JP4628132B2 - Method and apparatus for disinfecting waste water - Google Patents

Description

  The present invention relates to a method and apparatus for disinfecting drainage, and more particularly to a method and apparatus for disinfecting sewage diluted with rainwater.

  At the sewage works, the sewage is treated with a sand basin for removing sand, solid-liquid separation treatment for removing suspended solids (SS), activated sludge treatment, and then disinfection. In order, it is discharged into public water such as rivers, lakes, harbors and coastal waters.

  And generally as disinfection, disinfecting with chlorine gas or a chlorine-type disinfectant is common. This is because sewage, human waste, industrial wastewater, and the like may contain pathogenic bacteria that are a source of infectious diseases. In general, a chlorine-based disinfectant is added so that the number of coliforms per ml is 3000 or less. In some cases, ultraviolet irradiation or ozone addition may be performed without adding a chlorine-based disinfectant, but the use is limited because the facilities are enormous.

  The “combined sewer” is a system that collects domestic sewage and industrial wastewater and rainwater in the same pipe and sends them to the sewage treatment plant, and the above-mentioned treatment is performed at the sewage treatment plant. When there is a lot of rainfall, there is a risk that sewage mixed with rainwater that exceeds the amount that can be treated at the sewage treatment plant may flow in, so it is discharged from the sewage drainage facility (rainy weather) such as a rainwater discharge chamber or pump station to the public water area. Is done. Recently, in order to protect the landscape of public water areas such as rivers, a technology to prevent the outflow of oversized garbage, suspended matter, etc. by installing a screen in the sewage drainage facility has begun to be examined. However, the examination about the disinfection technique of coliform bacteria contained in tens of thousands to hundreds of thousands in the effluent discharged from the sewage evacuation facility has not been made.

  On the other hand, “separated sewer” collects domestic sewage and industrial wastewater and rainwater in separate pipes, sends domestic sewage and industrial wastewater to the sewage treatment plant, and discharges rainwater as overflow water. It is a method. Separate sewer overflow should naturally contain only rainwater. However, in reality, when a large amount of rain falls, a large amount of rainwater flows through the sewer, and at this time, pollutants present on the ground such as roads and sludge accumulated in the sewer are also brought together. It will be washed away. Therefore, the separated sewer overflow of sewerage sewer also contains E. coli caused by contaminants and sludge existing on the ground surface. In any case, the number of coliforms in the overflow water may exceed the discharge regulation value (3000 CFU / ml or less), and it is desired to disinfect. Here, CFU means a colony forming unit.

  Chlorine disinfectants have many advantages compared to ultraviolet irradiation and ozone sterilization, such as simple equipment and high applicability to soil conditions.

  However, when the technology applied to normal sewage treatment is diverted to sewage treatment in rainy weather, the following problems arise. First, since ammonia and amine coexist in rainy sewage, a chemical reaction represented by the following formula (1) occurs, the active chlorine changes to chloramine, and the bactericidal effect decreases to 1/10 or less. Therefore, even if the number of pathogenic bacteria does not change, if ammonia or amine is present, it is necessary to increase the addition amount of the chlorine-based disinfectant.

  In addition, since the disinfection time when using a chlorine-based disinfectant is 15 minutes or more (see “Sewerage Facility Planning / Design Guidelines and Explanations”), mix sewage in rainy weather with a chlorine-based disinfectant and stay for 15 minutes or more. A mixing tank is required. However, the sewage drainage facility (when it rains) does not have enough space to install such a mixing tank.

  Therefore, a disinfectant having a short disinfection time and a mixing method thereof are required for sewage treatment in rainy weather.

Researchers from Purdue University and Great Lakes Chemical Company have published in the author's paper: JE Alleman, JE Etzel, DE Gendron, JC Conley, WF McCoy, and AJ Hein, Bromine-Based Disinfection Performance. Reported a laboratory-scale experiment in which chlorinated bromine (BrCl), bromide, Br ₂ , and bromochlorodimethylhydantoin (BCDMH) were added to simulated wastewater containing bacteria such as coliforms. ing. For the simulated waste water, water at pH 7.2 containing low concentration ammonia (2 mg / L) or water at pH 8.2 containing high concentration ammonia (20 mg / L) is used. As bacteria, Escherichia coli, Pseudomonas, Streptococcus faccalis are used. However, it does not describe that the simulated waste water contains organic substances.

  Japanese Patent Application Laid-Open No. 4-156994 describes a method of injecting a bactericide into cooling water. As a disinfectant, it is described that hypobromite ions are generated by an oxidation-reduction reaction between ozone and bromine ions. However, the cooling water does not contain ammonia.

  Japanese Patent Application Laid-Open No. 11-47755 discloses a slime control agent and method containing a hydantoin compound as an active ingredient. A slime control agent is used for water used in pulp and paper mills.

  In one aspect of the present invention, HOX (wherein X is a bromine atom or an iodine atom) can be generated, and a disinfectant containing a bromine atom or an iodine atom is mixed with water to disinfect the disinfecting water. There is provided a method for disinfecting waste water, comprising the steps of: obtaining and disinfecting the disinfecting water by adding the disinfecting water to waste water containing organic matter and ammonia or ammonium ions.

  In this invention, it is preferable that the total organic carbon (total organic carbon) in the said waste_water | drain is 5 mg / l or more. The ammonium ion concentration in the waste water is preferably 1 mg / l or more.

  The drainage preferably contains rainwater. The waste water preferably contains sewage diluted with rain water.

  Moreover, it is preferable that the said disinfectant contains the 4-10 membered heterocyclic ring containing the hetero atom which consists of a nitrogen atom or a sulfur atom which may be condensed with another ring, 1-4. Further, the heterocyclic ring preferably contains a group represented by the formula —N (X) —C (═O) — (wherein X contains a bromine atom or an iodine atom) in the ring skeleton. Furthermore, it is preferable that the disinfectant is solid and the step of obtaining disinfecting water includes a step of dissolving the disinfectant in the waste water.

  The concentration of the disinfectant in the disinfecting water is preferably 100 mg / l as Cl to 10 g / l as Cl in terms of active chlorine concentration.

  It is preferable that the addition concentration of the disinfectant in the waste water is 0.5 mg / l as Cl to 25 mg / l as Cl in terms of active chlorine concentration.

  It is preferable that the adding step includes a step of introducing the disinfecting water below the surface of the waste water. Furthermore, it is preferable to further include a step of discharging the sterilized waste water to public water bodies.

In another aspect of the present invention, an apparatus for producing disinfecting water from a disinfectant and waste water;
A sand basin for removing sand in drainage,
A first flow path for introducing the disinfecting water into the sand basin;
There is provided an apparatus for disinfecting wastewater, wherein the wastewater is disinfected while staying in the sand basin.

  In the present invention, the disinfecting water production apparatus preferably includes a disinfectant storage device, a device for adding the disinfectant to the waste water, and a device for mixing the disinfectant and the waste water. Moreover, it is preferable that the said sand settling basin has two or more sand settling parts, and the said 1st flow path has a distribution tank for introduce | transducing disinfection water into each sand settling part.

  It is preferable that the first flow path is connected to an adding device for introducing the disinfecting water below the surface of the waste water.

  It is preferable to further include a reservoir or discharge channel for storing the sterilized waste water so that it can be discharged to public water bodies.

  It is preferable that a measuring instrument for inspecting the water quality of the sterilized waste water is provided in the reservoir or the discharge water channel.

  It is preferable to further have a second flow path for introducing a part of the waste water in the sand basin to the disinfecting water production apparatus.

  It is preferable that the disinfectant can generate HOX (wherein X is a bromine atom or an iodine atom) and contains a bromine atom or an iodine atom.

  The disinfectant preferably contains a 4- to 10-membered heterocycle containing 1 to 4 heteroatoms composed of a nitrogen atom or a sulfur atom, which may be condensed with other rings.

BEST MODE FOR CARRYING OUT THE INVENTION

  In one aspect of the present invention, waste water containing organic matter and ammonia or ammonium ions is disinfected.

  For example, in a combined sewer, raw sewage and rainwater are mixed and flow through the sewer. And the rainy day sewage which mixed both in this way, especially the rainy day sewage which has not yet been processed in a sewage treatment plant, is disinfected by the method of this invention.

  In the sewer type sewer system, the sewer system of the raw sewage and the sewer system of the rainwater are separated, and the sewage in rainy weather flowing through the sewer for rainwater is disinfected by the method of the present invention.

  As the content of organic matter in the wastewater, for example, in this wastewater, the total organic carbon may be 5 mg / l or more, 10 mg / l or more, and 30 mg / l. The above may be sufficient and 50 mg / l or more may be sufficient. Whether combined sewage or split sewage, generally the total organic carbon is 5 mg / l or more.

The ammonium ion concentration in the wastewater may be 1 mg / l or more, or 10 mg / l or more. When ammonium ion is contained in the waste water, the active bromine or active iodine changes to NH ₂ X, NHX ₂ or the like (wherein X means a bromine atom or an iodine atom). However, in the case of bromoamine (NH ₂ Br), the disinfection effect comparable to that of hypobromite is maintained, so that it can be effectively disinfected. In combined sewage, the ammonia ion concentration is generally 1 mg / l or more. In the case of diversion sewage, in the overflow water called first flush immediately after rainfall, the ammonia ion concentration is often 1 mg / l or more.

  In one aspect of the present invention, the drainage is mainly intended for sewage diluted with rainwater, but it may also be targeted for rainwater produced by a shunt sewer. Furthermore, water containing organic matter and ammonia or amine, such as sewage, human waste, industrial wastewater, or treated water thereof, may be treated by the method of the present invention.

  In one aspect of the present invention, the water to be treated contains E. coli. This is because it is particularly necessary to disinfect such water. The combined sewage generally contains E. coli. Also, diversion rainwater often contains E. coli.

  In one aspect of the present invention, a disinfectant that can generate HOX (wherein X is a bromine atom or an iodine atom) and contains a bromine atom or an iodine atom is used. Disinfectants that can produce acid (HOBr) and contain bromine atoms are used. Compared with the chlorine-based disinfectant, the bromine-based disinfectant or the iodine-based disinfectant is characterized by a shorter disinfection time. For example, bromine-based disinfectants can be sterilized for tens of seconds to several minutes. Moreover, since hypohalous acid (HOX, where X is a bromine atom or an iodine atom) is easily decomposed in nature, it is necessary to provide an apparatus for decomposing the hypohalous acid remaining in the waste water. Absent. On the other hand, with chlorine-based disinfectants, active chlorine reacts with ammonia in sewage to form chloramine and reduce sterilizing power. Have difficulty. Moreover, since the persistence of chloramine is high, it is necessary to provide an apparatus for the decomposition treatment.

  Examples of the disinfectant preferably used in the present invention include hydantoins, cyanuric acids, isothiazolones, ε-caprolactams, phthalimides, pyrrolidones, acridones, uracils, succinimides, barbituric acids, creatinines, Examples include dioxopiperazines, urazoles, glycine anhydrides, ω-heptalactams, maleic hydrazides, maleic imides, octalactams, and oxindoles.

  Hydantoins are represented by, for example, formula (II).

In the formula, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom or an iodine atom, provided that either X ¹ or X ² is a bromine atom or an iodine atom. Yes;
R ¹ and R ² are the same or different and are each independently a hydrogen atom or a lower alkyl group having 10 or less carbon atoms, preferably a hydrogen atom or a lower alkyl group having 6 or less carbon atoms, Preferably, it is a hydrogen atom or a lower alkyl group having 3 or less carbon atoms.

  Examples of the hydantoins include 1-bromo-3-chloro-5,5-dimethylhydantoin (a compound represented by the formula (I)). Bromochlorodimethylhydantoin has high stability and can maintain activity for several years if it avoids direct sunlight. BCDMH is a solid, and when dissociated, hypobromite ions are generated and exhibits a high disinfection effect.

  Cyanuric acids are represented, for example, by the formula (III).

In the formula, R ¹ , R ² and R ³ are the same or different and are each independently a chlorine atom, bromine atom, iodine atom, hydroxyl group, hydrogen atom or lower alkyl group having 10 or less carbon atoms, provided that , R ¹ , R ² and R ³ are a bromine atom or an iodine atom. The lower alkyl group preferably has 6 or less carbon atoms, more preferably 3 or less carbon atoms.

  Isothiazolons are represented, for example, by the formula (IV).

In which X is a bromine atom or an iodine atom;
R ¹ and R ² are the same or different and are each independently a chlorine atom, a bromine atom, an iodine atom, a hydrogen atom, or a lower alkyl group having 10 or less carbon atoms. The lower alkyl group preferably has 6 or less carbon atoms, more preferably 3 or less carbon atoms.

  For example, 5-chloro-2-methyl-4-isothiazolin-3-one is preferred.

  ε-caprolactams are represented by, for example, formula (V). In the formula, X is a bromine atom or an iodine atom.

  Phthalimides (phtalimides) are represented, for example, by the formula (VI). In the formula, X is a bromine atom or an iodine atom.

  The pyrrolidones are represented by, for example, formula (VII). In the formula, X is a bromine atom or an iodine atom.

  Acridones are represented, for example, by formula (VIII). In the formula, X is a bromine atom or an iodine atom.

  Uracils are represented, for example, by the formula (IX).

In the formula, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom or an iodine atom, provided that either X ¹ or X ² is a bromine atom or an iodine atom. Yes;
R ¹ is a hydrogen atom, a lower alkyl group having 10 or less carbon atoms, an amino group, or a nitro group. The lower alkyl group preferably has 6 or less carbon atoms, more preferably 3 or less carbon atoms.

R ² and R ³ are the same or different and are each independently a hydrogen atom or a lower alkyl group having 10 or less carbon atoms, preferably a hydrogen atom or a lower alkyl group having 6 or less carbon atoms, Preferably, it is a hydrogen atom or a lower alkyl group having 3 or less carbon atoms.

  Succinimides are represented, for example, by the formula (X). In the formula, X is a bromine atom or an iodine atom.

  Barbituric acids are represented, for example, by the formula (XI).

In the formula, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom or an iodine atom, provided that either X ¹ or X ² is a bromine atom or an iodine atom. Yes;
R ¹ and R ² are the same or different and are each independently a hydrogen atom or a lower alkyl group having 10 or less carbon atoms, preferably a hydrogen atom or a lower alkyl group having 6 or less carbon atoms, Preferably, it is a hydrogen atom or a lower alkyl group having 3 or less carbon atoms.

  The creatinines are represented by, for example, the formula (XII).

In which X is a bromine atom or an iodine atom;
R is a hydrogen atom or a lower alkyl group having 10 or less carbon atoms, preferably a hydrogen atom or a lower alkyl group having 6 or less carbon atoms, more preferably a hydrogen atom or a lower alkyl group having 3 or less carbon atoms. is there.

  Dioxopiperazines (dioxopiperazines) are represented by, for example, formula (XIII).

In the formula, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom or an iodine atom, provided that either X ¹ or X ² is a bromine atom or an iodine atom. is there.

  Urazoles are represented by, for example, formula (XIV).

In the formula, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom or an iodine atom, provided that either X ¹ or X ² is a bromine atom or an iodine atom. Yes;
R ¹ , R ² and R ³ are the same or different and are each independently a chlorine atom, a bromine atom, an iodine atom, a hydrogen atom or a lower alkyl group having 10 or less carbon atoms, and R ¹ , R ² and Any of R ³ is a bromine atom or an iodine atom. The lower alkyl group preferably has 6 or less carbon atoms, and more preferably 3 or less carbon atoms.

  Glycine anhydrides are represented, for example, by the formula (XV).

In the formula, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom, an iodine atom, a hydrogen atom, or a lower alkyl group having 10 or less carbon atoms, and X ¹ and X ² Either is a bromine atom or an iodine atom. The lower alkyl group preferably has 6 or less carbon atoms, and more preferably 3 or less carbon atoms.

  The ω-heptalactams are represented by, for example, the formula (XVI). In the formula, X is a bromine atom or an iodine atom.

  Maleic hydrazides are represented by, for example, formula (XVII).

In the formula, X ¹ and X ² are the same or different and are each independently a chlorine atom, a bromine atom or an iodine atom, provided that either X ¹ or X ² is a bromine atom or an iodine atom. is there.

  Maleic imides (maleimides) are represented by, for example, formula (XVIII). In the formula, X is a bromine atom or an iodine atom.

  Octalactams are represented, for example, by the formula (XIX). In the formula, X is a bromine atom or an iodine atom.

  Oxindoles are represented, for example, by the formula (XX). In the formula, X is a bromine atom or an iodine atom.

  The disinfectant that can be used in the present invention preferably contains a 4 to 10 membered heterocyclic ring containing a nitrogen atom or a sulfur atom, as shown in the above formulas (I) to (XX), and 5 to 9 membered. More preferably, it includes a heterocycle. The heterocycle preferably contains 1 to 4 heteroatoms, more preferably 1 to 3 heteroatoms. A hetero atom is a nitrogen atom or a sulfur atom.

  In the heterocyclic ring skeleton, a group represented by the formula -N (X)-(X is a chlorine atom, a bromine atom or an iodine atom, preferably a bromine atom or an iodine atom, more preferably a bromine atom. It is preferably an atom.

  As shown by the formula (XXI), the ring skeleton of the heterocyclic ring A has a group represented by the formula —N (X) —C (═O) — (wherein X contains a bromine atom or an iodine atom). More preferably, This is because hypohalous acid is particularly easily generated in this structure.

  The heterocycle may be condensed with another ring, for example, an aromatic ring such as a benzene ring, as shown by the above formulas (VI), (VIII) and (XX).

  One aspect of the present invention includes a step of mixing a predetermined disinfectant with water. In the present invention, a disinfectant may be added to the wastewater at a sewage drainage facility (when it rains). For example, it may be added at the sewage pipe that flows into the sewage drainage facility (when it rains), or it may be added at the sinking basin, especially at the inlet of the basin, or at the rainwater drainage pump well. Alternatively, it may be added in the rainwater drain pump inflow pipe. That is, any of these may be used, and the addition is not limited to one place but can be added in several places.

  Alternatively, a main flow path through which drainage flows and a bypass flow path branched from the main flow path may be provided in a sewage drainage facility (when raining), and a disinfection tank may be installed in the bypass flow path. In this disinfection tank, a disinfectant may be added to the waste water, and the disinfectant may be dissolved in the waste water.

  If the place where the disinfectant is added is the inflow side of the rainwater draining pump, it is preferable because the disinfectant and the sewage in the rain are sufficiently mixed by the stirring force in the pump. Further, it is preferable to add a disinfectant at the inflow portion of the sand basin because the residence time in the sand basin can be used for the reaction time.

  The disinfectant used in the present invention is often a solid at room temperature. When a solid disinfectant is added directly to the wastewater, undissolved solids are released along with the wastewater and there is a risk of adversely affecting aquatic organisms in public waters. Therefore, when the disinfectant is solid, it is preferable to dissolve the disinfectant in water to make disinfectant water and add it to the waste water. The dissolution method is not particularly limited, and any of a water flow stirring by an ejector, a flow path stirring, and a dissolution tank provided with a mixing device may be used.

  For example, disinfecting water in which 1% by weight or more, preferably 10% by weight or more, more preferably 20% by weight or more of the disinfectant is dissolved with respect to the saturated dissolution concentration of the disinfectant may be used. However, even when the disinfectant is solid, it is not necessary to dissolve all of the added disinfectant in water, and the solid disinfectant may remain in the disinfecting water.

  On the other hand, even when the disinfectant is a liquid at room temperature, when a small amount of liquid is added to a large amount of waste water, it takes some time to mix the two, and it does not necessarily mix uniformly. Therefore, it is preferable to add the disinfectant to the water and then add it to the waste water.

  The concentration of the disinfecting water is preferably 100 mg / l as Cl to 10 g / l as Cl, more preferably 200 mg / l as Cl to 2 g / l as Cl in terms of active chlorine concentration. When the concentration of the disinfecting water is smaller than 100 mg / l as Cl, not only the amount of disinfecting water is increased, but also the disinfectant may be consumed by the diluted water. is there. On the other hand, when the concentration of the disinfecting water is higher than 10 g / l as Cl, mixing of the disinfectant and the waste water becomes insufficient, and the disinfecting effect is reduced.

  The amount of disinfecting water added depends on the concentration of the disinfectant in the disinfecting water, the amount of rainfall, the quality of the drainage water, etc., and generally the amount of disinfecting water added corresponds to the increase in the amount of rainfall, that is, the amount of drainage and water quality. To increase. However, in one embodiment of the present invention, the increase in rainwater reduces the pollution of incoming water quality. Therefore, in one embodiment of the present invention, even if rainwater increases and the inflow water amount triples, it is not necessary to triple the amount of disinfecting water or disinfectant added. Therefore, it is reasonable to find the optimum addition amount in the influent water quality by a beaker test or the like in advance and determine the addition amount of the disinfecting water or the disinfectant by multiplying the value by the inflow water amount.

  Regarding inflow water quality, it is possible to grasp the mixed state of rainwater by measuring turbidity or electrical conductivity. With this index, on-time detection is possible. In addition to these indicators, rainfall patterns, particle properties in sewage during rainy weather, SS content, chemical oxygen demand (COD, Chemical Oxygen Demand), biological oxygen demand (BOD, Biological Oxygen Demand), etc. These indices can be used in any combination. In addition, various flow meters may be used for the inflow water amount, but it may be determined from the number of operating rainwater pumps and the load status.

  Next, the disinfecting water is added to a predetermined drainage to disinfect. For example, the disinfecting water in the disinfecting water tank is introduced into the main channel via the bypass channel.

  When the wastewater is sewage, human waste, industrial wastewater, or the like, the concentration of the disinfectant in the wastewater is usually 0.5 to 25 mg / l as Cl in terms of active chlorine concentration. Preferably, it is 1-15 mg / l as Cl. The added concentration of the disinfectant can be calculated from the concentration and amount of the disinfectant in the disinfecting water and the amount of waste water. The addition concentration of the disinfectant is a value before the disinfectant is consumed in the waste water.

When treated water is sewage, urine, industrial wastewater, etc., these treated waters generally contain coliforms in the range of 10 ⁴ to 10 ⁷ CFU / mL, but depending on the addition amount of the disinfectant. In general, the water to be treated can be sterilized quickly and reliably in about 1 minute.

  FIG. 1 is a schematic explanatory view illustrating an embodiment of the method of the present invention.

  Sewage in rainy weather flows into the sand basin 10 from the main channel. And in the sand basin 10, the inflow part 12 and the sand settling part 14a, 14b, 14c arrange | positioned in parallel with each other are contained. The sewage in rainy weather can flow from the inflow part 12 into the sand settling parts 14a, 14b, 14c.

  An exclusion pump 16 is disposed at the exit of the settling basin 10, and the exclusion pump 16 moves the sterilized rainy sewage to the discharge channel 17. Next, the rainwater in the discharge channel 17 is measured by a measuring instrument 18 such as a residual halogen detector, a turbidimeter, and an electric conductivity meter. The residual halogen detector measures the residual concentration of active halogen such as hypobromous acid. Thus, it is preferable that the residual halogen detector is normally disposed between the sand basin outlet and the discharge outlet.

When the active halogen concentration detected by the residual halogen detector is LC ₅₀ value (for example, in the case of BCDMH, 0.4 mg / l in terms of active chlorine (Cl ₂ )) or more, it becomes LC ₅₀ value or less. Thus, when the LC ₅₀ value is desirably 1/2 or more (for example, 0.2 mg / l in terms of active chlorine (Cl ₂ ) in the case of BCDMH), the LC ₅₀ value is desirably 1/2 or less. Reduce the supply of disinfectant or disinfecting water or temporarily shut off. As a result, adverse effects on aquatic organisms in public waters can be reduced.

  Then, after confirming that these measured values and the number of coliforms meet a predetermined discharge standard, they are discharged into public water areas such as rivers.

  Public water includes rivers, lakes, harbors, coastal waters, public trenches, irrigation canals, and other public waters or canals. However, the public water area does not include sewers, particularly sewers having downstream treatment plants.

  In the embodiment of FIG. 1, a bypass flow path 20 is connected to the inflow portion 12 of the sand basin 10. Part of the sewage in rainy weather that has flowed into the inflow portion 12 of the sand basin 10 is introduced into the bypass channel 20. Then, a disinfectant is added to the sewage during rainy weather, converted into disinfecting water, and returned to the sand basin 10 again.

  A pumping pump 13 is disposed in the inflow portion 12 of the sand basin 10. A part of the sewage in the rain 12 in the inflow portion 12 is pumped up to the bypass channel 20 by the pumping pump 13. On the other hand, the other part of the sewage in the rain of the inflow part 12 flows into the sand settling parts 14a, 14b, 14c.

  In the bypass channel 20, a pair of automatic screens 22 a and 22 b, a flow meter 23, a disinfectant addition device 30, a dissolution device 40, a pump 46 and a distribution tank 48 are arranged in this order. The automatic screens 22a and 22b are arranged in parallel with each other.

  The disinfectant addition device 30 includes a hopper 32 for storing the disinfectant 39, a supply unit 34 for supplying the disinfectant 39, and an ejector 36 for discharging the disinfectant into the flow path.

  The rainy sewage to which the disinfectant is added is guided to the device 40. When the disinfectant is solid, the device 40 dissolves the disinfectant in sewage during rainy weather. When the disinfectant is liquid, the disinfectant is mixed with sewage in rainy weather. The apparatus 40 has a tank 41. In the embodiment of FIG. 1, the tank 41 is divided into a stirring tank 41a and a storage tank 41b. However, it is not necessary to divide into two tanks in this way.

  The stirring tank 41a is provided with a water level gauge 42 and a stirrer 44 for stirring the waste water. The stirrer 44 includes, for example, a motor 44a, a shaft 44b connected to the motor 44a, and a stirring tool 44c such as a blade and an impeller fixed to the shaft. The waste water in the stirring tank 41a is stirred by the stirrer 44, and the solid disinfectant in the waste water can be dissolved. The waste water overflowed in the storage tank 41a is transferred to the storage tank 41b.

  When the solubility of the solid disinfectant is small, it is preferable to provide a dissolving device 40. On the other hand, when the solubility of the solid disinfectant is high, the disinfectant is quickly dissolved in the flow path, and thus a dissolution apparatus is not necessarily required.

  The disinfecting water obtained by the apparatus 40 is preferably guided to the sand basin 10 by the pump 46 through the flow path 47. As shown in FIG. 1, the disinfecting water may be guided directly to the sand basin 10 or may be guided to the sand basin 10 via the distribution tank 48 as shown in FIG. 2.

  That is, in FIG. 2, the distribution tank 48 is provided in the flow path 47. In FIG. 2, for the convenience of explanation, the sand settling portions 14 a, 14 b, and 14 c of the sand settling basin 10 are illustrated, and the inflow portion 12 is omitted.

  As shown in FIG. 1, the disinfecting water may be guided to the inflow portion 12 of the sand basin 10, or as shown in FIG. 2, upstream of each of the sand settling portions 14 a, 14 b, 14 c of the sand basin 10. May be introduced.

  As shown in FIG. 2, when disinfecting water is introduced upstream of each of the sand settling portions 14 a, 14 b, 14 c of the sand basin 10, the disinfecting water is supplied to the sand settling portions 14 a, 14 b, 14 c in the distribution tank 48. It is preferable to preliminarily distribute the disinfecting water led to each of the above.

  In the sand settling portions 14a, 14b, and 14c, the sand contained in the sewage during raining is settled and removed. At the same time, the sewage in rainy weather and the disinfecting water are mixed to disinfect the sewage in the rainy weather. In the sand settling portions 14a, 14b, and 14c, the sewage and disinfecting water in the rain preferably stay for 1 second to 30 minutes, more preferably 1 second to 15 minutes, and still more preferably 1 second to 10 minutes. Stay.

  FIG. 3 shows an embodiment of an adding apparatus for adding disinfecting water to the sand settling part. The addition device 50 has a pipe 52 extending in the horizontal direction and an introduction section that communicates with the pipe 52 and introduces disinfecting water into the waste water. The pipe 52 communicates with the flow path 49a and is supported by a support body (not shown). One embodiment of the introduction part is, for example, a plurality of hoses 54 suspended from the pipe 52. The open end 56 of the hose is preferably located upstream of the sand settling portion 14a and below the water surface. The disinfecting water distributed from the distribution tank 48 flows through the flow path 49a, the pipe 52, and the hose 54 in this order, and is added to the drainage 15 in the sand settling part 14a.

  When the open end 56 of the hose 54 is positioned on the water surface of the drainage 15 of the sand settling portion 14a, the disinfecting water splash from the open end 56 of the hose forms a mist due to wind or the like. Risk of corroding electrical equipment. The open end 56 of the hose is preferably disposed below the surface of the drainage 15 of the sand settling portions 14a, 14b, 14c.

  The tube 52 is preferably made of a material that is not corroded by disinfecting water. For example, a metal material such as Inconel, or a plastic material such as polytetrafluoroethylene or polyvinyl chloride can be used. The tube 52 preferably has sufficient mechanical strength to support the hose. It is preferably rigid, but may be flexible.

  For example, 2 to 20 hoses, preferably 2 to 10 hoses, and more preferably 2 to 6 hoses may be hung on each pipe 52. The interval between two adjacent hoses is preferably constant. This is because disinfecting water can be efficiently mixed with waste water. But the space | interval between two adjacent hoses may differ. The hose 54 is preferably flexible, but may be rigid.

Examples of the present invention will be described below, but the present invention is not limited thereto. In the following examples, wastewater was treated by the system shown in FIGS.
Example 1
A sterilization test was conducted using treated sewage water containing coliforms as treated water. As the disinfectant, 1-bromo-3-chloro-5,5-dimethylhydantoin (hereinafter referred to as BCDMH) (Example 1) and sodium hypochlorite (Comparative Example 1) were used. Bactericidal tests against coliforms were performed with varying concentrations of disinfectant. Table 1 shows the quality of water to be treated and Table 2 shows the test results.

  BCDMH exhibited a bactericidal effect at a concentration of 1/2 or less compared to sodium hypochlorite, and the number of coliforms could be reduced to 3000 CFU / mL or less at an addition concentration of 1 mg / L as Cl.

  Trihalomethane was 0.1 mg / L or less under the condition that BCDMH was added at lmg / L as Cl.

  In this specification, the addition rate of the disinfectant is indicated as active chlorine for both the bromine-based disinfectant and the chlorine-based disinfectant, and expressed as “mg / L as Cl” in terms of the active chlorine concentration. For example, when 1 g of BCDMH is added to 1 liter of waste water, it becomes 540 mg / L as Cl.

As for the reaction time, a sufficient effect was recognized in 1 minute with BCDMH, whereas a time of 5 minutes or more was required with sodium hypochlorite.
Example 2
After the aquatic processing wastewater was separated by flocculation, pressurization and floatation, wastewater obtained by activated sludge treatment was used as water to be treated. The disinfection agent addition density | concentration was changed with respect to this to-be-processed water, and the sterilization test was done. Table 3 shows the quality of water to be treated and Table 4 shows the test results.

  Organic nitrogen refers to the value of organic nitrogen as a whole, such as proteins, in addition to amines. For example, in the case of protein, it refers to the amount of only nitrogen atoms in the protein, and does not include the amount of carbon atoms or hydrogen atoms in the protein. Organic nitrogen does not include inorganic nitrogen such as ammonia and ammonium ions.

BCDMH produced a bactericidal effect at a concentration of 1/3 or less compared to that of sodium chlorate, and was able to reduce the number of coliforms to 3000 CFU / mL or less at an addition concentration of 2.5 mg / L as Cl.
Example 3
Wastewater was treated with the system shown in FIGS. The results are summarized in Table 5.

  * 1 A indicates BCDMH (effective halogen concentration 54%). B represents sodium hypochlorite (effective halogen concentration 10%).

* 2 Addition amount in terms of chlorine (Cl ₂ ) [mg / l].

  * 3 ND means not detected.

With RUN1 (sewage amount 120 m ³ / hour), the number of coliforms can be reduced to 3000 CFU / ml or less with a BCDMH addition amount of 12 mg / l.

With RUN2 (sewage amount 250 m ³ / hour), a BCDMH addition amount of 10 mg / l is sufficient, but the residual halogen concentration is 0.72 mg / l, which is not appropriate. With the addition amount of BCDMH of 5 mg / l, the number of coliforms can be reduced to 3000 CFU / ml or less, and the residual halogen concentration is 0.03 mg / l, which is appropriate.

RUN3 (sewage amount 530 m ³ / hour) is a case where the amount of rainfall is large, and proper disinfection was possible with a BCDMH addition amount of 3 to 4.5 mg / l. In addition, when the time which BCDMH at this time contacted rainwater exclusion sewage was calculated | required, it was about 50 second and it was able to disinfect in a very short time.

RUN4 (sewer 250 m ³ / hour) is a comparative example using sodium hypochlorite as a chlorine disinfectant. In RUN4, even if the amount of sodium hypochlorite added is 60 mg / l, the number of coliforms cannot be reduced to 3000 CFU / ml or less, and the residual halogen concentration is 1.53 mg / l and LC ₅₀ value (specifically, Is higher than 0.4 mg / l) in terms of chlorine (Cl ₂ ) and is inappropriate.

In any case of RUN1 to RUN4, the case where the disinfectant addition amount is 0 (zero) indicates the quality of the inflowing sewage that has flowed into the rainwater removal treatment plant.
〔The invention's effect〕

In the present invention, wastewater such as sewage in rainy weather can be sterilized efficiently. Further, disinfection can be achieved even if the residual halogen concentration is 0.4 mg / l or less of LC ₅₀ value or less. Further, by detecting the residual halogen concentration, when the control value of the residual halogen concentration is exceeded, the supply amount of the disinfectant or disinfecting water can be reduced or shut off, and environmental considerations can be made.

FIG. 1 is an explanatory diagram of one embodiment of the apparatus of the present invention. FIG. 2 is an explanatory view of a part of another embodiment of the apparatus of the present invention. FIG. 3 is a cross-sectional view of one embodiment of an apparatus that can be used in the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Sand settling basin, 12 ... Inflow part, 14a, 14b, 14c ... Sand settling part, 16 ... Exclusion pump, 17 ... Discharge water channel, 18 ... Measuring instrument, 20 ... Bypass flow path, 22a, 22b ... Automatic screen, 23 ... Flow rate 30 ... Disinfectant addition device, 32 ... Hopper, 34 ... Feeder, 36 ... Ejector, 39 ... Disinfectant, 40 ... Dissolution device, 41 ... Tank, 41a ... Stirrer tank 41a, 41b ... Storage tank, 42 ... Water level 44 ... Stirrer, 46 ... Pump, 47 ... Flow path, 48 ... Distribution tank, 49a ... Flow path, 50 ... Addition device, 52 ... Pipe, 54 ... Hose, 56 ... Open end

Claims (7)

  A method for disinfecting sewage in rainy weather which flows through a sewer for sewerage in a sewerage sewer system in rainy weather and which is discharged into public water areas, comprising organic matter, ammonia or ammonium ions and rainwater, and comprising 1-bromo-3-chloro-5 A process comprising: adding and dissolving a solid disinfectant comprising 5,5-dimethylhydantoin in water to obtain disinfecting water; and adding the disinfecting water to the sewage to disinfect.   The method according to claim 1, wherein the concentration of the disinfectant added to the sewage is 0.5 mg / L as Cl to 25 mg / L as Cl in terms of active chlorine concentration.   The method according to claim 1 or 2, wherein the disinfecting water is obtained by adding the disinfectant to the sewage.   The method according to any one of claims 1 to 3, wherein the step of adding the disinfecting water to the sewage and disinfecting includes introducing the disinfecting water below the surface of the sewage.   An apparatus for disinfecting sewage in rainy weather, which contains organic matter, ammonia or ammonium ions, and rainwater, flows through a sewer for sewerage in a sewerage sewerage system in rainy weather and is discharged to public waters, and is 1-bromo-3-chloro-5 , 5-dimethylhydantoin-containing disinfectant storage device for storing a disinfectant storage device, disinfecting water production device comprising a dissolving device for adding and dissolving the solid disinfectant in water, and the manufactured disinfecting water is added to the sewage A device comprising:   The apparatus according to claim 5, wherein the disinfecting water production apparatus includes a line for supplying the sewage to the dissolving apparatus, and the solid disinfectant is added to and dissolved in the sewage. A device for adding the disinfecting water to the sewage is installed in any one or more of a sewer pipe that flows into the rainwater sewer of a diversion sewer, an inflow portion of a sand basin, a rainwater drain pump well, and a rainwater drain pump inflow pipe. The apparatus according to claim 5 or 6.

Images