JP4017657B1 - Treatment method of wastewater containing organic matter - Google Patents

Abstract

An organic matter-containing wastewater treatment method is provided that can effectively treat wastewater containing organic matter and does not require removal of sludge, resulting in sufficient volume reduction of excess sludge.
SOLUTION: A method for treating organic matter-containing wastewater is a flow rate adjustment step 1 in which wastewater containing organic matter is maintained in an aerobic atmosphere in which the dissolved oxygen amount exceeds 1.0 mg / l and the flow rate of the wastewater is adjusted. The microaerobic microorganism treatment steps 2 and 3 for treating microorganisms in a microaerobic atmosphere with 0.1 to 1.0 mg / l, and then the waste water from the microaerobic microorganism treatment step is treated with sludge and supernatant under anaerobic atmosphere. Sludge sedimentation step 4 for sedimentation and separation into sludge, sludge concentration step 5 for concentration and sedimentation of the obtained sludge in an anaerobic atmosphere, and sludge treated in the sludge concentration step with a dissolved oxygen content of 0.1 to 1.0 mg / l Microaerobic sludge digestion process 6 for further digestion in aerobic atmosphere, recovering the supernatant liquid obtained in the microaerobic sludge digestion process and storing it in a microaerobic atmosphere with a dissolved oxygen content of 0.1 to 1.0 mg / l The sludge obtained in the sludge precipitation step 4 Mud is returned to the microaerobic maintenance biological treatment process 2, the supernatant liquid from the sludge concentration process 5 is returned to the flow rate adjustment process 1, and the supernatant liquid storage process 7 to the flow rate adjustment process 1 and / or the microaerobic microorganism treatment process 2 Return the supernatant to.
[Selection] Figure 1

Description

  The present invention relates to a method for treating organic matter-containing wastewater, and more specifically, can treat organic matter-containing wastewater effectively, and can sufficiently reduce the volume of excess sludge to be treated as a result without requiring removal of sludge. The present invention relates to a method for treating organic wastewater.

  Conventionally, the activated sludge method has been mainly used for the treatment of wastewater containing organic matter. In the activated sludge method, aerobic bacteria that breathe oxygen are mainly used, and a method of decomposing and purifying the influent sewage is adopted. However, since aerobic bacteria that breathe oxygen have a high growth rate and increase more than necessary in the treatment tank, it is necessary to work to extract these increased bacteria and surplus sludge such as dead bodies and excrement of bacteria. This excess sludge is said to occupy about half of industrial waste. Since there is less room for landfill at the final disposal site, measures to reduce the volume are urgently needed. In addition, due to the enforcement of the Food Recycling Law, there is an urgent need to reduce waste generation and reduce volume in food related businesses.

Therefore, various wastewater treatment methods that treat excess sludge or do not discharge excess sludge have been proposed.
For example, Patent Document 1 describes a wastewater treatment apparatus that performs wastewater treatment by microaerobic aeration treatment.

Patent Document 2 proposes an aeration treatment method having characteristics of both an activated sludge method and a biofilm method.
In Patent Document 3, the aeration treatment and sludge precipitation of the sewage are effectively performed simultaneously in the aeration treatment tank, and the generation of scum is suppressed as much as possible, so that the generated scum can be naturally separated from the purified water. A sewage treatment apparatus is proposed.

  In Patent Document 4, the sludge accumulated at the bottom of the settling tank is sucked up so that a certain amount of sludge can be returned to the aeration treatment tank, and the remaining sludge is returned to the settling tank without disturbing the liquid level. There has been proposed a sewage treatment apparatus adapted to appropriately agitate the sediment sludge at the bottom.

  Further, in Patent Document 5, microbial electron acceptor adjustment water is mixed into raw waste water, and the amount of dissolved oxygen is aerated under substantially 1 mg / l or less. A treatment apparatus has been proposed for carrying out a treatment method in which the amount of aeration is substantially 1 mg / l or less and the supernatant water is returned to the raw wastewater as electron acceptor adjustment water.

  However, the above-described conventionally proposed treatment methods still have a problem that the excess sludge cannot be sufficiently reduced, or even if the excess sludge is not generated, the organic matter-containing wastewater cannot be treated sufficiently effectively.

  In short, the current situation is that the surplus sludge has not been sufficiently reduced in volume, and there is a demand for the development of a treatment method for organic matter-containing wastewater that can further reduce the excess sludge.

JP 2004-188281 A JP 2004-223320 A JP 2004-223432 A JP 2004-237156 A Japanese Patent No. 3667254

  Accordingly, an object of the present invention is to provide an organic matter-containing wastewater treatment method that can effectively treat organic matter-containing wastewater and can sufficiently reduce the volume of excess sludge without requiring sludge extraction treatment.

  As a result of intensive studies to solve the above problems, the present inventors combined microbial treatment in an aerobic atmosphere of organic matter-containing wastewater with microbial treatment in a microaerobic atmosphere, and treated in an anaerobic atmosphere. It was found that the above-mentioned purpose can be achieved by allowing the subsequent drainage to settle and separate into sludge and supernatant, and the present invention has been completed.

  That is, the present invention is a flow rate adjustment step of adjusting the flow rate of the waste water by maintaining the organic matter-containing waste water in an aerobic atmosphere in which the dissolved oxygen amount exceeds 1.0 mg / l, and the waste water has a dissolved oxygen amount of 0.1 to 1.0 mg. / l, preferably 0.5 to 0.8 mg / l of microaerobic microorganism treatment step for treating microorganisms in a microaerobic atmosphere, and then the waste water from the microaerobic microorganism treatment step is treated with sludge and supernatant under anaerobic atmosphere The sludge sedimentation step for sedimentation and separation into sludge, the sludge concentration step for concentration and sedimentation of the obtained sludge in an anaerobic atmosphere, the amount of dissolved oxygen in the sludge concentrated in the sludge concentration step is 0.1 to 1.0 mg / l, preferably 0.5 to The supernatant obtained from the microaerobic sludge digestion process and the microaerobic sludge digestion process, which are further digested in a microaerobic atmosphere of 0.8 mg / l, is recovered and the dissolved oxygen amount is preferably 0.1 to 1.0 mg / l, preferably Is a supernatant storage process for storing in a microaerobic atmosphere of 0.5 to 0.8 mg / l The sludge obtained in the sludge precipitation process is returned to the microaerobic microorganism treatment process to activate the microaerobic microorganisms, and the supernatant liquid obtained in the sludge concentration process is returned to the flow rate adjustment process. It is the processing method of the organic matter containing waste_water | drain which carries out quantitative injection | pouring of a supernatant liquid from a storage process to a flow volume adjustment process and / or a microaerobic microorganism processing process.

  In this treatment method, the microaerobic microorganism treatment step includes a first microaerobic microorganism treatment step in which the wastewater from the flow rate adjustment step is subjected to microorganism treatment in a microaerobic atmosphere having a dissolved oxygen amount of 0.1 to 1.0 mg / l. , A second microaerobic microorganism treatment step in which the wastewater from the first microaerobic microorganism treatment step is subjected to a microorganism treatment in a microaerobic atmosphere having a dissolved oxygen amount of 0.1 to 1.0 mg / l to advance decomposition of organic matter. Are preferably included.

  According to the treatment method of the present invention, since organic matter-containing wastewater is treated in a microaerobic atmosphere, the growth rate is slow, and the growth of microorganisms mainly consisting of nitrate respiration that decomposes organic matter with the minimum necessary cell synthesis is possible. On the contrary, the growth of aerobic microorganisms (microorganisms mainly oxygen respiration) that generate excess sludge is suppressed. Therefore, the organic matter-containing wastewater can be effectively treated, and the excess sludge can be sufficiently reduced without requiring the sludge extraction treatment, and the organic matter-containing wastewater can be continuously treated without maintenance.

Hereinafter, the present invention will be described in more detail with reference to the drawings.
Examples of the organic matter-containing wastewater that can be treated in the present invention include manure wastewater, livestock manure wastewater, agricultural wastewater, domestic wastewater, and factory wastewater.

FIG. 1 is a schematic diagram showing an outline of the processing method of the present invention.
As shown in FIG. 1, the organic matter-containing wastewater treatment method of the present invention comprises a flow rate adjustment tank 1, a first microaerobic reaction tank 2, a second microaerobic reaction tank 3, a precipitation tank 4, a sludge concentration tank 5, Microaerobic sludge digestion tank 6, supernatant liquid storage tank 7, circulation pipe (digestion supernatant return pipe) 8 from the supernatant liquid storage tank 7 to the flow rate adjustment tank 1, and the first microaerobic reaction from the supernatant liquid storage tank 7 It can be carried out by a system including a circulation pipe (digested supernatant liquid return pipe) 9 leading to the tank 2 and a circulation pipe (concentrated sludge return pipe) 10 extending from the sludge concentration tank 5 to the flow rate adjustment tank 1. In the present embodiment, the micro-aerobic reaction tank has a two-tank structure of the first and second micro-aerobic reaction tanks. However, the two-tank structure is not necessarily required.

  In the flow rate adjustment tank 1, an organic matter-containing wastewater (hereinafter also referred to as “raw water”) is maintained in an aerobic atmosphere in which the dissolved oxygen amount exceeds 1.0 mg / l, and a flow rate adjustment step of adjusting the flow rate of the wastewater is performed. In the 1st microaerobic reaction tank 2, the 1st microaerobic microorganisms process process which processes the said waste_water | drain in the microaerobic atmosphere whose dissolved oxygen amount is 0.1-1.0 mg / l is performed. In the second microaerobic reaction tank 3, the wastewater from the first microaerobic microorganism treatment step is treated in a microaerobic atmosphere of 0.1 to 1.0 mg / l to promote decomposition of organic matter. The aerobic microorganism treatment process is performed. Next, in the sedimentation tank 4, a sludge precipitation step is performed in which the waste water from the second microaerobic microorganism treatment step is settled and separated into sludge and a supernatant in an anaerobic atmosphere. The process so far is continuously performed according to the natural flow of raw water supplied to the system. The supernatant obtained in the settling tank 4 may be discharged into a general basin as long as the drainage standard is satisfied. On the other hand, the sludge obtained in the sedimentation tank 4 is usually returned to the first microaerobic microorganism treatment step and again used for microbial activation, but the sludge concentration tank 5 is once or twice a day. And is subjected to a sludge concentration step for concentration and sedimentation in an anaerobic atmosphere. Subsequently, in the microaerobic sludge digestion tank 6, a microaerobic sludge digestion process is performed in which the sludge treated in the sludge concentration process is further digested in a microaerobic atmosphere having a dissolved oxygen content of 0.1 to 1.0 mg / l. In the microaerobic sludge digestion step, the residence time is preferably about 12 to 24 hours. Next, the supernatant liquid storage tank 7 collects the digestive supernatant liquid obtained in the microaerobic sludge digestion step and stores it in a microaerobic atmosphere with a dissolved oxygen amount of 0.1 to 1.0 mg / l. Perform the process. In this supernatant liquid storage step, it is preferable to promote the propagation of microorganisms for digestion and reduction by setting the residence time to about 12 to 24 hours.

  The sludge obtained in the sludge precipitation step is returned to the microaerobic microorganism treatment step to activate the microaerobic microorganisms. The supernatant liquid obtained in the sludge concentration step is returned to the flow rate adjustment step and again used in the wastewater treatment step. The digestive supernatant is quantitatively injected from the supernatant liquid storage process into the flow rate adjustment process and / or the microaerobic microorganism treatment process.

Hereinafter, each process will be described in more detail.
1) Flow rate adjustment step The flow rate adjustment step adjusts the flow rate of the waste water containing the organic matter-containing waste water in an aerobic atmosphere in which the dissolved oxygen amount exceeds 1.0 mg / l, preferably more than 1.0 to 2.0 mg / l. It is a process to do. Wastewater containing organic matter is constantly changing and unstable, such as water quality, dissolved oxygen, and inflow. In the following first and second microaerobic treatment steps, the dissolved oxygen content of the organic matter-containing wastewater is stabilized and discharged in the range of 1.0 to 2.0 mg / l in the flow rate adjustment step in order to quickly grow and activate microorganisms. It is preferable to adjust the dissolved oxygen amount to 1.0 mg / l or less in the first microaerobic reaction tank.

  In this embodiment, the dissolved oxygen amount is adjusted by sending air from the aeration pipe 1a provided in the flow rate adjusting tank 1 as shown in FIG. Here, the liquid in the flow rate adjusting tank 1 is also circulated by the flow of air supplied from the aeration pipe 1a.

  As shown in FIG. 1, the flow rate of the organic matter-containing wastewater present in the flow rate adjustment tank 1 and the supernatant liquid returned to the flow rate adjustment tank 1 from the sludge concentration tank 5 and the supernatant liquid storage tank 7 described later are the flow rate adjustment tank 1. To 1st slightly aerobic reaction tank 2 so that it will flow out to 1/24 to 1.5 times or less of daily average drainage per hour. The capacity of the treatment tank after the first microaerobic reaction tank is basically designed with the planned pollution load so that the daily influent wastewater is treated within 16 to 24 hours. This is not preferable because the residence time required for each treatment cannot be secured. In general, the supernatant liquid returned to the flow rate adjusting tank 1 is preferably set to be about 0.3 to about 1.0 vol% of the entire treated water amount.

2) First microaerobic microbial treatment step The first microaerobic microbial treatment step is a microaerobic atmosphere in which the wastewater has a dissolved oxygen content of 0.1 to 1.0 mg / l, preferably 0.5 to 0.8 mg / l. It is a process of microbial treatment.

  In this step, deodorizing microorganisms (such as chemically synthesized bacteria and Metofile bacteria) that consume nitrates and phosphates dominate. Chemosynthetic bacteria produce nitric acid, and Metofil bacteria produce sulfide. When sulfide increases in the liquid to be treated, sulfur-reducing microorganisms (including archaea) that consume sulfide as an electron acceptor grow.

  If the amount of dissolved oxygen is less than 0.1 mg / l, the growth of deodorant microorganisms (chemically synthesized bacteria, Metofile bacteria, etc.) will decrease significantly, and if it exceeds 1.0 mg / l, aerobic microorganisms will proliferate and activate. Prevents the generation of microorganisms that grow and activate in a microaerobic atmosphere. In addition, since aerobic microorganisms have a strong growth potential, the generation of sludge increases.

  The treatment in this step is preferably performed at ambient temperature, preferably 20 ° C to 30 ° C. Moreover, it is preferable to design the residence time which is processing time in the range of 4 to 12 hours by the load of organic matter containing waste_water | drain. In the present embodiment, since the same amount of liquid to be processed flows out to the second slightly aerobic reaction tank 3 as a result of continuous processing and flowing from the flow rate adjustment tank 1, the liquid to be processed is not easily short-circuited. . Generally, the amount of water flowing from the flow rate adjusting tank 1 to the first slightly aerobic reaction tank 2 is preferably set to be 1/24 to 1.5 of the daily average drainage amount per hour of the entire treated water amount.

  Also in the 1st microaerobic reaction tank 2, adjustment of the amount of dissolved oxygen is adjusted by sending in air from the aeration pipe 2a provided in the 1st microaerobic reaction tank 2, as shown in FIG. Here, the liquid in the first microaerobic reaction tank 2 is also circulated by the flow of air supplied from the aeration pipe 2a.

3) Second microaerobic microorganism treatment step The second microaerobic microorganism treatment step is a waste water from the first microaerobic microorganism treatment step of 0.1 to 1.0 mg / l, preferably 0.5 to 0.8 mg / l. This is a step of proceeding decomposition of organic matter by treatment in a microaerobic atmosphere.

In this process, fermentable microorganisms (yeast, bacillus, alkaligenes, Clostridium, Pseudomonas, lactic acid bacteria, etc.) that consume organic substances contained in the liquid to be treated prevail, and denitrification (N ₂ gas generation and release) proceeds. Then, decomposition of organic matter (production of H ₂ , CO _2, etc.) proceeds by a fermentation reaction using the organic matter as an electron donor. H ₂ generated by the decomposition of organic matter is decomposed by sulfur-reducing microorganisms that use sulfur compounds as electron acceptors, so that active growth of fermentable microorganisms is promoted. Odorous substances generated by the decomposition of organic substances (methyl sulfide: no methane generation due to the absence of methane odor) are consumed by deodorizing microorganisms (chemically synthesized bacteria, Metofile bacteria, etc.).

  If the amount of dissolved oxygen is less than 0.1 mg / l, the growth of fermentable microorganisms (yeast, bacillus, alkaligenes, Clostridium, Pseudomonas, lactic acid bacteria, etc.) is significantly reduced, and conversely if it exceeds 1.0 mg / l, aerobic microorganisms It proliferates and inhibits the activity of microorganisms that proliferate and activate in a microaerobic atmosphere. In addition, since aerobic microorganisms have a strong growth potential, the generation of sludge increases.

  The treatment in this step can be performed at ambient temperature, preferably 20 ° C to 30 ° C. Moreover, it is preferable to design the residence time which is processing time in the range of 4 to 12 hours by the load of organic matter containing waste_water | drain. In this embodiment, since it processes continuously and inflow from the 1st microaerobic reaction tank 2 will flow out to the sedimentation tank 3, it is set as the structure where a to-be-processed liquid is hard to short-circuit.

  The second slightly aerobic reaction tank 3 is also provided with an aeration pipe 3a for supplying air, adjusting the amount of dissolved oxygen and circulating the liquid to be treated.

4) Sludge precipitation step The sludge precipitation step is a step of allowing the waste water from the second microaerobic microorganism treatment step to settle and separate into sludge and supernatant liquid in an anaerobic atmosphere.

  In the sludge precipitation process, the growth of fermentable microorganisms is stopped by maintaining in an anaerobic atmosphere, and considered as anaerobic microorganisms (facultative anaerobic bacteria, sulfur-reducing bacteria) and phosphorus-absorbing microorganisms (polyphosphate accumulating bacteria, etc.) ) Grow and digest sludge to produce methane, nitrates, sulfur compounds, phosphates, etc.

  The sedimentation separation is preferably performed by leaving the stored liquid to be treated for a certain period of time, preferably 3 to 4 hours, at ambient temperature, preferably 20 ° C to 30 ° C. The sedimentation tank 4 is provided with a supernatant discharge pipe 4a for discharging the processed supernatant to the general watershed. In addition, in order to allow the sludge to settle naturally, a hopper 4b is provided at the bottom of the settling tank 4, and the settling sludge is always returned to the first microaerobic reaction tank 2 in an amount 1 to 2 times the daily average amount of drainage to concentrate the sludge. The tank 5 has a structure that can be distributed and adjusted. In addition, a separation level line (indicated by a dotted line in the figure) is set in the height direction of the liquid to be treated stored in the settling tank 4, and the liquid to be treated existing above the separation level line is a supernatant liquid. The inflow of the liquid to be treated from the second slightly aerobic reaction tank 3 may be performed below the separation level line. The inflow rate from the second slightly aerobic reaction tank is preferably 2 to 3/24 of the daily average drainage amount per hour.

5) Sludge concentration process The sludge concentration process is a process in which the sludge obtained in the sludge precipitation process is further concentrated and settled in an anaerobic atmosphere to separate into supernatant water and sludge.

  In the sludge concentration process, the precipitation sludge purified in the sludge precipitation process is further maintained in an anaerobic atmosphere to suppress the growth of fermentable microorganisms and the growth of digestive microorganisms (methane-producing bacteria, sulfur-reducing bacteria, etc.) The digestion of sludge further proceeds, and the excess sludge is reduced.

  In the present embodiment, the sludge is extracted from the lower end of the sedimentation tank 4 at a rate of about once every 12 to 24 hours, put into the sludge concentration tank 5 and stored in an arbitrary predetermined amount, and then the ambient temperature, preferably 20 ° C to It is preferred to concentrate at a temperature of 30 ° C. with a residence time of about 12-24 hours.

  The sludge concentration tank 5 is provided with a circulation pipe 10 for returning the separated supernatant liquid to the flow rate adjustment tank 1. Further, a hopper 5b is provided at the lower part of the sludge concentration tank 5 in order to allow the sludge to settle naturally.

  Although the concentration treatment of this embodiment is performed continuously, the sludge concentration step requires the presence of a predetermined amount of sludge, and it takes time until the predetermined amount of sludge settles in the sludge settling step. Since it takes time until the sludge is digested and reduced to a predetermined amount, the sludge is preferably transferred at a rate of about once every 12 to 24 hours.

6) Microaerobic sludge digestion process The microaerobic sludge digestion process is a microaerobic atmosphere in which the amount of dissolved oxygen in the sludge concentrated in the sludge concentration process is 0.1 to 1.0 mg / l, preferably 0.5 to 0.8 mg / l. It is the process of further digesting below.

  The organic matter in the sludge concentrated in the sludge concentration process is almost digested to become almost inorganic, and fermentable microorganisms are drastically reduced. In the microaerobic sludge digestion process, digestive microorganisms (methane-producing bacteria, sulfur-reducing bacteria, etc.) and deodorizing microorganisms (chemosynthetic bacteria, Metofile bacteria, etc.) coexist and decompose and digest residual organic matter. Thus, a solution (digestion supernatant) rich in inorganic components such as nitrates, sulfur compounds and phosphates is produced.

The amount of dissolved oxygen is maintained at 0.1 to 1.0 mg / l, preferably 0.5 to 0.8 mg / l, and digestive microorganisms and deodorant microorganisms are allowed to grow appropriately, resulting in a reduction in sludge volume.
If the amount of dissolved oxygen exceeds 1.0 mg / l, the activity of digestible microorganisms and deodorant microorganisms decreases.

  In this embodiment, after sludge is extracted from the lower end of the sludge concentration tank 5 and put into the microaerobic sludge digestion tank 6 and stored in an arbitrary predetermined amount, ambient temperature, preferably 20 ° C to 30 ° C, The reaction is preferably carried out with a residence time of 12 to 24 hours.

  Although the treatment method of this embodiment is performed continuously, the presence of a predetermined amount of sludge is required in the microaerobic sludge digestion step, and about once every 12 to 24 hours as in the preceding sludge concentration step. It is preferable to transfer sludge at a ratio of

The aerobic sludge digestion tank 6 is also provided with an aeration pipe 6a for adjusting the amount of dissolved oxygen and circulating the liquid to be treated.
The supernatant liquid rich in inorganic components obtained by the microaerobic sludge digestion process is sent to the next supernatant liquid storage process by natural outflow.

7) Supernatant liquid storage process The supernatant liquid storage process collects the supernatant liquid obtained in the microaerobic sludge digestion process (hereinafter, this supernatant liquid is referred to as “digested supernatant liquid”), and the dissolved oxygen amount is 0.1 to 1.0 mg. / l, preferably a step of storing in a microaerobic atmosphere of 0.5 to 0.8 mg / l. It is also a process of digesting the sludge that remains slightly.

  The digestive supernatant contains a large amount of chemical substances that microorganisms use as an energy source. For example, an inorganic liquid containing a large amount of nitrates, sulfur compounds, phosphates and the like produced microbiologically. Therefore, by returning the digested supernatant to the flow rate adjustment tank 1 or the microaerobic reaction tank 2, the metabolism of microorganisms in the raw water can be promoted, and the microorganisms can be easily maintained in an active state. For this reason, it is preferable to store digestive supernatant liquid, adjusting so that it may become the density | concentration range used as nitric acid 4.0-6.0 mg / L suitable as bait for microorganisms.

  If the amount of dissolved oxygen is less than 0.1 mg / l, the activity of deodorizing microorganisms (chemically synthesized bacteria, Metofir bacteria, etc.) is significantly reduced, and conversely if it exceeds 1.0 mg / l, digestive microorganisms and deodorizing microorganisms Activity decreases.

  In the present embodiment, the supernatant liquid is extracted from the upper end portion of the microaerobic sludge digestion tank 6 by natural outflow and is introduced into the supernatant liquid storage tank 7 and is about 12 at ambient temperature, preferably 20 ° C. to 30 ° C. Store for ~ 24 hours.

  The supernatant liquid storage tank 7 is also provided with an aeration pipe 7a for adjusting the amount of dissolved oxygen and circulating the liquid to be treated.

8) Circulation process In the present invention, the circulation process was obtained by returning the sludge obtained in the sludge precipitation process to the microaerobic microorganism treatment process and activating the microaerobic microorganisms, and the sludge concentration process. There are a step of returning the supernatant liquid to the flow rate adjustment step and a step of quantitatively injecting the supernatant liquid from the supernatant liquid storage step into the flow rate adjustment step and / or the microaerobic microorganism treatment step.

  The sludge from the sludge settling tank 4 is returned to the microaerobic microorganism treatment step (first microaerobic reaction tank 2) through the sludge return pipe 4c. The supernatant liquid from the sludge concentration tank 5 is returned to the flow rate adjustment tank 1 through the supernatant liquid return pipe 10. The digestive supernatant liquid from the supernatant liquid storage tank 7 is returned to the flow rate adjustment tank 1 and the microaerobic microorganism treatment step (first microaerobic reaction tank 2) through the digestive supernatant liquid return pipes 8 and 9, respectively.

  When returning the digestive supernatant to the flow rate adjustment step and / or the microaerobic microorganism treatment step, it is necessary to put it into each tank so that the total amount of wastewater to be treated per day is 0.3 to 1.0 vol%. preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not restrict | limited at all to these.

[Experimental system]
Using the apparatus shown in FIG. 1, the wastewater containing organic matter was treated at a daily throughput of 20 m ³ .

The amount of dissolved oxygen in the flow adjustment tank 1 exceeds 1.0 to 2.0 mg / l, the amount of dissolved oxygen in the first microaerobic reaction tank 2 and the second microaerobic reaction tank 3 is 0.1 to 1.0 mg / l, the precipitation tank 4 and The sludge concentration tank 5 was made anaerobic, and the dissolved oxygen amount in the microaerobic sludge digestion tank 6 was adjusted to 0.1 to 1.0 mg / l, and the dissolved oxygen amount in the supernatant liquid storage tank 7 was adjusted to 0.1 to 1.0 mg / l. The flow rate of raw water into the flow rate adjustment tank 1 was 20 m ³ / day, and the flow rate from the flow rate adjustment tank to the first microaerobic reaction tank 2 was adjusted to 0.9 m ³ / min and continuously supplied. The first microaerobic reaction tank 2 to the second microaerobic reaction tank 3 and the precipitation tank 4 were continuously supplied by overflow. In the sedimentation tank 4, the treated supernatant liquid was turned to the treated water discharge, and the sludge was settled. The sludge settled over about 24 hours was extracted from the bottom of the tank and transferred to the sludge concentration tank 5, and the sludge was further settled over about 24 hours to concentrate the activated sludge. Thereafter, the supernatant liquid of the sludge concentration tank 5 is returned to the flow rate adjustment tank 1 and the first slightly aerobic reaction tank 2, respectively, and the concentrated sludge is extracted from the bottom of the sludge concentration tank 5, and the slightly aerobic sludge digestion tank 6 is removed. The sludge was digested for about 24 hours. The supernatant liquid obtained in the microaerobic sludge digestion tank 6 is transferred to the supernatant liquid storage tank 7, and the microbial metabolism is advanced in a microaerobic atmosphere for about 24 hours to obtain a supernatant liquid rich in inorganic salts. Prepared. The supernatant liquid was transferred to the flow rate adjustment tank 1 and / or the first microaerobic reaction tank 2 to perform the following water treatment.

The wastewater used was organic matter-containing wastewater discharged from school meal facilities.
PH of raw water, microaerobic treated water collected from the second microaerobic reaction tank 3, microaerobic sludge digested water collected from the microaerobic sludge digestion tank 6, and treated water collected from the supernatant of the precipitation tank 4 (JIS K 0102 12.1), BOD (JIS K 0102 21), COD (JIS K 0102 17), SS (Appendix Table No. 59, 1971, Environment Agency), N-Hx (normal hexane extract content: Showa 49, Environmental Agency Notification No. 64, Appendix 4), TN (total nitrogen content: JIS K 0102 54.2), TP (total phosphorus content: JIS K 0102 46.3.1), transparency (measured by the clean measure method), SV ₃₀ (active sludge sedimentation rate 30-minute value), which is the ratio of the sludge height that settles in 30 minutes, MLSS (measured with a transmitted light type MLSS meter) that is an index of activated sludge suspended matter, ORP (redox potential meter) : JIS C 0920) according to the JIS method. The water quality measurement results are shown in Tables 1 and 2.

[Control system 1]
An experiment similar to the experimental system was performed using the same apparatus shown in FIG. However, the amount of dissolved oxygen in the flow adjustment tank 1 exceeds 1.0 to 2.0 mg / l, the amount of dissolved oxygen in the first aerobic reaction tank 2 and the second aerobic reaction tank 3 is 2.55 to 3.20 mg / l, the precipitation tank 4 and The sludge concentration tank 5 was set to anaerobic conditions (0.8 mg / l or less), the dissolved oxygen amount in the sludge digestion tank 6 was adjusted to 0 mg / l, and the dissolved oxygen amount in the supernatant liquid storage tank 7 was adjusted to 0 mg / l. The results are shown in Tables 3-4.

[Control system 2]
An experiment similar to the experimental system was performed using the same apparatus shown in FIG. However, the amount of dissolved oxygen in the flow rate adjustment tank 1 is less than 1.0 mg / l, the amount of dissolved oxygen in the first microaerobic reaction tank 2 and the second microaerobic reaction tank 3 is 0.1 to 1.0 mg / l, and the precipitation tank 4 is Anaerobic conditions, sludge concentration tank 5 with a dissolved oxygen content of less than 1.0 mg / l, aerobic sludge digestion tank 6 with dissolved oxygen content of 0.1-1.0 mg / l, supernatant liquid storage tank 7 The amount of dissolved oxygen was adjusted to 0.1 to 1.0 mg / l. The results are shown in Tables 5-6.

  The water quality measurement results of the experimental system and the control systems 1 and 2 are shown in a graph (FIGS. 2 to 14). From the water quality transition graph shown in FIGS. 2 to 13, in all items of BOD, COD, SS, normal hexane extract content (N-Hex), total nitrogen content (TN) and total phosphorus content (TP) It can be seen that the experimental system has less treated water content than the control systems 1 and 2, and that good treatment has been achieved. In particular, comparing the treatment rates from each raw water, it can be seen that the experimental system of the present invention is very well treated with BOD of 86% or more, COD of 70% or more, and SS of 85% or more. In addition, the experimental system shows a very low value of 1/2 to 1/4 of the control systems 1 and 2 in terms of the total nitrogen content, and the experimental system is 1/4 to that of the control systems 1 and 2 in terms of the total phosphorus content. 1/10 is extremely low. Thus, according to the method of the present invention, not only BOD, COD and SS can be treated very well, but also the contents of nitrogen and phosphorus can be significantly reduced. In addition, when treated by the method of the present invention, BOD, COD, SS, N-Hex, TP are always drainage standards for public water bodies (for example, local governments may determine based on the Water Pollution Control Law). Possible addition standards include BOD: 20 mg / L or less, COD: 10 mg / L or less, SS: 20 mg / L or less, N-Hex: 5 mg / L or less, TN: 20 mg / L or less, TP: 1 mg / L or less) It can be seen that it is filled and constant regardless of fluctuations in the raw water, and it is treated well.

Moreover, from the transition graph of SV ₃₀ shown in FIG. 14, in the experimental system of the present invention, the value of SV ₃₀ has been stable from 95% to 98% from the 10th day in the microaerobic sludge digestion process. On the other hand, it can be seen that the control system 1 reached 100% on the 27th day. In the control system 1, since sludge was extracted on the 29th day, it decreased to about 75% on the 30th day. A value of SV ₃₀ of 100% means that the sludge is saturated, the digestion of the sludge no longer proceeds and the sludge needs to be extracted, that is, the generation of excess sludge. On the other hand, in the experimental system of the present invention, the SV ₃₀ value does not reach 100% even after the 80th day. This is because the digestion of the sludge is progressing, and the supernatant liquid can be returned to the flow rate adjustment process and / or the microaerobic microorganism treatment process for reuse without requiring removal of the sludge. Almost no sludge (surplus sludge) has to be generated, which means that volume reduction has been achieved.

  From the above results, according to the treatment method of the present invention, it is possible to reduce the volume of surplus sludge without generating sludge that needs to be disposed of (surplus sludge). Very good processing efficiencies can be achieved in all (BOD, COD, SS, normal hexane extract content, total nitrogen content and total phosphorus content), and particularly excellent processing can be achieved with respect to the total phosphorus content.

FIG. 1 is a schematic diagram showing an outline of the processing method of the present invention. FIG. 2 is a graph showing the transition of the BOD measurement values of the experimental system and the control system in the experimental plant. FIG. 3 is a graph showing the transition of the BOD treatment rate of the experimental system and the control system in the experimental plant. FIG. 4 is a graph showing the transition of the COD measurement values of the experimental system and the control system in the experimental plant. FIG. 5 is a graph showing the transition of the COD treatment rate of the experimental system and the control system in the experimental plant. FIG. 6 is a graph showing changes in SS measurement values of the experimental system and the control system in the experimental plant. FIG. 7 is a graph showing the transition of the SS treatment rate of the experimental system and the control system in the experimental plant. FIG. 8 is a graph showing the transition of N-Hex measurement values of the experimental system and the control system in the experimental plant. FIG. 9 is a graph showing the transition of the N-Hex treatment rate of the experimental system and the control system in the experimental plant. FIG. 10 is a graph showing the transition of the TN measurement values of the experimental system and the control system in the experimental plant. FIG. 11 is a graph showing the transition of the TN treatment rate of the experimental system and the control system in the experimental plant. FIG. 12 is a graph showing the transition of the T-P measurement values of the experimental system and the control system in the experimental plant. FIG. 13 is a graph showing transition of the TP treatment rate of the experimental system and the control system in the experimental plant. FIG. 14 is a graph showing the SV ₃₀ transition of the experimental system and the control system in the experimental plant.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flow control tank 2 1st microaerobic reaction tank 3 2nd microaerobic reaction tank 4 Sedimentation tank 5 Sludge concentration tank 6 Microaerobic sludge digestion tank 7 Supernatant liquid storage tank 8-10 Piping for recirculation

Claims (5)

Maintaining the organic wastewater in an aerobic atmosphere in which the dissolved oxygen amount exceeds 1.0 mg / l, and adjusting the flow rate of the wastewater;
A microaerobic microbial treatment step of microbially treating the wastewater in a microaerobic atmosphere having a dissolved oxygen content of 0.1 to 1.0 mg / l;
Next, a sludge sedimentation process in which wastewater from the microaerobic microorganism treatment process is separated into sludge and supernatant liquid in an anaerobic atmosphere,
A sludge concentration step in which the sludge obtained in the sludge precipitation step is concentrated and settled in an anaerobic atmosphere,
A microaerobic sludge digestion process for further digesting the sludge concentrated in the sludge concentration process in a microaerobic atmosphere with a dissolved oxygen content of 0.1 to 1.0 mg / l,
Collecting the supernatant liquid obtained in the microaerobic sludge digestion process and storing it in a microaerobic atmosphere with a dissolved oxygen content of 0.1 to 1.0 mg / l,
Including
Return the sludge obtained in the sludge precipitation process to the microaerobic microorganism treatment process,
Return the supernatant obtained in the sludge concentration process to the flow rate adjustment process,
A method for treating wastewater containing organic matter, wherein the digestive supernatant is quantitatively injected from the supernatant storage step into the flow rate adjustment step and / or the microaerobic microorganism treatment step.   2. The treatment method according to claim 1, wherein the dissolved oxygen amount in the microaerobic microorganism treatment step, the microaerobic sludge digestion step, and the supernatant liquid storage step is 0.5 to 0.8 mg / l.   The microaerobic microorganism treatment step includes a first microaerobic microorganism treatment step in which the wastewater from the flow rate adjustment step is treated in a microaerobic atmosphere having a dissolved oxygen amount of 0.1 to 1.0 mg / l, Including a second microaerobic microbial treatment process in which the wastewater from the microaerobic microbial treatment process is microbially treated in a microaerobic atmosphere having a dissolved oxygen content of 0.1 to 1.0 mg / l to promote decomposition of organic matter. The processing method according to claim 1 or 2.   The processing method according to claim 3, wherein the digestive supernatant liquid from the supernatant liquid storage step is returned to the first microaerobic microorganism processing step.   The processing method according to any one of claims 1 to 4, wherein a residence time is 12 to 24 hours in the sludge concentration step and the microaerobic sludge digestion step.