JPH06254583A - Aerobic treatment of nitrogen and/or phosphorus-deficient organic waste liquid - Google Patents

Abstract

PURPOSE:To anaerobically treat a nitrogen and/or phosphorusdeficient org. waste liq. with the amts. of nitrogen and phosphorus sources to be added reduced or without adding the nitrogen and phosphorus sources if the conditions permit. CONSTITUTION:A nitrogen and phosphorus-deficient liq. to be treated is introduced into an aeration tank 11 from a liq. line 13, the return sludge from a line 14 is mixed with the activated sludge in the aeration tank 11, aeration is conducted, the activated sludge in the aeration tank 11 is drawn out into an ozone treating tank 21 through a line 22 and brought into contact with the ozone supplied from a line 24, treated with ozone and solubilized, and the ozone-treated sludge is returned to the aeration tank 11 from a line 25. The aerated liq. is introduced into a sludge separation part 12 and separated into solid and liq.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is directed to the aerobic treatment of nitrogen and / or phosphorus deficient organic effluents.
Or, it relates to a method for aerobic treatment of phosphorus-deficient organic drainage.

[0002]

2. Description of the Related Art Conventionally, organic effluent deficient in nitrogen and / or phosphorus has been treated by an aerobic treatment method such as an activated sludge method. In this case, nitrogen and phosphorus necessary for the growth of aerobic microorganisms are not covered. It is added to the processing liquid. Generally, the aerobic treatment method of waste liquid is a method of treating by utilizing microorganisms, and therefore, it is necessary to treat under the condition that aerobic microorganisms grow sufficiently and are active. For example, in terms of nutrition, nitrogen is about 1/20 times 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. It is said to be necessary.

Therefore, when treating an organic drainage deficient in nitrogen and / or phosphorus, conventionally, a compound such as ammonium salt or phosphate is used as a nitrogen and / or phosphorus source in the drainage so as to attain the above value. I am adding. However, in such a conventional method, the cost of nitrogen and phosphorus sources is high, and it is difficult to add necessary and sufficient nitrogen and phosphorus. If added excessively, nitrogen and phosphorus will leak into the treated water, resulting in poor water quality. May cause.

On the other hand, Japanese Examined Patent Publication No. 57-19719 discloses that excess sludge is destroyed by ultrasonic waves, ground by a homogenizer,
Disclosed is a method for treating excess sludge in which microbial somatic cells are destroyed by milling with a mixer, destruction by high-pressure and instantaneous decompression expansion, or oxidative decomposition by ozone gas, and the obtained liquid is aerobically digested.

However, this method is a method for reducing the volume of excess sludge, and a liquid obtained by destroying microbial somatic cells is used as a nitrogen and / or phosphorus source, and such liquid is deficient in nitrogen and / or phosphorus. It is not disclosed that the waste liquid is aerobically treated by adding it to the treated liquid.

In Japanese Patent Publication No. Sho 49-11813, excess sludge produced by aerobic treatment of organic waste liquid is hydrolyzed by adding an alkali and heating, and the decomposed liquid is neutralized and aerobic treated. A method for treating excess sludge that is returned to the device has been proposed.

However, this method is also a method for reducing the volume of excess sludge, and an alkali decomposition solution is used as a nitrogen and / or phosphorus source, and such solution is deficient in nitrogen and / or phosphorus. To treat the effluent aerobically by adding to the above is not disclosed.

[0008]

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

[0009]

The present invention provides a method for aerobically treating nitrogen- and / or phosphorus-deficient organic effluent in the presence of activated sludge containing aerobic microorganisms. Is extracted, and the extracted sludge is solubilized, and then introduced into an aerobic treatment system, which is an aerobic treatment method for nitrogen- and / or phosphorus-deficient organic waste liquid.

The effluent to be treated in the present invention is an organic effluent deficient in nitrogen or phosphorus, or both of them. Generally, the nitrogen content is 1 / BOD of 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 the drainage or 1/5 of carbon
It is an organic drainage of 0 times or less.

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. A known method can be adopted as the aerobic treatment.For example, in an aerobic treatment system equipped with an aeration tank and a sludge separation unit, organic waste liquid is introduced into the aeration tank and mixed with return sludge and activated sludge in the aeration tank. Then, the standard activated sludge method in which the mixed liquid in the aeration tank is guided to the sludge separation section for 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 the sludge separation section. In the latter case, it corresponds to solubilizing the excess sludge. The solubilized sludge is preferably introduced into the aeration tank, but not limited to this.

Examples of the method for solubilizing sludge include oxidative decomposition with an oxidizing agent such as ozone and hydrogen peroxide, mashing, acid dissolution, alkali dissolution, heat decomposition, and acid / alkali addition 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, and can be solubilized, for example, by contacting ozone-containing air with sludge. Oxidative decomposition with hydrogen peroxide is a method of solubilizing sludge by contacting it with hydrogen peroxide, and can be solubilized by leaving sludge in the presence of hydrogen peroxide, for example.

Grinding is a method of solubilizing sludge by breaking it with a ball mill or the like. The acid dissolution is a method of solubilizing sludge by contacting it with an acid, and as the acid, for example, hydrochloric acid, sulfuric acid or the like can be used. Alkali dissolution is a method of solubilizing sludge by bringing it into contact with alkali, and as the alkali, for example, sodium hydroxide, potassium hydroxide or the like can be used. Thermal decomposition is a method of heating sludge to solubilize it. These methods can be combined, and for example, the acid / alkali addition thermal decomposition is a method of solubilizing by combining acid dissolution, alkali dissolution and thermal decomposition.

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

As shown in FIG. 1, since the sludge itself is not mineralized by the ozone treatment, the SS of 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. Further, as shown in FIG. 2, when the ozone-treated sludge is aerobically treated, the amounts of Kjeldahl nitrogen and ammonia nitrogen remaining after that are almost equal, and most of the Kjeldahl nitrogen is ammonia nitrogen. I understand. Therefore, it can be seen that the ozone-treated sludge is a good nitrogen source containing almost no persistent organic nitrogen.

Therefore, the ozone-treated sludge contains about 13% by weight of nitrogen, about 17% by weight of carbon, about 1.6% by weight of phosphorus, and about 2.2% by weight of carbon in the sludge. I understand. Since the ozone-treated sludge contains a certain amount of nitrogen and phosphorus as described above, the ozone-treated sludge can be used as a nitrogen and / or phosphorus source.

Next, the ratio (ozone treatment ratio) θ of the amount of extracted sludge to the total amount of sludge in the aerobic treatment system when the activated sludge is withdrawn from the aerobic treatment system and subjected to ozone treatment will be described. Ozone treatment ratio when ozone-treated sludge is used as a nitrogen source: θn (day ^-1 ) Ozone treatment ratio when ozone-treated sludge is used as a phosphorus source: θp (day ^-1 ) C / N ratio of treated liquid: 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 required 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 rate of ozone-treated sludge: Cp (g-P / g-S)
S) = 0.016 (g-P / g-SS) Sludge concentration in aeration tank: X (g-SS / liter) Carbon conversion tank load: LV (g-C / liter / day) The amount of nitrogen required for (En-1 / Rn)
It is represented by LV. Therefore, the amount of ozone-treated sludge required when used as a nitrogen source is (En-1 / Rn) LV = C
It is represented by nθnX. If this equation is modified, θn = (En−1 / Rn) LV / X / Cn [1], and the ozone treatment ratio θn can be obtained. The amount of phosphorus required for one 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. When this equation is modified, θp = (Ep−1 / Rp) LV / X / Cp [2], and the ozone treatment ratio θp is obtained.

Therefore, if the ozone treatment is carried out at the ozone treatment ratios θn and θp of the formula [1] or [2], the amounts of nitrogen and phosphorus necessary for aerobically treating the organic matter are sufficient, Aerobic treatment is possible without the addition of nitrogen and / or phosphorus sources. On the other hand, when the ozone treatment is carried out at a value smaller than the ozone treatment ratio of the formula [1] or [2], the amount of nitrogen or phosphorus necessary for aerobically treating the organic substance is insufficient, so that ammonia, ammonium salt, Addition of other nitrogen and / or phosphorus sources such as phosphoric acid or phosphate is required. In either case, it is necessary to add sufficient nitrogen and / or phosphorus sources to form sludge at the beginning of treatment.

Therefore, when θn = θp, θn or θ
p can be an ozone treatment ratio θ. θn ≠ θp
In the above case, the larger value can be taken as θ, and if there is no problem even if the other decomposition product, nitrogen or phosphorus, is overproduced, that value can be taken as θ. When the excessively generated nitrogen or phosphorus has a bad effect, the largest possible value can be set as θ within a range without any adverse effect, and the insufficient nitrogen or phosphorus can be added.

As can be seen from the equation [1], the value of the ozone treatment ratio θn may be adjusted according to the C / N ratio (Rn) of the liquid to be treated and the set sludge load (LV / X). Also, the formula [2]
As can be seen from the above, the value of the ozone treatment ratio θp may be adjusted according to the C / P ratio (Rp) of the liquid to be treated and the set 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 ozone treatment rate θ does not affect the sludge activity up to about 0.5 day ⁻¹ . This means that if one half or less of the activated sludge retained in the aerobic treatment system is treated with ozone as drawn-out sludge per day, the sludge activity of the aerobic treatment system will be maintained. Therefore, the upper limit of the ozone treatment ratio θ is 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 equations [1] and [2], since the ozone treatment ratio θ is proportional to the sludge load, if the sludge load is set low, the value of the ozone treatment ratio θ becomes low, that is, 0.5 day. ^-1 can be controlled below. For example,
The ozone treatment ratio θn required when treating the waste liquid containing no nitrogen is calculated from the above formula [1] by 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 normal aerobic treatment, the ozone treatment ratio θn in this case is
The value of is 0.07 / 0.13 × 0.3 = 0.16day ^-1
And is practical enough. Further, the ozone treatment ratio θp required when treating the waste liquid containing no phosphorus is θp = (Ep / Cp) LV / X from the above formula [2], and the sludge load is 0.3 kg-C / kg-. When operating at about SS / day, the value of the ozone treatment ratio θp is 0.
02 / 0.016 × 0.3 = 0.38day ⁻¹ ,
Practical enough.

As shown in FIG. 4, the biodegradability of the ozone-treated sludge tends to deteriorate in a region where the ozone injection rate into the sludge is low, and 0.02 g-O ₃ / g-S is present.
If it is less than S, it is significantly reduced. Therefore, in the ozone treatment, the ozone injection rate per extracted sludge was 0.02 mg-O ₃ / mg.
-SS or more, preferably 0.05mg-O ₃ / mg-S
It is desirable to carry out at S or higher. On the other hand, although the upper limit of the ozone injection rate is not limited, it is 0.2 g-O ₃ / g in terms 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 biodegradability is greatly improved.

When a solubilization treatment other than ozone treatment is adopted, the values corresponding to Cn and Cp are obtained by preliminary tests and the like, and the solubilization is carried out using these values in the same manner as in formulas [1] and [2]. The processing rate can be calculated.

[0027]

EXAMPLES Examples of the present invention will be described below. FIG. 5 and FIG. 6 are flow sheets showing an aerobic treatment device for nitrogen- and / or phosphorus-deficient organic waste liquids of Examples, respectively. FIG. 5 shows an example of drawing sludge from an aeration tank to perform ozone treatment, and FIG. An example is shown in which sludge is drawn from the sludge separation section and ozone treatment is performed.

In FIGS. 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 is in contact with the air diffuser 15 at the bottom,
The air supply path 16 is in communication. A communication path 17 connects the aeration tank 11 to the sludge separation unit 12. Sludge separation unit 12
The treatment liquid passage 18 communicates with the upper part of the sludge, and the sludge withdrawal passage 19 communicates with the lower part. In the case of FIG. 5, the sludge withdrawal path 19 branches into the return sludge path 14 having the pump P ₁ and the excess sludge discharge path 20, and in the case of FIG. 6, the return sludge path 14 having the pump P ₁ and the excess sludge. It branches into a discharge passage 20 and a drawn-out sludge passage 22 provided with a pump P ₂ .

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

In the method for treating organic waste liquid by the above-mentioned treatment apparatus, in both cases of FIG. 5 and FIG. 6, in the aerobic treatment system 1, the treatment liquid is introduced from the treatment liquid passage 13 into the aeration tank 11. , Mixed with the return sludge returned from the return sludge passage 14 and the activated sludge in the aeration tank 11, and aerating the air supplied from the air supply passage 16 from the air diffuser 15 to perform aerobic treatment. To do. Part of the mixed liquid in the aeration tank 11 is the communication path 1
7 is led to the sludge separation part 12, and solid-liquid separation is performed. The separated liquid separated here is discharged as a processing liquid from the processing liquid path 18, the separated sludge is drawn out from the sludge drawing path 19, and a part thereof is returned to the aeration tank 11 from the returning sludge path 14 by the pump P ₁ . In the case of FIG. 5, the rest is discharged from the excess sludge discharge passage 20 to the outside of the system, in the case of FIG. 6, it is introduced from the extracted sludge passage 22 into the ozone treatment system 2, and the rest is discharged from the excess sludge discharge passage 20 to the outside of the system. Discharge.

In the ozone treatment system 2, the extracted sludge is circulated to the ozone treatment tank 21 from the aeration tank 11 in the case of FIG. 5 and from the sludge extraction passage 19 in the case of FIG. 6 through the extraction sludge passage 22 by the pump P ₂ , respectively. The ozone treatment is performed by contacting the ozone supplied from the ozone supply path 24. 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 subjected to aerobic treatment.

In the embodiment shown in FIGS. 5 and 6, the sludge separating section 12
Although the settling tank is shown as an example, 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 adopted.

The test results will be described below. Comparative Example 1 An organic waste liquid was prepared by using glucose as an organic material source and adding ammonia as a nitrogen source so as to be 5% by weight of the carbon source. Using this organic waste liquid as the liquid to be treated, activated sludge treatment was carried out under the conditions of a tank load of 0.6 kg-C / m ³ / day and SRT = 10 days. As a result, the amount of excess sludge produced 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 carried out 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 waste liquid. As a result, the sludge was separated and dismantled one week after the treatment was started, and the treatment could not be performed.

Example 1 The organic effluent containing no nitrogen was treated with activated sludge by the treatment apparatus shown in FIG. Ozone treatment condition is ozone injection rate 0.0
Was 5mg-O ₃ /mg-SS,θn=0.3day ^-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 stable at 4000 mg / l, and the treatment liquid did not deteriorate during the treatment period of 3 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 drainage liquid. Using this organic waste liquid as the liquid to be treated, activated sludge treatment was carried out under the conditions of a tank load of 0.6 kg-C / m ³ / day and SRT = 10 days. As a result, the amount of excess sludge produced was 0.38 kg-SS / m ³ / day, and the sludge concentration in the tank was 4
It was 000 mg / l.

Comparative Example 4 The activated sludge treatment was carried out in the same manner as in Comparative Example 3 except that the tank load and the sludge load were set to the same conditions as in Comparative Example 3, and no phosphorus source was added to the organic waste liquid. As a result, the sludge was separated and dismantled one week after the treatment was started, and the treatment could not be performed.

Example 2 An organic sludge containing no phosphorus was treated with activated sludge by the treatment apparatus shown in FIG. Ozone treatment condition is ozone injection rate 0.0
Was 5mg-O ₃ /mg-SS,θp=0.3day ^-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 stable at 4000 mg / l, and the treatment liquid did not deteriorate during the treatment period of 3 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 waste liquid deficient in nitrogen and phosphorus was treated with activated sludge by the treatment device of FIG. Tank load of aeration tank 0.6kg-C / m ³ / da
y, sludge concentration in the initial tank 4000 mg / l, SRT = 10
When the treatment was started under the conditions of one day, 100 to 200 mg / l of organic acids (acetic acid and butyric acid) were contained in the treatment liquid after 1 week.
After detection, the BOD removal rate gradually decreased, and one month later, the sludge was dismantled and the treatment could not be performed.

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

Example 4 In Example 3, 90% of extracted sludge was used instead of ozone treatment.
When the solution was heated and dissolved at 4 ° C. for 4 hours and the other processing conditions were the same as in Comparative Example 5, the sludge concentration in the tank was stable at 6000 mg / l, and it was 3 or more without adding other nitrogen source or phosphorus source. The treatment liquid did not deteriorate during the monthly treatment period.

Example 5 In Example 4, sulfuric acid was added when the drawn sludge was heated and dissolved, the pH was set to 2.8, the solution was solubilized, and then neutralized and returned to the aeration tank. Other processing conditions are Comparative Example 5
The sludge concentration in the tank was 4000 mg / l.
The treatment liquid did not deteriorate during the treatment period of 3 months without adding any other nitrogen source or phosphorus source.

Example 6 In Example 4, sodium hydroxide was added when the drawn sludge was heat-dissolved, the pH was set to 12, the solubilization was performed, and then the sludge was 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 stable at 0 mg / l, and the treatment liquid did not deteriorate during the treatment period of 3 months even if no other nitrogen source or phosphorus source was added.

[0044]

As described above, according to the present invention, in aerobic treatment of nitrogen- and / or phosphorus-deficient organic wastewater,
Since the activated sludge drawn from the aerobic treatment system was solubilized and then introduced into the aerobic treatment system, the nitrogen and / or phosphorus source added during aerobic treatment of the nitrogen- and / or phosphorus-deficient organic waste liquid. Can be reduced, and depending on the conditions, the treatment can be performed without adding a nitrogen or phosphorus source.

[Brief description of drawings]

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

FIG. 2 is a graph showing the relationship between the amount of Kjeldahl nitrogen and the amount of ammonia nitrogen in the case of aerobically treating ozone-treated sludge.

FIG. 3 is a graph showing the relationship between 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]

 1 Aerobic treatment system 2 Ozone treatment system 11 Aeration tank 12 Sludge separation part 13 Liquid passage to be treated 14 Returned sludge passage 15 Air diffuser 16 Air supply passage 17 Connecting passage 18 Treatment liquid passage 19 Sludge extraction passage 20 Excess sludge discharge passage 21 Ozone treatment tank 22 Extraction sludge passage 23 Exhaust ozone passage 24 Ozone supply passage 25 Ozone treatment sludge passage

Claims (1)

[Claims] 1. A method for aerobically treating nitrogen- and / or phosphorus-deficient organic effluent in the presence of activated sludge containing aerobic microorganisms, in which the activated sludge is drawn from the aerobic treatment system and the extracted sludge can be treated. A method for aerobic treatment of nitrogen- and / or phosphorus-deficient organic effluent, which comprises introducing into aerobic treatment system after solubilization treatment.