JPH0114833B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for processing organic waste liquid such as human waste through an extremely simple process and in a resource- and energy-saving manner.

The details of the present invention will be explained below by taking human waste treatment as an example.

[Prior art]

The process that has been evaluated as the most advanced in conventional human waste treatment and has the most examples is to add dilution water to human waste and perform biological treatment (activated sludge treatment is the most common), and then convert the activated sludge into a solid liquid in a settling tank. Separate and coagulate the supernatant water through sand filtration, and further ozone treatment to remove chromaticity and COD.
This method involves dewatering, drying, and incinerating the sludge while treating it with activated carbon.

Although this process appears to be rational at first glance, when the technology is evaluated from a strict viewpoint, the present inventors have come to realize that the following serious problems inherently exist.

That is, since many unit operations are arranged in series, the process is complex and maintenance is poor.

A flocculant is required in the coagulation solid-liquid separation process such as the coagulation-sedimentation process. Furthermore, the sludge dewatering process also requires the addition of a large amount of dewatering aid. Therefore, it is a resource-intensive process.

Ozone treatment requires a large amount of electricity to generate ozone, and activated carbon treatment also requires a large amount of expensive activated carbon. Furthermore, it is an energy-intensive process, as it requires a large amount of thermal energy to regenerate activated carbon.

In addition to requiring large amounts of dehydration aids such as cationic polymers, ferric chloride, and slaked lime to dehydrate excess biological sludge generated from the biological treatment process and flocculated sludge generated from the coagulation-sedimentation process, the water content of the dehydrated cake is As this rate is high at around 80%, a large amount of energy such as heavy oil is consumed in the process of drying and incinerating the dehydrated cake. Therefore, in combination with the above items, this is a process that consumes a large amount of resources and energy.

Although the problems pointed out by the present inventors are extremely serious, conventional methods have failed to treat organic wastewater and obtain the high quality of treated water necessary to prevent sludge in the aquatic environment. To some extent, this was considered to be unavoidable.

[Purpose of the invention]

The present invention was completed based on the inventor's strong doubts about the current state of the art, and provides a method for treating organic waste liquid that can rationally solve the drawbacks of the conventional processes. The purpose is to

The effects of the present invention can be described as surprising, and all of the conventional processes of coagulation sedimentation, sand filtration, ozonation, activated carbon adsorption, sterilization, mechanical sludge dewatering, and addition of dehydration aids are completely eliminated. It is no longer necessary, and the quality of the treated water is lower than that of conventional processes.
It is extremely superior and can significantly reduce operating costs.

[Structure of the invention]

That is, the present invention biologically treats organic waste liquid in a biological treatment process and uses the vapor compression method and/or the treated water.
Alternatively, an organic waste liquid is introduced into an indirect heating evaporation concentration process using a multiple effect evaporation method and subjected to concentration treatment, and the concentrated liquid discharged from the evaporation concentration process is further treated in a post-treatment process including an incineration process. This is the processing method.

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

BOD, which allows the filtered human urine 1 to flow into the biological nitrification and denitrification process 2 without adding dilution water;
Removes nitrogen components, etc. Biological nitrification and denitrification process 2 uses a nitrification solution circulation method that uses BOD components in human waste as an organic carbon source for denitrification bacteria;
A step inflow method, an aerobic denitrification method, a rotation treatment method, etc. can be adopted.

The activated sludge slurry 3 flowing out from the biological nitrification and denitrification process 2 is subjected to solid-liquid separation in a solid-liquid separation process 4 such as a centrifugal thickener, and most of the separated sludge 5 is biologically nitrified as return sludge 6. Recycled to denitrification step 2.

Furthermore, if human waste is treated with anaerobic or aerobic digestion and then treated with biological nitrification and denitrification, BOD is removed in the digestion process, resulting in a lack of organic carbon sources for denitrifying bacteria, and Since it is necessary to add expensive organic carbon sources such as methanol, ethanol, and acetic acid, which would lead to extremely unreasonable results, it is possible to directly biologically nitrify and denitrify human waste without undergoing such a digestion process. It is desirable to do so.

The separated liquid 7 from the solid-liquid separation step 4 then flows into an evaporative concentration step 8 using a vapor compression method, a multiple effect evaporation method, or a combination of both.

In addition, in biological nitrification and denitrification process 2, human waste is treated without dilution, so the microbial oxidation reaction generated heat (usually 30,000 to 40,000 kcal) is generated when biologically oxidizing BOD, ammonia nitrogen, etc. in human waste. /Kl
- Human waste) causes the water temperature of the activated sludge slurry 3 in the biological nitrification and denitrification process 2 to rise to 40°C or higher. Therefore, the inflow liquid to the evaporation concentration step 8, that is, the separated liquid 7, is also at a temperature of about 40°C, which has the important effect of reducing the amount of heat required to heat it to the evaporation temperature (usually set at 100°C). is obtained. This means the important technical concept of indirectly utilizing the heat generated by the microbial oxidation reaction in the evaporation concentration step 8.

The inflow liquid is preheated in the heat exchanger 9 to a temperature of about 80°C by water vapor condensed water (this is treated water) 10, and then flows into the evaporation concentration step 8 where it is evaporated. It is concentrated and discharged as a concentrated liquid 11. On the other hand, the water vapor 12 evaporated in the evaporation concentration step 8 is compressed and heated in a vapor compressor 13 using a mechanical compressor or a thermo compressor, and then returned to the indirect heating section 14 of the evaporation concentration step 8.
and is reused as a heating source. The steam is condensed in the indirect heating section 14, becomes the condensed water 10, passes through the heat exchanger 9, and is then discharged as treated water 15. The treated water 15 is colorless and transparent, almost equivalent to distilled water, and has extremely good water quality, exhibiting the highest quality of human waste treated water. Note that 16 is water vapor for starting up the evaporation concentration step 8.

The concentrated liquid 11 is 1/10 to 1/of the flow rate of the inflow liquid.
20, and has a very dark brown color.
Since it is a liquid with a COD concentration and the salt concentration has increased to more than a few percent, it is an essential step to finally incinerate this concentrated liquid and oxidize and decompose the COD components. In other words, it is not possible to dispose of this concentrated liquid or dry product.
This causes secondary pollution in the form of COD pollution and salt leaching at the disposal site. In the most preferred embodiment, as shown in the illustrated example, excess sludge 17 and concentrated liquid 11 discharged from the solid-liquid separation process 4 are led to an evaporative drying process 18 such as a rotary drum dryer and dried, and then the dried solids are dried. This is to incinerate material 19.

Water vapor 1 evaporated from this evaporative drying step 18
It is important that the steam 8' is also compressed by the steam compressor 20 and circulated in an indirect heating section such as a rotating drum to recover the latent heat of vaporization of the steam 18'. Note that 21 is condensed water, 22 is a heat exchanger, and 15' is concentrated water after heat exchange, which is combined with the treated water 15 and discharged.

The evaporation concentration step 8 and the evaporation drying step 18 are preferably carried out at atmospheric pressure, whereby the biological treatment liquid undergoes heat treatment at approximately 100°C, which automatically sterilizes pathogenic bacteria such as Escherichia coli. The chlorine sterilization process is no longer necessary. Therefore,
The formation of trihalomethanes by chlorine injection is not possible.

In addition, the dry solids 19 are supplied to a boiler or a pyrolysis furnace 23, and the recovered thermal energy 24 is used for driving the vapor compressors 13, 20, as a heating source for the evaporative concentration step 8, the evaporative drying step 18, and the inflow described above. Of course, it is also possible to use it for preheating liquid. 25 is a residue (incineration ash, etc.).

Furthermore, although not shown, it goes without saying that the effects of the present invention can be fully demonstrated by performing the evaporative drying step 18 using a vapor compression method, a multiple effect evaporation method, or a combination of these methods. But that's fine. Furthermore, a method of concentrating the water in advance using a reverse osmosis membrane, an ultrafiltration membrane, etc. before entering the evaporation concentration step 8 can also be adopted.

〔Effect of the invention〕

As described above, according to the present invention, many important effects as described below can be obtained, and various drawbacks of conventional processes can be fundamentally solved.

All processes that were essential in conventional processes, such as flocculation and sedimentation (or flotation) of biological treatment liquid, sand filtration, ozone treatment, and activated carbon adsorption, are no longer necessary.
Furthermore, it is possible to obtain treated water quality that is far superior to conventional processes.

Therefore, in addition to being extremely effective in preventing environmental pollution, the process is also extremely simplified, and there is no need for flocculants, ozone generation power, activated carbon replenishment, and activated carbon regeneration energy, resulting in significant resource and energy savings. It will be done.

In addition, the process of dewatering excess activated sludge and coagulated sedimentation (floating) sludge using a mechanical dehydrator, which was essential in conventional processes, can be eliminated, and at the same time, the addition of dewatering aids such as cationic polymers is no longer necessary. Great resource effect.

Concentrated organic waste liquids such as human waste contain large amounts of ammonia, organic acids, and odor components. Therefore, if the raw liquid is directly evaporated without using the process of the present invention, a large amount of ammonia and volatile components will be contained in the generated water vapor. Contains organic acids and odor components.
Therefore, careful attention must be paid to measures against leakage of odors from the evaporation tank, and concentrated water of generated steam cannot be discharged as treated water as in the present invention.

On the other hand, according to the present invention, volatile organic components, ammonia,
After removing odor components, we perform evaporation concentration and drying treatment using vapor compression methods, etc., so that the generated water vapor and its condensed water are free of BOD components, ammonia nitrogen, and odor components, resulting in water quality comparable to that of distilled water, which is clear and colorless. It will be done. In addition, there is no leakage of malodorous components from the evaporation tank.

When coagulation and sedimentation (floating) treatment is performed, flocculated sludge is inevitably generated, and its treatment and disposal are inevitably required, but flocculated sludge has very poor dewatering properties and has become a major problem. On the other hand, in the present invention, such a problem cannot occur because no flocculation treatment step is required and no flocculated sludge itself is generated.

In conventional processes, COD and chromaticity components of treated water cannot be completely removed in the coagulation treatment process, so ozone treatment and activated carbon treatment processes are essential.
Although the running cost is extremely high even if COD is reduced to several mg/kg, the present invention evaporates the biological treatment solution, so the treated water is completely colorless.
COD is also extremely low at 0-1mg/.

In the conventional sludge treatment process, a dehydration aid such as a cationic polymer is added to the mixed sludge of surplus activated sludge and flocculated sedimentation sludge, and the water is dehydrated using a mechanical dehydrator such as a belt press. The rate is extremely high at around 80%, and since inorganic substances such as aluminum hydroxide coexist in the dehydrated cake, the calorific value of the dehydrated cake is low.
Therefore, a large amount (usually
200-300/ton-DS) of auxiliary fuel is required.

On the other hand, in the present invention, since no coagulated and settled sludge is generated and no mechanical dehydration step is required, the moisture content of the dried material can be easily reduced and a dried material that is in the self-combustion range can be obtained. Therefore, no auxiliary fuel such as heavy oil is required during incineration.

The chloride ion concentration of human waste treated water using the conventional method is
Since the chloride ion concentration is as high as 300 to 3000 mg, it has been difficult to use it as irrigation water for forests and fields, but since the water treated by the present invention is close to distilled water, the chlorine ion concentration is only about a few ppm. Therefore, it can be used as irrigation water and forest spraying water.

Conventionally, slurry containing a large amount of suspended solids was considered to be inapplicable because the suspended solids adhered to the heat transfer surface as evaporation and concentration progressed, and it was considered that slurry could not be applied to various solutions containing almost no suspended solids, such as seawater. The present invention has been devised so that the vapor compression method or the multiple effect evaporation method, which has only been applied to slurry products, can be easily applied to slurry-like materials. Ta.

The concentrated liquid is finally incinerated, and the
Since the COD component and chromaticity component are completely thermally decomposed, secondary pollution from the concentrated solution is not caused, and at the same time, the calorific value of the COD component and chromaticity component in the concentrated solution can be effectively utilized.

〔Example〕

After removing the residue from human waste (containing 10% septic tank sludge) delivered to the human waste treatment plant in Zushi City, Kanagawa Prefecture, the amount of waste processed is
No-dilution treatment was performed using a nitrified solution circulation biological denitrification process at a scale of 100/min. As a result of non-dilution treatment, foaming in the nitrification tank was severe, but adding antifoaming water was not desirable as it would increase the amount of water to be evaporated and lower the water temperature. As a measure against foaming, a defoamer (which rotates an impeller to break the foam) was installed in the foam layer above the liquid surface of the nitrification tank.

MLVSS of biological denitrification process is 20000-25000
mg/, and the residence time was 7 days. The water temperature in the biological treatment tank decreases in summer due to the heat produced by the oxidation reaction of microorganisms.
The temperature was maintained between 42° and 25°C, and between 33° and 35°C in winter.

A chemical-free centrifugal concentrator (super decanter) is used for solid-liquid separation of biological treatment tank effluent slurry.
Most of the thickened sludge was recycled to the biological treatment tank, and a portion was discharged as surplus biological sludge. The centrifugal concentrated separation liquid was supplied to a self-vapor compression evaporation can and concentrated to a concentration ratio of more than 20 times.

The water quality of this evaporator inflow liquid is water temperature 40° to 42°C, pH
7.0-7.2, ammonia nitrogen 5mg/or less, soluble BOD 10mg/or less, soluble phosphoric acid 550-680
mg/, soluble COD430-520 mg/, chromaticity 2500
It was ~3000 degrees and chloride ions were 3000~3200mg/.

The above evaporation can uses a falling liquid film type that can be realized on a small scale.
Roots type steam compressors were used in each case. The water quality of the condensed water of evaporated water vapor (this becomes the undiluted treated water of human waste) is PH7.0, no SS, no color, COD1
mg/or less, BOD 5mg/or less, phosphoric acid not detected, and NH ₃ -N 5mg/or less, which was extremely good.

On the other hand, the concentrated liquid from the evaporation can and excess biological sludge were mixed and supplied to a closed self-vapor compression type drum dryer for evaporation drying, and the mixture was taken out as a dried product with a moisture content of 50%. The lower heating value of dry matter is
Due to its high 4800kcal/KgD.S and low moisture content, it easily self-combusted in a fluidized fluidized furnace.

In the above process, there was no need to use any chemicals or fuels such as heavy oil, and the process functioned smoothly using only electricity. The electricity required for processing biological treatment liquid and surplus biological sludge is 1Kl of human waste.
It was extremely energy-saving, with 40 to 45 kwh per unit. In addition, the power required for the biological treatment process was only for the aeration blower, but the power required for the blower was 15 to 20 kwh per 1Kl of human waste, and the total power required for the process was 55 to 65 kwh, so the total treatment cost was 1100 yen to 1300 yen/Kl and actual cost of conventional process
Significant cost savings compared to 3,500 yen to 4,000 yen/Kl.

[Brief explanation of drawings]

The drawings are flow sheets illustrating embodiments of the invention. 1... Sludge removal human waste, 2... Biological nitrification and denitrification process,
3...Activated sludge slurry, 4...Solid-liquid separation step, 5...
Separated sludge, 6... Returned sludge, 7... Separated liquid, 8... Evaporation concentration step, 9, 22... Heat exchanger, 10, 15',
21... Condensed water, 11... Concentrated liquid, 12,16,1
8'...Steam, 13,20...Vapor compressor, 14...
Indirect heating section, 15...treated water, 17...excess sludge, 1
8... Evaporation drying step, 19... Dry solid matter, 23... Boiler or pyrolysis furnace, 24... Thermal energy, 25
...residue.

Claims (1)

[Scope of Claims] 1 Organic waste liquid is subjected to biological treatment in a biological treatment process, and the treated water is led to an indirect heating evaporation concentration process using a vapor compression method and/or a multiple effect evaporation method for concentration treatment, and the evaporation concentration is A method for treating organic waste liquid, characterized in that the concentrated liquid discharged from the process is further treated in a post-treatment process including an incineration process. 2. The method according to claim 1, wherein surplus sludge generated from the biological treatment step is mixed with the concentrated liquid and guided to a post-treatment step including the incineration step. 3. Claim 1, wherein the biological treatment step is a step in which at least a biological nitrification reaction occurs.
or the method described in paragraph 2. 4. The method according to any one of claims 1 to 3, wherein the post-treatment step including the incineration step comprises an evaporative drying step and a subsequent incineration step.