JPH02126995A - Soil trench - Google Patents

Abstract

PURPOSE:To enhance the sewage purifying capacity of the title trench, to reduce clogging and to miniaturize the equipment by arranging a porous calcium silicate hydrate granular body alone or the mixture with gravel around a water sprinkling pipe. CONSTITUTION:The porous calcium silicate hydrate granular body 7a alone or the mixture with gravel 7b is arranged around the water sprinkling pipe 6. Furthermore, a porous calcium silicate hydrate granular body 5a alone or the mixture with sand 5b is packed into a trough-shaped water-impermeable vessel 4 provided below the water sprinkling pipe 6. As a result, the sewage purifying capacity is enhanced, clogging is reduced and the equipment can be miniaturized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is for disposing of wastewater such as human waste, domestic wastewater, industrial wastewater, etc. by permeating it into the soil, and purifying the same using the purification function of microorganisms. relating to soil trenches (also referred to as capillary infiltration trenches).

[Conventional technology] The purpose of trenching, which has been around for a long time, is to simply dispose of wastewater by permeating it into the soil. was being formed. Therefore, in this trench, there was a problem that most of the wastewater permeated by gravity into the underlying soil where microorganisms had low purification activity, and the wastewater was disposed of without being sufficiently purified.

Therefore, in Japan, the above-mentioned trench has been developed into a soil trench that can perform purification treatment by capillary infiltration of sewage into the surface soil where microorganisms have high purification activity.

The structure of this soil trench 21 will be explained according to FIG. 2. First, a trench groove 23 is dug in the ground 22. A synthetic resin film 24a is laid on the bottom of this trench groove 23 to form a gutter-like impermeable tank 24, and the impermeable tank 24 is filled with a sand body 25a such as coarse sand or capillary sand to form a lower layer 25. do.

A water sprinkling pipe 26 made of a permeable ceramic pipe or the like is arranged above the lower layer 25, and a gravel body 27a such as gravel or capillary gravel is buried around the water sprinkling pipe 26 to form a water sprinkling pipe surrounding layer 27. form. A capillary substance 28a such as a net or non-woven fabric is laid on the sprinkler pipe surrounding layer 27 to form a boundary layer 28, and on top of the boundary layer 28, local soil, peat, earthworm feces, and surplus are deposited. The two upper layers are completed by backfilling with capillary improved soil 29a mixed with organic additives such as sludge.

Sewage W seeping out from the sprinkler pipe 26 of the soil trench 21
Since gravity penetration is prevented by the impermeable tank 24, the water permeates into the ground 22 from the sides after capillary siphon movement in the sprinkler pipe surrounding layer 27 and lower layer 25.

Therefore, first, the microorganisms contained in this wastewater W are fixed on the surfaces of the gravel bodies 27a and sand bodies 25a of the above-mentioned both layer portions 27.25, form a stable biofilm, and begin to live there. In addition, microorganisms living in the capillary improved soil 29a of the upper layer 29 also descend to the above-mentioned both layer portions 27.25 and the gravel body 27a and the sand body 25.
It is fixed on the surface of a and acts to supplement microorganisms not included in the wastewater W.

After the microorganisms have been immobilized, the wastewater W exuding from the sprinkler pipe 26 is purified by the organic matter decomposition function of the microorganisms living on the surfaces of the gravel body 27a and sand body 25a, and BOD (biochemical oxygen demand) , C0D (Chemical Oxygen Demand), SS (Floating Substances), etc., are removed and then permeated into the earth 22 for disposal.

[Problems to be Solved by the Invention] However, the soil trench 21 also has the following problems.

(1) The ability to decompose organic matter is limited. This is due to the following reason.

(2) It is not always easy for microorganisms to be fixed on the surfaces of the gravel body 27a and sand body 25a, and there are cases where microorganisms do not propagate sufficiently.

(2) Since the water absorption power of the gravel body 27a and the sand body 25a itself is small, the permeability of the gravel body 27a and the sand body 25a itself is low, and the permeability of the gravel body 27a and the sand body 25a is reduced due to the infiltration of the waste water W, thereby reducing the purifying activity of microorganisms.

- When the decomposition of organic matter in wastewater W by microorganisms progresses, the pH becomes slightly acidic due to the decomposition products such as lactic acid, butyric acid, acetic acid, etc., which is unsuitable for the activity of microorganisms, and the purification activity of microorganisms decreases.

(2) The removal rate of nitrogen compounds is low. This is because if the activity of microorganisms decreases due to the above-mentioned reasons, nitrification from ammonia nitrogen to nitrate nitrogen will not be sufficiently performed.

(3) Adsorption capacity for phosphorus compounds (phosphoric acid and phosphates) is limited. Now, if the wastewater W contains a phosphorus compound, phosphate ions in the phosphorus compound are absorbed by the gravel body 27a.
It is thought that the particles are adsorbed onto the surface of the sand body 25a. However, since the surface area of the gravel body 27a and the sand body 25a is not so large, the adsorption capacity is also limited.

(4) The facility area is large. This is because, as described above, the conventional soil trench did not necessarily have a high purification ability for wastewater W. For example, soil trenches for domestic wastewater treatment require a length of 2 m or more per person, and require a larger area of land than the activated sludge method.

(5) Clogging occurs easily. The gravel body 27a and the sand body 2
This is because, in 5a, not only the capillary siphon movement of the waste water W was not sufficiently performed, but also the ability to purify the waste water W was not high as described above. Therefore, in the past, in addition to the main soil trench, a preliminary soil trench of 1/2 or more of the size was installed side by side, and both soil trenches were used alternately to naturally purify and recover the clogging of the main soil trench. I needed to do it.

Moreover, it took one to two months for recovery through natural purification.

An object of the present invention is to provide a novel soil trench that has a high ability to purify sewage, does not cause clogging, and can also reduce the size of facility equipment.

[Means for Solving the Problems] In order to achieve the above object, in the soil trench of claim 1, porous calcium silicate hydrate granules are used alone or mixed with gravel around the water pipe. I took the step of setting it up.

Further, in the soil trench of claim 2, a means is taken in which a gutter-like impermeable tank provided below the water pipe is filled with porous calcium silicate hydrate granules alone or mixed with sand. Ta.

[Function] The microorganisms contained in the wastewater exuding from the sprinkler pipes are defined in claim 1.
In the soil trench of claim 2, the soil trench of claim 2 is fixed to porous calcium silicate hydrate granules (including gravel, if mixed with gravel) arranged around the water pipe. In this case, they are fixed to porous calcium silicate hydrate granules (including sand if mixed with sand) filled in an impermeable tank, and both forms stable biofilms to inhabit.

Here, since the porous calcium silicate hydrate granules have a large number of fine voids, they facilitate the immobilization and propagation of the microorganisms, and create an atmosphere in which the microorganisms are more likely to be active. That is, the porous calcium silicate hydrate particles act as a suitable carrier for microorganisms.

In addition, the porous calcium silicate hydrate granules have a large water-absorbing power and greatly improve air permeability when sewage permeates, thereby further enhancing the purification activity of microorganisms.

Furthermore, the porous calcium silicate hydrate granules neutralize and buffer the pH of lactic acid, butyric acid, acetic acid, etc., which are organic decomposition products, and maintain wastewater at a slightly alkaline level suitable for microbial activity. Does not reduce purification activity.

As mentioned above, the microorganisms with enhanced purification activity quickly and reliably decompose organic matter contained in wastewater, and also effectively oxidize nitrogen compounds, promoting nitrification from ammonia nitrogen to nitrate nitrogen. .

In addition, when sewage contains phosphorus compounds, porous calcium silicate hydrate granules effectively adsorb phosphate ions in the phosphorus compounds into their many fine voids, so the phosphorus compounds have a high removal rate. will be removed.

In addition, in this soil trench, the permeability of wastewater is increased by the porous calcium silicate hydrate granules, and the capillary siphon movement of the wastewater is promoted more than in the conventional case, as well as the purification of microorganisms as described above. Because the activity is increased, clogging is less likely to occur, and even if it does occur, recovery through natural purification is faster than with conventional methods.

[Example] Hereinafter, an example of a soil trench embodying the present invention will be described with reference to FIG. 1.

In the soil trench 1 of this embodiment, the ground 2 has a width of 30 mm.
A trench 3 with a width of 70 mm and a wide top, 40 to 100 anm in depth, and a length of several meters to several tens of meters is dug, and a synthetic resin film 4a is laid on the bottom of the trench 3.
A gutter-like impermeable tank 4 is formed to prevent gravitational infiltration of wastewater W.

A lower layer 5 is formed in the impermeable tank 4 by filling porous calcium silicate hydrate granules 5a alone or in a mixture with a sand body 5b such as coarse sand or capillary sand. Here, the sand body 5b broadly refers to sand or sand-like granular bodies, and its components, particle size, etc. are not limited. Further, when mixing the porous calcium silicate hydrate granules 5a and the sand body 5b, the mixing ratio is not particularly limited, and for example, the porous calcium silicate hydrate granules 5a may be 20% by volume. can.

A water sprinkling pipe 6 made of a water-permeable ceramic pipe or the like is arranged above the lower layer 5, and around the water sprinkling pipe 6, porous calcium silicate hydrate granules 7a are used alone or with gravel, gravel, etc. The sprinkler pipe surrounding layer portion 7 is formed by being mixed and filled with a gravel body 7b such as capillary gravel. Here, the gravel body 7b broadly refers to gravel or gravel-like granular bodies, and its components, particle size, etc. are not limited. Moreover, when mixing the porous calcium silicate hydrate granules 7a and the gravel body 7b,
The mixing ratio is not particularly limited, and for example, the porous calcium silicate hydrate granules 7a can be 20% by volume.

A capillary substance 8a such as a net or nonwoven fabric is placed on the tube surrounding layer 7.
By this, a boundary layer part 8 is formed to prevent the next upper layer part 9 from falling. Capillary improved soil 9a, which is a mixture of local soil and organic additives such as peat, large earthworm particles, and surplus sludge, is backfilled on top of this boundary layer 8, thereby improving air permeability and water retention. An upper layer portion 9 is formed.

Now, the porous calcium silicate hydrate granules 5a, 7
Examples of a include inorganic porous artificial minerals obtained by mixing, curing, and curing high-pressure, high-temperature steam in a known manner by mixing a silicic acid raw material such as silica and a calcium oxide raw material such as lime cement. can. Specific components include those whose main component is one or more selected from the group of tobermorite, xonotlite, C-8-H gel, fossagite, gyrolite, and helebutandite. However, S i O2 min and CaO
There are no limitations on the composition ratio with respect to other trace components or on the content of other trace components.

Further, the porous calcium silicate hydrate granules 5a, 7
A is a porous material having a large number of fine voids, preferably with a porosity of 50 to 90%. This is because microorganisms inhabit these numerous voids and create an atmosphere in which they can easily become active.

Further, the porous calcium silicate hydrate granules 5a, 7
Although the particle size of a is not particularly limited, it is preferably 5 m or less for the porous calcium silicate hydrate granules 5a used in the lower layer portion 5. This is because if this exceeds 5 m, the capillary siphon movement of the wastewater W from the impermeable tank 4 will be suppressed. Further, the porous calcium silicate hydrate granules 7a used in the water sprinkler pipe surrounding layer 7 are preferably 5 to 50+ mn. If this is less than 5 mm, the sewage outlet of the water sprinkler pipe 6 must be made smaller, resulting in a problem that clogging is likely to occur.

According to the soil trench 1 configured as described above, the following effects are achieved.

(1) Since the sewage W seeping out from the sprinkler pipe 6 is prevented from permeating by gravity by the impermeable tank 4, it moves in a capillary siphon through the surrounding layer 7 and the lower layer 5 of the sprinkler pipe, and then flows from the sides to the earth. It will penetrate into 2.

Therefore, first of all, are the microorganisms contained in this wastewater W in the porous calcium silicate hydrate granules forming the sprinkler pipe surrounding layer 7? a (when the gravel body 7b is mixed, the same gravel body 7b is also included. The same applies hereinafter) and the porous calcium silicate hydrate granules 5a forming the lower layer 5 (when the sand body 5b is mixed, (including the sand body 5b (the same shall apply hereinafter)), they form a stable biofilm and live there. In addition, microorganisms living in the capillary improved soil 9a in the upper layer 9 also descend to the above-mentioned both layer portions 7.5 and enter the porous calcium silicate hydrate granules 7a, 5a.
and acts to supplement microorganisms not contained in wastewater W.

Here, the porous calcium silicate hydrate granules? a,
Since 5a has a large number of fine voids, it facilitates the immobilization and propagation of the microorganisms, and creates an atmosphere in which the microorganisms are more likely to be active. That is, the porous calcium silicate hydrate particles 5a, 7a act as suitable carriers for microorganisms.

Further, the porous calcium silicate hydrate granules 7a, 5
Since a has a large water-absorbing power and greatly improves air permeability when the wastewater W permeates, it further enhances the purification activity of microorganisms.

(2) After the formation of the biofilm, the wastewater W exuding from the sprinkler pipe 6 is purified in the following manner and disposed of by infiltration into the earth 2.

■Organic substances contained in wastewater W are quickly and reliably decomposed by microorganisms whose purification activity is enhanced by the porous calcium silicate hydrate particles 7a and 5a as described above, and the BOD
, COD, SS, etc. are effectively removed.

Now, when the above organic substances are decomposed, lactic acid, butyric acid, acetic acid, etc. are produced. However, in this embodiment, the porous calcium silicate hydrate particles 7a, 5a neutralize these acids and adjust the pH to maintain the wastewater W at a slightly alkaline state suitable for microbial activity. The ability to decompose organic matter does not decrease.

■Nitrogen compounds contained in wastewater W are also effectively oxidized by microorganisms whose purification activity is enhanced by the porous calcium silicate hydrate particles 7a and 5a, and nitrification from ammonia nitrogen to nitrate nitrogen is promoted. Ru.

In addition, the porous calcium silicate hydrate granules 7a described above
, 5a further promotes nitrification of the nitrogen compounds.

■When wastewater W contains phosphorus compounds, phosphate ions in the phosphorus compounds are contained in porous calcium silicate hydrate particles 7
Since the phosphorus compounds are effectively adsorbed into the many fine voids of a and 5a, they can be removed at a high removal rate.

As mentioned above, the soil trench 1 of this embodiment has a very high ability to purify sewage W, so it is possible not only to ensure the safety and reliability of the soil trench, but also to make the facility equipment smaller than in the conventional example. You can also do it.

(3) When the wastewater W is continuously purified as described above, there is a concern that the soil trench 1 may become clogged.

However, in this example, porous calcium silicate granules? The permeability of wastewater W is increased by a and 5a, and the capillary siphon movement of the wastewater W is promoted more than in the conventional example. Because the purification activity is increased, clogging is less likely to occur, and even if it does occur, recovery through natural purification is faster than in conventional methods.

It should be noted that the present invention is not limited to the configuration of the above-mentioned embodiments, and may be modified and embodied as desired without departing from the spirit of the invention, for example, as described below.

(1) In the above embodiment, the water pipe surrounding layer section 7 and the lower layer section 5
Porous calcium silicate hydrate granules 7a, 5a in both layers of
However, even if porous calcium silicate hydrate granules are provided in only one layer, the above-mentioned effects can be achieved.

(2) When arranging the porous calcium silicate hydrate granules 7a in the water sprinkler pipe surrounding layer 7, the method of arrangement is not limited. For example, the porous calcium silicate hydrate granules 7a are placed alone in the portion directly in contact with the water sprinkler pipe 6,
Around it, gravel bodies 7b may be arranged alone or in combination with porous calcium silicate hydrate granules 7a.

(3) Porous calcium silicate hydrate granules 5 in the lower layer 5
When arranging a, the method of arrangement is not limited.

For example, the porous calcium silicate hydrate granules 5a are placed alone in the portion directly in contact with the water sprinkler pipe surrounding layer 7,
Below that, the sand body 5b can be arranged alone or in combination with the porous calcium silicate hydrate granules 5a.

(4) Furthermore, porous calcium silicate hydrate particles may be provided in the upper layer 9. As a result, the upper layer 29
As the microorganisms living in the wastewater W actively reproduce and the purification activity increases, the action of the microorganisms to supplement the microorganisms not included in the wastewater W increases.

[Effects of the invention] Since the soil trenches of claims 1 and 2 are configured as described above, they have excellent sewage purification ability, are less likely to be clogged, and can be made smaller in facility equipment. be effective.

[Brief explanation of the drawing]

FIG. 1 is a sectional view schematically showing an embodiment of a soil trench embodying the present invention, and FIG. 2 is a sectional view schematically showing a conventional soil trench. 4... Impermeable tank, 5a... Porous calcium silicate hydrate granules, 5b.
...Sand body, 6...Water pipe, 7a...Porous calcium silicate hydrate granule, 7b.
...Gravel body.

Claims (1)

[Claims] 1. A soil trench formed by disposing porous calcium silicate hydrate granules (7a) alone or in combination with gravel (7b) around a watering pipe (6). 2. Gutter-shaped impervious tank (4) installed below the water pipe (6)
A soil trench filled with porous calcium silicate hydrate granules (5a) alone or mixed with sand (5b).