JPH07982A - Waste water treatment - Google Patents

Abstract

PURPOSE:To stabilize the treatment, to decrease the formed quantity of excess sludge, besides to save labor, to save resources and to save energy in biological treatment of waste water. CONSTITUTION:This is a method for treating waste water where an extract extracted from natural citrus fruits is added during a process for biologically treating waste water. The action of microorganisms participating in the purification of waste water is improved by the addition of the extract to form activated sludge rich in sedimentation property and concentration property. In this way, the effect of solid-liquid separation is increased to stabilize the treatment and the deterioration of the quality of the treated water due to sludge outflow is prevented and also the generated quantity of excessive sludge is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating wastewater by activating the activities of organisms involved in the purification of wastewater.

[0002]

2. Description of the Related Art When purifying organic waste water, a biological treatment method is widely adopted in which microorganisms are propagated under certain conditions to achieve a purifying action performed in nature in a short period of time. The activated sludge method is a typical treatment method. Bacteria and other organisms naturally occur in the wastewater. In the presence of oxygen by blowing air into the wastewater, this bacterium takes up organic matter in the surrounding wastewater, grows and reproduces, and forms a fine lump. Various aerobic microorganisms adhere to the surroundings of this lump, and these microorganisms also ingest fine suspended matter, soluble substances and bacteria in the wastewater as foods and propagate. Thus, a large number of microbial clumps are formed in the wastewater, which are cotton dust-like and are called flocs.
In other words, the organic pollutants in the wastewater turn into flocs by the action of microorganisms, and as a result, the wastewater is divided into flocs and clean water. Since this floc is generally heavier than water, when the mixed solution of flocs is left to stand, the flocs precipitate and clean supernatant water is obtained as treated water.
The settled hooks form sludge, which is essentially an accumulation of organisms and is a kind of living thing unlike ordinary sludge. Therefore, this sludge is particularly called activated sludge.
When this sludge is returned to the wastewater and mixed and contacted with the wastewater in the presence of an appropriate amount of oxygen, the pollutants are taken as food and work to remove the pollutants. The activated sludge that is returned to the wastewater is called return sludge. The above is the treatment principle of wastewater by the aerobic biological treatment method, and the treatment method using returned sludge is the activated sludge method. Wastewater treatment facilities using the activated sludge method generally have an aeration tank that biodegrades organic pollutants in the wastewater by mixing and contacting the wastewater with the activated sludge and oxygen, and the resulting sludge and supernatant water. It consists of a settling tank for separation. The activated sludge method is one of the most excellent biological treatment methods for highly treating organic wastewater, but it has the following fatal drawbacks. . That is, the deterioration of the settling property of activated sludge due to sudden shocks and changes in load conditions, and the deterioration of the treated water quality due to the sludge floating in the settling tank and being mixed with the discharged water and flowing out. It is no exaggeration to say that most of the money is spent on sludge management. In particular, the swelling of activated sludge often occurs at an unexpected time and has a fatal adverse effect on the treatment function. In the activated sludge method, no matter how excellent the biodegradation in the aeration tank is, if the solid-liquid separation in the sedimentation tank is poor, the sludge will flow out into the discharged water a lot and the water quality of the treated water will not deteriorate. further,
Concentration of the settled sludge will not be carried out well, the concentration of the returned sludge will be low, the concentration of activated sludge in the aeration tank will be low, and it will not be possible to retain useful microorganisms for wastewater treatment, and biodegradation will be reduced. Therefore, the quality of solid-liquid separation in the settling tank has a great influence on the degree of purification of wastewater. As measures against the deterioration of treated water quality due to such sludge outflow, conventionally, coagulants have been added to aeration tanks or settling tanks to increase sludge settling ability, or additional settling tanks or filtration devices have been installed. , Symptomatic treatment methods such as capturing the sludge that had flowed out were adopted. Further, a major drawback in maintaining the activated sludge method is that a large amount of surplus sludge is generated. Excess sludge is inevitably generated in biological treatment of wastewater, and is the residual sludge used as return sludge. This sludge has a high water content and poor concentration and dewatering properties, and the actual disposal cost of surplus sludge accounts for about half of the total cost required for wastewater treatment. Furthermore, this sludge easily decomposes and causes pollution such as offensive odors and hygienic pests. The volume of excess sludge greatly depends on the water content. For example, sludge with a water content of 99% is concentrated (dehydrated) and the water content is 98%.
If so, the capacity would be reduced to one half of that originally. Therefore, it is extremely important to obtain surplus sludge that is highly concentrated and has a low water content in order to reduce the disposal cost of surplus sludge. As a treatment method for activating microbial activity to reduce excess sludge, there is a method of administering a microbial agent such as bacteria or a microbial activity aid described in JP-B-63-65396 into an aeration tank. Biological treatment methods such as the activated sludge method utilize a wide variety of microorganisms in the Kunming culture system that spontaneously grew in the system, and it is an extremely complicated multi-component wastewater containing various components. In order to treat wastewater, the predominant species of microorganisms in the system vary depending on the wastewater substrate and other treatment conditions. Therefore, it is virtually impossible to control the biota in the system by administering the microbial agent, and its effect could not be expected. In addition, the method of administering a microbial activation aid described in JP-B-63-65396 is an effective main ingredient extracted from a special plant (soap tree) that grows naturally in Chile, Bolivia, Peru, etc. It is a method of administering an extract (soap solution) thought to be a saponin as a component. This method has been adopted in various fields of wastewater treatment and its effectiveness has been recognized, but an implementation report example “PPM, Vol.
No. 2 (published by Nihon Kogyo Shimbun) ”, this extract is expensive, so the cost of addition accounted for about 30% of the total treatment cost of wastewater treatment. It has only saved about 4% and has no significant economic effect.

[0003]

The method of adding a coagulant to an aeration tank or a sedimentation tank, which is adopted as a measure for preventing deterioration of the quality of treated water due to sludge outflow, is quick-acting, but when the addition is interrupted Since it returned to its original state, it was difficult to carry out stable wastewater treatment for a long period of time. In addition, this method has the drawback that the amount of excess sludge generated increases, and depending on the type and amount of coagulant used, it inhibits the growth and reproduction of microorganisms involved in the purification of wastewater, and There was a drawback that caused further deterioration. It is uneconomical in terms of cost to install an additional settling tank or install a filtering device, and this method cannot be adopted when the site for installation is restricted. The method of administering a microbial preparation to an aeration tank can hardly expect its effect, and the method of activating the activity of microorganisms by adding soap liquid to reduce the amount of excess sludge generated is Since the raw material is a plant that is produced in a specific area such as South America, the price of the product is high and the overall wastewater treatment cost has not been reduced as described above. For the above reasons, the present invention, in terms of sludge management, the stability can be secured by easier maintenance, the amount of surplus sludge generated is small, and the wastewater treatment cost is low, that is, economically. , To provide a highly efficient processing method.

[0004]

The present invention has solved the above problems and is as follows. The feature is that the extraction substance extracted from natural citrus fruits is added during the aerobic treatment process of waste water. The raw material of this extract is not only unevenly distributed in a specific area, but can be extracted from mandarin orange peel, etc.
It is easily and cheaply available in Japan. In addition, it is possible to effectively use the waste that is difficult to dispose of at the processing plant of canned tangerine and tangerine juice. This extracted substance is a kind of terpene that is naturally biosynthesized in a plant body by combining a plurality of isoprene. Terpenes are important pigments in animal and plant hormone components and photosynthesis, and are also used as fragrances. Extraction is usually obtained by steam distillation of fresh plant tissue. The tissue is mixed with water and distilled over steam throughout and the fraction is collected through a condenser. The distillate is a kind of oil and floats on the surface so that it can be easily separated. The main component effective for the wastewater treatment of this extracted substance is considered to be limonene, which is a monoterpene having a monocyclic structure with an orange scent. Since this extracted substance is difficult to dissolve in water, add a surfactant etc.,
It is preferable to use the one that is easily dissolved in water. The present invention is to add this extract material during the biological treatment process of wastewater, the addition of the extract material from aerobic biological treatment facilities such as aeration tanks and return sludge, or the discharge source of wastewater. It can be done anywhere to the treatment facility.
The amount of the extracted substance added varies depending on the organic matter component and concentration of the wastewater, the concentration and properties of the activated sludge, and is not constant, and is determined according to the characteristics of the wastewater and the sludge concentration (biomass) in the system. It is considered that the effect of the addition of the extract substance on the wastewater treatment is that the hormone component of the extract substance stimulates and activates the microorganisms involved in the purification of the wastewater to promote the growth and proliferation of the microorganisms. In addition, the extracted substance prepared by adding a surfactant or the like has a property of easily dissolving various poorly soluble substances such as polymer substances. From this, it is considered that it facilitates the reduction of the molecular weight of the hardly decomposable substance in the waste water and contributes to the promotion of the metabolic action of microorganisms.

[0005]

The wastewater treatment method according to the present invention only adds the step of adding the extraction substance extracted from natural citrus to the treatment step in the conventional biological treatment method, and involves alteration or modification of the conventional treatment facility. Not a thing. The extraction substance may be added manually or mechanically such as by using a pump.

[0006]

【Example】

Example 1 Activated sludge collected from a wastewater treatment facility of a broiler factory was conditioned with skim milk in each of three graduated cylinders each having a capacity of 1000 cc.
S) 6940 mg / l, initial organic suspended solids concentration (ML
(VSS) 5480 mg / l sludge was added and aerated using an air pump for tropical fish breeding, and once a day, the aeration was stopped, and this method and conventional method were allowed to stand for 30 minutes. The sludge volume ratio (SV value) after the precipitation was measured and compared. After the measurement of the SV value was completed, 100 cc of the supernatant water in the graduated cylinder was drawn out, and skim milk was dissolved in tap water to prepare the same amount of artificial wastewater (PH; 5.7, BOD; 3).
120 mg / l, COD; 766 mg / l, SS; 79
7 mg / l, total nitrogen; 126.3 mg / l, total phosphorus; 1
8.2 mg / l, normal hexane extract; 102.9
(mg / l) and the aeration operation was continued again. As the aeration condition, an air pump having an air discharge rate of 600 cc / min was used, and intermittent aeration was performed by alternately performing an aeration time of 30 minutes and an aeration stop time of 60 minutes. In the above operation, when the solid-liquid separation in the graduated cylinder progressed slowly and it was difficult to extract a predetermined amount of the supernatant water, the standing time was extended. In addition, in the example of the present method, after the artificial drainage was added,
A stock solution having the characteristics shown in Table 1 prepared by adding a surfactant to the extracted substance extracted from natural citrus is diluted with distilled water to 100%.
2 cc was added diluted with 00 times. In addition, in the conventional method 1 according to the conventional technique, after the artificial drainage was added, the stock solution of the soap solution was diluted 10000 times with distilled water to obtain 2c.
c, and the conventional method 2 does not add any substance other than artificial drainage.

[0007]

[Table 1] Table 2 shows SV values of Examples of the present method, the conventional method 1 and the conventional method 2, and FIG. 1 is a graph showing the SV values. From Table 2 and FIG. 1, when the present method, that is, the addition of the extraction substance extracted from natural citrus fruits, the sedimentation rate of sludge was higher than that of the conventional method (conventional method 1 and conventional method 2), and This indicates that activated sludge having excellent concentration properties was produced.

[0008]

[Table 2] The measurement of SV value was continued for 20 days, and when the measurement on the 20th day was completed by, the supernatant liquid after the precipitation was left standing was collected from each graduated cylinder, and the remaining mixed solution was tap water for water quality analysis. Activated sludge suspension (MLSS) and activated sludge organic suspension (MLVS)
It was used for the measurement of S). The BOD of the present method, the conventional method 1 and the conventional method 2 is 6 mg / l, respectively.
8 mg / l and 7 mg / l, COD is 6 respectively
It was mg / l, 6 mg / l, and 8 mg / l, and there was no significant difference in BOD and COD between this method and the conventional method. Regarding the properties of activated sludge, MLSS of this method, conventional method 1 and conventional method 2 are 7200 mg / l and 760, respectively.
0 mg / l and 9000 mg / l, MLVSS
Were 5300 mg / l, 5700 mg / l and 7900 mg / l, respectively. From the above, the ML of this method
SS was about 93% of conventional method 1 and about 80% of conventional method 2, and MLVSS of this method was about 93% of conventional method 1 and about 67% of conventional method 2. These facts indicate that the present method has a high reduction rate in both MLSS and MLVSS compared with the conventional method, that is, the present invention produces less excess sludge and produces activated sludge excellent in sedimentation and concentration. Means to provide a wastewater treatment method.

Example 2 The same sample used in Example 1 was used and 10
The sludge settling conditions of the present method and the conventional method on the days 15, 15 and 20 were measured and compared. The measurement method was performed by stopping the aeration air pump, leaving it to stand for 180 minutes, and recording the sludge surface height at which the interfacial sedimentation occurred during the time. Table 3 is this method, Table 4 is conventional method 1, and Table 5
Is the 10th, 15th, 20th day after the start of the treatment of the conventional method 2.
It shows the elapsed time on the day and the sludge height, and the elapsed time and the average sludge height. FIG. 2 is a sludge sedimentation curve showing the relationship between the elapsed time and the average sludge interface height in the present method, conventional method 1 and conventional method 2. From Table 3, Table 4, Table 5 and FIG. 2, the present method has a large reduction rate of the sludge surface height as compared with the conventional method, that is, the present invention produces activated sludge having excellent sedimentation and concentration properties. It has been found.

[0010]

[Table 3]

[0011]

[Table 4]

[0012]

[Table 5]

[0013]

EFFECTS OF THE INVENTION According to the present invention, activated sludge rich in sedimentation and concentration is produced, so that a large amount of biological sludge can be retained in the system, the diversity of biota becomes high, and the food chain becomes long. The rich diversity of biota shows high stability as an ecosystem and increased stability of biochemical reactions, and stabilizes the treatment effect in terms of water quality. In addition, as the food chain becomes longer, the number of organisms higher in the food chain, such as protozoa and metazoans, increases, and as a result of active predation and prey, the amount of excess sludge produced decreases. As described above, according to the present invention, since activated sludge having excellent sedimentation and concentration properties is generated, it is easy to prevent deterioration of treated water quality due to sludge outflow from the sedimentation tank, thus burdening maintenance work. It is possible to reduce the amount of wastewater and increase the treatment capacity by increasing the load of treated wastewater. INDUSTRIAL APPLICABILITY Since the present invention can be applied to a conventional treatment facility without any special modification or alteration, it can be easily applied to an existing facility that has a shortage of treatment capacity due to an overload of wastewater discharge amount or water quality. It is possible and is a very effective wastewater treatment method from the viewpoint of saving treatment cost, labor saving, resource saving and energy saving. In particular, the organic substance of the substrate is soluble, and further, it has a high application effect to the treatment of wastewater having a high content of carbohydrates and lower fatty acids, which is difficult to manage sludge such as wastewater from food factories. Further, since the raw material of the additive substance according to the present invention is natural citrus fruits, it can contribute to the effective use of wastes discharged from canned tangerines and juice processing plants.

[Brief description of drawings]

FIG. 1 is an SV value of Example 1.

FIG. 2 is a sludge settling curve of Example 2.

[Explanation of symbols]

 1 SV Value of the Present Invention 2 SV Value of Conventional Method 1 SV Value of Conventional Method 2 4 Sludge Settling Curve of the Present Invention 5 Sludge Settling Curve of Conventional Method 1 6 Sludge Settling Curve of Conventional Method 2

Claims (5)

[Claims] 1. A method for treating wastewater, which comprises adding an extraction substance extracted from natural citrus during the step of biologically treating the wastewater. 2. The wastewater treatment method according to claim 1, wherein the biological treatment step is performed by utilizing aerobic microorganisms. 3. The wastewater treatment method according to claim 1, wherein the extraction substance is added on the way from the drainage source to the wastewater treatment facility. 4. The wastewater treatment method according to claim 1, wherein the extraction substance is added in an aeration tank. 5. The wastewater treatment method according to claim 1, wherein the extraction substance is added to the returned sludge.