JPH0114837B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an innovative method that can treat organic waste liquids, particularly concentrated organic waste liquids such as human waste, to an extremely high degree in resource and energy savings through an extremely simple process. The details of the present invention will be explained below using human waste as a typical waste liquid. Among the conventional human waste treatment processes, the low-dilution two-stage activated sludge process is highly regarded as the most rational process and is being implemented rapidly. This process involves adding approximately 10 times the volume of dilution water to human waste to perform biological nitrification and denitrification treatment, then solid-liquid separation of the activated sludge in a settling tank, coagulation sedimentation and sand filtration of the supernatant water, and ozone-treated activated carbon. This process involves mechanically dewatering, drying, and incinerating surplus activated sludge and coagulated and precipitated sludge (hereinafter referred to as the conventional process). However, when this conventional process was technically evaluated from a strict viewpoint, the present inventors came to realize that it essentially contained the following serious problems. That is, the process is complicated because many unit operations are arranged in series, and maintenance is also poor. The coagulation and precipitation process requires large amounts of flocculants such as sulfuric acid and polymers. Therefore, in addition to being resource-intensive, a large amount of coagulated and settled sludge, which is difficult to dewater, is generated. For ozone treatment, 20kw of power is required for ozone generation.
A _large amount of activated carbon (600 yen/Kg/activated carbon) is required for activated carbon treatment. Furthermore, recycling activated carbon requires a large amount of cost (300 to 350 yen/Kg/activated carbon). Mechanical dewatering of excess activated sludge and flocculated sludge requires large amounts of dewatering aids such as cationic polymers, ferric chloride, and slaked lime, and the moisture content of the dehydrated cake is as high as 75-82%, making it difficult to dry. A large amount of auxiliary fuel such as heavy oil is used in the incineration process (200
~300/ton-D・S). Although all of these problems are extremely serious, in the past, it has tended to be recognized that advanced treatment of human waste is an inevitable necessity in order to prevent pollution of the aquatic environment. Ta. The present invention completely breaks through such conventional fixed concepts and provides a process that can successfully solve the above-mentioned drawbacks. The effects of the present invention are surprising, and the conventional processes of coagulation sedimentation, sand filtration, ozone treatment, activated carbon treatment, sterilization treatment, mechanical sludge dewatering process, and addition of dehydration aids are all unnecessary. Moreover, the quality of the treated water is overwhelmingly superior to that of conventional processes, and maintenance costs can be significantly reduced. That is, in the present invention, after organic waste liquid is subjected to biological treatment, oil is added to and mixed with a mixed slurry of the treated liquid from the biological treatment process and excess biological sludge, and then the mixture is allowed to flow into an evaporation process using at least a vapor compression method. This is a method for treating organic waste liquid, characterized in that water vapor condensation is used as highly treated water of the organic waste liquid. The technical gist of the present invention is to biologically treat an organic waste liquid and then vapor-compress and evaporate a specific object, a mixed slurry of the biologically treated liquid and surplus biological sludge. A method in which waste liquid is directly evaporated without biological treatment does not provide any of the excellent effects of the present invention, as will be described later. Next, one embodiment of the present invention will be described with reference to the drawings, taking human waste treatment as an example. The sludge-removed human waste 1 (which is often mixed with 10 to 30% septic tank sludge) is allowed to flow into the biological treatment process 2, such as the biological nitrification and denitrification process, without adding dilution water to the BOD. Biologically removes nitrogen and odor components. In addition, biological treatment process 2
In the case of human waste, the biological nitrification denitrification process or the biological nitrification process is optimal, but when the target is organic wastewater that does not contain much ammonia nitrogen components, an activity that only removes BOD is recommended. The sludge treatment process is sufficient. Activated sludge slurry (Mixed liquor) 3 flowing out from the biological treatment process 2 is separated into thickened sludge 5 and separated water 5' in a solid-liquid separation process 4 such as a centrifugal thickener, and the thickened sludge 5 is recycled to the biological treatment process 2. Ru. On the other hand, a slurry 6 containing excess activated sludge is mixed with the separated water 5' to form a mixed slurry 7. Although the BOD and nitrogen components in human waste have been removed in the biological treatment step 2, this mixed slurry 7 contains non-biodegradable color components and non-biodegradable COD.
Ingredients: MLSS5500-7000 containing a large amount of phosphoric acid
mg/slurry. Oil 8 such as heavy oil is added to this mixed slurry 7 and thoroughly mixed in a mixing tank 9 before flowing into a vapor compression evaporation step 10 (10' is an evaporator). In addition, in biological treatment step 2, human waste is treated without dilution, so the oxidation reaction generated heat (30,000 to 40,000 Kcal/
The temperature of the liquid in biological treatment process 2 is 40
℃ or higher, and the water temperature of the slurry 7 flowing into the evaporation step 10 also becomes 40℃ or higher.As a result, the pressure inside the evaporator is set to approximately normal pressure so that the temperature inside the evaporator 10' (usually 100℃) is reached. ), which has the extremely important effect of reducing the amount of heat required to heat the product to . This fact means a novel technical concept of indirectly utilizing the heat produced by the microbial oxidation reaction in the evaporation step 10. Therefore, the oil suspension slurry 11 is transferred to the heat exchanger 12.
After being preheated to a temperature of 80 to 85°C by steam condensed water 13 (this corresponds to the highly treated water of the removed human waste 1), it flows into the evaporation step 10, where it is evaporated and concentrated. It is discharged as a cloudy concentrated slurry 14. On the other hand, water vapor 15 evaporated in the evaporation step 10
After being compressed and heated in the vapor compressor 16, it flows into the indirect heating section 17 of the evaporation step 10 and is reused as a heating source. The water vapor condensed in the indirect heating section 17 becomes condensed water 13 and passes through the heat exchanger 12, after which a small amount of low boiling point oil mixed in the condensed water 13 is removed through an oil removal process (flotation separation, coalescer, etc.) 18. The water is removed and discharged as ultra-highly treated water 19. Treated water 19 is colorless and transparent, almost the same as distilled water, contains almost no COD, BOD, nitrogen, or phosphoric acid, and has been sterilized at high temperature, showing the highest quality of human waste water. In addition, as the evaporation step 10, in addition to the vapor compression method alone, a combination method of the vapor compression method and the multiple effect method can of course be adopted. In this way, the water in the oil suspension concentrated slurry 14 is removed by evaporation, and the amount of water in the mixed slurry 7 is reduced to approximately 1/1.
40 or less, the sludge is further led to a separate evaporator 20' to evaporate the water, and the sludge suspended in the oil is dried (this step is called the evaporation drying step of the oil suspended concentrated slurry 14). 20). Next, the oil-containing dried sludge 21 is made to flow into a deoiling process 22 such as a screw press or a centrifugal separator to separate and recover oil, and the recovered oil 23 and oil removal process 18
The recovered oil 23' is recycled to the mixing tank 9 and reused. It should be noted that if the amount of water evaporated in the evaporation step 10 is further increased, the amount of water in the oil suspension concentrated slurry 14 will further decrease.
0 is no longer necessary, and the oil suspension concentrated slurry 14 can be supplied to the deoiling step 22 all at once. In this case, the steam 26 generated from the boiler 25 is supplied to the indirect heating section 20'' of the evaporation drying process 20. Therefore, the deoiled sludge 24 discharged from the deoiling process 22 contains A trace amount of oil that could not be separated in step 22 remains (150-180-
oil/ton-D・S), and is a low-moisture sludge with a water content of about 10%, so the calorific value is approximately 4000Kca.
It has high l/Kg-D・S and has extremely excellent fuel properties. Therefore, it can be used as fuel for the boiler 25. The steam 26 generated in the boiler 25 is mainly used as a heating source for the evaporation drying process 20, and is also used for starting the evaporation process 10, deoiling process 22, etc. In the figure, 27 is combustion air, 28 is exhaust gas, and 29 is incineration residue. In addition, the water vapor 3 evaporated from the evaporation drying step 20
0 is preferably introduced into the suction side of the vapor compressor 16 in order to effectively utilize the heat. It goes without saying that the evaporative drying step 20 may be performed by a multiple effect method and/or a vapor compression method, if desired. Furthermore, it is preferable to co-fire the sludge 31 discharged from the sludge removal process in the boiler 25, which increases the amount of steam 26 generated. Note that 8' is a make-up oil for replenishing an amount equivalent to the oil adhering to the deoiled sludge 24 from outside the system. According to the present invention described in detail above, the following remarkable effects can be obtained, and the serious drawbacks of the conventional process can be completely solved. All of the steps that are essential in conventional processes, such as coagulation and sedimentation, sand filtration, ozonation, activated carbon adsorption, and sterilization, are no longer necessary, and moreover, it is possible to obtain the highest quality, ultra-highly treated water that could not be expected with conventional processes. Therefore, a remarkable effect is obtained in terms of preventing environmental pollution, and the process is also extremely simplified. Additionally, coagulants, ozone generation electricity, and activated carbon are all eliminated, resulting in significant resource savings. In addition, the process of mechanical dewatering of surplus activated sludge and coagulated sedimentation sludge, which is essential in conventional processes, is no longer necessary, and at the same time, no dewatering aids are required at all, resulting in significant resource saving and process rationalization effects. There is no coagulation and sedimentation of sludge, which is a problem in conventional processes. In the conventionally known method of direct multi-effect evaporation treatment of human waste without biological treatment, (a) human waste contains a large amount of ammonia, volatile organic components, and odor components; A large amount (several 1000 mg/) in the condensed water of
Since the condensed water contains ammonia, BOD, and odor components, it is completely impossible to discharge the condensed water as an advanced treatment as in the present invention. (b) Furthermore, careful measures must be taken to prevent odor from leaking from the evaporation process, and scale formation is likely to occur due to sulfides in human waste. However, since corrosive components (H ₂ S, organic acids, etc.) are included in the evaporated water vapor, the possibility of corrosion inside the vapor compressor is extremely large, making it difficult to apply the vapor compression method. (c) In addition, when attempting to perform biological nitrification and denitrification treatment on condensed water to remove ammonia and BOD components in condensed water, SS in human waste
Since all the BOD and phosphoric acid are transferred to the concentrated liquid during the evaporation process, the N/N of the condensed water is
The BOD ratio increases, and efficient biological denitrification cannot be performed unless a large amount of hydrogen donors (organic carbon sources) such as methanol and acetic acid, which are valuable substances, and phosphoric acid are added from the outside. On the other hand, in the present invention, human waste is sufficiently biologically treated in advance and then vapor compression evaporation treatment is applied to a specific target, a mixed slurry of the treated liquid and surplus activated sludge, so the above-mentioned drawbacks do not occur at all. do not. This is because ammonia nitrogen, BOD components such as volatile organic components, odor components, and scale-forming and corrosive components such as sulfides are sufficiently removed biologically in advance before feeding to the vapor compression evaporation process. With this structure, BOD, ammonia, odor components, and volatile organic acids in evaporated steam and condensed water are almost zero, and in the biological nitrification and denitrification process, phosphoric acid in human waste,
Since the SS BOD component can be fully utilized, the addition of phosphoric acid, methanol, and acetic acid is completely unnecessary. In the conventional process, surplus activated sludge and flocculation-sediment sludge (both are well-known as difficult-to-dewater sludge)
However, since dehydration aids such as cationic polymers are added and dehydrated using a dehydrator such as a belt press, the cost of dehydration aids is high at about 300 yen/Kl - human waste, and the water content is 80%. A large amount of auxiliary fuel is required to dry and incinerate the dehydrated cake (approximately 800 to 900 yen/Kl). In addition, since inorganic substances such as aluminum hydroxide caused by coagulated and settled sludge coexist in the dehydrated cake, the negative point that the calorific value of the dehydrated cake is small cannot be overlooked. In contrast, the present invention completely eliminates the need for a dehydrator and the step of adding a dehydration aid, so the above-mentioned drawbacks are successfully solved. Therefore, no auxiliary fuel is required for sludge incineration;
Conversely, the sludge itself can be used as fuel for boilers. Human waste water treated with conventional processes has a high chloride ion concentration of 500 to 3000 mg/mt, so it is
Although it is difficult to use water for irrigation in fields due to salt damage, since the water treated by the present invention is distilled water, the salt concentration is extremely small, ranging from zero to trace. Therefore, it can be easily and effectively used as irrigation water. Since the treated water according to the present invention is clear hot water, it can be effectively used for heating in treatment facilities, hot water pools at welfare centers, etc., and for bathing.
An even more energy-saving process is realized. Next, examples of the present invention will be described. Example: Raw human waste (containing 5-8% septic tank sludge) delivered to the human waste treatment plant in Zushi City, Kanagawa Prefecture is removed using a rotary screen, and then nitrified fluid circulation biology is applied at a processing rate of 10Kl/day. It was treated without dilution using a standard denitrification process. Addition of dilution water is undesirable because it increases the amount of water to be subjected to vapor compression evaporation treatment and lowers the liquid temperature, so non-dilution treatment was performed. A defoaming machine was installed to prevent foaming in the nitrification tank. MLVSS of biological denitrification process is 20000-21000
mg/, and the residence time was set to 5 to 7 days. Due to the heat produced by the oxidation reaction when microorganisms carry out the BOD removal reaction and nitrification reaction, the liquid temperature in the biological treatment tank is 40-45℃ in summer and 33-33℃ in winter.
The temperature was maintained at 35°C, and the temperature rose more than 20°C compared to the inflowing urine. Next, most of the biological treatment process effluent slurry is supplied to a chemical-free centrifugal concentrator (super decanter type used), and separated liquid and thickened sludge (solids concentration 5-6
%) and the thickened sludge was recycled to the biological treatment process. Next, a part of the biological treatment process effluent slurry is mixed with the centrifugal concentrated separation liquid to prepare a mixed slurry with a concentration of 6000 to 7000 mg MLSS, which corresponds to the amount of excess activated sludge generated, and heavy oil A is added to this for 1 kg of solids in the mixed slurry. Add 10Kg per mix, temperature 100
After preheating to a temperature of about 80℃ by exchanging heat with condensed water at ℃, it is supplied to a plate-type vapor compression evaporator (corresponding to code 10' on the flow sheet, heat transfer area 27m ² ), increasing the temperature by 40 to 50 times. It was concentrated by evaporation. No scale or corrosion was observed inside the evaporator because the heat transfer surface was protected by the oil film. The evaporated steam is compressed to 1.4Kgf/cm ² by a vapor compressor and raised in temperature, and then used again as a heating source for the evaporator.The condensed water of the steam is then used in the oil removal process using an inclined plate flotation type oil separator and a coalescer. Through this process, undiluted high-level treated human waste water having the water quality shown in the table below was obtained.

[Table] This treated water quality is of an extremely high quality that cannot be achieved by conventional undiluted treatment of human waste. However, the moisture content flowing out from the steam canister is 75~
80% oil suspension concentrated slurry (flow rate 400-500/
) was introduced into an evaporative drying tank (corresponding to 20' on the flow sheet) to obtain an oil-suspended dried sludge with a water content of 10 to 15%. The oil is extracted using a screw press, and the separated oil is recycled to an oil mixing tank.
D・S) was supplied to the boiler and used as fuel. The sludge discharged from the screw press had a high lower calorific value (3500 to 3900 Kcal/Kg・cake), so it easily combusted. In addition, the residue generated from the human waste removal process was dehydrated using a screw press (manufactured by Shoda Kikai Co., Ltd.), and the dehydrated residue with a water content of 60 to 63% was co-fired in the boiler. Steam generated from the boiler at a pressure of 2 Kgf/cm ² , a temperature of 133° C., and an amount of steam of 4700 Kg/day was supplied to the evaporative drying vessel and used for evaporative drying of the oil suspension concentrated slurry. As described above, the process of the present invention does not require alcohol for biological denitrification, flocculants for coagulation and sedimentation, ozone, activated carbon, and dehydration aids for sludge dewatering, which are required in conventional processes. What is required is A heavy oil to be supplied to the evaporation process 10' (addition amount 80 to 90/day, 0.8 to 1.0 per Kl of human waste,
The cost was only 60-80 yen/Kl). In addition, the power required for the evaporation process 10' is 20~20~1Kl of human waste.
It is extremely cheap at 22Kwh and costs 400 to 440 yen/Kl, and the electricity cost for the entire electrical equipment such as various pumps and aeration blowers is 1100 yen/Kl, total.
The cost was 1,560 to 1,620 yen/Kl - human waste, which was a significant reduction compared to the actual maintenance and management cost of the conventional process, which was 3,500 to 4,000 yen/Kl.

[Brief explanation of drawings]

The drawings are flow sheets illustrating embodiments of the invention. 1... Residue human waste, 2... Biological treatment process, 3... Activated sludge slurry, 4... Solid-liquid separation process, 5... Thickened sludge,
5'...separated water, 6...slurry, 7...mixed slurry,
8,8′...Oil, 9...Mixing tank, 10...Evaporation process, 1
0″, 20′...Evaporator, 11′...Oil suspension slurry,
12... Heat exchanger, 13... Condensed water, 14... Oil suspension concentrated slurry, 15, 26, 30... Steam, 16...
Vapor compressor, 17, 20″...Indirect heating section, 18...
Oil removal process, 19... Treated water, 20... Evaporation drying process, 21... Oil-containing dried sludge, 22... Oil removal process, 2
3, 23'...Recovered oil, 24...Deoiled sludge, 25...Boiler, 27...Combustion air, 28...Exhaust gas, 29
...Incineration residue, 31...Residue.

Claims (1)

[Claims] 1. After treating organic waste liquid in a biological treatment process,
A method for treating organic waste liquid, which comprises adding and mixing oil to a mixed slurry of the biological treatment liquid and excess sludge, and evaporating the mixture in at least an evaporation step using a vapor compression method. 2. The method according to claim 1, wherein the biological treatment step is a biological nitrification step. 3. The method according to claim 1, wherein the biological treatment step is a biological nitrification and denitrification step. 4. The evaporation step includes an evaporation step using the vapor compression method for removing and concentrating a part of the water in the mixed slurry, and removing and drying the water remaining in the thickened sludge from the evaporation step. Claim 1 consists of an evaporative drying step for
3. The method described in Section 2, Section 2, or Section 3. 5. At least one of the evaporation step using the vapor compression method and the evaporation drying step uses steam obtained by deoiling the dried sludge from the evaporation drying step and then incinerating it in a boiler as a heat source for heating. 5. The method according to claim 4, wherein the method is carried out.