JPS6253785A - Apparatus for separating bacterial cell - Google Patents

Abstract

PURPOSE:To continuously, efficiently and inexpensively remove bacterial cells from raw water containing said cells at high concn. over a long time, by providing a powdery magnetite layer in a tank to utilize the bacterial cell adsorbing characteristic thereof. CONSTITUTION:A raw water introducing port 22 and a treated water discharge port 23 are provided to a tank 21 and a precoat layer 25 containing powdery magnetite and the plate shaped supported means 24 for support said precoat layer 25 are provided so as to separate the introducing port 22 and the discharge port 23. In treating raw water, at first, valves V2-V4, V6 are closed and valves V1, V5 are opened and raw water is supplied into the tank 21 from a biological reaction tank 13 through the introducing port 22 and passed through the precoat layer 25 to be discharged from piping 30. After this discharge has been performed for a predetermined time, the valve V5 is closed while the valve V4 is opened, and raw water is transferred to a treatment process to perform the separation and removal of bacterial cells by the powdery magnetite of the precoat layer 25. When differential pressure increases, backwashing is performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a bacterial cell separation device, and in particular to a bacterial cell separation device that efficiently separates and removes bacterial cells from raw water such as pure water using the bacterial adsorption ability of magnetite. The present invention relates to a body separation device.

[Prior Art] In the manufacture of LSIs and VLSIs, large amounts of pure water and ultrapure water are used. Ultrapure water is pure water having a specific resistance of 17 to 18 MΩecm, which is extremely close to the specific resistance of theoretically pure water (water consisting only of H2O), which is 18.24 MΩ@Cm.

Even in oligotrophic water such as ultrapure water and pure water, microorganisms exist, albeit in very small amounts, and P in the pure water.
If organic substances are present even on the order of Pb, microorganisms will proliferate, causing trouble in pure water production equipment such as RO equipment.

The applicant has solved the problem caused by the proliferation of bacterial cells.

In an ultrapure water production device that includes a membrane treatment device and an ion exchange tower, there is also a biological reaction tank that performs biological treatment in the presence of a trace amount of energy source and/or nutrient source, and bacterial cells grown in this biological reaction tank. We previously filed a patent application (Japanese Patent Application No. 59-231738 (hereinafter referred to as the "prior application")) for an ultrapure water production device equipped with a biological treatment means consisting of a bacterial cell separator for separating and removing bacteria.

FIG. 2 is a system diagram when the deionized water production apparatus of the prior application is employed in a cleaning waste liquid recovery process from a semiconductor wafer cleaning system using ultrapure water.

In FIG. 2, wastewater from the semiconductor cleaning process 1 is first subjected to activated carbon adsorption treatment in the activated carbon adsorption tower 2 of the recovery system A, then treated and desalted in the ion exchange tower 3, and then further treated with a reverse osmosis membrane device if necessary. (not shown) and is treated with an ultraviolet oxidation device 4. In the ultraviolet fermentation device 4, in order to almost completely oxidize and decompose organic matter, generally,
Hydrogen peroxide is added as an oxidizing agent, and the treatment is performed by irradiating ultraviolet rays in the presence of hydrogen peroxide.

Such an activated carbon adsorption tower2. Treated water from recovery system A consisting of ion exchange tower 3 and ultraviolet oxidizer 4 is introduced into biological reaction tank 13 of biological treatment system F, and is subjected to aerobic biological treatment. Due to the reaction in the biological reaction tank 13, organic carbon becomes CO2 or bacterial cells. The bacterial cells are captured and separated in the subsequent bacterial cell separator 14. Since the water from which the bacterial cells have been separated has an extremely low concentration of TOC, it has almost no ability to proliferate microorganisms.This water is then processed into a pretreatment system C (consisting of a coagulation tank 5 and a two-tank filter 6), Primary pure water system D (consisting of reverse osmosis membrane device 7, deaerator 8 and ion exchange device 9) and subsystem E (ultraviolet sterilizer 10, mixed bed exchange device 11 and ultrafiltration membrane device 12)
Consisting of ) is introduced into the supply side of the primary pure water system D of the pure water production system B consisting of:

According to the pure water production device of the previous application, TOC and/or phosphorus components can be removed to an extremely low concentration at low cost, so that the produced pure water is free of TOC, which is a factor of microbial growth. and/or the concentration of the phosphorus component is extremely low, and the growth of microorganisms is reliably suppressed.

By the way, membrane separation devices such as microfiltration devices and ultrafiltration devices are generally used as bacterial cell separators for such pure water production equipment and other conventional bacterial cell separators in the water treatment field. According to these membrane separators, III in raw water
When the number is at a low level, bacterial cells can be isolated with good separation efficiency.

[Problems to be solved by the invention] However, if the number of bacteria in the raw water is high, for example lo'
If it is more than N/mu, the membrane will be severely clogged and it will be difficult to operate the membrane separation device continuously for a long period of time.

In particular, in the device of the prior application shown in FIG. 2, the number of viable bacteria in the raw water fed to the bacterial cell separator 14 increases because a biological treatment method is adopted to remove organic matter. However, the raw water contains bacterial cells at a high concentration. (TOC is l
mg/l, the number of bacteria is 10' to 10'
It will be about N/ml. ) Therefore, it is not easy to efficiently and inexpensively remove bacterial cells continuously over a long period of time from raw water containing such high concentrations of bacterial cells.

Means for Solving Problem E 1 The present invention provides a powdered magnetite layer in a tank, utilizes the bacterial adsorption properties of magnetite, and efficiently separates bacterial cells.

In addition, using a magnetic material such as magnetite as a filter aid,
Several methods for removing particulate matter using a pre-coat filter method have been reported (Publications 1982-20466, 1980-129063, 1982-18263), L.
However, these documents all relate to the recovery and reuse of magnetic filter aids, and do not mention anything about the ability of magnetite to remove bacterial cells.

[Function] Magnetite has the ability to adsorb and retain bacterial cells. According to the bacterial cell separation device of the present invention, magnetite has the ability to adsorb bacterial cells and retain them.
The number of bacteria in water containing bacteria at a high concentration of N/m is reduced to 1/10.
It is possible to easily reduce it to about 0 to 1/1000. (For details on the magnetite bacterial adsorption mechanism, see
(Currently, it is not fully clear.) The bacterial cell separation device of the present invention utilizes the bacterial adsorption properties of magtite, and uses the so-called magnetic treatment method that utilizes the agglomeration properties of magnetite in a magnetic field. Unlike the above, there is no need to apply a magnetic field during processing.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view showing a bacterial cell separation device 20 according to an embodiment. This embodiment is used as a bacterial cell separator in a pure water production apparatus shown in FIG.

In the figure, a tank 21 is provided with an inlet 22 for raw water and an outlet 23 for treated water, and a precoat layer 25 containing powdered magnetite and a precoat layer 25 that supports it are separated from the inlet 22 and outlet 23 for treated water. A plate-like support means 24 is provided for this purpose.

A pipe 26 having a valve V+ is connected to the inlet 22 so that raw water can be introduced. In the middle of piping 26,
Valve V2. Pipe 27.28 with V3 is connected,
It is said that diatomaceous earth and powdered magnetite can be supplied.

Furthermore, a treated water discharge pipe 29 having a valve v4 is connected to the treated water discharge port 23.

Further, each pipe 29.26 is connected to a branch pipe 30.3.
1 is connected to backwash water into tank 21.

This makes it possible to introduce and discharge. Vs and Vs are valves provided in the branch pipes 30 and 31.

The support means 24 includes a bottom plate of the tank 21 made of a perforated plate,
It is formed by pasting Saran net on top of it. To form a precoat layer on this support means 24, first, valves v3 and v2 are opened to supply powdered magnetite and diatomaceous earth to the tank; then, valve v5 is opened to supply backwash water, or.

Valve V+ is opened and raw water is supplied to the vicinity of the precoat layer 25 surface. Then open valve v5.

Clear air (air passed through a fi!i filter) is supplied from the branch pipe 30 to uniformly mix powdered magnetite and diatomaceous earth. Note that during this air mixing, the valve v6 is opened to perform exhaustion. As a result, a uniform precoat layer 25 is formed.

The pre-coat layer supports the powdered magnetite well,
In order to maintain water permeability and reduce filtration resistance, it is preferable to use a mixed layer of powdered magnetite and other powder as the other powder.

In addition to diatomaceous earth, inorganic fibrous substances are used.

The particle size of powdered magnetite is preferably about 0.2 to 5 gm, and the particle size of other powders is about 10 to 1 gm.
If the particle size is too large, the bacterial adsorption effect will be reduced, and if the particle size is too small, the filtration resistance will be increased and the treatment efficiency will be reduced.

The mixing ratio of powdered magnetite and other powder is 1:3.
~l: It is preferable to set it to about 10' (volume ratio).

The amount of pre-coating of the mixture of powdered magnetite and other powders is appropriately determined depending on the scale of the bacterial cell separation device, the quality of the raw water, and the like.

When processing raw water, first, valves V7, Vl, and V
4. Leave Vs blank, t<V+, Vs open, and feed the raw water (treated water of the biological reaction layer 13) into the tank 2 from the inlet 22.
1 and allowed to pass through the precoat layer 25. Therefore, the liquid that has passed through the precoat layer 25 is drained from the pipe 30. After this drainage has been carried out for a predetermined period of time, valve v5 is closed, valve v4 is opened, and the process proceeds to the treatment process. In this treatment process, bacterial cells are sufficiently separated and removed by powdered magnetite in the precoat layer 25, and the treated water outlet 23 and piping 2
It is discharged from 9 and fed to the 1 caustic water system D in the subsequent process.

If the differential pressure increases due to the flow of raw water.

Valves Vs and Va are opened to supply wash water into the tank 21 for backwashing. The LV (linear velocity) of backwashing is carried out at such a level that the precoat agent does not flow out, so that the bacterial cells captured by the precoat layer 25 can be discharged to the outside of the tank.

After backwashing, water is drained to near the surface of the precoat layer 25 through a valve V5, and mixing and stirring are performed by supplying clear air as in the initial precoat layer formation to form a uniform precoat layer 25. After that.

After passing through the drainage process mentioned in the raw water treatment process, the process returns to the treatment process.

In the device of the present invention, the increase in differential pressure is thought to occur mainly due to clogging of the precoat layer before the amount of bacteria adsorbed by magnetite reaches the saturation amount. It becomes possible to reuse magnetite.

It should be noted that the bacterial cell separation device of the present invention is not limited to the one having the configuration shown in FIG. 1, but may be of other types.
It is preferable to use a pre-coat type which has a high filtration effect.In addition to the one shown in the figure, the pre-coat type can be used, for example, on the bottom plate of a tank.

Such a structure may be one in which a large number of porous cylindrical members are erected, Saran net or stainless steel wire netting is wrapped around the cylindrical member to constitute a supporting means, and a precoat layer is formed on the supporting means. In this case, the effect of increasing the filtration area is achieved.

The bacterial cell separation device of the present invention can further improve the quality of the treated water by installing a normal membrane separation device on the downstream side as necessary and further membrane-treating the treated water.

In the above explanation, the case where the bacterial cell separation device of the present invention is used as a bacterial cell separator in the process of treating waste water from a semiconductor cleaning process and regenerating it into ultrapure water has been described. Naturally, the present invention can be applied to various types of equipment, such as equipment for treating water recovered from other processes, or equipment for producing pure water from aqua regia, well water, etc.

The present invention will be explained in more detail with reference to experimental examples below.

Experimental Example 1 Raw water containing bacterial cells was treated using the bacterial cell separation apparatus of the present invention shown in FIG.

The magnetite layer is a mixed layer of magnetite and diatomaceous earth, and the pre-coating amount is 0.4 kg of magnetite/
ITI', diatomaceous earth 0.8 kg/IT1'. Also,
The number of viable bacteria in the raw water was 3 to 5XIO5N/m, and the flow rate (LV) of the raw water was 6 m/hr.

Figure 3 shows the number of viable bacteria in the treated water and the changes over time in the water flow differential pressure.

As is clear from Figure 3, the number of viable bacteria in the treated water is
~10'N/ml, and the average bacterial cell removal rate was 99%.

In addition, as is clear from Figure 3, when the differential pressure of the magnetite layer reaches approximately 1.7 kg/cm'', simply backwashing with treated water and re-precoating reduces the bacterial removal rate. It was possible to reuse the product without causing any damage, and it showed a high bacterial cell removal rate even when the cumulative flow rate of raw water was 40 m''/rr1' or more.

(Effect 1 As detailed above, the bacterial cell separation device of the present invention utilizes the bacteria adsorption property of magnetite itself.

There is no need to apply a magnetic field, and bacterial cells can be efficiently separated and removed at low cost. Furthermore, even raw water containing a high concentration of bacterial cells can be continuously treated without maintenance for a long period of time.

According to the bacterial cell separation device of the present invention, bacterial cells can be separated from 106 to IO"
Even if raw water contains a high concentration of N/mJ1 or more, it is possible to significantly reduce the number of bacteria to 1/100-1/1000.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the bacterial cell separation device of the present invention, Figure 2 is a system diagram showing the pure water production/recovery system, and Figure 3 shows the results obtained in Experimental Example 1, showing raw water and treated water. It is a graph showing the relationship between the change in the number of viable bacteria and the cumulative amount of water flow and the differential pressure. A... Recovery system, B... Pure water production system,
C...Pretreatment system, D...Primary pure water system. E... Subsystem, F... Biological treatment system, 4... Ultraviolet oxidation device, 7... Reverse osmosis membrane device, 9
...Ion exchange device, 12...Ultrafiltration membrane device, 1
3... Biological reaction tank, 14... Bacterial cell separator, 20
... Bacterial cell separation device, 21 ... Tank, 22 ... Raw water inlet, 23 ... Treated water outlet, 24 ... Support means, 25 ... Precoat layer.

Claims (3)

[Claims] (1) An apparatus for separating bacterial cells from raw water containing bacterial cells, in which a powdered magnetite layer and a means for supporting the powdered magnetite layer are placed in a tank having an inlet for raw water and a drain for treated water. A bacterial cell separation device characterized in that the inlet and the outlet are separated from each other. (2) The bacterial cell separation device according to claim 1, wherein the powdered magnetite layer is a mixed layer of powdered magnetite and other powder. (3) The bacterial cell separation device according to claim 2, wherein the other powder is diatomaceous earth.