JPH05104085A - Purifying treatment of waste water - Google Patents

Abstract

PURPOSE:To remove not only a phosphorus component or an org. component but also a nitrogen component in the purifying treatment of waste water by simple constitution. CONSTITUTION:A broken stone bed 68, a lower purifying soil bed 66, a sand bed 64 and a surface rhizosphere soil bed 62 are successively formed on a bottom part in a layered form. A supply pipe 52 of waste water to be treated is embedded in the vicinity of the boundary of the surface rhizosphere soil bed 62 and the lower purifying soil bed 66 through the sand bed 64. A virescence plant 60 is planted in the ground surface of the surface rhizosphere soil bed 62 so as to extend the roots 60a of the plant 60 to the periphery of the supply pipe 52. The nitrogen component in waste water to be treated is absorbed by the virescence plant 60 and phosphorus or an org. component is adsorbed on the lower purifying soil bed 66 to be decomposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater purification treatment method capable of removing not only phosphorus and organic components in wastewater but also nitrogen.

[0002]

2. Description of the Related Art In recent years, with the development of resort areas and redevelopment of urban areas, there are many cases where various types of wastewater are discharged into public water areas. In such a case, in order to prevent water pollution of rivers, lakes and marshes as public water bodies that receive wastewater, especially the occurrence of water-bloom, red tide, etc. due to eutrophication, it is necessary to remove pollutants from wastewater before discharge. It is essential.

As a simple system for removing such pollutant components in waste water, a soil purification method utilizing the natural purification capacity has been conventionally used. This is to remove the pollutants in the wastewater by passing the wastewater through the soil, adsorbing the pollutants while passing through the soil, and further decomposing the pollutants by soil microorganisms.

[0004]

However, in such a conventional soil purification method, phosphorus and organic components in wastewater can be removed, but nitrogen components cannot be removed. was there.

On the other hand, since the plants planted on the soil surface absorb nitrogen components during the growth process, the inventors of the present invention can perform more advanced wastewater treatment by combining with the conventional soil purification method. I got the prospect of becoming.

The present invention has been made based on the above problems and findings, and its object is to provide a simple structure.
An object of the present invention is to provide a method for purifying wastewater that can remove not only phosphorus and organic components but also nitrogen components.

[0007]

In order to achieve the above object, the present invention provides a wastewater purification treatment method for purifying wastewater by passing wastewater through the soil, wherein the soil is a surface soil and a subsoil. And a plant is planted on the surface of the surface soil, and a passage is provided near the boundary between the surface soil and the lower layer soil for supplying treated wastewater. To do.

[0008]

With the above structure, a passage for supplying untreated wastewater is arranged near the boundary between the two layers of the surface soil and the lower soil, and plants are planted on the surface of the surface soil. ,
Phosphorus and other organic substances contained in the wastewater are adsorbed to the soil or decomposed by soil microorganisms to be removed, and the nitrogen component in the wastewater is absorbed by the plants through the roots of the plants planted on the surface soil surface. It

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a system diagram showing a test flow of a wastewater purification treatment method according to the present invention, and FIG. 2 is a partially cutaway side sectional view of a model soil tank used for a test of the wastewater purification treatment method according to the present invention.

As shown in FIG. 1, domestic wastewater artificially produced in an artificial sewage production plant 10 (BOD concentration 200
(ppm) flows into the combined septic tank 20 that uses both the anaerobic method and the aerobic method, and is subjected to biological treatment as a pretreatment. Then, the overflow water from the combined purification tank 20 flows into the pump pit 30, and is sent to the distribution tank 40 by the transfer pump 32 installed in the pump pit 30. In the distribution tank 40, the wastewater to be treated is distributed and supplied to each of the model soil tanks 50 installed at five locations. The properties of this treated wastewater are BOD1-5pp throughout the test period.
m, COD 3.1 to 4.2 ppm, total nitrogen (TN)
9.5 to 13.7 ppm, total phosphorus (TP) 3.4 to
It was 5.3 ppm.

Different soils are formed in each of the five model soil tanks 50 in order to compare their purifying effects, and different kinds of greening plants are planted on the surface of the surface soil. ..

The wastewater to be treated is supplied into the soil through a supply pipe 52 arranged between the surface soil and the lower soil of the soil formed in each model soil tank 50, and is purified. After that, it is led out from the model soil tank 50 through the water collecting pipe 54 provided at the bottom in the model soil tank 50, and the discharge box 70
It is discharged to the U-shaped groove 80 for discharge via.

The water passage for the wastewater to be treated described above is shown in FIG.
It is indicated by a thick line with an arrow inside.

Next, the structure of the model soil tank 50 will be described. As a soil tank used for the model soil tank 50, a box culvert 50a made of concrete, which is not easily affected by temperature changes, was used. In addition, its size is 2 m each for length and width as the minimum scale for observing and comparing the growth status of various planting plants and confirming the uniform supply status of wastewater to be treated.
In order to secure 30 to 40 cm as the surface rhizosphere soil, which is the surface soil on which the roots of planted plants grow, and also 30 to 40 cm as the lower layer purified soil, which is the lower soil, a height of 1 m
And Further, since it is necessary to collect the treated water after the purification treatment, the model soil tank 50 was installed on the ground.

Inside the box culvert 50a, as shown in FIG. 2, layered model soils are formed in this order from the bottom side to a crushed stone layer 68, a lower layer purified soil 66, a sand layer 64, and a surface rhizosphere soil 62. .. And surface rhizosphere soil 62
The surface rhizosphere soil 6
2 through the sand layer 64, the supply pipe 52 for the wastewater to be treated
Is buried.

The supply pipe 52 has a perforated pipe 52a provided with a large number of water permeation holes for allowing the treated wastewater flowing therein to permeate into the surrounding soil, and the perforated pipe 52a stably in the soil. It is composed of a bed 52b for supporting. Further, the nonwoven fabric 56 is wound around the perforated pipe 52a, and both ends thereof are extended in the radial direction of the perforated pipe 52a so that the wastewater to be treated is appropriately wet in the soil. ..

A green plant 60 such as turf is planted on the surface of the surface rhizosphere soil 62, and its root 60a is the surface rhizosphere soil 6
The inside of No. 2 grows and extends downward.

The crushed stone layer 68 at the lowermost portion is provided with a water collecting pipe 54 for collecting the highly-treated water that has been purified and discharging it to the outside of the model soil tank 50.

Next, the operation of this embodiment will be described in 1990.
A description will be given with reference to the results of the tests conducted from May to November 1990 using the test facility. Table 1 collectively shows combinations of greening plants 60, surface rhizosphere soil 62, and lower layer purified soil 66 in each model soil tank 50.

[0020] 1. Nitrogen (N) removal capacity From May to July during the test period, No. No. in which bentgrass was planted on the surface of the surface rhizosphere soil was used. One tank had a large amount of N removed, and the removal rate was 23 to 38%. On the other hand, from August to mid-October, No. 2 tanks, No. The amount of N removed in three tanks was large, and the removal rate was 23 to 33%.
In addition, No.
The four tanks had a removal amount of about 1 ppm throughout the entire test period, and the removal rate was about 10%. On the other hand, no. In the 5 tanks, the amount of N removed was as low as 0.6 ppm throughout the entire test period, and the removal rate was 5%.
It was about.

From the above results, (1) N removal ability is affected by the type of plant planted on the surface of the surface rhizosphere soil. (2) Model soil tank (No. 1 to No. 3) in which turf is planted
In the tank), the effect of removing N is greater than that in the model soil tank (No. 4 tank) in which Tamariu and Shibazakura are planted. (3) As a characteristic of each turf, bentgrass has a large amount of N removal from May to July, and Koroshiiba from August to October. It was confirmed. 2. Phosphorus (P) removal ability When examining the removal ability of P, both the raw water and the treated water account for phosphorus phosphate (PO) in the total phosphorus (TP).
₄ -P) for the ratio was 95% to 98% of were examined removal capability of PO ₄ -P principle.

No. In 2 tanks, PO throughout the entire test period
Most of _4- P was removed. No. 3 tanks, No.
4 tanks, No. In the 5 tanks, PO ₄ − from June to August
The absorption rate of P was 44 to 65%, but thereafter the removal rate deteriorated and decreased to 5 to 22%. No. In one tank, the removal rate was 30 to 40% throughout the entire test period.

From the above, it was confirmed that the removal ability of P was high in the model soil tank in which the black soil with high phosphoric acid absorption coefficient was used as the lower layer purified soil. 3. Relationship between Growth of Shiva and Total Nitrogen (TN) Removal Amount of the green plant 60 shown in Table 1 above. 1 tank to N
o. The three turf grasses were mowed almost regularly and their growth was investigated. As a result, it was confirmed from the relationship between the pruning yield of turfgrass and the amount of TN removed, that the amount of TN removed in each model soil tank increased as the growth amount of turf increased. Assuming that all the TN removed in the model soil tank was absorbed by the turf, the theoretical TN content of the turf is about 2.5-3.3%, but it was actually trimmed. The TN content of shiba is 2.1-
It was 4.1%, which was a value almost equivalent to the theoretical value.

From the above, No. 1 tank-No. It was confirmed that most of the TN removed in each of the three model soil tanks was absorbed by the turf growing on the surface of the surface rhizosphere soil 62.

The operation of this embodiment will be described based on the above test results. The treated wastewater is supplied by being buried in the model soil tank 50 near the boundary between the surface rhizosphere soil 62 and the lower layer purified soil 66. It flows through the inside of the perforated pipe 52a of the pipe 52 and permeates into the soil through a large number of water-permeable holes provided in the perforated pipe 52a. At this time, since the sand layer 64 having a high water permeability is formed around the perforated pipe 52a, the wastewater to be treated can easily exude from the perforated pipe 52a to the outside. Further, a non-woven fabric 56 is formed around the perforated pipe 52a.
Since it is wound and it extends between the sand layer 64 and the lower layer purified soil 66, the wastewater to be treated that has exuded from the perforated pipe 52a permeates along the non-woven fabric 56 and is deposited in the soil. The treated wastewater can be supplied uniformly.

The root 60a of the greening plant 60 planted on the surface of the surface rhizosphere soil 62 extends to the vicinity of the sand layer 64 in search of the treated wastewater that has penetrated into the soil and is contained in the treated wastewater. Since it significantly absorbs the fertilizer elements used, particularly nitrogen, the total nitrogen (TN) in the wastewater to be treated is effectively removed, and the greening plant 60 is provided with water and fertilizer.

The wastewater to be treated, which has not been absorbed by the green plant 60, passes through the lower-layer purified soil 66 and moves downward. In this process, the total phosphorus (TP) in the treated wastewater is adsorbed to the soil and removed, and at the same time, the pollutants such as organic substances in the treated wastewater are decomposed by soil microorganisms. Therefore, it is possible to carry out advanced wastewater treatment with a simple structure.

[0028]

As described in detail above, according to the wastewater purification method of the present invention, the passage for supplying the wastewater to be treated is provided near the boundary between the two layers of the surface soil and the lower soil. In addition, since plants were planted on the surface of the surface soil, phosphorus and other organic substances contained in the drainage are adsorbed to the soil or decomposed by soil microorganisms to be removed, and nitrogen components in the drainage are It is absorbed by the plant through the roots of the plant planted on the surface of the surface soil, and it is possible to remove not only phosphorus or organic components but also nitrogen components in the wastewater, and it is possible to prevent eutrophication of the wastewater.

[Brief description of drawings]

FIG. 1 is a system diagram showing a test flow of a wastewater purification treatment method according to the present invention.

FIG. 2 is a partially cutaway side sectional view of a model soil tank used for a test of a wastewater purification treatment method according to the present invention.

[Explanation of symbols]

 10 Artificial sewage production plant 20 Combined septic tank 30 Pump pit 40 Distribution tank 50 Model soil tank 52 Supply pipe 54 Water collection pipe 56 Nonwoven fabric 60 Green plant 62 Surface rhizosphere soil 64 Sand layer 66 Lower layer purification soil 68 Crushed stone layer

Claims (1)

[Claims] 1. A method for purifying wastewater, which comprises purifying wastewater by passing wastewater through the soil, wherein the soil is formed with two layers of surface soil and lower soil, and the surface soil has a plant. And a passage for supplying wastewater to be treated is disposed near the boundary between the surface soil and the lower soil.