JPS6295195A - Denitrification method by utilizing soil - Google Patents

Abstract

PURPOSE:To efficiently accelerate biological denitrification by alternately utilizing the plural troughs which are opened at the top end, are packed therein with packing materials such as gravel and are embedded in soil. CONSTITUTION:Sewage is admitted into the plural troughs 1-4 which are opened at least at the top ends, are packed therein with the packing materials such as gravel 7 and are embedded into a soil layer 8 so as to penetrate into the soil layer 8 around the troughs. The treated water is discharged from the other troughs. The inflow of the sewage into the troughs and the discharge of the treated water therefrom are periodically changed over and controlled at time differences for each of the troughs. As a result, the peripheries of the respective troughs alternately maintained under anaerobic and aerobic conditions, by which the biological denitrification is efficiently accelerated.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for treating wastewater using soil, and more particularly, to a denitrification method for biologically removing nitrogen compounds from wastewater.

[Conventional technology]

As a conventional denitrification treatment method of this kind, for example, Japanese Patent Publication No. 5
There is a method as shown in Japanese Patent No. 9-31400. In this method, a packed layer of sand, etc., a gravel layer, and aggregated soil are sequentially laminated inside an impermeable membrane, and sewage that flows intermittently from an inflow pipe is nitrated in the packed layer and gravel layer, and then Denitrification occurs in aggregate soil.

[Problem that the invention attempts to solve]

However, in the conventional denitrification method described above, since oxygen is supplied to the soil layer from above, it is difficult to perform sufficient nitric oxidation below the layer, making it difficult to carry out efficient denitrification treatment. . This invention was made to solve the above problems, and by alternately using each trough for the inflow of sewage and the discharge of treated water, the area around each trough is alternately kept under anaerobic and aerobic conditions, thereby creating a biological environment. The purpose is to obtain a denitrification method using soil that can efficiently promote denitrification.

[Means to solve the problem]

In the denitrification method of the present invention, sewage flows into at least one of a plurality of troughs that are open at least at the top end, filled with filler such as gravel, and buried in the soil layer, and is then transferred to the surrounding soil layer. The organic matter in this wastewater is oxidized and decomposed, nitrogen compounds are oxidized, and the treated water is discharged from other troughs, but by periodically switching between inflow and discharge from each trough, the surrounding soil layer is Repeatedly disgusted
It is placed under aerobic conditions to perform denitrification treatment.

[For use]

In this invention, when sewage flows into the trough, the sewage permeates into the surrounding soil layer from the open upper end of the trough, and the organic matter in the sewage is adsorbed by microorganisms in this soil layer, and is oxidized and removed. , the treated water is discharged from other troughs, but since each trough is periodically switched between inflow and discharge, the surrounding soil layer is periodically subjected to repeated anaerobic and aerobic conditions, thus denitrifying. is promoted. As wastewater continues to flow in, organic matter in the wastewater gradually begins to accumulate around the trough, and the surrounding soil layer also begins to become clogged. The time required for the mouth to become clogged is preferred as the inflow time for - times. The trough then enters the discharge process in a somewhat clogged state. After a while after switching to the discharge process, the wastewater flowing in from other troughs is oxidized and nitric acid begins to diffuse. This nitric acid is denitrified using organic matter accumulated in the soil layer. Moreover, since organic matter is removed by this denitrification, clogging of the soil layer is also reduced.

【Example】

FIG. 1 is a schematic plan view showing the flow of sewage in a sewage treatment apparatus used in the denitrification method using soil according to the present invention, and FIG. 2 is a front sectional view thereof. In the figure, reference numerals 1 to 4 indicate inflow and discharge troughs each having an open upper end, and has an inflow portion 5 at one end and an outflow portion 6 at the other end. These troughs 1 to 4 are each filled with gravel 7 and buried in a soil layer 8. In this embodiment, a bottom plate 9 is laid at the bottom of the trough buried part in the soil layer 8 to prevent wastewater from dissipating, and the troughs 1 to 4 are arranged in parallel on this bottom plate 9 at regular intervals. It is buried in soil layer 8. A wastewater inflow pipe 10 is connected to the inflow part 5 of each trough 1 to 4, and a treated water discharge pipe 11 is connected to the outflow part 6. Next, the operation for carrying out this invention will be explained. Sewage to be treated flows into the trough 1 from an inlet pipe 10, and after being treated is discharged from the discharge pipe 11 of another trough. This is sequentially switched periodically. That is, the inflow of wastewater and the discharge of treated water in each trough 1 to 4 are sequentially switched and controlled so that the time of inflow of wastewater and the time of discharge of treated water are shifted for each trough 1-4, as shown in the flowchart of FIG. 3, for example. be done. Normally, the sewage inflow is switched every few days, and in this example, the ratio of the sewage inflow time to the treated water discharge time is 1:3. When the inflow of sewage is finished, the inflowing sewage remains in the troughs 1 to 4, so at the beginning of the discharge process, the water stagnant in the troughs is drained and returned to the inflow side. In this way, the sewage that is switched and inflowed into the troughs 1 to 4 at different times permeates and diffuses into the surrounding soil layer 8 from the open upper end of each of the troughs 1 to 4. It collects in troughs 1 to 4 in the discharge process and is discharged from there as treated water. In this soil layer 8, BOD, SS, ammonia, etc. are oxidized and decomposed. Here, organic matter in the sewage is captured by the soil layer 8 around the trough into which the sewage is flowing, and the trough gradually begins to become clogged. In particular, when wastewater contains a large amount of ss, clogging progresses rapidly. The optimum timing for switching the inflow is just before this clogging progresses to a certain extent and becomes a hindrance to processing. Immediately after the inflow is stopped, the soil layer around the trough accumulates a lot of organic matter,
I'm having a hard time speaking to some extent. However, after switching the inflow,
These organic substances are oxidized and decomposed by oxidized nitrogen such as nitric acid that has flowed in and permeated from other troughs, eliminating clogging and denitrifying the trough. In addition, in the later stages of the discharge process, the soil layer around the trough becomes aerobic, and a certain amount of nitric acid accumulates there, so denitrification occurs here in the early stages of the next inflow process. Next, an example of experimental results will be shown. Inflow water quality Treated water quality P H7,77,2 B OD 172 1. O3
S 149 1.5T -
N 31.0 2.0NH4-
N 23.1 1.5NOx N
O,060,1ONO3-N
O,221,5T-P 4.93
0.20,゛, unit is mg//! (excluding <PH) T-N is Kjeldahl total nitrogen Thus, according to the method of this invention, by directly treating wastewater of the same quality as raw sewage, BOD, SS, etc. can be compared with conventional secondary treated water. Water quality equivalent to that obtained when other substances are treated can be obtained, and effective denitrification can also be performed. Note that since the troughs 1 to 4 are empty when switching the inflow, it is more effective to inflow a large amount at once, so an automatic siphon may be installed to allow the inflow.

【Effect of the invention】

As described above, in the present invention, since the inflow of wastewater and the discharge of treated water in a plurality of troughs are sequentially switched after a predetermined time has elapsed for each trough, denitrification is promoted in the vicinity of the troughs and the treatment is efficiently performed. In addition, by sequentially switching between the inflow of sewage and the discharge of treated water as described above, the clogging that occurs around the trough in the inflow process is effectively eliminated, so sewage with a higher concentration than conventional methods can be removed. can also be processed.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the flow of sewage in the sewage treatment equipment used in the denitrification method using soil according to the present invention.
~4 is the trough. Patent applicant Nishihara Environmental Health Research Institute Co., Ltd. 1,',
, 1 (2 others) - 1

Claims (1)

[Claims] Sewage flows into multiple troughs that are open at least at the top and are filled with gravel or other filler and buried in the soil layer, allowing this to permeate into the surrounding soil layer, and the treated water is discharged from other troughs. A denitrification method using soil that promotes denitrification treatment by regularly switching and controlling the inflow of sewage into the trough and the discharge of treated water with a time difference for each trough.