JPH0310395B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating human waste, and in particular to a method for treating human waste, which involves mixing raw human waste with returned sludge, subjecting it to anaerobic treatment, performing aerobic treatment, solid-liquid separation, and returning a portion of the separated activated sludge. It is. Generally, a method for treating sewage containing organic matter and phosphorus is to mix raw water with returned sludge, perform anaerobic treatment, then perform aerobic treatment, separate the mixed liquid into solid and liquid, and return a portion of the activated sludge. It is being said. In this method, activated sludge is placed in an anaerobic-aerobic environment repeatedly to cause excess phosphorus intake and release, effectively removing organic matter and phosphorus. It is applied to the treatment of water containing phosphorus. However, when raw human waste is treated in the same way, activated sludge maintains its organic matter absorption activity;
There were problems in that the ability to take in excess phosphorus may be lost, and the phosphorus removal rate decreases, making it impossible to lower the phosphorus concentration in the treated water. This invention is intended to solve the above-mentioned problems, and aims to improve the BOD and
The object of the present invention is to provide a method for treating human waste that can maintain a high phosphorus over-uptake capacity of activated sludge and increase the phosphorus removal rate by controlling the MLSS ratio to a predetermined value or less. This invention is a method in which raw human waste is mixed with return sludge, subjected to anaerobic treatment, then aerobic treatment is performed, solid-liquid separation is performed, and a portion of the separated activated sludge is returned. 0.025
This is a method for processing human waste characterized by the following. When we investigated the cause of the decreased ability of activated sludge to absorb excessive amounts of phosphorus when raw human waste is treated using anaerobic and aerobic treatments, we found that the
It was found that lower fatty acids, which are BOD components, were the cause. Lower fatty acids are components of soluble BOD, and in the case of sewage, they account for less than 10% of the BOD and have little effect, but in the case of raw human urine, lower fatty acids account for approximately 50% of the total BOD, and this is a component of soluble BOD. It accounts for the main part of the organic matter absorbed into activated sludge during treatment, and has a major impact on the properties of activated sludge. It is not clear why activated sludge loses its ability to take in excess phosphorus when it absorbs a large amount of lower fatty acids during anaerobic treatment, but the BOD/
By setting the MLSS ratio to 0.025 or less, the activated sludge's ability to excessively uptake phosphorus is maintained. In the present invention, the raw human waste to be treated refers to human waste itself excreted from households, etc., but SS
Pretreatment such as preliminary aeration to the extent of removal or stirring is possible, and in general, the target is human waste that has been removed with a screen or the like. In the treatment, the BOD is suitable for treatment with activated sludge and can be diluted with fresh water, seawater, etc. so that the BOD/MLSS ratio falls within the above range. The present invention will be explained below with reference to the drawings. 1 to 3 are system diagrams showing embodiments of the present invention, respectively, in which 1 is an anaerobic tank, 2 is an aerobic tank, 3 is a solid-liquid separation tank, and 4 is a denitrification tank. In the treatment method shown in FIG. 1, human waste 5, dilution water 6, and return sludge 7 are introduced into an anaerobic tank 1 and mixed to perform anaerobic treatment. Here, BOD in anaerobic tank 1/
Raw human urine 5, so that the MLSS ratio is 0.025 or less,
The amounts of dilution water 6 and return sludge 7 are controlled. The BOD/MLSS ratio in anaerobic tank 1 is calculated using the following formula. Raw human waste BOD (mg/) × raw human waste flow rate (/hr) / anaerobic tank MLSS (mg/) × [raw human waste flow rate + dilution water flow rate + return sludge flow rate (/hr)]……() The formula is anaerobic tank This is the formula for introducing human waste, dilution water, and return sludge into anaerobic tank 2.
In the case of a treatment method that introduces a mixed liquid from In the anaerobic treatment, the liquid in the anaerobic tank 1 is kept under anaerobic conditions for about 10 minutes to 4 hours while being gently stirred. Through anaerobic treatment, activated sludge uses energy from hydrolysis of polyphosphoric acid stored in the body to absorb BOD in human urine and release orthophosphoric acid. A portion of the mixed liquid in the anaerobic tank 1 is taken out and introduced into the aerobic tank 2 for aerobic treatment. The aerobic treatment is performed by blowing air into the aerobic tank 2 and carrying out aeration treatment for about 30 minutes to 5 hours. When aerobic treatment is performed, activated sludge oxidizes and decomposes BOD absorbed during anaerobic treatment and BOD in the liquid through respiration, and also takes in phosphorus into the body and stores it in the form of polyphosphoric acid. This phosphorus intake stores polyphosphoric acid as an energy source in preparation for an anaerobic environment.
By repeating anaerobic-aerobic environmental changes,
Activated sludge becomes overloaded with phosphorus. In the aerobic tank 2, nitrification and denitrification may be performed in the same tank by controlling DO. In this way, through aerobic treatment, BOD in the mixed liquid is decomposed and phosphorus is absorbed into the activated sludge. When separated, it is separated into treated water 8 from which organic matter, phosphorus, etc. have been removed, and activated sludge 9 which has stored a large amount of phosphorus. A part of the activated sludge 9 is returned to the anaerobic tank 1 as return sludge 7,
The remainder is discharged as surplus sludge 10. In this treatment method, BOD/
When the MLSS ratio exceeds 0.025, the excess phosphorus uptake capacity in activated sludge aerobic tank 2 decreases, but as long as the above ratio is maintained below 0.025, the excess phosphorus uptake capacity is maintained high and the phosphorus removal rate increases. get high,
The phosphorus concentration in treated water can be lowered. The treatment methods shown in Figures 2 and 3 are methods that perform denitrification in addition to removing organic matter and phosphorus; anaerobic treatment is the same as in Figure 1, but nitrification treatment is performed as aerobic treatment. be exposed. In the treatment method shown in Figure 2, the aerobic tank 2 is provided for nitrification treatment, and the aerobic tank 2 is aerated in excess of the aeration for BOD removal to make nitrifying bacteria predominant and reduce nitrogen components in the mixed solution. It is now nitrified to nitrate or nitrite ions. The denitrification tank 4 has the same anaerobic structure as the anaerobic tank 1, and the mixed liquid that has undergone anaerobic treatment in the anaerobic tank 1 and the return liquid 11 that has been nitrified in the aerobic tank 2 are introduced to remove activated bacteria containing denitrifying bacteria. Mix with sludge and stir to perform denitrification treatment. Here, denitrifying bacteria that reduce nitric acid or nitrite ions in the returned liquid 11 to nitrogen using BOD in the mixed liquid as a hydrogen donor become dominant, and the nitrogen component in the human waste is removed. The dephosphorization mechanism in this treatment method is almost the same as that in Figure 1, and the BOD/
After performing anaerobic treatment with an MLSS ratio of 0.025 or less, aerobic treatment (nitrification treatment) is performed in aerobic tank 2 to store phosphorus in activated sludge. The nitrification and denitrification treatments that are performed in parallel with this are performed independently of the removal of phosphorus. A part of the mixed liquid subjected to the nitrification treatment in the aerobic tank 2 is introduced into the final denitrification tank 4a, and an organic substance 12 such as methanol is supplied from the outside as a hydrogen donor.
The final denitrification treatment is performed in the same manner as in the denitrification tank 4. The mixed liquid in the denitrification tank 4 is re-aerated in the final aerobic tank 2a to remove residual organic matter. Other operations are the same as in the case of FIG. The treatment method shown in Figure 2 can remove nitrogen components in addition to the removal of organic matter and phosphorus in the method shown in Figure 1;
Almost the same processing as in the case shown in the figure is performed. In the treatment method shown in FIG. 3, in addition to the treatment method shown in FIG. 2, an intermediate denitrification tank 4b and an intermediate aerobic tank 2b are provided to repeat the denitrification and nitrification treatments, and the return liquid 11 is sent from the intermediate denitrification tank 4b. In addition to being returned to the first-stage denitrification tank 4, the mixed liquid subjected to anaerobic treatment in the anaerobic tank 1 is distributed to the denitrification tank 4 and intermediate denitrification tank 4b. In this treatment method as well, the anaerobic treatment is carried out in the anaerobic tank 1 as in the case of Figures 1 and 2.
Perform with a BOD/MLSS ratio of 0.025 or less. By repeating denitrification and nitrification in the denitrification tank 4, aerobic tank 2, intermediate denitrification tank 4b, and intermediate aerobic tank 2b,
Nitrogen removal rate increases. If the intermediate denitrification tank 4b and the intermediate aerobic tank 2b are repeated in more stages, the nitrogen removal rate will further increase. Other operations are the same as in the case of FIG. Phosphorus removal in this treatment method is also performed in the same manner as in FIGS. 1 and 2, and is not affected by denitrification or nitrification treatment. Therefore, almost the same processing is performed. Although phosphorus may be released, it is taken up again in the aerobic tanks 2, 2b, and 2a, and finally treated water with a low phosphorus concentration is obtained. In addition, the processing method can be changed in various ways,
In either case, it is necessary to perform anaerobic treatment at a BOD/MLSS ratio of 0.025 or less, then perform aerobic treatment, and then return a portion of the solid-liquid separated activated sludge to anaerobic treatment. The following methods can be used to reduce the BOD/MLSS ratio to 0.025 or less in anaerobic treatment. Add dilution water. Increase MLSS concentration. Increase return sludge flow rate. Return the mixed liquid from the aerobic tank or denitrification tank. A portion of the raw human waste is put into a denitrification tank or an aerobic tank. In addition to this, appropriate means can be adopted depending on each processing method. According to the present invention, in the method of mixing raw human waste with returned sludge and treating it anaerobically, then treating it aerobically,
Since anaerobic treatment is performed while maintaining the BOD/MLSS ratio below a predetermined value, it is possible to maintain the lower fatty acid concentration during anaerobic treatment below a predetermined value, thereby reducing the excess phosphorus uptake ability of activated sludge. This can increase the removal rate and lower the phosphorus concentration in the treated water. Example Human waste was treated according to the treatment method shown in FIG. First, after diluting the raw human urine, anaerobic tank 1 (1.2)
It is mixed with returned sludge for anaerobic treatment, mixed with circulating nitrification mixture in denitrification tank 4 (3.5) for denitrification treatment, nitrification treatment in aerobic tank 2 (7), and part of the nitrification mixture is The remaining part is circulated to the denitrification tank 4, and the remaining part is denitrified in the final denitrification tank 4a (3.5) by injecting 1.0 g of acetic acid/day, and then the final aerobic tank 2a (2).
After reaeration treatment in the solid-liquid separation tank 3, the treated water and precipitated sludge are separated, and a part of the precipitated sludge is transferred to the anaerobic tank 1.
and the remainder was discharged as surplus sludge. Table 1 shows the treatment conditions for the method of the present invention and the control method, and Table 2 shows the quality of the treated water.

【table】

[Table] As a result of the above, the method of the present invention can be
Phosphorus removal was carried out successfully for several months. In the control method, phosphorus removal was performed well for about one month after the start of treatment, but after that, the condition worsened and did not recover. The water quality treated by the control method in Table 2 shows the water quality in a stable state after one month.
In addition, the results of the control method in Table 2 show the results of treatment at a lower dilution rate than the method of the present invention;
Even when converted so that the dilution ratio is the same,
The phosphorus concentration of the present invention is lower than that of the control method. From the above results, it can be seen that the method of the present invention exhibits a far superior phosphorus removal rate than the control method.

[Brief explanation of drawings]

1 to 3 are system diagrams showing embodiments of the present invention, respectively. In each figure, the same reference numerals indicate the same or corresponding parts, 1 is an anaerobic tank, 2, 2a, 2b are aerobic tanks, 3 is a solid-liquid separation tank, and 4, 4a, 4b are denitrification tanks.

Claims (1)

[Claims] 1. A method in which human waste is mixed with returned sludge and subjected to anaerobic treatment, then aerobic treatment is performed, solid-liquid separation is performed, and a part of the separated activated sludge is returned, the BOD in the anaerobic treatment is /MLSS ratio is 0.025 or less. 2. The human waste treatment method according to claim 1, wherein the aerobic treatment is an aeration treatment for decomposing organic matter. 3. The method for treating human waste according to claim 1, wherein the aerobic treatment is a nitrification treatment for decomposing organic matter and nitrifying nitrogen components, and the nitrified liquid is subjected to a denitrification treatment. 4. The human waste treatment method according to claim 3, wherein the denitrification treatment is provided between the anaerobic treatment and the nitrification treatment, and the nitrified liquid is returned. 5. The human waste treatment method according to claim 3 or 4, wherein the nitrification treatment and the denitrification treatment are repeated in multiple stages.