JP3348455B2 - Aerobic treatment of nitrogen and / or phosphorus deficient organic effluent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to nitrogen and / or aerobic treatment of nitrogen and / or phosphorus deficient organic effluents.
Alternatively, the present invention relates to an aerobic treatment method for phosphorus-deficient organic effluent.

[0002]

2. Description of the Related Art Conventionally, organic effluents deficient in nitrogen and / or phosphorus have been treated by an aerobic treatment method such as an activated sludge method. In this case, nitrogen and phosphorus necessary for growth of aerobic microorganisms are covered. It is added to the processing solution. In general, the aerobic treatment method for wastewater is a method of treating microorganisms using microorganisms, and therefore, it is necessary to treat the wastewater under conditions where aerobic microorganisms grow and act sufficiently. For example, in terms of nutrition, nitrogen is about 1/20 times the BOD in the effluent, about 1/15 times the carbon, phosphorus is about 1/100 times the BOD in the effluent, and about 1/50 times the carbon in the effluent. It is said that it is necessary.

[0003] Therefore, when treating an organic effluent deficient in nitrogen and / or phosphorus, a compound such as an ammonium salt or a phosphate is conventionally used as a nitrogen and / or phosphorus source in the effluent so that the above value is obtained. Has been added. However, in such a conventional method, the cost of the nitrogen or phosphorus source is high, and it is difficult to add necessary and sufficient nitrogen and phosphorus. If added excessively, nitrogen and phosphorus leak into the treated water, and the water quality deteriorates. May cause.

On the other hand, Japanese Patent Publication No. 57-19719 discloses that superfluous sludge is destroyed by ultrasonic waves, ground by a homogenizer,
Disclosed is a method of treating excess sludge, which destroys microbial cells by performing grinding by a mixer, destruction by high pressure and instantaneous decompression expansion, or oxidative decomposition by ozone gas, and aerobically digesting the obtained liquid.

[0005] However, this method is a method for reducing the volume of excess sludge, and uses a liquid in which microbial cells have been destroyed as a nitrogen and / or phosphorus source, and uses such a liquid as a nitrogen and / or phosphorus deficiency. It does not disclose that the wastewater is subjected to aerobic treatment by being added to the liquid to be treated.

Japanese Patent Publication No. 49-11813 discloses that excess sludge generated by aerobic treatment of an organic effluent is hydrolyzed by adding an alkali to the sludge and heating the resulting sludge. There has been proposed a method of treating excess sludge which is returned to the apparatus.

However, this method is also a method for reducing the volume of excess sludge, and uses an alkaline decomposition solution as a nitrogen and / or phosphorus source, and uses such a solution as a liquid to be treated deficient in nitrogen and / or phosphorus. And aerobic treatment of the effluent by addition to water.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the amount of nitrogen and / or phosphorus added when treating organic effluents deficient in nitrogen and / or phosphorus. It is to propose an aerobic treatment method for nitrogen and / or phosphorus deficient organic effluent which can be treated without adding a phosphorus source.

[0009]

Means for Solving the Problems The present invention, in the presence of activated sludge containing aerobic microorganisms, the nitrogen and / or phosphorus deficiency organic drainage in a method of treating aerobic activated sludge from the aerobic treatment system , And after solubilizing the extracted sludge, introducing the sludge into the aerobic treatment system as a nitrogen and / or phosphorus source, and treating the total amount of sludge in the aerobic treatment system.
The percentage of the extracted sludge should be reduced by nitrogen and / or phosphorus deficiency.
C / N ratio and / or C / P ratio of mechanical effluent and set sludge
Nitrogen and / or is adjusted according to the load
Alternatively, it is an aerobic treatment method of phosphorus-deficient organic effluent.

The effluent to be treated in the present invention is an organic effluent deficient in nitrogen or phosphorus, or both, and generally has a nitrogen content of 1 / BOD in the effluent.
20 times or less or 1/15 times or less of carbon, phosphorus content is 1/100 times or less of BOD in wastewater or 1/5 of carbon
It is an organic drainage of 0 times or less.

[0011] The present invention is an aerobic treatment method in which sludge is solubilized and the solubilized sludge is used as a nitrogen and / or phosphorus source. As the aerobic treatment, a known method can be adopted.For example, in an aerobic treatment system having an aeration tank and a sludge separation unit, an organic wastewater is introduced into the aeration tank, and is mixed with returned sludge and activated sludge in the aeration tank. Standard sludge method, in which the mixed liquid in the aeration tank is guided to a sludge separation section to perform solid-liquid separation and a part of the separated sludge is returned to the aeration tank, and various modifications thereof can be adopted.

The sludge to be solubilized may be withdrawn from the aeration tank or withdrawn from the sludge separation section. The latter case is equivalent to solubilizing excess sludge. The solubilized sludge is preferably introduced into the aeration tank, but is not limited to this.

Examples of the method for solubilizing sludge include oxidative decomposition with an oxidizing agent such as ozone and hydrogen peroxide, grinding, acid dissolution, alkali dissolution, heat decomposition, and acid / alkali heat decomposition. Of these, oxidative decomposition with ozone (hereinafter referred to as ozone treatment) is preferable.

Ozone treatment is a method of solubilizing sludge by contacting it with ozone. For example, solubilization can be achieved by contacting sludge with air containing ozone. Oxidative decomposition by hydrogen peroxide is a method of solubilizing sludge by contacting the sludge with hydrogen peroxide. For example, solubilization can be achieved by leaving sludge in the presence of hydrogen peroxide.

Grinding is a method of solubilizing sludge by breaking it with a ball mill or the like. Acid dissolution is a method of solubilizing sludge by contacting the sludge with an acid. As the acid, for example, hydrochloric acid, sulfuric acid and the like can be used. The alkali dissolution is a method of solubilizing sludge by contacting the sludge with an alkali. As the alkali, for example, sodium hydroxide, potassium hydroxide, or the like can be used. Thermal decomposition is a method of heating and solubilizing sludge. These methods can be combined, for example, the acid / alkali heat decomposition is a method of solubilizing by combining acid dissolution, alkali dissolution and heat decomposition.

Next, the ozone treatment will be described in detail.
FIG. 1 is a graph showing the relationship between the ozone injection rate for sludge and the residual rate of organic matter (% by weight), and FIG. 2 shows the relationship between the amount of Kjeldahl nitrogen and the amount of ammonia nitrogen when the ozone-treated sludge is aerobicly treated. It is a graph.

As shown in FIG. 1, since the sludge itself is not mineralized by the ozone treatment, the SS of the ozone-treated sludge is determined from the elemental composition ratio of the sludge (C ₁₁₈ H ₁₇₀ N ₁₇ O ₅ P).
/ N ratio is about 8, C / N ratio is about 6, SS / P ratio is about 60,
The C / P ratio becomes about 44. Also, as shown in FIG. 2, when the ozone-treated sludge is subjected to aerobic treatment, the amounts of the remaining Kjeldahl nitrogen and ammonia nitrogen are substantially equal, and most of the Kjeldahl nitrogen is ammonia nitrogen. You can see that. Therefore, it can be seen that the ozone-treated sludge is a good nitrogen source containing almost no hardly decomposable organic nitrogen.

Therefore, the ozone-treated sludge contains about 13% by weight of nitrogen per sludge, about 17% by weight of carbon, and about 1.6% by weight of phosphorus per sludge and about 2.2% by weight of carbon. You can see that. Since the ozone-treated sludge contains a certain amount of nitrogen and phosphorus, the ozone-treated sludge can be used as a nitrogen and / or phosphorus source.

Next, a description will be given of the ratio (the ozone treatment ratio) θ of the amount of the extracted sludge to the total amount of the sludge in the aerobic treatment system when the activated sludge is extracted from the aerobic treatment system and subjected to ozone treatment. Ozone treatment ratio when using ozone-treated sludge as a nitrogen source: θn (day ^-1 ) Ozone treatment ratio when using ozone-treated sludge as a phosphorus source: θp (day ^-1 ) C / N ratio of liquid to be treated: Rn (G-C / g-N) C / P ratio of liquid to be treated: Rp (g-C / g-P) Ratio of nitrogen necessary for decomposition of organic matter: En (g-N / g-)
C) = 0.07 (g-N / g-C) Ratio of phosphorus necessary for decomposition of organic matter: Ep (g-P / g-)
C) = 0.02 (g-P / g-C) Nitrogen content of ozone-treated sludge: Cn (g-N / g-S)
S) = 0.13 (g-N / g-SS) Phosphorus content of ozone-treated sludge: Cp (g-P / g-S)
S) = 0.016 (g-P / g-SS) Sludge concentration in the aeration tank: X (g-SS / liter) Carbon conversion tank load: 1 day when put in LV (g-C / liter / day) The amount of nitrogen required for (En-1 / Rn)
It is represented by LV. Therefore, the amount of ozonized sludge required when used as a nitrogen source is (En-1 / Rn) LV = C
It is represented by nθnX. When this equation is modified, θn = (En−1 / Rn) LV / X / Cn [1], and the ozone treatment ratio θn is obtained. The amount of phosphorus required per day is represented by (Ep-1 / Rp) LV.
Therefore, the amount of ozone-treated sludge required when used as a phosphorus source is represented by (Ep-1 / Rp) LV = CpθpX. By transforming this equation, θp = (Ep−1 / Rp) LV / X / Cp [2], and the ozone treatment ratio θp is obtained.

Therefore, if the ozone treatment is performed at the ozone treatment ratios θn and θp of the formula [1] or [2], the amounts of nitrogen and phosphorus necessary for aerobic treatment of the organic matter are sufficient. Aerobic treatment is possible without adding nitrogen and / or phosphorus sources. On the other hand, when the ozone treatment is performed at a value smaller than the ozone treatment ratio of the formula [1] or [2], the amount of nitrogen or phosphorus required for aerobic treatment of the organic matter is insufficient. The addition of other nitrogen and / or phosphorus sources such as phosphoric acid or phosphate is required. In any case, it is necessary to add a sufficient nitrogen and / or phosphorus source to form sludge at the beginning of the treatment.

Therefore, when θn = θp, θn or θ
p can be the ozone treatment ratio θ. θn ≠ θp
In the above case, the larger value can be set to θ, and if there is no problem even if the other decomposition product, nitrogen or phosphorus, is generated excessively, the value can be set to θ. In the case where excessively generated nitrogen or phosphorus has a bad effect, a value as large as possible within the range where there is no influence is set to θ, and insufficient nitrogen or phosphorus can be added.

[0022] As can be seen from equation (1), the value of the ozone treatment rate θn are you adjusted according to the setting sludge load with C / N ratio of the liquid to be treated (Rn) (LV / X) . Further, as can be seen from the equation [2], the value of the ozone treatment ratio θp is also C /
That regulation <br/> be in accordance with the P ratio (Rp) and setting sludge load (LV / X).

FIG. 3 is a graph showing the relationship between the ozone treatment ratio θ and the sludge activity, and FIG. 4 is a graph showing the relationship between the ozone injection rate and the biodegradation rate of the ozone-treated sludge. As shown in FIG. 3, the sludge activity is not affected until the ozone treatment ratio θ is about 0.5 day ⁻¹ . This means that the sludge activity of the aerobic treatment system is maintained if less than half of the activated sludge retained in the aerobic treatment system is subjected to ozone treatment per day as extracted sludge. Therefore, the upper limit of the ozone treatment ratio θ is set to about 0.5 day ⁻¹ .

The upper limit of the ozone treatment ratio θ is 0.5 day ⁻¹
The value of degree is a sufficiently practical value. That is, as can be seen from the above formulas [1] and [2], the ozone treatment ratio θ is proportional to the sludge load. Therefore, if the sludge load is set low, the value of the ozone treatment ratio θ becomes low, that is, 0.5 day. It can be controlled to ^-1 or less. For example,
The ozone treatment ratio θn required when treating a wastewater containing no nitrogen is θn = (En / C
n) It becomes LV / X. Since the sludge load is generally operated at about 0.3 kg-C / kg-SS / day in a normal aerobic treatment, the ozone treatment ratio θn in this case is used.
Is 0.07 / 0.13 × 0.3 = 0.16 day ⁻¹
Which is sufficiently practical. In addition, the ozone treatment ratio θp required when treating a wastewater containing no phosphorus is θp = (Ep / Cp) LV / X from the above equation [2], and the sludge load is 0.3 kg−C / kg−. If the operation is performed at about SS / day, the value of the ozone treatment ratio θp is equal to 0.1.
02 / 0.016 × 0.3 = 0.38 day ⁻¹ ,
It is practical enough.

As shown in FIG. 4, the biodegradability of the ozone-treated sludge tends to deteriorate in the region where the ozone injection rate into the sludge is low, and is 0.02 g-O ₃ / g-S.
If it is less than S, it is significantly reduced. Therefore, the ozone treatment can reduce the ozone injection rate per drawn sludge to 0.02 mg-O ₃ / mg.
-SS or more, preferably 0.05 mg-O ₃ / mg-S
It is desirable to carry out at S or higher. On the other hand, the upper limit of the ozone injection rate is not limited, but is 0.2 g-O ₃ / g from the viewpoint of cost.
-SS or less, preferably it is desirable to less _{0.1g-O 3 / g-SS} . By performing ozone treatment at such an ozone injection rate, the sugar chain length of the cell wall of the aerobic microorganism is reduced, and the biodegradability is greatly improved.

When a solubilization treatment other than the ozone treatment is employed, values corresponding to Cn and Cp are obtained by a preliminary test or the like, and using these values, solubilization is performed in the same manner as in the equations [1] and [2]. The processing ratio can be determined.

[0027]

Embodiments of the present invention will be described below. 5 and 6 are flow sheets showing an aerobic treatment apparatus for nitrogen and / or phosphorus deficient organic effluent of the embodiment, respectively. FIG. 5 shows an example in which sludge is extracted from an aeration tank and ozone treatment is performed, and FIG. The example which pulls out sludge from a sludge separation part and performs ozone treatment is shown.

5 and 6, the aerobic treatment system 1
Is composed of an aeration tank 11 and a sludge separation unit 12. The aeration tank 11 has a liquid passage 13 to be treated and a return sludge passage 1.
4 communicates, and a diffuser 15 is provided at the bottom,
The air supply path 16 is in communication. A communication path 17 communicates from the aeration tank 11 to the sludge separation unit 12. Sludge separation unit 12
A liquid passage 18 communicates with the upper part of the apparatus, and a sludge extraction path 19 communicates with the lower part. The sludge extraction line 19 is branched into return sludge line 14 and excess sludge discharge passage 20 with a pump P ₁ in the case of FIG. 5, return sludge line 14 and excess sludge having a pump P ₁ in the case of FIG. 6 branches into the extracted sludge passage 22 having a discharge passage 20 and the pump P _2.

The ozone treatment system 2 has an ozone treatment tank 21 and a drawn sludge passage 22 equipped with a pump P ₂ and an exhaust ozone passage 2.
3 communicates with the upper part, and the ozone supply path 24 and the ozone treated sludge path 25 communicate with the lower part. The drawn sludge path 22
In FIG. 5, the ozone treatment tank 21 is communicated from the aeration tank 11, and in FIG. 6, from the sludge extraction passage 19 of the sludge separation unit 12. The ozonized sludge passage 25 is connected from the ozone treatment tank 21 to the aeration tank 11 in both FIG. 5 and FIG.

5 and 6, the aerobic processing system 1 introduces the liquid to be processed into the aeration tank 11 from the liquid path 13 to be processed. Then, the sludge returned from the return sludge passage 14 and the activated sludge in the aeration tank 11 are mixed, and the air supplied from the air supply passage 16 is diffused from the diffuser 15 to perform aeration, thereby performing aerobic treatment. Do. A part of the mixture in the aeration tank 11 is connected to the communication channel 1
7 to a sludge separation section 12 to perform solid-liquid separation. The separated liquid separated here is discharged as a processing liquid from the processing liquid passage 18, and the separated sludge is drawn out from the sludge extraction passage 19, and a part of the separated sludge is returned from the return sludge passage 14 to the aeration tank 11 by the pump P ₁ . In the case of FIG. 5, the remainder is discharged from the excess sludge discharge passage 20 to the outside of the system, and in the case of FIG. 6, the sludge is introduced into the ozone treatment system 2 from the extracted sludge passage 22. Discharge.

In the ozone treatment system 2, the extracted sludge is circulated from the aeration tank 11 in FIG. 5 and from the sludge extraction passage 19 in FIG. 6 through the extraction sludge passage 22 by the pump P 2 to the ozone treatment tank 21. The ozone treatment is performed by bringing the ozone into contact with the ozone supplied from the ozone supply path 24. At this time,
The ratio of the amount of withdrawn sludge to the total amount of sludge in the aerobic treatment system 1 is
C / N ratio and / or C / P ratio of liquid to be treated and set sludge
Adjust according to the load . The ozone-treated sludge is returned from the ozone-treated sludge passage 25 to the aeration tank 11 as a nitrogen and / or phosphorus source, and is subjected to aerobic treatment.

In the embodiment shown in FIGS. 5 and 6, the sludge separating section 12
Although a sedimentation tank is shown in the figure, a membrane separation device or another sludge separation device may be used. Further, the aerobic treatment system 1 is not limited to the standard activated sludge treatment, and other aerobic treatment devices can be employed.

The test results will be described below. Comparative Example 1 Glucose was used as an organic substance source, and ammonia as a nitrogen source was added so as to be 5% by weight of the carbon source to prepare an organic waste liquid. This organic waste liquid was used as a liquid to be treated, and activated sludge treatment was performed under the conditions of a tank load of an aeration tank of 0.6 kg-C / m ³ / day and SRT = 10 days. As a result, the amount of surplus sludge generated was 0.38 kg-SS / m ³ / day, and the sludge concentration in the aeration tank was 4000 mg / l.

Comparative Example 2 The activated sludge treatment was performed in the same manner as in Comparative Example 1 except that the tank load and the sludge load were set to the same conditions as in Comparative Example 1, and no nitrogen source was added to the organic wastewater. As a result, one week after the start of the treatment, the sludge was separated and dismantled, and could not be treated.

Example 1 Organic sludge containing no nitrogen was treated with activated sludge by the treatment apparatus shown in FIG. Ozone treatment conditions are ozone injection rate 0.0
5 mg-O ₃ / mg-SS, θn = 0.3 day ⁻¹ . The tank load, sludge load and SRT were the same as in Comparative Example 1. As a result, the sludge concentration in the aeration tank was stabilized at 4000 mg / l, and the treatment liquid did not deteriorate during the treatment period of three months without adding any other nitrogen source.

COMPARATIVE EXAMPLE 3 Glucose was used as an organic substance source, and phosphoric acid as a phosphorus source was added so as to be 1% by weight of the carbon source to prepare an organic effluent. This organic waste liquid was used as a liquid to be treated, and activated sludge treatment was performed under the conditions of a tank load of an aeration tank of 0.6 kg-C / m ³ / day and SRT = 10 days. As a result, the amount of excess sludge generated was 0.38 kg-SS / m ³ / day, and the sludge concentration in the tank was 4
000 mg / l.

Comparative Example 4 The tank load and the sludge load were set to the same conditions as in Comparative Example 3, and the activated sludge treatment was performed in the same manner as in Comparative Example 3 without adding a phosphorus source to the organic wastewater. As a result, one week after the start of the treatment, the sludge was separated and dismantled, and could not be treated.

Example 2 An organic effluent containing no phosphorus was treated with activated sludge by the treatment apparatus shown in FIG. Ozone treatment conditions are ozone injection rate 0.0
5 mg-O ₃ / mg-SS, θp = 0.3 day ⁻¹ . The tank load, sludge load, and SRT were the same as in Comparative Example 3. As a result, the sludge concentration in the aeration tank was stabilized at 4000 mg / l, and the treatment liquid did not deteriorate during the treatment period of three months without adding any other phosphorus source.

Comparative Example 5 Petrochemical wastewater (BOD 1000 mg / l, nitrogen 5 m
g / l, no phosphorus) was used as the liquid to be treated, and the organic wastewater deficient in nitrogen and phosphorus was subjected to activated sludge treatment by the treatment apparatus in FIG. Aeration tank load 0.6 kg-C / m ³ / da
y, initial sludge concentration in the tank 4000 mg / l, SRT = 10
When the treatment was started under the condition of one day, the organic acid (acetic acid and butyric acid) was 100 to 200 mg / l in the treatment liquid after one week.
The BOD removal rate gradually decreased, and after one month, the sludge was dismantled and could not be processed.

Example 3 Ozone treatment was performed in the same manner as in Example 2 using the processing apparatus shown in FIG. 5, and the other processing conditions were the same as in Comparative Example 5. As a result, the concentration of the sludge in the aeration tank was stabilized at 4000 mg / l, and the treatment liquid did not deteriorate during the treatment period of three months without adding any other nitrogen source or phosphorus source.

Example 4 In Example 3, 90% of the extracted sludge was used instead of the ozone treatment.
At 4 ° C. for 4 hours, and the other treatment conditions were the same as in Comparative Example 5. The sludge concentration in the tank was stable at 6000 mg / l. During the monthly treatment period, the treatment liquid did not deteriorate.

Example 5 In Example 4, sulfuric acid was added at the time of heating and dissolving the extracted sludge, the pH was set to 2.8, and the sludge was solubilized, neutralized, and returned to the aeration tank. Other processing conditions were Comparative Example 5.
The sludge concentration in the tank was 4000 mg / l
, And the treatment liquid did not deteriorate during the treatment period of three months without adding any other nitrogen source or phosphorus source.

Example 6 In Example 4, sodium hydroxide was added at the time of heating and dissolving the extracted sludge, the pH was set to 12, solubilization was performed, and then neutralized and returned to the aeration tank. Other treatment conditions were the same as in Comparative Example 5, and the sludge concentration in the tank was 400
It was stabilized at 0 mg / l, and the treatment liquid did not deteriorate during the treatment period of three months without adding any other nitrogen source or phosphorus source.

[0044]

As described above, according to the present invention, in the aerobic treatment of nitrogen- and / or phosphorus-deficient organic effluent,
After solubilizing the activated sludge extracted from the aerobic treatment system, it is introduced into the aerobic treatment system as a nitrogen and / or phosphorus source, and the aerobic treatment system withdraws the total sludge amount.
The percentage of sludge is reduced by nitrogen and / or phosphorus deficient organic waste.
C / N ratio and / or C / P ratio of liquid and set sludge load
Since so as to adjust in accordance with, when the aerobic treatment of nitrogen and / or phosphorus deficiency organic drainage, the amount of nitrogen and phosphorus source added can be reduced the, also depending on the conditions the addition of nitrogen and phosphorus sources It can be processed without doing so.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the ozone injection rate for sludge and the residual rate of organic matter.

FIG. 2 is a graph showing the relationship between the amount of Kjeldahl nitrogen and the amount of ammonia nitrogen when an ozone-treated sludge is subjected to aerobic treatment.

FIG. 3 is a graph showing a relationship between an ozone treatment ratio and sludge activity.

FIG. 4 is a graph showing a relationship between an ozone injection rate and a biodegradation rate.

FIG. 5 is a flow sheet showing the processing apparatus of the embodiment.

FIG. 6 is a flow sheet showing a processing apparatus of another embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 aerobic treatment system 2 ozone treatment system 11 aeration tank 12 sludge separation unit 13 liquid passage to be treated 14 return sludge passage 15 diffuser 16 air supply passage 17 communication passage 18 treatment liquid passage 19 sludge extraction passage 20 excess sludge discharge passage 21 Ozone treatment tank 22 Extraction sludge passage 23 Waste ozone passage 24 Ozone supply passage 25 Ozone treatment sludge passage

Claims (1)

(57) [Claims] 1. A method for aerobically treating a nitrogen- and / or phosphorus-deficient organic effluent in the presence of activated sludge containing aerobic microorganisms, comprising: extracting activated sludge from an aerobic treatment system; After solubilization, it is introduced into the aerobic treatment system as a source of nitrogen and / or phosphorus, and all sludge in the aerobic treatment system
The ratio of the amount of drawn sludge to the amount
C / N ratio and / or C / P ratio of organic deficient organic effluent
An aerobic treatment method for nitrogen- and / or phosphorus-deficient organic effluent, which is adjusted according to a set sludge load .