JPH05138186A - Treatment of drainage discharged from purification tank - Google Patents

Abstract

PURPOSE:To remove excess nitrogen and phosphorus in drainage discharged from a purification tank at a low cost by providing a biological membrane tank wherein the contact material is packed in the inside of a basketlike body in a pretreatment water area having drainage temperature regulated to specified value and forming a space for storing a falling object in the lower part of the contact material and supplying denitrification bacteria, phosphoric acid cumulative bacteria and a carbon source to the biological membrane tank. CONSTITUTION:A pretreatment water area 1 is formed between a purification tank 1 and the discharge water area of a pond, lakes and marshes and a river into which drainage is discharged. The pretreatment water area 1 is formed so that drainage temperature is regulated to >=5 deg.C in a natural state when drainage is introduced thereinto from the purification tank 3. A biological membrane tank 2 provided in the pretreatment water area 1 is constituted by packing the contact material 5 in the inside of a basketlike body 4. A space for storing the falling object of sludge is formed in the lower part of the contact material 5. Furthermore denitrification bacteria, phosphoric acid cumulative bacteria and a carbon source such as metanol and cotton are supplied to the biological membrane tank 2 and stuck to the contact material 5. When drainage is discharged from the purification tank 3, drainage is introduced into the biological membrane tank 2. Nitrogen and phosphorus contained in drainage are efficiently removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment method for removing excess nitrogen and phosphorus contained in wastewater from a septic tank before being discharged into a pond, lake, river or the like.

[0002]

2. Description of the Related Art Generally, as a method for treating wastewater in a septic tank, a purification method represented by an activated sludge method is adopted. However, nitrogen contained in the treated water of domestic wastewater is generally 10 to 15 ppm, and phosphorus is 1 to 3 ppm.
However, the water quality called eutrophication is 0.4 pp nitrogen.
Although the concentration of m and phosphorus is higher than about 0.1 ppm, the removal rate of inorganic nutrients by the activated sludge method is only about 20%. Therefore, a large amount of inorganic nutrient salts such as nitrogen and phosphorus are still dissolved in the treated wastewater from the septic tank. Although the above wastewater is not covered by the legal regulation, it is nevertheless a direct cause of eutrophication in the water area of the discharge destination, and its utility value as a water quality source is reduced and reused. Not only is it costing a lot more, but it also has a negative impact on the ecosystem of water bodies and is one of the major environmental pollutions.

Water pollution and environmental pollution (deterioration) caused by the progress of eutrophication in rivers, lakes and marine areas are important problems, and quick solutions are required. It is clear from the revision. In particular, in resort facilities and the like, in order to eliminate the influence on the environment pollution due to eutrophication of the surrounding water area, the treated water generated in the facility must be discharged to the outside and must be stored in a closed water area such as an artificial pond. Therefore, eutrophication of the above waters is inevitably inevitable, and it is inevitable that the water will become unusable.
Similarly, even in a small-scale public sewerage treatment facility, discharging treated water to a river or the like is a serious cause of damaging the river ecosystem.

On the other hand, conventionally, a wastewater treatment facility was installed on land to further purify the wastewater. However, such a treatment facility is large in size, and is used for operating an aeration device, a water circulation device and the like. There is a drawback that the consumption of electric energy is large and the cost is high.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the wastewater from the septic tank is mainly composed of nitrate nitrogen N.
If it is O ₃ , and the water temperature of the waste water is normal, 2 degrees Celsius
Paying attention to the fact that the temperature is around 0 degree, and effectively utilizing the mechanism of denitrification and phosphorus fixation in the natural world, excess nitrogen and phosphorus contained in the wastewater from the septic tank can be stored in ponds, lakes, rivers, etc. It is an object of the present invention to provide a method for treating wastewater from a septic tank, which removes it at low cost before it is discharged to the discharge water area.

[0006]

In order to achieve the above object, the method for treating wastewater from a septic tank according to the present invention comprises a septic tank and ponds, lakes and rivers where the wastewater from the septic tank is discharged. In between, a pretreatment water area is formed in which the temperature of the wastewater when flowing from the septic tank in a natural state is maintained at 5 ° C or higher, and at least phosphoric acid in the wastewater is accumulated in the body in the pretreatment water area. A biofilm tank filled with a contact material suitable as a medium for denitrifying bacteria that reduces nitrate nitrogen in wastewater to nitrogen gas in phosphate-accumulating bacteria is installed, and sludge is provided below the contact material. A space for accumulating fallen objects is formed, and denitrifying bacteria, phosphoric acid accumulating bacteria and carbon sources such as methanol and cotton are further supplied to the biofilm tank.

As the contact material inside the cage, it is preferable to provide a contact material having coarse mesh and free entry and exit of water on the outside and a contact material having fine mesh and a large contact area on the inside.

[0008]

INDUSTRIAL APPLICABILITY According to the present invention, the flow of waste water from a septic tank and the characteristics of the waste water, that is, the waste water temperature is a temperature at which microbial activity can be kept high, and the organic matter in the waste water can be reused as a nutrient source, Utilizing that the nitrogen in the wastewater is nitrate nitrogen that promotes nitric acid respiration mainly by various denitrifying bacteria,
Wastewater treatment is carried out by efficiently promoting the biochemical reaction of natural denitrification and dephosphorization by denitrifying bacteria and phosphate accumulating bacteria within the artificially created biofilm tank microbial environment. Since the discharged wastewater removes nitrogen and phosphorus from the wastewater in the pretreatment water area before it is released to the water areas such as ponds, swamps, lakes, rivers, etc., the progress of eutrophication in the entire discharge water area Can be prevented in advance. In particular, phosphorus is an element required by all organisms in a considerable amount, and it has been confirmed that water-soluble phosphorus is directly proportional to the growth rate of algae. It is possible to limit or prevent the occurrence of water-bloom due to eutrophication in the effluent area by preliminarily removing it in the limited pretreatment area.

Further, according to the present invention, a large onshore facility and its installation place are unnecessary, running costs such as electric energy such as aeration, pumping, heating and heat retention are not required, and sludge treatment is almost unnecessary. In addition, since sterilization with a chemical agent is not performed, maintenance management is easy, and low-cost labor-saving purification processing can be realized.

Furthermore, since the entire biofilm tank is below the surface of the water, the landscape is hardly damaged.

Therefore, the present invention is effective for eutrophication countermeasures such as water purification of ponds of resort facilities, storage pools of pretreated water for medium-scale sewerage, pretreatment of river discharge such as rural village drainage.

As a contact material inside the cage, when a contact material having coarse mesh is provided on the outer side and a contact material having fine mesh is provided on the inner side, the former contact material allows water to freely pass therethrough. Aerobic hydrosphere that promotes the growth of microorganisms useful for phosphorus fixation. In addition, since the latter contact material has a large contact area with microorganisms, it is easy for microorganisms to adhere, more microorganisms grow than the former contact material, the amount of dissolved oxygen is increased, and anaerobic suitable for denitrifying bacteria. Hydrosphere is formed. Therefore, since a complex microbial ecosystem is artificially created as a whole, efficient purification treatment can be performed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described below with reference to the drawings.
And a special biofilm tank 2 is installed in the pretreated water area 1.

The pretreated water area 1 is, as shown in FIG. 1, a septic tank 3
And the drainage water of the septic tank 3 are discharged between the pond, lake and river, and the discharge water area of the river, and the drainage temperature when flowing from the septic tank 3 is 5 degrees Celsius or more in a natural state. Has been formed. Generally, the water temperature of the wastewater from the septic tank 3 is 20 degrees Celsius or more, and if the pretreatment water area 1 is formed at a point not far from the septic tank 3, the water temperature of the wastewater flowing into this will be 5 degrees Celsius in a natural state. Can be held more than once.

The pretreatment water area 1 is provided before the discharge water area because the wastewater is not discharged from the septic tank 3 but is discharged after a certain period of time, and is retained to an extent that can be purified. This is because the natural flow of drainage can be utilized without resorting to mechanical means such as a pump that requires electric energy. The pretreated water area 1 is preferably such that wastewater can stay for about 2 to 3 days.

The water temperature condition of 5 degrees Celsius is 5 degrees Celsius due to the symbiotic action of microorganisms in the biofilm tank 2 described later.
This is because an active ecosystem has been observed even in terms of temperature, and purification can be promoted without requiring electric energy for heating and heat retention.

Next, as shown in FIG. 2, the biofilm tank 2 installed in the pretreated water area 1 is formed by filling the cage 4 with the contact material 5, and the cage 4 is , A large basket-like shape is formed by combining rods made of lattice-shaped glass fiber, and the float 7 is attached so that the whole has buoyancy.

The contact material 5 includes a contact material 5a having coarse meshes and free water from entering and leaving, and a contact material 5b having fine meshes and a large contact area.
It is preferable to be composed of In this case, a small triangular cylinder-shaped cage 4a is further arranged inside the cage-shaped body 4 by hanging or the like, and a coarse contact material 5a is provided on the outer side of the cage 4a.
Then, the inside of the cage 4a is filled with the fine contact material 5b. Further, the coarse contact material 5a uses, as the contact material 5a, a bios (trade name) or the like formed by combining a polypropylene face plate having holes or notches to form a spherical shape, and has a fine contact area. As the contact material 5b having a large number, a continuous loop-shaped fiber in a string shape or a felt material processed into a string shape, a band shape or the like (for example, a product name "Nefmac" etc.) is used, and this is used as a cage. It may be stretched on 4a.

A space 6 is formed below the contact material 5 for accumulating sludge falling matter. In this case, when the water depth of the pretreatment water area 1 is shallow, and when the contact material 5a is bios having a specific gravity smaller than that of water, the contact material 5a is placed on the upper portion 80 of the cage 4.
%, And the space 6 is formed so as not to reach the lower end of the cage 4. When the water is deep, it is held at a low position by an anchor or the like, and the whole is floated by the float 7.

It should be noted that the biofilm tank 2 is used in accordance with the inflow amount of waste water.
By appropriately arranging the partition plate 8 shown in FIG.
The retention time of the waste water in the tank may be adjusted to be long. Further, a plurality of units of the biofilm tank 2 may be provided depending on the size of the pretreatment pond.

Further, a denitrifying bacterium and a phosphoric acid accumulating bacterium and a carbon source such as methanol and cotton are supplied to the biofilm tank 2 and attached to the contact material 5. A typical denitrifying bacterium is Achromoba
cter, Alcaligenes, Bacillu
s, Hypomicrobium, Micrococc
us, Paraacoccus, Pseudomona
s, Thibacillus, and the like. In addition, examples of the phosphate-accumulating bacteria include PAB6 (registered microorganism). These denitrifying bacteria and phosphoric acid accumulating bacteria may be supplied by encapsulating the seed bacteria.

In the above structure, when the wastewater is discharged from the septic tank 3, the wastewater enters the biofilm tank 2, and nitrogen and phosphorus contained in the wastewater are efficiently removed as follows.

In the biofilm tank 2, the contact material 5a having a coarse mesh
The free passage of water allows the formation of an aerobic hydrosphere that does not become occluded and promotes the growth of microorganisms useful for phosphorus fixation. Further, since the contact material 5b having fine meshes has a large contact area of microorganisms, the microorganisms are easily attached to the contact material 5a having a coarse mesh.
Since more microorganisms grow and the density of microorganisms increases, the amount of dissolved oxygen consumed becomes large and an anaerobic hydrosphere suitable for denitrifying bacteria is formed. Thus, an overall complex microbial ecosystem is artificially created. In this way, the whole biofilm becomes a complicated environment, symbiosis, food chain becomes longer,
Since the energy is converted into a large amount, the purification efficiency becomes very high.

The denitrifying bacteria can grow under aerobic and anaerobic conditions, but if nitric acid or nitrous acid is present under anaerobic conditions and a suitable carbon source is present, nitric acid respiration is started, and nitric acid and nitrite are converted to nitrogen gas. It causes a biochemical reaction that reduces to. That is,
In general, nitrogen dissolved in water is nitrified to NH ₄ —NO ₂ —NO ₃ by aeration (oxidation action) by a fountain or a waterfall, and further nitrogen is gasified and denitrified by NO ₃ —N ₂ O—N ₂ . It However, the nitrogen in the waste water from the septic tank 3 is mainly nitrate nitrogen NO ₃ . As described above, since most of the nitrogen in the waste water is nitrate nitrogen, the biofilm tank 2 must be supplied with abundant nitric acid or nitrous acid that promotes nitric acid respiration, which is an essential energy source for various denitrifying bacteria. become.

Moreover, the water temperature of the wastewater from the septic tank 3 is usually 20 ° C. or higher, the microbial activity of the biofilm tank 2 is kept high, and the BOD substances and SS in the wastewater adhere to the contact material 5b to cause various microorganisms. Will be reused as a nutrient source (carbon source). Furthermore, the BOD value contained in the wastewater is 14
When the concentration is higher than ppm, the OD value becomes 0.5 ppm due to the consumption of dissolved oxygen, so that the microbial environment in the central part of the biofilm tank 2 is easily anaerobic and becomes an environment suitable as a medium for denitrifying bacteria. ..

Since the amount of BOD substances and SS substances contained in the waste water is as small as about 10 ppm, it is necessary to artificially reinforce the substances serving as carbon sources to supply the growth energy of microorganisms. Therefore, the optimum pH (7
To 7.5), add methanol etc. as a necessary carbon source regularly, or attach cotton etc.

By the above, the nitrogen in the waste water is efficiently removed as shown in FIG. This means that nitrogen fertilizers such as ammonium sulphate sprayed on the paddy fields are immediately converted into nitrogen gas by denitrifying bacteria in the reducing layer under a few millimeters in the soil and released into the atmosphere, impairing the fertilizing effect. It is also clear from the process of nitrogen cycling.

Next, although phosphorus is an essential element for the growth of organisms and the production of energy substances, it has been reported that microorganisms generally ingest phosphorus excessively. Therefore, in addition to the aerobic microorganisms grown in the contact material 5a of the biofilm tank 2 ingesting phosphorus, when the denitrifying bacteria, which are heterotrophic bacteria, grow in the contact material 5b as described above, the substances contained in the wastewater are nourished. Incorporates carbon and phosphorus as sources, thereby simultaneously reducing phosphorus. This is because phosphorus is fixed to the organism, and therefore, when it is peeled from the biofilm tank 2, it falls into the sludge removal space 6 below the biofilm tank 2. By removing this sludge, it is possible to prevent the diffusion into the discharge water area. However, phosphorus-incorporating microbes serve as a nutrient source for larger protozoa, which are assimilated and catabolized by the food chain, which is digested by larger organisms. The same applies to BOD substances, SS substances, etc. contained in wastewater. Therefore, compared to the activated sludge method, the amount of sludge generated is very small, and thus sludge treatment is almost unnecessary.

As described above, according to the method of treating waste water, the flow of waste water from the septic tank 3 and the characteristics of the waste water, that is, the waste water temperature is a temperature at which the microbial activity can be kept high, the organic matter (BOD substance in the waste water) , SS, etc.) can be reused as a nutrient source, and the nitrogen in the wastewater is nitrate nitrogen that mainly promotes nitric acid respiration of various denitrifying bacteria. Wastewater treatment is carried out by efficiently promoting natural denitrification and dephosphorization biochemical reactions inside the wastewater, and the wastewater discharged from the septic tank 3 is discharged to the water areas such as ponds, swamps, lakes and rivers. Since nitrogen and phosphorus in the wastewater are removed before the start of effluent, it is possible to prevent the progress of eutrophication in the entire discharge water area. In particular, phosphorus is an element required by all organisms in a considerable amount, and it has been confirmed that water-soluble phosphorus is directly proportional to the growth rate of algae. By preliminarily removing it in the limited pretreatment water area 1, it is possible to limit or prevent the generation of water-bloom due to eutrophication of the discharge water area. It should be noted that the progress of the above-described nitrogen and phosphorus removal processing is briefly illustrated in FIG.

In addition, the wastewater treatment method does not require a large onshore facility or its installation site, and therefore requires no aeration, pumping,
It does not require running costs such as electric energy such as heating and heat retention, hardly requires sludge treatment, and does not perform sterilization with chemicals, so maintenance is easy, low cost and labor-saving purification treatment is realized. can do.

Furthermore, since the entire biofilm tank 2 is under the surface of the water, the landscape is hardly damaged.

As the contact material inside the cage, the coarse contact material 5a is provided on the outer side, and the fine contact material 5b is provided on the inner side. Therefore, the former contact material 5a allows water to pass freely,
An aerobic hydrosphere is formed that does not clog and promotes the growth of microorganisms useful for phosphorus fixation. Also, the latter contact material 5
Since b has a large contact area with microorganisms, the microorganisms are likely to adhere to it, and more microorganisms grow than the former contact material 5a,
The consumption of dissolved oxygen becomes large, and an anaerobic hydrosphere suitable for denitrifying bacteria is formed. Therefore, since a complex microbial ecosystem is artificially created as a whole, efficient purification treatment can be performed.

The offensive odor generated by creating the anaerobic hydrosphere may be solved by using, for example, BSK bacteria (registered microorganism).

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a method for treating wastewater from a septic tank according to the present invention.

FIG. 2 is a cross-sectional view of a biofilm tank.

FIG. 3 is an explanatory diagram of a state in which a partition plate is provided in the biofilm tank.

FIG. 4 is an explanatory diagram of a process of removing nitrogen and phosphorus.

[Explanation of symbols]

 1 Pretreated water area 2 Biofilm tank 3 Septic tank 4 Contact material 5 Basket

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C02F 3/34 101 D 7158-4D 9/00 A 6647-4D

Claims (2)

[Claims] 1. The wastewater temperature when the wastewater from the septic tank naturally flows between the septic tank and the discharge area of the pond, lake, or river where the wastewater from the septic tank is discharged is maintained at 5 degrees Celsius or more. Suitable as a culture medium for phosphate-accumulating bacteria that form a pretreated water area that accumulates at least phosphoric acid in wastewater in the body and denitrifying bacteria that reduce nitrate nitrogen in wastewater to nitrogen gas in the pretreated water area A biofilm tank filled with the contact material inside the cage is provided, and a space for accumulating sludge falling matter is formed below the contact material, and further the denitrifying bacteria and the phosphoric acid accumulating bacteria are accumulated in the biofilm tank. A method for treating wastewater from a septic tank, which is characterized by supplying a carbon source such as methanol or cotton. 2. The contact material inside the basket-like body is provided with a contact material having coarse mesh and free entry and exit of water on the outer side, and a contact material having fine mesh and a large contact area on the inner side. Item 1. A method for treating wastewater from a septic tank according to item 1.