JPS6265792A - Biological treatment of water containing trace organic material - Google Patents

Abstract

PURPOSE:To permit the effective biological treatment of water contg. trace org. materials at a low treatment cost by utilizing the dissolved oxygen of the water contg. trace org. materials as the oxygen necessary for making the biological treatment. CONSTITUTION:The dissolved oxygen of the water contg. trace org. materials is utilized as the oxygen necessary for making the biological treatment in a method for making the aerobic biological treatment in a bioreaction tank 1 contg. living thing fixing means2 contg. trace org. materals. Municipal supply water, water recovered from a semiconductor plant, etc. having <=5mg/l TOC concn., for example, 2-5mg/l TOC cocn. or below are used as the water contg. trace org. materials. The water contg. trace org. materials is aerobically and biologically treated without aeration in this method and since there is no need for an aeration stage, running cost is reduced and the installation is simplified. The effective biological treatment of the water contg. trace org. materials at the low treatment cost is thus possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a biological treatment method for water containing trace amounts of organic matter.
In particular, the present invention relates to a biological treatment method for water containing trace amounts of organic matter, which is suitable for application to facilities for producing pure water or ultrapure water.

[Prior Art] In the production of LSI and fiLsI, large amounts of pure water and ultrapure water are used. Ultrapure water is pure water having a specific resistance of 17 to 18 MΩ*cm, 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 or pure water, microorganisms exist, albeit in very small amounts.If organic substances, even on the order of PPb, are present in pure water, microorganisms will proliferate, causing RO equipment This may cause trouble in other pure water production equipment.

The present applicant previously developed a method for suppressing the growth of microorganisms in water containing extremely small amounts of organic matter, such as ultrapure water used in the electronics industry, etc., by using a biological reaction tank with built-in biological fixation means. He discovered a method of chemically treating water to remove phosphorus components and make it phosphorus-deficient water, and filed a patent application (Japanese Patent Application No. 59-231737, hereinafter referred to as "Saiken Ko").
).

In addition, the present applicant has also developed an ultrapure water production device having a membrane treatment device and an ion exchange tower, which solves the problem caused by the proliferation of microorganisms in water containing trace amounts of organic matter. Added biological treatment means consisting of a biological reaction tank for biological treatment in the presence of an energy source and/or nutrient source, and a bacterial cell separator for separating and removing bacterial cells grown in this biological reaction tank. A patent application was previously filed for an ultrapure water production device (Japanese patent application No. 59-231738).
, hereinafter referred to as "first application ■". ).

The method of treating water containing trace amounts of organic matter with oligotrophic bacteria, which is disclosed in the above-mentioned prior application and prior application (■), has high treatment efficiency and lower running costs than the conventional ultraviolet oxidation method. This is a low and extremely effective treatment method.

[Problems to be solved by the invention] Generally, when raw water is subjected to aerobic biological treatment, in order to decompose organic matter contained in the raw water,
Supply of air (oxygen) is essential. For example, in activated sludge methods, an aeration step is usually provided to supply air.

However, in aerobic biological treatment, about 1/3 of the running cost of the equipment is accounted for by power costs such as the blower of the aeration equipment, and the existence of the aeration process has been a factor that increases the treatment cost.

[Means for Solving the Problems] As a result of extensive research into aeration treatment in such aerobic biological treatment, the present inventors found that when water containing trace amounts of organic matter is subjected to aerobic biological treatment, The present invention was achieved by discovering that the treatment can be carried out without aeration treatment as in conventional methods.

That is, the TOC concentration was reduced to 5 m by the aerobic biological treatment method.
Water with a weight of 7 sentences or less 1 For example, when treating tap water with a ROCG degree of 2 to 5 mg/l, semiconductor factory recovered water, etc., the amount of dissolved oxygen in the water is sufficiently close to the saturation value, so it is necessary to remove oxygen by aeration. There is no need to supply it.

For this reason, in the present invention, in the method of aerobically biologically treating water containing organic matter in a biological reaction tank equipped with biological fixation means, a trace amount of oxygen is required for biological treatment. The system uses dissolved oxygen in water containing organic matter.

The present invention will be explained in detail below.

In the present invention, the trace organic matter-containing water to be treated includes:
To Ci1 degree 5 mg/n or less, e.g. roc
Examples include tap water with a degree B of 2 to 5 mg/l or less, water recovered from a semiconductor factory, and the like.

Raw water with such a low TOC concentration produces a small amount of sludge through biological treatment, so it is not possible to maintain bacterial cells using a floating method such as the normal activated sludge treatment method.
It's inappropriate. For this reason, in the present invention, a biological reaction tank containing biological fixation means is used, and the treatment is carried out in a fixed bed system or a fluidized bed system.

Generally, organisms that survive in water containing trace amounts of organic matter with a TOC concentration of several mg/λ or less are oligotrophic bacteria.

In the present invention, these oligotrophic bacteria are activated by dissolved oxygen in water containing trace amounts of organic matter, and exhibit extremely high organic matter treatment effects.

In addition, as a specific bacterial species of such oligotrophic bacteria, oligotrophic bacteria (Origotrophic bacteria)
, ic bacteria), etc. are suitable. Oligotrophic bacteria are microorganisms that grow in water with extremely low TOC concentrations, such as ultrapure water, and by using them, the TOC concentration in treated water can be reduced to 50 ppb.
Hereinafter, for example, it is possible to reduce the concentration to about 10 to about PPb or less, and if it is a phosphorus or nitrogen concentration, to about toppb or less.

[Operation] Water with a low TOC concentration generally contains dissolved oxygen at approximately the saturation value. Furthermore, water with a low TOC requires only a small amount of oxygen to perform aerobic biological treatment.

According to the present invention, by utilizing this dissolved oxygen,
It becomes possible to perform aerobic biological treatment without providing an aeration process.

[Example] EXAMPLES The present invention will be described in more detail below with reference to Examples.

Example 1 As shown in Fig. 1, a fluidized bed biological reaction tank l containing granular ceramic acid with a particle size of 0.7 mm was used as the filler 2, and synthetic water (with a concentration of acetic acid) was used without aeration. 1 mg-C
/l) biological treatment was performed.

In addition, in FIG. 1, 3 is a raw water supply pipe, 4 is a treated water discharge pipe, and 5 is a circulation line.

As a result, as shown in Table 1, the residence time (D.

T,) In 10 minutes, the amount of acetic acid in the inflow water (synthetic water) is 15 gg-
C/Jl or less, and it was confirmed that the particles were almost completely removed. Also, the dissolved oxygen (0,0,) in the inflow water is 7
, 7 mg/L; decreased from 5.3 mg/L to 5.3 mg/L, indicating that the amount was spent on aerobic treatment.

@1 Table As is clear from this example, according to the present invention, aerobic biological treatment can be performed without aeration, and treated water of good quality can be obtained.

[Effects of the Invention] As detailed above, the method of the present invention performs aerobic biological treatment of water containing trace amounts of organic matter without aeration, and since an aeration process is not required, power costs for blowers, etc. are reduced. gone,
It is possible to reduce running costs and simplify equipment. Therefore, according to the present invention, it is possible to effectively biologically treat water containing trace amounts of organic matter at extremely low treatment costs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the biological reaction tank used in Example 1. l...biological reaction tank, 2...filling material.

Claims (2)

[Claims] (1) In a method of aerobically biologically treating water containing trace amounts of organic matter in a biological reaction tank with built-in biological fixation means, dissolved oxygen in water containing trace amounts of organic matter is used as the oxygen necessary for biological treatment. A biological treatment method for water containing trace amounts of organic matter. (2) The method according to claim 1, wherein the water containing trace organic matter has a TOC concentration of 5 mg/l or less.