/closing valves can be used.

In the above explanation, an automatic on-off valve was placed between the filter and the circulation pump, and a negative pressure pulse was generated in the one-door filter with respect to the operating pressure. 9 and applying a pressure pulse higher than the steady operating pressure has the same effect.

However, in this case, the pressure pulse is higher than the operating pressure, so the UF membrane needs to be able to withstand this. Therefore, it is preferable to arrange an automatic opening/closing valve at the inlet of the i-filter and operate it by a negative pressure pulse with respect to the operating pressure.

In addition, the method of the present invention is similar to the UF membrane (UF membrane) filter, as well as MF membrane removal:
A similar effect was found for over-the-counter equipment.

[Examples 1 to 3] M L S S 20000 to 30oooIItg/
A filtration test was conducted using J Noshi's raw sludge slurry as the test liquid.

The concentrator is a flat membrane type tJ equipped with a polysulfone tJFIFJ with a fractionation and molecular ffi of 20,000.
A F Fl i filter having an automatic on-off valve on the inlet line was used. The above test liquid was introduced into this I filter at a steady operating pressure of 5 K9/cd, and the D coupler interval T1 was adjusted to 15 minutes, 30 minutes, and 60 minutes using the automatic opening/closing valve.
The pressure pulse was applied for 10 seconds, and the change over time of 1 filter degree was measured. The results are shown in Table 1.

Table 1 [Comparative Example 1] Continuous filtration was performed in the same manner as in Examples 1 to 3 except that no pressure pulse was applied. As a result, the filtration rate (at the start) was 404/Tdhr, and after 15 minutes it was 30
J/'rIthr, but after 90 minutes, the UF membrane was blocked and 1 filter degree became almost O.

〔Effect of the invention〕

As mentioned above, the slurry filtration method according to the present invention is achieved by a simple operation of applying a pressure pulse generated by cutting off the slurry supplied to the filter for a short period of time. Contribute to fields such as pollution treatment with an excellent method that allows slurry with non-Newtonian flow characteristics, such as sludge slurry, to be continuously filtered at a high filtration rate using a membrane separation device such as a UFll or MF membrane. is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an apparatus for carrying out the method of the present invention;
FIG. 2 is a diagram of pulses when an automatic on-off valve is provided on the inlet side of filter 1, and FIG. 3 is a diagram of pulses when an automatic on-off valve is provided on the outlet side of filter I. 1...Activated sludge treatment slurry tank (slurry tank)
, 2... Waste slurry line to be treated (waste slurry line), 3... Slurry, 4... Circulation pump, 5... Timer, 6... ...Automatic opening/closing valve, 7...UF membrane) filter () filter), 7a...
...UF membrane, 8...1 liquid line, 9...concentrated slurry line,
, 10... Surplus 'rFi mud line... Interval for applying pressure pulses, T2...
...Applying time of pressure pulse.

Claims (1)

[Claims] A method for filtering a slurry having non-Newtonian flow characteristics using a membrane separator, the method comprising: cutting off the supply of the slurry to be filtered for a short time at predetermined intervals to generate pressure pulses.