DE2711040A1 - PROCESS AND EQUIPMENT FOR Sludge TREATMENT - Google Patents

Description

Patent Attorneys 9711

.,. pL-lng. E. Eder X / I I

Dip] .- Ing. K. Schieschke

! IMnchen «), ElisabeitK> tiaB334 _

KUBOTA TEKKO KABUSHIKI KAISHA (KUBOTA, LTD.)

Osaka / Japan Process and plant for sludge treatment

The invention relates to an improved method for treating sludge from wastewater treatment, in particular on a low-temperature heat treatment of sludge containing organic substances under pressure and on a system for carrying out this process.

A sludge treatment process is already known at which the organic matter-containing sludge undergoes heat treatment in a reactor at relatively low temperatures

O Temperatures below 165 C experienced with the introduction of steam and Compressed air to keep the reactor in an oxidizing atmosphere According to this process, the volume of air introduced into the reactor is greater than the value theoretically required to reduce the chemical oxygen demand (COD) by 2 - 4% and is 10-3O times the volume of the treated sludge, wherein the steam volume is regulated so that the over a thermocouple in the reactor monitored reaction temperature remains below 165 ° C.

This low-temperature printing process was developed to deal with high-temperature processes at higher temperatures of

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approx. 2OO ° C occurring difficulties to resolve, namely e.g. syneresis of the sludge, strong odor development of the separated gas, blockage of the heat exchanger with organic substances

With low-temperature printing processes, the filterability and the dewatering properties of the sludge can be improved despite improve the relatively low reaction temperatures, so that the effectiveness of the sludge treatment also increases. High pressure and high temperature, as used in the usual known processes, e.g. in the Zimmermann process, are not required.

There is also known a sludge treatment method (Japanese Patent Applications Nos. 49-13985, 49-53719, 49-137339) according to which the sludge to be treated is preheated in a heat exchanger before it is heat-treated in the reactor with steam and compressed air where already heat-treated sludge serves as a heat source for the heat exchanger.

These known methods have the following difficulties:

1) The air sent into the reactor rises in the form of large air bubbles, but not evenly, but sometimes only on one side of the reactor. As a result, the sludge is not adequately admitted with air, which the

Effectiveness of heat treatment impaired.

2) The gas separated in the reactor is discharged in the form of bubbles via a discharge line at the top of the reactor, which leads to clogging, corrosion and wear of the pipe.

3) The known methods are not suitable for the treatment the separated clear water.

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4. For the deodorization of the sludge treatment stage malodorous gas, chemicals are used. Such deodorization processes are uneconomical.

The invention is based on the object of a self-contained Provide low-temperature printing processes for sludge treatment, in which not only a heat treatment of the sludge in the reactor takes place, but also a treatment of the separated clear water and a deodorization of the im Gas produced during the process in order not to discharge any harmful exhaust gases or wastewater.

To achieve this object, the invention provides a sludge treatment process before, in which the sludge in the reactor is evenly exposed to air, the emergence of air bubbles is prevented from the reactor and the clear water separated from the treated sludge in at least one single-stage activated sludge process is treated.

To carry out this method, the invention provides a Arrangement before with a reactor in which a number of perforated plates in horizontal, each a distance from each other having layers are arranged, above which perforated plates, a partition wall divides the reaction space into an oxidation chamber and a sludge condensation chamber and each perforated plate on its underside with one of the air bubbles for uniform exposure of the Sludge evenly distributing rib profile is provided, with a further the exit of air bubbles with the separated Gas-preventing device and a clarification stage for the clear water separated from the heat-treated sludge provided are.

According to one feature of the invention is an effective clarification stage for treating the clear water separated by the hot melt thickener and the filtrate obtained from the dewatering stage intended.

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The invention creates an efficient treatment method for exhaust gas and wastewater, the deodorization of the ventilation stank in the sludge thickener and in the filter press resulting malodorous gases combined with the disposal of wastewater from one to the disposal of one from the Combustion stage resulting exhaust gas serving desulfurization tower originates.

Further refinements of the invention emerge from the Subclaims

The invention is described in more detail below with reference to an exemplary embodiment shown in the drawings. In the drawings shows:

1 shows the scheme of a sludge treatment plant according to the invention;

2 shows a vertical section through a reactor according to an embodiment of the invention;

Fig. 3 is a perspective view with parts cut away of the perforated ones provided in the reactor Plates and rib profiles;

Fig. 4

and Fig. 5 bottom views of the perforated plates

provided rib profiles;

6 shows a vertical section through part of the reactor according to FIG. 2;

7 is a diagram of a clarification stage according to the invention

Fig. 8 is a diagram of a deodorization stage according to the invention;

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As can be seen from FIG. 1, the raw sludge mixture pumped from a primary and secondary clarifier into a sewage treatment plant is first thickened in a raw sludge thickener 10 to a solids concentration below 3.5 4%. After the separation of foreign substances, which could lead to seizing of the pumps and clogging of the pipes and heat exchangers, the thickened sludge is stored in a thick sludge tank 11 and is pumped from there to a heat exchanger 12. This heat exchanger is built as a double tube design, with the untreated sludge being sent through the core tube and the already heat-treated sludge coming from the reactor 16 through the jacket tube in the opposite direction in order to heat the untreated sludge up to 120 ° C by indirect heat exchange. Any heat-conducting media, for example water, can be used to recover the heat of the heat-treated sludge and to preheat the untreated sludge.

The preheated sludge is converted into a cyclone Sand separator 13 Removed sand to prevent wear and tear on downstream components. That of sand The released sludge is fed into the reactor from below with steam from the boiler 14 and compressed air from the compressor 15 16 sent. By heat treatment over a period of

30 minutes or more at 130 ° - 165 ° C under a pressure of

approx. 10 kg / cm, which causes an intensive brushing with air, the filterability of the sludge is improved. The gas separated in the reactor 16 with sludge is in a combustion stage 19 burned.

The heat-treated sludge is from the reactor 16 via a pipeline to the heat exchanger 12 for heat recovery such as sent described above so that it cools down to approx. 60 ° C. The sludge is then left in a hot sludge thickener 17 settle where it separates through natural sedimentation into overflowing clear water and thick sludge. The thick mud

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is pumped to a dewatering stage, e.g. a filter press 18, where it is filtered under pressure. The filter cake is burned to ash in the incineration stage 19 which includes a waste heat boiler. The calorific value of the mud cake is recovered in the waste heat boiler in the form of steam, which is reused as a heat source for the heat treatment in the reactor.

The separated clear water, which is made up of overflowing clear water of the hot melt thickener 17 and from FiItrat from the Filter press 18 is made in a separate clarification stage 20 a biological treatment, as will be described. The treated clear water is sent back to a standard water treatment plant.

In this sludge treatment plant, the reactor 16, the raw sludge thickener 10, the thick sludge tank 11, the warm sludge thickener 17, the filter press 18 and the aeration tanks are the Clarification stage 20 the main sources of malodorous gases.

The gas coming from the reactor 16 is in the combustion stage 19 * and the gas coming from the thickener 17 is used for ventilation in the clarification stage 20 is used. «Burned

Less malodorous gases from other sources are fed to a deodorization stage 21 to be described.

The exhaust gas from the incinerator 19 is treated in a desulfurization tower 53 to remove the sulfuric acid gas (SOp) contained therein. The wastewater from this tower is used in deodorization stage 21.

As can be seen from FIG. 2, the sludge obtained from the sand separator is fed to the reactor 16 via a pipe 22. At the same time takes place via the pipes 23 and an introduction of steam and compressed air into the reactor. In the upper section of the reactor 16, a partition 25 is provided which the reaction space in an oxidation chamber 26 and in a heat condensation chamber 2j7g ra £ or / tAiil £ g

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In the first chamber, below the partition wall, there are a number of perforated plates 28 in horizontal, spaced-apart manner arranged layers provided. In order to achieve regular intervals between them, they are attached to the reactor before they are installed their circumference preferably via a number of vertical connecting rods 29 welded together (Fig. 3).

On the underside of each perforated plate 28 is a rib profile 30, e.g. attached by welding. The rib profile can be latticed as in Fig. 3, or in the form of crossed, concentric circles (Fig. 4) or honeycomb (Fig. 5).

In all cases, the rib profile 30 forms a number of air chambers η 31.

A dehumidifier 32 in the form of superimposed wire layers is attached in a horizontal arrangement to the partition wall 25, in the upper edge (Fig. 6) a plurality of V-shaped notches is trained. Above the dehumidifier 32, a steam heating coil 34 is provided in a horizontal arrangement, which here Is shown spirally, but can also be designed in a zigzag or grid shape.

A separate gas vent 39 is from a tubular dehumidifier 36, which also consists of wire layers and is closed at its lower end by an end plate 35. The gas separated in the reactor flows through the dehumidifier 32 into an exhaust pipe 37 in which a pressure control valve is located.

Since the compressed air blown into the reactor 16 together with the sludge in the form of air bubbles with partial oxidation of the mud rises, the air bubbles penetrate into each air chamber 31 on the underside of the profile 30 and flow through the holes in the perforated plates 28. Even if these plates were not mounted exactly horizontally, there would be the air bubbles are still well distributed in the air chambers

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and not accumulate on just one side of the reactor 16. This arrangement thus ensures uniform mixing the sludge with air.

After flowing through the perforated plates 28, the sludge floods the partition wall 25 and reaches the heat condensation chamber 27, where it is condensed with the addition of heat in the oxygen-poor, standing state. Although the dehumidifier is 35 on the partition 25 is attached, it does not hinder the flow of sludge, since the V-shaped on the upper edge of the partition Notches 33 are provided. The sludge treated in this way is discharged through an automatic drain valve (not shown) Discharged via a drain pipe 38. Due to this heat treatment in the reactor 16, the sludge undergoes a partial Oxidation, so that it separates into gas and solids, and its ability to be piled up is improved. That over the pipeline 37 separated gas is fed to the combustion stage 19.

When the separated gas passes through the dehumidifier 32, almost all air bubbles burst. Any through the dehumidifier Any air bubbles that have entered burst when they come into contact with the steam heating coil 34. Should some bubbles still remain, so they burst at the second dehumidifier 36. In this way it is ensured that no bubbles whatsoever through the exhaust pipe 37 can exit.

Next, the clarification stage 20 will be described (Fig. 7).

The clear water overflowing in the hot mud thickener 17 and the filtrate from the dewatering device, e.g. the filter press 18, is referred to here as separated clear water. Normally, the separated clear water produced in the low-temperature process has lower biochemical (BOD) and chemical oxygen demand (COD) and also lower dye content than the clear water resulting from high-temperature processes, because the reaction temperature is lower and the reactor

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is kept in an oxidizing atmosphere. The COD and BOD of the invention Process is 1/2 - 2/3 of the corresponding oxygen requirement for high-temperature processes and the dye content is 1/6 to 1/5. A gel adsorption analysis also shows that the deposited in the low-temperature process Clear water is hardly decomposed by the heat treatment and retains properties similar to the raw sludge. It can therefore continue to treat with the activated sludge process without further ado.

The clear water coming from the thickener 17 and the filter press 18 is allowed to set first in a first intermediate tank 40 and then with activated sludge in a first aeration tank 41 ventilate.

A BOD load is preferably applied to the first aeration tank 41 from 1.2 - 2.0 kg / m per day with a concentration of solids suspended in the mixed clear water of 4000-6000 ppm (= 10 "" volume percent) used.

The treated clear water then separates into solids and liquid in a first settling tank 42 from which one Part of the sludge is returned to the first aeration tank 41.

Tests have shown that the BOD of the clear water from the first aeration tank 41 is on average 100-150 ppm corresponds to a degradation rate of 95%. Another BOD reduction is due to the COD effect and the lack of nutrients not to be expected.

The clear water is then diluted approximately three times with raw sewage in a second aeration tank 44. As raw sewage, this is overflowing clear water from the raw sludge thickener 10 is used, which is fed to a second intermediate tank 43. The clear water obtained is then again subjected to a customary activated sludge process.

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The clear water obtained from the second aeration tank 44 is allowed to settle in a second settling tank 45, and the overflowing clear water is then fed to a sewage disposal facility (not shown). Part of the second Sludge contained in the settling tank 45 is returned to the second aeration tank 44. As ventilation air for the first and the second aeration tank, malodorous gas from the sludge thickener 17 is used and deodorized (Fig. 1).

Should an even higher-grade treatment be required, In this way, further treatment stages such as coagulation or piltration stages can be carried out on the second settling tank 45 connect with sand or revitalized charcoal.

The method according to the invention provides an almost complete biological treatment of the separated clear water through two-stage aeration with activated sludge. It also provides a completely simplified procedural system closed circuit with high effectiveness, with the raw water coming from the raw slurry thickener 10 as an inlet source is used.

Finally, the deodorization stage 21 shown in FIG. 8 will be described.

In general, the exhaust gas from sludge treated in the low-temperature process contains little odor from sulfur compounds, for example hydrogen sulfide (H ₂ S) and methyl mercaptan, since the sludge is partially oxidized in the reactor. The odor of the heat-treated sludge is also less intense than in the high-temperature process, since almost all malodorous components are separated from the reactor in the form of the exhaust gas, which is then burned directly in the combustion stage because of the very intense odor.

Gas with a relatively faint odor from the raw sludge thickener 10, the thick sludge tank 11, the filter press 18 and

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the aeration tanks 41 and 44 is fed into a deodorization tower 46 via a pipe 47. The tower will also with ozone (0 ^) from an ozone generator, not shown charged via a line 48 in order to oxidize the malodorous components of the gas.

The deodorized gas, which still contains residual ozone, is discharged at the top of the tower 46 and introduced from below into an ozone removal tower, in which the remaining ozone content is used to treat the wastewater containing _{Na 2 SO ^ fed from the desulphurization tower 53 via a collecting basin 54.} The treated gas and the Na ₂ SO. containing wastewater are disposed of via outlet channels 50 and 5 2.

The desulfurization tower 53 is used to break down the sulfuric acid contained in the exhaust gas from the combustion stage 19 by means of a sodium hydroxide solution (NaOH) which is pumped in from a tank 55 from above. The waste gas from the incinerator is introduced into the tower via a line 56 and coated with caustic soda for desulfurization. The desulphurized gas is then discharged at the top of the tower and the remaining _{liquid containing Na 3} SO ^ flows down into the tank 54.

All three towers 46, 49 and 53 are filled in their central area with the same corrosion-resistant plastic material, which prevents the gas from being drawn through too quickly to be treated effectively.

This deodorization process is much more economical than the previous methods using chemicals and is particularly suitable for sludge treatment plants with a Combustion stage.

The advantages of the low temperature printing process according to the invention are summarized again below.

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1) The process provides a completely self-contained system that allows the treatment of exhaust gas, wastewater and Solids united. There is no possibility for a secondary source of pollution.

2) Dense, uniform air admission of the sludge becomes guaranteed by perforated plates with a rib profile. The rib profile allows the heat treatment of the sludge at relatively low temperatures.

The size of the reactor can be reduced due to the higher reaction capacity to decrease.

3) Complete separation of gas and liquid in the reactor extends the life of the pressure control valve in the gas discharge pipe of the reactor. In addition, the combustion stage can be run at lower temperatures.

4) The low BOD of the separated clear water allows it to be treated in the usual biological process.

5) There is no oxidation stage whatsoever for the desulphurisation tower Waste water produced is required, as it is combined with the remaining ozone contained in the exhaust gas from the deodorization tower is treated.

Patent attorneys Dipl.-ing. E. Eder Dipl.-Ing. K. Schleeci '»

8MBnchen40, Elisatiethetraee34

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Claims (9)

Dip '.- Ing. E- S ---- 'β Munich ", Eii- * ceth6traae34 patent claims 1.) Process for the treatment of wastewater treatment accumulating sludge, whereby the sludge is preheated in a heat exchanger and thereby as direct or indirect Heat source fiirden untreated sludge, already heat-treated sludge and the preheated one with simultaneous entry of steam and compressed air into a reactor for gas separation undergoes a heat treatment, characterized in that the sludge in the reactor is uniformly exposed to air that the escape of air bubbles from the reactor is prevented and that that of the treated sludge separated clear water is treated in an at least one-stage activated sludge process. 2. The method according to claim 1, characterized in that the separated clear water is treated in the activated sludge process, and raw water is added to the clear water treated in this way and this mixture again to an activated sludge process is subjected. 3. The method according to claim 1, characterized in that the malodorous gas generated in the sludge treatment is deodorized using ozone and that to remove the remaining ozone contained in the treated gas Waste water that is produced by a desulphurisation storm used to break down sulfuric acid contained in the waste gas from a combustion stage is coated with the deodorized, ozone-treated gas. 4. Plant for carrying out the method according to claim 1, with a heat exchanger for preheating the untreated sludge with direct or indirect use of 709838/0846 _ ₂ ORIGINAL INoPtGTED of already heat-treated sludge as a heat source and a reactor for further heat treatment of the preheated sludge, in which the preheated sludge of steam and compressed air is applied, characterized in that a number of perforated plates (28) in horizontal layers, each spaced apart from one another, are arranged that above the perforated plates a partition (25) divides the reaction space into an oxidation chamber and a sludge condensation chamber, that each perforated plate (28) on its underside with one of the air bubbles for uniform application of the sludge uniformly distributing rib profile (30, 31) is provided and that one of the escape of air bubbles with the deposited Gas-preventing device and a clarification stage (20) for the clear water separated from the heat-treated sludge are provided. 5. Plant according to claim 4, characterized in that the preventing the escape of air bubbles with the separated gas Device has at least one dehumidifier (32) with at least one wire layer. 6. Plant according to claim 5, characterized in that the device preventing the escape of air bubbles also includes a heating coil (34). 7. Plant according to claim 5, characterized in that the clarification stage (20) for the separated clear water at least includes an aeration tank in which the separated clear water is treated in the activated sludge process, and at least one settling tank. 8. Plant according to claim 4, characterized in that the clarification stage (20) for the separated clear water has a first Aeration stank (41) for treating the separated clear water in the activated sludge process, as well as a first Settling tank (42), a second aeration tank (44) for Mixing the treated wastewater with raw wastewater and 709838/0846 - 3 - 2711OAO one-time treatment of the mixture in the activated sludge process and a second settling tank (45). 9. Plant according to claim 4, characterized by a deodorization stage (21) with a deodorization tower (46) for
Odor removal of the malodorous gas occurring in the overall system using ozone and through a tower (49) which depletes the remaining ozone in the exhaust gas of the Deodorxerungsturms (46), in which the wastewater from a desulfurization tower (53), which is used for the removal of a Combustion stage (19) containing sulfuric acid is used, with the deodorized, ozone-treated gas is coated. 7n9838 / nfW, ß