KR100666605B1 - Wastewater treatment method for reducing waste-sludge utilizing an anaerobic digestion reactor and wastewater treatment system thereof - Google Patents

Abstract

The present invention relates to a wastewater treatment method and apparatus for reducing wastewater sludge generated in a wastewater treatment process using an anaerobic digester, and the wastewater treatment method uses anaerobic microorganisms for organic matter in wastewater generated in a wastewater treatment plant. By inducing anaerobic reaction to convert to organic acid, and using aerobic microorganisms in an aeration tank.

Waste Sludge Reduction, Anaerobic Digester, Wastewater Treatment Method

Description

Wastewater treatment method and apparatus for reducing waste sludge by using anaerobic digester {a wastewater treatment method for reducing waste-sludge utilizing an anaerobic digestion reactor and wastewater treatment system

Figure 1 shows a process for treating waste sludge using the wastewater treatment apparatus according to the first embodiment of the present invention.

Figure 2 shows the treatment principle of the concentrated anaerobic sludge to anaerobic waste sludge in the present invention.

Figure 3 is a simplified view showing a conventional process for treating waste sludge, and a process for treating waste sludge using an anaerobic digestion tank according to Example 1 of the present invention.

4 is an experimental result of observing the trend of changes in suspended microorganism (MLSS) concentration before and after treating waste sludge through the wastewater treatment apparatus of Example 1 of the present invention.

5A shows the ratio of F / M (original wastewater / microorganism) after treating waste sludge through the wastewater treatment apparatus of Example 1 of the present invention.

Figure 5b shows the pH change after treating the waste sludge through the wastewater treatment apparatus of Example 1 of the present invention.

The present invention circulates and reprocesses the organic acid reactants produced through the anaerobic reaction of waste sludge to an aerobic tank, which is an aerobic reactor, to compensate for the disadvantages of the anaerobic process, which is relatively difficult to operate, and the process proceeds relatively quickly so that The present invention relates to a wastewater treatment method and apparatus capable of substantially reducing the amount of waste sludge by reprocessing an organic acid.

In general, wastewater treatment processes use UASB (Upflow Anaerobic Sludge Blanket Process) and UMBR (Upflow Multi-layer Bio Reactor) processes that have been reported to the industry.

However, all of the above methods generate a large amount of waste sludge after the wastewater treatment process, and the waste sludge thus generated is reprocessed through a dehydration process using a press filter, a vacuum dehydrator, and finally discarded. It is becoming.

The waste sludge itself contains a high concentration of organic wastewater as it is the main cause of secondary environmental pollution, and additional costs are required because a separate treatment device for treating this is required.

In order to solve the problems of the prior art, it is an object of the present invention to provide a wastewater treatment method and apparatus for minimizing the amount of waste sludge generated in the wastewater treatment process, and to facilitate the treatment of high concentration organic wastewater.

Another object of the present invention is to provide a wastewater treatment method and apparatus capable of treating the organic wastewater with high efficiency, simple process, low installation cost, easy commercialization, and high efficiency compared to the conventional method.

In order to achieve the above object, the present invention

(a) supplying wastewater through a flow control tank,

(b) an aerobic treatment step of treating the wastewater using aerobic microorganisms under aeration conditions in which dissolved oxygen is present in the aeration tank;

(c) separating the sludge and the treated supernatant by precipitating the treated water in a settling tank; And

(d) dividing the separated sludge into return sludge and waste sludge and transferring the returned sludge to an aeration tank and transferring the precipitated sludge to a thickening tank for concentrating.

As a method of treating wastewater by the activated sludge method comprising:

Treatment of wastewater by the activated sludge method comprising the step of transferring the waste sludge obtained in step (d) to an anaerobic tank to anaerobic treatment with anaerobic microorganisms, and transferring the treated anaerobic sludge to the aeration tank of step (b). Provide a method.

In addition, the present invention is a flow control tank for controlling the waste water supply, aeration tank for performing aerobic reaction using aerobic microorganisms, primary and secondary sedimentation tank for precipitating the treated water introduced from the aeration tank, and the primary precipitation tank And a concentration tank for collecting the waste sludge introduced from the secondary settling tank,

A thickening tank having waste sludge collected from the primary and secondary sedimentation tanks and having a conveying pipe for transferring the waste sludges to an anaerobic digester;

Anaerobic digestion tank for decomposing untreated hardly decomposable material in the aeration tank using anaerobic microorganisms from the concentration tank and reducing waste sludge with a transfer pump and a transfer pipe for transferring the anaerobic sludge to the aeration tank.

It provides a wastewater treatment apparatus comprising a.

Hereinafter, the present invention will be described in detail.

The method of the present invention refers to the UASB (Upflow Anaerobic Sludge Blanket Process) and UMBR (Upflow Multi-layer Bio Reactor) processes to treat wastewater using the advantages of anaerobic processes. The present invention relates to a method for economically treating a thickener sludge after a process and before being disposed of.

The present invention is characterized by converting waste sludge into anaerobic digestion using an anaerobic digester to convert into organic acids, alcohols, or the like, into a form that is easily reprocessed in an aeration tank.

In general, the anaerobic treatment of wastewater includes a process in which high molecular weight organic matters are decomposed into lower organic acids, and finally converted into methane gas and carbon dioxide by decomposition of anaerobic microorganisms. On the other hand, in the present invention, the anaerobic reaction of the concentrated waste sludge does not convert to methane gas and carbon dioxide, and causes only decomposition to organic acids. To this end, the present invention adjusts the temperature, residence time, and flow rate of the anaerobic tank to a specific range to meet the conditions of the anaerobic tank.

In the present invention, the principle of treating the concentrated anaerobic sludge is as shown in Figure 2, through the anaerobic reaction of the concentrated sludge to produce a volatile fatty acid (Volatile fatty acid (VFA) to convert into aerobic sludge, which is transferred to the aeration tank By increasing the concentration of suspended microorganisms (Mixed Liquor Suspended Solid, MLSS) in the aeration tank. The aerobic reaction and anaerobic reaction is the same as in Scheme 1 and Scheme 2, the organic acid includes a cell, organic acid, alcohol, CO2, H2, NH3 and the like.

Scheme 1

Organics + O ₂ → Cellular Formation + CO ₂ + Energy

Organics + O ₂ → CO ₂ + H ₂ O + Energy

Cellular material + O ₂ → CO ₂ + H ₂ O + energy

Scheme 2

The present invention uses the anaerobic treatment process to treat a high concentration of condensate tank waste (anaerobic sludge) discharged from the wastewater treatment process, to reduce the amount, to reduce the dehydration cycle of the waste, the amount of chemicals and waste used during dehydration Sludge is to reduce the processing cost. In addition, the present invention is to provide a method for easily treating the high concentration organic wastewater flowing out in the future phenol process.

Hereinafter, the wastewater treatment method of the present invention will be described with reference to the drawings. Figure 1 shows a process for treating waste sludge using the wastewater treatment apparatus according to the first embodiment of the present invention.

Wastewater treatment method of the present invention, basically the wastewater treatment using the active sludge method is operated in the manner as shown in Figure 2, anaerobic decomposition of the waste sludge of the thickener (Thickener) by applying an anaerobic reactor without additional equipment And then it can be configured as a system that is transferred to the aeration tank and processed again, and this process is carried out continuously, reducing the final waste sludge amount.

Preferably, the method of the present invention comprises the steps of (a) supplying wastewater through a flow control tank, (b) aerobic treatment step of treating the wastewater with aerobic microorganisms under aeration and stirring conditions in the aeration tank, (c) Precipitating the treated water in a settling tank to separate the sludge and the treated supernatant; And (d) the sludge is divided into a return sludge and a waste sludge, and the return sludge is transferred to an aeration tank and the precipitated waste sludge is transferred to a concentration tank for concentrating, and the waste sludge obtained in step (d) is concentrated. Transfer to an anaerobic tank and anaerobic treatment with anaerobic microorganisms, and the anaerobic waste sludge is transferred to the aeration tank of step (b) for processing.

At this time, the settling tank in the step (c) is composed of a first settling tank and a second settling tank sequentially disposed, the first settling tank is classified into a supernatant, return sludge and waste sludge by centrifugation, the supernatant is a secondary settling tank The transferred and returned sludge is transferred to the aeration tank, and the waste sludge is transferred to the thickening tank. In the second precipitation tank, the supernatant and precipitated waste sludge are classified by chemical precipitation reaction, and the supernatant is discharged and the precipitated waste sludge is transferred to the thickening tank. desirable.

In addition, in step (c), the settling tank is composed of a first settling tank and a second settling tank sequentially disposed, and the first settling tank is classified into a supernatant and a waste sludge by centrifugation, and the supernatant is transferred to a secondary settling tank. Waste sludge is transferred to the thickening tank, and the second settling tank is classified into a supernatant and precipitated waste sludge by a chemical precipitation reaction, and the supernatant is discharged and the precipitated waste sludge may be transferred to the thickening tank.

The chemical precipitation reaction carried out in the second precipitation tank may be carried out by a conventional method, and is not particularly limited.

Figure 3 briefly shows a process diagram of the conventional waste sludge treatment process, anaerobic digester for treating waste sludge according to an embodiment of the present invention.

3, in the case of the conventional method, the waste sludge is directly transferred to the sludge mixing tank 20 through the transfer pipe 50 in the thickening tank 10, but the present invention provides an anaerobic tank 30 in the thickening tank 10. It can be seen that the waste sludge is transferred to), and the partial anaerobic reaction sludge obtained through the anaerobic reaction is transferred to the aeration tank 40 for processing.

At this time, the operating conditions of the anaerobic reactor of the present invention are as follows.

The initial condition of the anaerobic reactor is to concentrate the sludge of the thickening tank as much as possible to enter the anaerobic reactor. The sludge amount of the concentration tank is 16 to 50 m 3 / day.

Thereafter, the introduced concentrated sludge is filled in an anaerobic reaction tank (based on 95 m ³ ) for about 2/3, and then subjected to anaerobic reaction with a residence time at a constant temperature. The anaerobic reaction is a reaction in which the anaerobic reaction is already progressing in the concentration tank, so that the reaction time is allowed to leave a longer time in the anaerobic tank, so that it is made in a range of appropriate temperature and pH. Preferably, the anaerobic reaction is subjected to the anaerobic reaction with a residence time of about 7 to 10 days while maintaining a temperature of 35 ℃ to 40 ℃ (optimum 37.5 ℃). This is the anaerobic initial reaction time for organic acid production, after which the concentrated sludge anaerobic residence time can be shortened to a maximum of 24 hours. At this time, the anaerobic reaction may decrease the reaction rate during air contact, it is preferable to minimize the contact with the air. Then, agitation is preferably performed for smooth anaerobic reaction, and the concentration of the anaerobic reactor is at least 15,000 ppm based on MLSS, preferably 10,000 to 15,000 ppm. When the reaction proceeds to the above, the anaerobic sludge is transferred to the aeration tank at 1.0 m ³ / hr to 1.5 m ³ / hr for aerobic microbial reaction.

Thereafter, the aeration treatment as described above is performed, the treated water is discharged through the first settling tank and the second settling tank, and the waste sludge is repeatedly transferred to the anaerobic tank, thereby repeatedly reducing the amount of waste sludge.

At this time, the operation conditions (temperature, pH, dissolved oxygen (DO)) of the aeration tank may be set according to the site treatment situation.

The concentrated sludge may be obtained by chromium and manganese. In the present invention, the concentrated sludge is preferably COD _Mn by manganese.

In addition, when the concentrated sludge is supplied to the aeration tank, the MLSS initially increases slightly, and the precipitation rate of the precipitation tank may decrease due to the generation of pin-floc, and there is no change in pH, but the chemical oxygen demand (COD) This can rise. In order to prevent this and to operate safely, the dissolved oxygen in the aeration tank due to the change of organic matter (nutrient) / microorganism (F / M ratio) in the wastewater due to the increase of MLSS is called DO. It is desirable to maintain the amount. More preferably, the dissolved oxygen amount in the aeration tank is preferably maintained at 5.5­6.5 ppm. In addition, the rise of MLSS may cause overload of the settling tank, and in this case, it is desirable to minimize the load state by appropriately adjusting the amount of the return sludge and the surplus sludge.

Through the treatment of waste sludge as described above, it can be expected that MLSS is increased by 1,000 to 1,500 ppm when the anaerobic process is injected into the aeration tank. However, volatile organic acids (VFA) decomposed in the anaerobic process are increased by increasing the inflow COD. A stable F / M ratio of about 0.1 to 0.2 can be formed. In addition, the sludge is transferred to the thickening tank, and the concentration and the amount of minerals are relatively increased through the anaerobic reaction of the aeration tank and recycled back to the thickening tank, so the waste sludge press filter process is shortened and dehydrated. The amount of chemicals used in the process can also be significantly reduced.

Therefore, the final waste sludge amount by the wastewater treatment method of the present invention is reduced by 50% or more than the conventional waste sludge amount to minimize the waste sludge amount. In addition, the method of the present invention can treat various organic wastewater with high efficiency regardless of the kind of wastewater.

Meanwhile, the wastewater treatment apparatus of the present invention basically includes a flow control tank, an aeration tank, a primary precipitation tank, a secondary precipitation tank, and a concentration tank, and includes an anaerobic tank to reduce the amount of waste sludge.

In the wastewater treatment apparatus of the present invention, the anaerobic tank serves to decompose untreated hardly decomposable material in the aeration tank by treating waste sludge introduced from the concentration tank using anaerobic microorganisms. At this time, the anaerobic tank is provided with a transfer pump and a transfer pipe for transferring the anaerobic sludge to the aeration tank, it is preferred that the nitrogen supply means and agitator.

At this time, the flow rate adjustment tank is preferably provided with a means for reducing the load fluctuations by adjusting the flow rate of the wastewater flows in. The aeration tank is preferably provided with a stirrer for treating the wastewater introduced from the flow control tank under activated sludge conditions. The primary sedimentation tank is provided with an apparatus for precipitating activated sludge by centrifugation by a scraper of the treated water introduced into the aeration tank, and an aeration tank conveying sludge pipe and a concentration tank surplus sludge pipe. The secondary sedimentation tank is provided with a chemical injection device for precipitating the supernatant introduced from the primary sedimentation tank by chemical precipitation reaction, and has a transfer pipe for transferring the waste sludge precipitated by the chemical precipitation reaction to the concentration tank.

In addition, the concentration tank is preferably provided with a transfer pipe for collecting the waste sludge introduced from the primary settling tank and the secondary settling tank, and transfer the waste sludge to the anaerobic digestion tank.

The transfer pipe between the anaerobic tank and the aeration tank is provided with a transfer pump for quantitatively transferring the treated water of the anaerobic tank to the aeration tank, and a transfer pipe for allowing the treated water not transferred to the aeration tank to be returned to the anaerobic tank.

As described above, the present invention anaerobic treatment of the waste sludge generated in the wastewater treatment plant using anaerobic microorganisms of the anaerobic tank, and a predetermined amount is injected into the aeration tank to process organic matter and organic acid in the sludge more efficiently by the activated sludge method. By repeatedly carrying out, the amount of waste sludge finally generated can be reduced. Therefore, the present invention can reduce the number of operations of the wastewater sludge dewatering process to improve the odor generation and worker environment, it is possible to reduce the waste sludge treatment cost.

Hereinafter, it demonstrates further in detail based on the Example of this invention. However, the following examples are for illustrating the present invention and the present invention is not limited to the following examples.

(Example 1)

Under the following conditions, the thickener sludge was anaerobic and retreated in an aeration tank.

-Experimental equipment operating conditions: temperature 30 ℃ / pH 6 ~ 7 / dissolved oxygen (DO) 4-5ppm

-Concentrated sludge generation: 16-50 ㎥ / day (about 1.6% ~ 5% of current influent), and about 10% of the influent was injected into the tank sludge in the experiment.

At this time, the operating conditions (temperature, pH, DO) of the aeration tank is adjusted to the same conditions as the actual site treatment conditions, and observed the concentration and equilibrium state of suspended microorganisms (MLSS) expected when the anaerobic wastewater is added to the result, and the results are shown in FIG. Indicated. In the anaerobic tank, the anaerobic reaction was carried out at 35 ° C., and anaerobic sludge generated in the settling tank (ie, the sludge transferred to the thickening tank).

In addition, the F / M ratio and pH change after the waste sludge treatment are shown in FIGS. 5A and 5B.

In this case, the aeration tank is divided into two compartments, one of which is referred to as (a), the other is referred to as (b), and (a) and (b) in Figs. Passes to a-> b to ensure wastewater treatment time.

(Example 2-6 and Comparative Example 1)

Waste sludge generated in the concentration tank was treated using the process diagram of FIG. 1 and the anaerobic reactor of FIG. 3. Operation conditions of the aeration tank and anaerobic tank are shown in Table 1 below, the sludge generated in the primary and secondary sedimentation tank, that is, partially anaerobic sludge transferred to the thickening tank, it was transferred to the aeration tank. We observed the rise and equilibrium of MLSS expected when the waste sludge was added to the aeration tank.

TABLE 1

Anaerobic and Aeration Tank Operation Conditions for Waste Sludge Treatment

Anaerobic tank Aeration tank Example 2 Example 3 Example 4 Example 5 Example 6 pH 7.8 7.5 7.9 7.7 7.5 7-8 DO (ppm) - - - - - 5 ~ 6 MLSS (ppm) 13,460 18,600 19,140 18,900 21,720 2,000-3,000 Temperature (℃) 35 35 35 35 35 25-35 Wastewater Retention Time (HRT) (day) 4.75 4.75 4.75 4.75 4.75 1.00 Waste Sludge Inflow (m ³ / day) 20 20 20 20 20 20-30 Reactor capacity (m ³ ) 95 95 95 95 95 2,800 Waste sludge reduction efficiency (%) 50 60 60 70 70 -

Through the results of Table 1, in the case of the present invention by applying the anaerobic process, it can be seen that the waste sludge amount is reduced by more than 50% to minimize the waste sludge amount. In other words, the anaerobic wastewater concentrated sludge was treated almost efficiently except when excessively introduced during the aerobic reaction, and the optimum aeration tank treatment effect was derived at the concentrated sludge less than 3 m3 / hr. In addition, microscopic examination of the state of the microorganisms showed that the best affinity with the existing aerobic treatment, and COD reduction efficiency and phenol removal efficiency was almost no difference.

On the other hand, the organic matter was decomposed into volatile fatty acids (VFA; Volatile Fatty Acid) such as acetic acid, ethanol and propionate butyrate through anaerobic reaction, and the phenomenon of temporarily increasing COD was measured. As it is decomposed, it can be judged as an effect of reducing the COD load of the aeration tank.

The method of the present invention is a method of anaerobic waste sludge by aerobic treatment of the anaerobic reaction intermediate product, the process is simple, low installation cost, easy to commercialize and at the same time minimize the amount of waste sludge generated.

Claims (8)

delete (a) supplying wastewater through a flow control tank, (b) an aerobic treatment step of treating the wastewater using aerobic microorganisms under aeration conditions in which dissolved oxygen is present in the aeration tank; (c) separating the sludge and the treated supernatant by precipitating the treated water in a settling tank; And (d) dividing the separated sludge into return sludge and waste sludge, the return sludge is transferred to an aeration tank, and the precipitated waste sludge is transferred to a thickening tank and concentrated. As a method of treating wastewater by the activated sludge method comprising: And transporting the waste sludge obtained in step (d) to an anaerobic tank for anaerobic treatment with anaerobic microorganisms, and transferring the treated anaerobic sludge to the aeration tank for treatment (b). In step (c), the settling tank is composed of a first settling tank and a second settling tank sequentially disposed, and the first settling tank is classified into a supernatant, a returning sludge and a waste sludge by centrifugation, and the supernatant is transferred to a secondary settling tank. The returning sludge is transferred to the aeration tank and the waste sludge is transferred to the thickening tank, and in the second precipitation tank, the supernatant and precipitated waste sludge are classified into the chemical precipitation reaction, and the supernatant is discharged and the precipitated waste sludge is transferred to the thickening tank. Wastewater treatment method by activated sludge method. (a) supplying wastewater through a flow control tank, (b) an aerobic treatment step of treating the wastewater using aerobic microorganisms under aeration conditions in which dissolved oxygen is present in the aeration tank; (c) separating the sludge and the treated supernatant by precipitating the treated water in a settling tank; And (d) dividing the separated sludge into return sludge and waste sludge, the return sludge is transferred to an aeration tank, and the precipitated waste sludge is transferred to a thickening tank and concentrated. As a method of treating wastewater by the activated sludge method comprising: And transporting the waste sludge obtained in step (d) to an anaerobic tank for anaerobic treatment with anaerobic microorganisms, and transferring the treated anaerobic sludge to the aeration tank for treatment (b). In step (c), the settling tank is composed of a first settling tank and a second settling tank sequentially disposed, and the first settling tank is classified into a supernatant and a waste sludge by centrifugation, and the supernatant is transferred to a secondary settling tank and the waste sludge is Is transported to the concentration tank, the second precipitation tank is classified into the supernatant and precipitated waste sludge by the chemical precipitation reaction, the supernatant is discharged and the precipitated waste sludge is transferred to the concentration tank, the method of treating wastewater by the activated sludge method. . The method of claim 2 or 3, The anaerobic reaction is a wastewater treatment method made at a temperature of 35 ℃ to 40 ℃, and a retention time of 7 to 10 days. The method of claim 2 or 3, The anaerobic reaction is a wastewater treatment method made under the conditions of the waste sludge flow rate 20 ~ 30 m ³ / day. Flow control tank for controlling wastewater supply, aeration tank for conducting aerobic reaction using aerobic microorganisms, primary and secondary precipitation tanks for sedimenting the treated water introduced from the aeration tank, and from the primary and secondary precipitation tanks Including a concentration tank for collecting the introduced waste sludge, It includes an anaerobic tank for anaerobic treatment of waste sludge introduced from the concentration tank using anaerobic microorganisms, The flow control tank is provided with a means for reducing the load fluctuations by introducing the wastewater, adjusting the flow rate of the incoming wastewater, The aeration tank is provided with a stirrer for treating the wastewater introduced from the flow control tank under active sludge conditions, The primary sedimentation tank is provided with a device for precipitating activated sludge by centrifugation by a scraper of the treated water introduced from the aeration tank, and an aeration tank conveying sludge pipe and a concentration tank surplus sludge pipe. The secondary sedimentation tank is provided with a chemical injection device for precipitating the supernatant introduced from the primary sedimentation tank by chemical precipitation reaction, An apparatus for treating wastewater for reducing waste sludge, comprising a transfer pipe for transferring the waste sludge precipitated by the chemical precipitation reaction to a concentration tank. The wastewater treatment apparatus according to claim 6, wherein the anaerobic tank is provided with a nitrogen supply means and an agitator. delete

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