JPS6391196A - Dephosphorization method for night soil treatment by using ultrafilter membrane - Google Patents

Abstract

PURPOSE:To permit effective removal of phosphorus by putting night soil into a dephosphorization plant, adding a flocculating agent thereto and removing the flocculated solid from the night soil in such a manner that the contained phosphorus components necessary for a biological reaction treatment remain in the separated liquid. CONSTITUTION:The night soil is treated in a biological reaction tank 20 and is then subjected to solid-liquid sepn. by an ultrafilter membrane 22. Sludge is returned to the vessel 20 and is partly treated as excess sludge. Before the night soil is supplied to the vessel 20, the night soil is fed to the dephosphorization plant 7 where the flocculating agent (e.g., cationic high- polymer flocculating agent and ferric polysulfate) is added to the night soil by a flocculating agent adder 9 to flocculate and solidify the phosphorus components contained in the night soil. The separated water is then fed to the tank 20. As a result, the phosphorus is effectively removed without increasing the load of suspended matter on the ultrafilter membrane.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dephosphorization method in human urine treatment using an ultrafiltration membrane. The present invention relates to a dephosphorization method in human waste treatment that can reduce the SS (suspended solids) load on membranes.

[Background of the Invention] In recent years, an innovative process that combines biological treatment and membrane treatment has been developed as an advanced treatment method for human waste.
No. 87725) has been certified as a ``human waste treatment facility outside the guidelines of the Ministry of Health and Welfare,'' and has achieved good results in the industry.

However, the ultrafiltration membrane used in the ASMEX process (
The OF film (hereinafter referred to as the OF film) is made of inorganic molecular substances (P, N
Unable to block Ox, Ml (4-N, etc.),
Nitrogen (N) and phosphorus (P), which are thought to be the cause of eutrophication,
) leakage becomes a problem. However, nearly 100% of the nitrogen content can be removed through biological treatment, so there are few problems with runoff. On the other hand, with regard to phosphorus, biological treatment has a limit of 50% removal, so there is a problem of leakage.

For this reason, the inventors investigated a method of treating the treated water after passing through the UF membrane using a general dephosphorization method. −・General dephosphorization methods include ■ coagulation sedimentation removal method, ■ apatite crystallization method,
■An adsorption removal method using a selective adsorbent can be considered.

The coagulation-sedimentation removal method (■) uses a flocculant to fix phosphorus as flocculated sludge, which is then dehydrated and incinerated. This is a method in which phosphorus is removed by crystallizing it as oxyapatite and passing it through a column packed with calcium carbonate such as bone char or persimmon shell.

However, these methods (1) and (2) cannot be said to be preferable methods because they cause SS to be contained in the treated water from which SS has been completely removed by the UF membrane. On the other hand, the adsorption removal method (2), which has fewer such drawbacks, is a method in which the phosphorus in the adsorbent is reacted with caustic soda and extracted as sodium phosphate, a caustic soda solution.The adsorbent is washed with acidic water to activate it and then recycled The sodium phosphate solution used and taken out is treated by the following two methods.

(a) One method is to add ferric chloride to sodium phosphate to form iron phosphate crystals, dehydrate and incinerate the crystals, and return the separated water to the main treatment process.

(b) Another method is to add caustic soda to a sodium phosphate solution, remove the liquid and separate the sodium phosphate crystals that precipitate due to the solubility difference, and extract them as sodium phosphate crystals, and the separated water is used as the regenerated adsorbent solution. This is a method of reusing it as

However, method (2) above has the drawbacks of high equipment costs and running costs (alkali consumption, etc.) and difficult process control.

Therefore, in order to solve the above-mentioned drawbacks, attempts have been made to dephosphorize the material before passing through the UF membrane.

For example, there are known techniques in which a flocculant for fixing phosphorus (P) is added to a biological reaction tank, or the flocculant is added intermediately from the biological reaction tank to the UF membrane (Japanese Patent Application Laid-open No. 58-128084).

However, in this technology, since the sludge concentration in the biological reaction tank is high, phosphorus (P) is immobilized and the phosphorus (P) is
In order to obtain the removal effect of phosphorus, a large amount of flocculant is required to be added, resulting in high costs.Also, it is not possible to achieve the desired phosphorus concentration (for example, the concentration regulated by law or ordinance). was there. Furthermore, the added flocculant increases the SS load on the membrane, which has the disadvantage of shortening the membrane life.

[Object of the Invention] An object of the present invention is to provide a dephosphorization method in human urine treatment using a UF membrane that can effectively remove phosphorus without increasing the SS load on the membrane.

[Means for Solving the Problems 1] As a result of extensive studies to achieve the above object, the inventors have completed the present invention.

In the dephosphorization method for human waste treatment using the UF membrane according to the present invention, human waste is treated in a biological reaction tank, then solid-liquid separation is performed by an OF membrane, and the sludge is returned to the biological reaction tank, while a part of it is treated as surplus sludge. In the human waste treatment method, the human waste is received in the dephosphorization equipment before being supplied to the biological reaction tank,
In the dephosphorization equipment, a flocculant is added to flocculate and solidify the phosphorus component contained in the human waste, and at least the phosphorus component necessary for biological reaction treatment remains in the separated liquid from which the flocculated solid is removed. It is characterized in that water is received into the biological reaction tank.

[Function] According to the present invention, when a flocculant is added in the dephosphorization equipment, the ss in the human waste is flocculated to form flocculated sludge, and the coagulated and solidified phosphorus contained components adhere to this flocculated sludge and are integrated. A flocculated sludge is obtained, and by removing this sludge, the phosphorus component is removed.

Furthermore, since the flocculation reaction can be controlled by the amount of flocculant added, it is also possible to limit the amount of phosphorus component removed so that at least the phosphorus component necessary for biological reaction treatment remains in the separated liquid from which flocculated solids have been removed. Become. Since the phosphorus component is controlled in this way, the amount of phosphorus component after membrane treatment is also extremely small, allowing it to be discharged.

Furthermore, by providing a dephosphorization treatment facility before the biological reaction treatment, organic substances and SS are also removed in addition to phosphorus, and the load on the biological reaction treatment is significantly reduced.

Furthermore, the addition of a flocculant does not increase the load on biological reaction treatment or membrane treatment.

[Example] An embodiment of the method of the present invention will be explained based on FIG.

Human waste is received in a receiving tank 1, and if the human waste contains relatively large impurities such as sand and stones, they are sedimented and removed in the receiving tank 1. The human waste in the receiving tank 1 is sent to a coarse screen 3 by a raw solution pump 2. The coarse screen 3 is a screen with an opening of 2 mm to 10 mm, and when the human waste passes through this screen, solid substances such as fibrous substances, rubber products, and other floating impurities in the human waste are removed.

The solid material is dewatered using a dehydrator 4, the cake is incinerated in an incinerator, and the separated water is sent to a primary storage tank 5. As the dehydrator 4, for example, a screw press can be used.

The human waste that has passed through the coarse screen 3 is sent to a secondary storage tank 5, and sent to a dephosphorization facility 7 together with the separated water by a pump 6.

The dephosphorization facility@7 consists of a coagulation tank 8, a flocculant addition device 9, and a solid-liquid separation device 10. The aggregation tank 8 is provided with an agitator 11, and it is preferable to use an agitator 11 whose rotation speed can be varied. The flocculant addition device 9 is a device for adding a polymer flocculant and polyferric sulfate, which are preferably used as flocculants.

12 is a polymer flocculant tank, and this tank 12 is provided with an agitator 13. If a powdered or liquid polymer flocculant is placed in the tank 12, diluted with water and stirred, a liquid flocculant adjusted to a predetermined concentration (approximately Q, 1 to 0.5%) can be obtained. can. 14 is a polymer flocculant pump.

The polymer flocculant that can be used in the present invention is not limited, but a cationic polymer flocculant is preferable, and specifically, for example, re-4804 manufactured by Mitsui Sui Anamido Co., Ltd.
etc. are preferred.

A ferric polysulfate tank 15 receives commercially available ferric polysulfate (11% liquid) and adds a predetermined amount of it diluted or undiluted using a pump 16. Inorganic flocculants that can be used in the present invention include ferric chloride and the like in addition to poly'8 and ferric acid.

In the present invention, the amount of polymer flocculant added is preferably 0.5 to 4.0%, more preferably 1.0 to 2.0%, based on the amount of dry SS flowing into the flocculation tank 8. In the case of polyferric sulfate, the amount of the flocculant added is preferably 5 to 50%, more preferably 10 to 30%.

Note that the amount of dry SS flowing into the coagulation tank 8 is the amount of dry SS flowing into the coagulation tank 8. If excess sludge (described later) does not mix into the V tank 8, this is the amount of dry SS in the night soil sent by the pump 6, and if excess sludge is mixed in, the amount of dry SS in the human waste is the amount
and the total amount of dry SS in the excess sludge.

In the present invention, in the coagulation tank, most of the phosphorus components in human waste are fixed by the action of the coagulant, and are thought to exist in the coagulated sludge in a fixed state, but it is necessary to supply only the amount necessary for the biological reaction. Therefore, the aggregation reaction is suppressed and the necessary amount of phosphorus component remains in the liquid. Such residual amount can be achieved by adjusting the amount of coagulant added. The amount required for biological reactions is generally BOD:P (
phosphorus) = 100: about 0.5 to 1. In the case of human waste Bol 15000ppm, phosphorus is 25-50p
About pm is required.

The sludge flocculated in the flocculation tank 8 is supplied to the solid-liquid separator 10 by a pump (not shown) or by gravity flow. The solid-liquid separator 10 uses a fine mesh screen in this embodiment. The fine 1.1 screen preferably has a mesh size of 0.5 mm or more from the viewpoint of preventing clogging of the screen, and preferably a mesh of 5 mm or less from the viewpoint of preventing clogging of the membrane.

Human waste that has passed through the fine mesh screen 10 is transferred to a secondary storage tank 17
The flocculated sludge that does not pass is sent to the dehydrator 18. Although a screw press or a centrifugal machine can be used as the dehydrator 18, a screw press is preferable. The cake dehydrated in the screw press is incinerated in an incineration facility, and the filtrate is returned to the primary storage tank 5.

The dephosphorized human waste in the secondary storage tank 17 is supplied to the biological reaction tank 20 by the pump 19. In the biological reaction tank 20, a commonly known multi-stage aerobic and/or anaerobic biological reaction is performed, and organic matter, nitrogen components, etc. are decomposed and removed by oxidation or reduction. Regarding the structure inside the biological reaction tank, it is preferable to use the structure described in Japanese Patent Application No. 59-267725, which was previously proposed by the present inventor, but is not limited thereto. The problem is a blower.

The sludge after the biological reaction is transferred to an ultrafiltration device 2 by a pump 21.
2, where it is separated into solid and liquid by a UF membrane.

The UF membrane used in the present invention has a molecular weight cutoff of 100
Those in the range of 0 to 3 million are preferable, such as rUFPlo'', rUFP70'', and rUFP manufactured by Mitsui Petrochemical Co., Ltd.
71'' etc. are preferable.

The membrane-separated sludge is returned to the biological reaction tank 20, and a portion is treated as surplus sludge.

In the present invention, the excess sludge is preferably returned to the coagulation tank 8, so that the excess sludge can be treated at the same time as dephosphorization.

The membrane-treated permeated water is sent to the activated carbon adsorption tower 23.

The activated carbon adsorption tower 23 not only performs advanced treatment of organic substances, but also performs decolorization specific to human waste. The final treated water is discharged from the treated water pit 24 to the outside of the system.

[Experimental Example] Experimental Example l 300 ran of human urine and 10 ran of surplus sludge with the composition shown in Table 1 below
0 mJl was placed in a flocculation tank and mixed to create a mixed stock solution.

Table 1 Note) Kyo: Not measured T-P: Total phosphorus concentration (same below) Next, the following flocculant was added to the above mixed stock solution.

■Polymer flocculant: Product name: rC-480J (cationic polymer flocculant) manufactured by Nimitsui Cyanamid Co., Ltd. Addition amount: 35 m of 0.2 W/V% liquid (dry s
(approx. 1.8% per s) ■Polyferric sulfate: Product name: Nissen Mining Co., Ltd. "Polyferric sulfate" Addition amount: 1
00Q+sg (approximately 23% based on dry ss) The pH was adjusted to 7 using caustic soda if necessary.

After stirring in a coagulation tank, solid-liquid separation was performed using a fine mesh screen to obtain separated water with the following composition.

(Composition of screen separated water) BOD 5500 mg/ISS
250 mg/IT-P
41 mg/liter The above-mentioned separated water was supplied to a biological reaction tank and treated, and solid-liquid separation was performed using a UF membrane. As a result, the composition of the treated water was as follows.

(Composition of IJF treated water) BOII 15 mg/stand SS
trace T-P O, 9 mg/degree of color change 500 degrees The above OF treated water was further treated with activated carbon, and the composition of the final treated water was as follows.

(Composition of activated carbon treated water) BOD 9 mg/SS
trace T-P O, 9 mg/discoloration degree 6 degrees Experimental Example 2 The experiment was conducted in the same manner as in Experimental Example 1 except that the amount of flocculant added was changed as shown in Table 2.

Table 2 shows the relationship between the amount of coagulant added and the treatment results. As is clear from the same table, it can be seen that dephosphorization is effectively achieved when a polymer flocculant and an inorganic flocculant are added to the flocculating tank.

Comparative Experimental Example 1 An experiment was conducted in the same manner as Experimental Example 1 except that no inorganic flocculant was added.

The relationship between the amount of coagulant added and the treatment results is shown in Table 2. As is clear from the table, the T-P of the
/l, indicating that dephosphorization was not carried out effectively.

Comparative Experimental Example 2 In Experimental Example 1, when the treatment was carried out without adding a flocculant, the composition of the treated water after IJF membrane treatment was as shown below, and the T-P was quite high at 130 mg/JL. There was no phosphorus effect.

(Composition of IF treated water) BOo 20 mg
/See SS trace T-P 130 wrgl1 chromaticity
600 Degree Comparative Experimental Example 3 In Experimental Example 1, an inorganic flocculant was added to the biological reaction tank without adding a polymer flocculant. Although a larger amount was added than in Experimental Example 1, the same dephosphorizing effect as in Experimental Example 1 could not be obtained. In addition, too much load was placed on the tlF membrane, which caused severe clogging of the membrane, necessitating immediate membrane cleaning.

[Effects of the Invention] As is clear from the above experimental examples, according to the present invention, a dephosphorization effect can be achieved even with a small amount of coagulant added.

Furthermore, it is possible to reduce the amount of SS and organic matter brought into the biological reaction tank, contributing to a reduction in the load on biological reactions and increasing the efficiency of the main process reaction. Furthermore, it is possible to provide a dephosphorization process that effectively functions as a pretreatment suitable for treatment under highly concentrated sludge, which is unique to membrane treatment. In addition, since it is only necessary to provide dephosphorization equipment as a pre-treatment, if it can be combined with conventional dephosphorization treatment, the equipment cost will be significantly reduced and process management will be easier.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an embodiment of the method of the present invention. 1: Receiving tank 2: Pump 3: Coarse screen 4: Dehydrator 5, primary storage tank 6, pump 7: Dephosphorization equipment 8: Coagulation tank 9: Flocculant addition device 1O: Solid-liquid separation device 11; Stirrer 12: Polymer Coagulant tank 13: Stirrer 14: Polymer coagulant pump 15: Polyferric sulfate tank 16: Pump 17 Secondary storage tank 18: Dehydrator 19: Pump 20: Biological reaction tank 21: Pump 22: Ultra Filtration device 23: Activated carbon adsorption tower 24: Treated water pit

Claims (3)

[Claims] (1) In a human waste treatment method in which human waste is treated in a biological reaction tank, then solid-liquid separation is performed using an ultrafiltration membrane, and the sludge is returned to the biological reaction tank and a portion is treated as surplus sludge, the human waste is treated in a biological reaction tank. In the dephosphorization equipment, the phosphorus components contained in human waste are coagulated and solidified by adding a flocculant, and the separated liquid from which the flocculated solids are removed contains at least the amount necessary for biological reaction treatment. A dephosphorization method in human urine treatment using an ultrafiltration membrane, characterized in that the phosphorus component remains, and then the separated water is received in the biological reaction tank. (2) A method for dephosphorization in human urine treatment using an ultrafiltration membrane according to claim 1, wherein the flocculant is a combination of a cationic polymer flocculant and ferric polysulfate. . (3) Claims 1 or 2, characterized in that surplus sludge is mixed into a coagulation tank that constitutes the dephosphorization equipment.
A method for dephosphorization in human urine treatment using the ultrafiltration membrane described in Section 3.