JP3871272B2 - Sewage treatment facility and sewage treatment method - Google Patents

Description

【００５３】
表１からわかるように、大腸菌群の不活化率は、塩素殺菌の場合も紫外線殺菌の場合もほぼ同様であることがわかる。ここで、殺菌に要した時間に着目してみると、紫外線殺菌の場合は、殺菌時間が０．２ｍｉｎと極めて短時間であるのに対して、塩素殺菌の場合は殺菌時間が１５ｍｉｎと長時間を要している。このことは、紫外線殺菌は、塩素殺菌と比較して極めて短時間で同様の殺菌効果があることを表している。そうすると、紫外線殺菌は、雨天時において短時間に多量に発生する超過分下水を迅速に処理可能な殺菌方法であるといえる。
【００５４】
（実験２：晴天時想定殺菌実験）
晴天時に主処理経路で処理された処理水に対して殺菌処理を行った場合を想定して下水処理場の二次処理水（紫外線透過率５０％Ｔ）を擬似処理水として用い、紫外線殺菌、塩素殺菌の順に殺菌処理した場合（以下、ＵＶ-ＣＬ処理と記載）と、塩素殺菌のみとした場合とについて、塩素投入量、殺菌時間、菌類の不活化率等を比較検討した。殺菌対照とした菌類は、実験１と同様に大腸菌群であり、用いた紫外線照射装置も実験１で用いたものと同様である。ただし、実験２においては紫外線出力を２．４ｋＷとした。その他の実験条件および結果は、表２に示す。
【００５５】
【表２】

【００５６】
表２からわかるように、大腸菌群の不活化率は、ＵＶ−ＣＬ処理の場合も塩素の殺菌のみの場合もほぼ同様であることがわかる。ここで、殺菌に要した時間に着目してみると、ＵＶ−ＣＬ処理の場合は、５ｓｅｃの紫外線照射と１ｍｉｎの塩素処理という極めて短時間である。それ対して、塩素殺菌の場合は殺菌時間が１５ｍｉｎと長時間を要している。さらに、ＵＶ−ＣＬ処理の場合には、塩素投入量が１ｍｇ-ＣＬ／Ｌであるの対して、塩素殺菌のみの場合は、４ｍｇ-ＣＬ／Ｌであり、１／４の塩素投入量となっている。このことは、ＵＶ−ＣＬ処理は、塩素殺菌のみと比較して極めて短時間で殺菌でき、かつ塩素投入量を削減できることを示している。そうすると、ＵＶ−ＣＬ処理は、晴天時における主処理経路で処理された処理水を短時間でかつ低塩素投入量で殺菌処理できる処理方法であり、これは残留塩素濃度を低減できる殺菌方法であるともいえる。
【００５７】
なお、本実験１および２により、雨天時および晴天時ともに同じ紫外線殺菌装置を使用して効率的な処理が可能であることも示された。
【００５８】
【発明の効果】
以上詳述のとおり、晴天時では、紫外線殺菌、塩素混和池の順に殺菌を行うことにより、塩素混和池での塩素使用量が削減されるとともに、これまで予測できない雨天時にしか使用されていなかった紫外線照射装置を有効に活用できるようになる効果が得られる。また、雨天時においては、紫外線照射による超過分下水に対して迅速な殺菌が行われるとともに、設計処理水量分に対して塩素混和池における通常の殺菌処理が図られ、未殺菌の処理水が放流等されることがないという効果が得られる。
【図面の簡単な説明】
【図１】本実施の形態にかかる下水処理設備および下水処理方法を説明するためのフロー図である。
【図２】紫外線照射装置の例を示す図である。
【図３】渦流式固液分離装置の例を示す斜視図である。
【符号の説明】
１…沈砂池、２…最初沈殿池、３…曝気槽、４…最終沈殿池、５…紫外線照射装置、６…塩素混和池、７…渦流式固液分離装置、８…高速繊維濾過装置、５０…紫外線照射装置外管、５１…紫外線照射ランプ、 ７０…円筒型水槽、７１…円筒型スクリーン、７２…円筒型水槽中央底部、Ｂ…副処理経路、Ｆ，Ｆ１，Ｆ２…流量計、Ｌ１、Ｌ２、Ｌ３、Ｌ４…流路（管渠）、Ｐ１，Ｐ２…汚濁度測定手段、Ｖ１，Ｖ２，Ｖ３…流路切替弁（可動堰）、Ｗ…被処理水。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sewage treatment facility for treating combined sewage and a sewage treatment method in the sewage treatment facility.
[0002]
[Prior art]
There are two types of sewers: “Separated sewer”, which is configured to drain rainwater and sewage into separate treatment pipes, and “Combined sewer”, which sends water to the treatment equipment using the same pipe. . The combined sewerage system has been adopted by local governments mainly in large cities from the late Meiji to the early Showa era when the sewerage system was rapidly popularized because it only requires one system of pipes and is easy to construct and inexpensive.
[0003]
In the combined sewer, a large amount of contaminated water mixed with sewage and rainwater is generated in rainy weather and flows into the sewage treatment facility. Therefore, in the sewage treatment facility for the combined sewer, the first sedimentation tank, aeration tank, and final sedimentation In addition to normal treatment paths such as ponds and chlorine-mixing ponds, or after sewage that exceeds the design treatment amount of this normal treatment path is first introduced from the settling basin and subjected to simple treatment such as contaminant removal treatment, or impurities Instead of removing, another processing path is provided in which chlorine is added to perform sterilization and discharge out of the processing system.
[0004]
However, since excessive sewage is generated in a large amount in a short time, the sterilization must be performed in a short time. However, the sterilization process by adding chlorine requires a residence time, and thus is not necessarily a suitable sterilization process. In addition, in order to shorten the residence time as much as possible, it is necessary to perform a large amount of chlorine input, and there is a problem that it is not possible to deny the possibility that residual chlorine will adversely affect the destination ecosystem.
[0005]
Therefore, in order to solve the problem of performing chlorine sterilization on such excess sewage, the present inventors in the previous application (Japanese Patent Application No. 2002-378422) have eddy currents as a process related to the other process path. Disclosed is a technique for disinfecting by using an ultraviolet irradiation device capable of high-speed sterilization within a few seconds to 1 minute in the subsequent stage while using a solid-liquid separation unit.
[0006]
[Patent Literature]
JP 2001-219193 A
JP 2000-185280 A
JP-A-11-347583
JP-A-11-216497
JP-A-9-271772
[0007]
[Problems to be solved by the invention]
However, the above-mentioned prior art usually requires an expensive, high-power ultraviolet irradiation device to achieve sufficient sterilization treatment for excess sewage with a relatively high turbidity, but it is usually difficult to predict in rainy weather. Because it is used only when sewage exceeding the design treatment amount of the treatment path flows into the treatment system, the cost of introducing the ultraviolet irradiation device is high despite the fact that it is an extremely excellent facility from the viewpoint of sterilization. There was a drawback that it was difficult to achieve an operating rate that would just meet.
[0008]
On the other hand, when excess sewage does not occur, a method of sterilizing with chlorine typified by sodium hypochlorite in a chlorine-mixing pond has been established, but problems such as chlorine persistence have been pointed out in recent years. There is a need to reduce the amount of chlorine used.
[0009]
Therefore, the main problem of the present invention is that the ultraviolet irradiation device that has been used only for the sterilization of excess sewage so far is also used in a normal treatment system, so that it is a disadvantage in terms of cost for introducing the ultraviolet irradiation device. The amount of chlorine used for sterilization treatment in normal processing such as in fine weather, so that it can be optimally sterilized depending on whether it is sunny or rainy. It is also intended to reduce the amount.
[0010]
[Means for Solving the Problems]
The present invention that has solved the above-described problems and the effects thereof are as follows.
<Invention of Claim 1>
A main treatment path comprising at least a first sedimentation basin into which combined sewage flows, an aeration tank for performing aeration treatment, and a final sedimentation basin for carrying out precipitation treatment in this order;
An excess sewage that exceeds the design treated water amount of the main treatment path is first supplied from the settling basin, and includes a sub-treatment path that performs turbidity removal treatment of the excess sewage, and
A sewage treatment facility comprising an ultraviolet irradiation device capable of controlling ultraviolet irradiation output and performing a sterilization treatment of treated water treated in the main treatment path or the sub-treatment path, and a chlorine mixing pond for chlorination. ,
When the inflow sewage does not exceed the design treatment amount of the main treatment path,
The treated water treated in the main treatment path is supplied in the order of the ultraviolet irradiation device and the chlorine basin, and sterilized,
When the inflow sewage exceeds the design treatment amount of the main treatment path,
After the amount of the design treated water in the main treatment path is treated in the main treatment path, it is supplied to the chlorine-mixing basin without being supplied to the ultraviolet irradiation device, and is sterilized. After being treated by the route, it is supplied to the ultraviolet irradiation device to be sterilized.
A sewage treatment facility characterized by being configured as follows.
[0011]
<Invention of Claim 2>
At least one of a turbidity measuring unit for measuring the turbidity of the treated water supplied to the ultraviolet irradiating device and a flow rate measuring unit for measuring the flow rate of the treated water supplied to the ultraviolet irradiating device, in the preceding stage of the ultraviolet irradiating device A sewage treatment facility according to claim 1.
[0012]
<Invention of Claim 3>
The sewage treatment facility according to claim 2, further comprising an irradiation output automatic control unit that automatically controls an ultraviolet irradiation output of the ultraviolet irradiation device based on at least one of a measurement value of the pollution degree measurement unit and a measurement value of a flow rate.
[0013]
<Invention of Claim 4>
The sewage treatment facility according to any one of claims 1 to 3, wherein the sub-treatment path includes at least one of a vortex type solid-liquid separation device and a fiber filtration device.
[0014]
<Derivation of Claim 5>
A main treatment path comprising at least a first sedimentation basin into which combined sewage flows, an aeration tank for performing aeration treatment, and a final sedimentation basin for carrying out precipitation treatment in this order;
A sewage in excess of the design treatment amount of the main treatment path is first supplied from the settling basin, and a sub-treatment path for performing turbidity removal treatment of the excess sewage, and
Sewage treatment in a sewage treatment facility comprising a UV irradiation device capable of controlling the UV irradiation output and performing a sterilization treatment of the treated water treated in the main treatment path or the sub-treatment path, and a chlorine mixing pond for chlorination. A method,
When the inflow sewage does not exceed the design treatment amount of the main treatment path,
The treated water treated in the main treatment path is supplied in the order of the ultraviolet irradiation device and the chlorine-mixing basin to sterilize,
When the inflow sewage exceeds the design treatment amount of the main treatment path,
The amount of the design treatment water in the main treatment path is treated in the main treatment path, and then supplied to the chlorine-mixing basin without being supplied to the ultraviolet irradiation device, and the sterilization treatment is performed for excess sewage. After processing with, supply to the ultraviolet irradiation device to sterilize,
A sewage treatment method characterized by the above.
[0015]
<Invention of Claim 6>
The output of the ultraviolet irradiation device when the inflow sewage does not exceed the design treatment water amount of the main treatment path is lower than the output of the ultraviolet irradiation device when the inflow sewage exceeds the design treatment water amount of the main treatment path. The method of operating a sewage treatment facility according to claim 5, wherein the ultraviolet ray is irradiated.
[0016]
<Invention of Claim 7>
The sewage treatment method according to claim 5 or 6, wherein at least one of a turbidity and a flow rate of treated water supplied to the ultraviolet irradiation device is measured, and an ultraviolet irradiation output of the ultraviolet irradiation device is controlled based on the measured value.
[0017]
<Invention of Claim 8>
The sewage treatment method according to any one of claims 5 to 7, wherein in the sub-treatment path, turbidity removal treatment is performed using at least one of a vortex solid-liquid separation device and a filtration device.
[0018]
(Function and effect)
In the present invention, conventionally, the ultraviolet irradiation device used only for the excess sewage is configured to be applied to the treated water treated in the main treatment path when the excess sewage part does not occur during fine weather. For this reason, the ultraviolet irradiation device is not deactivated, and an operation that matches the cost is performed. Moreover, since it is always operating and the ultraviolet irradiation device is not repeatedly turned ON / OFF, there is an advantageous effect from the viewpoint of the lamp life of the ultraviolet irradiation lamp.
[0019]
On the other hand, in the present invention, when the excess sewage is not generated, an ultraviolet irradiation device is disposed in the preceding stage of the chlorine mixing basin for the treated water treated in the main treatment path, and sterilized in the order of ultraviolet sterilization and chlorine sterilization. Do. When configured in this manner, the load on the subsequent chlorine mixing pond is reduced, the amount of chlorine used is reduced, and the influence of the ecosystem at the discharge destination is reduced by reducing the amount of chlorine used. In addition, effective sterilization can be expected with respect to, for example, Cryptosporidium, Giardia and the like having high chlorine resistance by combining chlorine sterilization and ultraviolet sterilization. Furthermore, when the treatment is performed by an ultraviolet irradiation device and chlorine sterilization, the sterilization time can be greatly shortened.
[0020]
On the other hand, the present inventors have configured the ultraviolet irradiation device and the chlorine mixing pond in this order, so that there is less residual chlorine and bacteria attached to the turbidity than arranging the chlorine mixing pond and the ultraviolet irradiation device in this order. It has been found that there is an advantage that the effect on the light is high and the light recovery of bacteria is small, and such an effect can be obtained in the present invention.
[0021]
In summary, when excess sewage is not generated, it is sterilized by ultraviolet sterilization and a chlorine basin, so the amount of chlorine used is reduced and the use of an ultraviolet sterilizer is used. It is used only when sewage is generated and is not deactivated. When excess sewage is generated, the main treatment route is sterilized with chlorine for excess sewage, as in the conventional example. Is sterilized by ultraviolet rays, and after being sterilized for both, it is released and untreated water is not discharged.
[0022]
On the other hand, the ultraviolet irradiation device used in the present invention can change the irradiation output of ultraviolet rays. This is because the treated water treated in the main treatment path undergoes aeration treatment and final sedimentation treatment, and thus has low pollution. Accordingly, a high bactericidal effect can be obtained with a low ultraviolet ray transmittance and a low irradiation output. On the other hand, excess sewage exceeding the design water volume of the main treatment path can occur during rainy weather, etc., and the process in the sub-treatment path is relatively simple. Compared with treated water, it has high pollution and low UV transmittance. Accordingly, when sterilizing by ultraviolet irradiation, ultraviolet irradiation with a higher output than the treated water treated in the main treatment path is required. For this reason, if the ultraviolet irradiation output is variable, the ultraviolet irradiation can be performed with an effective or minimum required output for each treated water, and the energy cost used for the irradiation can be suppressed.
[0023]
On the other hand, before the ultraviolet irradiating device, a pollution measuring means for measuring the turbidity of the treated water supplied to the ultraviolet irradiating device and a flow measuring means for measuring the flow of the treated water supplied to the ultraviolet irradiating device. When at least one is provided, the ultraviolet irradiation output of the ultraviolet irradiation apparatus can be optimized. In addition, the pollution degree as used in the field of this invention is a value used as the parameter | index of the contamination condition of the polluted water which affects ultraviolet-ray transmittance, and is a meaning containing at least turbidity, COD, BOD, TOC, TOD, and ultraviolet-ray transmittance. is there.
[0024]
In addition, if at least one of the vortex-type solid-liquid separation device and the filtration device is provided in the sub-treatment path, effective turbidity removal is performed when irradiating with ultraviolet rays, the ultraviolet transmittance increases, and sterilization by suitable ultraviolet irradiation is effective. Can be done. In other words, if the water to be treated contains a large amount of solids and has high turbidity, the ultraviolet light transmittance is low and the desired sterilizing effect may not be obtained even when irradiated with ultraviolet light. If a solid-liquid separation device or a high-speed filtration device is provided to separate and remove solid matter in the polluted water, the ultraviolet transmittance of the water to be treated is increased, so that the sterilization treatment by the subsequent ultraviolet irradiation device is effectively performed.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
The present embodiment will be described in detail below with reference to the drawings.
FIG. 1 is a diagram showing a sewage treatment facility according to the present embodiment. In the figure, 1 is a sand basin, 2 is a first sedimentation tank, 3 is an aeration tank, 4 is a final sedimentation tank, 5 is an ultraviolet irradiation device, 6 is a chlorine mixing pond, 7 is a vortex solid-liquid separation device, and 8 is a high-speed fiber. A filtration device, V1 to V3 are flow path switching valves, F is a flow meter, and P1 and P2 are turbidity meters, respectively. In the figure, an area surrounded by a dotted line A indicates a main processing path, and an area surrounded by a dotted line B indicates a sub processing path. In this equipment, the flow path is switched to L1 to L4 by the flow path switching valves V1 to V3.
[0026]
Further, the ultraviolet irradiation device to be used has a variable output, and further, a sub-treatment in rainy weather from an output capable of sterilizing the relatively low turbidity treated water treated in the main treatment path A. It is assumed that the output can be varied up to a high output that can sterilize the treated water with high turbidity treated by the route.
[0027]
In the following, including the explanation of this sewage treatment facility, when the combined sewage flowing into the sewage treatment facility such as in fine weather does not exceed the design treated water amount of the main treatment path A (hereinafter simply described as clear weather) The sewage treatment method in this sewage treatment facility is divided into cases where combined sewage exceeding the design treatment amount of the main treatment path A flows into the sewage treatment facility (hereinafter simply referred to as rainy weather). Detailed description.
[0028]
<Sewage treatment in fine weather>
In the sewage treatment facility according to the present embodiment (hereinafter simply referred to as the main sewage facility), the combined sewage (hereinafter simply referred to as sewage) that has passed through the combined sewer flows into the sand basin 1 first. Is done. In the sand basin 1, relatively large contaminants in the sewage are removed by the screen.
[0029]
The sewage from which impurities have been removed in the settling basin 1 is then supplied to the settling basin 2 first. In the first sedimentation basin 2, SS having a large specific gravity mainly composed of organic components in sewage is precipitated and separated as a preliminary treatment for aeration treatment. The precipitation treatment in the first settling basin can be carried out according to a conventionally known method, and the precipitation time and the like can be appropriately selected according to a conventionally known method.
[0030]
The sewage (clarified portion) initially treated in the settling basin is all supplied to the aeration tank in fine weather. In the aeration tank, aeration processing is performed according to a conventionally known processing method. The aeration treatment can be, for example, a biological treatment performed by mixing with aerobic bacteria and supplying air or oxygen. In this case, the fungi used, the aeration time, and the like can be appropriately selected according to a conventionally known technique. A floating substance (floc) is formed by the aeration process.
[0031]
Next, treated water containing aerated floc and the like is supplied to the final sedimentation basin, and flocs having a small specific gravity and easily floating due to the flow are settled and separated. The treatment in the final sedimentation basin can also be performed by a conventionally known technique.
[0032]
The clarified portion separated in the final sedimentation basin is supplied to the UV irradiation device in fine weather. That is, the ultraviolet irradiation device is used for excess sewage described later, but no excess sewage is generated in fine weather. Accordingly, in order to prevent the ultraviolet irradiation apparatus from becoming inoperative, treated water (hereinafter referred to as a clarified liquid) treated by the main treatment path A up to the aeration treatment is supplied in fine weather.
[0033]
In the ultraviolet irradiation apparatus, the clarified liquid has low turbidity and high ultraviolet transmittance, and the ultraviolet irradiation amount and the irradiation time are determined while taking care not to generate excessive output. And while paying attention to these points, the irradiation output in the ultraviolet irradiation apparatus can be determined by the degree of contamination of the treated water supplied to the ultraviolet irradiation apparatus. Here, the measurement of turbidity is conducted by using a tube tank or the like connected to the ultraviolet irradiation device or a storage tank in the previous stage, and an ultraviolet transmittance meter, turbidity meter, COD meter, BOD meter, TOC meter, TOD meter, etc. At least one measuring means P1 among the measuring means is provided to measure the turbidity, COD value, BOD value, TOC value, TOD value, ultraviolet transmittance, etc. of the clarified liquid. ₁ From this, it is possible to determine an irradiation output value at which optimum sterilization can be performed on the clarified liquid.
[0034]
Here, as shown in FIG. 2, as the ultraviolet irradiation device, a plurality of ultraviolet irradiation lamps 51, 51... Are arranged in a pipe 50 through which the water to be treated is circulated. It is preferable to use the ultraviolet irradiation device 5 that irradiates ultraviolet rays by allowing the water to be treated W to flow from the one side 50A and discharging from the other side 50B in the pipe. Since the ultraviolet irradiation device 5 having such a configuration can perform the ultraviolet irradiation treatment while flowing the water to be treated W, it is suitable for flowing and treating the clarified liquid in fine weather, and an excessive amount that flows irregularly in rainy weather. This is because it is also suitable for quickly treating and sterilizing sewage. Usually, since the transmittance of the clarified liquid with ultraviolet rays (254 nm) is 30 to 80% T, sterilization is possible with a residence time of about 5 seconds to 1 minute when the ultraviolet output is about 1 to 2 kW.
[0035]
The sterilized water that has been sterilized by the ultraviolet irradiation device 5 is then supplied to the chlorine-mixing basin 6. Here, in order to distribute the clarified liquid in the order of the ultraviolet irradiation device 5 and the chlorine mixing pond 6, the clarified liquid passes through the flow paths L1, L2, and L3 by operating the flow path switching valves V1 to V3 in the figure. And not through the flow paths L4 and L5. In this way, the clarified liquid is not supplied to the chlorine mixing basin 6 without passing through the ultraviolet irradiation device 5, and the treated water that has passed through the ultraviolet irradiation device 5 is not supplied to the chlorine mixing basin 6 from the flow path L5. The clarified liquid from the final sedimentation basin 4 is guided to the ultraviolet irradiation device 5 and irradiated with ultraviolet rays, and then supplied to the chlorine-mixing basin 6. Since the chlorine-mixing pond 6 has already been sterilized by ultraviolet rays in the previous stage, it can be treated with a small amount of chlorine input for the purpose of maintaining and assisting the sterilizing effect by ultraviolet rays. . The amount of chlorine input depends on the ultraviolet irradiation output in the ultraviolet irradiation device 5 in the previous stage, but can be about 1/4 to 1/15 of the conventional amount. Further, the mixing time with chlorine may be about 1/4 to 1/10 of the conventional time. Other operations in the chlorine mixing pond 6 can be performed by a conventionally known technique. For example, a conventionally known drug such as sodium hypochlorite can be used as the drug used for chlorine sterilization. Treated water that has been sterilized by chlorine in the chlorine mixing pond 6 can be discharged out of the treatment system. For example, it can be discharged into a river or the like.
[0036]
<Treatment in case of rain>
Next, sewage treatment during rainy weather will be described. The treatment in the settling basin 1 and the first settling pond 2 is the same as that in fine weather even in rainy weather. In rainy weather, sewage exceeding the design treatment water amount of the main treatment path A is generated. In this case, the excess sewage is led from the first settling basin 2 to the sub-treatment path B. As a method for leading to this sub-treatment path B, a weir is first provided in the middle of the pipe dredging from the settling basin 1 to the aeration tank 3, and the pipe dredging is configured so that sewage beyond the weir is directed to the sub-treatment path. To do. The sewage that exceeds the weir is sometimes referred to as overflow water, but is referred to as excess sewage in this specification.
[0037]
Then, the sewage supplied to the aeration tank 3 without passing through the weir as the design water amount of the main treatment path A is supplied to the final settling basin 4 after being subjected to the aeration treatment in the same manner as in fine weather, and also in fine weather in the same way. Precipitation treatment is done in the same way as time. That is, the processing is performed in the main processing path A in the same manner as in fine weather.
[0038]
And the treated water processed by the main process path A at the time of rainy weather is supplied to the chlorine mixing basin 6 without supplying to the ultraviolet irradiation device 5 unlike the time of fine weather. This is because the ultraviolet irradiation device 5 is used for the treatment of the excess sewage, so that the ultraviolet irradiation device 5 is not used for the treated water treated in the main treatment path A. In order to prevent the treated water treated in the main treatment path A from passing through the ultraviolet irradiation device 5, the flow path switching valves V1 and V2 are operated so that the clarified liquid flows through the flow paths L4 and L3. And not passing through the flow paths L1, L2.
[0039]
In this way, the clarified liquid supplied to the chlorine mixing pond 6 is sterilized by mixing with chlorine. The chlorine sterilization here is not sterilized by ultraviolet rays in the previous stage, so the chlorine amount and the mixing time according to the prior art are used. And after sterilizing in the chlorine mixing pond 6, it discharges | emits out of a processing system. For example, release into a river.
[0040]
On the other hand, the excess sewage led to the sub-treatment route B is subjected to turbidity removal treatment in the sub-treatment route B. Excess sewage increases rapidly in a large amount and in a short time, so as a turbidity removal treatment, a precipitation tank that requires a long sedimentation time is not suitable, and solid-liquid separation can be performed quickly. It is necessary to use the device 7. A vortex type solid-liquid separator is suitable as the solid-liquid separator. The vortex-type solid-liquid separation device feeds water to be treated into a cylindrical aquarium along the tangential direction of the aquarium, generates a vortex in the aquarium, and collects solids at the lower center of the aquarium. The clarified portion and the solid portion are separated, and the clarified portion is sent out of the water tank, and the collected solid content is pulled out of the water tank by the opening and closing of the extraction valve provided at the lower part of the water tank and pump means, and is separated into a solid and liquid. As a specific example, as shown in FIG. 3, a cylindrical screen 71 is arranged vertically in a cylindrical water tank 70, and water to be treated is placed in the cylindrical screen 71 along the tangential direction of the screen 71. The solid content is collected in the central lower part 72 of the water tank 70 while generating a vortex in the screen 71 and sending the clarified portion out of the tank through the screen 71, and the collected solid content is outside the water tank 70. Pull out And those which are configured.
[0041]
The sub-treatment path B of this sewage facility is provided with a flocculant addition means at the subsequent stage of the vortex type solid-liquid separation apparatus, and further with another vortex type solid-liquid separation apparatus at the subsequent stage of the flocculant addition means. It is preferable to install the first vortex type solid-liquid separation device, the conventionally known flocculant addition device, and the second vortex type solid-liquid separation device in this order.
[0042]
Moreover, the high-speed fiber filtration can be used for the solid-liquid separator in the sub-processing path. However, when trying to process the excess sewage with high turbidity only with the high-speed fiber filtration device, it takes time and effort to remove the supplemented solids, so when using the high-speed fiber filtration device, the vortex-type solid-liquid separation device, It is good to arrange in the order of the high-speed fiber filtration device.
[0043]
When it is raining, the turbidity-removed water that has been subjected to the turbidity-removing process in the sub-processing path B is supplied to the ultraviolet irradiation device 5 that was used for the above-mentioned process in the fine weather. Therefore, as described above, the treated water treated in the main treatment path A during rainy weather is not supplied to the ultraviolet irradiation device 5 so as not to pass through the flow paths L1 and L2 by the operation of the flow path switching valves V1 and V2. To. Here, the output of the ultraviolet irradiation device 5 is different from that in fine weather when it is raining, and is not subjected to final subsidence treatment, so the pollution level is high. Therefore, it is necessary to determine the irradiation output while paying attention to the fact that the output must be higher than that in sunny weather. The irradiation output in the ultraviolet irradiation device 5 can be determined by the turbidity of the treated water supplied to the ultraviolet irradiation device 5 as in fine weather. Here, the measurement of the turbidity is conducted in the same way as in fine weather, such as a tube connected to an ultraviolet irradiation device or a storage tank in the previous stage, and an ultraviolet transmittance meter, turbidity meter, COD meter, BOD meter, TOC in the storage tank. At least one measuring means P2 among measuring means such as a meter and a TOD meter is provided to measure the turbidity, COD value, BOD value, TOC value, TOD value, ultraviolet transmittance, etc. of the treated water. M ₂ From the above, it is possible to determine an irradiation output value at which optimum sterilization can be performed on the water to be treated.
[0044]
The sterilized water that has been sterilized by the ultraviolet irradiation device 5 is discharged outside the treatment system without being sent to the chlorine mixing basin 6 by operating the flow path switching valve V3 and passing through the flow path L5 in rainy weather. To do. For example, release into a river. This is because the chlorine-mixing pond 6 needs to treat the treated water treated in the main treatment path A.
[0045]
(Other)
The operation of the flow path switching valves V1 to V3 in this sewage facility is provided with a flow meter F for informing the generation of excess sewage in the middle of the pipe from the first settling basin 2 to the sub-treatment path B. On the basis of the measured value, the facility manager or the like may perform the operation manually, or may be configured to be switched by automatic control by a known computer control means or the like. Moreover, the measured value M is also used for the irradiation output control of the ultraviolet irradiation device 5 based on the degree of contamination. ₁ , M ₂ It may be performed manually by an administrator based on the above, or may be automatic control by known computer control or the like. The specific operation for changing the irradiation output of the ultraviolet irradiation device 5 depends on the operation method of the ultraviolet irradiation device 5 to be used.
[0046]
The change of the ultraviolet irradiation output is, for example, a case where the output is changed according to the turbidity. ₁ , M ₂ Until the value A exceeds the predetermined value A, the ultraviolet irradiation output is set to the output α. If the turbidity increases and exceeds the predetermined value A value, the ultraviolet irradiation output is increased from the output α to the output β, and the turbidity is further increased to the predetermined value. If the value B is exceeded, the ultraviolet irradiation output is changed so that the ultraviolet irradiation output is increased from the output β to the output γ. On the other hand, the measured value M measured by the pollution measuring meters P1 and P2. ₁ , M ₂ Is less than the predetermined value B, the ultraviolet irradiation output is reduced from the output γ to the output β. Further, when the turbidity is lower than the predetermined value A, the ultraviolet irradiation output is output from the output β to the output α. It is possible to change the ultraviolet irradiation output so as to decrease it. Rather than changing the UV irradiation output in steps of output α → output β → output γ or output γ → output β → output α, the UV irradiation output is also changed according to the continuous change in turbidity over time. It can be changed continuously over time.
[0047]
Moreover, although the said example is control by turbidity, as above-mentioned, according to the measured value of ultraviolet-ray-transmittance, COD value, BOD value, TOC value, and TOD value measured with the turbidity meter P1, P2, The ultraviolet irradiation output can also be changed. Further, as a judgment value for determining the irradiation output, a value obtained by multiplying a measured value of ultraviolet transmittance or turbidity by a COD value, an ultraviolet transmittance or a sum of turbidity and COD value, an ultraviolet transmittance or turbidity A value obtained by multiplying the measured value by the BOD value or a value obtained by multiplying the measured value of the ultraviolet transmittance or turbidity by the BOD value and the COD value can be determined as appropriate.
[0048]
On the other hand, the sterilization efficiency in the ultraviolet irradiation device 5 depends on the flow rate supplied to the ultraviolet irradiation device in addition to the pollution degree. That is, when the flow rate is large, it passes through the ultraviolet irradiation device 5 in a short time, so that irradiation with high output is required. Therefore, a flow meter F2 for measuring the flow rate of the clarified liquid is provided in the middle of the pipe shed from the final sedimentation basin 4 to the ultraviolet irradiation device 5, and the flow meter F3 is provided in the middle of the pipe shed from the sub-processing path B to the ultraviolet irradiation device 5. Measure the flow rate of clear liquid in fine weather and the flow of turbidity-removed water in rainy weather, and determine the ultraviolet irradiation output in the ultraviolet irradiation device 5 in consideration of the flow rate measured by these flow meters. can do. The specific mode of change can be performed in the same manner as in the example based on the turbidity.
[0049]
Most preferably, the ultraviolet irradiation output is determined in consideration of both the measured values of the above-described pollution degree and flow rate. In this case, for example, the calculation value represented by pollution degree × flow rate is used as an ultraviolet irradiation output determination parameter, and the ultraviolet irradiation output of the ultraviolet irradiation device 5 can be appropriately determined according to the parameter.
[0050]
<Experimental example>
Next, experimental examples of the present invention will be shown.
(Experiment 1: Expected sterilization experiment in rainy weather)
Assuming the treatment of excess sewage in rainy weather, the sterilization time and the sterilization treatment with the ultraviolet irradiation device using the high turbidity (ultraviolet light transmittance 30% T) simulated waste water We compared the inactivation rate of fungi. The fungus used as a sterilization control is the coliform group. The ultraviolet irradiation device used was a water-flowing type in which two medium-pressure mercury lamps with 4 kW output were arranged inside.
[0051]
The ultraviolet output in the ultraviolet irradiation device was 8 kW. On the other hand, the amount of chlorine input in chlorine sterilization was 10 mg-CL / L. Other experimental conditions and results are shown in Table 1.
[0052]
[Table 1]

[0053]
As can be seen from Table 1, it can be seen that the inactivation rate of coliform bacteria is almost the same in both the case of chlorine sterilization and the case of ultraviolet sterilization. Here, focusing on the time required for sterilization, in the case of ultraviolet sterilization, the sterilization time is as short as 0.2 min, whereas in the case of chlorine sterilization, the sterilization time is as long as 15 min. Is needed. This indicates that ultraviolet sterilization has the same sterilization effect in a very short time compared with chlorine sterilization. If it does so, it can be said that ultraviolet sterilization is a sterilization method which can process rapidly the excess sewage which generate | occur | produces in large quantities in a short time at the time of rain.
[0054]
(Experiment 2: Aseptic sterilization experiment in fine weather)
Assuming the case where sterilization treatment is performed on the treated water treated in the main treatment route in fine weather, the secondary treated water (ultraviolet light transmittance 50% T) of the sewage treatment plant is used as the pseudo treated water, The amount of chlorine input, the sterilization time, the inactivation rate of fungi, and the like were compared between a case where sterilization was performed in the order of chlorine sterilization (hereinafter referred to as UV-CL treatment) and a case where only chlorination was performed. The fungi used as a sterilization control are coliforms as in Experiment 1, and the ultraviolet irradiation apparatus used is the same as that used in Experiment 1. However, in Experiment 2, the ultraviolet output was 2.4 kW. Other experimental conditions and results are shown in Table 2.
[0055]
[Table 2]

[0056]
As can be seen from Table 2, it can be seen that the inactivation rate of the coliform group is almost the same both in the case of UV-CL treatment and in the case of only chlorine sterilization. Here, paying attention to the time required for sterilization, in the case of UV-CL treatment, it is an extremely short time of 5 seconds of ultraviolet irradiation and 1 minute of chlorine treatment. On the other hand, in the case of chlorine sterilization, the sterilization time is as long as 15 minutes. Furthermore, in the case of UV-CL treatment, the chlorine input is 1 mg-CL / L, whereas in the case of only chlorine sterilization, it is 4 mg-CL / L, which is a 1/4 chlorine input. ing. This indicates that the UV-CL treatment can be sterilized in an extremely short time as compared with only chlorine sterilization, and the amount of chlorine input can be reduced. Then, the UV-CL treatment is a treatment method that can sterilize the treated water treated in the main treatment path in fine weather in a short time and with a low chlorine input amount, and this is a sterilization method that can reduce the residual chlorine concentration. It can be said.
[0057]
In addition, this experiment 1 and 2 also showed that efficient treatment was possible using the same ultraviolet sterilizer in rainy weather and sunny weather.
[0058]
【The invention's effect】
As detailed above, in clear weather, sterilization in the order of UV sterilization and chlorine-mixed ponds reduces the amount of chlorine used in the chlorine-mixed ponds and has been used only in rainy weather that has not been predicted so far. The effect that the ultraviolet irradiation device can be effectively used is obtained. In rainy weather, excess sewage by ultraviolet irradiation is quickly sterilized, and normal sterilization treatment in the chlorine-mixing basin is planned for the amount of treated water, and unsterilized treated water is discharged. The effect that it is not equalized is acquired.
[Brief description of the drawings]
FIG. 1 is a flowchart for explaining a sewage treatment facility and a sewage treatment method according to the present embodiment.
FIG. 2 is a diagram showing an example of an ultraviolet irradiation device.
FIG. 3 is a perspective view showing an example of a vortex type solid-liquid separator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Sand basin, 2 ... First sedimentation tank, 3 ... Aeration tank, 4 ... Final sedimentation tank, 5 ... Ultraviolet irradiation apparatus, 6 ... Chlorine mixing tank, 7 ... Eddy current type solid-liquid separation apparatus, 8 ... High-speed fiber filtration apparatus, DESCRIPTION OF SYMBOLS 50 ... Ultraviolet irradiation apparatus outer tube, 51 ... Ultraviolet irradiation lamp, 70 ... Cylindrical water tank, 71 ... Cylindrical screen, 72 ... Cylindrical water tank center bottom part, B ... Sub-processing path, F, F1, F2 ... Flowmeter, L1 , L2, L3, L4 ... flow channel (pipe), P1, P2 ... pollution measuring means, V1, V2, V3 ... flow channel switching valve (movable weir), W ... treated water.

Claims (8)

A main treatment path comprising at least a first sedimentation basin into which combined sewage flows, an aeration tank for performing aeration treatment, and a final sedimentation basin for carrying out precipitation treatment in this order;
An excess sewage that exceeds the design treated water amount of the main treatment path is first supplied from the settling basin, and includes a sub-treatment path that performs turbidity removal treatment of the excess sewage, and
A sewage treatment facility comprising an ultraviolet irradiation device capable of controlling ultraviolet irradiation output and performing a sterilization treatment of treated water treated in the main treatment path or the sub-treatment path, and a chlorine mixing pond for chlorination. ,
When the inflow sewage does not exceed the design treatment amount of the main treatment path,
The treated water treated in the main treatment path is supplied in the order of the ultraviolet irradiation device and the chlorine basin, and sterilized,
When the inflow sewage exceeds the design treatment amount of the main treatment path,
After the amount of the design treated water in the main treatment path is treated in the main treatment path, it is supplied to the chlorine-mixing basin without being supplied to the ultraviolet irradiation device, and is sterilized. After being treated by the route, it is supplied to the ultraviolet irradiation device to be sterilized.
A sewage treatment facility characterized by being configured as follows. At least one of a turbidity measuring unit that measures the turbidity of the treated water supplied to the ultraviolet irradiating device and a flow rate measuring unit that measures the flow rate of the treated water supplied to the ultraviolet irradiating device is provided at the front stage of the ultraviolet irradiating device. A sewage treatment facility according to claim 1. The sewage treatment facility according to claim 2, further comprising irradiation output automatic control means for automatically controlling the ultraviolet irradiation output of the ultraviolet irradiation apparatus based on at least one of the measurement value of the pollution degree measurement means and the measurement value of the flow rate. The sewage treatment facility according to any one of claims 1 to 3, wherein the sub-treatment path includes at least one of a vortex type solid-liquid separation device and a fiber filtration device. A main treatment path comprising at least a first sedimentation basin into which combined sewage flows, an aeration tank for performing aeration treatment, and a final sedimentation basin for carrying out precipitation treatment in this order;
A sewage in excess of the design treatment amount of the main treatment path is first supplied from the settling basin, and a sub-treatment path for performing turbidity removal treatment of the excess sewage, and
Sewage treatment in a sewage treatment facility comprising a UV irradiation device capable of controlling the UV irradiation output and performing a sterilization treatment of the treated water treated in the main treatment path or the sub-treatment path, and a chlorine mixing pond for chlorination. A method,
When the inflow sewage does not exceed the design treatment amount of the main treatment path,
The treated water treated in the main treatment path is supplied in the order of the ultraviolet irradiation device and the chlorine-mixing basin to sterilize,
When the inflow sewage exceeds the design treatment amount of the main treatment path,
The amount of the design treatment water in the main treatment path is treated in the main treatment path, and then supplied to the chlorine-mixing basin without being supplied to the ultraviolet irradiation device, and the sterilization treatment is performed for excess sewage. After processing with, supply to the ultraviolet irradiation device to sterilize,
A sewage treatment method characterized by the above. The output of the ultraviolet irradiation device when the inflow sewage does not exceed the design treatment water amount of the main treatment path, and the output lower than the output of the ultraviolet irradiation device when the inflow sewage exceeds the design treatment water amount of the main treatment path. The method of operating a sewage treatment facility according to claim 5, wherein the ultraviolet ray is irradiated. The sewage treatment method according to claim 5 or 6, wherein at least one of a turbidity and a flow rate of treated water supplied to the ultraviolet irradiation device is measured, and an ultraviolet irradiation output of the ultraviolet irradiation device is controlled based on the measured value. The sewage treatment method according to any one of claims 5 to 7, wherein in the sub-treatment path, turbidity removal treatment is performed using at least one of a vortex solid-liquid separator and a filtration device.

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