JPS6025587A - High-degree treatment of water - Google Patents

Abstract

PURPOSE:To prevent adsorbing capability of activated carbon from being lowered, by controlling ozone injection ratio on the basis of a detected value of the total amount of organic matters having a molecular weight of not less than 1,000 contained in water to be treated. CONSTITUTION:Water 1 to be treated which has been subjected to a biochemical treatment and separation by flocculation is fed into a receiving tank 2, and is supplied into a reaction tank 5 for ozone oxidation by a water pump 3 through a detector 4. The detector 4 detects the total amount of organic matters having a high molecular weight of not less than 1,000 contained in water to be treated with ozone. After an ozone injection ratio is determined by a calculator 6 on the basis of the value detected by the detector 4, ozone is fed from an ozonizer 7 into the reaction tank 5 through a diffuser pipe 8, and is brought into reaction with water to be treated through gas-liquid contact. The water thus oxidized by ozone is fed into a dissolved ozone decomposing tank 10, where unreacted ozone contained in the water is brought into self-decomposition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] This invention relates to a method for highly and effectively treating organic matter in water in sewage treatment facilities, human waste treatment facilities, and the like.

[Prior art and its problems]

In recent years, water quality in public water bodies such as rivers and lakes has become significantly polluted, causing various adverse effects. As a countermeasure for this,
Regulations on the total amount of COD (Chemical Oxygen Demand) have been in effect since 1981, and sewage treatment facilities, which are the source of upstream pollution,
This includes human waste treatment facilities, garbage treatment facilities, etc. Among these, sewage treatment facilities and human waste treatment facilities are said to have the greatest impact on water pollution in public water bodies, as they discharge a large amount of water and have a high concentration of organic matter expressed as COD etc. in the discharged water. ing. Moreover, in these facilities, the colored components and organic matter in the effluent must be removed to a low concentration level, since the effluent is colored and resembles sewage or human waste. In other words, there is an urgent need for advanced treatment of effluent water.

However, the conventional water treatment methods used in these facilities can be considered to be almost the same, and are not functionally sufficient. Figure 1 shows the flow of water treatment at a human waste treatment facility.
Using this, the current processing method and its problems will be explained below. First, the collected raw human waste undergoes a mechanical separation process to remove coarse dirt, and then is appropriately diluted with groundwater to facilitate subsequent treatment before flowing into the next biological treatment process. do. This dilution step does not exist in sewage treatment, and this is a major difference between sewage treatment and urine treatment. Recently, in order to reduce the amount of dilution water, non-dilution processing is also being considered. Now, in the water to be treated that flows into the biological treatment process, most of the organic matter, nitrogen, and phosphorus are removed by the action of microorganisms such as activated sludge. The total amount of organic matter is expressed as total organic carbon (hereinafter abbreviated as TOC) or COD, and TOC will be used in the following explanation. For reference, the concentration of organic matter (unit: mg/l) is on the order of two digits after the biological treatment process.

Next, the treated water that has passed the biological treatment process is discharged into rivers, lakes, etc. after undergoing a disinfection process using chlorine sterilization.

However, these treatment methods cannot remove organic coloring components, and suspended substances float in the effluent, worsening the appearance of the effluent. With the current state of single-level treatment methods and the strengthening of the aforementioned legal regulations, there is a growing demand for higher-level treatment methods that can reduce the concentration of organic matter to a single digit. The advanced treatment methods are mostly physicochemical treatment methods, and typical examples include coagulation separation method, filtration method, and ozone oxidation method.

Activated carbon adsorption methods are available. Therefore, some of the processing facilities are adding these advanced processing processes to existing processes, as shown in FIG.

In particular, when the goal is to remove organic substances and organic coloring components to a high degree, for example, to reduce the TOC to 10 mg/L + chromaticity of 20 degrees (to the extent that it is almost impossible to tell whether or not it is colored). , ■The combination method of coagulation separation and ozone oxidation, and the combination method of coagulation separation and activated carbon adsorption are superior in terms of treated water quality.

By the way, although the above-mentioned two methods are excellent in processability, there are major problems in terms of maintenance and operability as shown below. First, a common problem is that in order to effectively perform coagulation and separation, the amount of chemical injection must be increased, and at the same time, the amount of coagulated and separated sludge and the amount to be disposed of increase accordingly. Further, this is not preferable not only because of an increase in running costs but also from the viewpoint of operability such as transportation of sludge. Next, focusing on the individual treatment methods, although this also relates to running costs, method (2) has a low ability to remove organic matter in ozone oxidation treatment. The problem is that it has to be increased. Figure 3 shows the results of oxidation treatment of flocculated and separated water at a certain human waste treatment facility.
C indicates that only about 20 inches are removed. On the other hand, the above-mentioned method (2) has the problem that since the adsorption capacity of organic substances such as TOC to activated carbon is small, a large-capacity adsorption tower is required for its treatment.

As a method to compensate for the shortcomings of these two treatment methods, a combination treatment method is known in which coagulation separation, ozone oxidation, and activated carbon adsorption are performed after the biological treatment step.

Conventionally, in the ozone oxidation step in this treatment method, the ozone injection rate was kept constant, so there was a problem that the activated carbon adsorption performance deteriorated due to fluctuations in the total amount of organic matter in the water to be treated.

[Purpose of the invention]

This invention was made in view of the above-mentioned problems, and is a method for highly treating waste water by a treatment method that includes an ozone oxidation step and an activated carbon adsorption step, regardless of fluctuations in the total amount of organic matter in the water to be treated. The purpose is to provide a stable, high-performance advanced treatment method that does not reduce activated carbon adsorption performance.

[Key points of the invention]

This invention provides a detection unit for calculating the total amount of high molecular weight organic matter contained in the water to be ozonated when performing advanced treatment of water, and performs the treatment while controlling the ozone injection rate based on the detected value. By doing so, the above objectives are achieved. In other words, the present invention is capable of carrying out the oxidation treatment using ozone as well as the subsequent activated carbon adsorption step without reducing the adsorption properties. The term "high molecular weight" means a molecular weight of 1000 or more, although it differs slightly depending on the type of biologically treated water.

[Embodiments of the invention]

FIG. 4 shows a system diagram showing an embodiment of the present invention. The water to be treated (flocculated water) l that has gone through the biological treatment process and the flocculation separation process (not shown) is once transferred to the receiving tank 2. After flowing into the water pump 3, the water is supplied to the ozone oxidation reaction 4115 via the water detector 4.

Here, the detector 4 measures the total amount of high-molecular-weight organic matter, which usually has a molecular weight of 1000 or more, contained in the water to be ozonated. It also has the function of calculating the proportion of organic matter. For example, this detector is a measuring device that calculates the amount of organic matter in the fractionated water of organic matter with a molecular weight of 1000 or more using a TOC analyzer after fractionating the molecular weight of organic matter in water using a liquid chromatograph. It is.

In the reaction tank 5, a calculator 6 is used based on the value determined by the detector 4.
After the dioscin injection rate is determined, a predetermined amount of ozone flows from the ozone generator 7 through the aeration pipe 8 at the bottom of the reaction tank 5, and causes a gas-liquid contact reaction with the water to be treated. At this time, unreacted ozone in the gas phase is treated by the exhaust ozone treatment device 9 and then released into the atmosphere. The water to be treated that has been oxidized by ozone in the reaction tank 5 is then transferred to the dissolved ozone decomposition tank 10.
flows into. Here, unreacted dissolved ozone contained in the water self-decomposes and disappears while the water to be treated remains for a predetermined period of time. Furthermore, the water to be treated overflows from the dissolved ozone decomposition tank 10 and flows into the receiving tank 11, and then is continuously supplied by the water pump 12 to the adsorption tower 13 filled with activated carbon, where it is treated. After that, it is subjected to a chlorine sterilization process (not shown).

The ozone injection rate is controlled within the optimum control range based on the results of experiments conducted by the present inventors and shown in FIG. Figure 5 shows TOC as an indicator of the total amount of organic matter contained in ozonated water.
TO (41
This is a measurement of the degree of From this result, the ratio is 0.5
~4.077) range, the TOC after the adsorption step is 10 mg.
It can be seen that / can be made below, which is the optimal control range.

An example of the results of the processing performed based on the processing flow described above will be explained in comparison with the conventional technique using FIGS. 6 and 7.

To explain the treatment process and conditions shown in Figure 6, the biologically treated water that has undergone the biological treatment process is used as raw water, and after flocculation separation under standard treatment operating conditions, three types of 70
- A, B, and C were treated separately and a comparative experiment was conducted. In Flow A, the coagulated and separated water is oxidized at an ozone injection rate of 20 mg/A, which is within the optimal control range of the 7 zones mentioned above, and then the water is continuously passed through an activated carbon adsorption tower for treatment. It is something that On the other hand, in Flow B, the same coagulated and separated water was oxidized at a higher ozone injection rate of 40 mg/l than in Flow A, and then subjected to the same treatment as in Flow A. In Flow ○, the coagulated and separated water was directly guided to the adsorption tower for treatment. The processing results in this experiment are shown in FIG.

The TOC concentration in FIG. 7 is the value of treated water in each step when continuous treatment was performed for -month. According to FIG. 7, in flow A of Jin's invention, the TOC concentration is in the single digits.
It can be seen that organic matter can be removed to a high degree with mg/L. In flow B, T of the adsorbed treated water flowing into the adsorption tower
Although the OCQ degree is the lowest, the TOC concentration of the treated water that has not undergone the subsequent adsorption process is the highest. In other words, in a method that adds the ozone oxidation and activated carbon adsorption steps in series, such as the combination method, unnecessarily increasing the ozone injection rate will reduce the adsorption of organic matter to activated carbon in the subsequent adsorption step. It shows that it decreases. The reason for this is that at low ozone injection rates, high-molecular-weight organic substances that are difficult to adsorb can be converted into low-molecular-weight organic substances that are highly adsorbable; This is due to the decomposition of organic matter, leading to a decrease in adsorption properties.

Figure 8 shows this in detail, and shows the ratio of adsorption capacity (adsorption amount of organic matter per unit of activated carbon, mass) of adsorbed treated water fractionated into three molecular weight ranges before and after ozone oxidation treatment. It represents. The ratio is 1 when ozone oxidation treatment is not performed. A value of 1 or more indicates that the subsequent adsorption property is improved by performing the ozone oxidation treatment. Focusing on 70-B in Fig. 8, it is shown that excessive oxidation treatment reduces the adsorption capacity of organic matter with molecules less than z 1 o o o to activated carbon, thereby reducing the overall adsorption performance. ing. Therefore, in ozone oxidation treatment, it is necessary to treat high molecular weight organic substances with a molecular weight of 1000 or more using an appropriate ozone injection rate. Furthermore, the molecular weight fractionation range can be further divided, but for practical purposes, the range shown in FIG. 8 is sufficient. The fractionation shown in FIG. 8 was performed by gel chromatography.

In the same experiment, the coagulation separation operation was performed by adding 300 mg/g of industrial aluminum sulfate solution to the test water as a coagulant.
L. After injecting 1 mg/l of an anionic polymer as a flocculation aid and flocculating it, it was introduced into a solid-liquid separation tank with a sedimentation time of 30 minutes for treatment. The water flow rate of the adsorption tower is 2m/
I laughed under the terms of HR.

Furthermore, with regard to the flow control system according to the present invention shown in FIG. 6, FIG. 9 shows the results of an experiment regarding the relationship between the number of days water is passed through the adsorption tower, TOolM, and degree. It can be seen that this allows highly treated water with a low concentration to be obtained with a stable activated carbon regeneration interval of about 30 days.

The principle of this invention and the related method for determining organic matter in treated water, that is, biologically treated water, will be explained in more detail. First, attempts have been made primarily from the standpoint of analytical chemistry to understand organic matter in biologically treated water as a group of organic matter that has the same properties as those originally contained in water. ing. There are two approaches. - is a method that measures proteins, amino acids, sugars, etc. that are thought to be contained in biologically treated water, and classifies and understands these organic substances organically. The Mop method is a method that uses an analytical device such as a liquid chromatograph to fractionate organic substances in water based on differences in molecular weight, and attempts to determine the characteristics of a group of organic substances from the pattern of the molecular weight distribution. These two methods have advantages and disadvantages, but from the standpoint of water treatment, the information obtained by the latter is more useful.
In physicochemical treatments such as ozone oxidation and activated carbon adsorption, information on the molecular weight is considered to be valuable because the molecular weight of the substance to be treated that is generally contained in water is the most likely to affect the processability.

However, conventionally, in the above-mentioned physicochemical treatments, information regarding molecular weight has not been used for purposes such as determining the operating conditions of the treatments. For example, in decolorizing treated human waste water, which is a typical example of oxidation treatment using ozone, a method is used in which the chromaticity of the water to be ozonated is determined in advance and the ozone injection rate is controlled based on this value. ing. In this case, the chromaticity, m= of a type of material to be treated, is simply used as an index for controlling the operating condition of the ozone injection rate. Furthermore, to add more information about the chromaticity of the human waste treated water, the colored components are bile pigments contained in the human waste and humic substances newly generated by the decomposition of organic matter in the human waste through biological treatment. Furthermore, our research has revealed that the molecular weights of these coloring components are widely distributed and that these two substances are not simple substances. Therefore, in decolorizing by ozone oxidation alone or in combination with coagulation separation and ozone oxidation, it is more appropriate to use chromaticity as a control index rather than the molecular weight of the coloring component.

However, the combination method! When removing organic matter to a high degree, the coloring component is only a part of the organic matter, so the chromaticity of the ozone oxidation process cannot be used as an index for controlling the ozone injection rate. Furthermore, performing oxidation treatment focusing only on chromaticity tends to result in excessive treatment, which is not economical and also reduces the organic matter to an excessively low molecular weight, resulting in a decrease in adsorption as shown in FIG.

Therefore, in this invention, in addition to removing colored components and other substances using the above-mentioned treatment method, organic substances with a molecular weight of 1000 or more contained in temporary ozonated water are detected in advance, and ozone is injected based on the detected value. By having the principle of controlling the rate and performing appropriate fermentation treatment, problems such as a decrease in adsorption in the adsorption process can be solved.

In the above description, the application of advanced treatment of biologically treated water such as human waste treated water has been explained, but the present invention can also be applied to the field of waterworks in addition to the above.

Currently, water supplies are facing problems with the production of carcinogenic substances such as chloroform and the production of strange odors and tastes. This is because the biologically treated water flows into water sources such as rivers, lakes, and marshes, and the water quality of these water sources deteriorates.

Therefore, the organic matter present in water from tap water sources is similar to that in biologically treated water, and as a countermeasure, it is necessary to add an ozone oxidation process or an activated carbon adsorption process to the existing process shown in Figure 10. is possible. Figure 11 and 1
Figure 2 is a water purification process diagram that is expected to be particularly adopted in the future. 10 to 12 will be explained below. Figure 10 shows a standard water purification process. Raw water taken from a water source such as a river is stored in a reservoir, then disinfected in a pre-chlorination process, and then flows into the coagulation separation process. . Here, suspended organic matter is mainly removed from the water to be treated. Next, the water to be treated undergoes disinfection treatment again in a post-chlorination disinfection step, and then is supplied to water service users via a water distribution reservoir or the like.

However, since the water purification process shown in FIG. 10 cannot deal with the above-mentioned problems, the water purification processes shown in FIGS. 11 and 12 are considered. In FIG. 11, the pre-chlorine disinfection step in FIG. 10 is changed to a pre-ozone disinfection step, and an activated carbon adsorption step is further incorporated after the coagulation separation step. Moreover, in FIG. 12, the pre-chlorine disinfection step is abolished and a medium ozone disinfection step is provided after the coagulation separation step, and the position of the activated carbon adsorption step is the same as in FIG. 11. Both Figures 11 and 12 show that dioscin is used instead of chlorine in the water disinfection process, and that an activated carbon adsorption process is arranged in the subsequent process to finish the water treatment. Therefore, even though the field of application is different from human waste treatment facilities, this invention can be fully applied to the field of waterworks as it has the same functionality.

〔Effect of the invention〕

According to this invention, in an advanced water treatment method having an ozone oxidation step and an activated carbon adsorption step, the ozone injection rate is controlled based on the detected value of the total amount of organic matter with a molecular weight of 1000 or more contained in the water to be ozonized. Therefore, it is possible to provide a stable advanced treatment method in which the activated carbon adsorption performance does not deteriorate regardless of fluctuations in the total amount of organic matter in the water to be treated.

[Brief explanation of drawings]

Figure 1: Standard treatment process diagram at a human waste treatment facility; Figure 2:
The figure is a processing process diagram with the advanced treatment process added to Figure 1.
Fig. 3 is an example of ozone treatment results, Fig. 4 is a system diagram of an embodiment of the present invention, Fig. 5 is a diagram showing the control range of the optimum ozone injection rate, and Fig. 6 is a process of the present invention and prior art. Experimental comparison process chart, Figure 7 shows a comparison of the experimental results in Figure 6, Figure 8 shows the analysis results to explain the experimental results in Figure 7, Figure 9 shows another experimental result of this invention, and Figure 10. 1 is a standard water purification process diagram for waterworks, and FIGS. 11 and 12 are diagrams showing an embodiment of the present invention for waterworks.

Claims (1)

[Claims] 1) In a water treatment method having an ozone oxidation step and an activated carbon adsorption step, the ozone injection rate is controlled based on the detected value of the total amount of organic matter having molecules of 11,000 or more contained in the water to be ozonized. Features: Advanced water treatment method. 2. The advanced water treatment method according to claim 1, characterized in that the ratio between the ozone injection rate and the total amount of organic matter with a molecular weight of 1000 or more is controlled in the range of 0.5 to 4.0. Advanced water treatment method.