WO2014030874A1 - Apparatus for pre-treating waste activated sludge and method for pre-treating waste activated sludge using same - Google Patents

Abstract

The present invention relates to an apparatus for pre-treating waste activated sludge that is generated in biological treatment tanks of sewage treatment plants and waste water treatment plants, and a method for pre-treating waste activated sludge using same. The apparatus for pre-treating waste activated sludge that solubilizes sludge includes: a first sludge storage tank that accommodates sludge to be treated; a high-pressure pump that introduces the sludge from the first sludge storage tank into a cavitation chamber at a pressure of between 7 bars and 560 bars; the cavitation chamber that has an orifice so that cavitation is generated while the high-pressure sludge discharged from the high-pressure pump passes therethrough; a Venturi section that has an ozone injection unit which injects ozone into the sludge discharged from the cavitation chamber; and a second sludge storage tank that is disposed on a downstream side of the Venturi section to store the treated sludge.

Description

Waste activated sludge pretreatment device and waste activated sludge pretreatment method using same

The present invention relates to a waste activated sludge pretreatment device generated in a biological treatment tank of sewage and wastewater treatment plants and a method for pretreating waste activated sludge using the same.

Waste activated sludge or excessive sludge, which is continuously generated in biological treatment tanks of sewage and wastewater treatment plants, is one of the representative organic wastes. Until now, these organic waste activated sludges have been treated by various methods such as landfilling, incineration, sea dumping, composting, auxiliary fueling, carbonization, etc., but most sewage and wastewater treatment plants have adopted the most cost-effective method of treatment. For this reason, a large amount of organic waste activated sludge has been dumped in the sea, sprinkled on land or landfilled all over the world. In Korea, more than 70% of sewage sludge has been disposed of by dumping at the end of 2006, since direct landfilling of organic waste sludge was banned in 2003. However, by joining the London Convention, an international environmental convention, such sea dumping was totally banned. Therefore, in the future, all of this organic waste sludge must be disposed of properly in land.

Against this backdrop, the future solution is to reduce sludge generation by itself, to recycle it as compost or cover material or auxiliary fuel, and to recover energy sources such as methane (CH ₄ ) through anaerobic digestion. Emerging into the room. In order to implement these methods, waste activated sludge must be properly pretreated. Currently developed technologies are still insufficient in terms of efficiency and cost.

In order to properly pretreat the waste activated sludge, it is important to understand the structure of activated sludge floc. Activated sludge flocs are lumps of microorganisms frozen together and are connected to each other through extracellular polymeric substances (EPS) (see Korean Patent Registration No. 10-0948494 FIG. 1).

In order to reduce waste activated sludge fundamentally, these sludge floc structures must be broken and the cell walls must be broken to allow the release of microbial components. The treated sludge is then fed back into the biological treatment tank or used as a carbon source in the advanced treatment process to remove nitrogen or phosphorus, thus making it possible to zero the waste activated sludge discharged from the wastewater treatment plant. In addition, in order to be recycled by composting, the water content must be lowered to less than 60% after dehydration. In this case, the pore water and some internal water of cells around the activated sludge should be removed. There is a limit that only free water can be removed only by the commonly used mechanical dehydration method. Therefore, other alternatives are needed, and suitable alternative methods should be techniques that can destroy such activated sludge floc structures and break cell walls. In the case of sludge treatment through anaerobic digestion, when the anaerobic digestion efficiency is increased, the solids are converted into biogas, which can recover a large amount of energy source, and consequently, the amount of sludge to be disposed of eventually decreases. You get an effect. Therefore, a pretreatment technique is required to increase the extinguishing efficiency. For this purpose, the amount of organic matter present as a solid and the amount of dissolved organic matter must be increased. This is possible only when the activated sludge floc structure is broken as described in the above two methods, and at the same time, the microbial cell wall is destroyed to release the intracellular material to the outside.

So far, waste activated sludge pretreatment has been tested and developed such as ultrasonication, high temperature heat treatment, ozone oxidation, cavitation treatment, alkali treatment, enzyme treatment, mechanical treatment, acid treatment, microbial treatment, wet oxidation process, vacuum treatment, etc. (Nam Gung-cheol, quoted from the 2008 KOSEN Expert Review).

Ozone oxidation of sewage sludge destroys the cell walls of the sludge reacted with ozone, releasing substances inside the cells (COD components). In addition, polysaccharides, proteins, lipids, and the like react with ozone to be converted to low molecular weight compounds. If the ozone dose is high enough, intracellular substances can be converted to carbon dioxide and water and mineralized. Waste activated sludge treatment using ozone can be divided into treatment for sludge reduction and pretreatment of anaerobic digestion (Korean Patent Registration No. 10-0928972). In the sludge reduction treatment, it was reported that an ozone injection of 0.05 kgO ₃ / kg TSS resulted in a sludge reduction effect of 19-35%. When applied to anaerobic digestion pretreatment, digestive sludge reduction of about 10% was obtained. In addition, the ozone dose was increased from 0.03 kgO ₃ / kgTSS to 0.06 kgO ₃ / kgTSS, increasing the emission of soluble COD from 11% to 16%. However, it has been reported that after the anaerobic digester, the COD of the effluent is increased and the cost is higher than the sludge reduction amount. In one study, the payback period for ozone pretreatment was estimated to be about six years. On the other hand, as a solution to this problem, it was reported that the closed loop ozone oxidizer in the medium temperature digester after ozone pretreatment was able to obtain much better gas production and COD reduction compared to the amount of ozone injection (Nam Gung Kyu, 2008 KOSEN Expert Review) Requoted from).

Hydrodynamic cavitation (HC) differs in ultrasonic cavitation and principle, but shows similar characteristics in its effect. HC is produced through turbulent flow of liquids, and often occurs when there is a large pressure difference in the flow of liquids. For example, if the device is made to pass through an orifice with a small cross-sectional area while moving the fluid at high pressure in a pipe with a constant cross-sectional area, there is a large pressure difference at the discharge portion of the orifice, which causes cavitation immediately after the discharge portion. This happens. Another example is a device that allows a fluid passing through an orifice to meet a blade. The orifice shape is not spherical but excellent in elliptical shape. In this case, as the blade vibrates, the cavitation can be caused very clearly and effectively. On the other hand, unlike the cavitation through one orifice, passing the fluid through a plurality of orifices can increase the cavitation effect. Variables affecting HC include the temporal factors of cavitation, along with pressure, flow rate, and cavitation chamber design. The pressure at the orifice inlet, the restoring pressure at the orifice discharge, and the minimum pressure for the occurrence of cavitation are important, and it is essential for commercial applications to clarify the relevant time factors (Namung Kyu-cheol, Journal of the Korean Society of Civil Engineers, Vol. 55) 10, pp 50-55, 2007).

One study reported that the residence time of cavitation pretreated sludge could be drastically reduced from 13 days to 6 days when not treated at moderate anaerobic digestion. In addition, the treatment efficiency is reported to be considerably improved by adding the alkali treatment prior to the cavitation treatment in the sludge reduction effect, gas production amount, and the like (Korea Patent Publication No. 2001-0072106). This process has been commercialized in a process called MicroSludge ^™ (Canada) and has recently been applied to real scale plants. In this process, the concentrated sludge is alkaline treated using a rotary drum concentrator at pH 8.5-10 for about 1 hour, followed by cavitation at a high pressure of 12,000 psi. As a result, up to 80% of sludge solubilization was possible. At this time, the pH of the solubilized sludge changes to 6.8-7.4. It has been reported that mesophilic digestion of this treated sludge can reduce volatile solids by 18-78%. Another example of a commercially available cavitation process is the Biogest Crown Disintegration System (UK). This process uses a very high flow rate and performs three cavitation treatments before the sludge is introduced into the anaerobic digester. Another example of a commercialization process is Rapid Non-equilibrium Decompression (RND). This process takes advantage of the phenomenon that CO ₂ dissolved due to supersaturation under high pressure rapidly expands with the pressure drop, thereby destroying the cell wall. The advantage of this process is that CO ₂ can be reused and energy costs are low, resulting in a payback period of less than two years.

In order to increase the overall efficiency of sewage sludge treatment, as described above, a process and apparatus are needed to effectively disassemble the structure of the sludge floc and to attack and destroy the cell walls of the microorganisms so that intracellular materials and internal water are released to the outside. Do. Cavitation and ozonation technologies provide an effective means of achieving this goal and, when used together, provide excellent synergy. Therefore, by integrating these technologies effectively and pretreating the waste activated sludge, a process and apparatus have been introduced that can reduce sludge reduction, improve sludge dewatering efficiency, and improve digestion efficiency (Korean Patent Registration No. 10-0948494). However, there is still a need for a sludge pretreatment process that can further improve sludge reduction, dewatering capacity, and anaerobic digestion efficiency with a simpler process.

In particular, in the existing cavitation-ozone process, the ozone was treated in a separate contact tank, so the pump capacity for injecting ozone had to be large, and the ozone contact tank had a limitation in uniformly solubilizing the organic sludge in the treatment of a large amount of organic sludge. have.

Accordingly, the present invention combines a physical treatment using cavitation with a chemical treatment using ozone in the pretreatment to solubilize the sludge, the operation cost is lower, the energy efficiency is simpler, and the device that maximizes the efficiency of the sludge solubilization, namely reduction, To improve the sludge dewatering efficiency and high anaerobic digestion efficiency sludge pretreatment device.

It is another object of the present invention to provide a method for pretreating sludge using the apparatus.

The present invention, in order to achieve the above technical problem, in the pretreatment apparatus for solubilizing waste activated sludge,

A first sludge reservoir containing the sludge to be treated;

A high pressure pump for introducing sludge from the first sludge reservoir into a cavitation chamber at a pressure of 7 bar to 560 bar;

A cavitation chamber having an orifice to allow cavitation to be generated while the high pressure sludge discharged from the high pressure pump passes;

A venturi unit having an ozone injection unit for injecting ozone into the sludge discharged from the cavitation chamber; And

It provides a waste activated sludge pretreatment apparatus comprising a second sludge storage tank for storing the treated sludge installed downstream of the venturi.

According to a preferred embodiment of the present invention, the venturi unit may be configured with one to ten venturi tubes connected in series.

According to a preferred embodiment of the present invention, the ozone injection portion connected to the venturi tube may be connected to the neck of the narrowest cross-sectional area of the venturi tube.

According to a preferred embodiment of the present invention, the pressure of the sludge introduced into the cavitation chamber from the first sludge reservoir is more preferably 7bar to 560bar, most preferably 10bar to 420bar.

According to a preferred embodiment of the present invention, the apparatus of the present invention may further include an ozone contact tank for ozone treatment of sludge discharged from the venturi portion between the downstream of the venturi portion and the second sludge storage tank.

According to a preferred embodiment of the present invention, at the front or rear end of the first sludge storage tank, it may further include a filtration tank for filtering foreign substances of a predetermined size or more from the sludge to be treated.

According to yet another aspect of the present invention, the apparatus comprises the step of ozone treatment with cavitation generation by passing the sludge to be treated through a venturi tube having a high pressure cavitation chamber and an ozone injection section using the apparatus. Waste activated sludge pretreatment methods are provided.

According to a preferred embodiment of the present invention, the waste activated sludge may be treated with alkali, hydrogen peroxide, or alkali and hydrogen peroxide before being introduced into the venturi part.

The apparatus according to the present invention maximizes the cavitation effect by placing a cavitation chamber by an orifice at the rear of the high pressure part in solubilizing the sludge by using a high pressure cavitation device, and then puts a venturi part to introduce ozone by dispersing and introducing ozone. It can save and also get good stirring effect. Therefore, compared with the case where only the ozone-only mixing treatment or the low pressure cavitation is performed using the venturi unit, the sludge reduction, the sludge dewatering efficiency and the anaerobic digestion efficiency are improved. In addition, even when using an additional ozone contact tank, the size of the pump and tank can be made small.

1 is a schematic diagram of a waste activated sludge pretreatment apparatus according to a first embodiment of the present invention.

2 is a schematic diagram of a waste activated sludge pretreatment apparatus according to a second embodiment of the present invention.

3 is a schematic diagram of a waste activated sludge pretreatment apparatus according to a third embodiment of the present invention.

4 is a schematic view showing various forms of orifices.

5 is a view showing the solubilization effect of the venturi tube.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a schematic diagram of a pretreatment apparatus according to a first embodiment of the present invention. As shown, the waste activated sludge pretreatment apparatus of the present invention includes a first sludge storage tank 1, a high pressure pump (HPP) 2, a cavitation chamber 4 having an orifice 3, and an ozone injection unit 6 therein. A venturi tube 5 and a second sludge reservoir 7. That is, the sludge to be treated is treated by hydraulic cavitation from the first reservoir 1 via a high pressure cavitation unit 4 by a high pressure pump 2 and then introduced into the venturi tube 5. At this time, ozone is injected into the ozone injection unit 6 of the venturi tube 5, and ozone and sludge are effectively mixed and further processed by a relatively weak hydraulic cavitation while passing through the venturi tube 5.

Stepwise, in the high pressure cavitation device 4 with the orifice 3, the sludge is divided into individual cells, mainly by dissolving the floc structure and breaking the bond formed by the extracellular fibrous materials. Ozone is injected from the venturi part 5 and mixed with the sludge and undergoes a weak cavitation phenomenon, and gas-liquid mixing is effectively performed, and ozone destroys the sludge by oxidizing the cell walls and extracellular tissues of the individualized cells through oxidation reaction. Solubilization.

The pressure of the high pressure pump 2 is preferably 7 bar to 560 bar, more preferably 10 bar to 420 bar. If the pressure is too low, the process may not proceed properly due to the pressure drop loss in the venturi portion, and if the pressure is too high, there may be a problem that the cost is increased by using expensive equipment. If necessary, the pump may be further used in front of the high pressure pump 2 to smoothly operate the high pressure pump.

In the present specification, the cavitation chamber refers to a region in which high pressure cavitation is formed from an orifice to a front end of the venturi portion. As shown in FIG. 4, the orifice 3 of the cavitation chamber 4 may have one or several openings and is not particularly limited. Sludge sucked into the orifice 3 by the high-pressure pump 2 is a cavitation phenomenon such as a shock wave is generated as the bubbles generated by the expansion portion rapidly collapses.

The ozone injection section 6 is formed in the neck portion of the venturi tube 5 in which the cross-sectional area of the venturi tube 5 is drastically reduced, and when the fluid passes through the portion, the velocity of the fluid increases rapidly and thus the fluid The pressure of is greatly reduced. In other words, since negative pressure is generated, ozone is naturally inhaled, so there is no need to operate a separate pump for ozone injection. In addition, the gas in the dissolved state in the fluid is released from the fluid or the phase change of water occurs to form cavities (cavities) is generated.

This hydrodynamic cavitation phenomenon has been used in other technical fields, but the use of a high pressure cavitation device and an ozone injection using a venturi tube eliminates the need for an ozone contact tank at all, or greatly reduces the size of the ozone contact tank. Gas-liquid mixing can be achieved. This can significantly improve energy efficiency and reduce costs.

In addition, in the pretreatment apparatus of the present invention, as shown in FIG. 1, only one venturi tube 5 having the ozone injection unit 6 is connected in series. However, two or more venturi tubes 5 are connected in series to form the venturi unit. In this case, the solubilization efficiency can be further improved while the sludge passes through each venturi tube. In particular, each venturi tube may be configured to be detachably connected to easily adjust the number of venturi tubes as needed. In addition, although ozone may be injected into each venturi tube, only some of them may be injected.

2 is another embodiment of the present invention. In addition to the first sludge reservoir 1, the high pressure pump 2, the cavitation chamber 4 with the orifice 3, the venturi part 5 including the venturi tube and the second sludge reservoir 7 as shown. If the sludge to be treated contains a large solid, it may further include a filtration tank 10 for filtering it. In FIG. 2, although the filtration tank 10 is installed in the front end of the 1st sludge storage tank 1, it can also be installed in the rear end. Although not shown, it may be provided with a means for promoting the solubilization of the sludge, that is, a means for adding before introduction into the venturi portion 5, such as alkali or hydrogen peroxide.

In another embodiment, as shown in FIG. 2, an ozone contacting tank 20 may be provided to further ozonate the sludge flowing out of the venturi part, and an additional ozone contacting tank 20 may be provided. The size or pump capacity of the reactor may also be much smaller than in the case of not using the device according to the invention, thus making the installation compact.

In the ozone contact tank 20, the sludge and ozone may be contacted in two ways. One is to use a gas-liquid mixing pump and the other is to use an injector / venturi. In the former case, the sludge in the contact tank 20 is removed by the gas-liquid mixing pump 30, and ozone is injected therein, and the sludge and ozone are mixed through the gas-liquid mixing pump 30 and put back into the ozone contacting tank 20. (See FIG. 2), the latter removes the sludge of the ozone contact tank 20 by using the liquid transfer pump 40 and after mixing the injecting ozone to the neck while passing the sludge passes through the injector / venturi (50) It is a method to put back into the ozone contact tank 20 (see Fig. 3). Either method can be used effectively. Hereinafter, the embodiment of the present invention will be described in detail. However, this description does not limit the scope of the present invention, those skilled in the art can be easily substituted by those described in the specification and claims of the present invention, the equivalent range for which such substitution is obvious is within the scope of the present invention. Belongs.

Example 1

Sewage sludge samples were taken from a biofilm reactor (MBR) pilot facility (treatment capacity: 300 tons / day, average TSS: 10,000 mg / L) installed in the sewage treatment plant. A device (1 venturi tube in series connection) as shown in Figure 1 was used, specific specifications are as follows.

1st sludge reservoir capacity: 1.5 m ³

High pressure pump flow rate: 17 L / min

High pressure pump pressure: 150 bar

Orifice cross section: 0.785 mm ²

Venturi tube cross section: 7.065 mm ²

Ozone injection volume: 120mg / L

Filtration tank specification: stainless steel screen with 1.0mm mesh (screen area: 0.196m ² )

Ozone contact tank and pump specifications: 1.2m ³ size cylindrical contact tank with bubble breaker on top, 2HP 380V gas-liquid mixing pump (Shinpung Naesan pump)

The ozone generator is a water-cooled device (SW-50 of Sewang C-Tech), and the ozone generating capacity is up to 50g-O ₃ / hr The raw material oxygen was pure oxygen (99.99%) stored in a high pressure vessel.

The treated sludge was analyzed in the following manner.

① pH-Each sample was measured for pH using a pH meter.

② Temperature-Each sample was measured for temperature using a thermometer.

③ Suspended solids (SS; suspended solids)-After washing the glass fiber filter (GF / C) with purified water in advance, place it on a watch plate, dry it for 2 hours in a dryer at 105-110 ℃, cool it in a sulfuric acid desiccator, The weight was precisely weighed and attached to the filter. Aspirate the sample with a suitable amount, filter it, and wash the filter wall and filter residue with water several times, remove the glass fiber with a pincent and place it on a watch dish, paying attention to a pincent, and dry it in a dryer at 105-110 ° C for 2 hours. The mixture was allowed to stand in a sulfuric acid desiccator, allowed to cool, and then weighed accurately as a constant weight. The difference in the weight of the glass fiber filter before and after filtration was calculated to be the amount of suspended solids.

④ SCODcr-After filtering the sample with glass fiber filter (GF / C), the filtered solution is injected into 2mL of water CODcr analysis kit and reacted at 150 ℃, and then SCODcr is analyzed using HS-2300Plus water analyzer (Humas, Korea). Analyzed.

Comparative Example 1-Only High Pressure Cavitation

When only high pressure cavitation (200bar) is performed without ozone treatment, reference may be made to the experimental example described in Korean Patent Registration No. 10-0948494. The result is as follows.

Table 1

	enemy	1 min	2 minutes	5 minutes	10 minutes
Sludge Contact Count (times)	-	0.8	1.6	4	8
pH	7.14	7.12	7.11	7.03	6.91
Temperature (℃)	26	32	36	44	55
SCODcr (mg / L)	43.2	262.49	325.76	532.29	1070.81
SCODcr / SS Ratio (× 1000)	5.02	29.17	40.72	66.54	133.85

Comparative example  2- Venturi tube  Ozone treatment with ozone contact pump without use

Experimental results in the case of treating only ozone with an ozone contact pump without high pressure cavitation can also refer to Korean Patent Registration No. 10-0948494. The experimental results according to the ozone input amount are as follows.

(2-1) ozone dose 30 g / hr

TABLE 2

	enemy	1 min	5 minutes	10 minutes
Ozone sludge contact count (times)	-	One	5	10
pH	7.14	6.63	6.46	6.19
Temperature (℃)	26	27	30	33
SCODcr (mg / L)	37.69	107.91	350.97	557.96
SCOD / SS ratio (× 1000)	5.38	15.42	87.74	139.49

(2-2) ozone dosage 50g / hr

TABLE 3

	enemy	1 min	5 minutes	10 minutes
Ozone sludge contact count (times)	-	One	5	10
pH	7.14	6.44	6.19	5.75
Temperature (℃)	26	28	30	35
SCODcr (mg / L)	37.69	278.49	616.89154.22	907.46
SCOD / SS ratio (× 1000)	5.38	46.42	154.22	302.49

Increasing the amount of ozone from 30g / hr to 50g / hr increased the destruction of sludge, which increased SCOD and increased SCOD / SS.

Comparative Example 3 Cavitation and Ozone Treatment without Venturi Tube

Experimental results in the case of performing ozone treatment by cavitation and ozone contact pump can also refer to Korean Patent Registration No. 10-0948494. The experimental results according to the ozone input amount are as follows.

(3-1) ozone dose 30 g / hr

Table 4

	enemy	1 min	5 minutes	10 minutes
Ozone sludge contact count (times)	-	One	5	10
pH	7.14	6.53	6.32	6.18
Temperature (℃)	26	30	32	35
SCODcr (mg / L)	37.69	404.28	719.74	1065.90
SCOD / SS ratio (× 1000)	5.38	67.38	179.94	355.30

(3-2) ozone dosage 50g / hr

Table 5

	enemy	1 min	5 minutes	10 minutes
Ozone sludge contact count (times)	-	One	5	10
pH	7.14	6.42	6.17	5.76
Temperature (℃)	26	28	32	35
SCODcr (mg / L)	37.69	549.99	924.69	1242.10
SCOD / SS ratio (× 1000)	5.38	78.57	231.17	414.03

Comparison of Treatment Performance with Unit Ozone Dose

In the case of using the apparatus of Example 1, Comparative Examples 2 and 3 subjected to ozone injection, the SCODcr increase ratio per unit ozone dose is compared as follows.

Table 6

division		Ozone Injection Concentration	SCODcr increase	SCODcr increase rate per unit ozone dose	Remarks (throughput amount, ozone generation amount, ozone injection time)
Example 1		120mg / L	1200 mg / L	10	1m 3 , 50g / hr, 2.4hr
Comparative Example 2	One	250 mg / L	520mg / L	2.08	20L, 30g / hr, 10min
	2	417mg / L	870 mg / L	2.09	20L, 50g / hr, 10min
Comparative Example 3	One	250 mg / L	1,028 mg / L	4.11	20L, 30g / hr, 10min
	2	417mg / L	1,204 mg / L	2.89	20L, 50g / hr, 10min

From Table 6 above, the high pressure as in the present invention is compared with the case of using an ozone contact pump without using a venturi tube (Comparative Example 2) or when using a cavitation and an ozone contact pump (Comparative Example 3). In the case of using a venturi tube after cavitation, it can be seen that a much better SCODcr increase, that is, a sludge solubilization effect, can be obtained compared to the same ozone dose.

Comparative Example 4 Only Low Pressure Cavitation Using Venturi Tube

FIG. 3 of Korean Patent Registration No. 10-0866620 of Samchang Enterprise shows the effect of the number of venturi tubes on the sludge solubilization efficiency (see FIG. 5).

According to FIG. 5, after 20 hours of treatment with one venturi tube, an SCOD value of 1,600 mg / L was shown. On the other hand, when two venturi tubes were connected in series, the SCOD increased with the start of operation, and the SCOD concentration reached 2,700 mg / L after 14 hours of treatment, and since then, the SCOD increase was minimal. After 20 hours of treatment, the increase in SCOD was about twice that of two venturi tubes in series. This shows that by connecting two Venturi tubes in series, the area of cavitation can be doubled.

In contrast to the present invention, Comparative Example 4 shows very slow processing performance. In Comparative Example 4, the SCOD value was 1,600 mg / L when treated with one venturi tube for 20 hours, and the SCOD increase was obtained when the treatment was performed for 10 hours with two. On the contrary, in the present invention, the SCOD value reaches 1,550 mg / L after the high pressure cavitation through two stages of low pressure cavitation, and the treatment time is within 1 minute to 3 minutes. This shortening of time results in a small space, a small area for the treatment facility, and a compact facility, thereby reducing facility investment and operation management costs.

Comparative Example 5-After Ozone Injection Using PFR Reactor

US Pat. No. 7,695,622 to Praxair Technology, Inc. (April 13, 2010) proposes a technique for reducing the amount of ozone injected compared to other previous documents in treating sludge with ozone for sludge reduction. In this way, ozone is injected at a single or multiple injection points and then linked to a plug flow reactor. However, it is difficult to compare directly because it does not present an SCOD value indicating the solubilization of the sludge.

However, in the present invention that ozone treatment through cavitation, ozone is added to about 100mg / L ~ 150mg / L. When the sludge with TSS 10,000mg / L was placed in a continuous mixing reactor (CSTR) and ozonated using one venturi tube, the SCOD growth rate increased from 400mg / L to 1200mg / L at the ozone injection rate of 120mg / L. Increased to 1600 mg / L when cavitation was included. In the present invention, the sludge reduction rate is 40% under this condition, and compared with 0.05 kg O ₃ consumed / kg Sludge reduced shown in Comparative Example 5, the ozone treatment efficiency is about twice as high as 0.025 kg O ₃ consumed / kg Sludge reduced. It can be seen that. As a result, it can be seen that the sludge reduction effect of the present invention is about 2 times for the same ozone input.

As described in the above Examples and Comparative Examples, the sludge solubilization rate is significantly lower in Comparative Example 1 and Comparative Example 4, in which only cavitation was performed without ozone treatment, as compared with the ozone treatment. In addition, in the case of using the ozone contact pump without using the venturi tube as in the case of Comparative Example 2 and Comparative Example 5 or using the PFR reactor after the ozone injection through the venturi tube, the treatment rate is lower than in the present invention. In addition, when using a venturi tube after high-pressure cavitation as in the present invention, it is possible to obtain a much better SCODcr increase, that is, a sludge solubilization effect compared to the same ozone dose, than when using a general ozone contact pump without using a venturi tube after a high-pressure cavitation.

The apparatus according to the present invention maximizes the cavitation effect by placing a cavitation chamber by an orifice at the rear of the high pressure part in solubilizing the sludge by using a high pressure cavitation device, and then puts a venturi part to introduce ozone by dispersing and introducing ozone. It can save and also get good stirring effect. Therefore, compared with the case where only the ozone-only mixing treatment or the low pressure cavitation is performed using the venturi unit, the sludge reduction, the sludge dewatering efficiency and the anaerobic digestion efficiency are improved. In addition, even when using an additional ozone contact tank, the size of the pump and tank can be made small.

Claims (7)

1. In the pretreatment apparatus for solubilizing waste activated sludge,

   A first sludge reservoir containing waste activated sludge to be treated;

   A high pressure pump for introducing sludge from the first sludge reservoir into a cavitation chamber at a pressure of 7 bar to 560 bar;

   A cavitation chamber having an orifice to allow cavitation to be generated while the high pressure sludge discharged from the high pressure pump passes;

   A venturi unit having an ozone injection unit for injecting ozone into the sludge discharged from the cavitation chamber; And

   And a second sludge storage tank configured to store the treated sludge installed downstream of the venturi part.
2. The method of claim 1,

   The venturi unit waste activated sludge pretreatment apparatus, characterized in that 1 to 10 venturi tube is connected in series.
3. The method of claim 1,

   Ozone injection unit connected to the venturi tube waste activated sludge pre-treatment device, characterized in that the cross-section of the venturi tube is connected to the narrowest neck.
4. The method of claim 1,

   Between the downstream of the venturi section and the second sludge reservoir. Waste activated sludge pretreatment apparatus further comprises an ozone contact tank for ozone treatment of the sludge discharged from the venturi.
5. The method of claim 1,

   A waste activated sludge pretreatment apparatus further comprising a filtration tank for filtering foreign substances of a predetermined size or more from the sludge to be treated before or after the first sludge storage tank.
6. A method of pretreating waste activated sludge using the apparatus of any one of claims 1 to 5.
7. The method of claim 6,

   The waste activated sludge is treated with alkali, hydrogen peroxide, or alkali and hydrogen peroxide before being introduced into the venturi section.

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