JPH02119992A - Method and device for purifying sewage - Google Patents

Abstract

PURPOSE:To improve the activity of denitrifying bacteria and to enhance the denitrifying capacity by supplying sewage to the bed of the soil mixed with metallic iron and a filler to consume the oxygen in the sewage, and maintaining the bed in an anaerobic atmosphere. CONSTITUTION:The SS, BOD, COD, etc., of the sewage A from a sewage sprinkler pipe 1 is aerobically decomposed in the coating soil bed 2 by the digesting and decomposing action of the soil organisms and the adsorbing and filtering action of soil to obtain treated water B. The treated water B is then infiltrated into the anaerobic and water-permeable soil 6, and brought into contact with the iron particles as a reducing agent in the soil. As a result, a large amt. of oxygen in the treated water B and the soil 6 is consumed, and the activity of the denitrifying bacteria is improved. Consequently, the NO2 and NO3-N in the treated water B are converted to N2 and N2O by the denitrifying bacteria while infiltrating down the soil 6, and efficiently denitrified. By this method, purified water C with the org. matter and nitrogen contents remarkably reduced is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for treating sewage, in particular, a method for treating sewage using soil to remove nitrogen bones and phosphorus contained in sewage such as domestic wastewater, urine and urine treated water, and sewage. The present invention relates to a novel method and apparatus for advanced processing.

[Prior Art] Problems with conventional soil purification methods and properties required of soil can be summarized in the following three points.

■ Water permeability is sufficiently high and clogging is unlikely to occur.

■ High content of compounds capable of adsorbing phosphoric acid, such as activated aluminum and activated iron.

■ Aerobic soil necessary for nitrification of ammonia nitrogen,
A structure in which a relatively anaerobic soil layer coexists that can supply the carbon source necessary for denitrification by microorganisms, and wastewater can pass through both layers at a sufficient speed and have sufficient contact and penetration into both layers. Become.

As a solution that can satisfy both of these contradictory conditions,
The present inventor has developed a soil layer with excellent air permeability and water permeability (a layer of sand, masa, zeolite grains, etc.: hereinafter referred to as a "permeable/aerobic soil layer").
A soil layer rich in active aluminum, active iron, and carbon sources (black soil, red soil, etc.; hereinafter referred to as the [Pf permeable/anaerobic soil layer]) is combined with a soil layer that has poor air permeability and water permeability but is rich in active aluminum, active iron, and carbon sources. We have developed an ideal soil purification method and device that can be called a multi-stage soil layer method (Japanese Patent Application No. 60-52729, Japanese Unexamined Patent Publication No. 61-212386).

Furthermore, as shown in Figure 4,! #Permeable/anaerobic soil 16
The workability problem was solved by forming an 8 m water/anaerobic soil layer as a type of soil block 17 packed in a water-permeable container or bag 13. In addition, the carbon content (C/
By using a material with a high N ratio), an improvement in denitrification ability was ensured (Japanese Patent Application No. 61-10730).

[Problems to be Solved by the Invention] However, there are some problems with the conventional multi-layer soil layer method described above, especially in T# permeable/anaerobic soil (soil block). That is, the permeable aerobic soil satisfies the conditions necessary for nitrification of ammonia nitrogen, and also exhibits good water permeability that can withstand high loads without causing any problems.

On the other hand, in H permeable, anaerobic soils, the supply of carbon sources necessary for denitrification by microorganisms was sufficient, but when considered as an anaerobic soil layer, denitrification ability was stabilized and microorganisms (denitrification There was still room for improvement in terms of the high activity of Nitrogen bacteria. That is, although the nitrogen purification ability is determined by the denitrification reaction rate of denitrifying bacteria, wastewater does not pass much through the H permeable anaerobic soil, but mainly passes through the periphery of the block. Therefore, when the inflow load it (I!/-·day) is increased, the flow velocity at the peripheral portion becomes faster and the purification performance decreases. In addition, when the inflow load is constant, the thickness of the multi-stage soil layer and the purification capacity are proportional, but if the capacity load < 1/I day) is - constant, the thickness of the soil layer is increased (e.g. twice) and the inflow When the load amount is increased (for example, doubled), the purification rate tends to deteriorate. Therefore,
In order to increase the sewage treatment capacity of the device (17rd day), it is necessary to increase the area. As a result, construction locations are limited and costs are high, which poses a major obstacle to implementation.

[Means for Solving the Problems] The present invention was made in view of the above, and replaces the H permeable/anaerobic soil that has an important effect on denitrification by using soil with excellent water permeability and metal fillers. By using improved permeable and anaerobic soil mixed with iron (hereinafter referred to as "permeable and anaerobic soil"), the treatment capacity is increased and the activity of denitrifying bacteria is improved, resulting in a dramatic increase in denitrification capacity. This will enable them to improve their performance.

That is, when metallic iron such as reduced iron comes into contact with air-containing water, a small amount of iron ions are eluted in the neutral region due to the oxidizing action of oxygen in the air. Utilizing this phenomenon, the soil layer is maintained in an anaerobic atmosphere by consuming oxygen in the wastewater, thereby improving the activity of denitrifying bacteria. Furthermore, the water permeability of the anaerobic soil portion is improved so that sewage permeates evenly and denitrification is performed well.

Metallic iron is not necessarily limited to pure iron. Further, from the viewpoint of reactivity, reduced iron is preferable, but is not necessarily limited to this. The shape of the metal iron is preferably granular in consideration of ease of handling and solubility. Its size is usually about 5 to 20 mesosh.

The usage ratio of metallic iron is determined by calculation or experiment based on the purity and particle size of metallic iron, the nitrogen concentration and dissolved oxygen amount in raw water (sewage water), the amount of treated water, etc. In the case of iron particles,
Usually about 2 to IO weight %, especially about 4 to 6% is preferable. If it is less than this, the denitrification efficiency will decrease, and if it is too much, there will be a problem of elution of iron ions.

In addition, iron ions produced by melting metal iron combine with acid ions and precipitate, and therefore exhibit an excellent effect in removing phosphorus.

As the soil constituting the easily permeable/anaerobic soil layer, in addition to sand and masa soil, soils with excellent permeability such as immature sand dune, coarse volcanic ash soil, and coarse brown forest soil are used.

In addition, as fillers used in place of soil, in addition to natural or artificial granular minerals such as zeolite particles, perlite, and vermiculite, crushed plastic products and the like can also be used. If the carbon content in these soils or fillers is low, mix materials with high carbon ratios (C/N ratio) such as jute, rice straw, tree leaves, other plants and animals, and surplus activated sludge as carbon sources. You can leave it there.

Easily permeable and anaerobic soil may be filled into the device as is, but if it is packed into a type of soil block packed in a water-permeable container or bag, handling becomes extremely difficult. In addition, uneven distribution of metallic iron in the entire device due to the difference in specific gravity between metallic iron and soil is prevented, and there are also advantages such as the use ratio of permeable and aerobic soil can be adjusted as designed. Furthermore, if a material with a high carbon content (C/N ratio) such as wood or jute is used as the material for these containers or bags, the denitrification ability can be improved.

On the other hand, the permeable/aerobic soil to be filled between the above-mentioned easily permeable/anaerobic soil layer or pro-tsuku includes not only the same materials as the above-mentioned easily permeable/anaerobic soil such as sand, but also zeolite grains and other materials. Fillers are also used.

The main role of this permeable and aerobic soil is to make wastewater permeable and
The objective is to enable contact, diffusion, and infiltration into layers and blocks of anaerobic soil as efficiently as possible, as well as to prevent clogging of the device and allow water to permeate quickly. In addition, mainly in this permeable and aerobic soil, 88 minutes, BOD and COD
Aerobic decomposition, nitrification, and deodorization of other organic matter are carried out.

Therefore, this soil has high air permeability and water permeability (
For example, the saturated superhydric coefficient is 10″2~10-3CIII
/S) is required. Depending on the case, °ζ may be mixed with something that promotes water permeability, such as sand, gravel, appropriately sized tree branches, or artificial grass.

When zeolite grains are used as permeable and aerobic soil, zeolite has a large ammonium ion retention capacity;
The adsorbed ammonium ions are converted into li+!+ acid nitrogen by the action of nitrifying bacteria, and are separated from the zeolite grains.Then, the process of ammonium ions being adsorbed again is repeated.

This behavior has the effect of lengthening the residence time of nitrogen within the device, which is advantageous for nitrogen removal. Furthermore, the large CEC of zeolite reduces the pl+ of wastewater due to nitrification.
It has a buffering effect against deterioration, and has favorable effects such as protecting microbial activity within the device.

[Function] As schematically shown in FIG.
In the covering soil layer 2 consisting of masa top, etc., the 88 min. and BOD
and is subject to aerobic decomposition and removal of COD components and other organic matter. Ammonia nitrogen is also nitrified by the action of nitrifying bacteria and becomes treated water (F3).

A part of this treated water (r()) transpires from the surface of the covering soil layer 2, but most of it gravitates down to the purification layer 4 below the trench 3.The purification layer 4 is made of permeable and aerobic soil. Multiple layers of waste from No. 5 and easily permeable/anaerobic soil No. 6 (2T- in the figure)
It is a layered product. As the purification layer 4, easily permeable and anaerobic soil blocks filled with easily permeable and anaerobic soil 6 in a jute bag etc. are placed with gaps left and right on the top and bottom, front and rear, and water permeable and aerobic soils are placed in the gaps. It may also be filled with soil 5.

The treated water (B) that has permeated into the permeable/aerobic soil 5 is placed under more oxidizing conditions and is subjected to aerobic decomposition and nitrification of organic matter in the same manner as the covering soil layer 2. In addition, when zeolite grains are used, fixation and nitrification of ammonia nitrogen are also performed here.

Next, the treated water (B) permeates into the easily permeable anaerobic soil 6 and comes into contact with the reducing agent, such as iron particles, contained therein to cause the following reaction.

Fe (1 unit) [;'e2■+2eO Therefore, a large amount of oxygen in the treated water (B) and easily permeable/anaerobic soil 6 is consumed. This action keeps the entire layer of easily permeable, anaerobic soil 6 anaerobic at all times, improving the activity of denitrifying bacteria. Therefore, NO2 and NO3N (nitrate nitrogen) in the treated water (B) are converted into N2 and N20 by denitrifying bacteria when they percolate through the layer of the soil 6, and are efficiently denitrified.

In addition, during this process, phosphoric acid (positive and poly) in the treated water (B)
reacts with iron ions Fe2Φ in easily permeable, anaerobic soil to form a precipitate of iron phosphate, which is adsorbed and fixed in the layer of soil 6.

In this way, purified water (C) from which nitrogen and phosphorus have been largely removed in addition to SS, BOD, and COD components and other organic matter
is collected in the drainage layer 7 and discharged to the outside of the device through the drainage pipe 8.

[Example] Next, the present invention will be described in detail based on an example shown in the drawings.

FIG. 2 shows an example of a laboratory-scale sewage purification apparatus according to the present invention. This sewage purification device 9 has a medium diameter of 10 cm and a length of 4 cm.
Acrylic tank 10 with internal dimensions of 5 cm and depth of 45 cm
Each type of soil is contained within.

That is, a covering soil layer 2 with a sewage sprinkler pipe 1 arranged from above;
The central part is a purification layer 4, and the lower part is a drainage layer 7 incorporating a drainage pipe 8. The drainage layer 7 is filled with gravel 11. The code 12 is net.7.

The permeable/aerobic soil 5 (thickness 5 mm) in the cover soil layer 2 (thickness 5 cm) and the purification layer 4 are made of zeolite grains (2 to 5 mm thick).
31φ) was used.

On the other hand, as easily permeable and anaerobic soil 6, iron grains (1
A 5% mixture of 0 to 20 mesosier) was used. The active aluminum and active iron contents (based on soft soil weight) of this improved easily permeable and anaerobic soil 6 are 0.1% and 5.3%.
Met. Then, add this easily permeable, anaerobic soil 6 to 3 cm.
x 5cmX I Ocm (- part 3cmX 2.5c
Fill a jute bag 13 with a size of (m x 10 cm) (
200g) to form easily permeable/anaerobic soil block 14,
These were arranged at intervals of 5 mm vertically and horizontally. The soil blocks 14 in each layer were arranged at intervals of 2.5 cm so that the treated water (B) could sufficiently contact and penetrate. The soil blocks 14 used were 77 (M) and stacked in 9 stages.

This jute bag body 13 not only constitutes a unit for filling easily permeable and anaerobic soil, but also is itself a net-like body that exists at the interface between aerobic soil and anaerobic soil, and is a net-like body that exists in both layers. This allows water to penetrate and move in all directions at the contact interface. In addition, the jute bag body 13 has a carbon content (C
/N ratio) is extremely high (usually 50 or more), it also serves as a carbon source for denitrifying bacteria, and also works to increase the denitrifying activity of the device. Note that the structure of the sewage purification device 9 and the material shape of the soil block 14 are merely examples, and the present invention is not limited to these.

L7 and artificial sewage (NO3N40mg/l!+PO4-P20) is supplied to this sewage purification device 9 as raw water (A).
mg//) 17! /day.

The experiment was conducted continuously for one month starting from September 1986. The results (average values) are as shown in Table 1.
Both T''-P were over 99%, which was extremely satisfactory.In addition, the supply amount per day with this equipment was 25β/d.
・Equivalent to the daily inflow load.

Next, as a conventional example, a similar sewage purification test was conducted using the apparatus shown in FIG. 4, and the results are also shown in Table 1. This conventional sewage purification device 15 differs from the device of the present invention shown in FIG. 2 only in that a H-permeable/anaerobic soil block 17 filled with Kuroboku soil 16 is used instead of the easily-permeable/anaerobic soil 60. , everything else is exactly the same. The content of active aluminum and active iron in Kuroboku soil (based on soft soil weight) is 5.
゜6% and 0.6%.

Comparative Example 1 has a drain pipe 8 as shown in FIG.
Under this condition, raw water was supplied IN/day for 3 consecutive months.
I did it. The values in Table 1 are average values, and purified water (0
)'s T-N? The JM degree increased over time, and the purification ability significantly decreased after 3 months.

In Comparative Example 2, following Comparative Example 1, raw water was continuously supplied for two months at a load water amount of 11/day. However, it was Table -1.

Judging from the results of the above comparative examples, it is clear that the conventional equipment does not require purified water (
If the target treated water quality for T-N in C) is 10 mg/l, the inflow load will be 25 I in the long term! /d・mouth seems to be the limit.

Table 2 In this case, the drain pipe 8 is placed in the state shown in (b) in Figure 4.
The purification layer 4 was used in a flooded state (anaerobic state). As a result, T-IJ in the purified water initially decreased to about 5II1 g/e, but rose again, and two months later, the purification ability of T-N decreased significantly. In addition, in both Comparative Example 1 and Comparative Example 2, T
-The removal rate of P was 99% or more.Next, an experiment was conducted to see how much inflow load the device of the present invention could withstand. That is, Showa 6
Starting in May 2017, an experiment was conducted to examine the degree of purification of purified water (C) obtained by increasing the supply of raw water (A). The results (average values during each period) are shown in Table 2.

Note that the device 9 used was the same as in the previous example.

Raw water (A) is artificial sewage (N O:l -N 36.6
mg/e-1-P O, +-P21.4 mg/l)
Sono supply was carried out as shown in the remarks column in the table, and these were carried out continuously for a total of three and a half months. Moreover, the inflow load amount (β/l·day) in Table 2 is the amount supplied by this device converted into per d. As a result, in the device of the present invention, when the target treated water quality of purified water (C) TN is 10 mg/l, 2507! /n? It has been found that this method can sufficiently withstand an inflow load of about -100 days and high-speed processing. This is sufficient for practical use in consideration of construction quality and cost.

In the apparatus shown in the above embodiment, the easily permeable and anaerobic soil 6 is filled into a jute bag 13 to form a soil block, but the present invention is of course not limited to this.

For example, as shown in FIG. 3, a sewage purification device 18 in which permeable aerobic soil 5 and easily permeable anaerobic soil 6 are layered in multiple stages (two stages in the figure) can also exhibit sufficient denitrification capacity. It is possible.

This sewage purification device 18 has gravel 19 around the sewage sprinkling pipe 1.
A net 20 is arranged between the cleaning layer 4 and the cleaning layer 4. As the permeable aerobic soil 5 occupying the upper part of the purification layer 4, in addition to the above-mentioned zeolite, masa soil, sand, etc. can be used. As the easily permeable and anaerobic soil 6 in the lower part of the purification layer 4, improved soil made by mixing about 5% iron particles into masa soil, sand, etc. can be used. Further, the substance having a high carbon ratio (C/N ratio) is mixed as a carbon source. In addition, sewage tanks and cesspits are also possible sources of sewage water.

In short, the present invention combines layers or blocks of permeable/aerobic soil 5 and easily permeable/anaerobic soil 6 to form a purification layer 4, and also adds iron to the highly permeable soil as the easily permeable/anaerobic soil 6. It is a mixture of grains and other reducing agents, and there are no limitations to the structure of other parts of the sewage purification device.

[Effects of the Invention] As detailed above, the sewage purification method of the present invention uses easily permeable anaerobic soil in which a reducing agent is mixed into permeable soil,
By consuming the oxygen in the wastewater supplied to this soil layer, the soil layer is forced into an anaerobic state, which improves the activity of denitrifying bacteria and dramatically improves the denitrification effect.

Furthermore, by combining this permeable, anaerobic soil and permeable, aerobic soil in multiple stages, S in wastewater can be reduced in permeable, aerobic soil.
This system performs aerobic decomposition and removal of organic matter such as S, simultaneously nitrifies ammonia nitrogen, and performs denitrification and dephosphorization in easily permeable and anaerobic soil for comprehensive purification of wastewater. be.

Therefore, in combination with the improved water permeability of the anaerobic soil layer, the wastewater treatment capacity of the equipment is greatly increased, high-load operation is possible, and the equipment can be made more compact. However, it has an unprecedented effect.

In addition, the sewage purification device of the present invention uses sand and masa soil, which are readily available as anaerobic soil, and uses iron grains as a reducing agent, so it can be constructed inexpensively and easily, and the entire soil used is It has excellent water permeability and can treat large amounts of wastewater with a compact device. In addition, by filling easily permeable and anaerobic soil into jute bags and forming blocks, it is possible to equalize the mixing ratio of the reducing agent and permeable soil when looking at the entire easily permeable and anaerobic soil layer. It has the advantage of being handled inside the cylinder.

[Brief explanation of drawings]

Figure 1 is a schematic diagram explaining the principle of sewage purification of the present invention, Figure 2
The figure shows an example of a laboratory-scale sewage purification device according to the present invention.
- A vertical cross-sectional view of the device taken along the X-ray section; Figure 3 shows another example of a laboratory-scale sewage purification device; al is a vertical cross-sectional view;
(b) is a vertical cross-sectional view of the device taken along the 'y'-Y line in Figure (a), Figure 4 shows a comparative example, al is a vertical cross-sectional view, (bl is a vertical cross-sectional view of the same figure (al) It is a vertical cross-sectional view of the device taken along the line -Z. 1... Sewage water pipe 2... Covering soil layer 4... Purification layer 5... - Permeable/aerobic soil 6... Easy permeable/anaerobic soil 9, 18... Sewage purification device 13... Jute bag body 14... Easy Permeable/anaerobic soil block A...
... Sewage (raw water) B ... Treated water C ... Purified water 1st 4th

Claims (1)

[Claims] 1. Supplying sewage to a layer of soil or filler mixed with metallic iron and consuming oxygen in the sewage to maintain the soil or filler layer in an anaerobic atmosphere and inhibit denitrifying bacteria. A method for purifying wastewater characterized by improving activity and effectively performing denitrification. 2. Sewage is passed through a layer of permeable, aerobic soil or filler material to nitrify the ammonia nitrogen in the wastewater, and then passed through a layer of soil or filler mixed with metallic iron for denitrification. A method for purifying sewage characterized by: 3. The method for purifying wastewater according to claim 1 or 2, wherein a carbon source is mixed together with metallic iron. 4. A combination of a layer or block of permeable/aerobic soil or filler and a layer or block of soil or filler mixed with metallic iron is placed below the sewage supply source. Soil-type sewage purification equipment.