JPH0565238B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for treating septic tank sludge. [Prior art] Conventionally, treatment of septic tank sludge is different from ordinary wastewater treatment methods, and the method is to perform pre-aeration if necessary, then perform solid-liquid separation, dewater the separated sludge, and treat the separated liquid with activated sludge. It had become mainstream. However, since the activated sludge treatment method requires a large-scale facility and is complicated to operate, a biological treatment method using a packed bed of granular media has been considered as a method for treating the separated liquid. [Problems to be Solved by the Invention] By the way, treating the separated liquid with a biological treatment method using a packed bed of granular media as described above can save equipment and simplify operation, but on the other hand, A large amount of microorganisms etc. adhere to the packed bed of granular media in a short period of time, increasing the filtration resistance and eventually clogging the packed bed. Therefore, the packed bed should be backwashed as appropriate, or the granular media should be taken out and scrubbed. However, there was a problem in that it was not easy to peel off the deposits and it was difficult to remove them sufficiently. The present invention solves the above-mentioned problems when treating separated liquid of septic tank sludge by biological treatment using a packed bed of granular media, and makes it possible to downsize septic tank sludge treatment equipment and simplify its operation. The purpose is to provide a processing method for [Means for Solving the Problems] The present invention involves adding an organic polymer flocculant to septic tank sludge for dehydration, and adding part of the septic tank contamination and at least one of the inorganic flocculants to the resulting dehydrated separated liquid. The organic polymer flocculant that remains in the dehydrated separated liquid is insolubilized and then solid-liquid separated, and the separated solid-liquid separated liquid is treated in a biological treatment process using a packed bed of granular media. It is also a method for treating septic tank sludge, characterized in that nitrification and denitrification treatments are performed in the biological treatment step. [Operation] To explain the operation of the present invention with reference to the drawings showing one embodiment, in FIG. After being introduced into an aeration tank 3 and oxidized by an oxygen-containing gas 4, a cationic polymer (organic polymer flocculant) 5 is added and flocculated in a flocculation tank 6, and then dehydrated in a dehydrator 7. , separated into a dehydrated cake 8 and a dehydrated separated liquid 9. A cationic polymer remains in the dehydration separation liquid 9, and in order to adsorb this cationic polymer, the septic tank sludge flowing out from the aeration tank 3 (septic tank sludge 1 introduced into the aeration tank 3) is added to the dehydration separation liquid 9 to adsorb this cationic polymer. Either part 10 of (may be) and inorganic flocculant 11,
Alternatively, when both are added and mixed, the cationic polymer is adsorbed to the sludge or the generated floc, and separated in the settling tank 12. The separated sludge 2 separated in the settling tank 12 is led to the aeration tank 3 as described above. In addition, in the dehydrated separated liquid 9 flowing into the settling tank 12,
Further, an anionic polymer or a nonionic polymer 13 can be added to coagulate the sludge or flocs that have adsorbed the residual cationic polymer, thereby increasing their settling properties in the settling tank 12. However, if the amount of anionic polymer or nonionic polymer 13 added is about the same as the amount of cationic polymer 5 added for dewatering septic tank sludge, the anionic polymer or nonionic polymer will remain. Since the biological treatment step 15 is blocked, it is necessary to make the amount significantly smaller than the amount of the cationic polymer 5, and it is appropriate to set the amount to be about 1 to 2 mg/approx. The precipitated separated liquid 14 from which the residual cationic polymer has been removed is led to a biological treatment tower 15, where oxygen-containing gas 4 is blown into it for biological treatment, and treated water 1
6 and flows out of the system. An example of the biological treatment tower 15 will be further described in detail with reference to FIG. Packed bed of granular media for biofouling such as anthracite 2
1, the packed bed 21 is maintained in an aerobic condition by the air (oxygen-containing gas) 4 blown from the aeration air pipe 22 in the support layer 20. The BOD components inside are oxidized and decomposed by BOD oxidizing bacteria attached to the surface of the granular medium, and at the same time SS (suspended matter) in the precipitated separation liquid 14 is
The treated water is also filtered by the packed bed, becomes treated water 16, and flows out from the treated water outflow pipe 23 in the support layer 20. As such biological treatment continues, the filtration resistance of the packed bed 21 increases in combination with the filtration action performed at the same time, so it is necessary to backwash the packed bed 21. Backwashing of the packed bed 21 is performed by stopping the inflow of the precipitated separation liquid 14 and supplying air from the air washing pipe 24 in the support layer 20, washing water from the washing water pipe 25 through the treated water outflow pipe 23, or both at the same time. It ejects and disturbs the packed bed 21 while peeling off the deposits of granular media, and the backwash wastewater 17 is sent to the overflow trough 26 at the top of the tower.
and is discharged from the intermediate drain pipe 27. This backwash wastewater 17 contains deposits and other excess sludge entrained by backwashing, and is returned and mixed into the dewatering separation liquid 9 of the dehydrator 7 for treatment (see Figure 1). . Furthermore, when removing nitrogen components from the septic tank sludge 1 to be treated, it is preferable to perform biological nitrification and denitrification treatment simultaneously with BOD oxidation and filtration in the biological treatment tower 15. For example, if the biological treatment tower is made into three towers and the precipitate separation liquid 14 is passed through in series, the first tower
Along with BOD oxidation, NH ₃ −N is nitrified to NO _x −N,
In the second tower, a denitrifying agent (hydrogen donor) is added to reduce NO _x
-N is reduced and decomposed to _N2 , and then the remaining denitrifying agent is oxidized in the third column. [Example] FeCl ₃ , septic tank sludge, etc. were added to and mixed with the dehydrated separated liquid in which 5 mg of cationic polymer remained, and then 1 mg of anionic polymer was added and separated by precipitation in a settling tank. Add the liquid to the second
The liquid was passed through a biological treatment tower as shown in the figure in a downward flow. The conditions at that time were as follows. Dehydrated separated liquid water quality (average): BOD 210 mg/, SS 99 mg/, cationic polymer 5 mg/Dehydrated separated liquid processing amount: 5.4 m ³ /day Sedimentation tank volume: Diameter 7.0 m, depth 1.2 m Biological treatment tower, volume: Diameter 0.4 m, height 5.0m Filled bed: Anthracite grain size 3mm Layer thickness 2000mm Table 1 shows the conditions for adding FeCl ₃ and the like.

〔Effect of the invention〕

As described above, according to the present invention, the problems of rapid increase in filter resistance and difficulty in backwashing, which are problems when treating septic tank sludge in a biological treatment process using a packed bed of granular media, are solved, This makes the septic tank sludge treatment equipment more compact and easier to operate.

[Brief explanation of the drawing]

FIG. 1 is a system explanatory diagram showing one embodiment of the present invention, FIG. 2 is an explanatory diagram of the configuration of a biological treatment tower, and FIG. 3 is a diagram showing the relationship between liquid passage time and filtration in the biological treatment tower for each experimental example, and It is a diagram showing backwashing timing and its effects. 1... Septic tank sludge, 2... Separated sludge, 3... Aeration tank, 4... Oxygen-containing gas, 5... Cationic polymer, 6... Coagulation tank, 7... Dehydrator, 8... Dehydrated cake, 9... Dehydrated separated liquid, 10... Part of septic tank sludge, 11... Inorganic flocculant, 12... Sedimentation tank, 14... Precipitated separated liquid, 15... Biological treatment tower,
16... Treated water, 17... Backwash wastewater, 20... Support layer, 21... Filled layer, 22... Air pipe for aeration,
23... Treated water outflow pipe, 24... Air washing pipe, 25...
...Washing water pipe, 26...Overflow trough, 27...Intermediate drain pipe.

Claims (1)

[Scope of Claims] 1. Adding an organic polymer flocculant to septic tank sludge and dehydrating it, adding a portion of the septic tank contamination and at least one inorganic flocculant to the resulting dehydrated separated liquid, and adding a part of the septic tank contamination and at least one inorganic flocculant to the dehydrated separated liquid. A treatment for septic tank sludge characterized by insolubilizing the organic polymer flocculant remaining in the sludge, performing solid-liquid separation, and treating the separated solid-liquid separated liquid in a biological treatment process using a packed bed of granular media. Method. 2. The method for treating septic tank sludge according to claim 1, wherein nitrification and denitrification treatments are performed in the biological treatment step.