KR101737994B1 - Dewatering system for high efficiency of sludge dewatering - Google Patents

Abstract

The present invention relates to a sludge dehydration system, and to a sludge dehydration method using the same, which utilizes oystershell and waste activated carbon, which are waste resources, so as to increase dehydration efficiency of the sludge. Moreover, it is possible to perform efficient dehydration treatment of various sludge, without being greatly affected by various kinds of sludge including water purification plant sludge, waste water disposal plant sludge, and the like, and it is also possible to perform various kinds of sludge separately or to perform mixed integral treatment.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dewatering system for improving the dewatering function of a sludge by using waste resources, and a dewatering system for high-

The present invention improves the dehydration efficiency of the sludge by using waste oyster shells and waste activated carbon which are waste resources, thereby enabling effective dehydration without being greatly influenced by various types of sludge including water purification plant sludge and wastewater treatment plant sludge, To a sludge dewatering system capable of individually treating mixed sludge or in a mixed manner and a sludge dewatering method using the sludge dewatering system.

Economic development and improvement of life have resulted in increase of domestic sewage and wastewater. Therefore, sewage and wastewater treatment facilities to prevent pollution of rivers and rivers have inevitably increased.

Sludge is left after the process of precipitation in the process of wastewater treatment. This sludge is finally landfilled or incinerated, and is dumped into the ocean.

Currently, it is prohibited to land directly in the landfill after dehydration at the sewage treatment plant, and therefore there is a need for research on a large and growing amount of sludge treatment. Producing low-moisture dehydrated sludge is an important issue in order to reduce the disposal cost of the sludge to 50% of the total sewage treatment cost.

Dewatered sludge with low water content is easier to handle than liquid or concentrated sludge, and can reduce the transportation cost due to volume reduction and increase the energy content upon incineration. It can also reduce the consumption of modifiers before composting and can significantly reduce odor and perishability. Therefore, a method for improving the dewatering efficiency of sludge is attracting attention.

Sludge dewatering aims at reducing the concentration of sludge by further reducing the amount of sludge, thereby facilitating the treatment of the sludge and reducing the disposal cost.

The dewatering method is divided into natural and mechanical methods. Natural methods include sand drying method and lagoon method. Mechanical method includes vacuum filter using vacuum suction force, filter press using pressure applying filtration membrane, compression of belt Belt Press using pressure, and Centrifuge using centrifugal force. Mechanical methods are mainly used nowadays because natural processes have fewer sludge throughputs, decrease in effective land and groundwater pollution, etc. However, there is a limitation in lowering the moisture content of sludge only by mechanical force, And the like.

In connection with dewatering of sludge, the 'sludge dewatering device and sludge dewatering system using the sludge dewatering device' of the registered patent No. 10-0329318 (registered date 2002.03.07), 'dehydration drying system' of Registration No. 10-0368682 'Sludge squeezing and dewatering system contained in river water' of registered patent 10-1146792 (registered date 2012.05.09), 'Continuous dredging dewatering system' of registered patent No. 10-1115238 (registered date 2012.02.01), registered patent 10-1169976 (Registered on Jul. 25, 2012), a continuous sludge dewatering device of a water purification system, and a dewatering device of a solid-liquid separation system of a registration room 20-0416677 (registered date 2006.05.11) However, no technique has been disclosed for improving the dehydration efficiency of the sludge by recycling the waste oyster shell and the waste activated carbon. Accordingly, the applicant of the present invention has accomplished the present invention to provide a sludge treatment system and a treatment method which have a sludge treatment cost reduction effect and an environmental pollution improvement effect due to recycling of resources, and a high treatment efficiency by efficiently recycling waste resources .

Korean Registered Patent No. 10-0329318 (registered on March 23, 2002) Korean Registered Patent No. 10-0368682 (Registration date 2003.01.07) Korean Registered Patent No. 10-1146792 (Registration date 2012.05.09) Korean Registered Patent No. 10-1115238 (Registration date 2012.01.01) Korean Registered Patent No. 10-1169976 (registered on July 25, 2012) Korea Registered Office 20-0416677 (Registered on May 5, 2006)

The present invention provides a sludge dewatering system capable of utilizing an oyster shell and waste activated carbon, and also provides a sludge dewatering method using the sludge dewatering system,

It is possible to individually and integrally treat various kinds of sludge by minimizing the occurrence of difference in dewatering efficiency depending on the kind of sludge, and thus it is possible to reduce the cost of sludge treatment, sludge treatment, It is an object of the present invention to provide a dewatering system that improves the dewatering function of sludge by utilizing resources and a sludge dewatering method using the same.

In order to achieve the above object,

The present invention relates to a system for sludge dewatering,

A sludge pretreatment unit for pretreating the sludge thermally and chemically in order to improve the dewaterability of the sludge;

A dewatering modifier injecting unit injecting a dewatering modifier to improve dewaterability of the sludge that has undergone the pretreatment through the sludge pretreatment unit;

A dehydrating auxiliary agent injecting unit injecting waste activated carbon as a coagulation assistant into the sludge injected with the dewatering improving agent;

A sludge concentration unit for removing a portion of the liquid contained in the sludge into which the waste activated carbon is injected to increase the solid matter content of the sludge;

And a dehydrating unit for ultimately dehydrating the concentrated sludge through the sludge thickening unit to improve the dehydration function of the sludge.

The dewatering system according to the present invention has an advantage that the dewatering property of the sludge is very high by constituting the system so as to maximize the dewatering efficiency irrespective of the type of the sludge.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing the entire structure of a dehydrating system according to the present invention; FIG.

Hereinafter, the detailed contents of the above-described technical configuration will be described with reference to the drawings.

The types of sewage sludge generated during the sewage treatment process include primary sludge (PS) generated in the primary settling basin of the sewage treatment process, activated sludge (WAS) generated in the biological treatment process, raw sludge and active The digested sludge (DS), which is decomposed organic matter in the anaerobic digestion tank, and the dewatered cake (DC), which is finally generated in the dehydration process, Respectively.

As shown in FIG. 1, the dewatering system 1 according to the present invention includes a sludge pretreatment unit 10 for pretreating the sludge thermally and chemically in order to improve the dewaterability of the sludge.

A dewatering modifier injecting unit 20 for injecting a dewatering modifier to improve dewaterability of the sludge that has undergone the pretreatment process through the sludge pretreatment unit 10;

A dewatering aid injecting unit 30 for injecting waste activated carbon as a coagulation aid into the sludge injected with the dewatering improver;

A sludge concentration unit 40 for removing a portion of the liquid contained in the sludge into which the waste activated carbon is injected to increase the solid matter content of the sludge;

And a dewatering unit (50) for finally dehydrating the concentrated sludge through the sludge thickening unit (40).

Sludge types include 4 to 10% solids, gray sludge with high tackiness; Surplus sludge having a solid soil content of 0.8 to 2.5% and a brown soil smell; Mixed sludge produced by mixing raw sludge and excess sludge with 0.5 ~ 1.5% solids in the pre-concentration tank; A concentrated sludge which is a sludge reduced before digestion of raw, surplus, and mixed sludge of 2.0 to 8.0% of solids; Concentrated by anaerobic or aerobic digestion with 2.5 to 7.0% solids. Decomposed sludge (mostly anaerobic digestion), which contains a large amount of gas from dark brown to black-brown, and when the sludge is dried, the gas is blown and ground; Dehydrated sludge to reduce moisture, transport and incineration of sludge with 20 to 40% solids, and facilitate final disposal; .

 Sludge generated as a treatment by-product in sewage treatment plant and water treatment plant has a high treatment cost, and since disposal cost or incineration cost is also large, treatment cost in sludge treatment takes a great deal of weight. Therefore, in order to reduce the disposal cost of sludge, it is best to reduce the water content to reduce the sludge.

The present invention relates to a dewatering system in which the water content of the sludge is minimized to enhance the functionality of sludge reduction, and the constituent elements of the dewatering system according to the present invention will be described in detail.

Sludge pretreatment can improve the efficiency of the total anaerobic digestion reaction by increasing the utilization of the anaerobic microorganism substrate by removing the rate step by eluting the intracellular matrix by destroying the cell wall of the microorganism by physical, chemical or biological methods have. It also facilitates the separation of moisture from solids as the water trapped in the cells or fine floc flows out.

That is, the sludge pretreatment unit 10 can efficiently remove moisture in the sludge whose dehydration efficiency is not improved by a general dehydration method such as mechanical dehydration by ultrasonic wave, ozone or thermal / alkali combination treatment, The water content of the water is reduced.

In the case of the ultrasonic wave preprocessing, ultrasonic wave preprocessing is performed at a frequency of 20 kHz and a maximum power of 120 to 400 W.

When the ozone pretreatment, an ozone generator (OZONIA four LAB2B LABORATORY OZONE GENERATOR), but using the air feed gas using pure oxygen, and the transmission amount is 2L / min, injection ozone concentration of ozone is fixed to 60mgO ₃ / LO ₂ Pretreatment is done.

In the case of the heat-alkali combination treatment, the pH is adjusted to 11 by injecting 0.05 mg NaOH / mg SS into the sludge, and the thermal and alkali merging pretreatment is performed for 2-3 hours at a temperature of 75-85 ° C.

The water content in the sludge is classified into free water and coupled water based on whether it is associated with sludge particles. The free water is divided into free water and interstitial water based on whether the free water is limited within the structure of the sludge. The combined water is divided into surface water and bound water depending on the combination of sludge particles and water.

Among the four types of water, the free water and the void water can be removed by mechanical dehydration, but it is known that the surface water and the combined water can not be removed by mechanical dehydration. Therefore, the surface number and the bonding water require thermal and chemical pretreatment.

In the ultrasound pre-processing, ultrasound generally refers to sound waves having a frequency of 16,000 Hz or more. Ultrasonic waves are generated by piezoelectric materials such as quartz. When alternating charges of the same size and opposite direction are applied to both sides of the piezoelectric material, the material repeatedly expands and contracts. The piezoelectric material converts electrical energy into mechanical energy. The mechanical vibration generated at this time generates ultrasonic waves.

The pretreatment of sludge by ultrasonic waves is a method of destroying the microorganisms of the activated sludge, and utilizes acoustic cavitation phenomenon which occurs when ultrasonic waves are emitted from the surface of the ultrasonic vibrator.

When the fluid is ultrasonically irradiated, the formation and collapse of the cavitation bubble, which is the implosion phenomenon of the bubble, occurs. The temperature and pressure inside the collapsed bubble rise to about 5,000K and several hundred to several thousand atmospheres. Which can lead to thermal destruction of compounds present in cavitation bubbles and generation of highly reactive OH radicals. Since sewage sludge is composed of water and solid matter, the flocs are disassembled by ultrasonic decomposition, and the cells such as microorganisms are decomposed, and the physical and chemical destruction of the sludge from which the cell liquid is eluted becomes possible. Such ultrasonic wave pretreatment releases soluble carbohydrates and organic substrates, and generally has a cell destruction degree of 95% or more.

The removal of the organic matter by the ozone in the ozone pretreatment is oxidized by the direct reaction between the ozone and the soluble substance or by the OH radical generated when the ozone is decomposed in water. Since the sewage sludge is composed of organic materials, the sludge is decomposed by ozone and converted into dissolved organic matter. By oxidizing the cell walls of the sludge by the produced OH radical, the surface of the microorganism is damaged, do.

When the ozone injection amount is low in the ozone pretreatment, the turbidity of the ozone treatment solution increases due to the increase of the fine particles due to the ozone treatment. Therefore, the average particle size of the sludge is increased by injecting a certain amount of ozone, .

The heat and alkali combination treatment is a method of hydrolyzing the cells by adding alkali to the sludge. As a result, the same sludge solubilization ratio can be obtained even at a relatively low temperature as compared with a heat treatment requiring a high temperature.

When the sludge is heat-treated only, the hydrolysis rate of the sludge is small, but when the pH is increased by adding NaOH, the hydrolysis rapidly increases, and as a result, the dewaterability can be increased.

The sludge that has undergone the pretreatment in the sludge pretreatment unit 10 is transferred to the dewatering improver injecting unit 20 to inject the dewatering agent into the sludge.

In order to improve the dewaterability of the sludge, it is necessary to improve the dewaterability of the sludge and to improve the dewaterability. However, the sludge property, dewaterability parameter and mechanical dehydrator should be satisfied. It can be said that

The improvement of the properties of the sludge is intended to enhance the size of the sludge particles so as to promote the solid-liquid separation, thereby facilitating the concentration and dehydration. In this case, the factors that have an important influence on the improvement of the sludge include a large surface area and a fine Sludge particles.

The dewatering improver is obtained by subjecting naturally dried oyster shells to an electric furnace at 850 to 950 ° C for sintering for 1.5 to 2.5 hours, cooling the calcined oyster shell (CWOS), then pulverizing the powdered oyster shell with a ball mill, Sieve selection process,

A hydration reaction process of the waste oyster shell in which the calcined oyster shell powder and distilled water are mixed at a weight ratio of 1: 4 and then heated to Ca (OH) ₂ by heating for 5 to 8 hours,

The hydration-reacted waste oyster shell powder and ocher powder are mixed in a ratio of 6: 4 to 9: 1.

The mixing ratio of the dewatering agent and the sludge is 1 to 3 parts by weight based on 100 parts by weight of the sludge.

The dehydrating agent was 8.13 wt% SiO ₂ ; Al ₂ O ₃ 12.56 wt%; 1.53 wt% Fe ₂ O ₃ ; MnO 0.06 wt%; 0.63 wt% MgO; CaO 53.17 wt%; Na ₂ O 0.76 wt%; K ₂ O 0.43 wt%; TiO ₂ 0.18 wt%; P ₂ O _{5 and} 0.21 wt%, and the alkali metal component is uniformly contained in a large amount, and the surface is porous, so that the function as the flocculant is excellent and the dehydration efficiency can be increased.

The main component of the waste oyster shell is composed of Ca (37.8%), which is an alkaline metal ion applicable as a dehydration improving agent. The calcium oxide and calcium hydroxide treated with such an oyster shell can be used as a coagulant in a wastewater treatment plant, Adsorbents and the like. The chemical composition of the waste oyster shell used in the present invention is as follows: Al ₂ O ₃ 2.37 wt%; 0.38 wt% Fe ₂ O ₃ ; 0.02 wt% MnO; 0.48 wt% MgO; CaO 55.43 wt%; Na ₂ O 1.35 wt%; K ₂ O 0.42 wt%; TiO ₂ 0.04 wt%; And 0.39 wt% P ₂ O ₅ ;

The loess has a honeycombed structure and is loosely cemented by calcium carbonate, resulting in a porosity of 50 to 55%. Its size is 0.02 ~ 0.05mm and it contains coarse and neutral dust. The content of particles below clay size is usually 5 ~ 10%. The loess is classified into 5 types. The porosity increases (60%) with sandy loess, and clay minerals such as Kaolinte, illite, Montmorillonite are predominantly contained in clay soil.

The loess was ground with a ball mill and screened with a sieve having a particle size of 200 mesh. The ocher was evaporated and dried in a drying oven at 100 to 110 ° C for 20 to 25 hours and stored in a desiccator use. The composition of the yellow loess used in the present invention is 45.3 wt% of SiO ₂ ; 22.1 wt% Al ₂ O ₃ ; 12.8 wt% Fe ₂ O ₃ ; MnO 0.4 wt%; 1.3 wt% MgO; CaO 2.wt% 7; Na ₂ O 0.7 wt%; K ₂ O 1.1 wt%; TiO ₂ 1.3 wt%; P ₂ O ₅ 0.1 wt%.

The sludge that has passed through the dewatering improver injecting unit 20 is transferred to the dewatering auxiliary injecting unit 30 to inject waste activated carbon.

At this time, the amount of the activated carbon to be injected is 1 to 1.5 parts by weight based on 100 parts by weight of the total weight of the sludge containing the dehydrating agent.

The waste activated carbon is washed with distilled water several times to remove impurities and air-dried for 24 hours. The naturally dried waste activated carbon is first pulverized with a ball mill, and the pulverized activated carbon is passed through a 200 mesh sieve (75 μm).

The waste activated carbon selected by the sieve is evaporated and dried for 24 hours while maintaining 105 ° C in a dry oven.

The sludge having passed through the dehydrating auxiliary injection unit 30 is transferred to the sludge thickening unit 40.

The sludge thickening part 40 is provided with at least one thickening device selected from gravity concentration, float concentration, centrifugal concentration, gravity belt concentration, and rotary drum concentration. As a specific example, a multi-disc type concentrator may be used.

The ultimate goal of the treatment of sludge is to separate the sludge by solid-liquid separation, to increase the solid concentration of the discharged sludge, and to lower the moisture content of the sludge. At this time, it is used as a concentration device to remove a part of liquid from the sludge in the pre-stage of the final sludge dewatering process to increase the solid matter content of the sludge.

As a specific example, waste activated sludge is usually discharged from a secondary settler with a solids content of about 0.8%. This is concentrated to 4% solids content to reduce the sludge volume to 1/5.

The sludge having been subjected to the sludge concentration process in the sludge thickening section (40) is finally transferred to the dehydration section (50) and subjected to a dehydration process.

Sludge dewatering is affected by chemical conditions such as selection of coagulant, amount of injection and agitation strength, and hydraulic conditions, though there is some difference depending on the dewatering device.

The dewatering process for sludge dewatering can be divided into natural and mechanical methods. Natural methods include sand drying method and lagoon method. Mechanical methods include vacuum filtration using vacuum suction, Pressure Filter Press, Centrifuges using centrifugal force, Belt Press Filter using Belt pressing pressure, and so on.

In the present invention, dehydration can be effected effectively even when a general dewatering method is applied through a sludge pretreatment process, and a dewatering system is provided to maximize a dewatering rate through a process of charging and concentrating a sludge modifying agent. The dehydration process can be carried out by selecting a natural or mechanical method according to the site conditions.

The constitution of the dewatering device according to the concentrator may be composed of a multi-disk type concentrator + BELT PRESS dehydrator. In other words, a multi-disk type concentrator is installed at the front of the BELT PRESS dehydrator, and the final dehydration is performed through the concentration process, thereby increasing the flow rate of the inflow sludge as compared with before the concentrator is used.

Conventional Screw-Press type dewatering device is a device that concentrates and dewaterizes by using gravity and press-in pressure of screw, and sludge which is coagulated is conveyed to the back pressure plate by conveying action of Screw wing, The sludge is squeezed with a larger pressure and the sludge is squeezed from the outlet backing plate to the high pressure and then discharged.

Since the dehydrated filtrate flows out through the screen but the sludge particles form a brige in the hole, even the particles smaller than the screen interval can not easily flow out, and the speed of the screw can be adjusted to about 0.1 to 2 rpm according to the characteristics and dehydration speed of the sludge Therefore, it becomes dehydration without impossibility.

The dewatering system according to the present invention is industrially applicable because the dewatering system is constructed so as to maximize dewatering efficiency in the final dewatering step, minimizing the water content and minimizing the sludge weight.

1: Dehydration system
10: sludge pretreatment section
20: Dewatering improving agent injection part
30: dehydrating assistant injection unit
40: sludge thickener
50: dehydration part

Claims (5)

delete delete delete delete Sludge pretreatment step; Injecting a dewatering agent into the sludge after the pretreatment; Injecting a dehydrating auxiliary agent into the sludge injected with the dehydrating improver; Sludge thickening step; A sludge dewatering method comprising the steps of dewatering concentrated sludge,

The sludge dewatering method comprises the steps of pre-treating the sludge by heat and alkali combination for 2 to 3 hours at a temperature of 75 to 85 ° C by introducing 0.05 mg NaOH / mg SS into the sludge,
With respect to 100 parts by weight of the pretreated sludge,
The naturally dried oyster shells were placed in an electric furnace at 850 to 950 ° C and subjected to a sintering reaction for 1.5 to 2.5 hours. The calcined oyster shells (CWOS) were allowed to cool, followed by ball milling and screening with a 200 mesh sieve , The calcined oyster shell powder and distilled water are mixed at a weight ratio of 1: 4 and then heated for 5 to 8 hours to convert into a form of Ca (OH) ₂ , followed by a hydration reaction of the oyster shell, 1 to 3 parts by weight of a dewatering improver prepared by mixing an oyster shell powder and a loess powder in a ratio of 6: 4 to 9: 1;
With respect to 100 parts by weight of the sludge into which the dehydrating and improving agent is injected,
After removing the impurities and drying naturally for 24 hours, the naturally dried waste activated carbon was first pulverized with a ball mill. The pulverized activated carbon was passed through a 200 mesh sieve (75 μm)
Injecting 1 to 1.5 parts by weight of dehydrating assistant, which is waste activated carbon which is evaporated and dried for 24 hours while maintaining 105 ° C in a dry oven;
A sludge concentration step of removing a part of the liquid contained in the sludge injected with the dehydrating auxiliary agent through the concentrator and increasing the solid matter content,
And a dehydrator is installed at a downstream end of the concentrator to finally dehydrate the concentrated sludge, thereby improving the dewatering function of the sludge.

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