JP6731025B2 - Method and apparatus for treating organic wastewater or sludge - Google Patents

Description

The present invention relates to a method and an apparatus for treating organic wastewater or sludge, and particularly, in an organic matter treatment system including a facility for anaerobically treating organic matter in organic wastewater or sludge by the action of anaerobic microorganisms, The present invention relates to a method and an apparatus for treating organic wastewater or sludge capable of recovering a component as a phosphorus compound such as magnesium ammonium phosphate (hereinafter referred to as “MAP”).

As a method for separating nitrogen components and phosphorus components from organic wastewater or sludge, magnesium ions or the like are added to the organic wastewater or sludge, and phosphorus, ammonia and magnesium ions contained in the wastewater are reacted to form MAP crystals. A method of growing and separating and collecting as MAP particles (referred to as “MAP processing method”) is known.

Such a MAP treatment method is an inexpensive crystallization method in which the amount of chemicals used, mechanical power, and thermal energy are relatively small, and the phosphorus component can be stably recovered, and the recovered MAP is excellent. Since it has added value as a fertilizer, it is an excellent technology for recovering and removing phosphorus and nitrogen from the viewpoint of effective use of resources.

Regarding the MAP treatment method, for example, in Patent Document 1, MAP particles generated in sludge in the anaerobic digestion step of anaerobically treating organic wastewater are separated by a liquid cyclone or the like to obtain a MAP separation concentrate containing the MAP particles. Then, magnesium ions are newly added to the MAP separation concentrate, and new MAP is laminated on the surface of the MAP particles present in the MAP concentrate by reaction with the dissolved phosphorus component to obtain MAP particles. A method has been proposed in which the MAP desorbed sludge that is recovered and the MAP particles are recovered is dehydrated and discharged as a dehydrated cake.

Further, in Patent Document 2, in an anaerobic digestion step of anaerobically treating organic wastewater or sludge, a step of solid-liquid separation of the organic sludge into a concentrated sludge and a concentrated desorption liquid before the anaerobic treatment, the concentrated sludge Anaerobic treatment, a step of separating MAP particles from the anaerobic-treated sludge, and a step of concentrating and dehydrating the anaerobic-treated sludge, respectively, wherein the anaerobic-treatment pre-stage concentrated desorbed water, A method has been proposed in which the MAP particles separated from the anaerobic-treated sludge, the anaerobic-treated concentrated/dehydrated separated water, and a magnesium source are mixed to produce MAP, and the MAP is separated and recovered.

Further, in Patent Document 3, the organic sludge is subjected to solid-liquid separation to separate it into a concentrated sludge of 4-12 wt% and a concentrated separated liquid, anaerobically digesting the concentrated sludge, and the anaerobic digested sludge and the previously concentrated separated water. A method of performing dehydration treatment after mixing the above is proposed.

JP, 2004-160304, A JP, 2004-941, A JP, 2016-117066, A

However, in all of Patent Documents 1 to 3, there is still room for studying a process for efficiently performing both the anaerobic treatment of an organic substance to be recovered and phosphorus recovery.

The inventors of the present invention have conducted research to recover soluble phosphorus components in organic matter as MAP particles for various organic wastewaters or sludges, and found that anaerobic treatment and phosphorus recovery of organic matter to be recovered The following items (1) to (5) were found as knowledge that serves as basic information for designing a process that is efficiently performed. All of these findings have been confirmed quantitatively by various pilot tests.

(1) The form of phosphorus in anaerobic digested sludge generated in a sewage treatment plant, etc. varies depending on the type and addition rate of the inorganic coagulant used for fixing phosphorus in the water treatment system. Since about 50 to 80% exist in the form of PO ₄ -P or MAP, by recovering these phosphorus from the sludge, the phosphorus in the sludge may be reduced and the solid sludge discharge amount may be reduced by 10% or more. To be.

(2) If the concentration of organic substances input to anaerobic treatment such as methane fermentation is increased to some extent, the capacity of the methane fermentation tank will be smaller and the retention days will be relatively short, about 10-15 days. The amount of surplus methane gas that can be used for is relatively large per input organic matter VS, and the methane fermentation efficiency is good.

(3) Even in a high-concentration organic sludge having a solid concentration of TS: 10 to 50 g/L, 80% or more of the anaerobic treatment input soluble phosphorus component is contained in an environment where a certain amount or more of seed crystal MAP particles are present. It can be formed as a relatively large MAP particle having a particle diameter of 10 μm or more.

(4) MAP particles having a MAP particle size of 10 μm or more can be separated and recovered at a recovery rate of 90% or more from sludge having a sludge concentration of 10 g/L or more by using a liquid cyclone or the like.

(5) The liquid mixture of the concentrated and separated water of the high-concentration digested sludge and the sludge before being put into the digestion tank has relatively good dewatering property.

Based on the above findings, while searching for a process that makes anaerobic treatment and phosphorus recovery more efficient, the present inventors have made further studies and found a problem. When performing a high-concentration digestion treatment, a concentration treatment is performed as a pretreatment of an organic substance to be fed into the anaerobic digestion process, but soluble phosphorus and soluble Mg may be relatively large in the separated concentrated separated water. Therefore, only by recovering phosphorus from the anaerobic digested sludge, it is possible to recover the soluble components in the pre-anaerobic-treated separated water, and to efficiently crystallize them into MAP particles having a relatively large particle size and recover them. Can be difficult.

As a phosphorus recovery method in a water treatment process before or without anaerobic digestion treatment of sludge, separated water containing a large amount of phosphoric acid is produced by utilizing the anaerobic aerobic method, and calcium salt is added by adding Ca salt: Known methods include a method of recovering Ca ₃ (PO ₄ ) ₂ and a method of adsorbing phosphoric acid with an adsorbent and finally recovering it as calcium phosphate through a phosphorus desorption process.

However, there is almost no report on the phosphorus recovery method from the mixed liquid of the liquid before the anaerobic digestion treatment and the sludge after the anaerobic digestion treatment. The reason is that under conditions without anaerobic digestion, it is common to separate and collect Ca-based precipitates such as calcium phosphate, which are highly reactive and have a specific gravity of 3.14 g/cm ^{3, which} is relatively easy to precipitate and separate. However, since there are many carbonate ions in the digested sludge after anaerobic digestion, if Ca is added, calcium carbonate tends to be produced earlier than calcium phosphate, resulting in poor efficiency.

When performing anaerobic digestion treatment, the soluble phosphorus and soluble Mg in the sludge that is put into the anaerobic digestion tank is contacted with about 1000 mg/L of NH ₄ -N immediately after being put into the digestion tank. Furthermore, since the pH also sharply rises to the alkaline range, fine MAP particles are instantly generated. Although it is obvious that the reactivity of the MAP formation reaction in the digestion tank is determined by the solubility product of each substrate component, the rate of change of the MAP solubility product in sludge under the flow conditions in the tank immediately after being introduced into the digestion tank Regarding the amount of newly formed fine MAP crystal nuclei and the amount of crystallization adhering to existing seed MAP particles, there are still many unclear points at the present time. There have been few reports on how much particle size MAP particles will be formed in a tank.

The reason for this is that there are still few efforts to recover MAP particles directly from sludge, and the particle size distribution of MAP particles produced in the digestion tank is MAP separation properties such as a liquid cyclone that separates and collects MAP in the latter stage. It has not been widely recognized that it will become an important factor that influences the above, and there are very few reports on the type, shape and physical properties of the inorganic fine particles present in the organic sludge in the first place.

In this regard, for example, the method of Patent Document 1 does not describe or suggest a method for directly recovering MAP particles from sludge before anaerobic treatment. On the other hand, in the method of Patent Document 2, it is described that the concentrated separated water obtained by concentrating and separating the sludge before the anaerobic treatment is supplied to the MAP granulation reaction device, but in the invention described in Patent Document 2, However, there is no description or suggestion of a method for directly recovering MAP particles from sludge before anaerobic treatment.

Further, in Patent Document 2, the liquid to be crystallized to be supplied to the MAP granulation reactor is mainly a filtrate after solid-liquid separation containing almost no organic sludge solids, and the crystallized water is treated in a water treatment system. It is clear from the description of Fig. 3 that is returned to the first settling tank that the crystallization-treated water has low turbidity, and the sludge before anaerobic digestion treatment is positively applied to the MAP granulation reactor. There is no description of supplying to.

Further, in Patent Document 2, as a method for recovering MAP from phosphate ions remaining in the digested sludge, a method of supplying the dehydrated filtrate after the dehydration treatment of the digested sludge to the MAP reaction tank is adopted, but in this method, dehydration is performed. Since the sludge is diluted by the coagulant used in the treatment and the wastewater from the dehydrator washing, the phosphate ion concentration and the Mg ion concentration in the filtrate at the time of being supplied to the MAP reaction tank are diluted to about 2/3. Since the MAP reaction is a chemical reaction due to the solubility product in many cases, the phosphorus recovery rate may be significantly reduced as compared with the method of directly supplying the digested sludge to the MAP reaction tank to recover phosphorus.

Further, the method of Patent Document 3 only discloses an example of highly efficient high-concentration anaerobic digestion using sludge having a sludge concentration of 4 to 12 wt %, and improves the anaerobic treatment of organic substances and the phosphorus recovery rate. There is no description or suggestion of a more efficient method.

In view of the above problems, the present invention provides a method and an apparatus for treating organic wastewater or sludge capable of efficiently performing both anaerobic treatment of an organic substance to be recovered and phosphorus recovery.

In order to solve the above-mentioned problems, the inventors of the present invention are concerned with factors affecting the particle size of MAP particles produced in an anaerobic treatment step, such as substrate concentration, VS concentration, various coexisting ions, temperature, pH, ORP, viscosity, and seed crystals. As a result of diligent research through various experiments on surface area, flow conditions, substrate supply method, organic matter decomposition rate, etc., the total amount of "phosphate ions" and "Mg ions" in sludge just before being supplied to the anaerobic treatment process It was found that it affects the size of the MAP particles produced.

In other words, the phosphate ion and Mg ion in the supplied sludge are respectively larger than the steady-state phosphate ion concentration and Mg ion concentration in the anaerobic treatment step, and the larger the difference, the easier the formation of fine MAP. Since this difference is a comparison based on the concentrations of phosphoric acid and Mg in the anaerobic treatment step during steady state, it is not necessarily determined only by the values of phosphate ion concentration and Mg ion concentration in the input sludge. There is nothing. The present inventors have developed this ΔPO ₄ -P (input sludge phosphoric acid-anaerobic treatment step phosphoric acid), ΔS-Mg (input sludge Mg ion-anaerobic treatment step Mg ion), and [ΔPO ₄ -P/input sludge. It has been found that a more optimal treatment process can be selected and a target phosphorus recovery rate can be achieved by using T-P], [ΔS-Mg/input sludge T-Mg] and the like as indexes.

Here, assuming that the PO ₄ -P concentration and the S-Mg concentration of the sludge put into the digestion tank are [PO ₄ -P-in] and [S-Mg-in] respectively, the The PO ₄ -P concentration and the S-Mg concentration are respectively [PO ₄ -P-out] and [S-Mg-out], and the TP concentration and the T-Mg concentration of the input sludge are respectively [TP -In], [T-Mg-in], the numerical values shown in the following equations (1) and (2) are L value (P) and L value (Mg), respectively. There is a correlation as shown in FIGS. 1 and 2 regarding the MAP rate (=fine MAP-P/TP).
L value _{(P) = ([PO 4} -P-in] - [PO 4 -P-out]) / [T-P-in] ... (1)
L value (Mg)=([S-Mg-in]-[S-Mg-out])/[T-Mg-in] (2)

More specifically, as a method for efficiently anaerobic treatment and phosphorus recovery of organic wastewater or sludge, the sludge to be supplied to the anaerobic treatment step before being supplied to the anaerobic treatment step is treated as The anaerobic treatment is performed in a state in which a predetermined treatment for significantly reducing the amounts of soluble phosphorus and soluble Mg is performed and the supply amount of the soluble phosphorus and soluble Mg to the anaerobic treatment step is significantly reduced. I do. Then, both the anaerobic treated sludge and the liquid containing soluble phosphorus and soluble Mg that were not directly supplied to the anaerobic treatment step are supplied to the MAP crystallization reactor, and the MAP separation device such as a liquid cyclone is used to form the MAP crystal. The organic wastewater is formed by forming a circulation line between the MAP separation device and the MAP crystallization reactor so as to maintain the MAP concentration in the precipitation reactor at a predetermined concentration, and supplying a Mg source into the reactor as necessary. It has also been found that a method of reducing soluble phosphorus contained in sludge and maximizing the amount of MAP recovered is one of the preferable methods.

The method for treating organic wastewater or sludge according to the embodiment of the present invention completed on the basis of the above findings, in one aspect, a step of performing an anaerobic treatment on the organic wastewater or sludge, the organic wastewater or A method for treating organic wastewater or sludge, comprising the step of recovering the phosphorus component in sludge in the form of magnesium ammonium phosphate particles, which is anaerobic after anaerobic treatment without concentrating and separating the organic wastewater or sludge. The treatment liquid and the organic wastewater or sludge in the previous stage of anaerobic treatment are mixed in a liquid in which magnesium ammonium phosphate particles are present without being concentrated and separated, and magnesium ammonium phosphate particles are adjusted by adjusting the pH of the mixed liquid. and Rukoto cause crystallization, the by the magnesium ammonium phosphate particles back to step to crystallize the MAP concentrate after separation concentration and, the MAP elimination sludge after separating concentrated magnesium ammonium phosphate particles at least a It is a method for treating organic wastewater or sludge, which is characterized in that the part is recycled to anaerobic treatment .

In another embodiment of the method for treating organic wastewater or sludge according to the embodiment of the present invention, the anaerobic treated liquid after anaerobic treatment is separated into a MAP concentrate and a MAP desorbed sludge, and a MAP concentrate is obtained. Is introduced into the MAP crystallization reactor, and the MAP desorption sludge is discharged to the outside of the treatment system of the MAP crystallization reactor.

In another embodiment of the method for treating organic wastewater or sludge according to the embodiment of the present invention, an anaerobic treatment liquid after anaerobic treatment of the organic wastewater or sludge, and an organic substance before the anaerobic treatment Physical decarboxylation is carried out in the MAP crystallization reactor in which the soluble phosphorus or soluble magnesium contained in the wastewater or sludge is introduced, or in the preceding stage of the MAP crystallization reactor.

In another embodiment of the method for treating organic wastewater or sludge according to the embodiment of the present invention, the soluble phosphorus or soluble magnesium contained in the organic wastewater or sludge in the preceding stage of anaerobic treatment is treated with a particle diameter of 10 μm. The above magnesium ammonium phosphate particles are mixed in a liquid containing 5 g/L or more.

In another embodiment of the method for treating organic wastewater or sludge according to the embodiment of the present invention, the pH is adjusted so that the pH of the mixed liquid is 6.8 or higher.

Preceding the present invention in yet another aspect, the anaerobic treatment apparatus, and the anaerobic treatment liquid after the anaerobic treatment without concentration separating the organic wastewater or sludge in the anaerobic treatment apparatus, the anaerobic treatment is performed And a MAP crystallization reactor for co-introducing the organic wastewater or sludge without being concentrated and separated, and adjusting the pH of the mixed solution in the liquid in which the magnesium ammonium phosphate particles are present to crystallize the magnesium ammonium phosphate particles. , MAP separation device for separating and concentrating magnesium ammonium phosphate particles from MAP crystallization treated water obtained in MAP crystallization reactor to obtain MAP concentrated liquid and MAP desorption sludge, and MAP desorption sludge to anaerobic treatment device An apparatus for treating organic wastewater or sludge, which is provided with a piping line for returning.

According to the present invention, it is possible to provide a method and an apparatus for treating organic wastewater or sludge, which are capable of efficiently performing both anaerobic treatment of an organic substance to be recovered and phosphorus recovery.

It is a graph showing the relationship between the L value of PO ₄ -P in the organic matter fed to the anaerobic treatment apparatus and the generation rate of fine MAP (%). It is a graph showing the relationship between the L value of S-Mg in the organic matter input to the anaerobic treatment apparatus and the generation rate of fine MAP (%). FIG. 1 is a schematic diagram showing a treatment device and treatment method for organic wastewater or sludge according to the first embodiment of the present invention. It is the schematic showing the processing apparatus and processing method of the organic wastewater or sludge which concern on the 2nd Embodiment of this invention. It is the schematic showing the processing apparatus and processing of the organic wastewater or sludge which concern on the modification of the 1st Embodiment of this invention. It is a schematic diagram showing a conventional organic wastewater or sludge treatment device and treatment method. FIG. 7 is a schematic diagram illustrating an example of a case where a conventional phosphorus recovery device is combined with the processing device and the processing method of FIG. 6.

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention specifies the structures, arrangements, etc. of constituent parts as follows. Not something to do.

In the present specification, a general sewage treatment plant that employs standard activated sludge treatment as a water treatment system and anaerobic digestion treatment and dehydration treatment as sludge treatment systems will be described as an example. However, those skilled in the art can adapt or apply to any treatment process such as food wastewater treatment, human waste wastewater treatment, food waste and organic waste material wastewater treatment that incorporates anaerobic treatment as a facility for treating organic waste liquid or organic matter. However, it is needless to say that the present invention is not limited to the exemplified sewage treatment.

Further, in the present specification, "fine MAP" means fine MAP having a particle size of 10 μm or less, which is difficult to separate from sludge by a separation device such as a liquid cyclone, and "coarse MAP" means a liquid cyclone. Means MAP in the form of fine particles having a particle size of 10 μm or less, which can be separated from sludge by a separating device such as. "Total MAP" means a combination of the above-mentioned fine MAP and crude MAP, and "seed crystal MAP" has a grain size of coarse MAP and is previously prepared to accelerate the MAP crystallization reaction. It refers to MAP particles which are filled in a fixed amount in a tank and allowed to flow. When the seed crystal MAP is sufficiently present, the MAP reaction is crystallized in such a manner that the seed crystal MAP is coated on the surface of the seed crystal MAP, and thus the reacted PO ₄ -P and S-Mg components have a particle size of the coarse MAP. It becomes MAP and can be separated and collected by a separation device such as a liquid cyclone.

There are two types of organic components that flow into the sewage treatment plant: first sludge that contains a large amount of organic acids that have settled and separated in the first settling tank in the water treatment system, and excess sludge that contains a large amount of activated sludge microorganisms that has settled and separated in the final settling tank. It is taken into the sludge and sent to the sludge treatment system as mixed raw sludge in which these are mixed. This mixed raw sludge decomposes organic substances by anaerobic digestion treatment in a sludge treatment system, recovers combustible gas, reduces the amount by dehydration treatment, and in some cases, performs dehydration treatment after dehydration cake, or after further reduction by incineration treatment, or It is generally carried out in the form of incinerated ash. The separated water separated in these sludge reduction processes is generally returned to the first settling tank of the water treatment system as return water.

Among the dissolved components of the mixed raw sludge supplied to the anaerobic digestion process, phosphate ions and magnesium ions released by activated sludge microorganisms in a form of trading with organic acids derived from primary sludge, and primary sludge derived There are many magnesium ions. It is desirable to introduce organic acids into the anaerobic digestion process as much as possible and recover them as combustible gases such as methane, but when phosphate ions and magnesium ions are introduced into the anaerobic digestion process, carbonate ions (dissociation products of organic matter decomposition by dissociation Then, hydroxide ions) and ammonia ions easily crystallize as MAP, which becomes a scale risk factor in the digestion tank and the subsequent equipment.

The digestion sludge in the digestion tank of general sewage sludge has a weak alkaline pH of about 7.0-7.5, and NH ₄ -N is about 600-1200 mg/L and PO ₄ -P is about 50 in the sludge. In many cases, about -300 mg/L and Mg ion about 1.0-30 mg/L are present. Magnesium ammonium phosphate (MAP) molecules having the structural formula of MgNH ₄ ·PO ₄ OH·5H ₂ O are produced in the digestion tank, and in many cases, MAP production is suppressed by Mg rate control. The amount of MAP existing in the digested sludge is often about 200-450 mg/L in terms of MAP-P.

The MAP particles have a wide range of particle diameters from 0.1 μm or less to 1 mm or more, and are necessary for recovering the MAP particles (specific gravity: 1.7) directly from the digested sludge 11 using a liquid cyclone or the like. The MAP particle abundance ratio of the coarse MAP particle size is about 10 to 35%.

According to the research conducted by the present inventors, when a general mixed raw sludge is put into the balance of such MAP-dissolved components in the digester, PO ₄ -P and Mg ions in the mixed raw sludge are digested in the digester. It has been found that MAP production rapidly progresses in balance with the pH and NH ₄ -N in the interior, and a large amount of fine new MAP particles is produced in the mixed raw sludge charging part in the digestion tank. Factors that generate fine MAP particles include not only substrate components such as PO ₄ ³⁻ , Mg ⁺ , NH ⁴⁺ , and OH ⁻ , but also seed crystal MAP amount, seed crystal particle diameter, flow conditions, etc. In the environment of the digester, it has been found that it is difficult to suppress the generation of fine MAP in the digester caused by PO ₄ -P and Mg ions derived from the input sludge.

Even if the fine MAP produced in the environment of the existing digestion tank is directly introduced into the MAP crystallization reactor in the subsequent stage, it is difficult to enlarge the total amount of fine MAP particles to the crude MAP level in a short time, so that the final digestion is performed. In many cases, most of the fine MAP generated in the tank cannot be finally recovered. Therefore, the inventors of the present invention have a method of recovering "PO ₄ -P and Mg ions" in the digestion tank charging liquid, which has the highest contribution to the production of fine MAP in the digestion tank, as crude MAP before charging the digestion tank. The following findings were obtained during the empirical examination.

That is, there is a large difference between the respective concentrations of phosphate ions and Mg ions supplied to this digestion tank and the respective concentrations of phosphate ions and Mg ions at the time of steady state in the digestion tank, and those values are TP of the input sludge, It was found that the larger the ratio with respect to T-Mg, the smaller the particle size of MAP particles produced in the digestion tank, and finally the phosphorus recovery rate decreases.

As a specific aspect, the following two methods of the first embodiment (reference example) and the second embodiment can be used, and one of them can be selected according to various conditions such as sludge properties. It is effective to do.

(First embodiment: concentrated separated water-digested sludge mixed phosphorus recovery system)
The organic wastewater or sludge treatment apparatus according to the first embodiment is, as shown in FIG. 3, a water treatment system 2 including a first settling tank 21, an aeration tank 22, and a final settling tank 23 for processing inflow water 1. Of the first settling basin 21 and the excess sludge 7 obtained in the final settling basin 23 to form mixed raw sludge 8 and the sludge treatment system 3 for treating the mixed raw sludge 8 And equipment.

In the first settling basin 21, the inflow water 1 is separated into the first settled sludge 5 containing a large amount of organic acid and the outflow water 4. The effluent 4 is subjected to aerobic treatment together with the activated sludge microorganisms in the aeration tank 22 to obtain an activated sludge mixed solution 6 containing the activated sludge. The activated sludge mixed liquid is subjected to solid-liquid separation in the final settling tank 23 to obtain surplus sludge 7 and treated water.

The surplus sludge 7 containing a large amount of activated sludge microorganisms settled and separated in the final settling tank 23 and the initial sludge 5 are mixed in a mixing tank 31 to obtain a mixed raw sludge 8. The mixed raw sludge 8 obtained in the mixing tank 31 is supplied to a concentrating device 32, and a coagulant or the like is added in the concentrating device 32 to concentrate the sludge to a concentration suitable for anaerobic treatment by a digestion tank 33 in a subsequent stage. The treated sludge is separated into concentrated sludge 9 and concentrated separated water 10.

In the concentrator 32, the concentrated sludge is typically concentrated to a sludge (TS) concentration of 2 wt% or more, more typically 4 to 12 wt%, and even more typically 7 to 10 wt%. By concentrating the mixed raw sludge 8 with the concentrating device 32 to increase the concentration thereof, the volume of the sludge that is put into the digestion tank 33 in the subsequent stage can be reduced, so that the digestion tank 33 can be downsized. Part of the concentrated separated water 10 can be returned to the sedimentation tank 21 first. Another part of the concentrated separated water 10 is supplied to the MAP crystallization reactor 34 via a pipeline. Depending on the amounts of phosphoric acid, Mg, organic acids, etc. in the concentrated separated water 10, the whole amount may be returned to the precipitation tank 21 first, or the whole amount may be supplied to the MAP crystallization reactor 34.

The concentrated sludge 9 is put into the digestion tank 33, and the anaerobic treatment is performed on the concentrated sludge 9 in the digestion tank 33 to obtain an anaerobic digestion liquid (digestion sludge 11). In the present specification, "anaerobic treatment" means methane fermentation mainly by absolutely anaerobic microorganisms or a treatment mainly composed of methane fermentation. A part or all of the digested sludge 11 is extracted from the digestion tank 33 and introduced into the MAP crystallization reactor 34.

The MAP crystallization reactor 34 adjusts the pH of the mixed solution to 6.8 or more in a liquid containing at least 5 g/L of magnesium ammonium phosphate particles having a particle size of 10 μm or more, and adjusts the pH of the magnesium ammonium phosphate particles. Is a device for crystallizing.

Although not shown, the MAP crystallization reactor 34 includes a pH adjusting mechanism for adjusting the pH of the liquid to be crystallized, a particle concentration adjusting mechanism for adjusting the concentration of MAP particles in the reactor, and Mg as necessary. It has a Mg supply mechanism for supplying ions. The mixed liquid of the concentrated separated water 10 and the digested sludge 11 obtained in the concentrator 32 is introduced into the MAP crystallization reactor 34, and the crystallization reaction of MAP particles proceeds in the MAP crystallization reactor 34. The MAP crystallization treated water 12 that has been treated in the MAP crystallization reactor 34 is discharged to the outside of the MAP crystallization reactor 34 and introduced into the MAP separation device 35.

The MAP separation device 35 is a device for separating and recovering magnesium ammonium phosphate particles from the MAP crystallization-treated water 12 obtained in the MAP crystallization reactor 34, and for example, a liquid cyclone or the like is preferably used.

In the MAP separation device 35, a MAP concentrated liquid 14 in which the crude MAP particles are separated and concentrated and a MAP desorbed sludge 13 in which the crude MAP particles are removed are obtained. The MAP concentrate 14 obtained by separating and concentrating the crude MAP particles is subjected to MAP crystallization through a pipe line provided between the MAP crystallization reactor 34 and the MAP separator 35, which are one of the facilities of the sludge treatment system 3. While being circulated back into the reactor 34, a part of it is discharged outside the system as a recovery MAP, and is used for various purposes after cleaning and drying.

In this way, the crude MAP particles obtained by the MAP separation device 35 are returned through the pipeline to the separated concentrated MAP concentrated liquid 14 to stably maintain the MAP concentration in the MAP crystallization reactor 34 at a predetermined concentration. Therefore, the MAP crystallization reaction in the MAP crystallization reactor 34 can be stably advanced. The MAP desorbed sludge 13 obtained by the MAP separating device 35 is introduced into a dehydrating device 36, and is dehydrated in the dehydrating device 36 to obtain a dehydrated cake.

Using the treatment apparatus shown in FIG. 3 described above, the method for treating organic wastewater or sludge according to the first embodiment can be implemented. That is, the treatment method according to the first embodiment includes a step of performing anaerobic treatment on organic wastewater or sludge, and recovering phosphorus components in the organic wastewater or sludge in the form of magnesium ammonium phosphate particles. It is a processing method including steps.

This method is included in the anaerobic treated liquid (digested sludge 11) after anaerobically treating the mixed raw sludge 8 containing organic wastewater or sludge in the digestion tank 33, and the mixed raw sludge 8 in the preceding stage for anaerobic treatment. Soluble phosphorus or soluble magnesium is preferably mixed in a MAP crystallization reactor 34 containing a liquid containing 5 g/L or more of magnesium ammonium phosphate particles having a particle size of 10 μm or more, and the pH of the mixed solution is preferably adjusted. Is more preferably 6.8 or more, more preferably by adjusting the pH to 7.1 to 7.8 to crystallize the magnesium ammonium phosphate particles, and crystallize the magnesium ammonium phosphate particles crystallized by the MAP separation device 35. The process includes returning the MAP concentrate 14 separated and concentrated in (1) to the MAP crystallization reactor 34, and sending the MAP desorbed sludge 13 to the dehydrator 36. MAP is recovered from a part of the MAP concentrated liquid 14.

It is preferable that the organic wastewater or sludge in the first stage for performing the anaerobic treatment, that is, the mixed raw sludge 8 includes a step of performing solid-liquid separation in the concentrating device 32 to separate into concentrated sludge 9 and concentrated separated water 10. It is preferable that the concentrated sludge 9 is introduced into the anaerobic treatment step, and the concentrated separated water 10 and the digested sludge 11 which is the anaerobic treated liquid after the anaerobic treatment are both introduced into the MAP crystallization reactor 34. Thereby, since the amount of soluble phosphorus and soluble magnesium in the sludge supplied to the anaerobic treatment step can be reduced in advance before the sludge is supplied to the anaerobic treatment step, in the anaerobic treatment step It is possible to suppress the generation of fine MAP that is less likely to contribute to the subsequent crystallization reaction that is generated, and control the soluble phosphorus in the sludge to a form that is more easily recovered as recovered MAP.

As described above, according to the apparatus and method for treating organic wastewater or sludge according to the first embodiment, it is possible to treat the mixed raw sludge 8 that has a relatively small amount of soluble organic matter that is the target of the anaerobic treatment. Even if there is, since the mixed raw sludge 8 can be concentrated in the concentration device 32 to a sludge concentration suitable for anaerobic treatment in the digestion tank 33, more useful gas is efficiently generated in the small digestion tank 33. Can be made.

Further, the concentrated and separated water obtained by the concentrator 32 and the digested sludge 11 discharged from the digestion tank 33 are introduced into the MAP crystallization reactor 34, and the crystallization reaction is allowed to proceed, so that the conventional water treatment system 2 is obtained. The supplied soluble phosphorus and soluble magnesium can be used for the MAP crystallization reaction in the sludge treatment system, and the recovery rate of phosphorus recovered by the MAP separation device 35 can be further improved. ..

Furthermore, the MAP concentrated liquid 14 discharged from the MAP separation device 35 is circulated back to the MAP crystallization reactor 34 as necessary, so that the MAP concentration in the MAP crystallization reactor 34 is suitable for crystallization of crude MAP particles. Since it can be maintained at a predetermined concentration, and by further supplying a Mg source into the MAP crystallization reactor 34 as necessary, the crystallization reaction in the MAP crystallization reactor 34 can proceed more stably. The stable phosphorus recovery rate can be obtained. The supply amount of the Mg source is specifically in the range of 0.5 to 1.3 based on the “Mg/P ratio” as a molar ratio with PO ₄ -P supplied into the MAP crystallization reactor 34. It is desirable to supply the Mg source as described above from the viewpoints of preventing the generation of fine MAP, reducing the cost, and preventing scale in the subsequent stage.

Further, according to the first embodiment, the soluble phosphorus or soluble magnesium contained in the mixed raw sludge 8 is maximally utilized to crystallize more MAP particles in the MAP crystallization reactor 34. be able to. Therefore, most of the MAP particles that existed in the conventional method as shown in FIG. 6 and FIG. 7 are removed in the dehydrated cake of the present embodiment, and the discharge amount of solid matter as the dehydrated cake is small. can do. As a result, cake disposal costs can be significantly reduced.

In addition, since PO ₄ -P and Mg ions in the dehydrated separated water separated by the dehydration treatment are greatly reduced as compared with the conventional method, even if the dehydrated separated water is returned to the water treatment system 2 as return water, water treatment is performed. The phosphorus load increase rate in system 2 can be made smaller than that in the conventional method.

The apparatus and method for treating organic wastewater or sludge according to the first embodiment can be particularly suitably applied when the soluble organic matter in the mixed raw sludge 8 is relatively small. At that time, when the mixed raw sludge 8 is concentrated and separated, the organic sludge is concentrated as much as possible to the concentrated sludge 9, and the concentrations of the soluble phosphorus and the soluble magnesium are reduced as much as possible. It is also effective to properly adjust the stirring conditions and aeration conditions before and after mixing the.

Although not limited to the following, for example, when the daily supply amount of the digested sludge 11 introduced into the MAP crystallization reactor 34 is 1Q, the concentrated separated water 10 should be 0.5 to 2.0Q. In one embodiment, when the daily supply amount of the digested sludge 11 is 0.3Q, the concentrated separated water 10 is 0.7Q, so that more efficient treatment can be performed.

(Second embodiment: phosphorus recovery method before anaerobic treatment of mixed raw sludge)
In the organic wastewater or sludge treatment device according to the second embodiment, as shown in FIG. 4, the point of supplying the mixed raw sludge 8 to the MAP crystallization reactor 34 before supplying it to the digestion tank 33 is: It is different from the organic wastewater or sludge treatment device according to the first embodiment.

That is, the organic wastewater or sludge treatment device according to the second embodiment is a digestive sludge obtained in the digestion tank 33 that performs anaerobic treatment, the mixed raw sludge 8 in the previous stage that performs anaerobic treatment, and the digestion tank 33. MAP crystallization reactor 34 for introducing at least a part of 11 together to crystallize magnesium ammonium phosphate particles, and magnesium ammonium phosphate particles concentrated from MAP crystallization treated water 17 obtained in MAP crystallization reactor 34 The MAP separating device 35 to be separated, and the MAP concentrated liquid 14 after separating and concentrating the magnesium ammonium phosphate particles in the MAP separating device 35 is circulated to the MAP crystallization reactor 34 or partially discharged out of the system to be recovered, A pipe line for returning the MAP desorbed sludge 16 to the digestion tank 33 of the sludge treatment system 3 is provided.

Since the target components in the mixed raw sludge 8 to be recovered by the MAP crystallization reactor 34 are phosphate ions and Mg ions, it is desirable to target the total amount of the mixed raw sludge 8 as much as possible, and at least the mixed raw sludge 8 It is preferable to introduce 50% or more of the above into the MAP crystallization reactor 34. However, the mixed raw sludge 8 may contain a certain amount of solid matter having a relatively large particle size such as hair, toilet paper residue, plant seed residue such as sesame seeds, etc. It may also cause clogging. Therefore, a part of the sludge mainly composed of solids having a relatively large particle size may be directly charged into the digestion tank 33 by using a sedimentation separation device or a separation screen, or may be mixed with the MAP desorption sludge 16. The gas may be supplied to the digestion tank 33, which effectively improves the decomposition efficiency of organic substances and the generation efficiency of useful gas such as methane gas in the digestion tank 33.

The opening diameter or screen width when using a separation screen or the like is preferably about 0.25 mm to 5 mm. However, when using this precipitation separator or separation screen, it is better to use a physical separation method that does not use a coagulant, and the concentration method that uses a coagulant was adopted in the first embodiment described above. Compared to the case, it can be expected that the effect of reducing chemical costs will be relatively low.

The digested sludge 11 processed in the digestion tank 33 is supplied to a MAP separation device 37 such as a hydrocyclone to separate and concentrate MAP particles, and the MAP concentrated liquid 15 and the MAP desorbed sludge 13 are separated. The MAP concentrate 15 is introduced into the MAP crystallization reactor 34 together with the mixed raw sludge 8 from the mixing tank 31. The MAP desorbed sludge 13 is introduced into the dehydrating device 36 via a pipeline, and is dehydrated in the dehydrating device 36 to produce a dehydrated cake.

In the MAP crystallization reactor 34, the pH is adjusted so that the pH of the mixed solution is 6.8 or more in a liquid containing at least 5 g/L or more of magnesium ammonium phosphate particles having a particle size of 10 μm or more, and The crystallization reaction proceeds. The MAP crystallization-treated water 17 processed in the MAP crystallization reactor 34 is introduced into a MAP separation device 35 such as a liquid cyclone, and MAP particles are separated by the cyclone separation. The MAP concentrated liquid 14 obtained after collecting the MAP particles is circulated back to the MAP crystallization reactor 34, and a part thereof is collected.

The MAP desorbed sludge 16 is used as a sludge to be input to the digestion tank 33 via a piping line. Although not shown, a pipe line may be provided to supply a part of the MAP concentrate 14 as seed crystal MAP to the digestion tank 33 as needed.

The method for treating organic wastewater or sludge according to the second embodiment can be implemented using the treatment apparatus shown in FIG. That is, in the treatment method according to the second embodiment, the mixed raw sludge 8 and at least a part of the digested sludge 11 obtained from the digestion tank 33 are both introduced into the MAP crystallization reactor 34, and the MAP crystallization reactor is introduced. At least a part of the MAP concentrated liquid 14 or the MAP desorbed sludge 16 after separating and concentrating the MAP particles crystallized in 34 is recycled to the anaerobic treatment in the digestion tank 33.

In the method for treating organic wastewater or sludge according to the second embodiment, the digested sludge 11 is further separated into the MAP concentrate 15 and the MAP desorbed sludge 13 in the MAP separator 37, and the MAP concentrate 15 is separated from the MAP concentrate 15. It may be introduced into the crystallization reactor 34 and discharging the MAP desorbed sludge 13 to the dehydrator 36 which is outside the treatment system of the MAP crystallization reactor 34. When the amount of crude MAP existing in the digested sludge 11 is sufficiently small, for example, about 100 mg-P/L or less, and when there is a request from the treatment facility side, the MAP separation device 37 is omitted and the digested sludge 11 is omitted. It is also possible to substitute a predetermined amount of the above into the MAP crystallization reactor 34 and send another predetermined amount to the dehydrator 36.

In addition, when the PO ₄ -P existing in the digested sludge 11 is unnecessarily large, for example, about 50 mg-P/L or more, and when there is a request from the processing facility side, etc., it is different from the MAP crystallization reactor 34. It may be effective to provide another MAP crystallization reactor (not shown) to remove PO ₄ -P from the sludge sent to the dehydrator 36 and recover it as MAP.

To achieve both of the original purpose of anaerobic treatment, "maximizing the decomposition rate of organic matter and maximizing the amount of useful gas such as CH ₄ that is generated accompanying it, and recovering useful gas," and improving the efficiency of phosphorus recovery from organic matter. In particular, it is desirable to leave as much organic matter as possible in the substance introduced into the anaerobic treatment step and remove soluble phosphorus and soluble Mg.

According to the organic wastewater or sludge treatment apparatus and treatment method of the second embodiment, the mixed raw sludge 8 is directly supplied to the MAP crystallization reactor 34 before the anaerobic treatment, and the MAP crystallization reactor 34 is supplied. Soluble phosphorus and soluble magnesium in the mixed raw sludge 8 are crystallized into MAP particles and separated, and the MAP desorbed sludge 13 after separating the MAP particles is supplied to the digestion tank 33, thereby anaerobic The treatment can be performed more efficiently, and at the same time, the phosphorus recovery rate can be improved.

In order to allow the crystallization reaction to proceed more stably in the MAP crystallization reactor 34, the pH is preferably set to 6.8 or higher, and more preferably in the alkaline range of 7.1 to 7.8. On the other hand, since the mixed raw sludge 8 of general sewage has a weak acidity of about 4.5 to 6.5, the mixed raw sludge 8 is treated with a MAP crystallization reactor like the treatment device shown in FIG. By introducing into the MAP crystallization reactor 34, the amount of the pH adjusting agent to be added may increase.

In the treatment apparatus according to the second embodiment, in order to utilize at least a part of the digested sludge 11 as an alkaline agent, NH ₄ , PO ₄ -P, and MAP seed crystal supply agent, the mixed raw sludge 8 is mixed. By introducing the digested sludge 11 into the MAP crystallization reactor 34 at the same time as the supply and appropriately adjusting the supply amount of the digested sludge 11, the amount of the chemical to be supplied to the MAP crystallization reactor 34 can be reduced. The following is an example because it depends on the sludge property. For example, when the mixed raw sludge 8 is added at about 1Q per day, the MAP concentrate 15 is supplied at 0.5 to 3Q per day to concentrate the MAP. When the daily supply amount of the liquid 15 is set to 2Q, by adding the mixed raw sludge 8 in about 1Q, more MAP can be recovered while reducing the supply amount of the chemical supplied to the MAP crystallization reactor 34. You can

The ratio of the amounts of the mixed raw sludge 8 and the digested sludge 11 supplied to the MAP crystallization reactor 34 varies depending on the sludge properties, but the MAP crystallization environment in the MAP crystallization reactor 34 has a pH of 6.7 to 7.6. , Mg ion concentration: 0.1 to 60 mg/L, crude MAP particle concentration: 7 to 70 g/L, two types of sludge blend ratio of mixed raw sludge 8 and digested sludge 11, Mg-based chemical addition It is desirable to adjust the amount, the aeration amount in the reactor, the MAP extraction amount, and the like.

In some cases, the mixed raw sludge 8 and the digested sludge 11 to be introduced into the MAP crystallization reactor 34 may be partially mixed before being introduced into the MAP crystallization reactor 34. Part of the fine MAP in the digested sludge 11 can be dissolved by coming into contact with the weakly acidic mixed raw sludge first, which increases the PO ₄ -P and S-Mg load on the MAP crystallization reactor 34. Therefore, the phosphorus recovery rate can be improved.

When the digested sludge 11 is supplied to the MAP crystallization reactor 34, MAP is once collected from the digested sludge 11 by the MAP separation device 37 and separated into a MAP concentrate 15 and a MAP desorbed sludge 13, and a MAP concentrate 15 It is more efficient from the viewpoint of reducing the phosphorus recovery rate and the amount of dehydrated cake discharged that the MAP desorbed sludge 13 is discharged to the outside of the system for dehydration treatment by introducing this into the MAP crystallization reactor 34. preferable.

In the MAP desorbed sludge 16 introduced into the anaerobic treatment step via the MAP crystallization reactor 34, organic substances are decomposed by the anaerobic microorganisms in the digestion tank 33, and at the same time, PO ₄ -P, S- are decomposed metabolites. Mg and NH ₄ —N increase, and MAP particles are generated in the anaerobic treatment process. However, the concentration of these MAP substrate components in the anaerobic treatment step does not change abruptly, particularly in the sludge inflow part of PO ₄ -P and S-Mg. It has been found to proceed slowly at relatively low concentrations to form relatively large MAP particles. That is, since the production of fine MAP, which was generated in a large amount in the anaerobic treatment step in the conventional method, is suppressed in the present invention, the phosphorus recovery rate is dramatically improved.

(Modification)
The digested sludge 11 after anaerobic treatment of the mixed raw sludge 8 and the concentrated separated water 10 or the mixed raw sludge 8 in an unconcentrated state are mixed together before being supplied to the MAP crystallization reactor 34, and the digested sludge 11 is mixed. In some cases, it may be preferable to perform a physical decarbonation treatment on the concentrated separated water 10 or the mixed raw sludge 8 that is not concentrated. Therefore, as shown in FIG. 5, a physical decarboxylation treatment device 38 may be provided between the digestion tank 33 and the MAP crystallization reactor 34 or in the MAP crystallization reactor 34.

As the physical decarbonation device 38, an aeration device, a mechanical stirring device, or the like can be used. According to the treatment apparatus shown in FIG. 5, the physical decarbonation treatment apparatus 38 performs the physical decarbonation treatment on the digested sludge 11 and the concentrated separated water 10 or the mixed raw sludge 8 in the unconcentrated state. In addition, since the pH increases, the amount of the pH adjuster used can be reduced, and the scale risk can be reduced in the subsequent process after the MAP crystallization further progresses in the pH environment increased by decarboxylation. In addition, the recovery rate of MAP particles in the MAP crystallization reactor 34 can be increased, and the amount of dehydrated cake produced can be reduced.

Although illustration is omitted, the physical decarbonation device 38 is arranged in the latter stage of the MAP separation device 37 and in the former stage of the MAP crystallization reactor 34 in FIG. 4 to remove the MAP concentrate 15 and the mixed raw sludge 8. Of course, it is also possible to carry out carbonic acid treatment.

The organic sludge that is introduced into the anaerobic treatment process in a treatment facility such as a sewage treatment plant has greatly different sludge properties due to the difference in the operation method in the water treatment system 2, etc. The amounts of phosphorus and soluble Mg are various.

Although there are cases where it cannot be said unequivocally, for example, when the sludge introduced into the anaerobic digestion tank at a sewage treatment plant has a ratio of initial sludge to be greater than the ratio of activated sludge-derived excess sludge, the sludge has an organic acid content rate. When the ratio of activated sludge-derived excess sludge is relatively high, soluble phosphorus and soluble magnesium are relatively high. When the sludge is the former, it is not possible to recover CH ₄ gas from the organic acid of the concentrated separation water in a process in which the sludge that has been anaerobically treated is concentrated and separated and the concentrated separation water is not introduced into the anaerobic treatment. become. In the case of the latter sludge, even a process in which the anaerobic treatment input sludge is concentrated and separated and the concentrated separation water is not introduced into the anaerobic treatment has almost no effect as CH ₄ gas recovery, and conversely high-concentration methane fermentation becomes possible. The fermentation tank can be made compact, which is effective. As described above, it is preferable to select one of the methods of the first embodiment, the second embodiment, and the modified example depending on the sludge property introduced into the anaerobic process.

Hereinafter, examples of the present invention will be shown together with comparative examples, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the present invention.

Phosphorus was recovered using a pilot plant that can switch to multiple operating conditions, using the first settling sludge and surplus sludge generated in the water treatment system of the sewage treatment plant. All of the anaerobic digestion equipment for mixed raw sludge adopts medium temperature digestion at 35°C, the digestion tank has a hydraulic retention time of 25 days, and the MAP separation device uses a liquid cyclone for all the hydrocyclone according to each flow balance. The caliber of under and over was adjusted appropriately. If the liquid cyclone charging liquid contained impurities having a particle size of 10 mm or more, they were removed by a sieve, and the removed substances were mixed with the cyclone over liquid.

Example 1 (reference example) shows the case of operating based on the pilot plant having the configuration shown in FIG. 3, and only Example 1 employs a digestion tank having a capacity of 1/3 of that of other Comparative Examples 1 and the like. Then, the sludge to be put into the digestion tank was introduced into the digestion tank in a state where the concentration of sludge was tripled by adding 0.2% of a flocculant to solid matter to the mixed raw sludge. Example 2 shows the case of operating based on the pilot plant having the configuration shown in FIG. 4, and 13 MAP desorption sludge: 15 MAP concentrated liquid: 8 mixed raw sludge = 2:3:2 from various conditions as the flow rate balance. It was set to be. Example 3 shows a case where decarbonation treatment was performed by adding an air lift circulation type aerator to the MAP crystallization reactor provided in the pilot plant configured as shown in FIG.

Comparative Example 1 shows the case of operating based on the pilot plant having the structure shown in FIG. 7, and Comparative Example 2 changes the mixing ratio of the first set sludge of the mixed raw sludge and the excess sludge in the pilot plant having the structure shown in FIG. 7. The following shows the case of driving.

The details of the operating conditions are shown in Table 1, and the phosphorus recovery rate of Comparative Example 1, the cost of the used chemical agent per recovered phosphorus, the plant power, the plant installation area, the surplus methane gas recovery amount, and the discharged solid amount (dehydrated cake weight) are 100 and 100, respectively. Table 2 shows the comparison results of each example and each comparative example in the case of performing. The cost of the chemicals used per recovery of phosphorus was the cost including the Mg source for crystallizing MAP, the pH adjuster, and the coagulant used when concentrating the mixed raw sludge.

In all of Examples 1 to 3, the phosphorus recovery rate could be increased as compared with Comparative Example 1 in which the mixed raw sludge was subjected to anaerobic treatment and then dehydrated. In addition, in all of Examples 1 to 3, the cost of the chemical agent used per recovered phosphorus could be reduced as compared with Comparative Example 1. Further, regarding the amount of discharged solid matter, since the MAP particles contained in the discharged cake as a solid matter in Comparative Example 1 are separated and collected in Examples 1 to 3, it is possible to significantly reduce the amount of solid waste. It was effective.

Furthermore, in Example 1, since the anaerobic treatment was performed using the concentrated sludge obtained by concentrating the mixed raw sludge, the size of the digestion tank could be reduced, and the plant installation area could also be reduced. .. In particular, since the digestion tank becomes 1/3, the recovery CH ₄ of the boiler used for heating treatment of the digestion tank is greatly reduced, and the surplus CH ₄ that can be used for power generation is increased from 100 to 105. did. Regarding phosphorus recovery, as expected, the fine MAP ratio in the digestion tank was drastically decreased from 80% to 55%, and the crude MAP conversion ratio was correspondingly increased, so the phosphorus recovery ratio was increased. Although the cost of the flocculant used for concentrating the mixed raw sludge to be put into the digestion tank 3 times was more than that in Comparative Example 1, the amount of phosphorus recovered increased 1.3 times, and The chemical cost was less than that of Comparative Example 1.

In Comparative Example 2 and Examples 2 and 3, the ratio of the initial sludge to the excess sludge of the mixed raw sludge is 8:2, and the organic matter derived from the initial sludge is large, so the method of Example 1 is adopted. CH ₄ gas cannot be recovered from organic substances such as organic acids in the concentrated separation water separated in the concentration treatment of the mixed raw sludge. Therefore, we did not concentrate the mixed raw sludge and used a normal size digestion tank.However, since there are many organic substances derived from the first settled sludge that has not been subjected to microbial decomposition treatment such as activated sludge treatment, excess gas in the digestion tank is used. Recovery volume increased slightly. Further, although the reason is not clear, Comparative Examples 1 and 2 are not suitable as a plant in the MAP crystallization because phosphorus derived from excess sludge tends to be slightly coarser than the phosphorus derived from initial settled sludge. Although the same, the phosphorus recovery rate was slightly smaller in Comparative Example 2.

In Example 2, since the soluble phosphorus and the soluble Mg were drastically reduced from the mixed raw sludge to be introduced into the digester, the mixture was introduced before the fine MAP production rate in the digester was 80%→45. %, and the phosphorus recovery rate was significantly increased since the crude MAP could be recovered in the latter stage. As for the cost of chemicals used per recovered phosphorus, the cost of chemicals was significantly reduced compared to Example 1 because the coagulant for concentration treatment of the mixed raw sludge used in Example 1 was not used.

In Example 3, the amount of the pH adjuster used could be reduced by the decarboxylation effect by aeration, and both the phosphorus recovery rate and the chemical cost were improved compared to Example 2. Regarding the plant power and the plant installation area of Examples 2 and 3, although the number of devices increased slightly compared to Comparative Example 2, the differences were not large.

In Comparative Examples 1 and 2 in which the mixed raw sludge or the concentrated separated liquid was not supplied to the MAP crystallization reactor, the amount of the chemicals added in the MAP crystallization reactor increased, and it contributed to the generation of MAP particles recovered in the digestion tank. Since fine MAP particles that were not produced were generated in the digestion tank, the phosphorus recovery rate and the drug cost per recovered phosphorus were lower than in Examples 1-3.

1... Influent water 2... Water treatment system 3... Sludge treatment system 4... Outflow water 5... Initial sludge 6... Activated sludge mixture 7... Excess sludge 8... Mixed raw sludge 9... Concentrated sludge 10... Concentrated separated water 11... Digestion Sludge 12... MAP crystallization treated water 13... MAP desorption sludge 14... MAP concentrate 15... MAP concentrate 16... MAP desorption sludge 17... MAP crystallization treated water 21... First settling tank 22... Aeration tank 23... Final settling Pond 31... Mixing tank 32... Concentrator 33... Digestion tank 34... MAP crystallization reactor 35... MAP separation device 36... Dehydration device 37... MAP separation device 38... Physical decarboxylation treatment device

Claims (7)

A method for treating organic wastewater or sludge, comprising a step of anaerobically treating the organic wastewater or sludge, and a step of recovering the phosphorus component in the organic wastewater or sludge in the form of magnesium ammonium phosphate particles. hand,
An anaerobic treatment liquid after the anaerobic treatment without concentrating and separating the organic wastewater or sludge, and magnesium ammonium phosphate particles in a state where the organic wastewater or sludge in the preceding stage of the anaerobic treatment is not concentrated and separated. were mixed in a liquid that is present, the the Rukoto to crystallize the magnesium ammonium phosphate particles, the MAP concentrate after separating concentrating the magnesium ammonium phosphate particles crystallization by adjusting the pH of the mixed solution The method for treating organic wastewater or sludge, which comprises returning to the step of allowing the treatment, and circulating and returning at least a part of the MAP desorbed sludge after separating and concentrating the magnesium ammonium phosphate particles to the anaerobic treatment. Before the anaerobic treatment, 50% or more of the organic wastewater or sludge is introduced into a MAP crystallization reactor to crystallize the phosphorus component in the organic wastewater or sludge in the form of magnesium ammonium phosphate particles. The method for treating organic wastewater or sludge according to claim 1, further comprising a step of recovering the organic wastewater . Method of treating organic waste water or sludge according to claim 1 or 2, characterized in that the pre-Symbol MAP elimination sludge further comprising a be discharged to the processing system out of the MAP crystallization reactor. In a MAP crystallization reactor for introducing anaerobic treatment liquid after anaerobic treatment of the organic wastewater or sludge, and soluble phosphorus or soluble magnesium contained in the organic wastewater or sludge in the preceding stage of the anaerobic treatment Alternatively, the method for treating organic wastewater or sludge according to any one of claims 1 to 4 , wherein a physical decarboxylation treatment is performed in the preceding stage of the MAP crystallization reactor. The soluble phosphorus or soluble magnesium contained in the organic wastewater or sludge in the preceding stage of the anaerobic treatment is mixed in a liquid in which 5 g/L or more of magnesium ammonium phosphate particles having a particle diameter of 10 μm or more are mixed. The method for treating organic wastewater or sludge according to any one of claims 1 to 5 . Method of treating organic waste water or sludge according to any one of claims 1 to 5, the pH of the mixed solution and adjusting the pH such that 6.8 or more. And anaerobic processing apparatus,
In the anaerobic treatment apparatus, the anaerobic treatment liquid after anaerobic treatment without concentrating and separating the organic wastewater or sludge, and the organic wastewater or sludge in the previous stage of performing the anaerobic treatment is not concentrated and separated. A MAP crystallization reactor which is introduced together and crystallizes the magnesium ammonium phosphate particles by adjusting the pH of the mixed solution in a liquid in which the magnesium ammonium phosphate particles are present,
A MAP separating device for separating and concentrating the magnesium ammonium phosphate particles from the MAP crystallization treated water obtained in the MAP crystallization reactor to obtain a MAP concentrate and a MAP desorbed sludge;
A pipe line for returning the MAP desorbed sludge to the anaerobic treatment device, and a treatment device for organic wastewater or sludge.