JPH0114836B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for processing organic waste liquids, particularly concentrated organic waste liquids such as human waste, through an extremely simple process and in a resource- and energy-saving manner.

Hereinafter, the details of the present invention will be explained by taking human waste treatment as a typical waste liquid as an example.

The process that has been evaluated as the most advanced in conventional human waste treatment and has the most examples is to add about 10 times as much diluted water to the human waste, perform biological treatment (activated sludge treatment is the most common), and then transfer the activated sludge to a settling tank. In this method, the supernatant water is subjected to coagulation sedimentation and sand filtration, and ozone treatment and activated carbon treatment are performed to remove chromaticity and COD, while the sludge is dehydrated, dried, and incinerated (hereinafter referred to as This is called the conventional process).

Although this conventional process appears to be reasonable at first glance, upon evaluating the technology from a strict viewpoint, the present inventors have come to realize that it inherently contains the following serious problems.

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

A large amount of 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 it is as high as 80%, a large amount of energy such as heavy oil is consumed in the drying and incineration process of the dehydrated cake (200-300/ton-D.S.).
Therefore, in conjunction with the above section, resources and
It is a very energy intensive process.

Although the problems pointed out by the present inventor are extremely serious, conventional methods have been unavoidable to some extent in order to highly treat organic wastewater and prevent pollution of the aquatic environment. However, the present inventor has strong doubts about the current level of technology, and has conducted studies to realize a process that can rationally solve the drawbacks of the conventional process. The present invention has now been completed.

The effects of the present invention can be said to be surprising,
Conventional processes such as coagulation sedimentation, sand filtration, ozone treatment,
The processes of activated carbon adsorption, sterilization, mechanical dewatering of sludge, and addition of dehydration aids are all eliminated, and the quality of the treated water is far superior to that of conventional processes, and operating costs can be significantly reduced. can.

That is, in the present invention, after biologically treating an organic waste liquid, the biologically treated water is subjected to indirect heating evaporation treatment using a vapor compression method and/or a multiple effect method, and the condensed water of the evaporated water vapor is converted into the treated water of the organic waste liquid. In addition, at least the surplus activated sludge generated from the biological treatment process is mixed with an oil having a boiling point higher than that of water, and after being evaporated and dried, the dried sludge is incinerated. It's a method.

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

The removed human waste 1 is allowed to flow into a biological nitrification and denitrification process 2 (which may also be a nitrification process or a denitrification process) without adding dilution water to remove BOD, nitrogen components, and the like. Biological nitrification and denitrification process 2
Examples of methods that can be used include a nitrifying solution circulation method, a step inflow method, an aerobic denitrification method, and a batch treatment method, which use BOD components in human waste as an organic carbon source for denitrifying bacteria.

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. On the other hand, solid-liquid separation step 4
The separated liquid 7 flows into an evaporation step 8 using a vapor compression method.

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 liquid flowing into the evaporation step 8, that is, the separated liquid 7, is also at a temperature of about 40°C, so it takes a while to heat it to the evaporation temperature (usually the pressure inside the evaporator 8' is set to 100°C). This has the important effect of reducing the amount of heat required. This means the important technical concept of indirectly utilizing the heat generated by the microbial oxidation reaction in the evaporation step 8.

Therefore, the inflow liquid is treated as water vapor condensed water (this is highly treated human waste water) in the heat exchanger 9.
After being preheated to a temperature of about 80℃ by 12',
It flows into the evaporation step 8 and is evaporated and concentrated, resulting in a concentrated liquid 11
It is discharged as. On the other hand, the water vapor 12 evaporated in the evaporation step 8 is compressed and heated in a vapor compressor 13 using a mechanical compressor or a salmon compressor, and then flows into the indirect heating section 14 of the evaporation step 8 again to be used as a heating source. used. Indirect heating section 1
At step 4, the water vapor is condensed, becomes the condensed water 12', 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 as human waste treated water. Note that 16 is water vapor for starting up the evaporation step 8. In addition to the vapor compression method shown in the illustrated example, the evaporation step 8 may be a multiple effect evaporation method or a combination of a vapor compression method and a multiple effect evaporation method.

Therefore, the concentrated liquid 11 is concentrated to 1/40 to 1/50 of the flow rate of the inflow liquid, and is an extremely dark brown liquid with a high COD concentration. Dispose of by incineration such as medium combustion incineration.

On the other hand, surplus activated sludge 17 generated from the biological nitrification and denitrification process 2 is mixed with oil 19 having a boiling point higher than water, such as heavy oil or waste oil, in a mixing tank 18 to form a mixed slurry 20 of sludge and oil. Mixed slurry 20
The water vapor flows into the No. 1 can 21 of the evaporative drying process 10 equipped with multiple-effect evaporators 21, 21', and 21''. Steam 23 is supplied from the boiler 22 to the indirect heating section 24 in the No. 1 can 21 to form a mixed slurry. The water in the slurry 20 is evaporated, and the evaporated steam 25 is caused to flow into the indirect heating section 24' in the No. 2 can 21', and the mixed slurry 20' with reduced moisture is pumped from the No. 1 can 21 to the No. 2 can 21'. The water in the mixed slurry 20' is further evaporated using the latent heat of condensation of the evaporated water vapor 25. The mixed slurry 20'' from the No. 2 can 21' is also evaporated and dried in the same manner.

However, the evaporated steam 2 from the No. 3 can 21″
5'' is condensed in a condenser (condenser) 26 and condensed water 27', 2 from can 2 21' and can 3 21''
7'' and is combined with the treated water 15 via an oil separation process (coalexer) not shown.
In addition, 24'' is an indirect heating part, 25' is evaporated steam,
27 is condensed water, 28 is a vacuum pump for discharging non-condensable gas, 34 is separately supplied boiler water supply,
The condensed water 27 passes through the boiler 22 and becomes the steam 2.
It becomes 3.

Now, the mixed slurry 29 discharged from the No. 3 can 21'' is a mixed slurry of oil and sludge with a moisture content of about 10%, with most of the moisture removed by evaporation, so it can be extracted using an oil extractor such as a screw press. 30, the oil and sludge in the mixed slurry 29 are separated, and the separated oil 31 is recycled to the mixing tank 18.Meanwhile, the deoiled sludge 32 is incinerated in the boiler 22, and steam 2
Collect 3. In addition, sludge, garbage, etc. should be removed from boiler 2.
Co-firing may be performed in step 2. 33 is incineration residue.

Regarding the disposal of the concentrated liquid 11 discharged from the evaporation step 8, the dried substance may be incinerated in the boiler 22 after being treated with an evaporator such as a drum dryer, or it may be directly sprayed and burned. However, it is best to concentrate it to the extent that it maintains its fluidity without being evaporated to dryness, then mix it with the surplus activated sludge 17 as shown in the example shown in the figure, and process it in the evaporation drying step 10 using oil as a medium. suitable. According to this method,
This is because a separate processing step for the concentrated liquid 11 becomes unnecessary.

Furthermore, the water vapor 2 generated in the boiler 22
Since the amount of water vapor 3 is often larger than the amount of water vapor required in the multi-effect evaporator, the remaining water vapor 23' is supplied to the evaporation process 8, the heating source for the heat exchanger 9, the heating of the administration building, etc. It is better to do so. Moreover, if the human waste removed from human waste is supplied to the oil extractor 30, the oil extraction efficiency will be improved.

In addition, the heat retained in the exhaust gas of the boiler 22 can be used directly or used to prepare hot water and used as a heat source for the heat exchanger 9, vapor compressor 13, mixing tank 18, oil extractor 30, etc., or can be used for incineration of waste at a human waste treatment plant. If the waste incineration plant is adjacent to the waste incineration plant, the residual heat from the waste incineration plant is used in the evaporation process 8.
Needless to say, it may also be used in the multi-effect evaporator mentioned above.

Furthermore, although not shown, the evaporative drying step 10 may be performed by a vapor compression method or a combination of this and a multiple effect evaporation method, and it goes without saying that the effects of the present invention can be fully exhibited. Furthermore, a method of concentrating the water in advance using a reverse osmosis membrane, an ultrafiltration membrane, etc. before entering the evaporation step 8 can also be adopted.

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

All of the steps that were essential in conventional processes, such as flocculation and sedimentation (or flotation) of biological treatment liquid, sand filtration, ozone treatment, activated carbon adsorption, and sterilization, are no longer necessary, and the process is far superior to conventional processes. water quality can be obtained.

Therefore, in addition to being highly 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. can get.

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, odor components, and SS, so if the raw liquid is directly evaporated without using the process of the present invention, a large amount of ammonia, ammonia, and It contains volatile organic acids and odor components, and is also prone to scale formation. Therefore, careful attention must be paid to prevent odor from leaking from the evaporation tank, and condensed 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 and scale-forming components such as sulfides, we perform evaporation concentration and drying treatment using vapor compression, etc., so there is almost no scale formation, and BOD is contained in the generated water vapor and its condensed water.
The water quality is clear, colorless and comparable to distilled water, with no ammonia nitrogen or odor components. In addition, there is no leakage of malodorous components from the evaporation tank.

If 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.
Running costs become extremely high (500 to 600 yen/Kl - human waste) to reduce COD to several mg/, but
In the present invention, since the biological treatment liquid is evaporated, the treated water is completely colorless and has an extremely low COD of 0 to 0.5 mg/.

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 dehydrated cake has a very high rate of about 80 to 85%, 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 to 300/ton-D.S.) of auxiliary fuel is required for drying and incinerating the dehydrated cake.

On the other hand, in the present invention, since coagulation and sedimentation sludge is not generated and no mechanical dehydration step is required, the moisture content of the dried product can be easily lowered and a dried product that is found in natural areas can be obtained.

The chloride ion concentration of human waste treated water using the conventional method is
Since the chlorine ion concentration is as high as 300 to 3000 mg/ml, 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.

Since oil such as heavy oil is added to surplus activated sludge and evaporated, fluidity is not lost even when water evaporates, so water can be easily evaporated in an evaporator, and most of the added oil can be removed. Since the oil is recovered and reused, the amount of heavy oil required is also extremely small.

Next, examples of the present invention will be described.

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 carried out by biological denitrification process with nitrification fluid circulation 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 countermeasure 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 20000-21000
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 45°C, and between 33° and 35°C during the winter.

A chemical-free centrifugal thickener (screw decanter type) was used for solid-liquid separation of the slurry flowing out of the biological treatment tank, and most of the thickened sludge was recycled to the biological treatment tank, with a portion being discharged as surplus biological sludge. . After the residual SS in the centrifugal concentrated separation liquid was sufficiently removed by precipitation or filtration, it was fed to a self-vapor compression evaporator and concentrated to a concentration ratio of more than 40 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 550-680mg/
, Soluble COD 430~520mg/, Chromaticity 2500~3000
The concentration of chloride ions was 3,000 to 3,200 mg/day.

The above evaporator is a small experimental scale falling liquid film type.
Roots type steam compressors were used in each case. The water quality of the condensed water of evaporated water vapor (this becomes highly processed water with no dilution of human waste) is PH7.0, no SS, no color,
The results were very good, with COD 0-0.5 mg/, BOD 1-3 mg/, phosphoric acid not detected, and NH ₃ -N 5 mg/ or less.

On the other hand, the concentrate from the evaporator and excess sludge (5.5Kg) generated from the non-dilution biological nitrification and denitrification process
Heavy oil A was added to the mixed slurry of the slurry (-D・S/Kl- human waste), dried in a multi-effect evaporator according to the CG process manufactured by Ebara Infilco Corporation, and then incinerated. The amount of oil required for this CG process is
The amount was extremely small at 0.15 per kg of solids in the mixed slurry supplied to the CG process. In other words, the heavy oil cost required to treat 1 kg of human waste is 82
Yen/Kg - It was human waste.

In addition, the cost required to evaporate biologically treated water using the vapor compression method was as low as 25 KWH per ^cubic meter of biologically treated water, or 375 yen/Kl of human waste. moreover,
The power cost of the aeration blower required for the biological nitrification and denitrification process is approximately 300 yen/Kl - human waste, and the operating cost of the entire process is approximately 1,000 to 1,100 yen/Kl including electricity costs for various pumps, etc. Compared to Kl-human waste, which requires maintenance and management costs of 3,500 to 4,000 yen/Kl-human waste in the conventional low dilution two-stage activated sludge method, the operating costs of the present invention are much lower.
Moreover, the treated water quality was overwhelmingly superior to that of conventional processes.

[Brief explanation of drawings]

The drawing is a flow sheet illustrating one embodiment 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 process, 8'... Evaporator, 9... Heat exchanger, 10... Evaporation drying process, 11... Concentrated liquid, 12, 16, 23, 2
3'... Steam, 12', 27, 27', 27''... Condensed water, 13... Vapor compressor, 14, 24, 24', 2
4″... Indirect heating section, 15... Treated water, 17... Excess activated sludge, 18... Mixing tank, 19... Oil, 20, 20',
20″, 29…Mixed slurry, 21…No. 1 can, 2
1'...No. 2 can, 21''...No. 3 can, 22...Boiler, 2
5, 25', 25''... Evaporated steam, 26... Condenser, 28... Vacuum pump, 30... Oil extractor, 31... Separated oil, 32... Sludge, 33... Incineration residue, 34... Boiler feed water.

Claims (1)

[Scope of Claims] 1. After biologically treating the organic waste liquid, the biologically treated water is subjected to indirect heating evaporation treatment using a vapor compression method and/or a multiple effect method, and the condensed water of the evaporated water vapor is converted into the organic waste liquid. An organic waste liquid characterized by adding and mixing an oil having a boiling point higher than that of water to the surplus activated sludge generated from at least the above-mentioned biological treatment process, evaporating and drying the treated water, and then incinerating the dried sludge. processing method. 2 The concentrated liquid obtained by the indirect heating evaporation treatment is mixed with the surplus activated sludge, and the oil is added and mixed to the mixture, and the evaporation drying treatment is performed.
The method described in section. 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. Claim 1, wherein the biological treatment step is carried out without adding dilution water.
3. The method described in Section 2, Section 2, or Section 3.