JP3278560B2 - Water treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water treatment apparatus provided with a membrane cartridge for separating water to be treated into a membrane inside a treatment tank.

[0002]

2. Description of the Related Art For example, in a water treatment facility for treating organic wastewater such as night soil, as shown in FIG. 3 and FIG. The device 3 is installed.

[0003] The membrane separation device 3 has a plate-shaped membrane cartridge 5 arranged in parallel at an appropriate interval inside a box-shaped membrane case 4 with an open top and bottom. Inside, an air diffuser 8 communicating with an air supply source such as a blower 7 outside the tank is arranged, and the membrane case 4 and the air diffuser case 6 are arranged one above the other.

[0004] In the membrane cartridge 5, an organic filtration membrane 10 is arranged on both surfaces of a filter plate 9, and a permeated water channel (not shown) communicating between the filter plate 9 and the filtration membrane 10 is formed in the filter plate 9. The suction tube 11 and the water collection tube 12 communicating with the permeated water flow path are provided. A suction means such as a permeated water pipe 13 and a suction pump 14 is provided so as to communicate with the water collection pipe 12.

In such a configuration, when the water to be treated 2 is subjected to membrane separation by the membrane separation device 3, the suction pump 14 passes through the permeated water pipe 13, the water collection pipe 12, and the suction tube 11 to the permeated water flow path of the membrane cartridge 5. By applying suction pressure or by setting the head of the water 2 to be treated above the membrane cartridge 5 to a filtration drive pressure, suspended substances such as activated sludge contained in the water to be treated 2 can be removed from the filtration membrane 10.
The permeated water permeated through the filtration membrane 10 and flowed into the permeated water flow path through the filtration membrane 10 is sucked by the suction tube 11, the water collection tube 12,
3 to the outside of the processing tank 1.

At this time, the air is aerated by the blower 7 through the air diffusing hole 8a of the air diffusing tube 8, and the gas-liquid mixed upward flow generated by the bubbles of the aerated air is caused to flow into the gap between the membrane cartridges 5 and 5, so that the Rub the entire membrane surface evenly,
The cake layer is prevented from being deposited on the surface of the filtration membrane 10.

[0007]

However, since the aeration intensity required for cleaning the membrane surface is as high as 5 m ³ / m ³ , the water to be treated containing nitrogen, such as biologically treated water after biological treatment, is subjected to membrane separation. In this case, NH ₄ —N present in the water to be treated is oxidized by oxygen dissolved in the water to be treated from the aerated air, and NOx tends to increase. Therefore, the denitrification treatment is performed while injecting methanol as a hydrogen source. There is a need to.

Further, even if the flow rate of the water to be treated into the treatment tank is reduced, the aeration intensity for cleaning the membrane surface cannot be reduced. Worsens.

Therefore, it is conceivable to clean the film surface with an oxygen-free gas. However, when the film is completely anaerobic, NOx present in the water to be treated is reduced and NH ₄ —N is eluted. It is necessary to use a gas containing about 8 to 10% oxygen.

Although it is conceivable to use a stirrer to generate a swirling water flow in the tank to clean the membrane surface, the stirrer does not have a sufficient membrane surface cleaning effect or an effect of releasing nitrogen in the water to be treated. It is necessary to clean the film surface with a gas containing oxygen.

The present invention solves the above-mentioned problems. When cleaning the membrane surface of a membrane cartridge with a gas such as air, a gas having a low oxygen concentration which does not cause an increase in NOx or NH ₄ -N in the water to be treated. It is an object of the present invention to provide a water treatment apparatus which can supply and can change the oxygen concentration without changing the aeration intensity even when the inflow amount of the water to be treated fluctuates.

[0012]

In order to solve the above-mentioned problems, a water treatment apparatus of the present invention is provided with a membrane cartridge for separating water to be treated into a membrane in a treatment tank, and a membrane cartridge below the membrane cartridge. In a water treatment apparatus provided with a diffuser for ejecting a gas for cleaning the surface, the treatment tank is formed in a closed manner, and the exhaust gas and air staying in the upper space in the tank are separated by a gas for cleaning the film surface.
Setting the circulation supplying circulating means to the air diffuser means as only circulating hand
A first flow control valve that regulates the amount of exhaust gas circulated
And a second flow control valve for adjusting the supply .

[0013] Further, the water treatment apparatus of the present invention is configured to membrane-separate biologically treated water obtained by treating organic wastewater in an aerobic tank and an anaerobic tank. According to the configuration described above, while the water to be treated is separated into membranes by the membrane cartridge inside the treatment tank and the membrane surface is washed with the membrane surface cleaning gas, the exhaust gas in the tank is diffused by the circulation means. An anaerobic state, that is, a low oxygen state, is realized by circulating and supplying the film surface cleaning gas containing exhaust gas from the diffuser means. Therefore, while the membrane surface cleaning is performed with the conventional aeration intensity, the membrane separation of the water to be treated, which causes inconvenience in the presence of a large amount of oxygen, can be performed.

Since the anaerobic state can be realized without reducing the aeration intensity as described above, it is possible to prevent an increase in NOx which is likely to occur when the biologically treated water is subjected to membrane separation. In addition, the elution of NH ₄ —N, which easily occurs under completely anaerobic conditions, can be prevented.

[0015]

Embodiments of the present invention will be described below. In FIG. 1 and FIG. 2, a water treatment facility 21 for treating organic wastewater such as night soil is composed of a deep reaction tank 2 for nitrification and denitrification.
2 and a membrane raw water tank 23.

The deep reaction tank 22 includes a tube 26 forming a descending flow path 24 and an ascending flow path 25, a circulating flow path 28 provided with a circulating pump 27, and a supply line for blowing air into the descending flow path 24. A raw water supply pipe 30 intermittently or continuously introduces organic wastewater, and a circulation flow path 28 and a descending flow path 24 are provided.
And the ascending flow channel 25 to supply air to the organic wastewater descending in the descending flow channel 24 without any excess or shortage.

The membrane raw water tank 23 is composed of an aerobic tank 31 arranged at the front stage, an anaerobic tank 32 arranged at the middle stage, a membrane separation tank 33 arranged at the latter stage, and a pump tank 34 arranged at the last stage. Then, primary treated water treated in the deep reaction tank 22 and fed by the liquid sending pipe 35 is introduced. Then, the primary treated water is supplied to an aerobic tank 31, an anaerobic tank 32, and a membrane separation tank 33.
The permeate in the membrane separation tank 33 flows out of the system as secondary treatment water, and the residue is removed from the pump tank 34.
Once stored, the sludge is sent back to the deep reaction tank 22 and outside the system as return sludge and excess sludge by the liquid feed pipe 36. In the lower part of each tank 31, 32, 33, 34,
Air diffusers 39, 40 communicating with blowers 37, 38 outside the tank
41, 42 are provided, and each diffuser 39, 40, 4
1 and 42, air is diffused in a pattern corresponding to each of the tanks 31, 32, 33 and 34.

The membrane separation tank 33 is as shown in FIG. 2, and a membrane cartridge 4 is housed inside a closed tank body 43.
4 is provided, and a suction pipe 46 for connecting the upper space in the tank to the suction side of the blower 38 is provided.

The membrane separation device 45 has the same configuration as the conventional one as described with reference to FIGS. 3 and 4, and therefore detailed description is omitted. In addition to a permeated water pipe 47 communicating therewith, the above-mentioned air diffusion pipe 41 is provided below the membrane cartridge 44. The air diffuser 41 is connected to the discharge side of the blower 38 by an air supply tube 48.

The suction port of the blower 38 and the suction pipe 46 are provided with flow control valves 38a and 46a. Hereinafter, the operation of the above configuration will be described.

The organic wastewater is intermittently or continuously charged into the deep reaction tank 22 through the raw water supply pipe 30, and the charged organic wastewater is driven by the circulation pump 27 so as to circulate the circulation flow path 28, the downflow path 24, and the ascending flowpath. Air is blown into the organic wastewater descending in the descending flow path 24 by the air supply means 29. As a result, the organic wastewater comes into sufficient contact with the activated sludge maintained at a high concentration in the tank, and the oxygen in the blown air descends with high efficiency into the organic wastewater while descending in the downflow passage 24. NH ₄ − in dissolved organic wastewater
N is nitrified by activated sludge under an aerobic condition in which a sufficient amount of oxygen is present.

Next, the air supply means 29 is stopped, and the organic waste water is caused to flow through the circulation flow path 28, the descending flow path 24, and the ascending flow path 25 without blowing air.
NO ₃ -N and the like in the organic waste water are reduced and denitrified to N ₂ by activated sludge under an anaerobic condition having a low oxygen concentration, and BOD is decomposed accordingly.

The primary treated water thus efficiently and stably subjected to nitrification, denitrification and BOD removal in the deep-layer reaction tank 22 in a state containing activated sludge is passed through the liquid sending pipe 35. It is sent to the aerobic tank 31 of the membrane raw water tank 23.

The primary treated water 31a that has flowed into the aerobic tank 31
In an aerobic condition where air is continuously supplied from the air diffuser 39, remaining NH ₄ —N and the like are nitrified by activated sludge,
It flows out to the anaerobic tank 32.

The nitrification-treated water 32a flowing into the anaerobic tank 32
In the anaerobic condition where air is intermittently supplied from the air diffuser 40, remaining NO ₃ -N and the like are reduced and denitrified by activated sludge and flow out to the membrane separation tank 33. In addition, the intermittent supply of air is performed at an interval and strength that prevent the activated sludge from settling.

The denitrification-treated water 33a flowing into the membrane separation tank 33
Is separated by a membrane cartridge 44 arranged in a membrane separation device 45, suspended matter such as activated sludge remains in the tank, and the permeated liquid is sent out of the system by a permeated water pipe 47.

At this time, the membrane cartridge 44 is denitrified in a state where the membrane surface cleaning is performed by the membrane surface cleaning gas continuously ejected from the air diffuser 41 and accumulation of suspended matter on the membrane surface is prevented. The membrane separation of the treated water 33a is suitably performed.

At this time, the exhaust gas staying in the upper space in the tank is sent to the suction side of the blower 38 through the suction pipe 46, and after being mixed with air as necessary, is supplied to the diffuser pipe 41. The inside of the tank is maintained in a low oxygen state while the aeration intensity required for cleaning the film surface is secured. As a result, it is possible to prevent an increase in NOx, which tends to occur in the conventional method of membrane-separating biologically treated water by using a gas containing a large amount of oxygen such as air as a gas for cleaning the membrane surface. In addition, the elution of NH ₄ —N, which tends to occur under completely anaerobic conditions, is also prevented.

The denitrification water 33a is supplied to the membrane separation tank 33.
When the amount of inflow varies the oxygen concentration is adjusted by changing the proportion of air to be mixed into the gas for film surface cleaning, elution increased and NH ₄ -N of NOx is prevented.

The activated sludge 34a that has been subjected to membrane separation in the membrane separation tank 33 and has flowed into the pump tank 34 is stored under aerobic conditions in which air is continuously supplied from the diffuser 42, and then partially returned to the sludge. Is sent as surplus sludge to the deep reactor 22 and the outside of the system through the liquid sending pipe 36.

In the above description, a flat membrane cartridge provided with an organic filtration membrane has been described as an example. However, the same configuration can be applied to any similar apparatus using a gas for cleaning the membrane surface. For example, a water treatment apparatus provided with a tubular or flat ceramic film inside a treatment tank is also included in the scope of the present invention.

[0032]

As described above, according to the present invention, the exhaust gas in the treatment tank is circulated and supplied, and the gas for cleaning the film surface containing the exhaust gas is jetted out. Anaerobic state can be realized while securing the aeration intensity,
In the presence of a large amount of oxygen, membrane separation of the water to be treated, which causes inconvenience, can be suitably performed. Variations in the amount of inflow of the water to be treated can be dealt with by changing the proportion of air mixed into the gas for cleaning the membrane surface.

As described above, since the anaerobic state can be realized while securing the aeration intensity, it is possible to prevent an increase in NOx, which is likely to occur when the biologically treated water or the like is subjected to membrane separation, and to prevent NH, which is likely to occur under a completely anaerobic state. Elution of _4- N can also be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of a water treatment facility in which a water treatment device according to an embodiment of the present invention is incorporated.

FIG. 2 is an overall configuration diagram of the water treatment apparatus shown in FIG.

FIG. 3 is an explanatory diagram showing a configuration of a conventional water treatment device.

4 is an overall configuration diagram of a membrane separation device installed inside the water treatment device shown in FIG.

[Explanation of symbols]

 22 Deep reaction tank 33 Membrane separation tank 33a Denitrified water 38 Blower 41 Aeration tube 43 Tank body 44 Membrane cartridge 46 Suction tube

Continuation of the front page (56) References JP-A-1-119397 (JP, A) JP-A-62-181772 (JP, A) JP-A-62-130799 (JP, U) (58) Fields investigated (Int) .Cl. ⁷ , DB name) C02F 3/12 C02F 3/28-3/34 101 C02F 3/02-3/10 B01D 65/02 520

Claims (2)

(57) [Claims] 1. A water treatment apparatus, comprising: a membrane cartridge for separating a water to be treated into a membrane inside a treatment tank; and a diffuser means for jetting a gas for cleaning a membrane surface below the membrane cartridge. was formed into sealable, only setting the exhaust gas and the circulation supplying circulating means air diffuser means and air as membrane surface cleaning gas remaining in the tank in the upper space, the circulation of exhaust gas circulation means
A first flow control valve for adjusting the flow rate and a second flow control valve for adjusting the air supply
A water treatment apparatus comprising a two-flow control valve . 2. The water treatment apparatus according to claim 1, wherein biological treatment water obtained by treating organic waste water in an aerobic tank and an anaerobic tank is subjected to membrane separation.