JPH07115022B2 - Sewage purification method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application and prior art] The present invention further purifies sewage, primary and secondary treated water of sewage, and domestic wastewater to sewage to a higher degree using soil. The present invention relates to improvement of a sewage purification device using a soil purification method and a soil purification principle.

The ideal sewage purification method is SS content, BOD and COD in sewage.
Not only adsorbing, decomposing and removing organic matter such as ammonia, ammonia and deodorizing, but also efficiently removing nitrogen and phosphorus in quality and quantity, and having a sufficient service life (for example, 10 years or more) Can be said to be. However,
The sprinkling filter method and the activated sludge method, which have been widely used in Japan, consume a large amount of energy and also produce odorous components, phosphorus, and
Almost ineffective in removing nitrogen.

Therefore, recently, a soil purification method that efficiently removes deodorant and phosphorus and nitrogen components has been in the spotlight. It actively utilizes the digestion / decomposition function of soil animals and soil microorganisms and the adsorption function of soil colloid, and is excellent in energy saving and cost saving. However, the soil treatment methods currently in use are not completely ideal. This is because although the various conditions required for soil are inconsistent as it is an ideal sewage purification method, those conditions have not been sufficiently considered or examined.

[Problems of conventional technology]

That is, in the soil purification method, in order to efficiently decompose and remove SS components, BOD and COD components, ammonia and other organic substances, and deodorize or nitrify, treat them while enhancing aerobic biological activity in well-ventilated soil. Need to do. For this purpose, coarse-grained and well-ventilated soil like Masa soil is suitable,
In Masa soil, it is difficult to remove nitrogen as well as phosphorus efficiently in the long term.

First, in order to remove phosphorus (orthophosphoric acid and polyphosphoric acid), it is indispensable that active aluminum (in some cases, active iron) is present in the soil. Is extremely small. Usually, it is 0.1% or less per dry soil weight. (Here, of the components in the soil, aluminum and iron soluble in 0.15M sodium oxalate-oxalic acid mixture (pH 3.5) are defined as active aluminum and active iron, respectively.) It is usual that the purifying device, which is the main constituent, halves the ability to remove phosphorus within 1-2 years.

On the other hand, soils with high active aluminum content are humic or non-humic volcanic ash soils, brown or tan forest soils,
Red-yellow soils, gray or brown lowland soils, etc., which generally have a high clay content and are inferior in air permeability and water permeability.
Therefore, these have a fatal defect that when they are filled with fine particles in a purification device, they are apt to be clogged and the sewage load cannot be increased.

Next, in order to remove the nitrogen content, nitrification or nitration of ammonia nitrogen under aerobic conditions, followed by denitrification reaction (N ₂
And N ₂ O generation and volatilization). For this purpose, aerobic and anaerobic soils must coexist.

As can be seen from the above consideration, the properties that the soil in the wastewater purification device should have can be summarized into the following three points.

Permeability is high enough. From the viewpoint of effective use of land, the daily treatment capacity of sewage is required to be 100 to 200 l / m ² or more.

High phosphorus removal capacity. Assuming that the average load of total phosphorus concentration is 5 mg / l and the removal rate is 95% or more and the service life is 10 years with a loading of 200 l / m ² / day, the amount of active aluminum is 1 When the adsorption efficiency of phosphorus is 25% at 1: 1, 15 kg / m ² or more is required. Therefore, if the provisional specific gravity of the filled soil is 0.8 g / cm ³ and the thickness of the soil layer is 1.5 m, it is sufficient to use soil with an active aluminum content of 1.25% or more. Kuroboku soil widely distributed in Japan usually satisfies this condition.

A permeable / aerobic soil layer and a relatively anaerobic soil layer capable of supplying organic substances necessary for denitrification coexist, and sewage passes through both layers at a sufficient speed, and Full contact
Must have a structure that can penetrate.

The ideal sewage treatment method described above can be realized only when these three contradictory conditions are satisfied.

However, in the conventional soil purification method, although it depends entirely on the purification ability of the soil filled in the equipment, sufficient examination and research on the soil type, properties, structure, or soil layer structure are performed. It has not been mentioned, and the need for air-permeable soil is stated at best.

[Means for Solving Problems, Examples]

Therefore, the present inventor has completed the present invention by studying the soil itself as a result of earnest research to make the present soil purification method more ideal.

The present invention provides two types of soils having extremely different properties, that is, a soil excellent in air permeability and water permeability (hereinafter referred to as "water permeable / aerobic soil"), and an aluminum or active substance which is inferior in air permeability and water permeability. Soil that is rich in iron and carbon sources (hereinafter referred to as "impermeable and anaerobic soil") is combined in layers, steps, etc. to satisfy mutually contradictory conditions necessary for purification of sewage. Therefore, it should be called the multi-stage soil layer method. Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

(Structure) FIGS. 1 and 2 show a wastewater purifying apparatus (1) according to the present invention.
An example is shown. This sewage purification device (1) is provided with a permeable / water-permeable device under a sewage sprinkling pipe (3) arranged in a covered soil layer (2).
An aerobic soil layer (4) ... and a poorly permeable / anaerobic soil layer (5) ... are packed in layers and steps.
In the figure, the soil layers of the same type are overlapped with each other with a shift of 1/2, and one soil layer is formed in succession with the soil layers of other types to form a stack of five layers. The covered soil layer (2) is
It is made of breathable soil such as masa soil and can be used to plant lawns. The perimeter of the dirty water sprinkling pipe (3) is surrounded by a gravel layer (6), and the upper surface of the gravel layer (6) is a mesh body (7) for preventing clogging,
The lower surface is surrounded by a partition plate (8) for diffusing sewage, and constitutes a trench (9) as a whole. This partition (8)
May be a plastic molded product, or a flexible sheet of plastic or rubber may be used. In addition, a perforated drainage pipe (11) (corrugated pipe, etc.) surrounded by the gravel layer (10) is disposed in the lowermost layer, and a net-like body (12) is provided on the upper surface of the gravel layer (10).
Is provided.

Then, all of them are housed in a tank (13) made of impermeable material such as concrete. It should be noted that the tank (13) may be only the surrounding area, and in addition to concrete and plastic, materials having low water permeability such as clay and wood are also used, and sometimes masonry or bedrock can be used. In addition, the sewage pipe (3)
In consideration of clogging and deterioration of purification capacity in winter, two sets are arranged.

As a concrete device, for example, the coated soil layer (2) is 50c.
m, each soil layer (4) / (5) has a thickness of 20 cm (total soil layer is about 1.5 m), surrounded by a concrete tank (13) with a thickness of about 5-10 cm to collect treated sewage. It can be so. Although the size of the tank (13) depends on the amount of wastewater treated, for example, the maximum width is about 3 m and the length is about 20 m, and a large number of such devices may be arranged in parallel. It should be noted that small animals such as earthworms may be kept in the tank in order to help the decomposition of organic substances.

Next, in the present invention, the soil constituting the water-permeable / aerobic soil layer (4) means coarse grains with a clay content of 10% or less and a silt content.
The soil classification is sand soil, loamy sand soil, sandy loam soil, or coarser soil than these, which is less than 35%. Masa soil, immature dune soil, coarse-grained volcanic ash soil, coarse-grained brown forest soil or coarse-grained brown lowland soil is generally suitable as a permeable / aerobic soil.

The main role of this permeable and aerobic soil is
The purpose is to allow the anaerobic soil layer (5) to contact, diffuse, and permeate as efficiently as possible, prevent clogging of the device, and allow water to permeate quickly. In addition, aerobic decomposition, nitrification, deodorization, etc. of SS, BOD, COD, and other organic substances are performed around this permeable and aerobic soil. Therefore,
The soil is highly breathable and water permeable (eg
Saturated hydraulic conductivity of 10 ^-2 to 10 ^-3 cm / s is required). Depending on the case, sand with a particle size of 0.2-2.0 mm, 2 mm-
Gravel with a particle size of up to several cm can be used for this permeable and aerobic soil layer (4). Further, in a part thereof, especially in the lower part thereof, any material such as a tree branch or an artificial grass having an appropriate size may be used as long as it promotes water permeability.

On the other hand, the soil that constitutes the impervious and anaerobic soil layer (5) is
The total content of clay and humus is 20% or more (humus content is 3-5
% Or more), and active aluminum as Al is at least 2 to 3% by weight or more with respect to dry soil, more preferably 5% or more.
It is desirable that the content be at least wt%. Relatively fine-grained black soil (humic volcanic ash soil), surface layers of brown or tan forest soil, gray lowland soil, etc. are suitable as poorly permeable and anaerobic soils. The saturated hydraulic conductivity of refractory and anaerobic soils is less than one-tenth that of permeable and aerobic soils as refilling soil considering the destruction of natural soil structure, and is about 10 ^-3 to 10 ^-4.
It is below cm / s. It should be noted that in the case of hardly water-permeable / anaerobic soil with a low content of active aluminum, the amount used may be increased. For example, if the Al content is 2 to 3% by weight, the Al content is 5% by weight.
1.7 to 2.5 times more difficult to permeate and anaerobic soil is required. This can be easily achieved by increasing the number of steps in the soil layer used or by increasing the proportion of hardly permeable / anaerobic soil in each layer. Further, as a carbon source, a substance having a high C / N ratio such as leaves and other plants and animals, and surplus activated sludge may be mixed.

(Action) Then, the sewage (A) that permeates the gravel layer (6) and the covered soil layer (2) from the sewage sprinkling pipe (3) is subjected to the digestive decomposition action of soil organisms and the adsorption and filtration action of soil, SS minutes, BOD and COD
Aerobic decomposition and removal of organic matter and other organic matter. Ammonia nitrogen is also nitrified by the action of nitrifying bacteria and becomes treated water (B). This is the conventional soil purification method (capillary purification method).

And a part of this treated water (B) evaporates from the surface of the covered soil layer (2). The other part gravitationally flows down between the soil layers (4) and (5) arranged below the trench (9). Since the permeable / aerobic soil layer (4) is composed of highly permeable and permeable soil, the treated water (B) mainly passes through the permeable / aerobic soil layer (4) (solid arrow), and has more oxidative conditions. Placed below.

A non-permeable and anaerobic soil layer (5) is connected above and below and to the left and right of the permeable and aerobic soil layer (4). Therefore, water permeability
The treated water (B) flowing through the aerobic soil layer (4) is not permeable to water.
The phosphoric acid (positive and poly) in the treated water (B) easily contacts the anaerobic soil layer (5) and partially penetrates (dashed arrow) to easily penetrate into the poorly permeable and anaerobic soil layer (5). It is fixed by adsorption. On the other hand, NO ₂ and NO ₃ in the treated water (B) are changed to N ₂ and N ₂ O by the action of denitrifying bacteria in the same anaerobic and carbon source-rich impermeable / anaerobic soil layer (5). , Denitrified. Various heavy metals are also adsorbed and removed.

Thus, the purified water (C) from which SS, BOD, COD, and other organic substances, as well as nitrogen and phosphorus are almost completely removed, is discharged out of the apparatus through the drain pipe (11).

By the way, the degree of purification and the treatable amount by the device (1) of the present invention are determined by the ratio and arrangement state of the permeable / aerobic soil layer (4) and the hardly permeable / anaerobic soil layer (5), and further of the soil used respectively. It changes depending on the type and contained components. Therefore, it is advisable to concretely determine the optimum combination of soil layers depending on the quantity and quality of wastewater and the desired quality of purified water.

For example, the preferable ratio of the permeable / aerobic soil layer (4) to the hardly permeable / anaerobic soil layer (5) depends on the phosphoric acid (positive and poly) concentration in the sewage. According to the experimental results, when aiming at high load and high speed treatment of 200 l / m ^{2 of} sewage containing 10 ppm of total phosphorus, it is difficult to obtain when the active aluminum content of the permeable and anaerobic soil is 10% or more. The ratio of permeable / anaerobic soil layer (5) to permeable / aerobic soil layer (4) is approximately 1: 1. 2 when the active aluminum content is 5-10%
When the ratio is 1 to 3 and 5%, it is about 4 to 1.

Concentration of phosphoric acid (positive and poly) in wastewater is 5ppm, throughput is 100l /
If it is about m ² , the concentration of active aluminum may be about 1/4 of the above value.

In the case of the structure shown in FIG. 1, the ratio of the amount of use of both soil layers is proportional to the ratio of the length of each soil layer (4) / (5).
Alternatively, as shown in Fig. 3, another permeable / aerobic soil layer (14) is inserted between the soil layers (4) and (5) connected to each other, which is a different structure from that of Fig. 1. It is also possible to change the ratio of each soil layer (4), (5), (14) to variously adjust the ratio of both.

Further, the water permeability and the purification rate change depending on the gradient θ in FIG. 1 and the number of stacked layers and the thickness of each soil layer in FIGS. 1 and 3. Especially as shown in Fig. 3, treated water (B)
In the case where the structure has a structure that is better in contact with the poorly permeable / anaerobic soil layer (5), the purification rate is improved.

As a concrete device shown in FIG. 3, the permeable / aerobic soil layer (4) and the hardly permeable / anaerobic soil layer (5) each have a thickness of about 15 cm, and the usage ratio is 1: 2, Both layers (4)
・ It is considered that a 5 cm thick permeable / aerobic soil layer (14) is inserted between (5). Other structures are substantially the same as those shown in FIG.

Generally, in the case of a large amount of treatment in which the amount of treated liquid is more important than the quality of purified water (C), the structure shown in FIG.
The water permeability may be increased by increasing the ratio of the aerobic soil layer (4). On the contrary, when the quality of the purified water (C) is emphasized, the treated water (B) is the impervious and anaerobic soil layer (5) as shown in FIG.
A structure that makes it easy to come into contact with water, or a poorly permeable / anaerobic soil layer (5)
The water permeability may be lowered by increasing the ratio of.

As described above, the sewage purification apparatus of the present invention is based on the principle of the multi-stage soil layer method of treating sewage by combining the sewage / aerobic soil layer (4) and the hardly permeable / anaerobic soil layer (5). A major feature is that the treatable amount and the quality of purified water can be arbitrarily controlled by changing the ratio of (4) and (5), the laminated structure, and the number of laminated layers.

(Comparative Example) Next, Table 1 shows the results of comparing the sewage purification capacities of the soil purification apparatus according to the method of the present invention and the conventional method.

The apparatus according to the method of the present invention (embodiment) has a structure shown in FIG. 1 for the first embodiment and a structure shown in FIG. 3 for the second embodiment. In addition, the device by the conventional method (comparative example) is
The structure of the trench is the same as that of the device of the present invention, but the filling soil in the lower part of the trench does not have a multi-stage soil structure, only the Masa soil (Comparative Example 1) and only Kuroboku (Comparative Example 2), the same as the Example. This is due to the device being filled to a thickness (1 m).

And, the active aluminum and active iron contents of the Masa soil as the permeable and aerobic soil used here are 0.1 and
0.3% (dry soil weight basis), the content of activated aluminum and activated iron of Kuroboku as permeable soil / anaerobic soil is 5.6, respectively.
% And 0.6% (dry soil weight basis). Also at the bottom of the trench The temporary specific gravity of the soil was 1.5 for the masa soil of Comparative Example 1 and 0.8 for black pearl of Comparative Example 2, whereas it was 1.2 for both Examples 1 and 2.

From this table, it can be seen that in Comparative Example 1, the amount of wastewater that can be treated is large, but the quality of purified water is significantly reduced. Further, in Comparative Example 2, clogging is likely to occur, the treatable amount is small, and the phosphorus removal capability is high, but denitrification can hardly be expected. On the other hand, the embodiment (the device of the present invention) has a practically sufficient treatment amount for both 1 and 2, and is superior to the conventional device in denitrification and phosphorus removal. It can be seen that it is extremely excellent in terms of qualitative processing capacity.

Other Examples The above is the sewage sprinkling pipe (3) in which the permeable / aerobic soil layer (4) and the hardly permeable / anaerobic soil layer (5) are arranged in the covered soil layer (2). However, the device of the present invention is not limited to such a structure.

For example, the water-permeable / aerobic soil layer (4) and the hardly water-permeable / anaerobic soil layer (5) may be arranged beside or above the waste water sprinkling pipe (3) as shown in FIG. In this case, it is advisable to intersperse the hardly permeable and anaerobic soil layers (5) between the permeable and aerobic soil layers (4) so as not to prevent the permeation of the sewage from the sewage sprinkling pipes (3). .

Alternatively, as shown in FIG. 5, a separate perforated drainage pipe (15) is provided above the wastewater sprinkling pipe (3), and the permeated water is included between and around the wastewater sprinkling pipe (3) and the drainage pipe (15). -The aerobic soil layer (4) and the hardly permeable / anaerobic soil layer (5) may be arranged. This is because when the wastewater from the bath or laundry is discharged at one time and the amount of sewage increases temporarily, the sewage is reversely permeated into the covered soil layer (2) and discharged from the drain pipe (15). It is difficult to permeate treated water during reverse osmosis.
It is to be purified by the anaerobic soil layer (5).

Further, the source of the sewage is not limited to the sewage spouting pipe (3), but may be a sewage tank (16) provided in the ground as shown in FIG. 6, for example. Then, a permeable / aerobic soil tank (4) and a hardly permeable / anaerobic soil tank (5) are provided around the opening of the sewage tank (16) to treat the treated water (B) as purified water (C). You can also do it.

Although the tank (13) and the drainage pipe (11) are not shown in FIGS. 4 to 6, they may be provided with a water collecting type by providing them similarly to the case of FIG. Permeation type may be used. Of course, even in the apparatus shown in FIGS. 1 and 3, the tank (13) may be omitted and an underground infiltration type may be used. In the case of the underground infiltration type, the soil tanks (4) and (5) should be widened so that sewage can easily come into contact with the poorly permeable and anaerobic soil layers. Alternatively, instead of the tank (13) shown in FIG. 1, (particularly around), it may be surrounded by a non-permeable and anaerobic soil such as black bokeh.

The permeable / aerobic soil and the hardly permeable / anaerobic soil layer are the first
As shown in FIG. 3 and FIG. 3, it may be arranged as a certain lump, and is not necessarily limited to the layered one, but the layered one is the best from the viewpoint of treatment efficiency and design / construction.

[Effect] As described in detail above, the method of the present invention, the sewage permeated into the surrounding soil layer from a sewage supply source such as a perforated sewage pipe,
SS, BOD or COD contained in wastewater, ammonia and other organic substances are allowed to flow down or reverse osmosis while adding aerobic decomposition and nitrification in a soil layer with excellent air permeability and water permeability.
During this process, it adsorbs and denitrifies phosphorus by contacting, diffusing, and permeating a soil layer rich in activated aluminum, activated iron, and carbon source, which has poor air permeability and water permeability.

Therefore, according to the method of the present invention, not only deodorization of sewage and decomposition and removal of polluted organic matter, but also removal of total phosphorus and total nitrogen, which were difficult or impossible by conventional soil purification methods, are efficiently performed in both quality and quantity. It becomes possible to do. In particular, when the content of active aluminum in the soil is higher than a certain standard value, high phosphorus removal ability can be maintained for 10 years or longer with ordinary domestic wastewater or treated primary sewage or secondary effluent.

Further, the device of the present invention is provided with a sewage / aerobic soil layer and a non-permeable / anaerobic sewage / aerobic soil layer itself or on the side or particularly below the coated soil layer in which the opening of the sewage spouting pipe or the sewage tank is arranged. The soil layers are arranged in layers and steps. Therefore, it requires no advanced technology for construction, and the processing operation is simple, energy saving and cost saving. Moreover, by devising the ratio of the permeable / aerobic soil layer to the difficultly permeable / anaerobic soil layer and the layered structure, there are many advantages such as the controllable amount of sewage and the quality of purified water. There is.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an example of the wastewater purifying apparatus according to the present invention, and FIG. 2 is a transverse sectional view of the same. FIGS. 3 to 6 show other different examples, FIGS. 3 and 6 are longitudinal sectional views, and FIGS. 4 and 5 are transverse sectional views. 1 …… Sewage purification device 2 …… Coated soil layer 3 …… Sewage sprinkling pipe 4 ・ 14 …… Permeable / aerobic soil layer 5 …… Slightly permeable / anaerobic soil layer 6 ・ 10 …… Gravel layer 7 ・ 12 ... … Mesh 8 …… Separator 9 …… Trench 11 ・ 15 …… Drainage pipe 13 …… Tank 16 …… Sewage tank A …… Sewage B …… Treated water C …… Purified water

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Abe 896 Futako, Yatsuka-cho, Yatsuka-gun, Shimane Prefecture (56) Reference JP-A-57-194090 (JP, A) JP-B 59-31400 (JP, B2) JP Kosho 57-54194 (JP, B2)

Claims (5)

[Claims] 1. The sewage infiltrated into the surrounding soil layer from the sewage supply source is used as SS, BOD and COD, and ammonia and other organic substances contained in the sewage as sand soil, loamy sand, sandy loam, or these. In a soil layer consisting of coarser soil with excellent air permeability and water permeability, it is made to flow down or reverse osmosis while adding aerobic decomposition and nitrifying action. A soil layer rich in iron and carbon sources, which is a combination of the above-mentioned permeable / aerobic soil layer in a layered or stepwise manner, on the surface of a black or brown forest soil, or a soil layer consisting of a gray lowland soil. Contact, diffusion,
A method for purifying sewage, which is characterized by adsorbing and removing phosphorus in sewage and performing denitrification after permeation. 2. The method according to claim 1, wherein the treatable amount of sewage and the degree of treatment can be arbitrarily set by changing the arrangement, the number of stages or the quantitative ratio of both soil layers through which the sewage passes. How to purify sewage in Japan. 3. The method for purifying sewage according to claim 1 or 2, wherein the periphery is surrounded by an impermeable material and purified water is collected in the lower part. 4. Permeability and water permeability of sandy soil, loamy sandy soil, sandy loam soil, or coarser soil in at least a part of the lower part of the covered soil layer where the perforated drainage pipe or the opening of the wastewater tank is located. Excellent soil layer, black my soil, surface layer of brown or tan forest soil, or gray lowland soil with poor permeability and water permeability, but a layer of soil rich in active aluminum or active iron and carbon source, layered, A sewage purification device characterized by being arranged in stages in multiple stages. 5. A drainage pipe surrounded by a gravel layer is provided at the lowermost layer,
The sewage purification device according to claim 4, wherein the periphery and the bottom surface are surrounded by an impermeable material.