KR200325153Y1 - High efficiency sludge dewatering equipment by high temperature sludge of anaerobic digester - Google Patents

Abstract

The present invention is a technique related to sludge dewatering in the case of using an anaerobic digester for sludge treatment in sewage treatment plants.

An object of the present invention is to provide a sludge dewatering device for maintaining the sludge dewatering efficiency even in a low water temperature season by dehydration using high heat of the middle temperature anaerobic digester.

In order to achieve the object of the present invention, the raw sludge from the first sedimentation basin of the sewage treatment plant and the surplus sludge from the final sedimentation basin are collected and concentrated in a high concentration in a mechanical concentrator, and the concentrated sludge is reduced by methane gasification in an anaerobic digester. Afterwards, the system was configured to dehydrate digested sludge in the dehydrator connected directly to the digester in a sealed pipe so that it could be dehydrated at a relatively high temperature of 30-35 ℃, which is the same temperature as the digester.

The present invention dehydrates sludge which has a high temperature at all times and uses a heat of digester even in a low temperature of winter so that the dehydration efficiency can be constantly increased throughout the year, so that the moisture content of the dehydrated cake is low and the amount of dehydrated cake is reduced. It works.

Description

High efficiency sludge dewatering equipment by high temperature sludge of anaerobic digester

The present invention is a technique related to dewatering sludge in sewage treatment plants.

The conventional technique for dewatering sludge in a sewage treatment plant is to concentrate the raw sludge and surplus sludge in the sludge treatment process, and then supply the concentrated sludge to the anaerobic digester gradually and as much as the amount of concentrated sludge supplied to the digester. It was common to remove little by little from the digester and store it in the sludge storage tank installed in the dehydration tank.

In this case, the problem is that the digested sludge, which was more than 30 ° C in the digester, cools during the day in the sludge storage tank during the low temperature season, such as winter, and dehydrated in a state of low water temperature so that the dehydration cake cannot be easily dehydrated. Will increase the water content.

If the conventional dehydration method is used, the temperature is low for many periods of the year (about 6 months or more) in places where the temperature of the sewage in the natural state is low, such as in Korea, and the natural temperature of sewage is 5-20 ℃ except for the summer. The sludge will be dehydrated.

Since the water content of the digested sludge before dehydration is usually 97-98%, the viscosity of the sludge is sensitive to temperature like the viscosity of water and the viscosity of water is 1.307 × 10 ^-3 Ns / ㎡ at 10 ℃. It is 0.653 × 10 ^-3 Ns / m2 at ℃, and the lower the water temperature, the higher the viscosity coefficient.

Viscosity coefficient of water can be seen that the water of 10 ℃ is about 2 times larger than the water of 40 ℃ and the water temperature is low due to the difference in viscosity is not good dehydration.

Dehydration occurs because the water between the sludge solids escapes from the sludge when the sludge is subjected to physical pressure or centrifugal force. It is not easy to be dehydrated, and it is difficult to dispose of the dehydrated cake, which is dehydrated sludge that comes out after dehydration, and it is difficult to dispose of it. (The sewage sludge with a water content of 75% or less is prohibited by law. It is difficult to transport, and the volume and weight of dehydrated cakes for the same solids are also increased, which requires a lot of cost for disposal, which is an economic waste and increases secondary environmental pollution.

For reference, the relationship between the solids, the water content and the weight of the dehydrated cake is shown in Equation 1.

Although the actual dehydrator operation data of sewage treatment plant differs depending on the quality of the sewage and the treatment process, the dewatering cake moisture content in the case of belt filter press type dehydrator is 76% on average when the water temperature is high in summer. The water content of was about 85%, which is about 9% higher than in summer, which was attributed to the difference in water temperature due to seasonal factors of dewatered sludge.

If the water content of 9% is different in the dehydrated cake, the weight of the dehydrated cake is different for the SS (solids) in the same sludge as follows.

here;

W _S1 : Weight of dehydrated cake at 76% moisture content against SS100Kg

W _S2 : Weight of dehydrated cake at 85% water content relative to SS100Kg

As in the above calculation example, the difference in the weight of dehydrated cakes for the difference of 9% of moisture content is 1.607-1 = 0.60 times and the difference of 60% remains when converted to%, and for the small difference of the moisture content of dehydrated cakes, the weight of dehydrated cake weight is It is very different that lowering the moisture content of the dehydrated cake as much as possible is an important way to reduce the amount of dehydrated cake.

In dewatering sludge in sewage treatment plant, raw sludge and surplus sludge from sewage treatment plant are concentrated together in a high concentration in a mechanical concentrator, and the concentrated sludge is reduced by methane gasification through digestion in an anaerobic digester, and the digested sludge is not stored. It is to provide a sludge dewatering device to reduce the amount of dehydration cake generated by direct dehydration from the dehydrator.

1 is a schematic diagram showing a configuration of the present invention

Explanation of symbols for important parts of the drawings

1. Mixing sedimentation tank 2. Transfer piping 3. Sludge transfer pump

3-1. Sludge Flow Meter 4. Mechanical Sludge Thickener 5. Transfer Piping

6. Concentrated Sludge Storage Tank

7. Concentrated Sludge Transfer Pipe 8. Concentrated Sludge Transfer Pump 8-1. Concentrated Sludge Flowmeter

9. Anaerobic digester 1 stage 10. Anaerobic digester 2 stage 11. Digester heating equipment

12. Fire extinguishing sludge conveying pipe 13. Fire extinguishing sludge conveying pump

13-1. Fire extinguishing sludge flow meter 14. Dehydrator

15. Coagulant Feeder

end. First Settling B. Microbial reaction tank (aeration tank) Final sedimentation basin

la. Fresh Sludge Transfer Pump Surplus Sludge Transfer Pump

hemp'. Fresh sludge flow meter

bar. four. Sludge Transfer Pipe Bar '. Surplus sludge flowmeter

Ah. Concentrated Desorbent Return Pipe

character. Dewatering and returning piping car. Symbolic water return piping

In order to achieve the object of the present invention,

A mixed sedimentation tank capable of mixing the excess sludge from the final sedimentation basin in the sewage treatment plant and the raw sludge from the initial sedimentation basin to settle for a short time to precipitate and concentrate to a certain level and to coagulate sediment if necessary;

A mechanical sludge thickening device for concentrating the sludge conveyed from the mixed settling tank to a high concentration;

A concentrated sludge reservoir with a stirrer to temporarily store concentrated sludge in the sludge concentrator and prevent sludge settling;

A one-stage or two-stage anaerobic digestion apparatus having an anaerobic digestion and heating facility, supplying the concentrated sludge of the concentrated sludge storage tank to the digester evenly for 24 hours with a concentrated sludge transfer pump;

A dehydration device connected directly to the anaerobic digestion apparatus with a transfer pipe and dehydrated while allowing the digested sludge to be constantly supplied by the digestion sludge transfer pump; And it provides a sludge dewatering device to increase the dewatering efficiency by using the heat of the digester to dehydrate while drawing an equal amount while dehydrating the amount of sludge to be dehydrated per day.

Hereinafter, the present invention will be described in detail.

The sewage flowing into the sewage treatment plant becomes fresh sludge by removing a large amount of solids and organics from the initial sedimentation basin (a), and the sewage from which the sludge has been removed is the following microbial reaction tank (b) (denitrification dephosphorization tank for aeration or advanced treatment). Biologically removes the remaining organic matter and nutrients, and separates solids and water in sewage from the final settler (C), and water is discharged out of the sewage treatment plant as discharged water. Most of the separated solids are returned and some are treated as sludge. Transferred to the system.

The fresh sludge is pumped periodically or continuously by the fresh sludge conveying pump (D) and the excess sludge is conveyed to the mixed sedimentation tank 1 through the sludge conveying pipe (bar) by the surplus sludge conveying pump (E). It was.

In the mixed sedimentation tank (1), the introduced sludge and surplus sludge are mixed, homogenized and precipitated, and the concentrated sludge is concentrated to 1.5 to 2% of solids, and the concentrated sludge acts as a sludge transfer pump (3) through the transfer pipe (2). It was transferred to the mechanical sludge concentrator (4) and the symbol water after precipitation was returned to the inlet of the most sedimentation basin through the symbol water conveying pipe (tea).

The mixed settling tank 1 was configured to inject a flocculant in preparation for deterioration of the bulking of the microbial reaction tank such as aeration tank or the deterioration of the excess sludge, so that a good settling can always occur.

The sludge concentrated in the mechanical sludge thickener (4) was transferred to the thickened sludge storage tank (6) with the stirrer through the thickened sludge conveying pipe (5) for temporary storage (usually one day), and the mechanical sludge thickener (4). Concentrated desorption liquid generated at was returned to the inlet of the first settling basin (A) through the concentrated desorption return pipe (H).

The concentrated sludge stored in the concentrated sludge storage tank (6) is transferred to the first stage (9) of the anaerobic digester by the concentrated sludge conveying pump (8) through the concentrated sludge conveying pipe (7), and the second stage of the anaerobic digester (10) by natural flow. In the anaerobic digester heating facility (11), hot water or steam was supplied to the anaerobic digester to maintain a prescribed temperature.

The digestion sludge feed pipe 12 is connected to the lower portion of the anaerobic digester 2 stage 10, and the digestion sludge feed pipe 13 is connected to the end of the digestion sludge feed pipe 12, and the extinguishing sludge feed pump 13 can automatically adjust the discharge amount. The rear end of the pump 13 and the inlet of the dehydrator 14 were connected to the fire extinguishing sludge conveying pipe 12, and a fire extinguishing sludge flowmeter 13-1 was installed therebetween.

The dehydrator 14 was able to supply the necessary flocculant through the flocculant supply device 15.

The dehydration cake dehydrated in the dehydrator 14 is taken out to the outside and the dehydrator desorption liquid generated during the dehydration process is returned to the inlet of the initial settling basin (a) through the dehydration desorption liquid return pipe (za).

The operating method of the device according to the invention is as follows.

Fresh sludge and surplus sludge generated by the inflow of sewage are transferred to the mixed sedimentation tank 1 through the pipe connected by the action of the respective sludge transfer pumps d and e. In the mixed sedimentation tank 1, the excess sludge and Fresh sludge is stored for a residence time of about 1 to 3 drawing periods (2 to 3 hours), and the precipitate is concentrated in a relatively homogenized state with a mixture of surplus sludge and sludge having different concentrations of fresh sludge (usually about solid concentration 1). ~ 1.5%) and the concentrated sludge is transferred to the mechanical sludge thickener (4) by the action of the sludge conveying pump (3), and the symbol water is returned to the inlet of the initial settling basin (a) through the symbol transport pipe (tea). .

The sludge conveyed from the mixed settling tank 1 is concentrated in the mechanical sludge concentrator 4 so as to have a solid concentration of about 4 to 6%.

The concentrated desorption liquid generated in this process is returned to the inlet of the initial settling point (a) through the concentrated desorption liquid return pipe (h), and the concentrated sludge is concentrated in the natural flow state by gravity through the concentrated sludge conveying pipe (5). 6) is transferred to.

The concentrated sludge storage tank 6 is equipped with a stirrer to prevent sludge settling and homogenize the sludge, and the storage time is usually one day (about 24 hours).

The concentrated sludge which has been temporarily stored in the concentrated sludge storage tank 6 is supplied to the first stage 9 of the anaerobic digester at an equal speed so that the concentrated sludge for one day can be supplied by the concentrated sludge transfer pump 8 for 24 hours. Anaerobic digestion takes place under conditions of rapid agitation and 30 to 35 ° C. during a residence time of about 15 days, and is then transferred to the anaerobic digester 2nd stage 10 by gravity to cause digestion and precipitation in stationary conditions, or 1 depending on the device. Anaerobic digestion takes place under the conditions of rapid stirring and forging at 30-35 ℃, and the sludge is completely digested through two stage digesters, some of which become methane gas and used as a heat source for the anaerobic digester heating device (11). The remaining digested sludge reduced in amount by the digested sludge transfer pipe 12 is installed in the lower portion of the anaerobic digester 2 stage (10). It is conveyed to the dehydrator 14 by the feed pump 13.

At this time, the amount of digested sludge to be transported is the amount required for one dehydration time (usually 8 hours), and the capacity of the digested sludge transport pump 13 is determined so that the amount of digested sludge is equally transported in one dehydration time and extinguish only during the dehydration time. The sludge feed pump 13 is configured to operate, and the fire extinguishing sludge feed pump 13 is linked with the fire extinguishing sludge flowmeter 13-1 installed at the rear end so as to automatically change the feed amount so that the designated feed amount can be transferred. By configuring the device, the amount of feed can be properly adjusted to ensure the best dewatering depending on the condition of the dehydrator and the digested sludge.

In this way, the sleep of the anaerobic digester 2 stage (10) is lowered during the dehydration time by the dehydration of the day, and as the concentrated sludge is supplied to the anaerobic digester 1 stage (9) until the same time the next day, the water gradually increases and eventually returns to the first water level. It is restored and there is no return or overflow.

This is because in the anaerobic digester of the present invention, in the anaerobic digester of the present invention, in the anaerobic digester of the present invention, in the anaerobic digester, the overflow water is generated every time the concentrated sludge is supplied throughout the day and is returned to the initial sedimentation basin, and only part of it is drawn from the digester. none.

In general, the overflow water in anaerobic digester contains high concentration of solids due to poor solid-liquid separation, which is returned to the inlet of the sewage treatment plant and mixed with the influent sewage to increase the pollutant load of the sewage treatment plant. By eliminating the excess water, the increase in pollution load of the influent sewage caused by the overflow water return does not occur.

Since the digested sludge delivered to the dehydrator 14 is dehydrated immediately after being transported, the sludge is dehydrated at a high temperature of 30 to 35 ° C. such as the temperature of the second stage 10 of the anaerobic digester, so that the sludge has a low viscosity coefficient. The moisture content of is low and the amount of dehydrated cake is reduced.

In the present invention, raw sludge and surplus sludge are mixed, concentrated by primary precipitation by gravity, and then concentrated in a high concentration in a mechanical concentrator, so that a small volume of concentrated sludge is supplied to the anaerobic digester for digestion to ensure sufficient digestion time. Due to the high digestibility, the sludge is reduced first and dehydrated at high temperature such as anaerobic digester, so the viscosity coefficient of sludge decreases even in winter when water temperature and temperature are low and the dehydration efficiency is high, so the water content of dehydrated sludge cake is lowered. As the amount of dehydration cake is reduced, secondary sludge is reduced, which can reduce the amount of sludge as a whole. Therefore, it is possible to reduce the cost of disposal of sludge or the cost of reforming for landfill. Wreath There is no need to reduce pollution and build a separate sludge storage tank in a dehydrator such an effect that the initial construction cost savings.

Claims (1)

A mixed sedimentation tank capable of mixing the excess sludge from the final sedimentation basin in the sewage treatment plant and the raw sludge from the initial sedimentation basin to settle for a short time to precipitate and concentrate to a certain level and to coagulate sediment if necessary; A mechanical sludge thickening device for concentrating the sludge conveyed from the mixed settling tank to a high concentration; A concentrated sludge storage tank having a stirrer capable of temporarily storing the sludge concentrated in the sludge concentrator and preventing sludge settling; A one-stage or two-stage anaerobic digestion apparatus equipped with a heating system for digesting the concentrated sludge in the concentrated sludge storage tank to the digester for 24 hours evenly with a concentrated sludge transfer pump and having a heating facility; A dehydration device connected directly to the anaerobic digestion apparatus with a transfer pipe and dehydrated while allowing the digested sludge to be constantly supplied by the digestion sludge transfer pump; And a sludge dewatering device that improves the dewatering efficiency by using heat of a digester to dewater while being equally drawn while directly dehydrating the amount of sludge to be dehydrated per day.