JPH0461993A - Method and apparatus for biological nitration and denitrification of organic polluted water - Google Patents

Abstract

PURPOSE:To simultaneously carry out the removal of residual SS by filtering and the nitration thereof according to an ascending current system by a method wherein a biological filter bed for denitrification is formed from a granular filter material having a large particle size and operated, according to the ascending current system, to simultaneously carry out the removal of SS in sewage by filtering and the denitrification thereof, and a biological filter bed is formed from a filter material whose particle size smaller than that of the filter material of the biological filter bed for denitrification. CONSTITUTION:A biological membrane of denitrifying bacteria is developed on the surface of a filter bed A and sewage 1 and a nitrated liquid 2 are supplied to the filter bed A formed from a filter material having a rather large particle size as an ascending current to advance the reduction of NOX-N and the removal of SS by filtering. Nitrating bacteria is bonded and developed on the surface of the granular filter material of a filter bed B and NH3-N in outflow water 5 is nitrated and the 3 residual SS component is bonded to and caught by the biological membrane to be filtered and removed. The residual part of the nitrated liquid 6 is supplied to a granular filter material bed C to remove a very small amount of the SS contained in the nitrated liquid 6. The filter bed B is operated according to an ascending current system to simultaneously carry out the filtration of SS and the nitration of NH3-N and the filtering continuation time of the filter bed B can marked be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for biological nitrification and denitrification of organic wastewater containing nitrogen components such as sewage and human waste.

[Conventional technology]

Conventionally, biological treatment of wastewater has been carried out by applying means such as suspended microbial treatment and biofilm treatment anaerobically, aerobically, or a combination of both.

In particular, wastewater treatment using a combination of an anaerobic filter bed and an aerobic filter bed can be achieved by using the process of anaerobic treatment - aerobic treatment → aerobic filter bed, for example. This method has the advantage of being able to reduce the amount of sludge generated compared to single-bed treatment, and also has the advantage of being able to perform multifaceted treatments, so its range of applications is extremely wide.

For example, the applicant first treated organic wastewater containing B[)D and SS in an anaerobic submerged biological filter bed in an upward flow, and then transferred this treated water in an aerobic submerged biological filter bed in a downward flow. We proposed a method that saves energy and requires a simple process.

In addition, in order to improve the maintenance and manageability of the treatment method including denitrification treatment and the scale of the treatment facility, the applicant has developed a system in which organic wastewater and nitrified liquid are passed through a filter bed filled with a strip of biological contact material. Supplied in countercurrent flow, BOD and NO.

After removing NH3-N, the effluent from the filter bed is fed in a downward flow to an aerobic biological soaked filter bed to nitrify NH3-N and to
We proposed a method to filter out the This method has the great advantage of not requiring an aeration tank or sedimentation tank.

[Invention or problem to be solved]

However, as a result of a detailed re-examination of this prior art by the present inventor, the following problems were discovered, and it became clear that it was not an ideal method.

That is, (1) In the nitrification and SS removal section using a downward flow aerobic biological filter bed, the filter bed becomes clogged quickly and must be cleaned frequently.

(2) The processing speed is low, and the residence time required to sufficiently nitrify and denitrify sewage water is approximately 9 hours, even under favorable conditions of a high water temperature of 21 to 28°C. Therefore, the equipment footprint and construction costs are large.

■ Because a strip-shaped (string-shaped) biological contact material is used as a filter bed for denitrification, scum forms on the water surface in the denitrification section. It also releases bad smells. A foul odor is also emitted from the water surface of the nitrification unit.

The present invention aims to completely solve the above-mentioned drawbacks of the conventional state-of-the-art technology, and specifically, (a) significantly reduces the progress of clogging of the biological filter bed and significantly reduces the frequency of filter bed cleaning; let

(b) The nitrification and denitrification rate is significantly increased by 8 to 9 times.

This effect dramatically reduces the equipment installation area and construction costs.

(C) Preventing the formation of scum on the water surface of the denitrification section and nitrification section and the scattering of bad odors.

This is the problem to be solved.

[Means to solve the problem]

The present invention is described in (1) to (3) below, and can thereby solve the above problems.

(1) Organic wastewater containing SS and ammonia was supplied in an upward flow together with a nitrification solution to an anaerobic submerged biological filter bed A filled with granular filter media (average particle size d1), and SS filtration and denitrification proceeded. After that, the effluent from the filter bed A is supplied in an upward flow to the aerobic submerged biological filter bed B filled with granular filter media (average particle size dz) to proceed with SS filtration and nitrification. A part of the effluent water is supplied to the lower part of the filter bed A, and tL>6
A method for biological nitrification and denitrification of organic wastewater, characterized by selecting a granular filter medium that satisfies the conditions of 2.

(2) The biological nitrification and denitrification method for organic wastewater as described in (11) above, characterized in that the remainder of the outflow water from the filter bed B is supplied to a granular filter medium filtration layer.

(3) Anaerobic immersed biological filter bed A filled with granular filter media (average particle size d1) and fed with organic wastewater and nitrification solution containing SS and ammonia in an upward flow to proceed with SS filtration and denitrification. and an aerobic immersed biological filter bed B filled with granular filter media (average particle size d2) and supplied with effluent water from the filter bed A in an upward flow to proceed with SS filtration and nitrification. A biological nitrification and denitrification device for sewage, which is provided with a means for supplying part of the effluent from the filter bed B to the lower part of the filter bed A, and comprises a granular filter medium that satisfies the condition d+>d2. Biological nitrification and denitrification equipment for organic wastewater, characterized by:

The present invention is a method for treating organic wastewater that combines an anaerobic submerged biological filter bed A (hereinafter simply referred to as filter bed A) and an aerobic submerged biological filter bed B (hereinafter simply referred to as filter bed B). and a processing device, the characteristics of which are that the granular filter medium filled in filter bed A has a larger particle size than the granular filter medium filled in filter bed B; N0x-N
The denitrification reaction of NH3-N to N2 and the filtration removal of SS are carried out in an upward flow, and the treated water is passed through filter bed B, where the nitrification reaction of NH3-N to N0x-N and the removal of SS are carried out in an upward flow. Part of the water is supplied and circulated to the filter bed A, and in particular, the particle size of the granular filter medium is limited to the filter bed A and filter bed B, and the water flow direction to the filter beds A and B. By limiting the flow to an upward flow, the water flow residence time and washing frequency of filter beds A and B are significantly reduced, treatment efficiency is improved, and bad odors are completely prevented.

The organic wastewater treated in the present invention has at least S
Contains S and NH3-N, but also BOD, COD
, chromaticity, etc. may be contained.

As the granular filter media for filter beds A and B, various known inorganic and organic materials can be used.
Average particle size ranges from 2 to 20 mm, preferably from 4 to 8 mm
selected from a range of m.

The average particle size of the granular filter media of filter bed B is selected from the range 2 to 8 mm, preferably from 2 to 4 mm. It is important to make the filter medium particle size (l) of filter bed A larger than the filter medium particle size (d2) of filter bed B, and if d<d2, the S in the raw water
S is trapped and removed at the bottom of the filter bed A, and the process cannot be continued unless the filter bed A is clogged or vigorously and frequently washed (this results in poor practicality).

The filtration speed of filter bed A when passing the total flow rate of sewage and nitrification liquid is 100 to 300 m/min when treating normal sewage.
hr range, preferably from 150 to 250 mm/hr. The filtration rate of filter bed B is 70 to 30
0m/hr range, preferably 15C) to 250
mm/hr, and is set to a desired value by considering the raw water quality, the particle size of the granular filter medium, and the filling rate of the granular filter medium.

In the present invention, the nitrifying liquid introduced into the filter bed A along with the organic wastewater may be composed only of the effluent treated in the filter bed B, or may be introduced from a separate process. Furthermore, when introducing the nitrification liquid into the filter bed A, BOD-enriched sewage liquid, alcohol, acetic acid, etc. may be separately mixed in to supplement BOD used for No, -N generation.

Also, the removal rate of SS in filter bed A is adjusted to a range of 50 to 90%, preferably 80 to 85% to ensure sufficient filtration rate and reduced cleaning frequency of filter bed A and filter bed B. It is good.

The treated water treated in the anaerobic filter bed A, that is, the effluent, is
In addition to nitrifying bacteria, the filter bed B may be introduced in an upward flow into the filter bed B.
BOD oxidizing bacteria etc. may be retained.

The nitrified liquid obtained by nitrifying NH3-N in the effluent water to NO, -N through the filter bed B is introduced into the filter bed A in an amount of 100 to 500%, preferably 200 to 400%, of the raw water inflow and circulated. good.

In the present invention, a part of the nitrified liquid, that is, the effluent water that has been subjected to the upward flow treatment in the filter bed B, is circulated to the filter bed A as described above, and the remainder can be discharged if it satisfies predetermined standards. The water quality may be improved by passing the effluent water through a granular filter layer different from the filter beds A and B.

It is preferable that the average particle size of the granular filter media in the granular filter media filtration layer is smaller than that of the filter bed B.

[Effect]

The structure and operation of the present invention will be explained in detail with reference to FIG.

In a preferred embodiment of the invention, the invention is comprised of three main parts.

That is, it consists of the main parts of the denitrification part of the filter bed A, the nitrification part of the filter bed B, and the filtration part of the granular filter layer C.

Filter beds A and B are constructed as fixed fixed beds filled with granular solids selected from anthracite, granular activated carbon, various granular minerals, plastic particles, lightweight granular aggregates, and the like.

Similar to the filter bed B, the granular filter media filtration layer C can also be operated as an aerobic biological filter bed by providing an aeration member.

Thus, organic wastewater 1 containing nitrogen components, such as sewage, is supplied together with nitrified liquid 2 to the lower part of the filter bed A having a large filter medium particle size.

When SS is contained in the wastewater 1 at a high concentration, it is preferable to provide the SS settling section at the bottom of the filter bed A.

It is also possible to inject flocculant 3 into wastewater 1 to perform coagulation and sedimentation treatment.In this case, is it necessary to provide a sedimentation section?As shown in the figure, it is necessary to provide a sedimentation section integrally at the bottom of filter bed A. It can also happen. Further, even when the flocculant 3 is not injected, the settling section can be provided.

Now, a biofilm of denitrifying bacteria has developed on the surface of the particle-sized filter media that constitutes the filter bed A, and the N0x contained in the nitrifying solution 2 has developed.
-N or BOD components in the wastewater 1 are used as hydrogen donors to be reduced to N2 gas by denitrifying bacteria and denitrified at high speed. At the same time, fine SS and colloids in the waste water are also filtered out.

Here, the waste water 1 and the nitrified liquid 2 are filtered onto a filter bed A with a larger particle size.
is supplied in an upward flow instead of a downward flow, reducing NO, -N and S
The first point of the present invention is to advance the filtration removal of S.

If wastewater 1 and nitrification liquid are supplied to filter bed A in a downward flow,
Severe clogging occurred in the upper surface layer of filter bed A.
This poses a major drawback in that it requires frequent cleaning.

On the other hand, in the case of upward flow, it was observed that SS was trapped over the entire height of the filter bed A, and it was found that the progress of clogging of the filter bed A was slowed down. Furthermore, no scum formation or foul odor was observed on the water surface.

In addition, if a band-like or string-like filter material as in the prior art described above is used as the biofouling filter material in the denitrification filter bed A, the denitrification rate will decrease, the filtration effect of SS will deteriorate, and scum will be formed on the water surface and bad odor will be emitted. It was confirmed that there is a drawback.

In addition, if the BOD concentration in the wastewater 1 is low compared to the nitrogen component concentration, it is preferable to inject an organic carbon source 4 such as methanol, ethanol, or acetic acid.

Thus, the denitrified effluent 5 from the upper part of the filter bed A is passed through the filter bed B in an upward flow together with oxygen-containing bubbles 9,
Nitrification of NH and -N and removal of residual SS are performed.

Nitrifying bacteria have grown attached to the surface of the granular filter media of filter bed B, and the NH3-N in the effluent water 5 is nitrified at a high speed, and the residual SS components are removed by filtration by adhesion to the biofilm and capture. . Here, it is important to make the particle size of the granular filter medium of filter bed B smaller than that of filter bed A. A part of the nitrified liquid 6 flowing out from the upper part of the filter bed B is recycled to the lower part of the filter bed A by the circulation pump 7.

On the other hand, the remainder of the nitrification liquid 6 (flow rate is equal to the inflow amount of the wastewater 1) 8 is filtered into a granular filter medium filtration layer C (hereinafter abbreviated as filtration layer C).

), it doesn't matter whether it's an upward flow or a downward flow)
, a trace amount of SS contained in the nitrifying solution 8 is removed by polishing. In addition, by performing the filtration process while supplying oxygen-containing bubbles 10 from the lower part of the filtration layer C, a biofilm can be developed on the surface of the filter medium of the filtration layer C, and a trace amount of BOD remaining in the nitrification liquid 8 can be reduced. , is preferable because NH3-N can be removed biologically.

11 is treated water, and BOD, SS, and nitrogen are also number ■
/β.

An important point of the present invention is that the filter bed B is operated in an upward flow to simultaneously perform SS filtration and NH3-N nitrification, and this allows the filtration duration of the filter bed B to be significantly extended.

That is, it is possible to continue filtration approximately three times as long as when filter bed B is operated in a downward flow. However, in the upward flow method, water rises in parallel with the oxygen-containing bubbles, so the filter medium may become agitated when the bubbles rise, and it was found that the filtration effect of SS was slightly inferior to that of the downward flow method. .

Therefore, it may be difficult to keep the SS in the nitrifying solution 8 below 10 .mu./l at all times. Providing a filter layer C is extremely effective as a countermeasure to this situation.

That is, by configuring the nitrification section with the upflow submerged filter bed B and the downflow or upflow filtration layer C in series, "filter bed A
It is possible to obtain the important effect of "satisfying the two conflicting conditions of slowing down the progress of clogging of , B, reducing the frequency of cleaning, and always keeping the SS of treated water below 10 ■/l". can.

Of course, the water quality regulations for discharged water are not very strict, and 5S20
In the case where the amount is less than 1/l, the filtration layer C may be omitted, or the filtration layer C plays a major role if a high degree of SS removal is to be achieved.

Moreover, if the NH3-N concentration in wastewater increases rapidly,
Is it possible that NH3-N cannot be completely nitrified in the filter bed B? Even in this situation, the filter bed C can function as a nitrification section by supplying oxygen-containing gas from the bottom of the filter bed C. Therefore, it is possible to prevent discharged water containing residual NH3-N from being discharged into public waters.

That is, the filtration layer C functions as a safety valve. The optimal filter material for the filter layer C is granular activated carbon, which also has the function of removing COD and chromaticity.

Note that 12a and 12b in FIG. 1 are water supply lines for cleaning the filter bed B and filtration layer C, and 13a, 13b, and 13c are outflow pipes for cleaning waste water.

To wash the filter bed A, it is sufficient to increase the flow rate of the waste water 1 to fluidize the filter bed A, and no special washing water is required. 1
4 is air used when cleaning the filter bed A, which cleans the inside of the filter bed A with air.

15 is a drainage pipe for settled sludge.

The gist of the technical idea of the present invention explained above can be summarized as follows:
The biological filter bed on the denitrification side is a granular filter medium with a large particle size, and is operated in an upward flow to simultaneously perform filtration removal of SS in wastewater and denitrification. Furthermore, by making the particle size of the biological filter bed for nitrification smaller than that of the filter medium of the biological filter bed on the denitrification side and performing the upward flow, the filtration removal of residual SS and nitrification can be simultaneously performed. This idea is in contrast to the conventional technology.

As a result, it has become possible to obtain the following important effects, and it has been confirmed that the drawbacks of the prior art can be completely solved.

〔Effect of the invention〕

■ The denitrification rate and nitrification rate are proportional to the concentration of denitrification and the concentration of nitrifying bacteria in the filter bed. Even at low filtration speeds of 18 to 20 m/day, the filter bed had to be cleaned more than once a day due to the rapid clogging. In other words, filter bed cleaning is an operation to forcibly wash out the microorganisms in the filter bed, so the frequency of cleaning the filter bed and the concentration of organisms maintained in the filter bed are inversely proportional. . That is, denitrification and nitrification rates are improved by washing the filter bed less frequently.

The present invention significantly reduces the frequency of filter bed cleaning compared to the prior art, and as a result, high-speed denitrification and nitrification reactions can be achieved, and the apparatus can be made significantly more compact.

(2) Since the denitrification section is made of a filter bed immersed in granular filter media that is highly effective in capturing SS, there is no scum generated at the water surface. No foul odor was observed.

■ Even though it flows out from the water surface of the nitrification unit like clarified treated water or a spring, it has an overwhelmingly superior aesthetic appearance compared to conventional technology, and the bad odor is biologically deodorized, so there is no bad odor coming from the water surface.

■ The progress of clogging of the filter bed is very slow, and the advanced removal effect of SS is slightly inferior.The filtration layer C is installed following the upflow nitrification filter bed, so that the clarified treated water always has an SS number of ■/β. Can you get it?

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

Experiments of the present invention were conducted based on the flow sheet shown in FIG. 1 using groundwater of Fujisawa City, Kanagawa Prefecture as raw water.

The experimental conditions are shown in Table-1.

It was possible to carry out filtration for an extremely long time.

As a result of this experiment, the processing speed was improved by approximately 9 times (residence time 1/9) compared to the conventional technology described above, and the amount of water that could be passed through one cycle (the amount of raw water that could be passed from one wash to the next) was improved. The flow rate (meaning the flow rate) increased approximately three times, and we were able to achieve a dramatic technological improvement.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a flow sheet for explaining one embodiment of the apparatus and method of the present invention. Explanation of symbols 1: Sewage 2: Nitrification liquid 3: Coagulant 4. Organic carbon source 5, runoff water
6: Nitrification liquid -07: Circulation pump 8:
Remaining part of nitrifying solution 9.1 Exhaled oxygen-containing bubbles 11: Treated water 1
2a, 12b: Cleaning water supply lines 13a, 13
b, 13c: Outflow pipe raw water processing amount of washing wastewater is 3rn'
/d, and conducted three continuous experiments. One month after the start of the experiment, enough denitrifying and nitrifying bacteria had adhered to the filter media, so from the second month onwards, composite samples were subjected to water quality analysis once a day. Table 2 shows the average values of water quality analysis. In addition, filtration duration (time elapsed until filter resistance reaches 5), filter bed A 38 hr filter bed B 26 hr filtration bed C 72 hr QQmmJ (to 20

Claims (3)

[Claims] (1) Organic wastewater containing SS and ammonia is filtered using granular filter media (
The nitrification liquid is supplied in an upward flow to an anaerobic submerged biological filter bed A filled with granular filter media (average particle diameter d_1) to proceed with SS filtration and denitrification. The water is supplied in an upward flow to an aerobic submerged biological filter bed B filled with particle size d_2) to proceed with SS filtration and nitrification, and a portion of the effluent water from the filter bed B is supplied to the lower part of the filter bed A. and d_1>
A method for biological nitrification and denitrification of organic wastewater, characterized by selecting a granular filter medium that satisfies the condition of d_2. (2) The biological nitrification and denitrification method for organic wastewater according to claim 1, characterized in that the remainder of the effluent from the filter bed B is supplied to a granular filter medium filtration layer. (3) Anaerobic submerged biological filter bed filled with granular filter media (average particle size d_1), and organic wastewater containing SS and ammonia and nitrification liquid are supplied in an upward flow to advance SS filtration and denitrification. A, and an aerobic submerged biological filter bed B filled with granular filter media (average particle size d_2), to which the effluent water from the filter bed A is supplied in an upward flow to proceed with SS filtration and nitrification. A granular filter medium which is a biological nitrification and denitrification device for industrial wastewater, which is provided with means for supplying a portion of the effluent from the filter bed B to the lower part of the filter bed A, and which satisfies the condition d_1>d_2. A biological nitrification and denitrification device for organic wastewater, characterized by selecting.