JPH07185546A - Purifying treatment of sewage - Google Patents

Abstract

PURPOSE:To purify sewage stably over a long period of time by bringing ozone into contact with the sewage, then oxidizing and decomposing the sewage by aerobic microorganisms and subjecting the sewage to a purification treatment by an ultrafiltration and reverse osmosis membranes. CONSTITUTION:The secondarily treated water 3 which flows into an ozone reaction chamber 1 and is treated by a biological treatment, etc., is aerated with the ozone 7. Hardly decomposable polluting materials are denatured to easily decomposable materials to permit a biological treatment and are made low molecular and hydrophilic by this ozone 7. Next, the secondarily treated water 3 is aerated with the air in a biological filter vessel 10 and the polluting materials made further easier to be decomposed are decomposed by the aerobic microorganisms in a treating vessel 11; thereafter, the treated water is sent to an ultrafiltration device 17. The water is filtered by ultrafilter membranes 18 of a fraction mol.wt. of about 50,000 in the ultrafiltration device 17 and is in succession filtered by the ultrafilter membranes 24 of a reverse osmosis filter device 23. The treated water after the filtration is released from a treated water pipe 25. Further, the filtered polluting materials are returned by a reflux pipe 19 and are drained properly from a drain pipe 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sewage purification treatment method for treating secondary treated water of sewage.

[0002]

2. Description of the Related Art Conventionally, for example, a method shown in FIG. 10 is known as a method for purifying sewage by highly treating and reusing sewage secondary treated water.

The method for purifying sewage shown in FIG.
A coagulant 31 is added to coagulate the pollutants in the wastewater 32, and the suspended solids, colloidal components, and aggregates in the wastewater are removed by sand filtration 33, and then fine filtration (MF: Microfiltration).
) Fouling Ind (FI) as a water quality index in the membrane
ex) is set to 4 to 5 by precision filtration 34, and then reverse osmosis (RO: Reverse Osmosis) membrane is used to reverse osmosis 35.
Has done and is highly processed.

[0004]

However, in the method for purifying sewage described above, after the coagulating sedimentation 32 and the sand filtration 33, the F
Since the MF process 34 and the RO process 35 are performed so that the I value becomes 4 to 5, the RO film surface is easily contaminated and the R film is stable for a long time.
In order to carry out the O treatment 35, the RO membrane must be frequently backwashed, which reduces the treatment efficiency of the sewage and causes the problem that the treatment cost increases due to the backwashing.

Further, there is a problem that the amount of sludge generated by the coagulating sedimentation 32 and the sand filtration 33 is large, the advanced treatment of wastewater becomes complicated, and the treatment cost increases due to the sludge treatment. In addition, sludge is coagulated and settled by adding coagulant 31.
Meanwhile, the wastewater is contaminated with the coagulant 31.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for purifying sewage that reduces the load on the RO membrane and can be easily and inexpensively and efficiently treated.

[0007]

The method for purifying sewage of the present invention is a method for purifying sewage using a reverse osmosis membrane, in which sewage is contacted with ozone and contacted with ozone. The sewage is oxidatively decomposed by aerobic organisms, and the sewage oxidatively decomposed by the aerobic organisms is filtered by ultrafiltration and then purified by using a reverse osmosis membrane.

[0008]

The method for purifying sewage of the present invention makes ozone polluted in sewage to make pollutants in sewage easily decomposable, and oxidizes and decomposes the easily decomposable pollutants by aerobic organisms. After the ultrafiltration of sewage containing pollutants that are easily decomposed, it is purified by a reverse osmosis membrane, which reduces the load on the reverse osmosis membrane and reduces the pollution of the reverse osmosis membrane. The treatment is stable for a long time and the treatment efficiency is improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus of one embodiment of the method for purifying wastewater of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an ozone reaction tank, which has a height of about 4 m and a diameter of about 0.6 m.
Is formed in a substantially cylindrical shape, and an inflow pipe 3 into which the secondary treated water 2 as sewage after the sewage is treated by, for example, biological treatment is introduced is provided at the upper end.

Aeration means 5 is provided at the bottom of the ozone reaction tank 1, and an ozone generator 6 is connected to the aeration means 5 so that the secondary treated water flowing into the ozone reaction tank 1 is discharged. Aeration of ozone 7 to 2. Furthermore, ozone reaction tank 1
In the upper part of the, ozone 7 aerated in the ozone reaction tank 1
Alternatively, an exhaust valve (not shown) that exhausts the air that flows in together with the secondary treated water 2 is provided.

At the lower end of the ozone reaction tank 1,
A derivation pipe 8 is provided for outflowing the secondary treated water 2 to which the ozone 7 in the ozone reaction tank 1 is aerated and brought into contact with the outside of the tank.

Numeral 10 is a biological filtration tank, which is a biological filtration tank.
The treatment layer 10 is formed in a substantially cylindrical shape having a height of about 2 m and a diameter of about 0.8 m, and a treatment layer in which a carrier for supporting aerobic organisms (not shown) is filled in a substantially middle portion of the biological filtration tank 10. 11 are formed. A lead-out pipe 8 from the ozone reaction tank 1 is connected to the upper end of the biological filtration tank 10.

Further, at the bottom of the biological filtration tank 10, there is a blower.
An aeration means 13 for aerating the air from 12 is provided, and a pump 14 for flowing the secondary treated water 2 that has passed through the treatment layer 11 at the bottom and treated by aerobic organisms to the outside of the biological filtration tank 10. Is connected to the transfer pipe 15. An ultrafiltration device 17 is provided on the downstream side of the transport pipe 15.

The ultrafiltration device 17 is provided with an ultrafiltration (UF) membrane 18 having a cut-off molecular weight of about 50,000 and a hollow fiber shape and a membrane area of about 5 m ² . .
Further, on the upstream side of the ultrafiltration device 17 on the surface of the UF membrane 18 where the secondary treated water 2 from the carrier pipe 15 comes into contact, a reflux pipe 19 having a tip connected to the carrier pipe 15 upstream of the pump 14. Is provided. Further, the reflux pipe 19 is provided with a drain pipe 20 for draining the secondary treated water 2 in which sludge substances (not shown) that cannot pass through the UF membrane 18 due to reflux are drained, and treated by a sewage treatment device (not shown) or the like. Or, it is adapted to be returned to the ozone reaction tank 1 again.

A water supply pipe 22 is provided on the downstream side of the UF membrane 18 surface of the ultrafiltration device 17, and a reverse osmosis filtration device 23 is provided on the downstream side of the water supply pipe 22.

In this reverse osmosis filtration apparatus 23, a spiral reverse osmosis (RO) membrane 24 having an exclusion rate of inorganic salts such as sodium chloride of 40 to 98% has a membrane area of about 2. Plural pieces are arranged so as to be 2 m ² . The upstream end of the RO membrane 24 of the reverse osmosis filtration device 23, which comes into contact with the secondary treated water 2 from the water supply pipe 22, has a water pipe with a tip.
A reflux pipe 19 connected to 22 is provided. Further, the reflux pipe 19 is provided with a drain pipe 20 for draining the secondary treated water 2 in which the sludge substance which cannot pass through the RO membrane 24 due to the reflux is discharged, and is separately treated by a sewage treatment device (not shown) or the like. Alternatively, it is returned to the ozone reaction tank 1 again.

Further, on the downstream side of the RO membrane 24 surface of the reverse osmosis filtration device 23, there is provided a treated water pipe 25 for draining highly purified treated water.

Next, the operation of the purification process by the apparatus of the above embodiment will be described.

First, while the secondary treated water 2 flows into the ozone reaction tank 1 through the inflow pipe 3, the ozone generator 6 is driven to aerate the ozone 7 from the aeration means 5 to the secondary treated water 2. , Decomposes contaminants (not shown) in the secondary treated water 2.

Further, the secondary treated water 2 in which ozone 7 has been aerated in the ozone reaction tank 1 is passed through the outlet pipe 8 to the biological filtration tank 10
And the air from the blower 12 is aerated by the aeration means 13 to the secondary treated water 2 flowing in. Also,
The secondary treated water 2 that has flowed in drives the pump 14 of the carrier pipe 15 to form a treatment layer composed of a carrier carrying aerobic organisms.
11 is made to flow through, and is made to flow out from the carrier pipe 15 to the ultrafiltration device 17.

The secondary treated water that has flowed into the biological filtration tank has a pump 14 so that the amount of water is about 100 m ³ / day and the flow rate of the treated layer is about 200 m ³ / m ² / day. Drive and purify.

The secondary treated water 2 that has flowed into the biological filtration tank 10 oxidizes and decomposes pollutants that have become easily degradable in the ozone reaction tank 1 due to aerobic organisms when flowing through the treatment layer 11. hand,
Purified.

Further, the secondary treated water 2 which has flowed into the ultrafiltration device 17 from the biological filtration tank 10 through the carrier pipe 15 by the pump 14 at a flow rate of about 12 m ³ / day has a permeation rate of about 2%. 100 l / m
It is filtered by UF membrane 18 every ² days. Then, the secondary treated water 2 is an undegradable and easily degradable pollutant that was not oxidatively decomposed by the aerobic organisms in the treatment layer 11 of the biological filtration tank 10 during permeation of the UF membrane 18. Contaminants rougher than the cut-off molecular weight of UF membrane 18 of 50,000 are filtered off. In addition, the secondary treated water 2 containing contaminants finer than the cut-off molecular weight of the UF membrane 18 flows into the reverse osmosis filtration device 23 via the water supply pipe 22.

[0025] Then, the contaminants, which are coarser than the cut-off molecular weight of the UF membrane 18 filtered by the UF membrane 18 of the ultrafiltration device 17, are refluxed together with the secondary treated water 2 at a liquid volume of about 24 m ³ / day. From the pipe 19 to the ultrafiltration device 17 again via the transfer pipe 15.
Further, due to this reflux, when the pollutant reaches a predetermined concentration on the upstream side of the UF membrane 18, that is, at a rate of about 10% of the inflowing secondary treated water 2, it is not shown separately via the drain pipe 20. The water is sent to a sewage treatment device for treatment.

Next, the amount of water from the ultrafiltration device 17 is 1 m ³ /
The secondary treated water 2 that has flowed into the reverse osmosis filtration device 23 by day is R
The permeation rate of the O membrane 24 is 20 l / m ² / day and the RO membrane 24 filters. Then, the secondary treated water 2 is a contaminant finer than the molecular weight cut-off of 50,000 of the UF membrane 18 which was not filtered by the UF membrane 18 of the ultrafiltration device 17 during permeation of the RO membrane 24. Alternatively, inorganic salts such as phosphoric acid generated by the decomposition of ozone 7 in the ozone reaction tank 1 and the decomposition of aerobic organisms in the biological filtration tank 10 are filtered by reverse osmosis to produce secondary treated water. 2 is highly purified and discharged from the treated water pipe 25.

Further, the contaminant filtered through the RO membrane 24 has a liquid volume of about 12 m ³ / day, and the reverse osmosis filter 23 through the reflux pipe 19 and the water pipe 22 together with the secondary treated water 2. Sewage treatment (not shown) via the drainage pipe 20 at the time when the pollutant reaches a predetermined concentration on the upstream side of the RO membrane 24, that is, at a rate of about 10% of the inflowing secondary treatment water 2. Water is sent to the equipment and processed.

Next, the operation of the above embodiment will be described.

First, when ozone 7 is supplied to the secondary treated water 2 in the ozone reaction tank 1, as shown in FIG. 2 and Table 1, the pollutants in the secondary treated water 2 are decomposed.

That is, for example, ozone 7 which transforms as shown in FIG. 3 reacts with an organic unsaturated compound which is excited as shown in FIG. 4 to produce an ozonide as shown in FIG. In the presence of water, aldehydes, ketones, carboxylic acids, etc. are generated by ozonolysis, etc. to transform easily-degradable pollutants into easily degradable pollutants that can be bioprocessed, or to reduce the molecular weight to perform bioprocessing. Becomes easily degradable.

[0031]

[Table 1] In addition, the easily decomposable pollutants produced by decomposing hydrophobic organic unsaturated compounds and the like by contact with ozone 7 are
It shifts toward hydrophilicity and lower molecular weight, and becomes hydrophilic like contaminants such as hydrophilic aldehydes, ketones, and carboxylic acids.

When 10 mg / l of ozone 7 was supplied, as shown in FIG. 2 and Table 1, precise filtration (MF: Mi
crofiltration) Contaminants with a particle size of about 0.45 μm or less, such as bacteria that are filtered through the membrane, and pollutants with a molecular weight cut-off of about 5 to 200,000 are reduced, and the molecular weight cut-off is 1 to
About 50,000 pollutants have increased, and the total chemical oxygen demand (COD) has decreased by about 30%. Therefore,
It can be seen that most of the pollutants having a particle size of about 0.45 μm or less and a molecular weight cutoff of about 200,000 or more are decomposed.

Table 2 and FIG. 7 show the state of decomposition of pollutants in the secondary treated water 2 when the supply amount of ozone 7 was changed.

[0034]

[Table 2] From the results shown in Table 2 and FIG. 7, the supply amount of ozone 7 is 5
If it is less than mg / l, the amount of organic matter having a cut-off molecular weight of about 50,000 or more increases sharply. Moreover, even if the amount of ozone 7 supplied is 10 mg / l or more, the amount of organic matter having a molecular weight cutoff of about 50,000 or more hardly changes. 15 mg /
It should be 1 or less.

Next, in the biological filtration tank 10, FIG.
As shown in Fig. 3, the aerobic organisms supported on the carrier constituting the treatment layer 11 decompose the pollutants having a particle size of about 0.45 µm or less which cannot be decomposed by the ozone 7, and further the total chemical oxygen. Reduce demand (COD).

The purification treatment by the aerobic organism is
Since the pollutants in the secondary treated water 2 are made easily decomposable in advance by the ozone 7, the purification treatment can be easily performed.

Further, in the ultrafiltration device 17, as shown in FIG. 2 and Table 1, it can be seen that the molecular weight cutoff of about 50,000 or more is filtered.

Further, the UF film 18 which is refluxed by the reflux tube 19
Table 3 shows the amounts of pollutants having a molecular weight cutoff of 50,000 or more, which have been filtered by.

[0039]

[Table 3] From the results shown in Table 3, the concentration of the pollutants filtered through the UF membrane 18 of the secondary treated water 2 that is refluxed through the reflux pipe 19 is measured without direct ozone treatment and aerobic treatment.
It can be seen that it is lower than that filtered through membrane 18. Therefore, by ozone treatment and treatment with aerobic organisms,
It can be seen that the pollutants have been decomposed.

On the other hand, from Table 3, when the molecular weight cut-off of the UF membrane 18 is about 20,000, the concentration of the pollutants in the refluxed secondary treated water 2 is high, and it can be reliably filtered. I understand.

By the way, if the molecular weight cutoff of the UF membrane 18 is made finer than about 20,000, the filtration rate becomes higher,
The concentration of pollutants in the circulated secondary treated water 2 becomes high,
Concentration polarization in which the concentration of the pollutant in a portion extremely close to the UF film 18 surface becomes high occurs remarkably, and a secondary film of the pollutant is formed in a gel state on the UF film 18 surface. Therefore, the UF
The permeation of the sludge substance passing through the membrane 18 is alienated, and as shown in FIG. 8, the permeated water amount of the UF membrane 18 starts to extremely decrease.

Therefore, the secondary treated water 2 to be refluxed is filtered using the UF membrane 18 having a pollutant concentration (COD concentration) of about 10 mg / l or less, preferably a cutoff molecular weight of 50,000 or more.

Next, in the reverse osmosis filtration device 23, as shown in FIG. 2 and Table 1, contaminants having a molecular weight cutoff of about 1 to 50,000 are filtered and the molecular weight cutoff is about 1 or less. It can be seen that most of the pollutants have been filtered.

FIG. 9 shows the result of comparison of the permeated water amount of the RO membrane 24 with that of the conventional coagulation sedimentation, sand filtration, and precision membrane filtration followed by filtration with a reverse osmosis membrane.

From FIG. 9, in the conventional purification treatment, the amount of passing water begins to decrease immediately after the filtration, and almost no permeation is possible when the number of operating days exceeds 20, but according to the purification treatment according to the above embodiment, The amount of permeated water hardly decreases,
It can be seen that stable filtration is possible. Furthermore, since ozone that does not contaminate the secondary treated water 2 is aerated without adding a coagulant or the like, the secondary treated water 2 is not contaminated and can be efficiently purified.

As described above, the UF film 18 and R
The pollutants filtered on the O film 24 have already been generated by ozone 7.
Since it is made hydrophilic, adhesion to the UF membrane 18 and the RO membrane 24 is less likely to occur, the load on the UF membrane 18 and the RO membrane 24 is reduced, and efficient filtration is possible.

Therefore, in the above embodiment, the secondary treated water 2
By contacting ozone 7 with the ozone, the pollutants in the secondary membrane water 2 are easily decomposed so that they are easily decomposed by aerobic organisms, and the hydrophilic substances are made hydrophilic. Since it is further decomposed, it is possible to use the UF membrane 18 finer than the conventionally used MF membrane without reducing the amount of permeated water, and the UF membrane 18 is used to filter what is filtered by the RO membrane 24. Therefore, the load on the RO membrane 24 is reduced, the formation of the secondary membrane is suppressed, the contamination of the RO membrane 24 can be reduced, and the secondary treated water 2 can be efficiently purified to a high degree.

Furthermore, since the contamination of the RO membrane 24 can be reduced, the RO membrane 24 can be stably and efficiently purified for a long period of time without frequent backwashing, and the operating cost increases due to frequent backwashing, and the RO membrane can be cleaned. It is possible to prevent the damage of 24 and the reduction of the treatment efficiency due to the stop of the treatment process due to the backwashing, and the inexpensive purification can be performed efficiently, efficiently and highly.

[0049]

EFFECT OF THE INVENTION The method for purifying sewage of the present invention is to bring ozone into contact with sewage to make pollutants in sewage easily degradable.
This easily degradable pollutant is oxidatively decomposed by aerobic organisms, and the wastewater containing undegraded easily degradable pollutant is ultrafiltered and then purified by a reverse osmosis membrane. The load on the osmosis membrane can be reduced and the contamination of the reverse osmosis membrane can be reduced, and the purification process of the sewage can be stable for a long period of time and the treatment efficiency can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a method for purifying sewage according to the present invention.

FIG. 2 is an explanatory view showing a situation of secondary treated water in each treatment step of the above.

FIG. 3 is an explanatory view showing ozone as above.

FIG. 4 is an explanatory view showing the same organic unsaturated compound.

FIG. 5 is an explanatory diagram showing a situation of a purification process using ozone.

FIG. 6 is an explanatory diagram showing a situation of a purification process using ozone.

FIG. 7 is an explanatory diagram showing a state of a purification process by the upper limit outer filtration film.

FIG. 8 is an explanatory diagram showing a state of purification processing by the reverse osmosis membrane.

FIG. 9 is an explanatory diagram showing a conventional wastewater purification treatment method.

[Explanation of symbols]

 1 ozone reaction tank 2 secondary treated water as sewage 7 ozone 10 biological filtration tank 11 treatment layer 17 ultrafiltration device 18 ultrafiltration membrane 23 reverse osmosis filtration device 24 reverse osmosis membrane

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C02F 9/00 501 B 502 FG 503 C 504 A

Claims (1)

[Claims] 1. A method for purifying sewage using a reverse osmosis membrane, wherein sewage is contacted with ozone, and the sewage contacted with ozone is oxidatively decomposed by an aerobic organism to produce an aerobic property. A method for purifying sewage, which comprises filtering sewage that has been oxidatively decomposed by living organisms by ultrafiltration and then purifying it using a reverse osmosis membrane.