JP2001252689A - Treatment method for organic waste water and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for reducing the consumption of chemicals in an MPA treatment method which removes phosphor and nitrogen as ammonium magnesium phosphate crystal from waste water which contains high concentration organic material, phosphor and nitrogen, and for drastically improving the efficiency of removal of nitrogen and phosphor. SOLUTION: This treatment method of organic waste water incorporates a process (1) in which phosphor and nitrogen in the waste water is made to a form of ammonium magnesium phosphate and taken out the same outside the system and, therein, is characterized in that a vacuum treatment process (2) in which the waste water which contains phosphor and nitrogen is subjected to vacuum treatment prior to the process (1). The treatment apparatus of organic waste water in which the organic waste water is biologically treated is provided with a ammonium magnesium phosphate reaction tank passing through a vacuum treatment device in the treatment course of the organic waste water of the treated water thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating organic wastewater in a sewage treatment plant and various wastewater treatment facilities, and more particularly, to a digestion / desorption solution of human waste and septic tank sludge, and digestion of sludge. In the treatment of removing phosphorus and the like as magnesium ammonium phosphate crystals from organic wastewater containing high concentrations of organic matter, phosphorus and nitrogen such as liquids and wastewater from chemical factories, the amount of chemicals used is reduced and nitrogen and phosphorus are removed. TECHNICAL FIELD The present invention relates to a processing method and a processing apparatus for greatly improving the removal efficiency of methane.

[0002]

2. Description of the Related Art Conventional general methods for simultaneous denitrification and phosphorus removal include biological treatment methods such as an anaerobic anoxic aerobic method, an anaerobic aerobic method, a coagulation sedimentation method, and an alumina adsorption method. Are often combined. In addition, in recent years, MAP treatment methods for removing phosphorus and nitrogen in wastewater as magnesium ammonium phosphate (MAP) crystals for return water or anaerobic digestion / desorbed liquid generated in the process of human waste treatment or sewage treatment have been proposed. Attempted.

[0003]

However, of these treatment methods, the anaerobic anoxic aerobic method has a problem that the treatment performance is not stable due to a change in the water environment or an external environment due to seasonal fluctuation. The method combining the anaerobic-aerobic method and the coagulation-sedimentation method has the problems that the processing steps are complicated and that the running cost including the cost of chemicals is large. M
In the AP treatment method, the operation is less complicated than the above two methods. In particular, the recovery of phosphorus can be performed stably, and the recovered MAP has an added value as an excellent fertilizer, and the effective use of resources. Therefore, it can be said that this is an excellent technology for removing phosphorus and nitrogen. However, also in the case of the MAP method, chemical costs such as sodium hydroxide as a pH adjuster and magnesium chloride as an additive are required, and the SS concentration is relatively low (300%).
Only about 0 mg / liter), about 60 to 70% of the concentration of orthophosphate phosphorus can be removed. That is, the fine MAP particles contained in the high-concentration sludge are hardly collected, and are merely disposed together with the sludge. Thus, there is a problem as a technology for recovering nitrogen and phosphorus.

An object of the present invention is to solve the above-mentioned problems of the prior art. That is, the present invention relates to an organic wastewater treatment system, particularly an organic wastewater containing organic matter, nitrogen and phosphorus, for example, a high concentration of an organic wastewater, a digestion and desorption solution of human waste and a septic tank sludge, a digestion solution of sludge, and a chemical factory wastewater. MAP treatment for removing magnesium ammonium phosphate crystals from wastewater containing organic matter, phosphorus and nitrogen, which reduces the amount of chemicals used and greatly improves nitrogen and phosphorus removal efficiency Is the subject.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and in addition to the MAP treatment step of removing phosphorus and nitrogen in organic waste water as magnesium ammonium phosphate crystals. The present inventors have found that the addition of the decompression treatment step significantly reduces nitrogen and phosphorus removal efficiency as well as the amount of drug used, and has completed the present invention.

That is, the present invention has solved the above-mentioned problems by the following organic wastewater treatment method and apparatus. (1) A method for treating organic wastewater, which comprises the step (1) of taking out phosphorus and nitrogen in the wastewater in the form of magnesium ammonium phosphate and taking it out of the system. )) A method of treating organic wastewater, which comprises a step (2) of reducing the pressure of the wastewater containing phosphorus and nitrogen before the step (b). (2) Organic wastewater is treated in a biological reaction tank, sludge generated in the biological reaction tank is introduced into an anaerobic fermentation step, and phosphorus and nitrogen in digested sludge generated during or after the anaerobic fermentation step are removed. A step (1) in which the digested sludge containing phosphorus and nitrogen is subjected to a reduced pressure treatment before or after the step (1) in a treatment method incorporating a step (1) of taking out the system in the form of magnesium ammonium phosphate. A method for treating organic wastewater, comprising the step (2). (3) In a wastewater treatment device for biologically treating organic wastewater, a magnesium ammonium phosphate reaction tank passing through a reduced-pressure treatment device is provided in a treatment route for the organic wastewater or the treated water. Organic wastewater treatment equipment.

(4) In a wastewater treatment apparatus for biologically treating organic wastewater, phosphoric acid passing through a reduced-pressure treatment apparatus is provided in a treatment path for sludge from a biological reaction tank for biologically treating organic wastewater. An organic wastewater treatment apparatus, comprising: a magnesium ammonium reaction tank; or a decompression device passing through a magnesium ammonium phosphate reaction tank. (5) In a wastewater treatment apparatus for biologically treating organic wastewater, first solid-liquid separation is provided, which is connected to an inflow pipe for treated water that supplies organic wastewater as inflow water and has a concentrated sludge delivery pipe to a dehydration apparatus. A tank and an intermediate separation tank provided with a concentrated sludge delivery pipe to a dewatering device on the separated water discharge side, then a biological reaction tank, and a final solid-liquid separation tank further provided with a concentrated sludge delivery pipe to an anaerobic fermentation tank, A cake combustion device provided with energy recovery means for the anaerobic fermenter on the cake discharge side of the dehydrator, and magnesium ammonium phosphate acting reversibly on the discharge side of the anaerobic fermenter provided with a methane gas recovery device A reaction tank, further comprising a reduced pressure processing device, or
An apparatus for treating organic waste water, comprising: a decompression treatment device that acts reversibly on the discharge side of an anaerobic fermentation tank provided with a methane gas recovery device; and a magnesium ammonium phosphate reaction tank.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below together with the operation. As a method to solve the above problems,
The present invention proposes a method for treating organic wastewater comprising a basic treatment flow shown in FIGS. That is, a method for treating an organic wastewater, in which phosphorus and nitrogen in the wastewater are taken out of the system in the form of magnesium ammonium phosphate (1) (referred to as "MAP treatment step")
By incorporating the step (2) of decompressing the wastewater containing phosphorus and nitrogen into the target liquid by discharging the components such as carbon dioxide and hydrogen sulfide dissolved in the target liquid into the gas phase, This will increase the pH in the solution.
As a result, it is possible to reduce the amount of a drug such as sodium hydroxide that has conventionally been required to be added in a relatively large amount as a pH adjuster to the target liquid.

In FIG. 1, an organic waste water is introduced into an inflow SS solid-liquid separation tank 1 to precipitate solids, and the supernatant water is transferred to an intermediate separation tank 6 provided with a membrane separation means (this may not be provided in some cases). The sludge that has settled or the concentrated sludge is sent to the dewatering device 10. The separated water separated in the intermediate separation tank 6 is sent to the biological reaction tank 3, where the separated water is subjected to an aerobic biological reaction by, for example, an activated sludge process, and the sludge is precipitated and separated in the microbial solid-liquid separation tank 5 for purification. Runs off as treated water. In this treatment method, the sludge settled and separated in the microorganism solid-liquid separation tank 5 is discharged out of the system as a concentrated sludge 31. Since the concentrated sludge 31 is one in which phosphorus and nitrogen are more highly concentrated. If phosphorus and nitrogen can be obtained in the form of magnesium ammonium phosphate, valuable resources can be recovered.

Then, when the concentrated sludge 31 is put into the anaerobic fermenter 4 and the anaerobic fermentation step is performed, organic matter is decomposed to generate methane gas, and the digested sludge 41 having a reduced amount of organic matter is obtained. There, it produces digested sludge containing hundreds to thousands of ammonium nitrogen and orthophosphate phosphorus and having a high content of M alkaline components and hydrogen sulfide. All or a part of the digested sludge 41 or the sludge 42 in the course of the digestion process is sent to the decompression device 2 to perform a decompression process. When the digested sludge 41 and the digestive sludge 42 are subjected to reduced pressure, carbon dioxide gas, hydrogen sulfide, and free ammonia are released from the liquid, and the amount of hydroxyl ions increases accordingly. When this solution is sent to the MAP first tank 21 and MgCl ₂ or the like as a Mg source is added, the MAP generation reaction proceeds only by adding a small amount of a pH adjuster such as sodium hydroxide or the like. The MAP first tank 21 has both a function of forming MAP particles and a function of separating MAP particles out of the system. The digested sludge 43 that has passed through the MAP first tank 21 is returned to the anaerobic fermenter 4 and undergoes the anaerobic fermentation process again. The digested sludge 43 reduces the activity of anaerobic fermentation such as carbon dioxide gas, hydrogen sulfide, free ammonia, orthophosphate phosphorus, hydroxyl ion, ammonium ion, etc. in the liquid while passing through the decompression device 2 and the MAP tank 21. Since the substances to be reduced are reduced and some of the microorganisms in the sludge are in a form easily damaged by the decompression treatment and decomposed, the digested sludge 43 to be decomposed by other microorganisms, the sludge 41, The anaerobic fermentation process is more likely to proceed than in the case of No. 42, and the decomposition rate of organic matter in the anaerobic fermenter 4 is improved.

As described above, the sludge can be circulated through the anaerobic fermenter 4, the decompression device 2, and the first MAP tank to increase the decomposition rate by fermentation. And the phosphorus content are collected by the MAP in useful forms, respectively. Further, the MAP may be returned from the first tank to the anaerobic fermenter 4 and circulated. In this case, the anaerobic fermenter 4, the decompressor 2, and the MAP first tank need not be limited to this order. Depending on the properties of the sludge, for example, the anaerobic fermenter 4, the MAP first tank, and the depressurizer 2 are arranged in this order. It is also effective when circulating. Further, the pressure may be returned from the decompression device 2 to the anaerobic fermenter 4 and circulated. In addition, most of the MAP particles precipitated in the sludge in this series of steps are collected in the MAP first tank, but depending on the organic matter decomposition level in the anaerobic fermenter, orthophosphorous phosphorus and ammonium nitrogen are contained in the sludge. May still be present at high concentrations. Therefore, MAP
The digested sludge 41 from which the particles have been removed is subjected to a dehydration treatment after being agglomerated with a polymer coagulant or the like, and the dehydrated filtrate is subjected to MAP second tank, MgCl ₂ or the like as a Mg source, and pH of sodium hydroxide or the like. By adding a regulator, orthophosphorus phosphorus and ammonia nitrogen in the dehydrated filtrate can be recovered as MAP particles.

The conditions for decompression in the decompression device 2 include:
The greater the degree of pressure reduction, the greater the amount of carbon dioxide gas and hydrogen sulfide released, and although effective, the greater the power for pressure reduction. An appropriate degree of reduced pressure is 80 to 360 hpa
s is preferred. On the other hand, the concentrated sludge 1
1 and the concentrated sludge 61 are dewatered, and the dewatered sludge is sent to the cake combustion device 7 where it is burned and energy recovery means 8
It is effective to heat the anaerobic fermenter 4 to promote anaerobic fermentation. Furthermore, the methane gas generated in the anaerobic fermenter 4 can be recovered by the methane gas recovery means 9 and burned separately, and the anaerobic fermenter 4 can be heated by the combustion heat.

As described above, a part of the sludge generated in the biological reaction tank 3 is introduced into the anaerobic fermentation step 4, and the digested sludge 41 is reduced in pressure during or after the anaerobic fermentation step ( By incorporating 2) and the MAP treatment step (1), it is possible to produce digested sludge containing hundreds to thousands of ammonium nitrogen and orthophosphate phosphorus and having a high content of carbonic acid and hydrogen sulfide. With the increase of hydroxyl ions due to decarboxylation and dehydrogen sulfide, the progress of MAP generation is facilitated, and the anaerobic fermentation reaction is promoted by returning the sludge after MAP particle recovery to the anaerobic fermenter. You.

It is desirable to use a deaerator (hereinafter, referred to as a thin-film vacuum deaerator) as disclosed in Japanese Patent Application Laid-Open No. Hei 7-136406 for the pressure reduction step (2). That is, a continuous deaeration device of a type in which the target liquid is accelerated by the centrifugal force of a bottomed sieve body rotating in the vacuum vessel and the target liquid collides with a wall surface in the vacuum vessel to remove gas in the target liquid. By employing the method of (1), it is possible to greatly increase the effect of decarboxylation and dehydrogen sulfide by reduced pressure treatment. In addition, the decompression process is performed by MA
It may be before or after the P treatment step. Further, as shown in FIG. 1, the anaerobic fermentation step, the MAP treatment step, and the reduced pressure treatment step may be repeatedly performed. That is, the circulation between the anaerobic fermentation step, the MAP treatment step, and the reduced pressure treatment step can be reciprocated, respectively. FIG. 2 shows an example in which the sludge treatment system of FIG. 1 is applied to a wastewater treatment system, and the same operation and effect as those of the sludge treatment system were obtained. In FIG. 2, after treating the wastewater or biologically treated water 12 in the reduced pressure treatment tank 2,
P processing is performed. At this time, it may be circulated from the MAP reaction tank 23 to the reduced pressure processing tank 2. The water treated in the MAP reaction tank 23 is discharged as MAP treated water 14 and the product is discharged as MAP product 15.

[0015]

Next, an example of operation results of an experimental plant in which the present invention is actually incorporated will be described in detail. FIG. 1 shows the flow of the experimental plant. Example 1 That is, in the present invention, in an organic wastewater treatment system including an inflow SS solid-liquid separation tank 1, a biological reaction tank 3 in which activated sludge floats, and a microorganism solid-liquid separation tank 5, in the inflow SS solid-liquid separation tank 1, The concentrated sludge 11 of the separated primary settled sludge, that is, the SS component having relatively good dehydration property, high calorie, and low nitrogen and phosphorus content, is subjected to dehydration treatment by the dehydration device 10 so that a large amount of wastewater is discharged from the wastewater treatment system. The organic component is removed, and the dehydrated cake is burned in the cake burning device 7.
In addition, surplus sludge separated in the microbial solid-liquid separation tank 5 or its concentrated sludge 31, that is, relatively poor dehydration,
A low-calorie, high nitrogen and phosphorus content component is digested in the anaerobic fermenter 4 and digested sludge 41 produced in the anaerobic fermentation process, that is, from components containing high concentrations of nitrogen, phosphorus and alkali components Phosphorus and nitrogen are recovered in the form of magnesium ammonium phosphate.

At this time, before the step of flowing the organic wastewater into the biological reaction tank 3 in which the activated sludge floats, an intermediate solid-liquid separation for separating suspended components remaining in the separated water of the inflow SS solid-liquid separation tank 1 is performed. The tank 6 is provided, and the intermediate sludge or the concentrated sludge 61 separated in the intermediate solid-liquid separation tank 6 is supplied to the dewatering device 10.
The dewatering process includes a step of dehydrating the SS organic matter having a high calorie and a good dehydration property, and discharging the dehydrated cake to separate it from the water treatment system.

Further, a cake burning device 7 for burning the dewatered cake of the primary sludge or the concentrated sludge 11 dehydrated by the dewatering device 10 or the intermediate sludge or the concentrated sludge 61 thereof, and recovering energy generated in the cake burning device 7. Burning energy recovery means 8, anaerobic fermenter 4
By using means such as the methane gas recovery means 9 for recovering the methane gas and the like generated in the above, the energy consumption of the plant can be efficiently reduced.

Further, after the MAP first tank 21, a part of the sludge generated in the biological reaction tank 3 is transferred to the anaerobic fermentation tank 4.
In the digested sludge 41 during or after the anaerobic fermentation process, the thin film vacuum deaerator is used as the depressurizer 2 to increase the number of hydroxide ions due to decarboxylation or dehydrogen sulfide, thereby producing MAP. Promote the progress of The sludge after the MAP particle recovery was returned to the anaerobic fermenter. In the first MAP tank, a mechanism for taking out the MAP particles grown to 0.5 mm or more out of the system using the specific gravity ratio was incorporated. The digested sludge discharged from the anaerobic fermenter 4 is dewatered by the dewatering device 10, and the dewatered cake is burned by the cake burning device 7,
The dehydrated filtrate recovered nitrogen and phosphorus again by the MAP second tank. The target water used was sewage flowing into a sewage treatment plant.

In the embodiment shown in FIG.
0mg / liter, SS180mg / liter, inflow of 900m ³ / day, treated water quality is BOD
It was 20 mg / liter and SS 10 mg / liter. The mixture of the concentrated sludge 11 from the inflow SS solid-liquid separation tank 1 and the concentrated sludge 61 from the intermediate separation tank 6 is S
S: 30 g / liter, flow rate: 3.5 m ³ / day.
The sludge cake dewatered by the dewatering device 10 has a water content of 68
%, 240 kg / day. At this time, the MAP obtained in the MAP reactor 21 was 14 kg / day (MgNH ₄ P
O ₄ · 6H was ₂ as O). The amount of NaOH which is a pH adjuster added to the MAP first tank 21 is 0.2 kg /
3.0k for only MAP processing without decompression
g / day was reduced by about 93% or more. The amount of NaOH which is a pH adjuster added to the MAP second tank is 1.1 kg.
/ Day. The digestibility of organic matter in the anaerobic fermenter is 85% in the present invention, compared to 45% in the case of MAP treatment alone, and the recovery rate of MAP from nitrogen and phosphorus in digested sludge is MAP treatment. Only 4 each
% And 32% in the present invention, respectively.
And the recovery rate of the present invention was high.

Example 2 As shown in FIG. 2, the process water for the MAP reaction tank in the organic wastewater treatment system incorporating the MAP treatment is subjected to a decompression treatment in a decompression treatment tank. The MAP generation efficiency increases. Table 1 shows the ratio of the quality of the treated water to the amount of MAP generated when the MAP treatment is performed on the inflow water flowing into the MAP reaction tank in the wastewater treatment system for the wastewater of the A factory. As shown in the table, in the existing MAP treatment facility, although the Mg additive and the alkaline agent were sufficiently added, the phosphorus and nitrogen to be treated were 9.8 mg / liter and 41 mg, respectively.
In contrast to processing up to 0 mg / liter, the reduced pressure treatment step of the flow of the present invention is performed before the MAP treatment step, thereby reducing the amount of Mg additive and alkali agent compared to existing equipment. Nevertheless, the amounts of phosphorus and nitrogen in the treated water were reduced to 2.1 mg / liter and 330 mg / liter, respectively, enabling chemical saving and highly efficient removal. Regarding the point where the concentration of NH ₃ —N differs from the stoichiometric mass balance, there is a possibility that ammonia stripping may occur due to the combined use of the reduced pressure treatment and the alkali treatment, but it is clearly known at this time. Absent.

[0021]

[Table 1]

[0022]

According to the present invention, in an organic wastewater treatment system, in particular, wastewater containing organic matter, nitrogen, and phosphorus, for example, digestion and desorbent of human waste and septic tank sludge, digestion of sludge, and chemical factory wastewater In the MAP treatment method for removing magnesium ammonium phosphate crystals from wastewater containing high concentrations of organic substances such as phosphorus and nitrogen, etc., the amount of chemicals used is reduced and the efficiency of nitrogen and phosphorus removal is greatly improved. We were able to.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a method for treating organic wastewater of the present invention.

FIG. 2 is a block diagram of a processing method of performing depressurization processing in a decompression processing tank on process water for a MAP reaction tank in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inflow SS solid-liquid separation tank 2 Decompression device 3 Biological reaction tank 4 Anaerobic fermentation tank 5 Microorganism solid-liquid separation tank 6 Intermediate separation tank 7 Cake combustion device 8 Energy recovery means 9 Methane gas recovery means 10 Dehydration device 11 Condensed sludge 12 Drainage 13 Reduced pressure treatment water 14 MAP treatment water 15 MAP product 21 MAP first tank 22 MAP second tank 23 MAP reaction tank 31 concentrated sludge 41, 42, 43 digested sludge 61 concentrated sludge

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C02F 1/58 C02F 1/58 P 3/28 3/28 Z 11/00 11/00 J (72) Inventor Iruchijima Yoshiharu 11-1 Haneda Asahimachi, Ota-ku, Tokyo F-term in EBARA CORPORATION (Reference) 4D011 AA16 AB02 AD03 AD06 4D037 AA11 AB01 AB02 AB12 AB15 BA23 BB01 BB07 CA02 CA07 CA08 CA14 4D038 AA08 AB29 AB44 AB48 BA04 BB03 ABB19 4040 AA12 AA27 AA61 BB14 BB33 BB52 BB73 BB91 4D059 AA05 AA19 BA12 BE00 BE42 BK15 CA06 CA07 CC01 CC10 DA09

Claims (5)

[Claims] 1. A method for treating an organic wastewater, which comprises a step (1) of taking out phosphorus and nitrogen in the wastewater in the form of magnesium ammonium phosphate and taking them out of the system. A method for treating organic wastewater, comprising, before (1), a step (2) of reducing the pressure of the wastewater containing phosphorus and nitrogen. 2. An organic wastewater is treated in a biological reaction tank, sludge generated in the biological reaction tank is introduced into an anaerobic fermentation step, and phosphorus in digested sludge generated during or after the anaerobic fermentation step is removed. In a treatment method incorporating step (1) of removing nitrogen out of the system in the form of magnesium ammonium phosphate, the digested sludge containing phosphorus and nitrogen is subjected to reduced pressure treatment before or after the step (1). A method for treating organic wastewater, comprising the step of reducing pressure (2). 3. A wastewater treatment apparatus for biologically treating organic wastewater, wherein a magnesium ammonium phosphate reaction tank passing through a reduced pressure treatment device is provided in a treatment path for the organic wastewater or the treated water. Organic wastewater treatment equipment. 4. A wastewater treatment device for biologically treating organic wastewater, wherein a treatment path for sludge from a biological reaction tank for biologically treating organic wastewater is provided with magnesium phosphate passing through a reduced-pressure treatment device. An organic wastewater treatment apparatus, comprising: an ammonium reaction tank; or a decompression device passing through a magnesium ammonium phosphate reaction tank. 5. A wastewater treatment apparatus for biologically treating an organic wastewater, wherein the wastewater treatment apparatus is connected to a treated water inflow pipe for supplying the organic wastewater as inflow water, and is provided with a concentrated sludge delivery pipe to the dewatering apparatus. A liquid separation tank, an intermediate separation tank provided with a concentrated sludge delivery pipe to a dehydration device on the separated water discharge side, a biological reaction tank, and a final solid-liquid separation tank further provided with a concentrated sludge delivery pipe to an anaerobic fermentation tank And a cake combustion device provided with an energy recovery means for the anaerobic fermenter on the cake discharge side of the dehydrator, and phosphoric acid acting reversibly on the discharge side of the anaerobic fermenter provided with a methane gas recovery device. A magnesium ammonium reaction tank, a vacuum processing apparatus further provided with a vacuum processing apparatus, or a vacuum processing apparatus which acts reversibly on the discharge side of an anaerobic fermentation tank provided with a methane gas recovery apparatus; An organic wastewater treatment device, comprising an organic reaction tank.