JP6977993B2 - Organic wastewater treatment method and treatment equipment - Google Patents

Description

The present invention relates to a method and a treatment apparatus for treating organic wastewater.

In the aerobic treatment of organic wastewater, particularly activated sludge treatment, surplus sludge containing grown microorganisms and the like is generated, and this disposal is costly. So far, various technologies for suppressing the generation of excess sludge have been developed, and sludge volume reduction technology using ozone is known at a practical level.

Patent Document 1 discloses a technique in which sludge generated by aerobic treatment is treated with ozone, thereby killing and decomposing microorganisms and suppressing the generation of excess sludge. Further, Patent Document 2 reports that the generation of excess sludge can be suppressed more efficiently by treating the sludge with ozone microbubbles.

Japanese Unexamined Patent Publication No. 2000-350995 Japanese Unexamined Patent Publication No. 2008-018378

Organic wastewater containing human waste contains a large amount of paper-derived fibers such as toilet paper. In particular, organic wastewater from parking areas, service areas, roadside stations, etc. has a relatively high proportion of human waste, and therefore contains a particularly large amount of fiber. In the course of research, the present inventors have focused on such organic wastewater containing urine as the organic wastewater to be treated.

However, since fibers are hardly decomposed by aerobic treatment and ozone treatment, the above-mentioned conventional technique cannot efficiently suppress the generation of excess sludge in the treatment of organic wastewater containing human waste.

Therefore, it is an object of the present invention to more efficiently suppress the generation of excess sludge and, by extension, the generation of sludge discharged to the outside in the treatment of organic wastewater containing human waste.

Excess sludge generated by aerobic treatment of organic wastewater is usually once concentrated by natural sedimentation in a concentration tank (about several tens of days to one month) and then disposed of. The present inventor paid attention to the reaction in this concentrating tank (for example, excess sludge concentrating tank, sludge storage tank, etc.), and as a result of allowing sludge containing fibers to stand under the same conditions as this concentrating tank, the fibers decomposed. I found that. As a result of further research based on this finding, the sludge obtained by solid-liquid separation of the aerobic treated product was treated (standing or agitated) in the same manner as this concentration tank, and this was treated with ozone and then aerobic again. We have found that the generation of excess sludge can be suppressed more efficiently by subjecting it to treatment, and the present invention has been completed.

That is, the present invention includes the following aspects:
Item 1. It is a method of treating organic wastewater containing human waste.
(A) A step of aerobic treatment of organic wastewater containing human waste,
(B) A step of solid-liquid separating at least a part of the aerobic treated product obtained in the step (a).
(C1) A step of allowing at least a part of the sludge obtained in the step (b) to stand or stir.
(D) A step of ozone-treating at least a part of the stationary or agitated product obtained in the step (c1), and (e) supplying the ozone-treated product obtained in the step (d) to the step (a). Processing method including steps.
Item 2. Item 2. The treatment method according to Item 1, wherein the standing or stirring treatment is performed at 10 to 35 ° C. Item 3. Item 3. The treatment method according to Item 1 or 2, further comprising a step (c2) of supplying at least a part of the sludge obtained in the step (b) to the step (a).
Item 4. Item 6. The treatment method according to any one of Items 1 to 3, wherein the organic wastewater contains toilet wastewater.
Item 5. Item 6. The treatment method according to any one of Items 1 to 4, wherein the content of the toilet wastewater is 15% by volume or more with respect to 100% by volume of the organic wastewater.
Item 6. Item 6. The treatment method according to any one of Items 1 to 5, wherein the ozone treatment is ozone bubble treatment.
Item 7. Item 6. The treatment method according to any one of Items 1 to 6, wherein the ozone treatment is ozone nanobubble treatment.
Item 8. Item 6. The treatment method according to any one of Items 1 to 7, wherein the aerobic treatment is an activated sludge treatment.
Item 9. Item 6. The treatment method according to any one of Items 1 to 8, wherein the object to be statically or agitated in the step (c1) is excess sludge.
Item 10. Item 3. The treatment method according to Item 3, wherein the feed to the step (a) in the step (c2) is return sludge.
Item 11. It is a treatment device for organic wastewater containing human waste.
(A) An aerobic treatment tank for aerobic treatment of organic wastewater containing human waste,
(B) A solid-liquid separation means for solid-liquid separating at least a part of the processed product obtained in the aerobic treatment tank (A).
(C1) A static or stirring treatment tank for statically or stirring at least a part of the sludge obtained by the solid-liquid separating means (B).
(D) An ozone treatment tank for ozone-treating at least a part of the treated product obtained in the stationary or stirring treatment tank (C1), and (E) the treated product obtained in the ozone treatment tank (D). A processing apparatus including a return means for returning to the aerobic processing tank (A).

According to the present invention, in the treatment of organic wastewater containing human waste, the generation of excess sludge can be suppressed more efficiently, and the generation of sludge discharged to the outside can be efficiently suppressed. In addition, the sludge obtained by solid-liquid separation of the aerobic treated material can be allowed to stand or stir in a conventional surplus sludge concentration tank, sludge storage tank, etc. In this case, existing equipment is used. It is economical because the wastewater treatment of the present invention can be carried out.

It is a schematic diagram of one Embodiment of this invention. It is a figure which shows the result of the decomposition test (Example 1) of a fiber. The vertical axis shows the average fiber length (μm), and the horizontal axis shows the number of days elapsed after allowing each sample sludge to stand. "Concentrated + TP" indicates a mixture of a portion of concentrated sludge and toilet paper (TP). It is a schematic diagram of one Embodiment of this invention.

In the present specification, the expressions "contains" and "contains" include the concepts of "contains", "contains", "substantially consists" and "consists of only".

1. 1. Method for Treating Organic Wastewater The present invention relates to a method for treating organic wastewater containing human waste, which comprises steps (a), (b), (c1), (d), and (e) as one aspect thereof. (In the present specification, it may be referred to as "the processing method of the present invention"). This will be described below.

Step (a) is a step of aerobic treating organic wastewater containing human waste.

Human waste is a mixture containing stool and urine, and is not particularly limited as long as this is the case. Human waste usually contains fibers derived from paper such as toilet paper (particularly cellulose fibers). Examples of human waste include drainage from toilet bowls of flush toilets (flush toilet drainage), toilet drainage of pumping toilets (including simple flush toilets) and waste in the human waste tank, and preferably flush toilets. Drainage is mentioned.

Organic wastewater is not particularly limited as long as it is wastewater containing human waste. The organic wastewater may consist only of human waste, but usually contains other wastewater other than human waste. Examples of other wastewater include kitchen wastewater; miscellaneous wastewater from wash basins, etc.; business wastewater from refueling offices, automobile repair offices, etc.

When the organic wastewater contains toilet wastewater (particularly flush toilet wastewater), the content of the toilet wastewater is, for example, 5 to 80% by volume, preferably 10 with respect to 100% by volume of the organic wastewater to be aerobic treated. It is ~ 70% by volume, more preferably 15-60% by volume, still more preferably 20-55% by volume.

Specific examples of "organic wastewater containing urine" include wastewater from rest facilities attached to roads such as service areas, parking areas, and roadside stations; domestic wastewater; amusement parks and zoos located in the suburbs. Suburban facilities such as parks, shopping centers, airports, and railway facilities can be mentioned.

"Organic wastewater containing human waste" may contain foreign substances, and in such cases, it is preferable to perform pretreatment and then aerobic treatment. Examples of the pretreatment include sand setting treatment, foreign matter removal treatment, crushing treatment and the like. The pretreatment can be carried out according to or according to the known method adopted for organic wastewater. The sand basin treatment is usually performed in a sand basin. The foreign matter removing process can be performed by a sorting process means such as a screen. The crushing process can be performed by, for example, a crusher or the like. These pretreatments make it possible to remove or reduce relatively heavy foreign matter and remove or reduce relatively large foreign matter.

If necessary, the "organic wastewater containing human waste" may be subjected to aerobic treatment after passing through a flow rate adjusting tank. Thereby, the input amount to the aerobic treatment can be appropriately adjusted. It is desirable that the flow control tank be equipped with a stirrer in order to prevent the generation of sediment and putrefaction.

The aerobic treatment is not particularly limited as long as the organic matter in the organic wastewater can be metabolized by the aerobic microorganism, and can be carried out according to or according to a known method. Examples of the aerobic treatment include activated sludge treatment, biofilm treatment and the like, and preferably activated sludge treatment.

Aerobic treatment (particularly activated sludge treatment) is usually carried out in an aerobic treatment tank (aerobic tank) equipped with a means for supplying an oxygen-containing gas such as air to organic wastewater (for example, an air diffuser). can.

The dissolved oxygen concentration in the aerobic treatment is, for example, 1 mg / L or more and 1 to 4 mg / L. The aerobic treatment can be performed under non-heating (room temperature or atmospheric temperature) or under heating. When activated sludge treatment is performed as an aerobic treatment, the MLSS (Mixed Liquor Suspended Solids) is preferably in the range of 3000 to 6000 mg / L. The treatment time for the aerobic treatment can be appropriately set according to the inflow amount of organic wastewater, the growth amount of activated sludge, and the like.

After the step (a), at least a part of the aerobic processed product is subjected to the following step (b).

The step (b) is a step of solid-liquid separating at least a part of the aerobic processed product obtained in the step (a).

The solid-liquid separation can be performed according to or according to a known method. Examples of the solid-liquid separation method include precipitation separation, membrane separation, centrifugation and the like, and preferred examples include precipitation separation. By solid-liquid separation, the aerobic treated product is divided into a liquid component cleaned by the aerobic treatment and sludge.

The liquid component separated by solid-liquid separation can be discharged to the outside after being subjected to disinfection treatment or the like. The disinfection treatment is not particularly limited as long as it is a treatment capable of sterilizing bacteria such as Escherichia coli, and examples thereof include chlorine disinfection treatment.

The MLSS of the sludge separated by solid-liquid separation is, for example, 4000 to 10000 mg / L, preferably 6000 to 10000 mg / L, and 70000 to 10000 mg / L. It is preferable that at least a part of this sludge (sometimes referred to as “return sludge”) is supplied to step (a) (step (c2)). This makes it possible to keep the amount of microorganisms in the aerobic treatment constant. Further, at least a part of this sludge (sometimes referred to as "surplus sludge") is subjected to the following step (c1).

The step (c1) is a step of allowing at least a part of the sludge obtained in the step (b) to stand or stir.

The standing or stirring treatment is performed by standing or stirring (preferably standing) the sludge. Thereby, the fibers in the sludge can be decomposed into a form easily decomposed by the above-mentioned aerobic treatment or the ozone treatment described later, or can be dissolved in the liquid.

The stirring is not particularly limited as long as it is a stirring for sludge concentration. For example, agitation performed to promote the concentration of sludge in a surplus sludge concentration tank, a sludge storage tank, or the like, and more specifically, agitation by a stirring rod, a stirring shaft, or the like can be mentioned.

The standing or stirring treatment may be carried out under heating, but is usually carried out at room temperature or at a high temperature (for example, 10 to 35 ° C.). The time of the standing or stirring treatment is not particularly limited, and examples thereof include 1 day to 3 months and 2 weeks to 2 months.

Although not a limited interpretation, it is believed that in the static or agitated treatment, anaerobic conditions are created in the sludge, which activates the metabolism of anaerobic microorganisms and decomposes the fibers. .. Therefore, it is desirable not to supply an oxygen-containing gas such as air in the static or stirring process.

Excess sludge generated by aerobic treatment of organic wastewater is usually once allowed to stand in a concentration tank (for example, excess sludge concentration tank, sludge storage tank, etc.) and concentrated by natural sedimentation (several tens of days to one month). Then, or after concentrating under conditions for promoting concentration with a stirring rod, a stirring shaft, etc., and then disposing of the product, the standing or stirring treatment in step (c1) can be carried out under the same conditions. Therefore, in the step (c1), the existing equipment of the prior art (for example, surplus sludge concentration tank, sludge storage tank, etc.) can be used as it is.

After the step (c1), both the naturally settled sludge and the liquid component of the supernatant can be subjected to the following step (d), or only the naturally settled sludge can be subjected to the following step (d). ..

The liquid component of the supernatant that is not subjected to the step (d) may be discharged to the outside after being subjected to a disinfection treatment or the like, or may be supplied to the step (a).

The sludge not subjected to the step (d) can be discharged to the outside as it is or after further concentration.

The step (d) is a step of ozone-treating at least a part of the stationary or agitated product obtained in the step (c1). Thereby, the microorganisms contained in the statically or stirred product can be decomposed, and the fiber decomposition product can be further decomposed by the step (c1).

The ozone treatment is not particularly limited as long as it is a method capable of oxidative decomposition by contacting ozone with a stationary or stirred product, and can be carried out according to or according to a known method. The ozone treatment can be performed, for example, by mixing bubbles containing ozone as a gas (ozone bubbles) or a liquid containing the bubbles with a standing or stirring product (ozone bubble treatment).

The mode particle size of the ozone bubble is, for example, 50 nm to 50 μm, preferably 50 nm to 10 μm, more preferably 50 nm to 1 μm, still more preferably 50 nm to 500 nm, still more preferably 50 nm to 300 nm, still more preferably 50 to 150 nm. be. The flocs contained in the stationary or agitated product usually have a size of several to several hundreds of μm, and if the ozone bubble is relatively large, ozone cannot reach the inside of the flocs. Therefore, by making the most frequent particle size of the ozone bubble smaller, the decomposition efficiency by the ozone treatment can be further improved. From this point of view, the ozone treatment is preferably ozone nanobubble treatment using nano-sized ozone bubbles (ozone nanobubbles).

Ozone bubbles can be prepared according to or according to known methods for producing microbubbles. For example, it can be manufactured by a gas-liquid mixing shear method, a static mixer type, a Venturi type, a cavitation type, a steam condensation type, an ultrasonic method, a swirling flow method, a pressure melting method, a micropore method, or the like.

At least a part of the ozone-treated product obtained in the step (d) is subjected to the following step (e).

The step (e) is a step of supplying the ozone-treated product obtained in the step (d) to the step (a). This makes it possible to further decompose the fiber decomposition product in the step (c1) and the decomposition product further decomposed by the ozone treatment.

The supply is not particularly limited as long as the ozone-treated product is finally subjected to the aerobic treatment, and may be directly supplied to the aerobic treatment tank or supplied to a stage prior to the aerobic treatment (for example, a flow rate adjusting tank). May be good.

According to the treatment method of the present invention, the fibers can be efficiently decomposed, the generation of excess sludge can be suppressed more efficiently, and the generation of sludge discharged to the outside can be efficiently suppressed. can.

2. 2. Organic Wastewater Treatment Device The present invention relates to a device for treating organic wastewater containing human waste, including (A), (B), (C1), (D), and (E), as one aspect thereof. In the present specification, it may be referred to as "the processing apparatus of the present invention"). This will be described below. A schematic diagram of an embodiment of the processing apparatus of the present invention is shown in FIGS. 1 and 3.

In the following description, conventionally known means (for example, pumps, pipes, etc.) can be used as various supply means and various discharge means. Supply and discharge between each tank and each means may be performed directly, or may be performed via a buffer tank such as a flow rate adjusting tank, an advection pit, or a sludge pit.

Each tank and each means in the apparatus of this invention may be provided with temperature control means as needed.

(A) is an aerobic treatment tank for aerobic treatment of organic wastewater containing human waste.

The aerobic treatment tank (A) is provided with means for supplying an oxygen-containing gas such as air (for example, an air diffuser) so that the step (a) can be carried out. Further, if necessary, the aerobic treatment tank may have a stirring means for stirring the inside of the tank.

The treatment apparatus of the present invention is provided with a pretreatment means for organic wastewater (for example, a sand basin; a separation treatment means such as a screen; a crusher, etc.) upstream of the aerobic treatment tank (A), if necessary. May be.

The aerobic treatment tank (A) has an organic wastewater supply means, a return sludge supply means, and ozone treatment so that organic wastewater containing human waste, return sludge, ozone-treated products, etc. can be efficiently supplied into the tank. It is preferable to have a material supply means or the like.

When the aerobic treatment tank (A) and the solid-liquid separation means (B) are separate tanks, the aerobic treatment tank (A) efficiently transfers the aerobic treated substance to the following solid-liquid separation means (B). It is preferable to have an aerobic treated product discharging means so that it can be discharged.

The shape, size, etc. of the aerobic treatment tank (A) are not particularly limited, and can be appropriately set according to the inflow amount of organic wastewater, the growth amount of activated sludge, and the like.

(B) is a solid-liquid separation means for solid-liquid separation of at least a part of the processed product obtained in the aerobic treatment tank (A).

The solid-liquid separation may be performed in a tank different from the aerobic treatment tank (A), or may be performed in the same tank. Preferably, the solid-liquid separation is performed in a tank separate from the aerobic treatment tank (A). In the former case, the solid-liquid separation means (B) exists as a solid-liquid separation tank (for example, a settling tank, a centrifugal separation tank, a membrane separation tank), and in the latter case, the solid-liquid separation means (B) is a settling tank. It may be the aerobic treatment tank (A) itself for functioning as an aerobic treatment tank (A), or it may be a membrane separation device provided in the aerobic treatment tank (A). In the former case, it is preferable that the solid-liquid separating means (B) is provided with an aerobic treated product supply means so that the aerobic treated product can be efficiently supplied into the tank.

The tank in which the solid-liquid separation means or the solid-liquid separation means is arranged is a surplus sludge discharge means for efficiently discharging the sludge obtained by the solid-liquid separation to the following static or stirring treatment tank (C1). Equipped with a return sludge discharge means for efficiently discharging sludge to the aerobic treatment tank (A), a liquid component discharge means for disinfecting the liquid component obtained by solid-liquid separation and discharging it to the outside. It is preferable to have.

The shape, size, etc. of the solid-liquid separating means are not particularly limited, and can be appropriately set according to the inflow amount of organic wastewater, the growth amount of activated sludge, and the like.

(C1) is a static or stirring treatment tank for statically or stirring at least a part of the sludge obtained by the solid-liquid separating means (B).

The static or stirring treatment tank (C1) is not particularly limited as long as it is a tank capable of statically or stirring sludge, and may not be provided with any means for adding any treatment. In the case of stirring, it is preferable to provide means for concentrating sludge (for example, a stirring rod, a stirring shaft, etc.). As the tank (C1), a conventional surplus sludge concentration tank, sludge storage tank, or the like can be adopted.

It is preferable that the stationary or stirring treatment tank (C1) is provided with surplus sludge supply means or the like so that the sludge obtained by the solid-liquid separation means (B) can be efficiently supplied.

The stationary or agitated treatment tank (C1) is a stationary or agitated product discharging means for efficiently discharging the static or agitated product to the following ozone treatment tank (D), after the static or agitated treatment. It is preferable to have a liquid component discharging means for discharging the liquid component as the supernatant to the outside for disinfection treatment, a liquid component discharging means for discharging the liquid component to the aerobic treatment tank (A), and the like. ..

The shape, size, etc. of the stationary or stirring treatment tank are not particularly limited, and can be appropriately set according to the inflow amount of organic wastewater, the growth amount of activated sludge, and the like.

(D) is an ozone treatment tank for ozone-treating at least a part of the treated product obtained in the stationary or stirring treatment tank (C1).

The ozone treatment tank (D) is provided with an ozone supply means (preferably an ozone bubble or a liquid supply means containing the ozone bubble) so that the step (d) can be carried out.

It is preferable that the ozone treatment tank (D) is provided with a stationary or agitated product supply means or the like so that the static or agitated product can be efficiently supplied in the tank.

It is preferable that the ozone treatment tank (D) is provided with an ozone-treated product discharging means for efficiently discharging the ozone-treated product to the aerobic treatment tank (A).

The shape, size, etc. of the ozone treatment tank (D) are not particularly limited, and can be appropriately set according to the inflow amount of organic wastewater, the growth amount of activated sludge, and the like.

(E) is a return means for returning the processed product obtained in the ozone treatment tank (D) to the aerobic treatment tank (A).

As the return means (E), conventionally known ones (for example, pumps, pipes, etc.) can be used for organic wastewater treatment. The supply and discharge between the tanks may be performed directly or may be performed via a buffer tank such as a flow rate adjusting tank.

The return means (E) preferably includes an ozone-treated product discharging means provided in the ozone treatment tank (D) and an ozone-treated product supply means provided in the aerobic treatment tank (A).

According to the treatment apparatus of the present invention, the treatment method of the present invention can be efficiently carried out, whereby the generation of excess sludge is suppressed more efficiently, and the generation of sludge discharged to the outside is efficiently suppressed. Can be suppressed.

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

Example 1. Fiber decomposition test Sludge was collected from the aeration tank of the septic tank installed in the Okuya parking area, and this was settled and concentrated to obtain concentrated sludge. The MLSS (Mixed Liquor Suspended Solids) of the concentrated sludge was measured by the sewage test method and found to be 8300 mg / L. A part of the concentrated sludge and toilet paper (TP) were mixed at a ratio of 10 g of TP to 1 L of the concentrated sludge to obtain a concentrated sludge-TP mixture.

By sealing 1 L each of the concentrated sludge and the concentrated sludge-TP mixture obtained above in a polypropylene container having a capacity of 1 L, the conditions are the same as those of the concentrated tank (non-aeration type) such as the excess sludge concentration tank and the sludge storage tank. The product was allowed to stand at room temperature (about 25 ° C.). After 1 day, 7 days, 14 days, 21 days, and 28 days from the start of standing, a part of the sludge is collected, the length of the fiber contained in the sludge is measured, and the average fiber is measured based on the measured value. The length was calculated. The fiber length was measured by taking a picture of sludge under a microscope and using image analysis software (ImageJ) to straighten the bent fiber on the image. The results are shown in FIG.

As shown in FIG. 2, both the concentrated sludge and the concentrated sludge-TP mixture are allowed to stand under the same conditions as the concentrated sludge (non-aeration type) such as the excess sludge concentration tank and the sludge storage tank, and the average fiber length is increased. Diminished. It is considered that the reduced amount is converted into a substance that is easily decomposed by aerobic treatment or ozone treatment, such as a monomer or an oligomer constituting the fiber, or is dissolved in a liquid.

Claims (8)

It is a method of treating organic wastewater containing human waste.
(A) A step of aerobic treatment of organic wastewater containing human waste,
(B) A step of solid-liquid separating at least a part of the aerobic treated product obtained in the step (a).
(C1) A step of allowing at least a part of the sludge obtained in the step (b) to stand or stir.
(D) A step of ozone-treating at least a part of the stationary or agitated product obtained in the step (c1), and (e) supplying the ozone-treated product obtained in the step (d) to the step (a). the process only contains,
The standing or stirring treatment is performed at 10 to 35 ° C.
The organic wastewater contains toilet wastewater and
The content of the toilet wastewater is 15% by volume or more with respect to 100% by volume of the organic wastewater .
Processing method. The treatment method according to claim 1 , further comprising (c2) a step of supplying at least a part of the sludge obtained in the step (b) to the step (a). The treatment method according to claim 1 or 2 , wherein the ozone treatment is an ozone bubble treatment. The treatment method according to any one of claims 1 to 3 , wherein the ozone treatment is ozone nanobubble treatment. The treatment method according to any one of claims 1 to 4 , wherein the aerobic treatment is an activated sludge treatment. The treatment method according to any one of claims 1 to 5 , wherein the object to be statically or agitated in the step (c1) is excess sludge. The treatment method according to claim 2 , wherein the feed to the step (a) in the step (c2) is return sludge. It is a treatment device for organic wastewater containing human waste.
(A) An aerobic treatment tank for aerobic treatment of organic wastewater containing human waste,
(B) A solid-liquid separation means for solid-liquid separating at least a part of the processed product obtained in the aerobic treatment tank (A).
(C1) A static or stirring treatment tank for statically or stirring at least a part of the sludge obtained by the solid-liquid separating means (B).
(D) An ozone treatment tank for ozone-treating at least a part of the treated product obtained in the stationary or stirring treatment tank (C1), and (E) the treated product obtained in the ozone treatment tank (D). a return means for returning to the aerobic treatment tank (a) seen including,
The standing or stirring treatment is performed at 10 to 35 ° C.
The organic wastewater contains toilet wastewater and
The content of the toilet wastewater is 15% by volume or more with respect to 100% by volume of the organic wastewater .
Processing equipment.

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