WO2005077839A1

WO2005077839A1 - Method for treating organic wastewater

Info

Publication number: WO2005077839A1
Application number: PCT/JP2004/001563
Authority: WO
Inventors: Hideyuki Nakashima; Takashi Yamada
Original assignee: Asahi Organic Chemicals Industry Co., Ltd.
Priority date: 2004-02-13
Filing date: 2004-02-13
Publication date: 2005-08-25

Abstract

A method for treating an organic wastewater, which comprises maintaining the concentration of at least one of pyroligneous acid, a polyphenol, an organic acid and a metal salt of an organic acid in a reaction vessel (A) of an activated sludge process apparatus at a level of 1 ppb to 100 ppm. The method allows the elongation of the life of a filtration film (5) being used in an activated sludge process apparatus and also the reduction of the amount of generation of an excess sludge.

Description

Description Organic wastewater treatment method

The present invention relates to a method for treating organic wastewater such as domestic wastewater, livestock wastewater, fishery processing wastewater, or various kinds of industrial wastewater. More specifically, treatment of organic wastewater using an activated sludge treatment device that has a reaction tank that treats organic wastewater with microorganisms and a filtration membrane that separates the suspension after the reaction treatment into treated water and a concentrated liquid About the method. Background art

Conventionally, methods for treating organic wastewater using a filtration membrane include immersing the filtration membrane in a reaction tank, separating the suspension after the reaction into treated water and a concentrated liquid using a filtration membrane, and Although some of the concentrated liquid separated in the filtration membrane is returned to the reaction tank, basically, as shown in Fig. 4, the organic wastewater 16 is pre-treated via a pipeline. The mixture is introduced into the process 17, passed through a flow control tank (not shown), and introduced into the reaction tank 18. The suspension in the reaction tank is converted into sludge 24 and filtered water 23 by the filtration membrane 20. Solid-liquid separation is performed. The filtered water 23 is disinfected in the disinfection tank 19 and released into rivers, etc., and the sludge 24 accumulated in the reaction tank 18 is replaced with excess sludge 25 so that the sludge concentration in the reaction tank is maintained. After passing through the sludge concentration tank 21, it is held in the sludge storage tank 22, and then is carried out of the system. However, in the process of microbial treatment of organic wastewater, sugars, proteins, nucleic acids, etc., produced by microorganisms become viscous polymers, which cause clogging of the filtration membrane surface and clogging in pores of the membrane. This is the cause of the problem. As a result, a certain amount of treated water cannot be discharged, and the suspension in the reaction tank may carry over. The solution is to replace the membrane, but it costs Big and problematic. Various cleaning methods have also been devised to remove the polymer adhering to the membrane, but this method is intended to remove the residue in organic wastewater, which is a cause of preventing the membrane from blocking the filtration channel. This has not been solved.

In the biological treatment of organic wastewater, microorganisms such as bacteria, fungi, and protozoa take up organic matter as nutrients and purify while repeating the growth of these microorganisms. Will occur.

The generated sludge itself is a source of foul odors and is difficult to use secondaryly.Therefore, it is difficult to secure excess sludge disposal sites, increase the cost of disposal, and degrade the environment due to the disposal of disposed sludge. It is a problem. Furthermore, when dewatered sludge is incinerated, it causes a decrease in the temperature of the incinerator, which may cause the generation of dioxin.

As described above, the conventional organic wastewater treatment apparatus using a filtration membrane has problems in that the maintenance and management costs are high and excess sludge is generated in large quantities.

The present invention has been made in view of the above-described problems, and an object of the present invention is to extend the life of a filtration membrane used in an activated sludge treatment apparatus and greatly reduce the amount of excess sludge generated. To provide a method for treating organic wastewater.

Disclosure of the invention

In view of the situation of the prior art as described above, as a result of various studies, the present inventor has found that at least one compound of wood vinegar, polyphenols, organic acids, and metal salts of organic acids is 1 ppb- The microorganisms are activated by maintaining the concentration at 100 ppm, and the activated microorganisms decompose the polymer, whereby the permeability of the suspension through the filtration membrane is improved, and as a result, the membrane life is extended. I found it to be longer. In addition, activated microorganisms are extinguished by the cellular mechanism called autooxidation, and the resulting excess sludge is greatly reduced. The inventors have found that the present invention is reduced, and completed the present invention.

That is, the present invention relates to an organic wastewater treatment apparatus using an activated sludge treatment apparatus having a reaction tank for treating organic wastewater with microorganisms, and a filtration membrane for separating the suspension after the reaction treatment into treated water and a concentrated liquid. In the treatment method, at least one compound of wood vinegar solution, polyphenols, organic acid, and metal salt of organic acid is added, and the concentration of the added compound in the reaction tank becomes 1 ppb to 100 ppm. The first feature is that the concentration of the compound added is kept at 10 ppb to lp pm. Further, a polyphenol and an organic acid metal salt are added, and the concentrations of the added polyphenol and the organic acid metal salt in the reaction vessel are maintained at 10 ppb to lp pm, respectively. This is the third feature, and the fourth feature is that the filtration membrane is a microfiltration membrane or an ultrafiltration membrane. Brief Description of Drawings

FIG. 1 is a diagram showing a configuration and a processing flow of an experimental apparatus used in the present example and a comparative example. FIG. 2 is a graph showing a relationship between a processing time and a pressure change in Example 1. 3 is a graph showing the relationship between the processing time and the pressure change in Example 2, and FIG. 4 is a diagram showing a general processing flow of organic wastewater using a conventional filtration membrane. In the figure, A is a reaction tank, 1 is a raw water tank, 2 is an organic wastewater, 3 is a denitrification tank, 4 is a nitrification tank, 5 is a filtration membrane, 6 is filtered water, 7 is a sewage transfer pump, and 8 is a sludge circulation pump. , 9 is a filtered water transfer pump, 10 is a pressure gauge, 11 is a stirrer, 1 2 is a diffuser, 13 is a blower, 14 is a filtered water circulation pump, 15 is a filtered water tank, and 16 is organic wastewater. , 17 is a pretreatment step, 18 is a reaction tank, 19 is a disinfection tank, 20 is a filtration membrane, 21 is a sludge concentration tank, 22 is a sludge storage tank, 23 is filtered water, 24 is sludge, 25 is excess sludge. BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, wood vinegar, phenols, polyphenols, organic phenols, polyphenols, organic acids, and organic acid metal salts are added in a reaction vessel by adding at least one compound of the compounds. It is necessary to maintain at least one compound of an acid and a metal salt of an organic acid at a concentration of 1 ppb to 100 p; m, more preferably 10 ppb to lppm. From the viewpoint of the effect of activating sludge and reducing excess sludge, the concentration of the compound in the reaction tank must be higher than 1 ppb, and it does not deteriorate the quality of the treated water as a bactericide and inhibitor for activated sludge. From the point of view, it must be lower than l OO p pm. The reaction tank in the present invention refers to a tank for treating organic wastewater with microorganisms. In the examples described later, a two-tank type is shown, but the reaction tank may be a single tank. It may be a double tank of more than a tank.

The wood vinegar liquid in the present invention is preferably derived from hardwood, and the polyphenols are not particularly limited, but tannin, rutin, and quercetin are preferable, and the organic acid and the organic acid metal salt are not particularly limited. Preferred are formic acid, acetic acid, propionic acid, butyric acid and metal salts thereof such as sodium salts and potassium salts. The above compounds have the effect of suppressing the amount of activated sludge polymer and the amount of generated sludge even when they are used alone, but they contain both polyphenols and metal salts of organic acids, and the concentration in the reaction tank solution is reduced. It is more effective to keep each of them at 10 ppb to lppm, and more preferably, the mass ratio of polyphenols to organic acid metal salt (polyphenols organic acid metal salt) is 70 to 3 ppm. It is preferable to mix in the range of 0 to 30/70.

'' The blocking of the filtration membrane is caused by the adhesion of the activated sludge polymer that does not pass through the filtration membrane to the filtration membrane surface, and the effect of the present invention is that the amount of the polymer is reduced by the compound held in the reaction tank. By Microfiltration membranes (pore size 0.1 l / m to 10 m) and ultrafiltration membranes (pore size 0.001 βη! ~ 0.01 / zm) are used to extend the life of filtration membranes. It is more effective when When considering wastewater treatment with a large amount of contaminants, the pore size of the filtration membrane is preferably larger than that of the ultrafiltration membrane. In order to prevent the activated sludge cells from permeating the filtration membrane and deteriorating the treated water, the pore diameter of the filtration membrane is preferably smaller than that of the microfiltration membrane.

The method for maintaining the concentration of the compound in the reaction tank is not particularly limited, but the sludge multiplies in the reaction tank, and the compound acts more effectively in this step. It is preferable to maintain the concentration in the reaction tank by adding it to at least one of the reaction tanks. Since the flow control tank has a function to temporarily stay in order to transfer the inflow wastewater to the reaction tank at a constant rate, it is possible to read the amount of inflow wastewater from the flow meter and add the compound quantitatively based on the flow rate. it can.

Although the detailed mechanism of action of the present invention is not clear, the compound enhances the respiratory activity of bacteria in the sludge, thereby reducing the amount of polymer produced by the bacterium, and the produced polymer is active. Consumed by transformed bacteria. As a result, the amount of viscous polymer that causes blockage of the membrane is reduced, membrane clogging is delayed, and activated microorganisms are promoted by auto-oxidation, reducing excess sludge generated. it is conceivable that.

Hereinafter, examples of the present invention will be described, but the present invention is not limited to these examples.

First, before conducting a continuous experiment using a filtration membrane, to evaluate the effects of various compounds, as a reference example, sludge was cultured with or without the compound, and after the culture. Comparison of sludge increase and comparison of dewaterability based on sludge resistivity in dewaterability test went.

By the way, organic wastewater is oxidized by microorganisms in activated sludge in a reaction tank during the treatment process. In other words, the organic wastewater is fed into the reactor as a nutrient for activated sludge and treated. Therefore, in the following Reference Example, an organic wastewater was treated by treating an Erlenmeyer flask as a reaction tank.

In the following description, L represents a little.

Treatment of the organic waste water is 5 0 Erlenmeyer flask OML, the activated sludge collected from a sewage treatment plant (5 5 0 0 mgZL) 2 0 was OML charged, meat extract, polypeptone, urea, N a ₂ HP_〇 ₄ , N a C l, KC 1 , C a C l There mg S 0 ₄ organic wastewater consisting of a (C 0 D 2 8 7 0 mg / L) 2 5mL was added, urchin by the wood vinegar is l OO ppb Then, add 2.5 mL of wood vinegar solution (10 mg / L), add tap water so that the total volume becomes 250 mL, and rotate for 8 hours under the condition of 20 ° (: 130 rpm). This was performed by cultivation.

After the culture, the obtained suspension (activated sludge) was centrifuged (1300 rpm, 10 minutes), and the COD of the supernatant was measured. After drying (105 ° C, 24 hours), the weight was measured and the sludge increase rate was calculated.

Separately from this, after culturing, the obtained suspension (activated sludge) is concentrated and used in accordance with the Nutsche test described in Chapter 4, Section 14 of the Sewerage Test Method issued by the Japan Sewerage Association. The sludge specific resistance was calculated.

The results are shown in Table 1.

Instead of the wood vinegar solution in Reference Example 1, 2.5 mL of tannin (lOmgZL) was added so that the ninnin became 100 ppb, and the culture was performed in the same manner as in Reference Example 1. went. So Table 1 shows the results.

Instead of the wood vinegar solution in Reference Example 1, add 2.5 mL of acetic acid (lOmgZL) so that the acetic acid becomes 100 ppb, culture in the same manner as in Reference Example 1, and perform the same measurement and calculation. went. Table 1 shows the results.

Instead of the wood vinegar solution in Reference Example 1, 2.5 mL of sodium acetate (10 mg / L) was added so that sodium acetate would be 100 ppb, and cultivation was performed in the same manner as in Reference Example 1, and the same measurement was performed. And calculated. The results are shown in Table 1.

In place of the wood vinegar solution in Reference Example 1, 2.5 mL of tannin (5 mg / L) and 2.5 mL of acetic acid (5 mg / L) were added so that the amount of ninnin and acetic acid became 50 ppb, respectively. , And the same measurement and calculation were performed. The results are shown in Table 1.

Instead of the wood vinegar solution in Reference Example 1, 2.5 mL of tannin (5 mg / L) and 2.5 mL of sodium acetate (5 mgZL) were added so that the tannin and sodium acetate became 50 ppb, respectively. Culture was performed, and the same measurement and calculation were performed. Table 1 shows the results.

The same culture was performed as in Reference Example 1 except that the wood vinegar solution was not added, and the same measurement and calculation were performed. However, the amount of sludge increase in Reference Comparative Example 1 was defined as a sludge increase rate of 100%. The results are shown in Table 1.

The sludge increase rate calculated in the above Reference Examples 1 to 6 is the sludge increase rate of Reference Comparative Example 1 as 100%, and the sludge increase rate of each Reference Example. The amount is divided by the amount of sludge increase in Reference Comparative Example 1 and is shown in%. From Table 1, looking at the specific resistance of the sludge is indicative of the dehydrating, or, if none added 3.4 9 1 0 ^{1 ()} seconds against although it was ² 7 Dea', pyroligneous acid, polyphenols , Organic acids and organic acid metal salts were added, the specific resistance of the sludge was small, as 2.28 X 101 ⁽⁾ to 3.18 X 101 ^Qs ² Zg It can be seen that the dehydration property was improved. Table 1 also shows that when wood vinegar, polyphenols, organic acids, and organic acid metal salts are added, the rate of increase in sludge is suppressed to about 66 to 85%, and the amount of excess sludge generated is reduced. It turns out that there are few. In addition, the water quality at this time was equal to or higher than Comparative Reference Example 1 in which none of them was added.

From the above, it was found that wood vinegar, polyphenols, organic acids, organic acid metal salts, and combinations thereof suppressed the amount of generated sludge, and further improved the dewaterability of the cultivated sludge. . Based on this, a continuous experiment using a filtration membrane was performed.

table 1

A continuous experiment by the activated sludge method with a microfiltration membrane was performed.

Fig. 1 shows the configuration of the experimental apparatus.

As shown in Fig. 1, reaction tank A is composed of a denitrification tank 3 (7.5 L) and a nitrification tank 4 (7.5 L). A filtration membrane 5 of 90 mm × 200 mm) was immersed. The denitrification tank 3 is provided with a stirrer 11 for stirring activated sludge, and the nitrification tank 4 is provided with an air diffuser 12 at the bottom of the tank for the purpose of supplying oxygen to the activated sludge and stirring the sludge. It was installed and connected to a blower 13 to allow ventilation. Further, a pressure gauge 10 was installed between the filtration membrane 5 and the filtration water transfer pump 9 to measure the suction pressure of the membrane.

In the treatment with the above experimental equipment, the denitrification tank 3 and the nitrification tank 4 were previously filled with activated sludge collected from the treatment plant to a concentration of about 10 g ZL, and then the organic wastewater collected from the treatment plant on a daily basis. The raw water tank 1 The wastewater was sent to the denitrification tank 3 using the sewage transfer pump 7 at a flow rate of 1-25 L / r (30 L / day). The organic wastewater 2 sent to the denitrification tank 3 is mixed with the activated sludge in the denitrification tank 3 and then transferred to the nitrification tank 4 in an extrusion flow manner. On the other hand, from the nitrification tank 4 to the denitrification tank 3, activated sludge of about 300% of the inflow water is circulated by the sludge circulation pump 8, and the filtration is performed through the filtration membrane 5 immersed in the nitrification tank 4. Water 6 is drained by a filtered water transfer pump 9.

Incidentally, the film flux 1. To a 5 m ³ Zm ² · day, and transfer the filtered water 6 to filtering water tank 1 5 in an intermittent operation so that the flow rate of 5 L / hr, further filtering the filtered water 6 The water was returned to the nitrification tank 4 by the water circulation pump 14 at a flow rate of 3.75 L / hr. The air volume in the nitrification tank 4 was about 5 LZmin, and continuous air ventilation was performed.

Under the above conditions, once a day, 150 mL of a mixed solution of tannin and sodium acetate prepared at 20 ppm each was directly added to the denitrification tank 3. The measurement was performed on the suction pressure of the membrane and the filtered water COD.

The membrane flux 1. To a ^{^{2 m 3 / m 2 · day}} , 3. 7 5 transports the filtered water 6 in continuous operation so that the flow rate of the LZH r to filtering water tank 1 5, further filtered water 6 The same treatment as in Example 1 was performed except that the filtrate was returned to the nitrification tank 4 at a flow rate of 2 LZ hr by the filtered water circulation pump 14, and the same measurement was performed.

To the membrane flux and ^{^{0. 5 m 3 / m 2 ·}} day, except for transferring the filtered water 6 to filtering water tank 1 5 in continuous operation so that the flow rate of 1. 2 5 L / hr, Example The same processing was performed as in 1. The measurement was performed on the reactor sludge concentration, reactor sludge volume, and filtered water COD.

Performed except that tannin and sodium acetate were not added The same processing as in Example 1 was performed, and the same measurement was performed.

The same treatment as in Comparative Example 1 was performed except that the film flux was changed to 1.2 m ³ / m ² · day, and the same measurement was performed.

The same processing as in Comparative Example 1 was performed, except that the membrane flux was set to 0.5 m ³ / m ² · day, and the same measurement as in Example 3 was performed.

The results of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Tables 2, 3, and 4.

Table 2 and Fig. 2 show the results of the pressure change at each elapsed time in Example 1 and Comparative Example 1, and Table 3 shows the results of the pressure change at each elapsed time in Example 2 and Comparative Example 2. This is shown in FIG. Table 2 shows the results of measuring the filtered water COD of each of the elapsed times of Example 1 and Comparative Example 1, and the filtered water COD of each of the elapsed times of Example 2 and Comparative Example 2 was measured. The measured results are shown in Table 3.

According to Tables 2 and 3, and Figures 2 and 3, when tannin and sodium acetate were added to give 200 ppb, the pressure rise was suppressed as compared to the case where tannin and sodium acetate were not added. Regarding the period when the maximum suction pressure of the filtration membrane was reached—50 kPa, tannin and sodium acetate were added at 200 ppb, compared to 36 days without any addition. When it was added so as to be 60 days, the life of the film was increased by about 1.7 times. The COD of the filtered water at that time was comparable. Furthermore, as for the sludge increase, as shown in Table 4, when nothing was added, the amount of ninnin and sodium acetate was 20 O ppb, while the amount of 392 mg ZL increased in 10 days. In this case, only 88 mg / L increased in 10 days, indicating that the amount of generated sludge was suppressed to 22%. Also, the filtration at that time Water COD was comparable.

Table 2

(Note: one is not measured)

Table 3

(Note: one is not measured)

Table 4

(Note: one is not measured) Industrial applicability

As described above, according to the method for treating organic wastewater of the present invention, the respiratory activity of patella in activated sludge is activated, and the amount of activated sludge polymer is reduced. As a result, the service life of the membrane is prolonged and the amount of permeated water is increased. Therefore, the cost for membrane management is reduced. Also, since the amount of excess sludge generated can be reduced, the disposal cost of excess sludge is also reduced.

Claims

The scope of the claims

1. An organic wastewater treatment method using an activated sludge treatment apparatus having a reaction tank for treating organic wastewater with microorganisms and a filtration membrane for separating a suspension after the reaction treatment into treated water and a concentrated liquid, comprising: Liquid, a polyphenol, an organic acid, and a metal salt of an organic acid are added, and the concentration of the added compound in the reaction vessel is maintained at 1 ppb to 100 ppm. Characteristic organic wastewater treatment method.

2. The method for treating organic wastewater according to claim 1, wherein the concentration of the added compound is maintained at 10 ppb to 1 pm.

3. A polyphenol and an organic acid metal salt are added, and the concentrations of the added polyphenol and the organic acid metal salt are each maintained at 10 ppb to 1 ppm. 3. The method for treating organic wastewater according to paragraph 1 or 2.

4. The method for treating organic wastewater according to any one of claims 1 to 3, wherein the filtration membrane is a microfiltration membrane or an ultrafiltration membrane.