JP3410866B2 - Treatment method of human wastewater - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating night soil sewage such as night sewage and septic tank sludge, and more particularly to a method for highly purifying night sewage wastewater using a photocatalyst at low cost.

[0002]

2. Description of the Related Art The most advanced treatment method at present is to perform biological nitrification denitrification of undiluted human waste sewage undiluted and then perform membrane separation with a UF membrane or the like, and an inorganic coagulant (aluminum sulfate, second chloride (E.g. iron) to coagulate and remove phosphorus, COD, etc., further coagulate flocculated flocs with a UF membrane, and COD remaining in membrane permeated water is adsorbed on granular activated carbon to obtain highly treated water. This technology is called the membrane separation process of night soil wastewater.

[0003]

However, the conventional membrane separation process for human waste water has the following problems. 1. Low-molecular-weight COD that cannot be removed by the coagulation treatment flows into the activated carbon treatment process in a considerably large amount, and thus the running cost of activated carbon is high. 2. The activated carbon is frequently regenerated and maintenance is complicated. An object of the present invention is to solve these problems by applying a photocatalytic chemical oxidation means that has never been applied to the treatment of night soil wastewater in a novel manner.

[0004]

The above object of the present invention can be achieved by the following constitution. (1) In a method of treating human waste sewage by a step including a biological nitrification denitrification treatment, the human sewage sewage is biologically nitrified and denitrified, and then coagulated and separated by an inorganic coagulant to obtain the coagulated separation. A method for treating human waste sewage, which comprises contacting aggregated separated water with a photocatalyst under light irradiation for chemical oxidation and then adsorbing activated carbon. (2) A particulate photocatalyst is added to and suspended in the aggregated separated water, chemically oxidized while being irradiated with light, and then the photocatalyst is subjected to solid-liquid separation, and the separated water obtained by the solid-liquid separation is adsorbed on activated carbon. (1) The method for treating human waste sewage as described above.

The main points of the technical idea of the present invention are as follows. 1. After biologically nitrifying and denitrifying the human waste sewage, it is coagulated and separated by an inorganic coagulant, and a photocatalyst such as titanium oxide, cadmium oxide, and iron oxide is brought into contact with the coagulated and separated water obtained by the coagulation and separation to emit light. Irradiate and chemically oxidize. 2. The treated water that has been subjected to photocatalytic treatment and chemical oxidation is further treated with activated carbon. FIG. 1 shows an example of steps for carrying out the present invention. For the biological nitrification denitrification treatment in the present invention, a conventionally known method can be used. The biological nitrification denitrification treatment in the present invention may be carried out without diluting the human waste sewage or appropriately diluting it, but it may be carried out neat in consideration of the efficiency of the photocatalytic oxidation reaction to be carried out later. preferable. In the method of the present invention,
Prior to biological nitrification and denitrification treatment of human waste sewage, a known pretreatment or the like can be performed. A conventionally known method can be used for coagulation separation performed after the biological nitrification denitrification treatment in the present invention. As the inorganic coagulant used for the coagulation separation, a conventionally known one can be used. The aggregation and separation may be performed by any method such as precipitation after aggregation action by adding an inorganic coagulant, centrifugation, and membrane separation.

[0006]

[Function] Biological nitrification and denitrification treatment of human waste system wastewater (hereinafter,
When treated water (also simply referred to as biologically treated water) (hereinafter also simply referred to as biologically treated water) is contacted with a photocatalyst and irradiated with light, some substance in the biologically treated water significantly interferes with the chemical oxidation action of the photocatalyst, but the biologically treated water aggregates. It was found that when separated, the inhibitor of photocatalytic effect was removed and COD was effectively oxidatively decomposed. Probably the photocatalytic inhibitor in the biologically treated water is phosphate ion, a high molecular weight organic substance. (Phosphate ion and high molecular weight organic matter are removed by coagulation treatment.) After removing BOD from urine-based wastewater by a normal activated sludge method (nitrogen is not removed), the treated water that has been coagulated and separated is subjected to a photocatalytic treatment. It was confirmed that the photocatalytic oxidation reaction preferentially causes the nitrification reaction of ammonia nitrogen because a large amount of ammonia nitrogen remains in the water, and the COD removal effect is significantly reduced. From the above findings, it was found that in order to effectively carry out chemical oxidation by photocatalyst, it is important to perform photocatalytic treatment on the urine system wastewater after biological nitrogen removal and further coagulation treatment. .

Since the rate of COD removal by the photocatalytic oxidation reaction is quite low, it is preferable to provide a reaction time of one day or longer. It is naturally possible to use a UV irradiation lamp to exert the photocatalytic action, but since running costs such as electric power and UV lamp replacement are extremely high, it is necessary to treat at a low cost as much as possible and it is not very practical for urine treatment. Is preferably used. For example, the roof of a human waste treatment facility,
Alternatively, a method in which a pond is provided outdoors so that the coagulated water can be retained for a long time while irradiating sunlight to allow the photocatalytic reaction to proceed sufficiently is preferable. If the water depth of the pond is too deep, the irradiation of sunlight will be insufficient, so it is preferable to set it to about 50 cm. Of course, if the construction cost is affordable, the combination of the condenser, the optical fiber light guide, and the diffuser will not prevent the introduction of sunlight into deeper water. Further, if a large amount of diluting water is added to urine-based wastewater for biological treatment, the amount of water increases and the capacity of the photocatalytic reaction tank becomes too large to be practically practical. Therefore, ideally, undiluted biological treatment is desirable.

However, when sunlight is used, the effect of photocatalytic reaction decreases and disappears in winter, in the rain, and at night, so that stable treated water quality cannot be obtained, but the present invention has this drawback. It was solved as follows. That is, by further subjecting the photocatalyst-treated water by sunlight to adsorption of activated carbon, water with high COD is supplied to the activated carbon process in winter, rainy weather, and night, and this COD is removed by activated carbon, so that sunlight is sufficiently irradiated. During the time period, water containing almost no COD is supplied to the activated carbon process, and stable, good treated water can always be obtained. As a result, the annual average COD load on activated carbon can be greatly reduced as compared with the conventional method (method of treating coagulated water with activated carbon). As described above, the human wastewater was biologically nitrified and denitrified, and then coagulated and separated, and then the coagulated and separated water obtained by the coagulation and separation was subjected to a photocatalytic oxidation reaction and further obtained by the photocatalytic oxidation reaction. The concept of treating photocatalyst-treated water with activated carbon has never existed before.

As the shape of the photocatalyst, known ones such as fine particles, those having a photocatalyst attached to a granular carrier, and those having a photocatalyst attached to the surface of a plate-shaped or rod-shaped material can be used. When the photocatalyst is immobilized on the carrier, the surface area of the photocatalyst may be reduced and the reaction rate may be reduced. In that case, it is preferable to suspend the photocatalyst in the form of fine particles in the aggregated water for use. The suspension concentration of the particulate photocatalyst in the aggregated water is 5
It may be about 2000 to 20000 mg / l, preferably 1000
It is recommended to set it up to about 5000 mg / l. The photocatalyst fine particles are separated and collected by a filtration means such as coagulation filtration or a UF membrane and reused. Almost no deterioration of the photocatalyst over time is observed,
It is preferable that about 10% of the photocatalyst can be replenished annually in order to guarantee the catalytic ability.

[0010]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Example 1 Treated water obtained by biologically nitrifying and denitrifying human sewage undiluted (hereinafter referred to as biologically treated water) was installed (F city, Shizuoka prefecture).
Then, the test was conducted by the method of the present invention to verify the effect of the present invention. Biologically treated water (COD 530 mg / l, chromaticity 280
(1) 1500 mg / l of ferric chloride was added to 0), and treated water (COD 92 mg / l, chromaticity 120) obtained by coagulation and separation was added to titanium oxide photocatalyst powder (manufactured by Fuji Titanium Co., Ltd., particle size 0.15 to 0.3 μ).
m, having anatase type crystal type) 5000 mg / l
After adding and suspending it, it was allowed to stay in a tank with a water depth of 50 cm installed outdoors during fine weather for 2 days, and then a UF membrane (manufactured by Nitto Denko Corporation,
The titanium oxide fine particles were separated with a nominal molecular weight cutoff of 10,000). This UF membrane permeated water had a COD of 11 mg / l and a chromaticity of 8). The space velocity (S
V) 2 was passed, the column effluent was COD 3 mg /
The chromaticity was 1 and the chromaticity was 0. Next, when the same experiment was performed in rainy weather, the COD of the UF membrane permeation water after the photocatalytic treatment was 43 mg.
/ l, chromaticity 40), which did not satisfy the discharge water quality standard (COD 15 mg / l or less), but the activated carbon treated water of the UF membrane permeate had COD 8 mg / l and chromaticity 2. As a result of conducting a continuous test for 1 year (total 112 days in rainy weather) under the above conditions, the average COD of the activated carbon inflow water was 22 mg / l. The COD of the activated carbon-treated water remained below 15 mg / l even after passing through the water for 6 months, and regeneration of the activated carbon was unnecessary during this period.

[Comparative Example 1] The treated water (COD 92 mg / l) which had been coagulated and separated in Example 1 was directly treated with activated carbon (SV2) without photocatalyst treatment. The activated carbon treated water after 20 days deteriorated to COD 18 mg / l. It was necessary to regenerate the activated carbon once every 20 days. [Comparative Example 2] The biologically treated water of Example 1 (COD530
The same titanium oxide photocatalyst as used in Example 1 was directly added to 10000 mg / l, phosphorus 632 mg / l), and the mixture was allowed to stand for 2 days outdoors in fine weather and then subjected to membrane separation,
The membrane permeated water COD was 495 mg / l, and almost no COD was removed. From this, it is understood that it is important to photocatalyst-oxidize the product that has been aggregated and separated after the biological treatment.

[0012]

The following effects were obtained by performing the biological nitrification denitrification treatment, the coagulation separation with the inorganic coagulant, the photocatalytic oxidation reaction, and the activated carbon adsorption on the human waste sewage in this order. 1. The regeneration frequency of activated carbon is reduced to about 1/6. 2. When sunlight is used, the effect of the photocatalyst is greatly reduced at night and in rainy weather, but in this case as well, good treated water can always be obtained. 3. The maintenance cost is low because the ultraviolet irradiation lamp can be eliminated. 4. By coagulating and separating the biologically treated water, the substance that inhibits the photocatalyst can be removed, and the photocatalytic action can be effectively exhibited. Further, by using the photocatalyst in the form of fine particles, COD can be chemically oxidized more efficiently.

[Brief description of drawings]

FIG. 1 shows an example of steps for carrying out the present invention.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI C02F 9/00 503 C02F 9/00 503D 504 504A 504E 1/28 1/28 D 1/32 1/32 1/52 1/52 E 3/34 101 3/34 101A (56) Reference JP-A 64-75098 (JP, A) JP-A 55-44361 (JP, A) JP-A 53-16454 (JP, A) JP-A 63-214398 (JP, A) JP-A-2-172597 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 9/00 501 C02F 9/00 502 C02F 1/28 C02F 1/32 C02F 1/52 C02F 3/34 101

Claims (2)

(57) [Claims] 1. A method for treating human waste sewage by a step including a biological nitrification denitrification treatment, wherein the human sewage sewage is subjected to biological nitrification denitrification treatment, and then coagulated and separated by an inorganic coagulant. A method for treating human waste sewage, characterized in that the obtained aggregated and separated water is brought into contact with a photocatalyst under light irradiation for chemical oxidation and then activated carbon is adsorbed. 2. A particulate photocatalyst is added to and suspended in the aggregated separated water, chemically oxidized while being irradiated with light, and then the photocatalyst is subjected to solid-liquid separation, and the separated water obtained by the solid-liquid separation is adsorbed on activated carbon. The method for treating human waste sewage according to claim 1.