JPS5996000A - Dehydrating method of sludge - Google Patents

Abstract

PURPOSE:To improve dehydration rate in the stage of dehydrating the sludge generated from a biological treatment of waste water by subjecting the sludge, as a pretreatment, to an O3 treatment thereby breaking the cellular films of microorganisms in the sludge and dehydrating the internal water. CONSTITUTION:Raw water (e.g.; municipal sewage, night soil and various other industrial waste water), and the desorbed liquid 14 from a thickener 14, an anaerobic digester 5 and a dehydrator 6 are supplied into a setting tank 1, where precipitate is settled. The supernatant liquid thereof is fed to an aeration tank 2. On the other hand, the precipitate is fed as raw sludge to the thickener 4. The raw sludge 13 from the tank 1 and the excess sludge 12 from the final settling tank 3 are supplied to the thickener 4 where the sludge is thickened. The thickened sludge 15 is fed to the digester 5. The digested sludge 16 emitted from the digester 5 is fed to an O3 oxidation tank 19, where the ozonized air 21 generated in an O3 generator 20 is supplied to the sludge 16 to break the cellular films of the microorganisms in the digested sludge. The moisture in the cells of the microorganisms is dehydrated in the dehydrator 6. The treatment function in the dehydrater is thus remarkably improved and the consumption of fuel for incineration in the succeeding stage is decreased.

Description

[Detailed description of the invention] Concerning the improvement of the analytical method.

Figure 1 shows a general flow sheet for a conventional wastewater treatment process for municipal sewage, human waste, and various other industrial wastewaters.

1 is the first settling tank, 2 is the aeration tank, 3 is the final settling tank, 4 is the concentration tank, 5 is the anaerobic digestion tank, 6 is the dehydration tank, 7 is the dryer, 8
is incinerator, 9 is raw water, 10 is treated water, 11 is return sludge,
12Ii surplus sludge.

13 is raw sludge, 14 is desorbed liquid, and 15 is thickened sludge.

16 represents digested sludge, 17 represents dehydrated cake, and 18 represents dried sludge.

Initially, the settling tank 1 contains raw water 9 (for example, urban sewage).

human waste and various other industrial wastewater) is supplied to the concentration tank 4, anaerobic digestion 5, and dehydration tank 6 to the desorption rL14 to precipitate the precipitate and send the supernatant liquid to the aeration tank 2, while the precipitate is treated as raw sludge. Send to concentration tank 4.

The aeration tank 2 receives the supernatant liquid from the initial sedimentation tank 1 and 1 liter of returned sludge from the final sedimentation tank 3, contacts it with air or oxygen, aerates it, grows aerobic microorganisms, and purifies the treated liquid with these microorganisms. and send to final precipitation 1i13. Note that a rotating disk type or the like can also be used as the aeration device.

In the aeration tank 2, the treated liquid and microorganisms are supplied to the final settling tank 3, where the precipitate is precipitated and the supernatant liquid is made into treated water 10 and is either discharged or sent to an advanced treatment process.

On the other hand, a part of the sediment is returned to the aeration tank 2 as return sludge 11, and the other part is sent to the thickening tank 4 as surplus sludge 12.

The raw sludge 13 from the initial settling tank 1 and the excess sludge 12 from the final settling tank 3 are supplied to the thickening tank 4 and concentrated. Desorption liquid 14
At first, the sedimentation tank IK was returned.

The thickened sludge I5 is sent to the anaerobic digestion tank 5. That is, the excess sludge generated from the biological treatment process of wastewater is concentrated and reduced in volume.

In the anaerobic digestion tank, the concentrated sludge 15 is putrefied using methane bacteria to completely decompose organic matter, further reducing the volume, and the digested sludge 16 is sent to the dewatering tank 6. - The force syneresis liquid 14 is first returned to the settling tank IK.

In the dehydration tank 6, the digested sludge 16 is dehydrated using a dehydrator such as a belt press or a filter press, and the dehydrated cake 17 is transferred to the dryer 7.
The desorption gj, 14I′i is returned to the initial precipitation tank l.

The dryer 7 completely dries the dehydrated cake and incinerates it as dried sludge 18 in the incinerator 8.

As mentioned above, the process is roughly divided into water treatment process and sludge treatment process, the former mainly involves "biological treatment" such as the standard activated sludge method, and the latter involves concentration → (anaerobic digestion) → dehydration → drying.
Incineration is the standard configuration. Sludge generated from water treatment processes is composed of suspended solids in the target wastewater, sedimented and separated colloidal substances, and the surplus of purified microorganisms grown in biological reaction tanks (aeration tanks) that are discharged. Ru. Water in sludge exists either surrounded by sludge particles or directly bonded to them, and its forms can be roughly divided into the following four types.

(1) pore water, (2) capillary bound water, (3) surface adhering water,
(41 Internal water, etc.) Of these, (4) refers to the water present in the bodies of microorganisms that form sludge, and to eliminate it, the microbial cell membrane must be destroyed. Conventionally, as a pretreatment for dehydration, Heat treatment methods have also been used, but this dehydration method does not dehydrate the internal water contained in cell membranes, and there is a natural limit to the dehydration rate.

The present invention was proposed for the purpose of eliminating the drawbacks described in the paper, and is characterized in that ozone treatment is applied as a pretreatment for dewatering sludge generated from biological treatment of wastewater. .

By performing such treatment, the fine cell membranes in the sludge are destroyed, internal water is dehydrated, and the dewatering rate can be improved.

Embodiments of the present invention will be described below with reference to FIG.

Since the symbols 1 to 4 and 7 to 18 are the same as those in the conventional example shown in FIG. 1, their explanation will be omitted.

19 is an ozone oxidation tank and digested sludge 1 from anaerobic digestion tank 5
6 and ozonized air 21 generated by an ozone generator 20 are supplied, and within the tank, the cell membranes of microorganisms in the digested sludge are destroyed by the action of the ozonized air.

Next, in the dehydration tank 6, even the water inside the cells of the microorganisms is dehydrated. The processing function in the dehydration tank has been significantly improved, and the downstream dryer and incinerator equipment have become more compact, and the amount of fuel consumed for incineration can be reduced, among other ripple effects.

[Brief explanation of the drawing]

Figure 1 shows the general flow of a conventionally known wastewater treatment process.
- indicates FIG. 2 shows a flow route of one embodiment of the present invention. Engineering...No.
Final settling tank, 4... concentration tank, 5... anaerobic digestion tank,
6... Dehydration tank, 7... Dryer, 8... Incinerator. 19...Ozone oxidation tank, 20...Ozone generator.

Claims (1)

[Claims] A sludge dewatering method characterized in that ozone treatment is performed as a pretreatment for dewatering sludge generated from biological treatment of wastewater.