JPH0975910A - Wastewater recovery and regeneration method - Google Patents

Abstract

(57) [Abstract] [Problem] Closed type that can efficiently recover and reuse most of wastewater without generating secondary industrial waste such as excess sludge and concentrated wastewater in wastewater treatment and recovery processes. Provide a recovery method. SOLUTION: Waste water is treated with activated sludge, activated carbon powder is added to activated sludge treated water, and the water is passed through an immersion type membrane separation device using a microfiltration membrane or an ultrafiltration membrane, and the permeated water is recovered as reclaimed water. To do. As the powdered activated carbon to be added to the activated sludge treated water, the powdered activated carbon produced from the excess sludge generated in the activated sludge treatment process of wastewater is used. [Effect] By adding activated carbon to the activated sludge treated water and passing it through an immersion type membrane separator, it is possible to remove N, P, organic substances, chromaticity, salts, SS, bacteria, odorous components, etc. in the wastewater. It is possible to obtain recycled water equal to or more than industrial water and miscellaneous water. By using surplus sludge as a powdered activated carbon material, the amount of sludge waste generated can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater recovery and recycling method, and more particularly, in recovering and recycling factory wastewater and sewage,
The present invention relates to a closed-type recovery / regeneration method capable of efficiently recovering and reusing most of wastewater with little generation of secondary industrial waste such as excess sludge and concentrated wastewater in wastewater treatment and recovery processes.

[0002]

2. Description of the Related Art From the viewpoints of protecting water resources and securing water sources during periods of drought and disasters, there has been an increasing demand in recent years for the development of technology for collecting industrial wastewater and sewage and processing it into reusable water quality. It's starting. At the same time, reclaimed water is required to have a quality equal to or higher than that of industrial water and miscellaneous water.
It is expected that the treatment process will be more highly advanced.

[0003]

[Problems to be Solved by the Invention] In order to recover and recycle wastewater in a comfortable social environment, most wastewater is efficiently recovered and reused without generating secondary waste. However, in the current treatment process, only a part of the drainage system that can be easily recovered is targeted, and most wastewater is discharged without being recovered and reused. In addition, in many cases, secondary industrial waste such as sludge and concentrated effluent is generated during regeneration, which causes a new treatment problem for these wastes.

The present invention solves the above-mentioned conventional problems, and when recovering and reusing factory wastewater and sewage, most of secondary industrial waste such as excess sludge and concentrated wastewater is treated in wastewater treatment and recovery process. It is an object of the present invention to provide a closed type recovery / regeneration method capable of efficiently recovering and reusing most of wastewater without being generated.

[0005]

In the wastewater recovery and regeneration method of the present invention, powdered activated carbon is added to activated sludge treated water obtained by treating wastewater with activated sludge, and a microfiltration membrane or an ultrafiltration membrane is used. A method of passing water through a submerged membrane separation device and collecting permeated water as reclaimed water, wherein, as the powdered activated carbon, use is made of powdered activated carbon produced from excess sludge generated in the wastewater activated sludge treatment step as a raw material. Is characterized by.

The following items are required items in the recovery and reuse of waste water.

Stable, safe and highly reclaimed water is obtained. No secondary waste is produced. Most of the wastewater can be collected and reused.

The present inventors have developed the wastewater recovery and regeneration method of the present invention as a process that can satisfy the above requirements.

In the present invention, for example, the secondary treated water obtained from the existing activated sludge treatment facility that treats the entire amount of the factory wastewater is used as a water source, and activated carbon is added to this to obtain a microfiltration (MF) membrane or By passing the water through an immersion type membrane separation device using an ultrafiltration (UF) membrane, it is preferable that the activated sludge treated water is an NH ₄ adsorption device, an immersion type membrane separation device, and a reverse osmosis (RO) membrane. By sequentially passing water through the separator, N, P, organic matter, chromaticity, salts, SS, bacterial cells, odorous components, etc. in the wastewater can be efficiently removed, and recycled water equal to or more than industrial water and miscellaneous water. Can be obtained.

Further, by utilizing the surplus sludge generated in the activated sludge treatment step as a raw material for the powdered activated carbon, the amount of sludge waste generated can be reduced.

In the present invention, it is preferable to incinerate the generated waste activated carbon, and in particular, this waste activated carbon incinerator is an exhaust gas combustion device for incinerating the exhaust gas generated from the activated carbon manufacturing process, and a waste film (waste immersion). It is preferable to use the generated heat as a heat source for an activated carbon production apparatus, etc., while also serving as an incinerator for membranes and waste RO membranes.

Concentrated waste water generated as a by-product such as RO membrane separator concentrated liquid and recycled waste liquid from the NH ₄ adsorption device are physically and chemically decomposed by an oxidative decomposition device which suppresses the generation of waste. Therefore, it is desirable to discharge only a limited minimum amount of drainage to sewers.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a system diagram showing a method of an embodiment of the waste water recovery and regeneration method of the present invention. In the following, this FIG.
Details of the processing method will be described for each of the main steps shown in FIG.

Activated sludge treatment device 1 In the present invention, wastewater (raw water) such as sewage or factory wastewater
Is treated with a usual activated sludge treatment device 1 to obtain activated sludge treated water. For this activated sludge treatment, any treatment method is adopted, and either a floating method or a biofilm method may be used.

The activated sludge treated water is the activated sludge treated water of the sewage treatment plant or the activated sludge treated water of the factory effluent, which is generally not subjected to advanced treatment such as denitrification and dephosphorization. It is secondary treated water. Therefore, it corresponds to the treated water discharged to general rivers and sea areas around BOD 20 mg / L and SS 20 mg / L, but it may be biological treated water that has been subjected to denitrification, dephosphorization, and the like.

In the present invention, as will be described later, the excess sludge generated in this activated sludge treatment (generated by backwashing in the biofilm method) is used as a raw material for producing powdered activated carbon, so that the amount of waste generated is reduced. can do.

NH ₄ adsorption device 2 The activated sludge treated water from the activated sludge treatment device 1 is
In the H ₄ adsorption device 2, NH ₄ adsorption treatment is performed with an adsorbent such as zeolite.

This NH ₄ adsorption step is provided when NH ₄ --N is contained in the activated sludge treated water,
By the biological denitrification process incorporated in the activated sludge treatment process,
It can be omitted when NH ₄ -N in the activated sludge treated water is below a predetermined concentration.

The NH ₄ concentration in the activated sludge treated water is generally a low concentration of several tens mg / L or less, and the concentration of alkali metal ions such as Ca and Mg is relatively low, so that the NH ₄ concentration in the activated sludge treated water is small. Adopting the adsorption method as the removal method is advantageous for obtaining good water quality, and the apparatus can be downsized.

As the adsorbent of the NH ₄ adsorbing device 2, ion exchange resin, zeolite and the like can be used, but zeolite, particularly clinoptilolite, is suitable because it has good selectivity for ammonia.

In the NH ₄ adsorption treatment, specifically, the activated sludge treated water is caused to flow into a zeolite packed tower which is Na-type with sodium salt such as sodium chloride in a downward flow or an upward flow, to obtain Na ions and NH ₄ ions. Is carried out by ion-exchange. In this case, the water flow rate of the packed tower depends on the NH ₄ concentration of the activated sludge treated water, but when the NH ₄ concentration is 10 mg / L or more, SV = 5 hr ⁻¹ or less is preferable. The NH ₄ concentration of water (outflow water) is 0.2 mg / L
It is possible to set the degree. When SS is contained in the activated sludge treated water and the SS concentration is 20 mg / L or more, it is preferable to install a simple filtration device for removing SS in the preceding stage of the NH ₄ adsorption device. mg /
If it is about L, it is also possible to use SS filtration together with the adsorption device.

[0023] In this NH ₄ adsorption step, at the time of increasing NH ₄ concentration in the treated water NH ₄ adsorber 2, reproduces the adsorbent such as zeolite. As a regenerant, it is common to use an aqueous NaCl solution of about 0.5 to 5% by weight. The use of a high-concentration aqueous solution of NaCl exceeding 5% by weight causes a problem in the treatment of the recycling waste liquid. From the viewpoint of treating the waste liquid for regeneration, a solution of 2% by weight or less is particularly desirable. The regeneration solution can be passed through either an upward flow or a downward flow, and the passage speed is preferably SV = 2 hr ⁻¹ or less. Although the passing amount depends on the concentration of the regenerating solution, the NH adsorbed on the adsorbent is passed by passing the regenerating solution in an amount of 10 to 20 times the adsorbent capacity.
90% or more of ₄ can be recovered. The recycled waste liquid generated by the regeneration of the adsorbent is guided to the oxidative decomposition device 7 described later for processing.

The activated sludge treated water contains SS,
When SS is filtered and trapped in the H ₄ adsorption device, before regeneration of the adsorbent, the same means as an ordinary filter is used, for example, backwash water is passed from the bottom of the packed bed, or air is removed from the adsorbent. Backwashing is performed by jetting backwashing water simultaneously or alternately. Backwash wastewater is transferred to raw water or activated sludge aeration tank for treatment.

As mentioned above, NH is added to the activated sludge treated water.
_{When 4-} N is not contained (when the NH ₄ concentration is 2 mg / L or less), the NH ₄ adsorption device 2 need not be provided.

Powder Activated Carbon Production Device 4 In this powder activated carbon production device 4, excess sludge generated from the activated sludge treatment device 1 is concentrated and dehydrated by a normal sludge dewatering device 3 to obtain a dehydrated cake having a water content of 80 to 85%. A powdered activated carbon is produced by using as a raw material. The dehydrated cake may be dehydrated by mixing the initial sludge with excess sludge.

For the production of activated carbon, the same method as a general method in which palm shell, walnut shell, coffee bean dregs, etc. are carbonized and then activated can be employed. Carbonization treatment has a water content of 80
The dewatered cake dehydrated to ~ 85% is crushed, and is performed in an electric furnace filled with nitrogen gas at 400 to 900 ° C for 2 to 4 hours,
The obtained charcoal is crushed into a powder having a particle size of 1 mm or less. The crushed coal is put into an electric furnace at 800 to 900 ° C., and steam activation is performed for 30 minutes to 2 hours using heated steam or heated steam in which nitrogen gas is blown. As the activation method, any other method such as a method using carbon dioxide gas can be adopted.

The yield of powdered activated carbon obtained from the dehydrated cake varies depending on the properties of surplus sludge and SS, carbonization and activation conditions, but is generally 10 to 25% per dry sludge amount.
Regarding the performance of the obtained powdered activated carbon, iodine adsorption and phenol adsorption performance are lower than those of palm shell activated carbon of the same particle size, but it can be sufficiently used as activated carbon.

In addition to the dehydrated cake of surplus sludge, the activated carbon producing apparatus 4 can also use as a raw material a waste material of an immersion membrane or an RO membrane described later. When an ion exchange resin is used as the adsorbent of the NH ₄ adsorption device 2, the waste ion exchange resin can be used as a part of the activated carbon raw material.

A small amount of tar is generated from the carbonization process of the activated carbon production apparatus 4, and methane, ethane, CO, C
Although O ₂ gas and the like are generated, these tars and gases are processed by the combustion / incineration device 8 described later.

Immersion Type Membrane Separation Device (Powder Activated Carbon Adsorption Dephosphorization Device) 5 In this immersion type membrane separation device 5, a flat membrane or a hollow fiber membrane-shaped MF is used.
A membrane or a UF membrane is dipped and installed in a tank, and the powdered activated carbon manufactured by the powdered activated carbon manufacturing apparatus 4 is used in the tank to treat water (effluent water from the NH ₄ adsorption apparatus 2 or the activated sludge processing apparatus 1). A), an activated carbon adsorption treatment of residual organic matter, particularly, a biodegradable organic matter is performed.

The substances adsorbed on the activated carbon are mainly biodegradable substances remaining in the activated sludge treatment, and the chromaticity component,
Odorous components, surfactants, trihalomethanes, etc. are also removed. In this adsorption treatment, in order to enhance the adsorption efficiency of the powdered activated carbon, it is preferable to set the flow rate in the tank to 30 cm / sec so that the activated carbon is sufficiently mixed in the tank.

The residence time of the water to be treated varies depending on the performance and particle size of the powdered activated carbon, but is preferably 30 minutes or longer.

The amount of the activated carbon charged depends on the organic matter concentration of the water to be treated, but the adsorption performance of the activated carbon produced by the activated carbon producing apparatus 4 is about half that of commercially available activated carbon. Add more than twice the amount as when using commercially available activated carbon. When the amount of activated carbon that can be produced by the activated carbon producing apparatus 4 is less than the required amount, the insufficient amount is supplemented with commercially available activated carbon.

The waste activated carbon which has reached the saturation of the adsorption capacity is concentrated at the bottom of the tank together with the phosphorus-containing sludge described later, transferred to the combustion / incinerator 8 described later, and incinerated.

When the water to be treated contains phosphorus, an aggregating agent such as iron salt or aluminum salt is added to the tank to mainly remove phosphorus such as orthophosphoric acid simultaneously by the aggregating and dephosphorizing treatment. In addition, when the activated sludge treatment device 1 has a biological dephosphorization process, or when raw water does not contain phosphorus, it is not necessary to add a coagulant.

It is necessary to add the coagulant in the minimum amount necessary for dephosphorization so that excess iron or aluminum does not increase the load on the RO film in the subsequent stage. When iron salt is used as a coagulant in a general coagulation-sedimentation dephosphorization treatment, FePO ₄ and Fe
The amount of coagulant added is 2 to 3 times the stoichiometrically required amount of (OH) ₃ . However, in the immersion type membrane filtration system, it is not necessary to form flocs having a good sedimentation property as in the coagulation-sedimentation treatment, and therefore, the addition amount of the coagulant is sufficiently within twice the stoichiometric amount. .
Further, it is not necessary to use a polymer coagulation aid together. Usually, when the phosphorus component of the water to be treated is otolinic acid, it is possible to make the phosphorus concentration of the treated water about 0.1 mg / L by adding a coagulant corresponding to twice the stoichiometric amount. Become.

The phosphorus-containing sludge generated by this coagulation dephosphorization treatment is withdrawn from the bottom of the tank together with the waste activated carbon, and is incinerated in the combustion / incineration device 8 described later.

As described above, when the target water does not contain phosphorus, or even when phosphorus is contained, dephosphorization is not carried out in the tank of the immersion type membrane separator, but is carried out by the RO membrane separator at the subsequent stage. In some cases, it is not necessary to add a flocculant.

The treated water after the activated carbon adsorption treatment and, if necessary, the dephosphorization treatment is MF membrane or U immersed in the tank.
Membrane filtration with F membrane.

The MF membrane or UF membrane immersed in this tank is generally a flat membrane made of polyethylene or polypropylene, or a hollow fiber, or a tubular membrane made of a ceramic material. , The liquid in the tank is made to flow so that the liquid in the tank can sufficiently come into contact with the membrane surface. Examples of this flow means include a stirrer, pump circulation, aeration and the like. Alternatively, a method of bringing the liquid in the tank into contact with the surface of the film by rotating these films in the tank can be adopted. The point to be noted when installing the membrane is to prevent the powdered activated carbon and dephosphorized coagulated sludge charged in the tank from accumulating on the surface of the membrane, and to keep the activated carbon and coagulated sludge flowing on the surface of the membrane. It is to adjust the situation and the installation place. For example, it is preferable to install an air diffusing tube at the bottom of the tank, arrange the membrane on the air diffusing tube, and arrange the membrane in the upward flow due to aeration.

The permeated water of the membrane separation device 5 has a pressure-
A method of suctioning under a reduced pressure of 0.1 to -0.3 Kg / cm ² is generally used.

When contaminants such as organic matter, sludge and various salts adhere to the surface of the immersion membrane or inside the membrane and the amount of permeated water decreases, the membrane is washed. The membrane is washed by backwashing in which washing water is supplied from the permeate side of the membrane while the membrane is immersed in the tank.

Treated water may be used as the wash water, but since the degree of recovery gradually decreases only by backwashing with water, it is preferable to periodically add a detergent to the backwash water for chemical cleaning. . Although any cleaning agent can be used, hydrogen peroxide or ozone is preferable. For example, 1 to 10% by weight of hydrogen peroxide solution is injected to oxidize hydrogen peroxide and bubbles generated from hydrogen peroxide. A method of decomposing contaminants or peeling them from the film by using is suitable.

Since hydrogen peroxide and ozone remaining in the tank after the cleaning are rapidly decomposed by the powdered activated carbon in the tank, it is not necessary to discharge the cleaning waste liquid to the outside of the tank.
In addition, by using hydrogen peroxide or ozone,
There is also no risk of increasing the salt load of the membrane.

At the bottom of the tank in which the membrane is immersed, there is provided a powder activated carbon charged into the tank and a precipitation part capable of concentrating the activated carbon and sludge in order to discharge the coagulated sludge generated by dephosphorization. The waste activated carbon and the phosphorus-containing sludge in which the adsorption of organic substances is saturated are concentrated here and transferred to the combustion / incineration device 8 described later.

Further, although the waste immersion membrane is also incinerated by the combustion / incineration device 8, it can be used as a raw material for producing powdered activated carbon.

The membrane permeated water of the immersion type membrane separation device 5 is further passed through the RO membrane separation device 6 in the subsequent stage, but depending on the use of the recovered reclaimed water, desalting treatment by the RO membrane is not required. There may be cases. In that case, the treated water (permeated water) of the immersion type membrane separation device 5 becomes the final recovered reclaimed water.

RO Membrane Separation Device 6 The quality of the permeated water from the immersion type membrane separation device 5 varies greatly depending on the properties of the target water, but is 1-5 mg / L of BOD or CO.
It contains D, NH ₄ —N is about 0.2 mg / L, and phosphoric acid is about 0.1 mg / L. Depending on the use of the recovered reclaimed water, there are some examples in which these water qualities can be used, but when water quality equivalent to industrial water or miscellaneous water is desired, RO membrane separation treatment is required.

The material of the membrane used for the RO membrane separation treatment is
Cellulose acetate is generally used, and the membrane shape includes hollow fiber shape, flat membrane shape, spiral shape, tubular shape, and the like. Generally, RO membrane separators have a pressure of 15 kg depending on the operating pressure of the membrane.
/ Cm ² near the low-pressure to standard pressure type in the vicinity of 30 Kg / cm ^2, are divided into 40 Kg / cm ² or more high-pressure. Recently, ultra-low pressure RO membranes and nanofilters (NF) with lower operating pressure have been developed and put into practical use. Although these low-pressure and ultra-low-pressure RO membranes and NF are difficult to obtain high desalination performance, they have many advantages from the viewpoint of energy saving because they have low operating pressure. Especially in the wastewater recovery process,
Generally, the salt concentration of wastewater is much lower than that of seawater, so low and ultra low pressure RO membranes and NF are used to increase the salt desalination rate to 50-6.
The method of operating at 0% is said to be more preferable in terms of energy saving.

These commercially available low pressure and ultra low pressure RO
When normal factory wastewater is used as raw water by using a membrane or NF, BOD and COD are 0.5 mg / L or less, N is 0.2 mg / L or less, P is 0.005 mg / L or less, F
e and Mn are 0.01 mg / L or less, and highly recovered reclaimed water in which Escherichia coli and general bacteria are not detected can be obtained. In addition, when municipal wastewater is used as raw water, the evaporation residue is 10-50 mg /
L, M-High water quality with an alkalinity of 10 to 20 mg / L can be obtained.

In these low-pressure and ultra-low-pressure RO membranes, when the concentration factor is increased, the operating pressure is increased and the amount of permeated water is reduced. Therefore, the concentration factor is generally 10 to 15 times. Therefore, a concentrated liquid having an organic matter concentration of 10 to 15 times is produced. This concentrated liquid is decomposed alone or in a mixture with the regenerated waste liquid from the NH ₄ adsorption device, and decomposed in the oxidative decomposition device 7 described later.

Waste RO generated from this RO membrane separation device 6
The membrane is incinerated by a combustion / incinerator 8 described later or used as a raw material for powdered activated carbon.

Oxidative Decomposition Device 7 In the concentrated liquid of the RO membrane separation device 6, the organic substances remaining without being adsorbed and removed by activated carbon are concentrated 10 to 15 times. The TOC concentration varies depending on the properties of the raw water, but it may be 50 to 150 mg / L. Also, N
When the H ₄ adsorption device 2 is adopted, a regeneration waste liquid of the adsorbent is generated as described above. The NH ₄ concentration in the regeneration waste liquid is 100 to 500 mg / L, although it varies depending on the regeneration conditions.
Becomes

When treating the concentrated liquid or the regenerated waste liquid of the RO membrane separation device 6, the regenerated waste liquid has a high salt concentration, but biochemical nitrification denitrification is possible. But R
Since the hardly decomposable substance is concentrated in the concentrated liquid of the O membrane separation device 6, biochemical treatment is difficult. Further, a method of concentrating with an RO membrane is also conceivable, but there remains a problem in processing a new concentrated liquid.

Therefore, in the present invention, the oxidative decomposition treatment using an oxidizing agent is used as the decomposition treatment method of the organic matter in the concentrated liquid of the RO membrane separation device 6 and the ammonia in the regenerated waste liquid of the NH ₄ adsorption device 2. Is preferred.

As the oxidizing agent, hydrogen peroxide, ozone, nitrite, etc. are used, and the addition amount thereof may be a reaction equivalent amount or more with respect to the organic substance and ammonia.

It is preferable to carry out the reaction in the presence of a catalyst because it proceeds at a relatively low temperature in a short time. In this case, as the catalyst, it is preferable to use a carrier such as titanium dioxide or alumina on which a noble metal such as platinum or palladium is supported.

The reaction temperature is arbitrary, but 100 ° C. or higher,
It is preferably carried out at 140 to 200 ° C., and decomposition can be carried out at this temperature in a short time.

For example, when a concentrated liquid containing an organic substance is oxidatively decomposed with hydrogen peroxide in the presence of a catalyst in which platinum is supported on titanium at a high temperature of 140 to 170 ° C., the decomposition can be efficiently performed, and the organic substance is oxidized. It is decomposed into carbon dioxide and removed.

Also, sodium sulfite was added as a reaction equivalent to the waste waste liquid containing ammonia, heated to 140 to 170 ° C., and passed through a reaction column filled with a titanium-platinum catalyst to convert ammonia to nitrogen gas. It can be oxidized and removed.

When treating the concentrated waste liquid in which the concentrated liquid and the recycled waste liquid are mixed, a platinum catalyst is used and the temperature is 100 to 20.
By reacting with hydrogen peroxide under the condition of 0 ° C,
Organic matter and ammonia can be decomposed at the same time.

Further, NH ₄ in the regenerated waste liquid is oxidized to nitrogen gas with a nitrite in the presence of a platinum catalyst, and then hydrogen peroxide is added to the mixture, which is then brought into contact with the platinum catalyst to successively undergo oxidation decomposition treatment. Is also possible. In this case, the amount of nitrous acid used may be equivalent to the stoichiometric amount of reducing to nitrogen gas with respect to the amount of NH ₄ —N, and the amount of hydrogen peroxide used may be equal to the amount of carbonic acid relative to the TOC amount of the mixed concentrated waste liquid. It is 1.2 to 1.5 times the stoichiometric amount that decomposes to gas.

With such an oxidation treatment, 90% of NH ₄ --N
% Or more and 90% or more of TOC can be decomposed and removed. The treated water in the oxidative decomposition device 7 is discharged.

Combustion / Incineration Device 8 As described above, the activated carbon production device 4 generates exhaust gas containing tar, methane, ethane, CO, CO _{2, and the} like. Further, waste activated carbon and phosphorus-containing sludge are generated from the immersion type membrane separation device 5. Furthermore, a dipping film for disposal is generated. Waste RO membranes are also generated from the RO membrane separation device 6. combustion·
The incinerator 8 is an apparatus that incinerates the exhaust gas, waste activated carbon, waste film, and the like, recovers the heat, and uses the heat as a heating source for the activated carbon manufacturing apparatus 4 and the like. Since the ash from the combustion / incinerator 8 contains phosphorus, it can be used as a fertilizer.

The waste immersion membrane and the waste RO membrane can be used as the raw material for the powdered activated carbon in the activated carbon manufacturing apparatus 4 as described above.

According to such a method of the present invention, the turbidity is 2
0 degree or less, pH 6.5 to 8.0, alkalinity 75 mg /
L or less, evaporation residue 250 mg / L or less, chloride ion 8
0 mg / L or less, iron 0.3 mg / L or less, Mn 0.2 m
It is less than g / L and does not contain nitrogen, phosphorus, Escherichia coli, surfactants, trihalomethanes, etc., and has no offensive odor or coloration, and is recovered water of a quality equal to or higher than that of ordinary industrial water or miscellaneous water. be able to.

[0068]

The present invention will be described more specifically with reference to the following examples.

Example 1 Reclaimed water was recovered according to the method shown in FIG. 1 using the total wastewater of the textile dyeing factory as raw water. This integrated wastewater is BOD5
00 to 1300 mg / L, COD 250 to 800 mg / L
L, SS 300 to 650 mg / L, all-N 30 to 120
mg / L, total -P4 to 12 mg / L, the color tone is brown to black, and the waste water contains a surfactant and whose water quality varies greatly.

The activated sludge treatment device 1 has an aeration tank residence time of 2
Operated for 4 hours at a BOD load of 0.5 to 1.3 Kg / m ³ , the treated water quality was BOD 25 to 35 mg / L, and COD2.
7-45 mg / L, SS5-12 mg / L, total -N is 2
7 to 110 mg / L, and total-P was 3 to 10 mg / L. In addition, out of all -N, NH ₄ -N is 25 to 95 mg /
Of L and all-P, PO ₄ -P was 3 to 8 mg / L.

Excess sludge generated from this activated sludge treatment device 1 is 450 to 1100 m including SS of integrated wastewater.
g / L, a cationic polymer dehydration aid was added, and the average water content in the sludge dehydrator (belt press type dehydrator) 3 was 8
Dehydrated to 3%. Dehydrated cake has an average organic content of 8
2%.

In the NH ₄ adsorption device 2, 0.5 L of zeolite (clinoptilolite from Akita, Japan) having an average particle size of 1.25 mm was filled in a column having an inner diameter of 50 mm and a length of 500 mm, and a 2 wt% saline solution was added. After passing 10 L upward flow of water to convert the zeolite to Na type, NH ₄ —N 45 mg /
L (average) of the activated sludge treated water has a flow rate of 2.5 L / hr
(SV = 5 hr ⁻¹ ) and water was passed in an upward flow. NH ₄ -N of the treated water (outflow water) was 0.15 to 0.2 mg / L from immediately after passing water until 24 hours. After 24 hours of passing water, the zeolite was regenerated using 10 L of a 2 wt% saline solution. NH ₄ -N regeneration effluent is 263 mg / L, the regeneration efficiency was 97.8%.

In the powder activated carbon producing apparatus 4, the dehydrated cake having a water content of 83% and an organic matter content rate of 82%, which was obtained by dehydrating the excess sludge of the activated sludge treatment apparatus 1 with the sludge dewatering apparatus 3, was used as the powder activated carbon. Was manufactured. In the carbonization treatment, the dehydrated cake was dried at 105 ° C. in advance, 100 g of dried sludge from which water had been removed was crushed to a particle size of several mm, and charged with nitrogen gas into a stainless container having a vent hole with a capacity of 1 L. Then, it was carbonized at 500 ° C. for 3 hours using an electric furnace. After crushing this charcoal to a particle size of 0.5 to 1 mm, it was filled in a stainless steel column having an inner diameter of 70 mm and a length of 1000 mm, and nitrogen gas saturated with water vapor was flowed through the column at a flow rate of 1 L per minute. , 80 in the electric furnace
Activation treatment was performed at 0 ° C. for 1 hour. The activated carbon obtained by the activation treatment was 17 g, and the yield was 17% based on the amount of excess dry sludge. COD of this powdered activated carbon 33 mg /
The maximum COD adsorption capacity of L target water is 65 mg-
COD / g-activated carbon, which was about 1/2 of that of powdered activated carbon produced from commercially available palm shell.

[0074] In immersion membrane separation device 5, the average NH ₄ -N0.18mg / L of NH ₄ obtained from adsorption test device, average PO ₄ -P7mg / L, the average BOD28mg / L, NH average COD33mg / L ₄ 800 mg / L of powdered activated carbon produced by the activated carbon producing apparatus 4 was added to the adsorption-treated water. Further, ferric chloride was added at a Fe concentration of 50 mg / L. This added Fe concentration is twice the stoichiometric amount required to aggregate and remove the phosphate ions (7 mg / L) of the NH ₄ adsorption treated water. When ferric chloride was added, the pH of the liquid in the tank was adjusted to 6.5 with sodium hydroxide. Also,
In order to fully perform activated carbon adsorption and aggregation reactions,
The mixture was allowed to stay for 0 minutes and vigorous stirring was performed.

This submerged membrane separation device 5 is a small one having a tank capacity of 10 L, and a small membrane device using a hollow fiber type MF membrane having a standard pore diameter of 0.1 μm is immersed and installed in the tank, and the membrane permeated water is passed. To 0.5 m ³ / by vacuum suction of -0.2 Kg / cm ^2.
It was obtained at a permeation flow rate of m ² · day. The quality of the membrane permeate is CO
_{D4.5mg / L, NH 4 -N0.5mg /} L, PO 4
-P 0.1 mg / L, surfactant (ABS) 0.001
It was below mg / L, and the color tone was colorless and transparent.

Next, this membrane-permeated water was passed through a low-pressure RO membrane separation device 6 using a hollow fiber RO membrane made of cellulose acetate under conditions of a salt desalination rate of 50% and a concentration ratio of 13 times.

The recovered reclaimed water (RO membrane permeated water) thus obtained was
The water was as follows, and it was odorless and non-colored high-quality treated water.

Water quality of recovered reclaimed water Turbidity: 1 degree or more pH: 7.4 COD: 0.5 mg / L or less NH ₄ -N: 0.2 mg / L or less PO ₄ -P: 0.005 mg / L or less Alkalinity: 45 mg / L Evaporation residue: 200 mg / L Cl: 65 mg / L Fe: 0.01 mg / L or less Mn: 0.01 mg / L or less Surfactant: 0.001 mg / L or less NH ₄ adsorption in the above treatment The waste liquid for regenerating the adsorbent from the device 2 has a salt concentration of 2% by weight and NH ₄ —N of 263 m.
g / L. A salt concentration of 1.1% by weight obtained by mixing the recycled waste liquid with the concentrated liquid of the RO membrane separation device 6, NH
A mixed waste liquid of _4- N156 mg / L and TOC 120 mg / L was oxidized by the oxidative decomposition apparatus 7. That is, a column (made of stainless steel having an inner diameter of 30 mm and a length of 300 mm) filled with 100 ml of a catalyst in which platinum is supported on titanium (stainless steel having an inner diameter of 30 mm and a length of 300 mm) was catalytically oxidized under the condition of a temperature of 160 ° C. using nitrous acid and hydrogen peroxide as oxidizing agents. First, for the treatment of NH ₄ —N, sodium nitrite was added in an amount of 768 mg / L, which was equivalent to the stoichiometric amount of NH ₄ —N, and water was passed in an upward flow at a flow rate of SV = 2 hr ⁻¹ . After the reduction treatment, the TOC oxidation treatment was performed in the same column at a temperature of 160.
It was carried out under the same conditions of C and SV = 2 hr ⁻¹ . The amount of hydrogen peroxide added at this time was 1020 mg / L, which was 1.5 times the stoichiometric amount at which the total amount of TOC was decomposed into carbon dioxide gas. Total-N in column effluent is 3-5 mg / L, TOC is 8-
It was 10 mg / L, and NH _4- N and TOC in the mixed waste liquid were decomposed by 92% or more. This oxidative decomposition treated water was discharged.

Further, the tar and gas generated in the powder activated carbon production apparatus 4, the waste activated carbon generated from the immersion type membrane separation apparatus 5, the phosphorus-containing sludge and the waste immersion membrane, and the waste RO membrane of the RO membrane separation apparatus 6 are Combustion / incineration processing was performed in the combustion / incineration apparatus 8 to obtain phosphorus-containing ash, and the generated combustion heat was effectively used as a heating source of the powdered activated carbon production apparatus 4.

In this example, the recovery rate of the above-mentioned water quality from the wastewater of the textile dyeing factory as the raw water was 75%, and the treated water discharged from the oxidative decomposition apparatus 7 was about 25 L per 100 L of the raw water. Yes, combustion / incinerator 8
The phosphorus-containing ash generated in 1 was about 14 g per 100 L of raw water.

[0081]

As described in detail above, according to the method for recovering and recycling wastewater of the present invention, when recovering and reusing factory wastewater and sewage, by-products such as excess sludge and concentrated effluent during wastewater treatment and recovery process It is possible to efficiently recover most of the wastewater and obtain recovered reclaimed water with high water quality, with almost no generation of industrial waste.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example method of a wastewater recovery and regeneration method of the present invention.

[Explanation of symbols]

1 Activated sludge treatment device 2 NH ₄ adsorption device 3 Sludge dewatering device 4 Powdered activated carbon production device 5 Immersion type membrane separation device 6 RO membrane separation device 7 Oxidation decomposition device 8 Combustion / incineration device

Claims (2)

[Claims] 1. An activated sludge treated water obtained by treating wastewater with activated sludge, and powdered activated carbon is added to the treated sludge to pass through an immersion type membrane separator using a microfiltration membrane or an ultrafiltration membrane. A method for recovering reclaimed water, which comprises using, as the powdered activated carbon, powdered activated carbon produced from excess sludge generated in an activated sludge treatment step of the wastewater as a raw material. 2. The wastewater recovery and regeneration method according to claim 1, wherein waste activated carbon generated in the immersion type membrane separator is incinerated.