JPH0114834B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for treating human waste, sewage, and other organic wastewater. [Prior art] The process that has been evaluated as the most advanced in conventional human wastewater treatment, and the number of examples of which has been implemented rapidly in recent years, involves adding dilution water to human waste, performing biological nitrification and denitrification treatment, and then converting activated sludge into activated sludge. This method involves separating solid and liquid in a settling tank, and then coagulating and settling the supernatant water, filtering it with sand, and then subjecting it to ozone treatment and activated carbon treatment. At first glance, this process appears to be a fairly reasonable process and is easily evaluated as an excellent method. However, when the technology is evaluated from a strict perspective, the inventor found that it inherently contains the following serious problems. I came to realize that. In other words, because many unit operations are arranged in series, the process is complex and maintenance is poor. In addition to requiring the addition of a large amount of flocculant in the coagulation-sedimentation or coagulation-floating process, which consumes resources, coagulation-sedimentation sludge, which is difficult to dewater, is generated, making its treatment and disposal difficult and requiring a large amount of expense. It takes. About 20~ to ozone generation power for ozone treatment
It requires a large amount of electricity of 300KWH/Kg of ozone, and the activated carbon treatment uses expensive activated carbon of 500 to 600 yen/Kg of activated carbon, so the cost of activated carbon treatment becomes large. In order to stop using activated carbon, it is necessary to regenerate the waste activated carbon, but regeneration requires a large amount of thermal energy, which is not energy-saving after all. The present inventor had a strong inquiry into the technical level of the conventional process which had the above-mentioned problems, and proceeded with the study and completed the present invention. [Object of the Invention] That is, an object of the present invention is to provide a method for treating organic wastewater that can extremely rationally solve the above-mentioned problems of the conventional methods. [Structure of the Invention] The present invention provides biological treatment of organic wastewater in a biological treatment process in which a biological nitrification reaction is performed without digestion treatment, and after concentrating the biologically treated water in an evaporation concentration process. , a method for treating organic wastewater, characterized in that the concentrated liquid is treated in a post-treatment process including an incineration process. The effects of the process of the present invention can be said to be surprising, as the conventional processes of coagulation sedimentation, sand filtration, ozone treatment, and activated carbon adsorption are completely unnecessary, and the quality of the treated water is significantly superior to that of the conventional process. Maintenance costs will also be reduced. An embodiment of the present invention will be described below with reference to the drawings. The removed human waste (often contaminated with septic tank sludge) 1 is passed into the biological treatment process 2 using the biological nitrification and denitrification method without adding dilution water, which mainly removes nitrogen such as BOD and ammonia. Thoroughly remove components. As biological treatment step 2,
A nitrification liquid circulation type that uses the BOD component in human waste 1 as a hydrogen donor for denitrifying bacteria, a stepwise inflow type of human waste, an aerobic denitrification type, and a batch processing type are adopted. Adding a large amount of dilution water to the biological treatment step 2 is not preferable because it not only causes a decrease in water temperature but also increases the amount of water to be evaporated. When human waste is subjected to humility digestion or aerobic digestion and then biological nitrification and denitrification, BOD is removed during the digestion process, resulting in a lack of organic carbon sources for denitrifying bacteria, and methanol, Since it is necessary to add expensive organic carbon sources such as ethanol and acetic acid, which brings extremely unreasonable results, in the present invention, human waste is directly subjected to biological nitrification and denitrification treatment without undergoing such a digestion treatment. do. The activated sludge slurry 3 flowing out from the biological treatment tank 2' is subjected to solid-liquid separation in a solid-liquid separation step 4 using a centrifugal concentrator, and most of the separated sludge 5 is returned to the biological treatment tank 2 as return sludge 5'. ’ will be recycled. On the other hand, the surplus (activated) sludge 6 is dehydrated by a mechanical dewatering process 7 such as a filter press or screw press, and is converted into dehydrated separated water 7' with a moisture content of 60.
The dehydrated cake 8 will be around 65%. However, the biologically treated water 9 separated in the solid-liquid separation step 4 has BOD, ammonia nitrogen components, and SS removed well, but non-biodegradable COD, chromaticity,
Large amounts of phosphoric acid and organic nitrogen remain. For this reason, in the conventional process, biologically treated water9 is subjected to coagulation sedimentation, sand filtration, ozone treatment, and activated carbon treatment.
COD, chromaticity, phosphoric acid, and organic nitrogen are removed, but in the present invention, such conventional methods are abolished, and biologically treated water 9 is heated indirectly using a vapor compression method and/or a multiple effect method. Condensed in the evaporation concentration step 10, the condensed water of the generated water vapor is converted into biologically treated water 9.
A new method will be introduced in which the nitrified biologically treated water is evaporated and concentrated using the exhaust heat of the incinerator. That is, to explain the evaporation concentration method using the vapor compression method using the illustrated example, the biologically treated water 9 is preheated and then supplied into the evaporator 10' under normal pressure conditions.
After the evaporated water vapor 11 is compressed and heated in the vapor compressor 12, it is heated to an indirect heating section 13 in the evaporator 10'.
The latent heat of condensation of water vapor is reused as a heating source for evaporation. In the indirect heating section 13, the water vapor becomes condensed water 14. Since this condensed water 14 has a temperature of about 100°C and has a large amount of heat, it is used in the heat exchanger 15 to preheat the biologically treated water 9. , and is discharged as treated water 14'. The treated water 14' is almost the same as distilled water, is colorless and transparent, has extremely low COD, BOD, phosphoric acid, and nitrogen (about 0 to 1 mg/d), and exhibits the highest quality as human waste treated water. Furthermore, this embodiment includes the following points as one of the important concepts. In other words, the heat produced by the microbial oxidation reaction generated during the biological treatment of human waste 1 (30,000 to 40,000 Kcal/Kl, the calorific value of human waste is 30,000 to 40,000 Kcal/Kl)
We focused on the effect that the temperature of the liquid in the biological treatment tank, and therefore the temperature of the biologically treated water 9, rose by 20 to 30°C over the temperature of the raw human waste 1, and the temperature was raised by the heat of microbial oxidation. One of the important points is to evaporate and concentrate the biologically treated water 9. As a result, the evaporation temperature inside the evaporator 10' (usually 100
This has the extremely important effect of reducing the amount of heat required to heat the product to temperatures up to 30°F (°C). The concentrated liquid 16 (biologically treated water 9 concentrated several tens of times) evaporated in the evaporator 10' is then evaporated in a separate evaporative drying process 17 (preferably a drum dryer). Dry and solidify 1
8 (composition is BOD component, salts such as NaCl) is incinerated in incineration step 19. Since the evaporative concentrate contains high concentrations of BOD components and color components, incineration is an essential step in the present invention. In other words, even if only salt is precipitated from the evaporative concentrate, high concentrations of COD and chromaticity components remain, so if the evaporative concentrate is disposed of as it is, or if it is simply dried and then disposed of, the COD will be reduced at the disposal site. , as it causes secondary pollution such as chromaticity elution.
It is essential to completely thermally decompose COD and chromaticity components by incineration as in the present invention. On the other hand, the residue 8' and the dehydrated cake 8 are processed in the above-mentioned incineration process 1 in which a fluidized bed incinerator equipped with an exhaust heat boiler is used.
It is naturally incinerated in step 9, and the recovered thermal energy 20 is supplied to the evaporative concentration step 10 and/or the evaporative drying step 17 for effective use. 21 is incineration residue. At the start-up of the evaporative concentration step 10 and the evaporative drying step 17, steam 26 supplied from outside the system or steam 26' from the incineration step 19 is used. In the present invention, the term "incineration" is used to mean that thermal decomposition treatment also falls within the scope of incineration treatment. In addition, if a garbage incinerator is installed adjacent to or attached to a human waste treatment plant, excess heat generated from the garbage incineration process can be used in the evaporation concentration step 10.
and/or evaporative drying step 17 is highly desirable. A method of generating electric power using a turbine or the like from the surplus heat and using the generated electric power to drive the vapor compressor 12 can also be recommended. In the present invention, the evaporation drying step 17 of the concentrated liquid 16
The following methods are particularly recommended. That is, after preheating the concentrated liquid 16, it is supplied to a closed type indirect heating evaporation dryer under normal pressure conditions, for example, a closed type drum dryer 22 as shown in the illustrated example,
The concentrated liquid 16 is attached to the surface of the rotating drum in the form of a film, the film-like liquid is evaporated to dryness by steam supplied inside the drum, and the dried substance 18 is scraped off from the drum surface with a scraper. Discharge from the hopper to the outside of the tank. On the other hand, water vapor 23 evaporated from the film-like liquid film is transferred to a vapor compressor 24.
This method involves compressing and raising the temperature in a drum, recycling it into a drum, and reusing it as a heating source for evaporative drying. In this case, since the quality of the condensed water 25 condensed inside the drum dryer 22 is also very good, it is merged with the treated water 14'. As described above, in one embodiment of the present invention, a case has been described in which the vapor compression method is adopted.However, a multiple effect evaporation method or a combined method of a multiple effect evaporation method and a vapor compression method may be used in the evaporation concentration step 10 and the evaporation drying step 17. Needless to say, it may be adopted. The evaporative drying step 17 may be of any type,
In the illustrated example, the concentrated liquid 16 is supplied to the sludge storage section 22' in which the rotating drum is immersed, but it may also be directly sprayed or allowed to flow down onto the surface of the rotating drum. In addition, concentrate 16
is not treated in the evaporation drying step 17 and is directly incinerated step 19
It may also be incinerated by spraying. Furthermore, the condensed water (highly treated human waste water) 14 flowing out from the heat exchanger 15 is still at a temperature of about 50°C and has a large amount of heat, so it is not discharged as it is, and the dehydrated cake 8 is heated. The recovered thermal energy 20 from the incineration process 19 can be increased by utilizing the air as a heating source for the ventilation drying process (not shown). Optionally, the treated water 14' may be further subjected to ultra-high-level treatment by any polishing step (eg, ion exchange, adsorption, chemical oxidation treatment, ultrafiltration treatment, etc.). In addition, in the example illustrated above, both the evaporation concentration step 10 and the evaporation drying step 17 are performed under normal pressure conditions, but in this case, the biologically treated water 9 of human waste 1 is condensed through a heating step of about 100°C. Since the water becomes treated water 14', no bacteria such as coliform bacteria remain in it. Therefore, no special sterilization process is required. Note that at least one of the above two steps may be performed not under normal pressure conditions but under reduced pressure, or the biological treatment step 2 may be a biological nitrification step or a biological denitrification step. [Effects of the Invention] According to the present invention as described above, the following many important effects can be obtained. All the steps of coagulation and sedimentation (floating), oxidation, ozone oxidation, and activated carbon adsorption of the biological treatment liquid, which were essential in the conventional process, are no longer necessary, and the treated water is of much better quality than the conventional process. can get. Therefore, it not only has a significant effect on preventing environmental pollution, but also simplifies the process. A flocculant, ozone generation power, activated carbon replenishment, and activated carbon regeneration energy are all unnecessary, resulting in significant resource and energy savings. Since no flocculation-sedimentation (or flotation) sludge is generated, the only sludge that needs to be treated is excess biological sludge, and treatment and disposal costs can be significantly reduced. Since inorganic hydroxides (Al(OH) ₃ , Fe(OH) ₃ , etc.) such as coagulated sedimentation (floating) sludge are not mixed in the dehydrated cake, the calorific value of the dehydrated cake is low.
It has excellent fuel properties at 4000 to 4500 Kcal/Kg dry matter, and easily self-combustes, so it does not require auxiliary fuel such as heavy oil. This point greatly contributes to the energy saving effect. Since human waste contains high concentrations of ammonia, organic acids, and odor components,
When human waste is directly evaporated, a large amount of ammonia, volatile organic acids, and odor components are contained in the generated water vapor and the water vapor condensed, so it is impossible to discharge the water vapor condensed as treated human waste water. Moreover, human waste contains 10,000 to 20,000
Contains a high concentration of SS per ml,
In normal evaporation operations, the SS concentration increases due to water evaporation, and the viscosity increases extremely, clogging the evaporator. Conventionally, methods have been adopted to prevent data from being lost. In contrast, in the present invention, human waste is first biologically treated to sufficiently remove ammonia, volatile organic components, and odor components, and then microorganisms such as activated sludge are separated into solid and liquid. As a result, extremely clear water quality equivalent to that of distilled water is obtained, with almost no BOD, COD, nitrogen, phosphoric acid, color components, or odor components present in the evaporated steam and its condensed water. Also,
There is no leakage of odor components from the evaporator, and there is almost no SS in the liquid to be evaporated, so it is important that it can be easily evaporated and concentrated without the need for the conventional troublesome operation of adding oil to create a fluid medium. There are advantages. The chloride ion concentration of conventional human waste water is 300~
It was difficult to use the water for irrigation in forests and fields because of the high chlorine ion concentration of 3000 mg/kg, but since the treated water of the present invention is close to distilled water, the chlorine ion concentration is only a few ppm.
It's just a matter of degree. Therefore, it can be easily used for irrigation water. Furthermore, when human waste is directly evaporated, scale-forming components such as sulfides present in human waste are removed.
Because of SS, scale adhesion on the heat transfer surface inside the evaporator is severe, but in the present invention, since the biologically treated water of human waste is evaporated, it has been experimentally confirmed that scale formation is extremely small. [Example] Human waste (containing 10% septic tank sludge) delivered to a certain human waste treatment plant in Kanagawa Prefecture was filtered using a rotary screen to remove the human waste, and the amount of human waste processed was 1Kl/
The nitrified solution was treated undiluted by biological denitrification process on a daily scale. The reason for non-dilution treatment was to reduce the amount of water flowing into the evaporation process and to raise the water temperature due to the heat of microbial reaction. As a result of the non-dilution treatment, there was severe foaming on the water surface of the nitrification tank, but this was resolved by installing a defoamer on the foam layer on the water surface of the nitrification tank. MLSS of biological nitrification and denitrification process is
20,000 mg/~23,000 mg/, and the residence time was 7 days. The water temperature in the biological treatment tank is controlled by microorganisms (BOD assimilating bacteria,
Due to the heat produced by microbial reactions (nitrifying bacteria, denitrifying bacteria, etc.), the temperature rises to 45-46℃ in summer, 33-35℃ in winter, and 37℃ in spring and autumn.
It was maintained at ~42°C. A chemical-free centrifugal thickener is used for solid-liquid separation of the biological treatment tank effluent slurry, and most of the thickened sludge (concentration 5-6%) is recycled to the denitrification tank, with a portion being discharged as surplus activated sludge. did. However, centrifugal concentrated separated water (SS300~500ml/
The remaining SS is further removed by flowing into the sedimentation tank, and the separated water containing 20 to 30 mg of SS is supplied to the vapor compression evaporator, where it is concentrated to a concentration ratio of 50 times, and the concentrated liquid is mixed with the concentrated liquid of 20 to 180 mg/day. The water vapor condensed water (highly treated human waste water) was obtained. A small-scale falling film type was used for the above-mentioned evaporator, and a Roots type was used for the vapor compressor.
The water quality of the evaporator influent and condensed water was as shown in the table below.

[Table] The concentrated liquid discharged from the evaporator is supplied to a closed type self-vapor compression type drum dryer developed by the present inventor and evaporated to dryness to produce a mixture of COD components, phosphoric acid, color components and salts. Obtained. On the other hand, ferric chloride was added to the excess sludge at 12% per SS.
After adding %, neutralize to pH4~5 with Ca(OH) ₂ ,
Next, it is dehydrated using a filter press with a squeezing mechanism, with a moisture content of 64 to 65% and a lower calorific value of approximately 4000 Kcal/Kg.
A dehydrated cake of D.S. was obtained. In addition, the residue was dehydrated using a screw press to obtain a dehydrated residue with a water content of 60 to 61%. Dehydrated cake, dehydrated residue, evaporated dry matter of the above concentrated liquid, and garbage from the treatment plant management building and nearby housing complex are self-incinerated in a fluidized bed incinerator equipped with an exhaust heat boiler, and the recovered heat is used to start up the above evaporator. It was used for normal operation, steady-state operation, and preheating of the evaporator inflow. In addition to the above-mentioned filter press, we investigated a method of dewatering surplus sludge using a screw press after adding a polymer flocculant, and as a result, a dehydrated cake with a water content of 62 to 64% was obtained, which was combined with the film press dewatering method. We obtained equally good results. According to the present invention as described above, the processing cost per 1Kl of human waste is 900 to 1000 yen,
The highest quality treated water was obtained at approximately 1/4 the cost of the conventional process.

[Brief explanation of drawings]

The drawings are flow sheets illustrating embodiments of the invention. 1... Human waste, 2... Biological treatment process, 2'... Biological treatment tank, 3... Activated sludge slurry, 4... Solid-liquid separation process,
5...separated sludge, 5'...return sludge, 6...surplus (activated)
Sludge, 7...Mechanical dewatering process, 7'...Dehydrated separated water, 8
...Dehydrated cake, 8'...Residue, 9...Biologically treated water, 1
0...evaporation concentration step, 10'...evaporator, 11, 23,
26, 26'... water vapor, 12, 24... vapor compressor,
13... Indirect heating section, 14, 25... Condensed water, 14'
... Treated water, 15 ... Heat exchanger, 16 ... Concentrate, 17
... Evaporation drying process, 18... Drying solid matter, 19... Incineration process, 20... Recovered thermal energy, 21... Incineration residue,
22...Drum dryer.

Claims (1)

[Claims] 1. Organic wastewater is subjected to biological treatment in a biological treatment process in which a biological nitrification reaction is carried out without being subjected to digestion treatment, and the biologically treated water is concentrated in an evaporation concentration process. 1. A method for treating organic wastewater, comprising treating the concentrated liquid through a post-treatment process including an incineration process. 2. The method according to claim 1, wherein the post-treatment step comprises an evaporation drying step as a first step and an incineration step as a second step. 3. The method according to claim 2, wherein the evaporation drying step evaporates the concentrated liquid to dryness. 4. The method according to claim 2, wherein at least one of the evaporative concentration step and the evaporative drying step is performed using incineration waste heat from an incineration step. 5. Claim 1 in which the steam condensed water from the evaporation concentration step is used to preheat the biologically treated water.
3. The method described in Section 2, Section 2, or Section 3. 6. The method according to claim 1, 2, 3, or 4, wherein the biological treatment step is a biological nitrification and denitrification step. 7. The method according to claim 6, wherein the biological treatment step is performed on human waste wastewater without adding dilution water thereto.