JPS5962391A - Treatment of organic waste water - Google Patents

Abstract

PURPOSE:To simplify considerably the titled treatment by subjecting activated sludge to a solid-liquid sepn. after biological treatment of org. waste water, aerating the separated water with gas contg. O2, evaporating and condensing the steam, and using the condensed water as the highly treated water of the above- described org. waste water. CONSTITUTION:Org. waste water 1 is biologically treated in a biological treatment stage 2, and the activated sludge slurry 3 flowing out of said stage is subjected to a solid-liquid sepn. in a solid-liquid sepn. stage 4 using a centrifugal concentrator or the like. The separated excess activated sludge 8 is fed to a sludge dehydration stage 7, where the sludge is separated to separated water 8 by the dehydration and dehydrated cake 9. The water 8 and the separated water 10 in the stage 4 are fed to an aeration tank 11 where the water is aerated by the gas contg. O2. Outflow water 12 is preheated with a heat exchanger 13 and is then fed to an evaporator 14'. Evaporated steam 15 is compressed and heated by a steam compressor 16, and is utilized as a heat source in the indirect heating section 17 of the evaporator 14' and a heat exchanger 13, by which the steam is made into highly treated water 19.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating organic wastewater such as human waste and various industrial wastewaters.

For example, a process that has been evaluated as the most advanced process in conventional human waste treatment, and which is being implemented rapidly, involves adding diluted water (approximately 10 times the amount) to human waste, performing biological nitrification and denitrification treatment, and then processing it. This method involves coagulating the water, filtering it through a sand filter, ozonating it, adsorbing it on activated carbon, and then sterilizing it.

Although this process is currently being evaluated as an excellent process, when the technology is evaluated from a strict viewpoint, the present inventor has come to realize that it inherently contains the following serious drawbacks.

In other words, ■ Many unit operations are arranged in series, making the process complex and difficult to maintain.

■ The coagulation-sedimentation or coagulation-floating process requires the addition of a large amount of inorganic flocculant, which consumes a large amount of resources and generates coagulation-sedimentation sludge that is difficult to dewater.The treatment and disposal of this sludge is a key issue and requires a large amount of expense. It takes.

The presence of broken, flocculated sludge reduces the quality of the compost product.

■ Ozone generation requires a multi-digit electric power of approximately 25 kg/cm, and activated carbon treatment requires a multi-digit electric power of approximately 500 to 60 kg/cm.
It requires a high cost of 0 yen/kl - urine.

The present inventor had strong doubts about the current state of affairs, conducted studies to develop a process capable of eliminating the above-mentioned drawbacks, and completed the present invention.

The effects of the present invention can be described as surprising; the conventional steps of coagulation and sedimentation, sand filtration, ozone treatment, activated carbon adsorption, and sterilization treatment are completely unnecessary, and the quality of treated water is significantly improved.

That is, the present invention subjects organic wastewater to biological treatment, then separates activated sludge into solid and liquid, aerates the separated water with an oxygen-containing gas and then evaporates it, and converts the condensed water of the evaporated water vapor into the organic wastewater. This is a method for treating organic wastewater characterized by treating it as treated water.

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

Removed human waste (often contaminated with septic tank sludge)
] without adding dilution water to the biological treatment process 2 using the biological nitrification-denitrification bed method (or biological nitrification method) to sufficiently remove nitrogen components such as BOD and NH3-N. . Adding a large amount of dilution water to the biological treatment step 2 is extremely preferable because it does not cause a decrease in water temperature, but rather increases the amount of water to be evaporated.

The activated sludge slurry 3 flowing out from the biological treatment process 2 is subjected to solid-liquid separation in a solid-liquid separation process 4 using a centrifugal compressor, and most of the separated sludge 5 is returned to the biological treatment process 2 as return sludge 5'. Surplus activated sludge is recycled into
The sludge is treated in a sludge dewatering step 7 such as a filter press, screen IJ, or press, and is separated into dehydrated separated water 8 and dehydrated cake 9 (water content 63 to 65).

Thus, the separated water from the solid-liquid separation step 4, that is, the biologically treated water 10 and the dehydrated separated water 8, is aerated in the aeration tank 1 with an oxygen-containing gas.

In biologically treated water 10, BOD and nitrogen components were successfully removed, but large amounts of non-biodegradable COD, IJ acid, chromaticity, and organic nitrogen remained. For this reason, in the conventional process, the biologically treated water 10 is subjected to coagulation sedimentation, sand filtration, ozone treatment, and activated carbon treatment to remove COD, chromaticity, phosphoric acid, and organic nitrogen. Do not use conventional methods that have many problems.

In other words, the outflow water from the aeration tank 11]2 is transferred to the heat exchanger]3
After preheating with VC, the evaporated water vapor 15 is supplied to the evaporator 14' in evaporation step 4 and compressed and heated by the vapor compressor 16, and then led to the indirect heating section 17 in the evaporator 14' to condense the evaporated water vapor 15. Reuse latent heat as a heating source for evaporation.

The condensed water 18 passes through the heat exchanger 13 and then becomes the highly treated water 19.

Highly treated water】9 is distilled water, so it is colorless and transparent, COD,
There are no traces of BOD, phosphoric acid, nitrogen, and SS, and the water is of the highest quality that could not be expected with conventional processes as undiluted human waste treated water.

The function of the above aeration process is very important.If this aeration process is omitted and the biologically treated water 10 is directly evaporated, condensation *
It was found that 18 had a sulfur-based malodor (dimethyl sulfide, presumed to be dimethyl sulfide).

That is, in order to remove the bad odor of the condensed water 18, we have considered a method of introducing it to a deodorizing process such as activated carbon adsorption, but the ideal solution would be to pursue a method that does not cause the condensed water 18 to have a bad odor. As a result of further consideration, we found that by sufficiently aerating the biologically treated water 10, condensed water 18
It was discovered that the odor no longer lingers. The mechanism for preventing this malodor has not yet been clarified by the present inventor.

Next, this embodiment includes the following points as a precaution. That is, the microbial oxidation heat generated when human waste 1 is biologically treated (according to the inventor's actual measurements, 30
nOO~40000 kcat/kl -'L, the calorific value of urine), the temperature of the liquid in the biological treatment tank, and therefore the temperature of the biologically treated water 10, is 20 to 30% higher than the temperature of the urine 1.
Focusing on the effect of raising the temperature by 0°C, the important concept is to evaporate and concentrate the material whose temperature has been raised by the heat of microbial oxidation. This saves external thermal energy for evaporation.

The evaporated concentrate 20 is then disposed of in an arbitrary disposal process 21 such as spray combustion or evaporation to dryness.

In the above-mentioned embodiments, the vapor compression method is adopted and the 'fC case has been explained, but it goes without saying that a multiple effect method or a combination of the vapor compression method and the multiple effect method is also effective.

The important effects of the present invention as described above are as follows.

■ The highest quality treated water can be obtained, which cannot be achieved with conventional processes, and at the same time, the process is significantly simplified.

■ Flocculants, ozone generation electricity, activated carbon, sterilizing agents, and energy for regenerating activated carbon are all eliminated.

■ Coagulated sludge (Al (OH
) 3. Since no sludge (mainly composed of Fe(OR)s) is generated, the only sludge that needs to be treated is surplus biological sludge, and the cost of sludge treatment and disposal can be significantly reduced.

■ The calorific value of the dehydrated cake is approximately 40,001 ccaj because the separated aqueous inorganic flocculated sludge is mixed into the dehydrated cake.
/Ky -D,s is high, and the water content can be easily reduced to 65 coefficients or less, so it has excellent fuel properties.

Therefore, since it self-combusts, it does not require auxiliary fuel such as heavy oil. This effect greatly contributes to energy saving.

■ The water to be evaporated is biologically treated water 1), and human waste is not directly evaporated, so there is no odor, ammonia, or volatile organic acids are scattered, and the high concentration of SS components in the urine does not occur in the evaporator. No clogging or no-flow phenomenon occurs.

■ The chloride ion concentration of conventional human waste treated water is 3 [)Om.
Since the chlorine ions in the treated water of the present invention are as high as 9/L, it is difficult to use water for irrigation in the mountains and fields due to salt damage. Therefore, water can be easily reused for irrigation.

Furthermore, if human waste is directly evaporated, there is a high possibility that the evaporator will be corroded due to the sulfides and organic acids present in the human waste, but the present invention removes sulfides and organic acids through biological treatment. Q) The problem will be resolved.

Next, examples of the present invention will be described.

Example: Human waste transported to the Kanagawa Moito human waste treatment plant (septic tank sludge 1)
After decontamination of the waste (contaminated with water) using a Rotarysk 1)-on, it was treated without dilution using a biological nitrification and denitrification process using a C petrochemical fluid circulation system with a processing amount of 1 kl/day of human waste. MLSS1418 (100-20
°C) OnIn9/l, residence time was 7 days. The water temperature in the biological treatment tank ranged from 3 to 42 degrees Celsius due to heat of microbial oxidation.

A chemical-free centrifugal concentrator (Tomoe Kogyo products) is used for solid-liquid separation of the biological treatment tank effluent slurry, and most of the thickened sludge (concentration 5 to 6 cm) is passed through the denitrification tank FCIJ wheel, and some was supplied to the dewatering process as surplus sludge.

The dehydrator uses a fully automatic filterless system.

The moisture content of the dehydrated cake was 63 to 64 tI), the cake calorific value was about 4 Q OO1<cat/Ky -n,s, and it easily self-combusted in a fluidized bed incinerator.

Therefore, centrifugal concentrated separation water (SS1oo~) 20 +
After aerating the I19/l) for 12 hours, it was fed into a vapor compression evaporator rC and concentrated to 50 times the 1iJl ratio.
t/day of steamed gravel condensate and 1,804 tons/day of steam condensed water (this is highly treated water of human waste) were obtained.

The quality of declarified human waste, biologically nitrified and denitrified untreated water (biologically treated water), and condensed water (highly treated water) was as shown in the following table.

*Based on the 6-level odor intensity display method.

On the other hand, when centrifugally concentrated separated water was directly evaporated without aeration, the odor intensity of the condensed water was 3, which was greater than the odor intensity of biologically treated water.

The evaporative concentrate was sprayed into a sludge fluidized bed incinerator and disposed of by combustion.

[Brief explanation of drawings]

The drawings are flow sheets illustrating embodiments of the invention. 1... Human waste, 2... Biological treatment process, 3... Activated sludge sludge IJ-24... Solid-liquid separation process, 5 pile separation sludge,
5'... Returned sludge, 6... Excess activated sludge, 7...
Sludge dewatering process, 8... Dehydrated separated water, 9... Dehydrated cake, 1o... Biological treatment water, 11... Aeration tank, 12.
... Effluent water, 13... Heat exchanger, 14... Evaporation process, 14'... Evaporator, 15... Evaporated water vapor, 16.
... vapor compressor, ]7 ... indirect heating section, 18 ... condensed water, 19 ... highly treated water, 2o ... evaporation concentrate,
2]...Disposal process. Patent applicant: Patent attorney representing Ebara Infilco Co., Ltd.
Go Hayama - Patent attorney Sen 1) Minoru

Claims (1)

[Claims] 1. After biologically treating organic wastewater, the activated sludge has a solid-liquid content of 1i7 tp L, the separated water is aerated with an oxygen-containing gas, and then evaporated, and the condensed water of the evaporated water vapor is・Advanced treatment of organic wastewater A method for treating organic wastewater characterized by carrying out water treatment. 2. The method according to claim 1, wherein the biological treatment step is a biological nitrification step. 6. The method according to claim 1, wherein the biological treatment step is biological nitrification and denitrification treatment. 4. Claim 1, wherein the biological treatment process treats human waste water as the organic wastewater, and is performed frequently by adding dilution water to the organic wastewater.
The method described in paragraph 2 or 3. 5. The method according to claim 1, 2, 3 or I'i 4, wherein the evaporation step is performed by a vapor compression method. 6. A method according to claim 1, 2, 3 or 4, wherein the evaporation step is by a multiple effect method. Z. The method according to claim 1, 2, 3 or 4, wherein the evaporation step is a combination of a vapor compression method and a multiple effect method.