JPH07328658A - Purifying treatment of waste water - Google Patents

Abstract

PURPOSE:To provide a continuous purifying treating method of waste water capable of purifying simultaneously and efficiently COD and SS in various waste water. CONSTITUTION:An oxidizing agent is forcedly mixed to a spiral flow containing finely divided bubbles formed in an inside of a waste liq. treating vessel 1 by using a self-suction stirring type gas-liquid contact device having a structure fitted with a bubbling stirring means 2 in which plural impellers 14 are provided at the bottom end part of a rotary shaft 12 served also as a vent hole having an air suction hole 15 at its upper part and plural air jetting holes 16 are bored in the rotary shaft 12 corresponding to a back part of the impellers fitted to the waste liq. treating vessel 1. An aq. soln. of sodium hypochloride is used as the oxidizing agent.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is capable of efficiently purifying various wastewater containing COD (chemical oxygen demand) and SS (suspended substance) such as kitchen wastewater, secondary sewage treatment water, and pulp wastewater. The present invention relates to a wastewater purification treatment method.

[0002]

2. Description of the Related Art Industrial kitchen wastewater, factory wastewater, etc., which are routinely discharged from restaurants and industrial production facilities, are unavoidable.
OD, SS, etc. are contained. Conventionally, for the organic SS contained in these wastewaters, a filtration separation method in which coarse particles are aggregated by the addition of a flocculant and then separated by filtration with a filter or a foam separation in which air is carried by bubbling bubbles and separated On the other hand, there is known a method of removing COD components by oxidizing and decomposing COD components by adding an oxidizing agent such as NaClO to a reaction tank with a stirrer, and there are many proposals regarding this type of purification treatment technology. Has been done.

However, in these conventional techniques, the installation area of the processing apparatus used is generally large, and
Since there are many discontinuous operations, the treatment efficiency is low.
Further, recently, research has been conducted to effectively recycle purified water obtained by treating kitchen wastewater as wash water for toilets and the like, and development of a compact and continuously treatable apparatus and treatment method has been demanded.

[0004]

DISCLOSURE OF THE INVENTION As a result of intensive studies on the purification treatment of wastewater satisfying the above-mentioned requirements, the present inventors have found that a compact self-priming stirring type gas generator capable of generating fine bubbles has a special mechanism. It was confirmed that COD and SS can be purified simultaneously and continuously with high efficiency by using a liquid mixing device and introducing an oxidant into the device.

The present invention was developed on the basis of such knowledge, and the purpose thereof is to purify waste water which can be efficiently recycled to a recyclable state by a simple operation using a compact device. To provide a method.

[0006]

In order to achieve the above object, a method for purifying wastewater according to the present invention is provided with a plurality of impellers at the lower end of a rotary shaft which also serves as a ventilation pipe having an air intake hole at the top. A self-priming stirring type gas-liquid contactor having a structure in which a bubbling stirring means having a plurality of air ejection holes formed in the rotary shaft corresponding to the back surface of the impeller is installed in a waste liquid treatment tank is used. The constitutional feature is that the oxidizer is forcibly mixed with the spiral flow containing fine bubbles formed in the waste liquid treatment tank.

The object to be treated in the present invention is various wastewater containing COD and SS such as kitchen wastewater and industrial wastewater, and is not particularly limited. Specifically, for example, rice sharpening juice produced from restaurants and households, wastewater containing carbohydrates such as tableware residues, proteins, fats and oils components, cleaning wastewater containing surfactants such as cleaning agents, or factory equipment. Industrial wastewater containing organic compound components generated from

FIG. 1 is a schematic sectional view showing a self-priming stirring type gas-liquid contactor used in the present invention.
Is a bubbling stirring means attached to the waste liquid treatment tank 1, and 3 is an oxidant storage tank. The waste liquid treatment tank 1 is provided with a waste water introducing pipe 4 at the lower end, a foam discharge port 5 at the upper part, and a treatment liquid discharge port 6 at the upper side, and a foam discharge port for facilitating the separation of the foam as necessary. A baffle plate 7 and a shield plate 8 are attached to the lower surface of the plate 5. Furthermore, the waste liquid treatment tank 1 is connected to the oxidant storage tank 3 via a metering pump 9, and an inlet pipe 11 is attached so that the outlet 10 at the tip faces the tip of the bubbling stirring means 2. .

As shown in FIG. 2 (perspective explanatory view), the bubbling stirring means 2 is provided with a rotary drive motor 13 on the top of a rotary shaft 12 which also serves as a ventilation pipe, and a plurality of impellers 14 are installed on the lower end. In addition, a plurality of air suction holes 15 are provided in the upper part of the rotary shaft 12 (the lower part of the rotary drive motor 13) located outside the system of the waste liquid treatment tank 1, and the impeller 14
A plurality of air ejection holes 16 are formed on the side surface of the rotary shaft 12 corresponding to the back surface of the. According to this structure, when the rotary drive motor 13 is actuated, a negative pressure is generated in a portion of the impeller 14 that contacts the back surface in the rotational direction,
By this action, the air sucked into the rotary shaft 12 from the air suction hole 15 is self-sufficiently jetted into the vortex through the air jet hole 16. The jetted air is dispersed in the wastewater as fine bubbles of a few microns unit by the stirring action by the vortex flow and the shearing action of the impeller 14, and extremely efficient gas-liquid contact occurs.

The vortex flow containing the fine bubbles formed as described above is forcibly mixed with the oxidizer from the oxidizer storage tank 3 through the metering pump 9 and the feed pipe 11. As the oxidant, oxygen, ozone, an oxidizing gas such as air,
An oxidant aqueous solution in which one or more of sodium hypozincate, calcium hypochlorite, hydrogen peroxide, sodium persulfate, potassium permanganate and the like are dissolved can be used. The drug concentration when using an oxidizing agent aqueous solution is
Although it varies depending on the amount of COD components in the wastewater to be treated and the type of chemicals, the equivalent ratio to the COD amount is generally in the range of 1: 1-8, preferably 1: 2-6. Among these, an aqueous solution of sodium hypochlorite having an effective chlorine content of 10% by weight or more is most preferably used.

[0011]

According to the present invention, when the self-priming stirring type gas-liquid contactor having the above-mentioned structure is operated, micron-sized fine bubbles generated by the negative pressure on the back surface of the impeller and the rotary shearing action of the impeller are efficiently discharged into the waste water. It is well stirred and dispersed, and SS is easily attached and supported in the process of moving up the waste liquid treatment tank. In this way, the foam that has incorporated the SS component is continuously discharged, and the SS is effectively foam-separated. On the other hand, the COD component contained in the wastewater is oxidatively decomposed by the oxidizer forcibly mixed with the spiral flow containing fine bubbles, and is purified to be substantially detoxified. At the same time, the effect of lowering the chromaticity is brought about.

The above-mentioned foam separation and oxidative decomposition proceed concurrently in the same waste liquid treatment tank, and by this action, the removal of SS contained in the waste water and the decomposition of the COD component are carried out simultaneously.
Therefore, the water quality after treatment is purified to the extent that it can be recycled as wash water for toilets and the like. In addition, the self-priming stirring type gas-liquid contactor used in the present invention has a simple structure and can be designed in a relatively compact size, and the purification process can be carried out easily and continuously.

[0013]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples. However, the invention is not limited to these examples.

Example 1 A self-priming stirring type gas-liquid contactor 1 having the structure shown in FIG.
(Drainage treatment tank; width 25 cm x depth 20 cm x height 50 cm, internal volume; 25 liters) continuously flows kitchen wastewater with a COD content of 54 ppm, an SS content of 40 ppm and a pH of 7.3 from a waste liquid introduction pipe 4, The rotary drive motor 13 (200V, 2P, 30Hz, inverter control) of the bubbling stirring means 2 was operated to rotate the rotary shaft 12 at 2500 rpm. On this occasion,
The amount of air ejected from the air ejection holes 16 was 1.6 liters per 1 liter of waste water. At the same time, an aqueous sodium hypochlorite (manufactured by Junsei Chemical Co., Ltd.) aqueous solution containing 10% by weight of available chlorine was supplied from the inlet pipe 11 for purification treatment.

The COD, SS and transparency of each treatment liquid were measured, and the results are shown in Table 1 in comparison with the concentration of sodium hypochlorite aqueous solution (equivalent ratio to COD amount 1) and the liquid residence time in the apparatus. It was The COD and SS were measured according to JIS K0102 (hereinafter the same).

[0016]

[Table 1]

Comparative Example 1 1 liter of the same kitchen waste water as in Example 1 was placed in a flask equipped with a conventional rotary stirrer, the same sodium hypochlorite aqueous solution as in Example 1 was added, and the rotation speed was 300 rpm.
It was stirred at. The COD and SS amount after the treatment in this manner were measured, and the results are shown in Table 2 in comparison with the treatment time.

[0018]

[Table 2]

EXAMPLE 2 COD content of 13 ppm, SS content of 9 ppm,
Instead of the sewage secondary treated water having a pH of 7.1, other than that in Example 1
Wastewater purification treatment was performed under the same conditions as above. CO of treated water
D and SS were measured and the results are shown in Table 3.

[0020]

[Table 3]

Comparative Example 2 Example 2 was placed in a flask equipped with a conventional rotary stirrer.
The same sewage secondary treated water as 1 liter was added, the same sodium hypochlorite aqueous solution as in Example 1 was added, and the rotation speed was 3
Stirred at 00 rpm. CO after treatment in this way
The amounts of D and SS were measured, and the results are shown in Table 4 in comparison with the treatment time.

[0022]

[Table 4]

Example 3 Purification treatment was carried out under the same conditions as in Example 1 except that the treated liquid of kitchen wastewater having a chromaticity of 55 degrees was used as the treatment liquid and the concentration of the aqueous solution of sodium hypochlorite was 2.5 equivalents. Then, the degree of decrease in chromaticity was measured. The results are shown in Table 5. The chromaticity was measured according to JIS K0102 (Factory drainage test method).

[0024]

[Table 5]

Comparative Example 3 In a flask equipped with an ordinary rotary stirrer, 1 liter of the same kitchen wastewater biological treated water as in Example 3 was placed, and Example 3 was added.
The same sodium hypochlorite aqueous solution was added and stirred at a rotation speed of 300 rpm. In this way, the chromaticity after stirring for 10 minutes was measured. The results are shown in Table 6.

[0026]

[Table 6]

[0027]

As described above, according to the present invention, COD and SS contained in various wastewaters can be efficiently removed at the same time by a relatively compact device and simple operation, and the chromaticity can be lowered. Is possible. Therefore, for example, it is extremely useful as a treatment method for continuously detoxifying kitchen wastewater, secondary sewage treated water, pulp wastewater, etc. to a water quality that can meet environmental standards.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a self-priming stirring type gas-liquid contact device used in the present invention.

FIG. 2 is an enlarged perspective explanatory view of the bubbling stirring means in FIG.

[Explanation of symbols]

 1 Waste liquid treatment tank 2 Bubbling stirring means 3 Oxidant storage tank 4 Waste liquid introduction pipe 5 Foam discharge port 6 Treatment liquid discharge port 7 Baffle plate 8 Shield plate 9 Metering pump 10 Outlet port 11 Inlet pipe 12 Rotation shaft 13 Rotary drive motor 14 Impeller 15 Air inlet 16 Air outlet

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kenichi Kokubun 2-5-12 Higashi-Kanda, Chiyoda-ku, Tokyo Within Environmental Engineering Co., Ltd. (72) Noriyuki Komiya 2-5-12 Higashi-Kanda, Chiyoda-ku, Tokyo Environmental Engineering Co., Ltd.

Claims (2)

[Claims] 1. A plurality of impellers are installed at the lower end of a rotary shaft that also functions as a ventilation pipe having an air intake hole in the upper part, and a plurality of air ejection holes are provided in the rotary shaft corresponding to the back surface of the impeller. Using a self-priming stirring type gas-liquid contactor having a structure in which the bubbling stirring means is installed in the waste liquid treatment tank, the oxidizer is forcibly mixed with the swirl flow containing fine bubbles formed in the waste liquid treatment tank. A method for purifying wastewater, which is characterized in that 2. The method for purifying wastewater according to claim 1, wherein an aqueous solution of sodium hypochlorite is used as the oxidizing agent.