JP2013059705A - Method and apparatus for clarifying raw water containing iron, manganese and ammoniacal nitrogen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for clarifying raw water containing iron, manganese and ammoniacal nitrogen such as ground water, in which by oxidizing and filtering dissolved iron and manganese by a filter medium having attached microorganisms without using chemicals, the iron and manganese are removed while slightly leaving a part thereof and the ammoniacal nitrogen valuable as a fertilizer is left in treated water to obtain agricultural water allowing the saving of the fertilizer for an agricultural land.SOLUTION: In the clarifying method, the iron removal and manganese removal of the raw water containing at least iron, manganese and ammoniacal nitrogen are performed by a biological filtering method. In the clarifying method, oxygen is dissolved in the raw water so that the dissolved oxygen concentration of the obtained treated water is 4 mg/L or more, iron removal, manganese removal and nitrification are controlled so that at least the ammoniacal nitrogen remains in the treated water and then filtration is performed by contact with microorganisms, thereby the treated water containing the ammoniacal nitrogen is obtained.

Description

  The present invention relates to a method for purifying raw water containing iron, manganese, and ammonia nitrogen such as groundwater, and in particular, removes iron / manganese dissolved in the raw water by biological filtration without using chemicals, leaving only a part. In addition, the present invention relates to a purification method and a purification device for obtaining agricultural water in which a large amount of ammonia nitrogen, which is valuable as a fertilizer, remains in treated water and can save fertilizer in farmland.

In many cases, iron, manganese, ammonia nitrogen, and the like are dissolved in groundwater, and when groundwater containing these is used as agricultural water, purification is performed to remove excess iron and manganese.
When removing iron and manganese from groundwater containing ammonia nitrogen and using them for agricultural water, conventionally, a chlorine-based oxidant is injected and ammonia nitrogen is completely removed, then iron is oxidized and manganese is oxidized. Have been removed. In the iron and manganese treatment, an oxidant is added and removed by a catalytic filtration method filled with a catalyst. Since the oxidation of manganese proceeds slowly, it is self-oxidized using a catalyst coated with manganese dioxide.
Originally used as a water purification technology for drinking water, drinking water maintains the residual chlorine concentration when ammonia nitrogen remains because the water supply law stipulates that residual chlorine be maintained at the faucet. The presence of ammoniacal nitrogen was unlikely because it could not be done, and it was desired that it be completely treated. Therefore, the chemical oxidation method as described above has come to be used.

  In the case of this chemical treatment method, ammonia nitrogen is reacted first, so iron and manganese can be treated only after ammonia nitrogen is completely removed by the breakpoint chlorine injection method. Also, if an excessive amount of oxidizing agent is added to remove iron and manganese, the oxidizing agent may remain in the treated water, and the remaining remaining oxidizing agent will adversely affect the crops. It is necessary to do. In addition, a large amount of oxidant is required to remove ammoniacal nitrogen with a chlorine-based oxidant.

  In addition, as a method for oxidizing manganese without being influenced by ammoniacal nitrogen, there is a method using potassium permanganate as an oxidizing agent, but the cost of chemicals is higher than that of chlorine, leading to an increase in manufacturing cost. Further, for the above reasons, ammoniacal nitrogen is desired to be treated separately. When the ammonia nitrogen is removed with chlorine, trihalomethane is produced by the extra chlorine added.

  Conventionally, in a water supply facility called biological filtration (Patent Document 1), a processing method (Patent Document 2) in which an oxygen supply amount is adjusted using a drop (Patent Document 2), oxygen-containing gas is added to water to be treated. Examples include the supplied method (Patent Document 3). The aeration filtration pond type biological treatment device has a biological filtration device with an aeration device and sand filtration equipment, and is introduced for the purpose of treating ammonia nitrogen and organic matter in drinking water applications. It has been pointed out that the biological filtration method is inaccurate and maintenance is troublesome, but in reality it is not only fully automated, but it can be washed once every 3 days at normal groundwater levels. It is an inexpensive processing method. However, a bulky facility is required, and water is flowed by a natural flow method, so an RC structure is often used, and it can be an excessive facility in a farm with a small amount of water. Even when aeration is used or when a head is used, or when the oxygen supply amount is adjusted by supplying an oxygen-containing gas, an environment is established in which oxygen reaches all microorganisms. It is not possible to build a system that removes iron and manganese.

Agricultural water, unlike drinking water, is one of the nutrient salts, so it does not need to be completely removed and does not require residual chlorine. Since iron and manganese are also essential elements, they do not need to be completely removed and may remain to the extent that no scale is attached to the piping.
Thus, a water purification method with easy operation management has been developed that allows ammonia nitrogen to remain, remove iron and manganese to some extent, and backwash and regenerate while filling the filter medium without using chemicals. Absent.

JP 2003-290784 A JP 2005-288417 A JP 2010-89046 A

  In the present invention, from raw water containing iron, manganese and ammonia nitrogen such as groundwater, without using chemicals, the dissolved iron / manganese is oxidized by a filter medium to which microorganisms adhere, and a very small part is left by filtration. An object of the present invention is to provide a purification method and a purification apparatus for removing agricultural nitrogen that is valuable as a fertilizer and remaining in treated water to obtain agricultural water that can save fertilizer in farmland.

  As a result of intensive studies, the present inventors have found that when the iron / manganese dissolved in raw water containing iron, manganese and ammoniacal nitrogen is removed by biological filtration, the dissolved oxygen concentration of the treated water obtained is 4 mg / Nitrogen removal of iron, manganese removal, and ammonia nitrogen so that at least ammonia nitrogen remains in the treated water by dissolving oxygen in the raw water so that it becomes L or higher and contact filtering with microorganisms at high speed. ) Can be controlled, and a large amount of ammoniacal nitrogen remains in the treated water, and it has been found that agricultural water capable of saving fertilizer in farmland can be obtained, and the present invention has been achieved.

That is, the present invention is as follows.
(1) A purification method for removing iron and manganese by raw filtration of raw water containing at least iron, manganese, and ammonia nitrogen, and the dissolved oxygen concentration of the obtained treated water is 4 mg / L or more In this way, oxygen is dissolved in the raw water so that at least ammonia nitrogen remains in the treated water, and it is controlled by removing iron, removing manganese, and nitrifying to come into contact with microorganisms and contain ammonia nitrogen. A purification method characterized by obtaining treated water.
(2) The above-mentioned treated water has a combined iron and manganese concentration of 0.2 to 0.5 mg / L and an ammoniacal nitrogen concentration of 0.5 mg / L to 5 mg / L (1) The purification method described.
(3) The purification method according to (1) or (2), wherein the dissolved oxygen concentration of the raw water in which the oxygen is dissolved is 9 mg / L or more.
(4) An oxygen dissolving step for dissolving oxygen in the raw water and a porous filter medium having a particle size of 1 mm to 4 mm to which microorganisms were attached were filled so that the dissolved oxygen concentration of the treated water obtained was 4 mg / L or more. The raw water in which oxygen is dissolved is passed through the biological filtration tower at a superficial velocity of 3 hr ^{-1 to} 10.5 hr ^-1 to control the removal of iron, manganese and nitrification by microorganisms adhering to the filter medium, and ammonia nitrogen. The purification method according to any one of the above (1) to (3), further comprising a step of obtaining treated water containing.
(5) A purification device used in the purification method according to any one of (1) to (4), wherein oxygen is dissolved in the raw water so that the dissolved oxygen concentration of the treated water obtained is 4 mg / L or more. And a biological filtration tower packed with a porous filter medium having a particle diameter of 1 mm to 4 mm to which microorganisms are attached, and the microorganisms attached to the filter medium so that ammonia nitrogen remains in the treated water And a biological filtration tower for controlling nitrification.
(6) The purification device has a treated water storage tank, and the storage tank has at least one of a facility for shielding light, a UV irradiation device, an aeration device, and a circulation device. The processing apparatus as described.

According to the present invention, from raw water containing iron, manganese, and ammonia nitrogen such as groundwater, without using chemicals, dissolved iron and manganese are removed leaving a very small portion, and ammonia nitrogen that is valuable as a fertilizer A large amount of water remains in the treated water, and agricultural water that can save fertilizer in farmland can be obtained.
Further, according to the purification method of the present invention, regeneration by backwashing can be performed while the filter medium is filled, and operation management is easy.

It is the schematic of an example of the purification apparatus of this invention. 1 is a schematic view of a purification device used in Example 1. FIG. 2 is a graph showing the treatment status of ammonia nitrogen when water is passed at a superficial velocity of 6 hr ⁻¹ in Example 1. FIG.

  The present invention relates to a purification method for removing iron and manganese by a biological contact filtration method of raw water containing at least iron, manganese, and ammonia nitrogen, and the dissolved oxygen concentration of the obtained treated water is 4 mg / L or more Oxygen is dissolved in the raw water so that at least ammonia nitrogen remains in the treated water, and it is controlled by removing iron, removing manganese, and nitrifying to contact with microorganisms and containing ammonia nitrogen. It is a purification method for obtaining treated water, and it is preferable that the concentration of iron and manganese in the treated water is 0.2 to 0.5 mg / L in total and the concentration of ammoniacal nitrogen is 0.5 mg / L to 5 mg / L. . Moreover, in order to make the dissolved oxygen concentration of the obtained treated water 4 mg / L or more, it is preferable that the dissolved oxygen concentration of the raw water in which oxygen is dissolved is 9 mg / L or more.

In the conventional biological filtration method, aeration is performed to replenish dissolved oxygen and filtration is performed in a saturated state of oxygen. At the same time as iron and manganese are removed by microorganisms, ammonia nitrogen is nitrified and obtained. The treated water contained almost no ammoniacal nitrogen.
In the present invention, when oxygen is dissolved in raw water and filtered so that the dissolved oxygen concentration of the obtained treated water is 4 mg / L or more, iron removal, manganese removal and nitrification are controlled, and ammonia nitrogen is added. By obtaining it as treated water before it is completely nitrified, it is possible to obtain a treated liquid in which much ammonia nitrogen remains in the treated water. Since ammonia nitrogen becomes fertilizer, fertilizer can be saved by using this treated water as agricultural water.

  The dissolved oxygen concentration in the treated water (hereinafter simply referred to as treated water) after the biological filtration treatment is 4 mg / L or more, preferably 5 mg / L or more. The dissolved oxygen concentration in the treated water is less than 4 mg / L. And the iron removal performance deteriorates. In biological treatment, microorganisms adhere to the entire filter medium, and there is oxygen necessary for breathing for microorganisms to survive apart from removal of most of iron and manganese and nitrification of some ammonia nitrogen, and below 4 mg / L As a result, the microbial reaction decreases. The upper limit of the dissolved oxygen concentration in the treated water is about 9 mg / L. When oxygen is not used, the dissolved oxygen concentration of the raw water may be lowered in consideration of economy.

In the present invention, the dissolved oxygen concentration of the raw water is preferably 9 mg / L or more so that the dissolved oxygen concentration of the treated water is 4 mg / L or more so that a sufficient microbial reaction is performed. More preferably, it is 9-11 mg / L.
If the dissolved oxygen concentration in the treated water is too low, iron and manganese are difficult to remove, iron remains 0.3 mg / L or more, manganese remains 0.2 mg / L or more, and the total concentration of iron and manganese is 0.5 mg. / L or more.
The amount of oxygen dissolved in the raw water in order to make the dissolved oxygen concentration of the treated water 4 mg / L or more depends on the concentrations of ammoniacal nitrogen, iron and manganese in the raw water. When the iron concentration is 1-2 mg / L and the ammoniacal nitrogen concentration is about 2 mg / L, 8 mg / L or more, when the iron concentration is 2-4 mg / L, and the ammoniacal nitrogen concentration is about 2 mg / L, It is preferable to be 9 mg / L or more.
In addition, when the iron concentration is 4 mg / L to 15 mg / L, the filtration tower is divided into two towers, and when the iron concentration is 15 to 30 mg / L, the filtration tower is divided into three towers to supply oxygen to all. An apparatus is preferably provided. When the iron concentration is 30 mg / L or more, a diffuser and a coarse filter medium are introduced into the raw water tank, and a process for aeration treatment is provided. Before the biological filtration process, a part of iron is used as a colloid of iron oxide. It can be filtered and removed. At this time, it can be more reliably removed by using a coagulant together.

  Examples of the raw water include groundwater, and the normal water temperature is about 17 ° C. Since the saturated dissolved oxygen concentration of distilled water at 1 atm and 17 ° C. is 9.37 mg / L, it is preferable to dissolve oxygen under pressure in order to make the dissolved oxygen concentration of raw water 9 mg / L or more. By making the oxygen dissolution method pressure dissolution, when dissolved at a water temperature of 17 ° C. and a gauge pressure of 0.12 MPa, it can be dissolved up to about 15 mg / L.

The total concentration of iron and manganese in the treated water is preferably 0.2 to 0.5 mg / L. When iron and manganese are also used as agricultural water, they are useful for growing crops, but it is preferable to treat them to such a level that they do not become scales in the piping. If the concentration is less than 0.2 mg / L, it is relatively transparent and has little coloration. However, there is a concern about the lack of iron in the soil. More scale adheres to the nozzles
The concentration of ammoniacal nitrogen is preferably 0.5 mg / L to 5 mg / L, more preferably 0.5 to 3.0 mg / L. If it is less than 0.5 mg / L, there may be a shortage of nutrients, so a large amount of fertilizer is required. If it exceeds 5 mg / L, nutrients are abundant and plankton, microorganisms, bacteria, etc. are generated. However, oxygen in the treated water is consumed, and it tends to be water with little dissolved oxygen. In addition, the soil tends to become acidic soil, which is not preferable. If it exceeds 10 mg / L, the roots may die.

  The levels of iron, manganese and ammoniacal nitrogen in the treated water according to the present invention are 0.5 mg / L for Fe + Mn, which is a target value for recycled water, and 0 for Fe + Mn, which is a target value for car wash water. .3 mg / L and the like. Incidentally, the tap water level is preferably 0.3 mg / L or less for iron, 0.05 mg / L or less for manganese, and 0.05 to 0.3 mg / L from the viewpoint of chlorine disinfection, although ammonia nitrogen is not standard.

In order to obtain the above-mentioned treated water, the purification method of the present invention comprises an oxygen dissolving step for dissolving oxygen in the raw water so that the dissolved oxygen concentration of the obtained treated water is 4 mg / L or more, and particles to which microorganisms are attached. The raw water in which oxygen is dissolved is passed through a biological filtration tower packed with a porous filter medium having a diameter of 1 mm to 4 mm at a superficial velocity of 3 hr ^{-1 to} 10.5 hr ^-1 to remove microorganisms adhering to the filter medium. And a step of controlling the iron, manganese removal, and nitrification to obtain treated water containing ammoniacal nitrogen.

As the quality of the raw water, when the number of filtration towers is one, iron 0.5-4 mg / L, manganese 0.2-1.0 mg / L, ammoniacal nitrogen 0.8-7.0 mg / L Is preferably used. The ammonia nitrogen concentration is preferably as high as or higher than the manganese concentration. In agricultural land, fertilizers penetrate groundwater, and the concentration of ammoniacal nitrogen in groundwater is usually higher.
When the amount of iron contained in the raw water is as high as 30 mg / L or more, a step of aeration treatment of the raw water can be provided before oxygen is dissolved in the raw water.
If sufficient aeration is performed in the previous stage, insoluble iron oxide is formed as colloidal particles. In the present invention, the colloidal particles can be removed to some extent by the subsequent biological filtration tower. Filtration of colloidal particles, which has been difficult in the past, can be captured by microbial membranes of iron-oxidizing bacteria, manganese-oxidizing bacteria, and nitrifying bacteria that adhere to the surface of a porous filter medium having a particle size of 1 mm to 4 mm. The colloid cannot be removed even with fine sand of 0.3 mm considering only the particle size, but the treatment is easy due to the filtration effect by the microbial membrane. Here, the particle diameter is an effective diameter (hereinafter referred to as “particle diameter”). The effective diameter refers to the particle diameter at 10% when fractionated by sieving and expressed as cumulative weight passage rate.
Iron and manganese other than iron insolubilized in the raw water aeration process step are oxidized in the biological filtration tower with the aid of dissolved oxygen and are processed to the above-mentioned level so as not to become scale in the piping.

  The control method of iron removal, manganese removal, and nitrification to obtain treated water before ammonia nitrogen is completely nitrified is to pass the particle size, bed height, and raw water of the filter medium packed in this biological filtration tower. Speed, washing frequency, dissolved oxygen amount, and the like. Microorganisms involved in the treatment of iron, manganese, or ammonia nitrogen have a certain degree of segregation in the biological filtration tower due to the characteristics of the microorganisms responsible for oxidation. Iron is removed by iron-oxidizing bacteria, but it is very easy to grow and easy to increase. Manganese-oxidizing bacteria are very difficult to grow and are not autotrophic bacteria, and therefore require symbiosis with other bacteria or a small amount of organic matter. Nitrifying bacteria that treat ammonium nitrogen to nitrate nitrogen are not as fast as manganese-oxidizing bacteria, but they grow slowly. However, since it is an autotrophic bacterium, it can grow alone without the need for organic matter. For this reason, when raw | natural water flows in from the upper part of a filtration tower, it grows in order of iron-oxidizing bacteria, then nitrifying bacteria, and manganese bacteria from the upper part. Nitrifying bacteria are partly mixed with iron-oxidizing bacteria, and often mixed with lower-layer manganese oxidizing bacteria. Normally, raw water often has higher ammonia nitrogen concentration than manganese concentration, and the oxidation rate of manganese can be faster than the nitrification rate of ammonia. Can be left in the treated water.

The porous filter medium packed in the biological filtration tower preferably has a particle diameter of 1 mm to 4 mm, more preferably a particle diameter of 2 to 3 mm, and a filter medium larger than that usually used in the biological filtration tower is preferred and insolubilized. It is possible to adsorb and remove the colloidal iron adsorbed on the biofilm by microorganisms adhering to the filter medium. Further, it is preferable to perform the treatment at a high filtration rate of 3hr ^-1 ~10.5hr ^-1 than the normal rapid filtration tower.
When a filter medium having a small particle diameter of less than 1 mm is used, the filtration rate cannot be increased. If the same amount of treated water is used, the cross-sectional area of the filtration tower increases. Moreover, since the specific surface area of a filter medium becomes large, the amount of attached microorganisms increases, and it may be processed completely, and ammonia nitrogen cannot remain in treated water. Although it is conceivable to control by making the bed height thin, if the bed height is made thin, the residence time is short, so there is a possibility that it cannot be handled if there is a concentration variation in the raw water.
When the particle diameter exceeds 4 mm, the specific surface area of the filter medium becomes small and the removal amount cannot be expected. Therefore, when the content is determined to be 0.5 mg / L with iron + manganese, the layer height of the filter medium is increased, or It is necessary to install about 2-3 filtration towers side by side.
The porous filter medium preferably has a bulk specific gravity of about 0.9 to 1.1. When it becomes larger than 1.1, it will become a thing without a hole, a living organism will not adhere easily and a specific surface area will also become small.

Moreover, although the bed height of a filter medium is based also on the diameter of a filtration tower, 0.6m-2.2m are preferable, 1.2m-2m are more preferable, Furthermore, 1.6m-2m are especially preferable.
When the layer height exceeds 2.2 m, the residence time becomes longer and the processing accuracy increases. However, since the oxygen becomes inaccessible, the layer height needs to be set in consideration of the dissolved oxygen concentration. In addition, pressure loss tends to increase, and the apparatus is tall and uneconomical.
When it is necessary to increase the height of the filter medium depending on the state of the raw water, it is preferable to divide the filtration tower into a plurality of sections and to make the height of the filter medium of one tower less than 2.2 m.
When the layer height of the filter medium is less than 0.6 m, the treatment of iron and manganese becomes unstable.

The filtration rate is important for allowing ammonia nitrogen to remain in a state in which oxygen is well maintained, and a filtration superficial velocity of 3 hr ^{-1 to} 10.5 hr ^-1 is preferred.
When the filtration superficial velocity is less than 3 hr ⁻¹ , the time of contact with microorganisms becomes longer, nitrification of iron removal, manganese removal, and ammonia nitrogen proceeds, and the concentration of ammonia nitrogen in the resulting treated water is low. Become. Moreover, it becomes difficult to make the dissolved oxygen concentration of treated water into 4 mg / L or more. Moreover, if the same amount of treated water is used, the cross-sectional area of the filtration tower increases as described above, which is uneconomical.
If the filtration superficial velocity exceeds 10.5 hr ⁻¹ , the removal rate of manganese will deteriorate, and more water will be treated in the space filled with the same filter medium, and the amount of metal salt that precipitates will be larger accordingly. Thus, the degree of increase in pressure loss increases, and the frequency of backwashing is increased. Since the washing frequency is good for manganese oxidation about once every 2 to 3 days, if the iron concentration of raw water is about 2 to 3 mg / L, the filtration superficial velocity is preferably about 6 to 7 hr ^−1. .
Finally, it is possible to adjust the amount of dissolved oxygen.

As the porous filter medium, it is sufficient that the width of the particle size variation is small, lighter than sand, and porous, and various materials such as zeolite, anthracite, garnet, pumice, activated carbon are used. it can. When water is passed through the filtration tower from above, it is preferable to sink in water.
As microorganisms that oxidize iron and manganese, basically, microorganisms contained in raw water adhere to the porous filter medium packed in the biological filtration tower and proliferate, but the removal performance is exhibited. Since it may take 3 months, it is particularly limited if it contains iron bacteria, manganese oxidizing bacteria, and nitrifying bacteria that are already used for removing iron and manganese in order to shorten the period. Not a thing but a well-known thing can be used. Examples include Gallionella, Thiobacillus, Leptothrix, Caldimonas, Hyphomicrobium, Nitrosomonas, Nitosospira, Nitrobacter, Nitrospira, Geobacter, Geothrix and the like.
Examples of the raw water containing at least iron, manganese, and ammonia nitrogen include groundwater and river water. The raw water may contain lead, arsenic, cadmium, etc., but these are also removed by the purification method of the present invention.

  Although the biological filtration tower according to the present invention has good filtration performance, clogging occurs due to the generation of iron oxide / manganese dioxide sludge, and backwashing is required when the pressure loss increases. In general groundwater, for example, when iron is 2 mg / L, manganese is 0.5 mg / L, and ammoniacal nitrogen is 3 mg / L, this biological filtration tower needs to be cleaned about once every three days. . In the sand filtration apparatus for chemical treatment, washing twice a day is necessary, but in the biofiltration, washing is less due to the effect of the microbial membrane.

  Cleaning is based on backwashing using ordinary water, and complicated operations such as high-pressure water cleaning are not required. Good exfoliation and concentration of sludge are extremely important in the present invention, and enable continuous operation with a small amount of washing water.

  The purification apparatus of the present invention has an oxygen dissolving apparatus for dissolving oxygen in raw water so that the dissolved oxygen concentration of the treated water obtained is 4 mg / L or more, and a particle size of 1 mm to 4 mm on which microorganisms are attached. A biological filtration tower packed with a porous filter medium, and at least a biological filtration tower that controls iron removal, manganese removal, and nitrification by microorganisms attached to the filter medium so that ammoniacal nitrogen remains in the treated water.

When the iron concentration of the raw water is high, a raw water aeration apparatus having an aeration device for aeration of the raw water can be provided separately from the oxygen dissolving apparatus for dissolving oxygen in the raw water.
The oxygen dissolving device is preferably a device that dissolves oxygen under pressure. For example, the oxygen dissolving device can be composed of a compressor and an ejector for pressurizing air, and oxygen pressure dissolving that dissolves oxygen in the raw water piping through the ejector. Apparatus. Alternatively, a biological filtration tower may be used as a pressure vessel, and oxygen may be dissolved under pressure in the biological filtration tower.

The biological filtration tower is preferably a pressure vessel because of its ease of control and flexibility. Moreover, when considering using treated water as agricultural water, a pressure vessel is suitable from the scale, the quality of groundwater, etc., and it is preferable that the oxygen dissolution method is pressure dissolution. The pressure in the biological filtration tower is more preferably 0.04 MPa to 0.25 MPa, more preferably 0.04 MPa to 0.17 MPa in terms of gauge pressure.
In an open biological treatment tower, the dissolved oxygen concentration can be increased to about 8 mg / L by aeration from the bottom of the tower, but the pressure loss can only be reduced to about 1 m (0.01 MPa). It is not suitable as a device of scale because it is not versatile. A pressure loss of 1 m has a drawback that the installation area of the apparatus becomes too large, and a compact pressure vessel type is suitable for a small amount of water.
Then, raw water is passed through the filtration tower at 3 hr ⁻¹ to 10.5 hr ⁻¹ , and iron removal, manganese removal, and nitrification are performed by microorganisms attached to the filter medium. The filtration tower is preferably provided with a dissolved oxygen concentration sensor and a control valve for controlling the dissolved oxygen concentration.

The purification method and the purification apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a raw water aeration apparatus used in the former stage of the present invention, a pressurized oxygen dissolving apparatus provided in a raw water pipe, and a final biological filtration tower.
The groundwater pumped from the well by the pump 1 is supplied with air from the raw water blower 3 to the aeration device 4 installed in the raw water tank 2 so as to reach saturated dissolved oxygen. The groundwater in which dissolved oxygen is saturated passes through the raw water pipe 15 by the raw water pump 5, adjusts the flow rate by the ejector valve 8, pressurizes the air by the compressor 36, and guides it to the raw water pipe 15 through the pressurized air pipe 34. 7 to mix pressurized air and raw water. When the iron concentration in the raw water is high, it is preferable to add a coarse filter medium here, remove a part of the insolubilized iron in advance, and then pressurize and dissolve the air in the treated water. Raw water and air are mixed under pressure to dissolve oxygen so that the dissolved oxygen concentration of the treated water becomes 4 mg / L or more, and flows into the biological filtration tower 10. In the biological filtration tower 10, a porous filter medium 18 to which microorganisms are attached is preferably filled with 0.6 m or more, and gravel 19 is concealed in the lower part so that the filter medium does not leak from the treated water collection pipe 20. It is spread to the height. The raw water that has flowed into the biological filtration tower 10 from the upper part is sequentially removed from the iron while passing through the filter medium 18, and a part of ammonia nitrogen is nitrified to remove manganese. The treated raw water flows into the water collecting pipe 20 as treated water, is stored in the water storage tank 11 through the lower treated water pipe 16 and the outflow valve 9, and is used as agricultural water. If the manganese concentration in raw water is about 0.5 mg / L and the ammoniacal nitrogen concentration is about 2 mg / L, manganese can be lowered to 0.1 mg / L, leaving about half of the ammoniacal nitrogen.

  The oxygen pressure dissolving apparatus is composed of an ejector 7 and a compressor 36. Pressurized air is supplied by the compressor 36, the air and raw water in the ejector 7 are mixed, and the amount of dissolution can be controlled by the supply pressure of air and the flow rate of raw water introduced to the ejector 7.

  The biological filtration tower 10 includes an air washing tube 21. When the pressure in the biological filtration tower becomes high to some extent, air washing, back-flow washing, and water removal are performed. Specifically, the cleaning is preferably performed when the pressure increase in the filtration tower is about 0.25 MPa at the maximum, and preferably when the pressure increase is about 0.04 to 0.17 MPa. If the pressure rises too much, water will form and processing performance will deteriorate. When the internal pressure of the biological filtration tower reaches a predetermined pressure, the drain valve 8 is opened, the raw water pump 5 is stopped, the open valve 22 is opened, water is drained to the position of the drain pipe 32, and then the washing blower valve 23 is opened. The opening washing blower 22 is operated and air is sent to an air washing tube 21 installed at the bottom of the biological filtration tower 10, and the filter medium 18 is developed with air to separate sludge and excess microorganisms attached to the filter medium 18. . The separated sludge is sent to the sludge storage tank 45 by backwashing. In the backwashing, the discharge valve 40 and the washing water valve 39 are opened, the washing pump 37 is operated, the treated water in the water storage tank 11 is passed through the washing water pipe 38, and the treated water is introduced from the bottom of the biological filtration tower 10 and the separated sludge is put on To the sludge storage tank 45 through the discharge pipe 33. After that, sludge that could not be washed out is removed by waste water washing to ensure good water quality. Waste water cleaning is a normal water purification process (pumping pump 1 → well water piping 14 → raw water tank 2 → raw water pump 5 → raw water piping 15 → biological filtration tower 10 → collection pipe 20) with the outflow valve 9 closed and a drain valve Open 12 and release. The drainage valve 12 is closed and the outflow valve 9 is opened and the treated water is stored in the water storage tank 11 in about 10 minutes, the time during which the inside of the biological filtration tower is replaced.

  The sludge transferred to the sludge storage tank 45 is distributed to the sun drying floor 36 by the transfer pump 45. The sun-dried bed is filled with a filter medium 41, and the washed sludge remains on it, and becomes a dehydrated cake 42 by the sun. The water of the cleaning sludge is discharged out of the system by the drain pump 44.

  Although FIG. 1 shows a one-column system, when the layer height of the filter medium needs to be increased in order to adjust the water quality, the filter tower may be divided into two to make two towers. When the iron concentration of the raw water is 4 mg / L or more, even if the layer height of the filter medium is set to 2.2 m, the removal of iron is worsened, and the dissolved oxygen concentration of the treated water is 4 mg / L or less and the microbial reaction is lowered. Such a problem may occur. If the layer height of the filter medium is increased, the above-described problems may occur. In this case, the filtration tower can be divided into two towers. In the case of using two towers, the dissolved oxygen concentration of the treated water obtained by treatment with the two filtration towers may be 4 mg / L, but the dissolved oxygen concentration of the treated water treated in the first tower is 4 mg / L. Oxygen is dissolved in the raw water so as to be L or more, treated in the first tower, and further treated in the first tower so that the dissolved oxygen concentration of the treated water treated in the second tower is 4 mg / L. It is preferable to dissolve oxygen in the treated water.

In the treated water treated according to the present invention, nutrients useful for the growth of crops remain, and since chlorine is not added for the treatment, when the treated water is stored, algae is stored in the storage tank. And creatures are more likely to occur. Therefore, clear water is always obtained in the storage tank 11 by combining a facility for shielding light, an immersion type UV illumination device, an aeration device, and a circulation line to the biological filtration tower 10.
Examples of the facilities for shielding light include providing a light-shielding lid or making the water storage tank light-shielding.
UV irradiation equipment does not use chemicals such as chlorine, so it is optimal for agricultural use. However, maintenance is required because the lamp needs to be replaced about once a year. It is preferable to provide an aeration apparatus in the storage tank and provide a line that circulates to the biological filtration tower when residual nutrients are insolubilized by aeration. Although nutrients tend to decline, they are more suitable for agricultural purposes than chlorine disinfection.

Next, the present invention will be described in more detail with reference to experimental examples.
Example 1
A column having a length of 200 cm and an inner diameter of 3 cm was filled with 70 cm of a zeolite filter medium having a particle diameter of 1 to 3 mm and having microorganisms with an effective diameter of 2 mm attached thereto. The microorganisms attached were Gallionella, Leptothrix, Nitrosomonas and Nitrobacter. As shown in FIG. 2, air is diffused on the surface of the filter layer, air is supplied at 0.12 MPa, and the dissolved oxygen concentration of the raw water (17 ° C.) is set to 9 to 11 mg / L. Water was passed at 6 hr ⁻¹ . In FIG. 2, the reverse cleaning device is omitted, but as shown in FIG. 1, a reverse cleaning device is provided. In Example 1, the reverse cleaning is performed once every two days when the pressure increases to 0.04 MPa. went.
The raw water quality at this time is 2 mg / L for iron, 0.5 mg / L for manganese, and 2.0 mg / L for ammoniacal nitrogen, and the water quality when the treated water quality is stable after operation for about 1.5 months is Iron became 0.03 mg / L or less. Manganese was 0.3 mg / L and ammoniacal nitrogen was 1.6 mg / L, and treatment with 80% ammoniacal nitrogen remaining was possible. In the treated water, the dissolved oxygen concentration was 6 mg / L or more. The treatment status of ammonia nitrogen is shown in FIG.
The concentration of iron and manganese in the raw water and treated water was determined by flame atomic absorption spectrophotometry shown in 60.2 and 58.2 of JIS K0101, respectively, and the concentration of ammoniacal nitrogen was described in 36.2 of JIS K0101. It was measured by indophenol blue absorptiometry.
Moreover, the dissolved oxygen concentration in raw | natural water and treated water was measured with the measuring method using the diaphragm type sensor (Toa DK Co., Ltd. product, portable dissolved oxygen meter).

When the flow rate was set to a superficial velocity of 10 hr ⁻¹ , iron was 0.1 mg / L, manganese was 0.4 mg / L, and ammoniacal nitrogen was 1.8 mg / L. The leak concentration of manganese and ammonia nitrogen increased slightly. The dissolved oxygen concentration of the treated water was 7 mg / L or more.

When the flow rate was set at a superficial velocity of 3 hr ⁻¹ , iron became 0.01 mg / L, manganese 0.2 mg / L, and ammoniacal nitrogen 1.2 mg / L.
The dissolved oxygen concentration of the treated water was 5 mg / L or more.

(Example 2)
In Example 2, water was passed through in the same manner as in Example 1 except that the filter medium in Example 1 was changed to a zeolite filter medium having a particle diameter of 2 to 4 mm and an effective diameter of 3 mm.
Under conditions of a superficial velocity of 6 hr ⁻¹ , the quality of the treated water is 0.3 mg / L for iron, 0.4 mg / L for manganese, and 2.0 mg / L for ammoniacal nitrogen, and the dissolved oxygen concentration in the treated water Was 7 mg / L. When the superficial velocity was 3 hr ⁻¹ , the water quality of the treated water was iron 0.1 mg / L, manganese 0.3 mg / L, and ammoniacal nitrogen 1.5 mg / L. The dissolved oxygen concentration of the treated water was 4 mg / L. In terms of superficial velocity 6hr ^-1 but the removal rate of the iron and manganese became slightly worse than Example 1, lowering the iron in the treated water, the concentration of manganese by the superficial velocity and 3 hr ^-1 I was able to. When a filter medium having a slightly larger particle size is used, the removal amount of iron and manganese is deteriorated, but the removal amount can be increased by reducing the superficial velocity. In this case, the washing is related to the raw water, but if the water quality is the same, it is about once every four days.

(Example 3)
Treatment of raw water containing 0.3 mg / L iron, 0.4 mg / L manganese, and 0.5 mg / L ammonia nitrogen under the conditions of a superficial velocity of 10 hr ⁻¹ using the filter medium having an effective diameter of 3 mm of Example 2. Water was passed in the same manner as in Example 2 except that. The quality of the obtained treated water was 0.1 mg / L for iron, 0.3 mg / L for manganese, and 0.3 mg / L for ammoniacal nitrogen. Moreover, the dissolved oxygen concentration of treated water was 7 mg / L or more.

Example 4
The filter medium in Example 1 is in the range of 0.6 to 2 mm in particle size, changed to a zeolite filter medium with an effective diameter of 1.2 mm, and the same as in Example 1 except that backwashing was performed once a day. The water was passed through. Under the conditions of a superficial velocity of 8 hr ⁻¹ , iron was 0.1 mg / L, manganese was 0.4 mg / L, and ammoniacal nitrogen was 1.5 mg / L. Moreover, the dissolved oxygen concentration of treated water was 4 mg / L.

(Comparative Example 1)
In Example 1, water was passed under the conditions of a superficial velocity of 6 hr ^{−1 in} the same manner as in Example 1 except that the dissolved oxygen concentration of the raw water (17 ° C.) was 6 to 7 mg / L. The dissolved oxygen concentration of treated water became 2-3 mg / L or less, and the iron concentration of treated water became 0.5 mg / L, manganese 0.4 mg / L, and ammoniacal nitrogen 1.8 mg / L.
The processability of iron deteriorated and manganese could not be processed. Ammonia nitrogen treatment also deteriorated.

(Example 5)
As shown in FIG. 1 using a zeolite filter medium having a column diameter of 1.6 m, a filter medium packing height of 2 m, and a particle diameter of 1 to 3 mm of the packed filter medium, and having an effective diameter of 2 mm, to which microorganisms similar to Example 1 are attached. Using the biological filtration device, air was supplied to the raw water at 0.12 MPa, the dissolved oxygen concentration of the raw water (17 ° C.) was set to 9 to 11 mg / L, and the raw water was purified at a superficial velocity of 6.25 hr ^−1. went. Backwashing was performed once every three days of backwashing when the pressure increase was 0.12 MPa. The operation was performed at a dissolved oxygen concentration of 4 mg / L or more in the treated water during the purification operation.
The raw water quality is iron 2.5 mg / L, manganese 0.4 mg / L, ammoniacal nitrogen 3.8 mg / L, and the treated water quality is iron 0.03 mg / L, manganese 0.2 mg / L, ammonia It was 3.8 mg / L.

(Comparative Example 2)
In Example 5, the raw water was purified in the same manner as in Example 5 except that the operation was performed at a dissolved oxygen concentration of the raw water of 6 to 7 mg / L. Operation was performed at a dissolved oxygen concentration of treated water during the purification operation of less than 4 mg / L.
The water quality of the treated water was 0.5 mg / L for iron, 0.3 mg / L for manganese, and 3.8 mg / L for ammoniacal nitrogen.

Claims (6)

  A purification method in which at least iron, manganese, and ammonia nitrogen contain raw iron and remove manganese by biological filtration, and the raw water is adjusted so that the dissolved oxygen concentration of the treated water is 4 mg / L or more. The treated water containing ammonia nitrogen is filtered by contacting iron with microorganisms by controlling iron removal, manganese removal and nitrification so that at least ammonia nitrogen remains in the treated water. The purification method characterized by obtaining.   The purification method according to claim 1, wherein the concentration of iron and manganese in the treated water is 0.2 to 0.5 mg / L in total, and the concentration of ammoniacal nitrogen is 0.5 mg / L to 5 mg / L. .   The purification method according to claim 1 or 2, wherein a dissolved oxygen concentration of the raw water in which the oxygen is dissolved is 9 mg / L or more. A biological filtration tower packed with an oxygen dissolving step in which oxygen is dissolved in raw water so that the dissolved oxygen concentration of the obtained treated water is 4 mg / L or more, and a porous filter medium having a particle size of 1 mm to 4 mm to which microorganisms are attached. In addition, oxygen-dissolved raw water is passed at a superficial velocity of 3 hr ^{-1 to} 10.5 hr ^-1 to control iron removal, manganese removal, and nitrification by microorganisms adhering to the filter medium, and contain ammonia nitrogen. The purification method according to claim 1, further comprising a step of obtaining treated water.   A purification device for use in the purification method according to any one of claims 1 to 4, wherein an oxygen dissolving device for dissolving oxygen in the raw water so that the dissolved oxygen concentration of the treated water obtained is 4 mg / L or more; , A biological filtration tower packed with a porous filter medium having a particle size of 1 mm to 4 mm to which microorganisms are attached, and iron removal and manganese removal by microorganisms attached to the filter medium so that ammonia nitrogen remains in the treated water And a biological filtration tower for controlling nitrification.   6. The processing apparatus according to claim 5, wherein the purification device has a treated water storage tank, and the storage tank has at least one of a facility for shielding light, a UV irradiation device, an aeration device, and a circulation device. .