JPH0852497A - Treatment of phosphorus-containing organic sewage - Google Patents

Abstract

PURPOSE:To remove phosphorus, BOD, SS and ammonia at high speed and in high degree with a single vessel by adding particulates of dense iron hydroxide and/or aluminum hydroxide to a phosphorus-containing org. sewage, then introducing the sewage to a packed layer fixed with microorganisms under an aerobic condition. CONSTITUTION:A slurry 6 of dense iron hydroxide particulates having large phosphorus adsorptivity is added to the phosphorus-containing org. sewage 1 such as sewerage, and the sewage is stirred in a pipeline 10 and flowed into the packed layer 3 in an aerobic biological filter device 2 from an upper side of this device. In this case, aluminum hydroxide is exemplified as the particulates having the phosphorus adsorptivity other than the iron hydroxide. Moreover, both of the iron hydroxide and aluminum hydroxide may be used. Then, the phosphorus is adsorbed and removed quickly by the dense particulates of the iron hydroxide, etc., and SS in the sewage is captured by a biological membrane of the filter device 2 to be filtered and removed. BOD and ammonia are also removed biologically with microorganisms sticking to the filter material, and a clarified treated water 7 flowing out from a lower part of the filter device 2 is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating phosphorus-containing organic wastewater such as human waste system wastewater, industrial wastewater, and sewage.
In particular, it relates to a method for treating phosphorus-containing organic wastewater capable of removing phosphorus, SS, BOD, and ammonia in the wastewater in a single tank at a high speed and to a high degree.

[0002]

2. Description of the Related Art As one of the methods for treating organic wastewater such as sewage, there is a biological treatment method. Among these, a technique is known in which organic sewage is supplied together with air bubbles to a packed bed of granular solids such as anthracite to perform biological treatment. This method is called "Aerobic Biofiltration Method" (Biological Aerated Fil).
ter, abbreviated as BAF). BAF is B in the wastewater
OD, SS, ammonia, etc. can be highly treated in a single tank,
It is an area-saving method that is easy to maintain and manage, and is attracting attention. However, there is a big drawback that phosphorus, which has become a particularly environmental problem recently, cannot be removed.
Has become one of the factors that hinder the spread of. On the other hand, as a method for removing phosphorus in the organic wastewater, there are an activated sludge method, a method of adding an inorganic coagulant, and the like. However, although the activated sludge method could remove phosphorus to some extent, it could not stably and highly remove phosphorus. The method using an inorganic flocculant (such as calcium chloride) has caused a burden on sludge treatment because it produces coagulable sludge (including calcium phosphate) that is difficult to dehydrate.

[0003]

Therefore, an object of the present invention is to treat phosphorus-containing organic wastewater capable of removing phosphorus, BOD, SS, and ammonia in phosphorus-containing organic wastewater at high speed and highly in a single tank. To provide a method. Another object of the present invention is to provide a method for treating phosphorus-containing organic wastewater, which enables a long filtration duration, has good concentration and dewaterability of washing wastewater, and can easily treat sludge. A further object of the present invention is that the microbial membrane attached to the filter medium for biological filtration is iron hydroxide,
Another object of the present invention is to provide a method for treating phosphorus-containing organic sewage that has a small amount of SS leak into treated water because aluminum hydroxide fine particles are attached and captured.

[0004]

In order to achieve this object, the present inventor initially examined the following means. That is, BA
In this method, an inorganic coagulant such as aluminum sulfate or polyaluminum chloride is added to the sewage flowing into F to remove phosphorus by coagulation filtration. However, the flocculation flocs formed are bulky and bulky, and since a large amount is produced, the problem that the filtration layer is clogged in a short time is recognized. Further, the backwashing wastewater of the filtration layer contains a hardly dehydratable inorganic sludge, which has a drawback that it imposes a burden on the treatment and disposal of the sludge.

The present inventor has conducted further studies and found the following constitution, and was able to achieve the object. The present invention provides a packed bed of granular filler in which microorganisms are fixed under aerobic conditions after adding fine iron hydroxide and / or aluminum hydroxide fine particles prepared in advance to an organic wastewater containing at least phosphorus. It is a method for treating phosphorus-containing organic wastewater, which is characterized by being introduced into.

That is, fine iron hydroxide or aluminum hydroxide fine particles having a large phosphorus adsorption force are prepared by the method described below in advance, and the fine particles are added to the organic wastewater to be used as a filter medium instead of a physical filter layer. When it is supplied to the BAF to which is attached, phosphorus in wastewater, BOD, SS,
Ammonia can be removed at a high rate at a high rate in a single tank, the clogging of the filtration layer is significantly less than that of the method in which a coagulant is added, there is no SS leak into the filtered water, and the inorganic sludge is difficult to dehydrate. It has been found that no longer occurs.

[0007]

The structure and operation of the present invention will be described with reference to FIG. 1, which shows one embodiment of the method of the present invention. Suitable for affixing and immobilizing biofilm such as anthracite, granular activated carbon, porous ceramic granules, sponge granules (eg urethane foam granules), and spherical expanded polystyrene in the aerobic biological filter (BAF) 2. A packed bed 3 of granular solid is provided. An air diffuser 4 is installed below the packed bed 3 and air 5
Are directly supplied into the packed bed 3 as bubbles. When the organic wastewater 1 is supplied to BAF, it becomes B as a granular solid in about 2 weeks.
Microbial membranes such as OD assimilating bacteria and nitrifying bacteria are attached and immobilized.

To the phosphorus-containing organic wastewater 1 such as sewage, a slurry 6 of fine iron hydroxide fine particles having a large phosphorus adsorption power is added from a storage tank, stirred in a pipe line 10 and aerobic biological filtration device 2 is agitated. It flows into the packed bed 3 of BAF from the upper part. Here, as the fine particles having a phosphorus-adsorbing power, aluminum hydroxide may be mentioned, and both iron hydroxide and aluminum hydroxide may be used. Phosphorus is quickly adsorbed and removed by dense fine particles such as iron hydroxide, and SS in wastewater is captured by the biofilm and removed by filtration. Further, BOD and ammonia are biologically removed by the microorganisms adhering to the filter medium, and the clarified treated water 7 flowing out from the lower part of the aerobic biological filtration apparatus 2 is obtained. In the present invention, the dense iron hydroxide and / or aluminum hydroxide fine particles having such a large phosphorus adsorption effect are added to the organic wastewater, and the mixed wastewater is preferably used for the packed bed of the granular filler on which microorganisms are immobilized. Phosphorus and BO in organic wastewater by introducing gas
It becomes possible to remove D, SS and ammonia in a single tank at a high degree and at a high speed.

Since the iron hydroxide fine particles that adsorb phosphorus in the slurry 6 are dense and can be trapped in a large amount in the packed bed 3 for biological filtration, the flocculation flocs are bulky to increase the filtration resistance of the packed bed 3. Remarkably less than the coagulation filtration method,
Filterability is improved. Further, since the capacity for capturing SS such as fine particles in the filling tank 3 becomes large, the filtration duration time becomes long.
These can shorten the processing time and facilitate the maintenance of the filtration tank. On the other hand, the dense slurry 6 of iron hydroxide fine particles has significantly less adhesive force to the filter medium than flocs produced in the coagulation filtration method in which a coagulant is added, and therefore SS leaks by mere physical filtration. It has the drawback of being easy to do. However, in the case of biofiltration as in the present invention, the biofilm attached to the filling filter medium is
It has been confirmed that iron hydroxide and aluminum hydroxide fine particles having poor cohesive force are effectively trapped because they show strong adhesion to SS containing the fine particles. This is a new finding on which the present invention is based.

If the filtration treatment is continued by the above method, the filtration resistance of the packed bed will be a predetermined value (500 mmH ₂ O).
Therefore, the supply of the organic waste water 1 is stopped and the filling layer 3 is washed. The valve 11 is opened, the valve 12 is closed, and the washing water 8 is supplied from the lower part of the biological filtration device 3 and backwashed. The cleaning wastewater containing SS that has been cleaned and removed is the cleaning wastewater discharge pipe 9
Be excluded from. At this time, the iron hydroxide and aluminum hydroxide fine particles are separated from the filler by backwashing and discharged together with the washing drainage. Since the cleaning wastewater contains dense iron hydroxide or aluminum hydroxide, it was found that the concentrated dehydration was good and dehydration was easy, and a dehydrated cake with low water content was obtained, as described later. As a result, unlike the coagulation filtration method, inorganic sludge that is hardly dehydrated does not occur.

The phosphorus adsorption capacity used in the present invention is large,
The following method can be recommended as a method for producing dense iron hydroxide or aluminum hydroxide fine particles. That is, a method of neutralizing a ferrous sulfate solution and oxidizing it with air, oxygen, hydrogen peroxide, or ozone, and neutralizing a ferric sulfate or polyiron sulfate (polyiron) solution with a magnesium-based alkaline agent. And a method of neutralizing aluminum sulfate with a magnesium-based alkaline agent are preferable. A calcium-based alkaline agent is also effective in place of magnesium, but the use of magnesium produces finer particles. If NaOH is used as the alkali, dense particles will not be generated. The example shown in FIG. 1 is a method of neutralizing the polyiron 13 with magnesium hydroxide 14 in the adjusting tank 15.

The iron hydroxide and aluminum hydroxide fine particles used in the present invention have the following advantages in addition to good filterability, sedimentation concentration and dehydration. First, the phosphorus adsorption rate of iron hydroxide and aluminum hydroxide fine particles is remarkably higher than that of the conventional method of packing a column with a granular adsorbent such as activated alumina (particle diameter of about 2 to 4 mm). This means that since the aqueous solution is stirred after the addition of the fine particles, the contact ratio between the dissolved phosphorus and the iron hydroxide and aluminum hydroxide fine particles is high, and the particle size is as small as several μm, so This is because the specific surface area is extremely large.

The term "dense fine particles" as used in the present invention means that the volume per unit weight of particles is small and a high concentration of precipitated solid matter can be obtained when the particles are precipitated for a certain period of time. Specifically, the dense iron hydroxide used in the present invention,
The aluminum hydroxide fine particles have a solid concentration of 40 to 13 when precipitated in a 1 liter graduated cylinder for 30 minutes.
It has a high value of about 0 g / liter. On the other hand, the flocs produced when ferric chloride, aluminum sulfate, and other coagulants are added to sewage will inevitably become swollen particles called "bulky flocs", which have the opposite properties to "dense particles". 30 minutes Precipitated solids concentration 4-16g /
Only about a liter. The "iron hydroxide" of the present invention is used to mean hydrated iron oxide Fe ₂ O ₃ .nH ₂ O,
"Aluminum hydroxide" is used to include hydrated aluminum oxide. The amount of iron hydroxide and / or aluminum hydroxide fine particles added is 7 to 30 mg with respect to 1 mg of raw water phosphorus,
It is preferably 10 to 20 mg. Further, as a filtering method, organic sewage may be introduced from the lower part of the packed bed and filtered in an upward flow, or organic sewage may be introduced from the upper part of the packed bed and filtered in a downward flow. May be.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples, but the contents of the present invention are not limited thereto. Commercially available poly iron sulfate stock solution (iron content 11%) 1 with water
Dilute to 0 times, add magnesium hydroxide to this and p
When neutralized to H5.5, the SVI value was 11 (SVI
The value of is a very dense iron hydroxide fine particle (particle size 2) which is the volume occupied by 1 g of solid matter in the precipitate after the slurry is filled in the graduated cylinder and allowed to stand for 30 minutes. A slurry containing ˜4 μm) was obtained. After adding 20 mg / liter of this slurry as a solid substance to raw water (sewage) and mixing it, air bubbles are aerated from the lower part of a filling tank filled with cubic polyurethane foam having a particle diameter of 10 mm as a filter medium in a layer height of 2.5 m. A comparative test was conducted under two conditions: a biological method (Example) and a physical filtration method without aeration (Comparative Example). Here, the physical filtration method without aeration was performed under the same conditions as in the present invention except that aeration was not performed. The bulk density of the polyurethane foam used in this example is 0.
It was 028 g / cm ³ .

Both passed water at a filtration speed of 50 m / d.
Raw water quality is water temperature 22 ℃, SS105mg / liter, B
The OD was 120 mg / liter, the phosphorus was 2.9 mg / liter, and the ammonia was 31 mg / liter. In the physical filtration method, since the filter medium is free of microorganisms, S
About 14 to 18 mg / liter of S leaked. Also, B
The OD removal rate was 30% and the ammonia removal rate was 0%. Furthermore, the phosphorus removal rate was 72%. On the other hand, in the biological filtration method, after 2 weeks, the microorganisms are sufficiently attached to the filter medium, and the filtered water obtained after that becomes clear and SS2 mg / liter,
Treated water containing 0.08 mg of phosphorus, 2 mg of BOD, and 8 mg of ammonia was obtained.
At this time, the amount of microorganisms attached to the filter medium was as high as 16 g / liter per 1 liter of the filter medium filled. Treated water SS
The filtration duration time before deterioration to 10 mg / liter was 70 to 75 hours, which was long. The filtration resistance at this point was only 40 mmH ₂ O. The concentration and dewatering property of the backwash water of the filter tank is good, the sludge concentration after sedimentation for 120 minutes is 4.8%, and the water content of the dewatered cake by the belt press is 73%.
It was a small percentage. Here, the backwash was performed once for 48 hours.

[0016]

The following effects can be obtained by the method of the present invention. 1. Phosphorus, BOD, SS, and ammonia can be removed at high speed and highly in a single tank. 2. Dense iron hydroxide and aluminum hydroxide, which have a large phosphorus adsorption power, are prepared in advance and added to the raw water, so that the filtration duration is long, the concentration and dewatering property of the washing drainage are good, and the sludge treatment is easy. 3. Since the biofilm attached to the filter material for biological filtration adheres and captures iron hydroxide and aluminum hydroxide fine particles, SS leak into the treated water is small.

[Brief description of drawings]

FIG. 1 is a process drawing showing one embodiment of the method of the present invention.

[Explanation of symbols]

 1 Organic Sewage 2 Aerobic Biological Filtration Device 3 Filling Tank 4 Air Diffuser 5 Air 6 Iron Hydroxide Slurry 7 Clarified Water 8 Cleaning Water 9 Drainage Pipe 10 Pipeline 11 Valve 12 Valve 13 Poly Iron 14 Magnesium Hydroxide 15 Preparation Tank

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C02F 3/06 ZAB

Claims (1)

[Claims] 1. Filling a granular filler in which microorganisms are fixed under aerobic conditions after adding fine iron oxide and / or aluminum hydroxide fine particles prepared in advance to an organic wastewater containing at least phosphorus. A method for treating phosphorus-containing organic wastewater, which comprises introducing the organic wastewater into a layer.