JPS60166094A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To prevent the decomposition of a lower layer part due to the increase of anaerobic organism layers by returning a part of a treated product obtained in the oxidation treatment in a contact oxidation vessel to a contact digestion vessel, and treating again the product along with low-concn. waste water. CONSTITUTION:The purified waste water is charged into an aerobic contact oxidation vessel B through a discharge pipe 9 at the upper part of a vessel, circulated in the vessel B by a circulating flow of air supplied from an air supply pipe 13, brought into contact with an aerobic organism film of an aerobic filter bed 12, and purified by the oxidation of low molecular organic substances to gaseous carbonic acid and water and the oxidation of ammonium ions to nitric acid and nitrous acid. The purified water is discharged to the outside of the system through a purified water discharge pipe 14. A part of the purified water is simultaneously returned to a contact digestion vessel A through a purified water return pipe 15 equipped with a pump, and anaerobically treated along with the newly supplied waste water. The denitrification by the reduction of nitric acid, nitrous acid, etc. formed in the contact oxidation vessel B is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating wastewater, and more specifically, the present invention relates to a method for treating wastewater, and more specifically, a method for treating low-concentration wastewater after solid-liquid separation in a pond, sand pond, etc. using a biochemical method that combines anaerobic biological treatment and aerobic biological treatment. The present invention relates to a method for purification by treatment.

Biochemical treatment of wastewater has the great advantage of low energy consumption, unlike physicochemical treatments such as solid-liquid separation by adding flocculants, wet oxidation of waste liquid, dewatering, drying and incineration of sludge.

Therefore, biochemical treatment using aerobic microorganisms is currently the mainstream method of purifying sewage, which is mainly miscellaneous wastewater such as kitchen wastewater and flush toilet wastewater, in urban areas.

This biochemical treatment using aerobic microorganisms can be roughly divided into two types: the suspended organism method and the fixed biofilm method. The suspended organism method further includes the standard activated sludge method and the long-time aeration method. The former is suitable for large-scale, high-grade treatment, but requires advanced techniques for cultivation and requires a great deal of effort for maintenance and management. The latter method is suitable for medium-scale treatment and generates a small amount of sludge, but it has the drawback of requiring a long residence time and being susceptible to load fluctuations.

In addition, fixed biofilm methods include the trickling filter method, rotating disk method, and contact oxidation method. All of these methods are resistant to load fluctuations because they form food chains with biofilms or a combination of various microbial films. Although it is easy to maintain and manage and is suitable for small-scale processing, it has the disadvantage of not being able to handle increases in processing volume. As described above, biochemical treatment using aerobic microorganisms has various advantages and disadvantages, but a further problem is the treatment of nitric acid and nitrite produced by the action of aerobic microorganisms.

In view of the above problems, the inventors of the present invention have investigated various wastewater treatment methods that combine aerobic biological treatment and anaerobic biological treatment. In addition, aerobic biological treatment uses a contact oxidation tank that is resistant to load fluctuations and is easy to maintain, and the desorbed water in the contact oxidation tank is returned to the contact digestion tank, making it possible to achieve both anaerobic biological treatment and The present invention was completed based on the discovery that not only the advantages of aerobic biological treatment are fully utilized, but also the amount of sludge generated is significantly reduced.

That is, in the wastewater treatment method according to the present invention, low-concentration wastewater after solid-liquid separation in a settling basin or the like is supplied to a contact digestion tank equipped with multiple stages of anaerobic filter beds for purification treatment, and the treated water is further purified. The treated product obtained in the oxidation treatment is separated into digested sludge and desorbed water, and the separated desorbed water is returned to the contact oxidation tank to reduce the low concentration. The system is characterized in that it is purified together with the wastewater again, while the separated digested sludge is extracted from the system.

According to the method of the present invention, wastewater is alternately subjected to anaerobic treatment and aerobic treatment while passing through each digit, decomposing organic polymers into low molecular weight molecules, decomposing low molecular weight molecules into carbon dioxide gas, water, etc., and decomposing nitric acid gas. Efficient purification treatment such as denitrification by reduction of ions, etc., and stable high-grade treatment that is resistant to load fluctuations can be achieved, making it possible to significantly reduce maintenance costs and construction costs.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, A shows a contact digestion tank and B shows a contact oxidation tank. The contact digestion tank A has a hopper-shaped part 2 at the bottom of a cylindrical main body 1, and an inflow part 3 that communicates with a sand settling basin (not shown) opens at the upper end of the main body 1 through a top plate 4. . 5
is a wastewater inflow pipe vertically installed in the center of the tank, the upper end of which is connected to the opening, and the lower end of which is open at the bottom of the hopper-shaped portion 2.

In the contact digestion tank A, a plurality of stages of anaerobic filter beds 6, 6, . . . are arranged with a required interval 7 in the vertical direction. In addition, a sludge drawing pipe 8 is provided at the lower end of the tank A, and
A treated water withdrawal pipe 9 communicating with the contact oxidation tank B is provided in the upper part.

In the contact digestion tank A, it is important to provide multiple upper and lower anaerobic filter beds 6 with good biofilm adhesion. That is, in anaerobic filter beds, biofilms generally have weak adhesion, and if the flow rate is too high or the flow is disturbed, the biofilms will peel off and the treatment effect will be significantly reduced. Therefore, the filter bed 6
As the filter media used for forming the filter, materials such as granular ice made of plastic, such as ice cubes and crushed stone, and materials that have good adhesion to biofilms, such as plate-shaped bodies, cylindrical bodies, and net-shaped bodies, are used. Then, filter media are stacked to a required thickness to form several stages of filter beds 6, and gaps 7 of a required height are provided between each filter bed 6. By arranging the filter beds 6 in multiple stages and providing appropriate intervals between the filter beds in this manner, the wastewater uniformly contacts the filter media, the turbulent flow state is rectified, and the treatment effect is significantly enhanced.

In the contact oxidation tank B, like the contact digestion tank A, a vertical flow pipe 11 is vertically installed in the center of a cylindrical body 10 whose lower part is a part of the hopper, and an aerobic filter bed 12 is arranged around it. The end of the air supply pipe 13 is opened at the lower end of the flow pipe 11 . Further, a purified water outflow pipe 14 is provided in the upper part of the tank B, a part of which is branched and connected with a purified water return pipe 15 that communicates with the inflow part 3 of the tank A, and furthermore, a sludge withdrawal pipe 16 is provided at the lower end.
is provided.・Next, we will explain the purification effect of wastewater.

The wastewater (desorbed water) after solid-liquid separation in a settling basin or the like is supplied from the inflow section 3 to the lower part of the contact digestion tank A through the inflow pipe 5, and flows upward as shown by the arrow. The liquid passes sequentially from the lower stage to the upper stage of the anaerobic filter bed 6, comes into contact with the anaerobic biofilm formed on the anaerobic filter bed 6, or decomposes low molecular weight organic matter by facultative anaerobes present in the liquid. oxidation, generation of ammonium ions (NH4), etc. occur, resulting in purification. On this occasion,
The wastewater whose flow is disturbed by passing through the lower filter bed 6 is
Before entering the next filter bed, the flow is rectified by passing through the gap 7 between the filter beds, and the flow into the next filter bed 6 is made uniform, resulting in uniform contact conditions with the filter medium. The purified wastewater passes through the discharge pipe 9 in the upper part of the tank and then enters the aerobic contact oxidation tank I3, and is circulated in tank B by the supply air circulation flow from the air supply pipe 13, and then flows through the aerobic filter bed 12. Upon contact with airborne biofilms, low-molecular organic matter is oxidized and decomposed into carbon dioxide and water.
It is purified by oxidation of ammonium ions to nitric acid and nitrous acid. This purified water is discharged to the outside through the purified water outflow pipe 14, and a part of it is returned to the contact digestion tank A through the purified water return pipe 15 equipped with a pump, where it is anaerobically treated together with newly supplied wastewater. , Denitrification occurs due to the reduction of nitric acid, nitrous acid, etc. generated in the catalytic oxidation tank B along with the decomposition of the polymer (some substances) into low molecular weight substances.

Excess sludge produced in the contact digestion tanks and oxidation tanks A and B is normally discharged from the sludge withdrawal pipes 8 and 16 through the sludge return pipe 17 and treated together with the solids separated in the settling basin or the like or alone. However, a portion may be returned to the digestion tank B for reprocessing.

In the above embodiment, the wastewater flows into the contact digestion tank A from the upper part of the tank A, but if the wastewater flows uniformly into the bottom stage of the filter bed, it is possible to As shown in the diagram, a waste water inlet pipe 18 may be provided at the bottom of the tank A.

As described above, according to the method of the present invention, wastewater is alternately subjected to anaerobic treatment and aerobic treatment while passing through various types, and further, the treated product is separated into digested sludge and desorbed water in contact oxidation tank B. , this separated desorbed water is returned to the contact digester,
Since it is subjected to anaerobic treatment and aerobic treatment alternately again, organic polymers are decomposed into low molecular weight molecules, low molecular carbon dioxide gas,
Denitrification by decomposition of water, etc. and reduction of nitrate ions, etc. proceed sufficiently, and stable high-grade purification treatment is performed.

FIG. 2 shows another example of a contact digester for carrying out the invention. That is, the contact digestion tank A' has a hopper-shaped part 2 at the bottom.
On the top plate 4 of the cylindrical body 1, there is a partition wall 19 that partitions the left and right sides.
is installed vertically, and anaerobic filter beds 6 are provided in multiple stages above and below on both sides, similar to the case shown in FIG. In this case, the wastewater passes through one side of the contact digestion tank A' as a downward flow from the upper stage to the lower stage as shown by the arrow, and then passes through the contact digestion tank A' as an upward flow from the lower stage to the upper stage due to other forces. Similarly, it is purified by coming into contact with an anaerobic biofilm. At this time, the inflow direction of wastewater is downward, so
Sedimentation and separation of digested sludge is efficiently performed, and clogging of the anaerobic filter bed 6 can be prevented by switching the inflow direction of wastewater at predetermined intervals.

FIG. 3 shows another example of a contact digester for carrying out the invention. That is, in the contact digestion tank A', the wastewater inflow pipe 5 and the partition wall 19 in the cylindrical main body 1 shown in FIGS. A wastewater supply dispersion nozzle 20 is positioned below the lowest filter bed 6, and wastewater is supplied from the bottom of the contact digestion tank A'. In this case, compared with Fig. 1 and Fig. 2, the internal structure of the contact digester l\' is simple, so the manufacturing cost is low, and since the waste water is supplied through the dispersion nozzle 20, the anaerobic filter bed This has the effect of making the contact more uniform.

FIG. 4B shows another contact material used in the anaerobic filter bed of the present invention.

That is, the contact material C consists of dish-shaped bodies 21 and 22 having different large and small diameters.
(for example, 5 to 10 cm in diameter) are provided in multiple stages vertically at appropriate intervals using connecting members 23.

The dish-shaped bodies 21 and 22 are connected with each other with the central four parts 24 facing upward, and each has a plurality of notches 25 on its outer peripheral edge.
has been established. The plate-like bodies 21 and 22 are made of corrosion-resistant metal, plastic, or plate material, and the connecting member 23 may be made of any material that can fix the plate-like body, such as a rod shape, a string shape, or a pure shape.

When the anaerobic filter bed 6 shown in FIGS. 1 to 3 is constructed using this contact material C, the following effects can be obtained. That is, anaerobic microorganisms have weaker adhesion to the filter bed than aerobic microorganisms, and when a biofilm forms a layer, it tends to easily peel off and fall off, reducing the ability to purify sewage. However, when the contact material C is used in the anaerobic filter bed as in this example, the anaerobic biofilm is formed at the center of the horizontal dish-shaped body 21+22! ! Part 7 2
There is no risk of adhesion to, formation of, and peeling off from the anaerobic treatment. Furthermore, when the anaerobic biofilm is formed beyond a certain limit in the central four parts 24, the notch 25 at the outer periphery prevents the rotting phenomenon of the lower layer caused by an excessive increase in the anaerobic biofilm layer. be able to. Also, unlike the so-called packed type anaerobic filter bed 6 shown in Figures 1 to 3, the filter medium is not clogged with anaerobic biofilm, and the filter bed is extremely easy to remove and replace. can be done.

Next, the conventional method and the present invention will be compared.

Even with the standard activated sludge method, which is considered the highest grade of conventional sewage treatment, the BOD removal rate is limited to 90%, and the BOD removal rate of inflow wastewater is
When the D concentration is 200mg/l, the treated water is 20mg/l
becomes. Furthermore, if the BOD concentration is 200 mg/l or more or the water temperature is 10° C. or less, and the residence time is too long, it will be difficult to manage the activated sludge, and the BOD removal rate will decline sharply.

In contrast, in the present invention, the BOD removal rate is always 95%.
For example, the BOD of inflow sewage is 20011.
In the case of 1 g/l, the BoD of treated water is 10 mg/l or less. In addition, even if the BOD of inflow wastewater reaches a concentration of 200 mg/1 or more, it is possible to prevent contact with contact digestion tank A and contact oxidation tank A by appropriately changing and combining the respective residence times in contact digestion tank A and contact oxidation tank B. By installing the oxidation tanks B in multiple stages, it is also possible to achieve a BOD removal rate of 97% or more.

To give an example of a combination of changing residence times, if the BOD of inflow wastewater is 300h+H/l, and the residence times in contact digestion tank A and contact oxidation tank B are each set to 30.10 hours, various A, The BOD of treated water purified by B is 90 mH/l and 9+og/l, respectively.
The OD removal rate is 97%. Also, at the same BOD concentration,
When the residence time of each type A and B is set to 48.15 hours, the BOD of treated water is 75n+g/l, 7.5m
g/l, and the final BOD removal rate reaches 97.5%.

Further, according to the present invention, the BOD removal rate in contact oxidation tank B is 70% or more, so BOD removal rate in contact oxidation tank B is
The amount of removal is reduced, the amount of air required is small, and the power consumption of the blower, which accounts for most of the power for water treatment, is reduced to about 172 compared to conventional methods, significantly reducing power consumption.

Furthermore, even with the contact oxidation method, which is said to produce a small amount of sludge, the amount of excess sludge is 20 to 30% of the amount of BOD removed.
However, in the present invention, the amount is extremely small, and is only about 2% of the removed BOD.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of a purifying device for implementing the present invention, FIGS. 2 and 3 are explanatory diagrams similarly showing other examples of the purifying device, and FIG. The contact structure of the pond for implementation is shown, with A being a plan view and the mouth being a sectional view taken along line a-a. A, A', A'... Contact digestion tank, B... Contact oxidation tank, C... Contact material, 1.10... Cylindrical body, 6.
... Anaerobic filter bed, 7 ... Interval, 12 ... Aerobic filter bed, 15 ... Purified water return pipe, 19 ... Partition wall, 20 ...
Distributed supply nozzle, 21° 22... dish-shaped body, 23...
Connecting material. Figure 1 L-□-, -2-1-111 (a) (b) Procedural amendment (voluntary) May 4, 1985 1, Indication of the case 1985 Patent Application No. 18569 2, Name of the invention Wastewater treatment method 3, Relationship to the case of the person making the amendment Patent applicant address 3-26-8 Denenchofu, Ota-ku, Tokyo Name
Shoji Hiraoka 4, Agent fi281-0808 Address: Jobebashi Building, 2-11-2 Yaesu, Chuo-ku, Tokyo (
6. Subject of amendment (1) "Claims" column of the specification (2) "Detailed description of the invention" column of the specification
856.9) 1) The claims of the specification of the present application are amended as follows. Low-concentration wastewater after solid-liquid separation in a settling basin etc. is supplied to a contact digestion tank equipped with multiple stages of anaerobic filter beds for purification treatment, and the treated water is further supplied to a contact oxidation tank for oxidation treatment. A method for treating low-concentration wastewater, characterized in that two plates of treated products obtained in the oxidation treatment are returned to a sieve contact digestion tank and purified again together with the low-concentration wastewater. 2) "Sand basin" on page 1, line 16 of the specification of the present application is corrected to "sand basin". 3) Correct "mo" in line 13 of page 2 to "ha". 4) Correct "Weak against load fluctuations: 0" on the 14th line to "Processing performance is also not very good." 5) "Desorbed water" on page 3, line 10 is corrected to "part of the treated product." 6) In lines 19 and 20 of the same, "separate into d-containing water and desorbed water, and the separated desorption" is corrected to "a part of". 7) Page 4, 1 of the same Delete ``mizuwa'' in line 1. 8) Delete [Meanwhile, the separated digested sludge is extracted from the system] in the second and third lines. 9) Correct "wastewater (desorbed water)" on page 3, line 10 of the same page to "low concentration wastewater." 10) Delete "or by facultative anaerobes present in the liquid" in lines 14-15. 11) Correct rBJ on page 7, line 19 to rAJ. 12) Correct "de" in line 7 of page 8 to "garano". 13) Lines 7 to 9 [1 for digested sludge and desorbed water]
This separated desorbed water is removed. 14) Page 9, lines 3 to 7 [In this case, wastewater...
... can be prevented. ” to be deleted. 15) "A'" on the 9th line, 14th line, and 16th line
” are respectively corrected to rA”J. 16) In the 19th line of the same line, next to “It has the effect of...”, change the line to “In addition, the above contact digesters A and A'
. It is more preferable to provide a plurality of each of A" and contact oxidation tank B, and treat the wastewater by flowing it through these plurality of tanks in series." 17) Change j300J in line 7 of page 12 to [200J, change “30, 10J” in lines 8 to 9 to [12,5J, change “90” and “9” in line 10 to “ 60” and “6
”, respectively. 18) Delete "Also, the same BOD! One degree reaches 97.5%." in the 11th to 15th lines. 19) Change “2” in the 5th line of page 513 to “5-15”
Correct. 20) Change rA, A', A' J in the 12th line to [A,
A'. Correct to A″] Patent applicant Shoji Hiraoka

Claims (1)

[Claims] Low-concentration wastewater after solid-liquid separation in a settling pond or the like is supplied to a contact digestion tank equipped with multiple stages of anaerobic filter beds for purification treatment, and the treated water is further supplied to a contact oxidation tank for oxidation treatment. and separating the treated product obtained in the oxidation treatment into digested sludge and desorbed water, and returning the separated desorbed water to the contact digestion tank and purifying it again together with the low concentration wastewater;
A low-concentration wastewater treatment method characterized by extracting the separated digestion sludge from the system.