JP2638726B2 - Ozone injection control method for low-temperature water treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ozone injection control method for treating activated coke oven water with activated sludge and then treating the treated water with ozone to efficiently reduce COD in the treated water. .

[0002]

2. Description of the Related Art In recent years, in order to reduce or eliminate water pollution in rivers, lakes, marshes, shores, etc., as one step of a water treatment process such as vertical water treatment, human waste treatment, industrial wastewater treatment, etc., which is an upstream pollution source. It is known to inject ozone for the purpose of sterilization, decomposition of organic substances, decolorization, deodorization and the like.

[0003] For example, Japanese Patent Application Laid-Open No.
In the water treatment in which the treated water after the biological treatment step is subjected to the combination of the ozone oxidation treatment step and the activated carbon adsorption step, the ozone injection rate is determined by the detection value of the total amount of organic substances having a molecular weight of 1000 or more contained in the ozonized treatment water. It is disclosed that the control is performed as follows.

[0004] This technique is a treatment method in which activated carbon adsorption performance does not decrease irrespective of fluctuations in the total amount of organic matter in the water to be treated.

Japanese Patent Application Laid-Open No. 61-090789 discloses that when water is treated with ozone, the ozone absorption rate varies depending on the supplied ozone concentration instead of the conventional concentration control method. An ozone treatment method that stabilizes ozone absorption efficiency by controlling either one of the ozone concentration and the supply amount to a constant value and controlling the other to a variable value according to the supply amount control method when the control range is exceeded is disclosed. doing.

Japanese Patent Application Laid-Open No. 60-168590 discloses that when controlling the injection of ozone using a conventional TOC (total organic carbon) concentration or chromaticity as a parameter in controlling the injection of ozone in a water purification process, the concentration or chromaticity wavelength of the ozone is controlled. Therefore, the flow rate and TOC of the water to be treated are measured, and the ozone injection amount is set so that the ratio of the ozone consumption to the TOC of the water to be treated is maintained at a predetermined reference value, for example, 1.0 to 1.2. Are disclosed.

[0007]

As is well known, a large amount of coke oven water is generated, and various organic substances, inorganic substances, suspensions, and pigment components are dissolved and suspended in the water. Therefore, advanced water treatment technology is required.

The general treatment of coke oven water is activated sludge, sedimentation separation, chemical addition, coagulation separation, or water treatment combining this with adsorption and filtration. Had to be changed.

Therefore, it is desired to simplify the processing steps in order to increase the capacity in a limited facility space.

[0010] As a corresponding technique, activated coke oven water is subjected to activated sludge treatment, and then ozone is injected into the treated water to oxidize the treated water to decompose and decolorize pigment components and oxidatively decompose organic matter to a higher degree, thereby reducing COD (chemical deodorization). (Required oxygen demand) can be considered.

However, the activated sludge treatment of the coke oven water is a biological treatment, so that if the coke production conditions fluctuate, for example, due to a change in coal brand, etc., the fossil water component fluctuates, resulting in a change in nutrient status and activation. Sugars are formed around the sludge cells and their buoyancy fluctuates, or they overproliferate due to temperature, water temperature, and other conditions and partially deplete in oxygen. It is unavoidable that the activated sludge or sludge flows in and the concentration of the suspended matter changes suddenly.

This problem can be solved by adding a filtration tank, but adding a filtration tank goes against simplification of processing equipment.

[0013] Further, ozone has a problem that the cost of oxygen as a raw material is very high or requires a high voltage for ionizing it, so that the cost is high. The fact is that it is hardly applied to the concentration and the large amount of treated water.

In order to reduce COD in the coke oven water by a treatment process comprising activated sludge and ozone oxidation, various kinds of organic substances, inorganic substances or suspended substances existing in the water to be treated are taken into consideration, and the minimum amount is taken into consideration. Ozone needs to be injected properly.

Further, it is desired to be able to appropriately cope with component fluctuations in the above treated water, especially fluctuations in the concentration of the suspension (SS).

In order to solve the above problem, the above-mentioned known example, for example, Japanese Patent Application Laid-Open No. 60-025587, discloses that the total amount of organic substances is
The molecular weight was fractionated by liquid chromatography, and the molecular weight was 10
This method controls the ozone injection rate based on an analysis method that separately measures the amount of organic matter in the fractionated water of organic matter of 00 or more, which not only requires expensive analysis equipment but also makes the measurement intermittent. If the amount of organic matter in the treated water changes suddenly, there is a problem that the countermeasures are delayed, and if the concentration of the suspended solids in the treated water changes suddenly, it is no longer possible to respond.

This sudden change in the concentration of the suspension cannot be dealt with in JP-A-61-090789 and JP-A-60-168590 because of the reduced controllability.

[0018]

SUMMARY OF THE INVENTION The present invention relates to a method for reducing the COD of treated water by treating the treated water with activated sludge and then treating the treated water with ozone. The suspension concentration and the transparency were measured, and based on 150 ppm of the suspension concentration measurement value, when the measured value was 150 ppm or more, ozone was supplied at a predetermined ratio between the suspension concentration and the ozone injection amount. Addition control, the measured value is 150 ppm
In the case of less than the above, there is provided an ozone injection control method for a water treatment facility, wherein ozone is added and controlled at a predetermined ratio between the degree of visibility and the amount of injected ozone.

Further, in the present invention, the ratio of the above-mentioned suspension concentration and the amount of injected ozone is in the range of 0.5 to 0.7, and the ratio of the transparency and the amount of injected ozone is in the range of 0.2 to 0.4. 3. The method for controlling ozone injection of a safe water treatment facility according to claim 1, wherein:

[0020]

[Action] Most of the suspended solids (SS) in the treated water after the activated sludge treatment of coke oven water is composed of activated sludge and its dead bodies, and its composition is composed of proteins, glucose, etc. A part of this suspension is also a COD source. The component composition and the concentration of the suspension may vary greatly depending on the activated sludge equipment state and the coke oven operating conditions.

As described above, the amount of C
In order to effectively reduce OD, it is necessary to simultaneously and efficiently decompose and remove the suspended matter and dissolved organic matter.

The present invention focuses on the selective reactivity of suspended matter with ozone in a certain range of treated water after activated water has been treated with activated sludge, and has completed an ozone injection control method in consideration of suspended matter. .

FIG. 1 shows the concentration of suspension (SS) in treated water and C
The relationship between OD concentrations is shown. When the concentration of the suspension in the treated water is 150 ppm or more, a correlation between the concentration of the suspension and the value of COD is recognized, indicating that the suspension is preferentially oxidatively decomposed and COD is reduced.

In the region where the concentration of the suspended solid is less than 150 ppm, the relationship between the concentration of the suspended solid and the COD value varies.

This is considered to be due to the fact that the components of the suspension are changed and are in the form of an organic substance which does not contribute to COD.

FIG. 2 shows the relationship between the COD concentration and the transparency indicating the coloring components in the treated water in the region where the concentration of the suspension is less than 150 ppm.

As is clear from the figure, in this range,
There is a correlation between the COD value and the degree of transparency representing the coloring component, and the organic substance serving as the coloring component is preferentially decomposed from the suspension to reduce COD.

In addition, 150 ppm of the above-mentioned measured concentration of the suspension
When the measured value is 150 ppm or more, the ratio between the preset suspension concentration and the ozone injection amount is 0.5 to
At 0.7, the addition of ozone is controlled.

When the ratio of the above-mentioned suspension concentration and the amount of injected ozone is less than 0.5, even if the amount of ozone required for oxidative decomposition of the suspension is satisfied by the selective reaction, the amount of ozone required for oxidative decomposition of the coloring component is reduced. Run short.

On the other hand, if it exceeds 0.7, the amount of waste ozone increases and the load of ozone treatment and the cost increase, which is not appropriate.

The measured value of the concentration of the above-mentioned suspension is 150 pp.
If it is less than m, ozone is added and controlled within a range of a predetermined ratio between the visibility and the ozone injection amount of 0.2 to 0.4.

When the ratio between the transparency and the ozone injection amount is 0.2
If it is less than the required value, the amount of ozone required for the oxidative decomposition of the suspension will be insufficient even if the amount of ozone required for the oxidative decomposition of the coloring component is satisfied.

On the other hand, if the ratio exceeds 0.4, the amount of waste ozone increases, and the load and cost for ozone treatment increase, which is not appropriate.

The concentration of the suspended matter and the degree of transparency of the water to be treated after the activated sludge treatment are measured using a suspended matter concentration meter and a transparency meter. Uses a continuous measuring device.

The concentration of the suspension can be measured by, for example, irradiating the treated water flowing in a pipe through which light passes with infrared rays and measuring the concentration of the suspension from the reflectance.

Further, as the permeation meter, it is possible to use a permeation meter that transmits light to treated water flowing in a pipe through which light passes, and measures the transmittance based on the attenuation rate of light.

The specifications of these suspension densitometers or fluorometers are not particularly limited, and they may be any measuring instruments capable of continuously measuring the concentration and the transparency of the suspension.

It should be noted that a chromaticity meter using a specific wavelength is not preferable as a measuring means because it is affected by the absorption capacity of a specific substance.

Hereinafter, the present invention will be specifically described with reference to the drawings.

FIG. 3 shows a schematic flow chart of a coke oven water treatment system to which the present invention is applied.

The low-temperature water generated in the coke oven is introduced into the activated sludge treatment tank 1, where most of organic substances such as phenol and amines are oxidatively decomposed and detoxified by microorganisms, and most of nitrogen and sulfur are removed. This treated water is led to the settling tank 2 to separate sludge and treated water.

The sludge separated from the treated water is returned to the activated sludge treatment tank 1 via the sludge pipe 3.

On the other hand, the properties of the treated water tend to be unstable depending on the state of the activated sludge, and may vary greatly depending on the raw coal blending conditions and dry distillation conditions.

The activated sludge which is generated depending on the state of the activated sludge or is suspended from the sedimentation tank 2 due to flocking phenomenon or the like.

COD while responding to the change in the concentration of the suspension
In order to satisfy the standards for the amount and the SS amount, it is important to measure the concentration of the suspended matter and the degree of transparency and add ozone in an amount corresponding to the measured value.

The treated water separated in the sedimentation tank 2 is continuously measured by the suspended matter concentration meter 4 and the permeation meter 5 in the course of its movement.

The measured values of the concentration of the suspended solids and the degree of transparency are input to the arithmetic and control unit 7, and the operation valves 9, 10 for adjusting the amount of oxygen generated from the oxygen generator 8 and the amount of ozone generated from the ozone generator 10. When the measured value is 150 ppm or more, the ozone injection amount of the treated water into the ozone reactor 6 is set to 150 ppm or more, and the ozone injection amount is set at a preset ratio between the ozone injection amount and the suspension concentration. Ozone addition control is performed, and when the measured value is less than 150 ppm, ozone addition control is performed at a predetermined ratio between the degree of transparency and the ozone injection amount.

The water treated by the ozone reactor 6 is C
The concentration is monitored by the OD meter 12 and fed back to the controller 7 based on the concentration. The ratio between the suspension concentration and the ozone injection amount is in the range of 0.5 to 0.7, and the ratio between the transparency and the ozone injection amount. Can be finely adjusted in the range of 0.2 to 0.4.

[0049]

EXAMPLES Table 1 shows the results of applying the present invention to the coke oven water having a COD of 135 ppm and 64 ppm after treatment with activated sludge using the treatment equipment shown in FIG.

As ozone, ozone having a concentration of 4% was used. The ozone reactor 6 of the treated water is provided with a stirring blade, and the number of revolutions and the flow rate are controlled so that the total mass transfer capacity coefficient of ozone is 600 l / h.

FIG. 4 shows the transition of the ozone treatment result, and the COD of the discharged treated water can be stably controlled to 50 ppm or less.

[0052]

[Table 1]

[0053]

According to the present invention, the ozone is supplied at a predetermined ratio between the concentration of the suspended solid and the amount of injected ozone or the ratio between the transparency and the injected amount of ozone, based on the specific value of the concentration of the suspended solid in the treated water. Since the addition is controlled, the oxidation treatment can be performed with the optimal ozone injection amount, and the COD concentration and the SS concentration can be effectively reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the concentration of a suspension (SS) in treated water and the concentration of COD.

FIG. 2 is a graph showing the relationship between the visibility and the COD concentration of the coloring components in the treated water in the region where the concentration of the suspension is 150 ppm.

FIG. 3 is a schematic flow chart of a coke oven water treatment system to which the present invention is applied.

FIG. 4 is a transition diagram of an ozone treatment result.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Activated sludge treatment tank 2 Sedimentation tank 3 Return sludge piping 4 Suspended matter concentration meter 5 Permeability meter 6 Ozone reactor 7 Operation control unit 8 Ozone generator 9 Operating valve 10 Ozone generator 11 Operating valve 12 COD meter

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location C02F 9/00 504 C02F 9/00 504C (72) Inventor Shoichi Yamaguchi 5-3 Tokaicho, Tokai-shi New Nippon Steel Corporation Nagoya Works (72) Inventor Hiroshi Muto 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technology Development Division (56) References JP 50-149141 (JP, A)

Claims (2)

(57) [Claims] Claims 1. After activated coke oven water is treated with activated sludge,
When reducing the COD in the treated water by ozone treatment of the treated water, the suspended matter concentration and the transparency of the treated water after the activated sludge treatment are measured, and the suspended matter concentration measured value of 150 ppm is used as a reference, When the measured value is 150 ppm or more, ozone addition control is performed at a preset ratio of the suspended solid concentration and the ozone injection amount, and when the measured value is less than 150 ppm, the predetermined transparency and the ozone injection amount are determined. An ozone injection control method for a water treatment facility, characterized in that ozone is added and controlled in a ratio. 2. The method according to claim 1, wherein the ratio between the suspension concentration and the ozone injection amount is 0.5 to 0.7, and the ratio between the transparency and the ozone injection amount is 0.2 to 0.4. Claim 1
The ozone injection control method of the water treatment equipment according to the above.