JP2712457B2 - Membrane separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a membrane separation device, and in particular, it is possible to increase the amount of filtered water and improve the quality of treated water by suppressing the destruction of flocs by a circulation pump. The present invention relates to a membrane separation device.

[Prior art] Fine suspended or colloidal substances contained in raw water,
When a flocculant or a pH adjuster is added to separate components such as a soluble substance to form a floc, and a membrane is separated as a suspended substance by a parallel flow method, a membrane separation apparatus as shown in FIG. 2 is generally employed. You.

That is, in the membrane separation device shown in FIG. 2, raw water is supplied to the flocculating tank (or pH adjusting tank) 1 by the flocculant and / or
Alternatively, a pH adjuster from the pH adjuster tank 3 is added. The coagulated water is supplied to the circulation tank 4 and separated by the circulation pump P.
It is introduced into the membrane separator 5 provided with 5a in a parallel flow manner, and the suspended substance is separated and concentrated. The treated water is discharged out of the system. In FIG. 2, P ₁ and P ₂ are chemical injection pumps.

[Problems to be Solved by the Invention] When a membrane separation process is performed by the membrane separation apparatus shown in FIG. 2, the filtration flux (hereinafter, referred to as “flux”) of the membrane separator 5 decreases with time. . The cause of this decrease in flux is an increase in resistance due to accumulation of suspended solids on the membrane surface.

Increased resistance due to penetration of suspended matter into the pores of the membrane.

Refinement of the suspended solids by the circulating pump P and the accompanying difficulty in filtering the suspended solids.

Can be considered. The present inventors further examined the problem of flux reduction, and found that among the above factors, the following factors were particularly large, and the fineness of the suspended substance by the circulation pump was further promoted. It has been found that the liquefied matter permeates through the membrane and the quality of the treated water deteriorates.

In order to reduce the fineness of the suspended substance by such a circulating pump, as shown in FIG. 3, it is conceivable to add a flocculant and / or a pH adjuster directly to the circulation tank 4 for treatment. (Note that in FIG. 3, components having the same functions as those shown in FIG. 2 are denoted by the same reference numerals and description thereof is omitted.) However, in the membrane separation device shown in FIG. And / or the time until the membrane separation after the addition of the pH adjuster is short, and thus the coagulation time is short, so that the membrane separation treatment is performed before sufficient coagulation is performed, and the quality of the treated water quality is reduced. There are problems of deterioration and increased filtration resistance due to suspended matter.

An object of the present invention is to solve the above-mentioned conventional problems, to provide a membrane separation device capable of suppressing the destruction of flocs by a circulating pump, and obtaining a treated water of remarkably excellent water quality with a high amount of filtered water. .

[Means for Solving the Problems] The membrane separation device of the present invention performs a membrane separation process of a coagulation tank by adding a coagulant and / or a pH adjuster to raw water and a coagulation treatment water in a parallel flow system. In a membrane separation apparatus including a membrane separator, a circulation tank for circulating coagulation-treated water through the membrane separator, and a circulation pump, the circulation tank includes a coagulant adding means and / or
Alternatively, a pH adjusting agent adding means is provided.

Hereinafter, the present invention will be described in detail with reference to the drawings. First
FIG. 1 is a system diagram of a membrane separation device according to one embodiment of the present invention.

The illustrated membrane separation apparatus mainly includes a coagulation tank 1, a coagulant tank 2, a pH adjuster tank 3, a circulation tank 4, a membrane separator 5 having a separation membrane 5a, and a circulation pump P. Connected at 17. P ₁ and P ₂ are chemical injection pumps.

When processing the membrane separation apparatus shown in FIG. 1, the raw water is introduced into flocculation tank from first piping 11, coagulant is supplied through a pipe 16,16a that from coagulant tank 2 comprises a chemical feeding, chemical dosing pump P ₁ and / or coagulation treatment at pH adjusting agent supplied through a pipe 17,17a with a chemical feeding, chemical dosing pump P ₂ than the pH adjusting agent tank 3.

The coagulated water passes through the pipe 12, the circulation tank 4, and the pipe 13, and is introduced into the membrane separator 5 by the circulation pump P in a parallel flow manner with respect to the separation membrane 5a. The concentrated water of the membrane separator 5 is circulated to the circulation tank 4 via a pipe 14, while the treated water is discharged out of the system via a pipe 15.

In the circulating tank 4, the concentrated water (circulated water) circulated from the pipe 14 and the coagulated treated water introduced from the coagulating tank 1 via the pipe 12 are connected to the pipe provided with the chemical injection pump P ₁ from the coagulant tank 2.
Flocculants and / or pH adjusting agent through a piping 17,17b with a chemical feeding, chemical dosing pump P ₂ than the pH adjusting agent tank 3 is added through 16, 16b. With the added flocculant and / or pH adjuster, the suspended matter in the concentrated water circulated through the pipe 14, particularly the suspended matter fined by the circulation pump P, is effectively reagglomerated. Further, the flocculation treatment water introduced from the flocculation tank 1 through the pipe 12 further promotes the flocculation.

For this reason, the flocculated water and the circulating water, in which the finely divided suspended substances are significantly reduced, are always supplied to the membrane separator 5, the flux is maintained at a high level, and the quality of the treated water is also extremely high. .

The raw water to be treated by the membrane separation apparatus of the present invention is not particularly limited, and examples thereof include metal-containing wastewater such as garbage incineration smoke washing wastewater and plating factory wastewater.

The separation membrane of the membrane separator is not particularly limited, and a microfiltration membrane or an ultrafiltration membrane used in a usual parallel flow type membrane separation treatment can be used. In particular, when a microfiltration membrane is used, the quality of the treated water is stable and high, and excellent effects can be obtained.

In the present invention, the addition of the flocculant and / or the pH adjuster to the circulation tank may be continuous or intermittent, and is appropriately determined according to the raw water quality, the circulating water quality, and the like.

In the present invention, since the coagulant and / or the pH adjuster are added in two stages to the coagulation tank and the circulation tank, there is a concern that the amount of the drug used may increase, but in the present invention, the amount of the chemical used is about the same as the conventional one May be added separately to the coagulation tank and the circulation tank, and it is not necessary to particularly increase the amount of drug used.

[Operation] In the membrane separation device of the present invention, since the flocculating agent and / or the pH adjusting agent adding means is provided in the circulation tank, the finely divided suspended substance by the circulation pump is returned to the circulation tank when returned. Is reagglomerated by the added flocculant and / or pH adjuster.

For this reason, finely divided suspended substances deteriorate filtration performance, increase membrane resistance by penetrating into the pores of the membrane, reduce flux, and further deteriorate the quality of treated water by permeating the membrane. The problem is improved.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1 A membrane separation test was performed using the membrane separation apparatus of the present invention shown in FIG. In addition, raw water, a separation membrane, operating conditions, etc. are as follows.

Raw water: Fluorine-containing wastewater F; 30 mg / l Separation membrane: Tubular type microfiltration membrane Pore size: 0.2 μm Coagulation tank medicine injection amount: Sulfuric acid band; 1500 mg / l (neutralized with NaOH) Circulation tank medicine injection amount: Sulfuric acid band; 500 mg / l (intermittent inflow) (neutralized with NaOH) Membrane separator operating conditions: pressure; 2 kg / cm ² circulating water flow; 8.5 l / min backwash; once / 30 minutes The test results are shown in Table 1.

Example 2 A test was performed in the same manner as in Example 1 except that the chemical injection in the circulation tank was continuously injected, and the results are shown in Table 1.

Comparative Example 1 A test was conducted in the same manner as in Example 1 except that a sulfate band of 2000 mg / l was added only to the flocculation tank and neutralized with NaOH using the membrane separation apparatus shown in FIG. Indicated.

Comparative Example 2 Raw water was directly introduced into the circulation tank by using the membrane separation apparatus shown in FIG.
Was performed in the same manner as in Example 1 except that the solution was added and neutralized with NaOH. The results are shown in Table 1.

The following is clear from Table 1.

According to the membrane separation devices of the present invention of Examples 1 and 2, the amount of filtered water was increased by about 40% and the quality of the treated water was stably good as compared with the membrane separation device of FIG. 2 of Comparative Example 1. . This is considered to be because the suspended matter refined by the circulation pump was reaggregated by the sulfuric acid band intermittently or continuously added to the circulation tank. According to the membrane separator shown in FIG. 3 of Comparative Example 2, the amount of filtered water was increased by 15% and the quality of the membrane treated water was better than that of the membrane separator shown in FIG. 2 of Comparative Example 1. The effect was small compared to 1 and 2. The membrane separation apparatus shown in FIG. 3 of Comparative Example 2 performs the coagulation reaction and the re-coagulation simultaneously in the circulation tank. This is probably because the fine suspended solids permeated and affected the treated water. In addition, it is considered that the filtration resistance of the suspended substance was increased due to incomplete aggregation, and the flux was also reduced as compared with Examples 1 and 2.

Example 3 A membrane separation test was performed using the membrane separation apparatus of the present invention shown in FIG. In addition, raw water, a separation membrane, operating conditions, etc. are as follows.

Raw water: plating wastewater pH; 3.0 COD; 20mg / l Cu; 16.9mg / l Fe; 1.1mg / l separation membrane: flat ultrafiltration membrane a fractionation molecular weight; 50,000 flocculation tank chemical feed amount: MgSO ₄ · 7H ₂ O; 70mg / l (as Mg) (adjusted to at NaOH pH11) circulation tank chemical feed _{amount: MgSO 4 · 7H 2 O;} ( intermittent infusion as Mg) 30mg / l (adjusted to pH11 with NaOH) membrane separator operating conditions : Pressure; 2 kg / cm ² circulating water volume; 9.6 l / min The test results are shown in Table 2.

Example 4 A test was conducted in the same manner as in Example 3 except that the chemical injection in the circulation tank was continuously injected, and the results are shown in Table 2.

The membrane separation apparatus shown in Comparative Example 3 Fig. 2, MgSO ₄ only coagulation tank
A test was conducted in the same manner as in Example 3 except that 100 mg / l (as Mg) of 7H ₂ O was added and the pH was adjusted to 11 with NaOH, and the results are shown in Table 2.

Comparative Example 4 Raw water was directly introduced into the circulation tank by using the membrane separation apparatus shown in FIG. 3 without providing a flocculation tank, and 100 mg of MgSO ₄ .7H ₂ O was introduced into the circulation tank.
The test was performed in the same manner as in Example 3 except that the pH was adjusted to 11 with NaOH after adding / l (as Mg), and the results are shown in Table 2.

 The following is clear from Table 2.

According to the membrane separation devices of the present invention of Examples 3 and 4, the amount of filtered water was increased by about 20% as compared with the membrane separation device of Comparative Example 3 shown in FIG. Note that the treated water quality was the same in Examples 3 and 4 and Comparative Examples 3 and 4. This is presumably because the use of an ultrafiltration membrane having a molecular weight cut-off of 50,000 enabled the removal of fine suspended substances using a circulating pump.

That is, in the case of the ultrafiltration membrane, the pore size is smaller than the microfiltration membrane, so that the microfiltration does not permeate the membrane even if it is miniaturized.

Example 5 A membrane separation test was performed using the membrane separation apparatus of the present invention shown in FIG. In addition, raw water, a separation membrane, operating conditions, etc. are as follows.

Raw water: lead, mercury-containing waste water Pb; 0.5mg / l Hg; 0.2mg / l separation membrane: tubular type microfiltration membrane pore size; 0.2 [mu] m flocculation tank chemical feed _{amount: FeCl 3 · 6H 2 O;} 80mg / l (Fe as) (neutralized with NaOH) circulation tank chemical feed _{amount: FeCl 3 · 6H 2 O;} 20mg / l ( intermittent infusion as Fe) (neutralized with NaOH) membrane separator operating conditions: pressure; 2 kg / cm ² circulating water ; 8.5 l / min Backwash; 1 time / 30 minutes The test results are shown in Table 3.

Example 6 A test was conducted in the same manner as in Example 5 except that the chemical injection in the circulation tank was continuously injected, and the results are shown in Table 3.

The membrane separation apparatus shown in Comparative Example 5 FIG. 2, FeCl ₃ only coagulation tank
A test was performed in the same manner as in Example 5 except that 6H ₂ O was added at 100 mg / l (as Fe) and neutralized with NaOH,
It is shown in the table.

Comparative Example 6 Raw water was directly introduced into the circulation tank by using the membrane separation apparatus shown in FIG. 3 without providing a flocculation tank, and 100 mg of FeCl ₃ .6H ₂ O was introduced into the circulation tank.
The test was conducted in the same manner as in Example 5 except that / l (as Fe) was added and neutralized with NaOH, and the results are shown in Table 3.

According to Table 3, according to the membrane separation device of the present invention, Comparative Example 5
It is clear that the amount of filtered water is increased by about 25% and the quality of the treated water is stable and good as compared with the membrane separation device shown in FIG.

[Effects of the Invention] As described above in detail, according to the membrane separation device of the present invention, the suspended substance miniaturized by the circulation pump is reaggregated in the circulation tank, so that the suspended material accompanying the micronization is suspended. This makes it difficult to filter the substance, increases the resistance due to the penetration of suspended substances into the pores of the membrane, and suppresses the decrease in flux. In addition, the permeation of the finely divided suspended substance through the membrane is prevented, and the quality of the treated water is improved.

For this reason, according to the membrane separation device of the present invention, it is possible to stably obtain treated water having extremely good water quality with a flux 20 to 40% higher than that of the conventional method.

[Brief description of the drawings]

FIG. 1 is a system diagram of a membrane separation device according to one embodiment of the present invention,
2 and 3 are system diagrams each showing a conventional membrane separation device. 1 ... coagulation tank, 2 ... coagulant tank, 3 ... pH adjuster tank, 4
... circulation tank, 5 ... membrane separator, P ... circulation pump.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-61691 (JP, A) JP-A-61-125407 (JP, A) JP-A-56-31496 (JP, A) 97217 (JP, A) JP-A-52-125476 (JP, A) JP-A-52-73555 (JP, A)

Claims (1)

(57) [Claims] 1. A coagulation tank for coagulating a raw water by adding a coagulant and / or a pH adjuster, a membrane separator for separating the coagulated water in a parallel flow manner, and a membrane separator for the coagulated water. A membrane separation device comprising a circulation tank and a circulation pump for circulating water, wherein the circulation tank is provided with a flocculant adding means and / or a pH adjusting agent adding means.