JP3360608B2 - Cleaning method for water treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for cleaning a water treatment apparatus. More specifically, the present invention provides a water treatment apparatus for reducing impurities in water by passing water through a packed bed of iron metal particles, and effectively prevents the filled iron metal particles from forming block-like lumps. The present invention relates to a method of cleaning a water treatment apparatus that can perform the treatment.

[0002]

2. Description of the Related Art Wastewater discharged from a desulfurization device for exhaust gas generated when coal or oil is burned includes heavy metals,
Since it contains various harmful substances such as nonmetals, it is necessary to remove these harmful substances from wastewater. If the wastewater contains peroxosulfuric acid, iodic acid, selenic acid, nitric acid, etc., adjust the pH of the wastewater containing these harmful substances to 5 or less and bring it into contact with iron metal, then coagulate and solid-liquid By performing the separation, peroxosulfuric acid, iodic acid, selenic acid, nitric acid and the like in the wastewater are reduced by the divalent iron ions eluted, and the iron ions dissolved in the water due to the coagulation treatment are removed from the water-insoluble water. When precipitated as iron oxide, harmful substances such as heavy metals and fluorine are also efficiently removed at the same time. As a method of bringing wastewater into contact with ferrous metal,
There are known a stirring contact method in which iron metal fine particles are added to wastewater in a reaction tank and stirring, and a water contact method in which wastewater is passed through a packed bed of iron metal particles. The stirring contact method does not require a washing operation of the packed bed, but the reduction reaction is not sufficient, the removal of harmful substances in the wastewater is inferior to the water contact method, and the addition amount of iron metal fine particles, There are many problems in operation management such as controlling the stirring intensity for uniformly dispersing the iron metal fine particles and preventing the dispersed iron metal fine particles from flowing out. On the other hand, the water contact method of passing water through the packed bed of iron metal particles is as follows:
Operation management is relatively easy, and harmful substances in wastewater are efficiently removed at the beginning of water passage.However, if water continues to flow for a long time, pollutants may adhere to the surface of iron metal particles or clogging may occur. And the efficiency of wastewater treatment is reduced. The present inventors have previously disclosed in Japanese Patent Application Laid-Open No. 9-323090 that contaminants attached to the surface of iron metal particles can be easily peeled and removed, and harmful substances in wastewater can be stably removed. As a washing method of the water treatment apparatus, after washing water is passed through the packed bed and washed, a mixed flow of washing water and air is further supplied in an upward flow to remove contaminants in the packed bed of iron metal particles. A cleaning method for water treatment equipment was proposed. By this method, the wastewater treatment can be performed stably, but depending on the quality of the wastewater, such as when the wastewater contains a high concentration of nitrate nitrogen, the iron metal particles in the packed bed are blocked during the treatment. A phenomenon of forming a lumpy mass occurred. When the iron metal particles form a block-like mass, the contact with the wastewater becomes insufficient, so that the wastewater is not effectively used for wastewater treatment, and further, there is a problem that the iron metal particle remains in the packed bed as an iron mass. Since the block-like lump of iron metal particles cannot be loosened by a normal washing method, the water treatment device which does not form the block-like lump in the packed bed and is easy to operate and manage. There has been a demand for a cleaning method.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a water treatment apparatus for reducing impurities in wastewater by passing water through a packed bed of iron metal particles. An object of the present invention is to provide a method for cleaning a water treatment apparatus, in which particles do not form block-like lumps and operation management is easy.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor dissolves the packed bed of iron metal particles by passing air through the packed bed, and then mixes washing water with air. By performing the operation of supplying the gas in an upward flow twice or more a day, the iron metal particles are loosened before forming the block-like mass, and the block-like mass of the iron metal particle is not formed. And completed the present invention on the basis of this finding. That is, the present invention provides: (1) a water treatment apparatus for reducing impurities in wastewater by passing water through a packed bed of iron metal particles; After loosening the packed bed of iron metal particles through air for 1 second to 1 minute, washing is performed for 1 day to remove contaminants from the packed bed of iron metal particles by supplying a mixed flow of washing water and air in an upward flow. (2) a method of cleaning a water treatment apparatus, wherein the cleaning is performed twice or more times; (2) cleaning is performed using a mixed flow of cleaning water and air, and then cleaning is performed using only cleaning water. 3. The method for cleaning a water treatment device according to item 1, and (3) the water treatment according to item 1 or 2, wherein the wastewater is adjusted to be acidic and water is passed through a packed bed of iron metal particles. A method of cleaning the apparatus. Further, as a preferred embodiment of the present invention, (4) the method for cleaning a water treatment apparatus according to item 1, wherein the pH of the wastewater is adjusted to 5 or less; (5) in the supply of a mixed flow of the cleaning water and the air, 2. The method for cleaning a water treatment apparatus according to claim 1, wherein the supply speed is LV = 30 to 150 m / h. (6) In the supply of a mixed flow of cleaning water and air, the supply speed of air is LV = 50 to 200 m. / H, the method for cleaning a water treatment apparatus according to item 1, wherein the supply of a mixed flow of cleaning water and air is performed for 30 seconds to 5 minutes. Can be mentioned.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention can be used for washing a water treatment apparatus for passing wastewater through a packed bed of iron metal particles to reduce impurities in the wastewater. Acid wastewater,
When the pH is preferably adjusted to 5 or less and brought into contact with iron metal, divalent iron ions elute from the iron metal into water according to the following formula. Fe + 2H ⁺ → Fe ²⁺ + H ₂ Peroxosulfuric acid, iodic acid, selenic acid and nitric acid contained in the waste water react with divalent iron ions according to the following formulas, respectively, and are reduced. S ₂ O ₈ ^2- + 2Fe ²⁺ → 2SO ₄ ^2- + 2Fe ³⁺ 2IO ₃ ⁻ + 10Fe ²⁺ + 12H ⁺ → I ₂ + 10Fe ³⁺ +
6H ₂ O SeO ₄ ^2- + 6Fe ²⁺ + 8H ⁺ → Se ⁰ + 6Fe ³⁺ +4
H ₂ O NO ₃ ⁻ + 4Fe ²⁺ + 6H ⁺ → NH ₄ ⁺ + 4Fe ³⁺ + O ₂ +
H ₂ O In addition, if the redox potential of -400 to-100 mV, the reaction of ferrous metals and selenium acids takes place according to the following equation. SeO ₄ ^2- + 3Fe + 8H ⁺ → Se ⁰ + 3Fe ²⁺ + 4H ₂
O After the impurities contained in the wastewater are brought into contact with the iron metal and reduced as described above, if an alkaline agent is added to the reduced water and the pH is adjusted to 7 or more, iron ions in the water are, for example,
It becomes water-insoluble iron hydroxide to form flocs as shown in the following formula. Fe ²⁺ + 2NaOH → Fe (OH) ₂ + 2Na ⁺ Fe ³⁺ + 3NaOH → Fe (OH) ₃ + 3Na ⁺ At this time, in addition to reduced selenium, heavy metals, suspended solids, fluorine and COD components contained in wastewater Etc. can be simultaneously separated by aggregation and sedimentation.

In the method of the present invention, examples of the iron metal particles to be brought into contact with drainage include particles of pure iron, crude steel, alloy steel, and other iron alloys. When the iron metal is an iron alloy, the iron content is preferably 85% by weight or more. By passing the wastewater through a packed bed of iron metal particles, such as a column filled with iron metal particles, it is possible to efficiently contact the wastewater with the iron metal particles. However, if the water continues to flow through the packed bed of iron metal particles, contaminants will adhere to the surface of the iron metal particles and clogging of the packed bed of iron metal particles will occur. Gradually decrease. Such contaminants include iron oxides, iron carbides, iron sulfides produced by the reaction of iron metal or iron ions,
There are suspended substances in wastewater. In the method of the present invention,
After passing the wastewater through the bed of iron metal particles and continuing the reduction treatment of impurities, stop the flow of wastewater, loosen the bed of iron metal particles by passing air through the bed of iron metal particles, and further wash A mixed flow of water and air is supplied in an upward flow to separate and remove contaminants adhering to the surface of iron metal particles, or
Remove contaminants that are clogging the packed bed of iron metal particles. In the method of the present invention, by stopping the flow of the wastewater and passing air through the packed layer of the iron metal particles, the packed layer of the iron metal particles is loosened before the iron metal particles form a block-like mass, and the block is formed. It is possible to prevent the formation of a lumpy mass. When nitrate nitrogen is contained in the wastewater, the iron metal particles are particularly likely to form block-like lumps. However, by passing air through the packed bed of iron metal particles, nitrate nitrogen of about several hundred mg / liter can be obtained. The formation of block-like lumps of iron metal particles can be prevented even when treating wastewater containing.

In the method of the present invention, there is no particular limitation on the flow direction when air is passed through the packed bed of iron metal particles, and it can be either an upward flow or a downward flow. However, by setting the ventilation direction to upward flow, the packed bed of iron metal particles can be effectively loosened, and the flow of acidic adjusted wastewater is usually upward due to the generation of hydrogen gas. Since the supply of the mixed flow of the washing water and the air is also performed in the upward flow, the ventilation of the iron metal particles into the packed bed is preferably performed in the upward flow from the viewpoint of equipment design and operation management. . In the method of the present invention, it is preferable that the ventilation speed for loosening the packed layer of iron metal particles is LV = 50 to 200 m / h. When the ventilation speed is less than 50 m / h, the packed layer of iron metal particles is not sufficiently loosened, and a block-like lump may be generated. If the ventilation speed exceeds 200 m / h, the consumed power is increased, and the fine metal particles may be scattered. Aeration time is 5 seconds ~
Preferably, it is one minute. If the ventilation is less than 5 seconds, the packed layer of iron metal particles may not be sufficiently loosened, and a block-like lump may be generated. Ventilation within 1 minute is usually sufficient, and usually the ventilation layer for 1 minute loosens the packed layer of iron metal particles so as not to form a block-like mass. In the method of the present invention, after the packed bed of iron metal particles is loosened by passing air through the packed bed of iron metal particles, a mixed flow of washing water and air is supplied in an upward flow. In the case of washing only with washing water, even if the packed layer of iron metal particles is developed, the effect of removing contaminants is small and the washing effect is not improved even if a large amount of washing water is consumed. Is supplied as an upward flow, the packed bed of iron metal particles expands and fluidizes, and is vigorously stirred by a mixed flow containing air bubbles, and contaminants adhering from the surface of the iron metal particles are peeled off. Discharged along with the clogging pollutants in the water stream.

In the method of the present invention, the supply rate of the washing water for forming the mixed stream of the washing water and the air is LV = 30.
It is preferably from 150 to 150 m / h. The flow rate of the washing water can be selected according to the size of the iron metal particles and the like, but when a mixed flow of the washing water and the air is supplied, the packed layer of the iron metal particles develops by 10 to 50%. It is preferable to set the degree. When the flow rate of the washing water is less than 30 m / h, the packed layer of the iron metal particles is less developed, and contaminants attached to the surface of the iron metal particles may not be sufficiently removed. When the flow rate of the washing water exceeds 150 m / h,
In addition to consuming a large amount of washing water, iron metal particles may flow out. In the method of the present invention, the supply rate of air for forming a mixed flow of washing water and air is LV =
It is preferably 50 to 200 m / h. If the air supply speed is less than LV = 50 m / h, the agitation power may be weak and the cleaning effect may not be sufficiently improved. Normally, the supply speed of air is sufficient to be LV = 200 m / h, and even if more air is supplied, the cleaning effect is not improved in proportion to the increase in the supply amount of air. In the method of the present invention, it is preferable to supply the mixed flow of the washing water and the air for 30 seconds to 5 minutes. If the supply of the mixed flow is less than 30 seconds, the cleaning of the packed bed of iron metal particles may be insufficient. The supply of the mixed flow within 5 minutes is usually sufficient, and the supply of the mixed flow longer than this does not improve the cleaning effect.

In the method of the present invention, it is preferable that after the cleaning is performed by supplying a mixed flow of the cleaning water and the air, the cleaning is performed using only the cleaning water. By washing only with the washing water, the contaminants separated by the mixed flow of the washing water and the air can be completely washed away, and bubbles can be expelled from the packed layer of the iron metal particles. Can be formed. In the method of the present invention,
It is preferable that the flow rate of the washing with only the washing water after the supply of the mixed flow of the washing water and the air is LV = 30 to 150 m / h. When the flow rate of the washing water is less than 30 m / h, the packed bed of the iron metal particles is less developed, and there is a possibility that the flushing of the separated contaminants and the expelling of bubbles are insufficient. When the flow rate of the cleaning water exceeds 150 m / h, the amount of the cleaning water to be consumed increases and the iron metal particles may flow out. In the method of the present invention, the washing with only the washing water after the supply of the mixed stream of the washing water and the air is performed by:
It is preferably performed for 10 seconds to 3 minutes. If the cleaning time using only the cleaning water is less than 10 seconds, there is a possibility that the removal of the separated contaminants and the removal of bubbles may be insufficient. Washing with only the washing water is usually sufficient for less than 3 minutes. Even if washing with only the washing water is continued longer than that, the washing effect is not improved. After the cleaning with only the cleaning water is completed, the supply of the cleaning water is stopped and settled,
A packed layer of iron metal particles is formed again. In the method of the present invention, after the packed bed of iron metal particles is loosened through air through the packed bed, a mixed flow of washing water and air is further supplied in an upward flow to remove contaminants in the packed bed of iron metal particles. Washing is performed at least twice a day. If the frequency of this washing is once a day, the filled iron metal particles may form a block-like mass. After loosening the packed bed of iron metal particles through the packed bed with air, a cleaning flow for removing contaminants in the packed bed of iron metal particles by supplying a mixed flow of washing water and air in an upward flow, and removing the contaminants from the packed bed of iron metal particles in one day. By performing the treatment twice or more times, the filled iron metal particles are prevented from forming a block-like lump, and the filled iron metal particles can be effectively used for water treatment.

FIG. 1 is an explanatory view of a method for cleaning a water treatment apparatus according to the present invention. The water treatment apparatus shown in this figure is provided with a water inlet 2 and an air inlet 3 at the bottom of a cylindrical reaction vessel 1,
A discharge port 4 for reducing water, washing water and air is provided on the head. A ferrous metal particle support plate 6 having a strainer 5 is attached to the lower part of the reaction tank, and a ferrous metal particle filling layer 7 is formed thereon by further filling the ferrous metal particle support plate.
A perforated plate 8 is attached to the upper part of the reaction tank, and an iron metal particle supply port 9 is provided. In the reduction treatment of the wastewater, wastewater whose pH is adjusted to 5 or less, preferably pH 2 to 3 by the addition of an acid is supplied from the water inlet, and the peroxosulfuric acid contained in the wastewater is filled in the packed bed of iron metal particles. , Iodic acid,
Reduction treatment of impurities such as selenic acid and nitric acid. Since the wastewater is introduced as an upward flow, the hydrogen gas generated during the reduction treatment moves upward together with the water flow, and is discharged from the outlet at the head of the reaction tank. The reduced water discharged from the discharge port is further led to the coagulation and sedimentation facility, where an alkaline agent is added.
The pH is adjusted to 7 or more, and if necessary, a polymer coagulant or the like is further added to perform coagulation precipitation treatment to obtain treated water. In the method of the present invention, the water treatment apparatus is washed at least twice a day. In order to wash the water treatment apparatus, the supply of the wastewater is stopped, and the packed bed of the iron metal particles is loosened by passing air from the air inlet. Next, a mixed flow of washing water and air is supplied to the packed bed of iron metal particles in an upward flow, whereby the packed bed of iron metal particles is developed and fluidized.
Due to the development and fluidization of the packed bed of iron metal particles, the contaminants adhering to the surface of the iron metal particles are peeled off, and are discharged from the outlet together with the pollutants that have caused clogging along with the mixed flow. After supplying the mixed flow of the cleaning water and the air for a predetermined time, the supply of the air may be stopped as necessary, and the cleaning using only the cleaning water may be performed. By performing the cleaning using only the cleaning water, the separated contaminants are completely washed away, and bubbles are expelled from the packed layer of the iron metal particles.
After washing with only the washing water, the supply of the washing water is stopped, and the iron metal particles are calmed down to form a packed layer. After that, the wastewater is supplied from the water inlet and the reduction process is restarted.
According to the method of the present invention, the filled iron metal particles are prevented from forming block-like lumps, the filled iron metal particles are effectively used for water treatment, and impurities in wastewater are stably removed over a long period of time. A reduction treatment can be performed.

[0011]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 A water inlet and an air inlet were attached to a lower part of an acrylic resin column having an inner diameter of 200 mm and a height of 1,000 mm, and a ferrous metal particle support plate provided with a strainer was provided immediately above the water inlet and the air inlet. In addition, an iron metal particle supply port, a perforated plate, and a reduction treatment water discharge port were provided at the top of the column. 10 liters of uniform spherical iron metal particles having a particle diameter of 0.6 mm were packed on the iron metal particle support plate to prepare a column having a packed layer of iron metal particles having the shape shown in FIG. Hydrochloric acid was injected into flue gas desulfurization wastewater containing 100 mg / liter of nitrate nitrogen at a pH of 6.7 so that the HCl concentration became 200 mg / liter. That is, water was passed in an upward flow at a speed of SV = 30 / h. Stop the flow of flue gas desulfurization wastewater every 12 hours, and allow air to reach LV = 135m
/ H in an upward flow for 20 seconds to loosen the packed bed of iron metal particles, then water = 100 m / h and air = 1
35m / h, 4 minutes per minute in the upward flow as a mixed flow of water and air
Water was supplied for 0 second, and finally, only water was supplied in an upward flow at LV = 100 m / h for 1 minute to complete the washing operation. After the completion of the washing operation, the treatment of the flue gas desulfurization wastewater was started again. The iron metal particles were supplied from the iron metal particle supply port such that the filling amount in the column became 10 liters. The treatment of the flue gas desulfurization effluent was continued for one month while washing every 12 hours, that is, twice a day, but no block-like mass was formed on the iron metal particles. Comparative Example 1 A column having the same packed layer of iron metal particles as in Example 1 was prepared, and the same process as in Example 1 was performed except that washing was performed every 24 hours, that is, once a day. Performed in parallel with Example 1. On the second day after the start of treatment, 5
A lump of 〜１０10 cm formed. The water treatment was continued under the same conditions for one month, but a block-like mass of iron metal particles was always present in the column.

[0012]

According to the method for cleaning a water treatment apparatus of the present invention, in a water treatment apparatus for reducing impurities in wastewater by passing water through a packed bed of iron metal particles, the filled iron metal particles are formed in a block shape. Lumps are prevented from being formed, the filled iron metal particles are effectively used for water treatment, and the reduction treatment of impurities in wastewater can be stably performed over a long period of time.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method for cleaning a water treatment apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Water inlet 3 Air inlet 4 Outlet 5 Strainer 6 Iron metal particle support plate 7 Packing layer of iron metal particles 8 Perforated plate 9 Iron metal particle supply port

Claims (3)

(57) [Claims] 1. A water treatment apparatus for reduction treatment of impurities in the waste water was passed through the packed bed of iron metal particles, vent the filling layer
At a speed of LV = 50-200 m / h, the packed bed of iron metal particles is loosened through air for 5 seconds to 1 minute , and then a mixed flow of washing water and air is supplied in an upward flow. And a cleaning method for removing contaminants from the packed bed of iron metal particles at least twice a day. 2. A cleaning process using a mixed flow of cleaning water and air.
After that, it is further characterized by washing with only washing water
The method for cleaning a water treatment apparatus according to claim 1, wherein 3. A packed bed of iron metal particles by adjusting waste water to be acidic.
The water treatment according to claim 1, wherein water is passed through the water treatment.
Method for cleaning equipment.