JP2006136752A - Method for treating water containing suspended solid, inorganic-state nitrogen and phosphorus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a method for treating water containing suspended solids, inorganic-state nitrogen and phosphorus, in which oxidized nitrogen can be removed/decreased efficiently by sulfur denitrification being a biological reaction without being affected by suspended solids hindering a solid denitrifying substrate from exhibiting its good result and phosphoric acid and ammonia nitrogen can also be decreased easily at the same time by the action of magnesium hydroxide. <P>SOLUTION: The water containing suspended solids, inorganic-state nitrogen and phosphorus is made to pass through a pretreatment tank 1 packed with a lightweight granular material 2 and successively through a multiple treatment tank 3 packed with another lightweight granular material 4 whose surface is coated with the denitrifying substrate consisting of sulfur and an alkaline substance so that the suspended solids, inorganic-state nitrogen and phosphorus contained in the water are removed/decreased. In order to induce the denitrifying substrate to surely exhibit its good result over a long period of time, the multiple treatment tank is backwashed suitably and magnesium hydroxide is added to the multiple treatment tank so that the pH of the water to be treated becomes 8-8.5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, after normal biological treatment such as activated sludge method for livestock sewage and food processing wastewater, inorganic nitrogen and phosphorus are efficiently added while minimizing the influence of some suspensions. The present invention relates to a method for treating inorganic nitrogen / phosphorus-containing water accompanied by a suspended substance used for reducing and removing the environment where the treated water is discharged.

  Emission regulations related to inorganic nitrogen such as nitrate nitrogen by the Water Pollution Control Law and others have been strengthened year by year, but the harsh management environment and practical and simple inorganic nitrogen removal technology have been established for the livestock industry. Temporary emission standards have been applied because they are not.

  However, even if it is limited to pigs, about 9.7 million heads are fattened nationwide, and the sewage sewage mainly from urine is highly treated. Since July 2004, at least nitrate nitrogen and nitrite When the total of the numerical values obtained by multiplying the concentration of ammonia nitrogen by 0.4 in addition to the concentration of nitrogen needs to be 900 mg / L or less, and depending on the region, it is required to purify to 60 mg / L or less as total nitrogen There is also.

  In the activated sludge method, which is introduced relatively frequently at livestock sewage treatment sites, nitrogen compounds in livestock sewage can be easily mineralized and oxidized to nitrate nitrogen by the control method. However, livestock sewage has a BOD / N ratio. In many cases, the denitrification tends to be insufficient. Under such circumstances, it is considered that a method using sulfur denitrifying bacteria, which is a kind of autotrophic bacteria, is suitable for efficiently removing nitrate nitrogen, and various methods have been proposed (Patent Documents 1 and 2). .

  They basically use a composition for imparting microbial activity (Patent Document 3), which was developed and proposed by one of the present inventors to uniformly disperse a required amount of calcium carbonate in a sulfur matrix as a denitrification substrate. If used, it is possible to accurately neutralize sulfate ions produced with sulfur denitrification and to suppress a decrease in pH.

  In addition to removing nitrate nitrogen by sulfur denitrification, the inventors also developed an innovative method for simultaneous reduction and recovery of ammonia nitrogen and phosphorus by adding magnesium hydroxide to the denitrification substrate. It has been proposed (Patent Document 4).

  However, the treated water of livestock sewage by the activated sludge method usually contains a suspension. Even if the suspension is removed almost completely by membrane filtration or the like, for example, sulfur denitrification is subsequently performed. For example, sulfur-oxidizing bacteria and the like grow and gypsum fine particles and the like as neutralizing substances are also generated, so that they block the particles of the denitrification material and reduce the denitrification efficiency. To prevent this, regular backwashing is effective, but conventional sulfur denitrification materials have not been easy to backwash from the viewpoint of density and particle size.

  Thus, a material (Patent Document 5) using the composition of Patent Document 3 that has a relatively low bulk specific gravity and is capable of reducing the particle diameter has been proposed. In this material, an organic component contained as a binder is proposed. The generation of suspensions may be promoted by decomposition of the liquid, and the shape of the process is not spherical but cylindrical, and the possibility of fine particles due to wear is also predicted. Not ideal.

  Moreover, ammonia nitrogen often remains in livestock sewage treated water such as activated sludge by nitrification-driven operation, and phosphoric acid always remains, so the influence of coexisting suspensions was minimized. A simple and effective method for simultaneous removal and reduction of inorganic nitrogen and phosphorus is desired in many fields.

  Various methods have been proposed for simultaneous removal of nitrogen and phosphorus (Patent Documents 6 to 13). However, these methods require a separate process for removing nitrogen and phosphorus, dosing or heating.・ Requires pressurization, complicated management when applied to actual wastewater, depends on specific bacteria for both denitrification and phosphorus removal, complicated process, and included in treated water There are many cases where there is a problem in practical use in the field of livestock, such as the necessity of adding an agglomerate that matches the concentration of phosphorus, or the life of the removal material is short, especially in the medium and small scale livestock field Applicability is poor.

The method of Patent Document 4 proposed and developed by the present inventors also requires a separate device for maintaining the high pH necessary for denitrification efficiency and phosphoric acid removal in the presence of suspension.
JP 2003-71491 A JP 2003-334590 A JP-A-11-285377 Japanese Patent Application No. 2003-332479 JP 2004-174328 A Japanese Patent Laid-Open No. 2004-237170 JP 2003-200199 A JP-A-6-23390 JP 2003-285096 A JP 2001-179295 A JP 2003-71454 A JP-A-8-103787 JP-A-11-239785

  The present invention suppresses adverse effects due to suspended solids from treated water such as livestock sewage by an activated sludge method, etc., and suppresses nitrate nitrogen by sulfur denitrification in a good environment. And a method for treating inorganic nitrogen / phosphorus-containing water with a suspension capable of easily and reliably reducing phosphoric acid and ammonia nitrogen in a good environment simultaneously with efficient removal of nitrite nitrogen and nitrogen The purpose is to provide.

  The invention according to claim 1 of the present invention introduces water to be treated containing inorganic nitrogen and phosphorus together with a suspension to a combined treatment tank filled with a filter medium that contributes to the reduction of inorganic nitrogen and phosphorus, It is characterized by removing or reducing inorganic nitrogen and phosphorus while filtering the coexisting suspension through the filter medium, and discharging the suspension and insoluble phosphorus intermittently accumulated in the combined treatment tank by backwashing. To do.

  In the invention according to claim 2, the water to be treated containing inorganic nitrogen and phosphorus together with the suspension is introduced into a pretreatment tank filled with a pretreatment filter medium to reduce the suspension, and then inorganic. Water is introduced into a combined treatment tank filled with filter media that contributes to the reduction of nitrogen and phosphorus.

  According to a third aspect of the present invention, the pretreatment filter medium is a lightweight granular material, a filter medium that contributes to the reduction of inorganic nitrogen and phosphorus in the composite treatment tank, or denitrification substrate consumption after being used in the composite treatment tank It is characterized by comprising a filter medium with reduced denitrification effect.

  The invention according to claim 4 is a pretreatment of the filter medium having a reduced denitrification effect, wherein the filter medium for pretreatment comprises a filter medium having a reduced denitrification effect due to denitrification substrate consumption after being used in the combined treatment tank. 4. The method for treating inorganic nitrogen / phosphorus-containing water with a suspension according to claim 3, wherein the pretreatment tank and the main treatment tank are reversed to pass water when used as a filter medium.

  According to the fifth aspect of the present invention, when the phosphorus reduction effect of the filter medium contributing to the reduction of inorganic nitrogen / phosphorus in the combined treatment tank is reduced, the magnesium hydroxide powder / powder is added within a range in which denitrification can be maintained. It is characterized by adding.

  The invention described in claim 6 is characterized in that the filter medium that contributes to the reduction of inorganic nitrogen and phosphorus is a granular material obtained by coating and adhering a mixture of sulfur and an alkaline substance on the surface of a lightweight granular material.

  The invention according to claim 7 is characterized in that the lightweight granular material is pearlite.

  The invention according to claim 8 is characterized in that the alkaline substance is calcium carbonate and / or magnesium hydroxide.

  According to the method for treating inorganic nitrogen / phosphorus-containing water with a suspension according to the present invention, nitric acid in the presence of a suspension such as livestock wastewater treated water such as piggery sewage or treated wastewater from food factory wastewater. Water can be purified easily and effectively, and it also contributes to the improvement of appearance such as chromaticity. .

The treated water that is the treatment target of the present invention is livestock wastewater such as swine sewage, food factory wastewater, and biologically treated water obtained by normal biological treatment of these in the presence of suspensions of nitrate nitrogen. Water to be treated containing inorganic nitrogen containing nitrite nitrogen and ammonia nitrogen and phosphorus such as phosphate phosphorus. Such treated water contains, for example, a relatively large amount of a substance that can be a carbon source for sulfur denitrifying bacteria, and it is not necessary to use a large amount of a substance that can be a carbon source such as calcium carbonate.
In the method for treating inorganic nitrogen / phosphorus-containing water with a suspension according to the present invention for treating such treated water, the treated water containing inorganic nitrogen and phosphorus together with the suspension is treated with inorganic nitrogen.・ Water is introduced to the combined treatment tank filled with filter media that contributes to the reduction of phosphorus, and suspensions are reduced to minimize the effects of suspensions coexisting in the water to be treated and accumulated in the tank. It is basically based on the fact that effective removal and reduction of inorganic nitrogen and phosphorus are mainly performed in the combined treatment tank by discharging turbid matter and insoluble phosphorus by back washing appropriately.

In this method, as the filter medium of the composite treatment tank, granular, powdery, powdery, and massive materials can be used, and as this material, alkaline substances and sulfur developed by one of the inventors of the present invention can be used. It is desirable to use a composition for removing nitrate nitrogen or the like (see Japanese Patent Application Laid-Open No. 2003-71493) comprising a composition obtained by coating and / or impregnating light specific gravity porous particles on the core.
As the light-weight granular material that is the core, so-called perlite, nacre, minestone, pumice, shirasu balloons, etc. obtained by heat treatment of pearlite, lightweight ceramic, glass foam, etc. can be used. As the alkaline substance constituting the denitrification substrate, calcium carbonate, magnesium hydroxide, dolomite, limestone, aluminum hydroxide, lightweight cellular concrete (ALC) powder, powder particles, and fine particles can be used. If calcium carbonate and magnesium hydroxide are used, it is excellent in denitrification of oxidized nitrogen by an autotrophic denitrification method using sulfur-oxidizing bacteria, and ammonia nitrogen and phosphorus can be removed.

  Furthermore, it is preferable to use a natural mineral brucite (water talc) or a crushed and crushed rock containing the same as a main constituent mineral as magnesium hydroxide powder and powder, but other sources such as seawater and chemical synthesis Even magnesium hydroxide can be used.

As such a material, particles having a particle diameter of about 3 to 6 mm are preferable, and even a plurality of particles that are welded and enlarged can be used. The particle size of the alkaline substance in the particles is preferably about 0.1 mm or less, and the particle size of the light specific gravity porous granule is preferably about 2 to 5 mm.
The bulk specific gravity of this material is preferably 0.6 to 0.9 g / cm ³ . Since the particles of this material have hydrophilic properties, when processing the water to be treated, it settles with water and realizes a good treatment, and at the time of backwashing, it floats easily and performs backwashing. This is because simple processing can be easily realized.
The shape of the particles is preferably close to a sphere. This is because if it is spherical, the filtration performance is improved, and the number of backwashes is easily reduced.

In order to treat the water to be treated using such materials, the composite treatment tank is filled with the materials, and the water to be treated is introduced from, for example, the top side of the composite treatment tank, and various conditions such as HRT are appropriately selected. The water to be treated can be treated, for example, by passing the water in a downward flow and discharging the treated water from the bottom side.
In this treatment, for example, the pH of the treated water after treatment is preferably in the range of 8.0 to 8.5. In such a pH range, it is easy to ensure phosphorus removal ability and easy removal of nitrate nitrogen, and also a tendency to suppress or decrease the increase in nitrite nitrogen was also observed. .

  During this treatment period, the suspended matter in the water to be treated is filtered by the filter medium, and the solid content formed by the growth of sulfur-oxidizing bacteria or the production of gypsum fine particles is also filtered. Captured. Therefore, it is preferable to continue the treatment while intermittently backwashing the filter medium regularly or irregularly.

  According to such treatment of water to be treated, the combined treatment tank can efficiently remove nitrate nitrogen, nitrite nitrogen, ammonia nitrogen, and phosphoric acid simultaneously and filter the suspension. It is possible to improve the appearance such as chromaticity. Therefore, the treatment of water to be treated can be simplified by a simple treatment method. Moreover, if the predetermined materials as described above are used, it is possible to easily maintain the function of the filter medium by backwashing, and it is possible to easily suppress the influence of the suspended matter and smoothly perform the inorganic state over a long period of time. Nitrogen and phosphoric acid can be removed and reduced.

  In the method of the present invention, in order to reliably suppress the influence of the suspended solids and smoothly remove and reduce inorganic nitrogen and phosphoric acid over a long period of time, water is introduced into the pretreatment tank filled with the pretreatment filter medium and suspended. It is also preferable to introduce water into the combined treatment tank after reducing the turbidity.

The pretreatment filter medium filled in the pretreatment tank is not particularly limited as long as it can remove the suspended matter, but a granular material is preferably used as the filter medium. Examples of such materials include so-called perlite obtained by heat treatment of pearlite, pearlite, minestone, pumice, and shirasu balloons, lightweight ceramics, glass foam, ALC grains, water treatment plant soil Processed products, processed products of volcanic ash-derived soil such as Kanuma soil, and the like can be used.
As this material, it is preferable to use a material having a bulk specific gravity of 0.3 to 0.9 g / cm ³ . Here, since the particles of the material have a hydrophilic property, when processing the water to be treated, it contains water and settles, exhibits a filtering function, and floats easily during backwashing. Because it can be done.

  Here, it is particularly preferable to use the same material as that used as the filter medium of the combined treatment tank, or a material having a reduced denitrification effect due to denitrification substrate consumption after being used in the combined treatment tank. The material having a reduced denitrification effect due to the denitrification substrate consumption is a material in which a sufficient denitrification effect cannot be obtained.For example, an alkaline substance and sulfur are coated with light specific gravity porous particles on the core. In the case of a composition for removing nitrate nitrogen or the like comprising an impregnated composition, sulfur on the surface of the light specific gravity porous granule is obtained by being subjected to treatment for a long period of time or by being subjected to repeated backwashing and the like. The denitrification substrate represented by calcium carbonate is consumed or the denitrification substrate is peeled off, and as a result, a desired denitrification rate cannot be obtained. This occurs after repeated recovery of the phosphorus removal ability to which magnesium hydroxide is added, which will be described later, and after long-term use.

If such a material is used as a filter medium for pretreatment, not only is it easy to perform backwashing with an appropriate specific gravity, but also a slight denitrification action remains, improving the denitrification effect of the entire device. It is also possible to make it.
In addition, if this is done, the types of materials used in the combined treatment tank and the pretreatment tank can be reduced, and waste of materials can be suppressed.
In this way, after reducing the suspension in advance by the pretreatment tank, if the water to be treated is introduced into the composite treatment tank, the amount of the suspension trapped in the filter medium of the composite treatment tank can be suppressed, It is easy to maintain the water permeability of the filter medium. This is preferable because it reduces the number of times of backwashing and can suppress deterioration due to wear of the filter medium due to backwashing.

Furthermore, in the method of the present invention, when the influence of the suspension is more reliably suppressed and inorganic nitrogen and phosphoric acid are removed and reduced smoothly over a long period of time, the coating containing the inorganic nitrogen and phosphorus together with the suspension is used. The treated water is introduced to the pretreatment tank filled with the pretreatment filter medium and then to the combined treatment tank filled with filter medium that contributes to the reduction of inorganic nitrogen and phosphorus, and the suspension is reduced in the pretreatment tank. Removal of inorganic nitrogen and phosphorus with minimal effect of suspended solids, mainly in the combined treatment tank, and denitrification of filter media contributing to the reduction of inorganic nitrogen and phosphorus filled in the combined treatment tank When the denitrification effect decreases due to substrate consumption, the pretreatment tank is newly filled with filter media that contributes to the reduction of inorganic nitrogen and phosphorus in place of the pretreatment filter medium. Perform the operation that reverses the combined treatment tank, After can minimize repetition, and suspension accumulated in intracisternal and the effect of suspension coexisting water to be treated by draining by suitably carried backwash phosphorus insoluble it.
In this way, the filter medium made of the material deteriorated in the combined treatment tank can be used as the pretreatment filter medium without being moved, and the workability is very good and suitable.

  In the method of the present invention, in any of the above cases, when the phosphorus reduction effect of the filter medium that further contributes to the reduction of inorganic nitrogen and phosphorus is reduced, magnesium hydroxide to the extent that does not prevent denitrification to the combined treatment tank By adding the powder / particles, the phosphorus removal performance can be maintained and recovered.

The surface of this magnesium hydroxide is carbonated due to consumption by dissolution, carbonate ions contained in the water to be treated, etc., and its alkalinity tends to decrease. Therefore, it is easy to run out by continuing the treatment of the water to be treated. Therefore, in the method of the present invention, magnesium hydroxide is added at the time when the phosphorus reduction effect is lowered, regardless of whether magnesium hydroxide is present in the combined treatment tank.
Furthermore, when this magnesium hydroxide is added in a large amount, the pH is excessively increased, and the denitrification ability may be lowered or invalidated. Therefore, in this invention, it is necessary to add to the extent which does not prevent denitrification.
Here, it is preferable to add magnesium hydroxide as powder / powder for the reason that the contact area with the water to be treated can be increased, but there is also a concern that it will flow out of the combined treatment tank during backwashing. However, in the present invention, by using a filter medium made of the above-mentioned materials for the composite treatment tank, it is easy to ensure filtration performance, and therefore the number of backwashes can be reduced. Moreover, since magnesium hydroxide has a higher specific gravity than the suspension, it tends to stay in the filter medium of the combined treatment tank. Therefore, the addition of magnesium hydroxide makes it possible to fully exhibit the effect.

As an index for determining that the phosphorus reduction effect has decreased, for example, the phosphoric acid concentration in the treated water discharged from the combined treatment tank may be used, but the pH of the treated water can be used. For example, it may be determined that the phosphorus reduction effect is reduced by reaching pH 8 or lower as this pH.
And, when adding magnesium hydroxide powder / grains, if it is added excessively, the pH will rise too much, and the activity of the bacteria will decrease and the denitrification ability tends to decrease. For example, magnesium hydroxide It can be added so that the pH of the treated water discharged from the combined treatment tank in the state where the powder / powder is added is maintained in the range of 8 to 8.5, and it is also preferable to add in multiple times.

Next, an example of the processing apparatus for processing to-be-processed water by the method of this invention is demonstrated.
As the processing apparatus, an apparatus (example) as shown in FIG. 1 can be used. In FIG. 1, reference numeral 1 is a pretreatment tank, 2 is a pretreatment filter medium, 3 is a composite treatment tank, 4 is a filter medium that contributes to the reduction of inorganic nitrogen and phosphorus, 5 is magnesium hydroxide powder, and 6 is water to be treated. , 7 indicates treated water. However, it is not limited to this embodiment.

In such a processing apparatus, first, the above-described materials are filled as the pretreatment filter medium 2 in the pretreatment tank 1 and the filter medium 4 contributing to the reduction of inorganic nitrogen and phosphorus in the composite treatment tank 3. Then, as shown by a solid line in FIG. 1, the water 6 to be treated is passed from the preliminary treatment tank 1, then passed to the combined treatment tank 3, and the treated water 7 is discharged from the combined treatment tank 3. Process by.
During this treatment period, in the preliminary treatment tank 1 and the composite treatment tank 3, a backwash operation is performed intermittently or regularly using a backwash device or an aeration device (not shown) to maintain the processing capacity. . Further, when the effect of reducing phosphorus in the treated water 7 is lowered, the treatment is continued by adding the magnesium hydroxide powder 5 to the combined treatment tank 3.

Then, when the effect of reducing the inorganic nitrogen of the filter medium 4 that contributes to the reduction of inorganic nitrogen and phosphorus is reduced, and the desired denitrification rate cannot be obtained, the pretreatment filter medium 2 is extracted from the pretreatment tank 1. Then, after the pretreatment tank 1 is newly filled with the filter medium 4 that contributes to the reduction of inorganic nitrogen and phosphorus, an operation of reversing the pretreatment tank 1 and the composite treatment tank 3 is performed. That is, the pretreatment tank 1 is a composite treatment tank 3 ′, and the composite treatment tank 3 is a pretreatment tank 1 ′. At this time, the pretreatment filter medium 2 filled in the composite treatment tank 3 ′ is discarded and filled with a filter medium 4 ′ that contributes to the reduction of new inorganic nitrogen and phosphorus. Further, the filter medium 4 that contributes to the reduction of inorganic nitrogen and phosphorus filled in the pretreatment tank 1 ′ is left in the filled state, and this filter medium 4 is used as the pretreatment filter medium 2 ′.
In this state, as shown by a chain line in FIG. 1, the water to be treated 6 ′ is passed from the pretreatment tank 1 ′ and then passed to the combined treatment tank 3 ′, and the treated water 7 ′ is subjected to the combined treatment. Processing is performed by discharging from the tank 3 '. In this apparatus, it is possible to perform processing continuously for a long time by repeating such an operation.
In addition, the pretreatment filter medium 2 to be discarded after use can be used for other purposes thereafter. In the case of pearlite, it should be used effectively as a secondary material for compost production or a soil conditioner. Is also possible.

  In such an apparatus, the method for treating inorganic nitrogen / phosphorus-containing water with a suspension according to the present invention coexists with suspensions such as livestock wastewater treated water such as piggery sewage and treated wastewater from food factory wastewater. Since inorganic nitrogen and phosphoric acid are effectively removed from the water to be treated and contribute to water environment conservation at the discharge destination, it is suitable for treatment of inorganic nitrogen / phosphorus-containing water accompanied by suspension.

  In order to confirm the effectiveness of inorganic nitrogen / phosphorus-containing water treatment with the suspension described above, the apparatus shown in FIG. 1 (Example) was created as the present invention, and the livestock grassland research located at Ikedadai Tsukuba City Ibaraki Prefecture A test was conducted using a liquid obtained by biologically treating actual sewage in a pig farm. In this example, the operation in which the combined treatment tank 3 and the preliminary treatment tank 1 were reversed was not performed.

  A pretreatment tank 1 having a capacity of 5 liters and a main treatment tank 3 having a capacity of 5 liters were provided.

  Pearlite pearlite (manufactured by Taiheiyo Pearlite Co., Ltd.): 0.5 liter (layer thickness 100 mm) as pretreatment filter medium 2; Pearlite pearlite (Pacific Perlite Co., Ltd.) as filter medium 4 that contributes to the reduction of inorganic nitrogen and phosphorus (Made by Hosoi Chemical Co., Ltd.): 37% by weight, calcium carbonate (made by Nichetsu Co., Ltd.): 18.5% by weight, magnesium hydroxide (made in China): 44.5% by weight Applying 0.5 liters (layer thickness 100 mm) of material having a particle size of 2 to 25 mm with powder particles coated and coated, and adding a sample (produced in China) with an average particle size of 10 μm as magnesium hydroxide powder 5 Water to be treated shown in Table 1 was introduced into the pretreatment tank 1 and then to the main treatment tank 3 by a metering pump under conditions of HRT 2.5 hours and a treatment water temperature of 20 ° C.

  As a comparative example, in a single treatment tank, sulfur (manufactured by Hosoi Chemical Industry Co., Ltd.): 35% by weight, calcium carbonate (manufactured by Nichetsu Co., Ltd.): 45% by weight as a filter medium contributing to the reduction of inorganic nitrogen and phosphorus. Magnesium hydroxide (produced in China): To-be-treated water having the water quality shown in Table 1 was passed through 3 liters of a mixture consisting of 20% by weight and having a particle diameter of 5 to 20 mm under conditions of HRT for 36 hours and a treatment water temperature of 20 ° C.

The test results were as shown in Table 2 and FIGS. Table 2 shows the purification effect of the comparative example, and FIGS. 2 to 6 show the purification effect of the example.
FIG. 2 shows changes in the removal rate of oxidized nitrogen, nitrate nitrogen, and inorganic nitrogen, that is, nitrogen removal ability in Examples. FIG. 3 shows the relationship between raw water (treated water) pH and nitrite nitrogen increase. FIG. 4 shows the removal rate of phosphate phosphorus, that is, the change in phosphate removal ability, and the recovery effect of phosphate removal ability by adding magnesium hydroxide. FIG. 5 shows the relationship between treated water pH and phosphate removal ability. FIG. 6 shows the effect of removing suspended suspension (SS) by pretreatment using pearlite.
In addition, all of oxidized nitrogen (nitric acid, nitrous acid) and ammoniacal nitrogen are included in Table 2 and FIG. 2 as inorganic nitrogen.

The purification effect by the comparative example is as shown in Table 2, and the suspended suspension (SS) did not show the purification effect as specially noted, but it was tested for the removal rate of nitrate-like (nitrate state) nitrogen. The value of 0.10 kg / m ³ / day was the smallest and good throughout the period of 130 days.

  However, in the comparative example, after 20 days from the start of the test, the removal rate of nitrite nitrogen and ammonia nitrogen suddenly decreases, and the concentration of phosphate phosphorus exceeding the test water may be contained in the treated water. there were. The reduction in the removal effect was observed when the treated water had a pH of 8 or less. Unlike the recovery of nitrate nitrogen removal by backwashing, the pH was increased and ammonia was removed even after backwashing. There was almost no recovery of the removal effect of basic nitrogen and phosphate phosphorus.

In contrast, in the examples, the nitrogen removal ability tended to gradually decrease after 80 days from the start of the test. However, if the concentration of nitrite nitrogen in the water to be treated was 0.2 kg / m ³ / day or less, HRT2 Even at 5 hours (HRT of the comparative example was 36 hours), the nitrogen removal ability was 0.3 kg / m ³ / day or more, which was clearly superior to the comparative example (see FIG. 2). In the latter half of the test, the raw water (treated water) has a pH of 7.6 or less in many cases. In such a case, a relatively large amount of nitrite nitrogen is contained, and 0.1 kg / m ³ / day or more. In many cases, the value of was shown (see FIG. 3).

Further, in the examples, after the 50th day when the treated water pH became 8.0 or less, an operation such as backwashing was performed, but the recovery of the pH and phosphate removal ability was not expected, and from the 68th day to the 84th day. When 30 g of magnesium hydroxide was added in 7 portions from the top of the treatment tank 3, the treated water pH recovered to 8.0 or more, and at the same time, the phosphate removal ability also recovered to 0.1 kg / m ³ / day or more. It was clearly superior to the comparative example (see FIGS. 4 and 5).

  Further, in the examples, the SS in the water to be treated (raw water) was 119 to 169 mg / L, which was reduced to 8 to 10 mg / L by the pretreatment, and 91.6 wt% to 95.3 wt%. The removal rate was shown (see FIG. 6). Although the results up to the fifth day are shown in FIG. 6, the same filtration effect as that until the fifth day is maintained continuously and satisfactorily by performing appropriate backwashing using the increase in filtration resistance as an index during the test period. did.

  In addition, when the treated water pH was 8.0 or more, not only the phosphate removal ability was maintained, but also the accumulation and generation of nitrite nitrogen tended to be suppressed. It was also suggested that the decrease in the ability to remove oxidized nitrogen due to the remaining nitrite nitrogen found in nitrogen can be suppressed (see FIGS. 3 and 5).

  In addition, although it is a visual comparison, the treated water of the Example has improved color tone compared to the comparative example as well as the raw water (treated water).

  By the way, the filter medium after diverted as a pretreatment filter medium after being used as a denitrification filter medium is almost consumed for the sulfur content on the surface, but insoluble phosphorus, nitrogen, and magnesium components may be deposited on the surface. Yes, if the filter medium is mainly pearlite, it is recognized as a legal soil improvement material and is recognized as a good secondary material in composting, so the circulation of fertilizer components contained in pearlite and treated water, etc. It can be a promising recycling material in terms of use.

  In addition, this invention is not limited to the form of implementation (Example) mentioned above.

It is explanatory drawing which shows the processing apparatus of the inorganic nitrogen and phosphorus containing water with the suspension which concerns on the Example of this invention. It is a graph which shows the change of the removal rate, ie, nitrogen removal ability, of the oxidation nitrogen in the Example of this invention, nitrate nitrogen, and inorganic nitrogen. It is a graph which shows the relationship between raw | natural water (treated water) pH and the amount of nitrite nitrogen increase in the Example of this invention. It is a graph which shows the removal effect of the phosphate phosphorus in the Example of this invention, ie, the change of phosphate removal ability, and the recovery effect of phosphate removal ability by addition of magnesium hydroxide. It is a graph which shows the relationship between the treated water pH and phosphoric acid removal ability in the Example of this invention. It is a graph which shows the removal effect of the suspended suspension (SS) by the pretreatment using the pearlite in the Example of this invention.

Explanation of symbols

1, 1 'Pretreatment tank 2, 2' Pretreatment filter medium 3, 3 'Combined treatment tank 4, 4' Filter medium contributing to reduction of inorganic nitrogen and phosphorus (denitrification filter medium)
5, 5 'Magnesium hydroxide powder 6, 6' Water to be treated (raw water)
7, 7 'treated water

Claims (8)

Water to be treated containing inorganic nitrogen and phosphorus together with the suspension is introduced to the combined treatment tank filled with filter medium that contributes to the reduction of inorganic nitrogen and phosphorus, and the coexisting suspension is filtered by the filter medium. Inorganic nitrogen / phosphorus content with suspension, which removes or reduces inorganic nitrogen and phosphorus, and intermittently accumulates suspension and insoluble phosphorus in composite treatment tanks by backwashing Water treatment method. Water to be treated containing inorganic nitrogen and phosphorus along with the suspension is introduced into a pretreatment tank filled with pretreatment filter media to reduce the suspension, and subsequently contribute to the reduction of inorganic nitrogen and phosphorus. The method for treating inorganic nitrogen / phosphorus-containing water with a suspension according to claim 1, wherein water is introduced into a combined treatment tank filled with a filter medium. The pretreatment filter medium is a lightweight particulate material, a filter medium that contributes to the reduction of inorganic nitrogen and phosphorus in the composite treatment tank, or a filter medium with reduced denitrification effect due to denitrification substrate consumption after being used in the composite treatment tank The method for treating inorganic nitrogen / phosphorus-containing water with a suspension according to claim 2. The pretreatment filter medium is composed of a filter medium having a reduced denitrification effect due to consumption of the denitrification substrate after being used in the combined treatment tank. When the filter medium having a reduced denitrification effect is used as a pretreatment filter medium, the pretreatment tank The method for treating inorganic nitrogen / phosphorus-containing water with a suspension according to claim 3, wherein water is passed through the treatment tank in reverse. The magnesium hydroxide powder / powder is added within a range in which denitrification can be maintained when the phosphorus reduction effect of the filter medium contributing to the reduction of inorganic nitrogen / phosphorus in the combined treatment tank is reduced. A method for treating inorganic nitrogen / phosphorus-containing water with the suspension according to any one of 1 to 4. 6. The filter medium that contributes to the reduction of inorganic nitrogen and phosphorus is a granular material in which a mixture of sulfur and an alkaline substance is coated and attached to the surface of a light-weight granular material. A method for treating inorganic nitrogen / phosphorus-containing water with a suspension described in 1. The method for treating inorganic nitrogen / phosphorus-containing water with a suspension according to claim 6, wherein the lightweight granular material is pearlite. The method for treating inorganic nitrogen / phosphorus-containing water with a suspension according to claim 6 or 7, wherein the alkaline substance is calcium carbonate and / or magnesium hydroxide.

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