KR100969208B1 - Method of sewage treatment system for reducing sludge by soil-covering type contact oxidation - Google Patents

Abstract

PURPOSE: A method of sewage treatment system for reducing sludge by a soil-covering type contact oxidation is provided to chemically decompose mucous-substances of the sludge for using a cytoplasm of an organism as a material when processing microorganisms. CONSTITUTION: A method of sewage treatment system for reducing sludge by a soil-covering type contact oxidation comprises the following steps: sediment-separating sewage at a sedimentation separator(11); firstly aerating the sewage using a first contact aeration tank; precipitating the sludge inside a settling tank; secondly aerating the sewage using a second contact aeration tank; filtering the sewage at a contact filtration tank; discharging the sewage at a discharging tank; forming alkalization sludge by heat-alkalizing the sludge discharged from the contact aeration tank(12a), the settling tank(13), the contact filtration tank(14), and the discharging tank(15); neutralizing the alkalization sludge by adding acid, and separating into neutral sludge and neutral processing liquid; and reusing the neutral processing liquid.

Description

Sludge Reduction Soil-covered Contact Oxidation Sewage Treatment Method {METHOD OF SEWAGE TREATMENT SYSTEM FOR REDUCING SLUDGE BY SOIL-COVERING TYPE CONTACT OXIDATION}

The present invention relates to a soil-coated contact oxidation sewage treatment system and a method configured to significantly reduce the sludge itself by heating alkali treatment, and in particular, to a viscosity by heating alkali treatment of sludge collected in each treatment tank. Physically destroying the cell walls of sludge organisms while chemically decomposing the substance, greatly improving the sewage treatment efficiency by promoting the use of the protoplasm of the sludge organisms as a substrate of useful microorganisms in the soil and microorganisms in the treatment process, and sludge 1 The present invention relates to a sludge-reduced soil-coated contact oxidation sewage treatment system and method for reducing sludge treatment costs by less than / 3.

Water is the first thing a human needs to survive. As such water is polluted by industrialization and urbanization, modern people are threatening health and survival, and interest in water quality is increasing. Accordingly, various efforts are being made to meet the demands of modern people, such as strengthening water quality standards and preventing pollution of raw water, and management of industrial wastewater discharged to rivers is also an important issue. Since wastewater discharged from industrial activities contains organic substances and heavy metals that are extremely dangerous to the human body, if they are discharged into rivers, they can seriously threaten the health of the people as well as serious environmental problems. Plants emitting pollutants are now mandatory to have a wastewater purification facility, and have facilities to purify domestic wastewater before it is discharged to the stream. However, these purification facilities discharge sludge in the process of purifying water quality, and the discharged sludge causes other environmental problems.

As living standards raise interest in environmental issues, there is an increasing demand for environmental improvement, and large-scale sewage treatment plants are installed in large cities except for some mountainous and urban areas. As of 2000, the sewerage penetration rate was 70%, an increase of 2.1% compared to 1999 and 4.6% compared to 1997. The amount of sewage sludge is expected to increase with the increase of population and the establishment and spread of sewage treatment plants every year. At the end of 2003, the amount of sewage sludge generated at 236 sewage treatment plants was 6,199 tons, and 0.29 ㎏ of sludge dewatered cake was discharged per ㎥ of sewage. In addition, sludge production per unit sewage treatment will increase not only with the increase of sewage spread and the introduction of classification pipes, but also the total amount of sewage sludge generated.

Sewage treatment sludge treatment in Korea has been dealt with two environmental problems along with food waste in recent 4 years. Landfilling has been banned since July 2003 as landfilling trends have declined and leachate problems have increased, while residual aluminum causes environmental problems such as Alzheimer's disease. As the prohibition of direct landfilling of sewage sludge has been triggered, many local governments have sought ways to treat sewage sludge.However, due to the difficulty in preparing appropriate measures, the water content was kept below 75% by June 2003, so It has been temporarily reserved as possible.

By year, the sewage sludge treatment rate increased significantly from 22% in 1997 to 71% in 2002, while landfilling was rapidly reduced from 73% in 1997 to 12% in 2002. As of 2001, sewage sludge treatment costs for each treatment method were 22,811 won / ton for ocean dumping, 20,321 won / ton for landfill, 35/213 won / ton for incineration, 20,615 won / ton for recycling, and 18,025 won / ton for recycling. On average, it costs KRW 46,791 million to process a total of 1,895.9 thousand tons. The annual treatment cost per ton tended to decrease slightly due to the development of treatment technology and the improvement of operation, but the total cost of sludge treatment increased with the increase of sludge production.

However, the sludge treatment has become a serious problem since the London dumping treaty is expected to prohibit sludge offshore dumping from 2010, and new sludge reduction and recycling methods are required. In addition, sewage sludge has a high water content and contains a large amount of organic materials, and if it is improperly treated, there is a risk of environmental damage due to secondary pollution, and there is an urgent need for efficient use of organic materials and reduction of sludge to reduce landfill consumption. do.

Until now, studies on sludge treatment have been conducted to improve the biodegradability of sludge to increase volume reduction and anaerobic digestion efficiency. Treatment methods include ultrasonic application, physical crushing, and heat treatment, which are physical treatment methods, and general oxidation treatment, ozone treatment, and lytic oxidizer treatment, which are chemical treatment methods, and high temperature aerobic bacterial treatment, which is a biological treatment method. Combination of sludge reduction technologies has been actively developed, but these methods are techniques for treating or using sludge already generated, and there is a limit to reducing the amount of excess sludge itself.

Therefore, there is an urgent need for a technology that reduces sludge generation amount by combining physicochemical treatment with biological treatment.

In addition, in most cases, water pollution occurs in domestic sewage, and considering the cost of conduits, more efficient sewage treatment facilities of small and medium scale are required, rather than large-scale sewage treatment methods requiring large spaces and large budgets. In addition, under the conventional treatment technology, the treatment efficiency is low, but the maintenance cost is high, and there is a limit that the small and medium-sized sewage treatment facilities cannot be installed due to the aversion facility such as generation of a bad smell.

Therefore, developing a sewage treatment system that has a high treatment efficiency at a low maintenance cost and significantly reduces sludge generation, rather than a large-scale sewage treatment plant without side effects, can be greatly reduced by the sewage treatment industry. It becomes a subject and one of the objectives of this invention mentioned later.

As part of the research and development aimed at achieving the above-mentioned problems, the present applicant has disclosed Korean Laid-Open Patent Publication No. 2001-303 (name of the invention: a soil-coated internal circulation catalytic oxidation device and a catalytic oxidation method using the same), and Korean Laid-Open Patent Publication. 2001-103060 (Name of the invention: Soil-covered sewage and wastewater purification apparatus with parallel treatment of sewage and food waste), Korean Patent Publication No. 10-0631373 (contact oxidation apparatus with maximized nitrogen and phosphorus removal efficiency And contact oxidation method using the same) has been filed and registered.

Referring to Figure 1, the conventional soil-coated contact oxidation sewage treatment system sedimentation separation tank (11), primary contact aeration tank (12a), sedimentation tank (13), secondary contact aeration tank (12b), contact filtration tank (14) , The discharge tank 15 is included and the soil is coated on the upper portion of each treatment tank to form a soil layer 16, water such as grass is planted in the soil layer 16, a plurality of vents in the lower portion of the soil The formed capillary network and the filter medium, such as crushed stone in which the microorganism of the soil can be filled is made, the primary contact aeration tank (12a), sedimentation tank (13), secondary contact aeration tank (12b), contact filtration tank (14) , Each sludge discharged from the discharge tank 15 is returned to the sedimentation separation tank 11 to be reprocessed.

In the conventional soil-coated contact oxidation sewage treatment method using the same, sedimentation of sewage in the sedimentation separation tank (11), the sewage sedimentation sedimentation in the sedimentation separation tank (11) in the first contact aeration tank (12a) Aeration step, the sedimentation of the first aeration sewage in the first contact aeration tank (12a) sedimentation sludge in the sedimentation tank 13, the second contact aeration tank (12b) sewage in the state of sludge precipitated in the sedimentation tank (13) A) aeration in a second step, filtering the sewage aerated in the second contact aeration tank (12b) in a contact filtration tank (14); Discharging the sewage filtered in the contact filtration tank 14 in the discharge tank 15, the soil is coated on the upper portion of each treatment tank so that the grass is planted, a plurality of vents in the lower portion of the soil Formed capillary network (not shown), and filter media such as crushed stone, where sewage passes and can inhabit the microbes of the soil, is treated with sewage by the microorganisms in the soil and the roots of plants, and the odor is absorbed from the soil. Configured to process.

However, the above-mentioned patent application is a high quality porous breathable coated soil and sewage is contacted by the capillary infiltration, and the sewage is decomposed by soil organisms such as microorganisms and earthworms present in the soil, planted in the soil The air that is circulated to the plant roots and the soil to be promoted the decomposition treatment by the soil organisms to increase the soil microorganisms in a large amount to further improve the sewage treatment efficiency.

However, the above-described patent application of the present applicant also has a problem that it takes a long time to treat the sludge due to the low biodegradability of the sludge itself, which makes it easy for cell walls such as welfare animals, higher animals, microorganisms, etc. present in the sludge. Since it is not destroyed, the cause can be found in the fact that it is difficult for the soil organism to proliferate using the prototype in the cells of the sludge organism as a substrate.

Accordingly, an object of the present invention is to physically destroy the cell walls of sludge organisms while chemically decomposing viscous substances by heating alkali treatment of sludges collected in each treatment tank, thereby treating the protoplasm of the sludge organisms as useful microorganisms and treatment of soil. By promoting the use as a substrate of microorganisms in the process, the sewage treatment efficiency is greatly improved, and the sludge reduction, which can significantly reduce the sludge treatment cost by reducing the sludge to 1/3 or less, the soil-coated contact oxidation sewage treatment system, and the sludge reduction To provide a soil-coated contact oxidation sewage treatment method.

In order to achieve the above object, in the present invention, the sedimentation separation tank, contact aeration tank, sedimentation tank, contact filtration tank, discharge tank is included and the soil is coated on the upper portion of each treatment tank, the grass is planted, a plurality of the lower portion of the soil In the soil-coated contact oxidation sewage treatment system filled with a ventilated capillary network and a medium capable of inhabiting soil microorganisms, the sludge discharged from the contact aeration tank, the sedimentation tank, the contact filtration tank, and the discharge tank has a pH of 12. A heating alkali treatment tank for heating alkali treatment at 8 to 13.2 and 55 to 65 ° C. for 22 to 30 hours to form alkalized sludge; Neutralizing treatment by adding acid to the alkalized sludge and neutralizing the solid sludge and the neutral treatment liquid to separate solids / liquids (hereinafter referred to as 'solid / liquid'); And a sludge-reducing soil-coated contact oxidation sewage treatment system including a sedimentation separation tank which is returned to the neutral treatment liquid and reused for sewage treatment.

In the present invention, the sewage is sedimentation separation in the sedimentation tank, the sedimentation and sewage sedimentation in the sedimentation tank primary aeration in the first contact aeration tank, the first aeration sewage in the first aeration sedimentation tank Precipitating sludge in the sedimentation tank, the second aeration of the sewage in which the sludge is precipitated in the sedimentation tank in the second contact aeration tank, and filtering the sewage aerated in the second contact aeration tank in a contact filtration tank, And discharging the sewage filtered in the contact filtration tank 14 from the discharge tank, wherein the upper portion of each treatment tank is coated with soil to plant grass, and a plurality of ventilation pipes formed with a plurality of air vents at the bottom of the soil. In the soil-coated contact oxidation sewage treatment method for treating sewage by filling the media that can inhabit the soil microorganisms, the contact aeration tank, sedimentation tank, contact filtration tank Heating alkali treatment of sludge discharged from the discharge tank to pH 12.8 to 13.2 and 55 to 65 ° C. for 22 to 30 hours to form alkalized sludge; Neutralizing the acid by forming the alkaline sludge and separating solid / liquid into neutral sludge and neutral treatment liquid; And a sludge-reduced soil-coated contact oxidation sewage treatment method comprising the step of returning the neutral treatment liquid to a sedimentation separation tank and reusing it for sewage treatment.

The sludge-reducing soil-coated contact oxidation sewage treatment system according to the present invention physically destroys the cell walls of the sludge organisms while chemically decomposing viscous substances by heating alkali treatment of the sludge, thereby reducing the protoplasts of the organisms in useful soil microorganisms. By promoting the use as a substrate of water and microorganisms in the treatment process, the efficiency of sewage treatment is greatly improved, and the sludge is reduced to 1/3 or less, and the cost of sludge treatment is greatly reduced.

The present invention is an improved invention of the same Korean Patent Application Publication No. 10-0631373, the sludge collected in the soil-coated contact oxidation sewage treatment system by heating alkali treatment for a certain time, the viscous material of the sludge is chemically decomposed Alkali sludge is formed in which the cell walls of sludge organisms are physically and chemically destroyed, and the alkaline sludge is neutralized to flow out due to cell wall destruction of the liquid components and sludge organisms caused by chemical degradation of the neutralized sludge and the viscous substances deposited. By separating the solids / liquids into the neutral treatment liquid containing the protoplasts, and returning the neutral treatment liquid to the sedimentation tank of the soil-coated contact oxidation sewage treatment system for reuse in sewage treatment, the growth of the soil organisms treating the sewage Greatly improved efficiency of sewage treatment That the loss of high sludge itself is a spirit.

That is, the sedimentation separation tank 11, the primary contact aeration tank 12a, the sedimentation tank 13, the secondary contact aeration tank 12b, the contact filtration tank 14, the discharge tank 15 is included in the upper portion of each treatment tank The soil is coated to form a soil layer 16, the grass is planted in the soil layer 16, a maternity network (not shown) formed with a plurality of air vents in the lower part of the soil, and sewage passes through the soil microorganisms It is made by filling the media such as crushed stone, and the soil-coated contact oxidation sewage treatment system is constructed in which soil organisms in the soil layer play a secondary function of sewage purification and greatly improve sewage treatment efficiency. .

Soil organisms such as plants, animals, microorganisms, etc. up to about 1 m below the surface of the soil surface coexist while maintaining interdependence. When contaminants enter the soil layer, the contaminants become nutrients of the soil organisms and are decomposed and removed. It is known that the soil is inhabited by a huge variety of microorganisms, and earthworms like earthworms are very fond of sludge and have the ability to break down sludge as much as their weight every day. And since harmful bacteria living in sewage such as Escherichia coli exist in the hostile relationship with soil microorganisms, the harmful bacteria become food for soil microorganisms and can be completely removed, and the soil microorganisms become food for protozoa. The food chain relationship that is the nutrient source of the earthworm is established. In addition, the malodor generated in the soil-coated contact oxidation sewage treatment system is adsorbed while passing through the soil layer, and the adsorbed malodorous substance is gradually processed by the soil microorganisms so that the malodor is not discharged to the outside. When plants such as grass are planted on top of the soil layer, the plants grow using soil contaminants as nutrients, so that they can perform the purification function of the contaminants together with the soil, and in the case of the treatment plant, as part of the landscaping facility. Can be used.

However, the soil-coated contact oxidation sewage treatment system as described above has a problem that it takes a long time to treat the sludge due to the low biodegradability of the sludge itself, which is a welfare animal, a higher animal, a microorganism, etc. Since the cell wall is not easily destroyed, it is difficult for the soil organism to proliferate using the prototype in the cells of the sludge organism as a substrate.

Therefore, in the present invention, the primary contact aeration tank 12a, the sedimentation tank 13, the secondary contact aeration tank 12b, the contact filtration tank 14, and the discharge tank 15 in the soil-coated contact oxidation sewage treatment system are generated. Rather than returning the sludge to the sedimentation separation tank 11 as it is, a means for reducing the sludge generated by the respective treatment tanks by heating alkali treatment is provided to constitute a sludge-reduced soil-coated contact oxidation sewage treatment system.

The sludge-reduced soil-coated contact oxidation sewage treatment system of the present invention will be described in detail with reference to the drawings and examples.

Figure 2 schematically shows the structure of the soil-coated contact oxidation sewage treatment system of the present invention.

Referring to FIG. 2, first, the sludge-reducing soil-coated contact oxidation sewage treatment system of the present invention has sludge discharged from the contact aeration tank, the sedimentation tank, the contact filtration tank, and the discharge tank at pH 12.8 to 13.2 and 55 to 65 ° C. A heating alkali treatment tank for heating alkali treatment for 22 to 30 hours to form alkalizing sludge is included.

In order to chemically decompose the viscous substances contained in the sludge and to physically destroy the cell walls of the sludge organism, ozone treatment of sludge or mechanical grinding of sludge may be considered. However, the ozone treatment of the sludge is very economical because the ozone treatment apparatus is large and the ozone generation cost is high, and ozone leaked from the ozone treatment apparatus may adversely affect the environment. In addition, the mechanical crushing treatment of sludge which concentrates sludge into metal mill crusher and flows the metal mill together to force the crushing of cell wall of sludge organism by frictional force and frictional heat between the ball and the ball is insufficient. In addition, the effect of decomposing viscous substances contained in the sludge cannot be expected.

Therefore, in the present invention, the sludge is heated by alkali treatment to chemically decompose the viscous material contained in the sludge and physically destroy the cell wall of the sludge organism.

To this end, it is connected to the primary contact aeration tank 12a, the settling tank 13, the secondary contact aeration tank 12b, the contact filtration tank 14, the discharge tank 15, each of the treatment tanks 12a, 12b, 13, The heating alkali treatment tank 21 which reduces the sludge discharged | emitted by 14 and 15 by heat-alkali treatment is formed.

The heating alkali treatment tank 21 mixes an alkali agent such as sodium hydroxide to the sludge to adjust the pH to 12.8 to 13.2 to chemically decompose the viscous material contained in the sludge and physically destroy the cell wall of the sludge organism. It is configured to perform a heating alkali treatment on the sludge by maintaining the temperature of the sludge at 55-65 ° C. for 22-30 hours to promote chemical decomposition of viscous substances and cell wall destruction of sludge organisms.

If the sludge to be heated alkali treatment in the heating alkali treatment tank 21 is less than pH12.8, the phenomenon of neutralization of the sludge occurs due to the chemical reaction between the protoplasm and alkali of the sludge organisms exposed by the high temperature alkali treatment, the heating alkali treatment If the sludge exceeds pH13.2, the chemical decomposition of the viscous material in the sludge and the destruction of the cell wall of the sludge organism are no longer improved and waste of alkaline agent is generated. In addition, when the temperature of the sludge to be heated alkali treatment in the heating alkali treatment tank 21 is less than 55 ℃ does not exhibit the effect of promoting the chemical decomposition of the sludge and cell wall destruction of the sludge organism, the temperature of the sludge to be heated alkaline 65 When it exceeds C, the energy consumption used for the heating alkali treatment will be excessive. In addition, when the time for which the sludge is heated alkali treatment in the heating alkali treatment tank 21 is less than 22 hours, the chemical decomposition of the viscous material in the sludge and the cell wall destruction of the sludge organism does not proceed sufficiently, and the time for the sludge is heated alkali treatment If this time exceeds 30 hours, the chemical decomposition of the viscous material in the sludge and the cell wall destruction of the sludge organism will no longer proceed.

By heating the sludge, the viscous material of the sludge is chemically decomposed, and an alkalized sludge in which the cell wall of the sludge organism is destroyed is formed, and the alkaline sludge is neutralized and reduced.

In addition, the sludge-reducing soil-coated contact oxidation sewage treatment system of the present invention includes a neutralization tank that neutralizes the acidic sludge by adding acid and separates solid / liquid into neutral sludge and neutral treatment liquid.

Since the alkalized sludge formed by the heating alkali treatment in the heating alkali treatment tank 21 is strongly alkaline, the supernatant liquid / liquid separated from such strongly alkaline alkalinized sludge is returned to the sedimentation separation tank 11 as it is. In addition to severely adversely affecting the habitat of the soil organisms, the sewage discharged from sludge-reduced soil-coated contact oxidation sewage treatment system exhibits strong alkalinity, which impairs the environment. In addition, alkaline sludge also becomes difficult to treat with a known sludge treatment method.

Therefore, the neutralization treatment tank 22 which separates solid / liquid into a neutral sludge as a solid and a neutral treatment liquid as a supernatant by neutralizing by adding an acid, such as sulfuric acid, to the alkalized sludge conveyed by heating and heating in the alkali treatment tank 21 is heated. Is formed.

The neutral treatment liquid separated from the neutral sludge in the neutralization treatment tank 22 is returned to the sedimentation separation tank 11 to promote the growth of soil organisms inhabiting the soil layer 16.

As described above, the strongly alkaline supernatant separated from the neutral sludge and solid / liquid contains liquid components generated by chemical decomposition of viscous substances and protoplasts released by cell wall destruction of sludge organisms, and the liquid components and protoplasts are soil organisms. By greatly promoting the growth of sewage, the efficiency of sewage treatment is greatly improved and sludge reduction is supported.

In addition, the amount of final sludge deposited in the neutralization tank 22 is about one third of the initial sludge discharged and discharged from each treatment tank 12a, 12b, 13, 14, and 15, and the sludge generation itself was reduced. In addition, the reduced sludge is treated by a known sludge treatment method such as concentration, drying, fertilization and the like.

In addition, the sludge-reduced soil-coated contact oxidation sewage treatment system of the present invention includes a sedimentation separation tank which is formed so that the neutral treatment liquid is returned and reused in sewage treatment.

The sedimentation separation tank 11 of the sludge-reducing soil-coated contact oxidation sewage treatment system is configured to continue to use the neutral treatment liquid returned from the neutralization treatment tank 22 for the soil-coated contact oxidation sewage treatment.

The neutral treatment liquid returned from the neutralization treatment tank 22 to the sedimentation separation tank 11 contains the liquid component generated by chemical decomposition of the viscous material and the plasma flowing out by the cell wall destruction of the sludge organism, and the liquid component and Protoplasm greatly promotes the growth of soil organisms in the soil layer 16, greatly improving the efficiency of sewage treatment, and supporting sludge reduction.

The sludge-reducing soil-coated contact oxidation sewage treatment method of the present invention will be described in detail with reference to Examples.

Precipitating and separating sewage in a sedimentation tank; pre-aeration of sewage sediment separated in the sedimentation tank in a first contact aeration tank; and precipitating sludge in the sedimentation tank of the first aeration sewage in the first contact aeration tank. Step, the second aeration of the sewage in the sludge precipitated in the sedimentation tank in the second contact aeration tank, filtering the sewage secondary aerated in the second contact aeration tank in the contact filtration tank, filtration treatment in the contact filtration tank And discharging the sewage from the discharge tank, wherein the soil is coated on the upper portion of each treatment tank, and the grass is planted. In the soil-coated contact oxidation sewage treatment method in which the filter medium is filled to treat sewage, the primary contact aeration tank, the sedimentation tank, the secondary contact aeration tank, the contact filtration tank, and the discharge Am ah as to transport the precipitate separation tank the sludge generated in, a method for reduction of sludge generation itself in the above-mentioned treatment tank is provided The method of sludge reduction soil coated type contact sewerage oxide is formed.

First, the sludge-reducing soil-coated contact oxidation sewage treatment method of the present invention is heated alkali for 22 to 30 hours at pH 12.8 to 13.2 and 55 to 65 ° C for sludge discharged from the contact aeration tank, sedimentation tank, contact filtration tank, and discharge tank. Treating to form alkalized sludge.

The first sludge discharged from the primary contact aeration tank, the settling tank, the secondary contact aeration tank, the contact filtration tank, and the discharge tank to the heating alkali treatment tank is subjected to heat alkali treatment to form a reduced alkalized sludge compared to the sludge.

Specifically, in the heating alkali treatment tank, an alkaline agent such as sodium hydroxide is mixed with the sludge to adjust the pH to 12.8 to 13.2 to chemically decompose the viscous material contained in the sludge and physically destroy the cell wall of the sludge organism, In order to promote chemical decomposition of the substance and destruction of the cell walls of the sludge organisms, the heating alkali treatment is performed on the sludge by maintaining the temperature of the sludge at 55 to 65 ° C. for 22 to 30 hours.

If the sludge is heated to alkaline, the viscous material of the sludge is chemically decomposed, and the alkalinized sludge is formed while the cell wall of the sludge organism is destroyed, and the alkalinized sludge is neutralized and reduced.

In addition, the sludge-reducing soil-coated contact oxidation sewage treatment method of the present invention includes the step of neutralizing the acid-forming sludge by adding an acid forming the alkaline sludge and dividing the solid / liquid into a neutral sludge and a neutral treatment liquid.

Since the alkalinity sludge formed by the heating alkali treatment in the heating alkali treatment tank is acidic strongly alkaline, when the supernatant liquid / liquid separated from the strongly alkaline alkalinization sludge is returned to the sedimentation tank as it is, the soil organisms inhabit the soil layer. Seriously adverse effects, and because the sewage discharged from the sludge-reduced soil-coated contact oxidation sewage treatment system is strongly alkaline, it is not only harmful to the environment, it is also difficult to treat the sludge that is alkaline also known sludge treatment method.

Therefore, by neutralizing by adding acid, such as sulfuric acid, to the alkalized sludge transferred by heating alkali treatment in the heating alkali treatment tank, the solid / liquid is divided into neutral sludge as a solid and neutral treatment liquid as a supernatant.

That is, acid is added to the alkaline sludge to convert the neutral sludge and the neutral treatment liquid to a pH close to neutral, and the neutral treatment liquid is returned to the sedimentation separation tank to promote the growth of soil organisms inhabiting the soil layer.

The neutral treatment liquid separated from the neutral sludge and solid / liquid contains a liquid component generated by chemical decomposition of the viscous material of the sludge and a plasma discharged by the destruction of the cell wall of the sludge organism, and the liquid component and the plasma are soil layers. By greatly promoting the growth of the soil organisms contained in the sewage treatment, the efficiency of sewage treatment is greatly improved and sludge reduction is supported.

The amount of final sludge deposited in the heating alkali treatment tank is about one third of the initial sludge discharged from each treatment tank, and the sludge generation itself is reduced, and the sludge is concentrated, dried, and fertilized. Treated by sludge treatment method.

In addition, the sludge-reduced soil-coated contact oxidation sewage treatment method of the present invention includes the step of returning the neutral treatment liquid to the sedimentation tank for reuse in sewage treatment.

The neutral treatment liquid returned from the neutralization tank to the sedimentation separation tank contains the liquid component generated by chemical decomposition of the viscous material and the protoplasts released by the destruction of the cell wall of the sludge organism, and the liquid component and the protoplasts proliferate the soil organisms. This greatly promotes the efficiency of sewage treatment, while supporting sludge reduction.

The sludge-reduced soil-coated contact oxidation sewage treatment system and method of the present invention will be described in detail with reference to specific examples. However, the following examples are only for illustrating the present invention in detail, and do not limit the present invention.

<Examples>

1. Experiment apparatus and operation method

Based on the design specifications of the conventional soil-coated contact oxidation sewage treatment system, sludge-reduced soil-coated soil which is a laboratory scale of 40 L / day of sewage treatment capacity provided with means for reducing the sludge itself generated in each treatment tank. Three sets of catalytic oxidation sewage treatment reactors were constructed.

3 is a photograph of a soil-coated catalytic oxidation sewage treatment reactor according to one embodiment of the present invention.

As described above, the present invention uses a soil-coated contact oxidation method. Referring to FIG. 3, a sedimentation tank, a primary contact aeration tank, a precipitation tank, a secondary contact aeration tank, and a sludge-reduced soil-coated contact oxidation sewage treatment reactor, The upper part of each treatment tank, which was a contact filtration tank and a discharge tank, was covered with porous soil in which grass was planted. This reactor was installed inside the laboratory to minimize the external artificial factors, and sludge reduction experiments were carried out. To prevent the occurrence of green algae in the reactor, the surface of the reactor was surrounded by expanded polystyrene (EPS). Encased.

2. Artificial preparation and operation of sewage water

Generally, the sewage water characteristics of single-family homes or farming and fishing villages are very high because of the inflow of livestock waste water. Therefore, the concentration range during influent wastewater operation is based on the main water quality characteristics of the wastewater from rural areas. Artificial synthetic wastewater of similar composition was prepared. Artificial synthetic wastewater was prepared using glucose, calcium phosphate (KH ₂ PO ₄ ), and the like. In Table 1 below, the concentrations of the major water quality items of the synthetic wastewater are shown in comparison with the sewage water quality of rural areas.

<Table 1> Comparison of Sewage Water Quality and Major Synthetic Wastewater Concentrations in Agricultural and Fishing Villages

Item division CODcr (mg / L) T-N (mg / L) T-P (mg / L) pH Rural Sewage Water Quality Characteristics 300 100 15 - Artificial synthetic wastewater 375 45 7.5 7.0

In this experiment, the amount of artificial wastewater flowing into the sludge-reduced soil-coated contact oxidation sewage treatment reactor was 10 L per day, and the inflow amount was 7 ml / min, and the wastewater and soil layers in each treatment tank were maintained at 4 to 30 ° C. The dissolved oxygen amount (DO) of the primary contact aeration tank and the secondary contact aeration tank was maintained at 2 to 8 mg / L. Table 2 shows the trace element composition of the artificial synthetic wastewater.

<Table 2> Trace Elements Composition of Synthetic Wastewater

division Content (g / L) KH ₂ PO ₄ 0.200 K ₂ HPO ₄ 0.350 MgSO ₄ 7H ₂ O 0.295 CaCl ₂ 2H ₂ O 0.180 FeSO ₄ 7H ₂ O 0.010 NaCl 2.000 MoO ₃ 0.001

3. Review the results

Sludge Reduction The sludge discharged from the primary contact aeration tank, the sedimentation tank, the secondary contact aeration tank, the contact filtration tank, and the discharge tank of the soil-coated contact oxidation sewage treatment reactor was reduced by heat alkali treatment or heat treatment in the heat treatment tank.

1) pH change by sludge solubilization

Specifically, the sludge-reduced soil-coated contact oxidation sewage treatment reactor 1 was treated with sodium hydroxide mixed with sodium hydroxide for 24 hours by heating the sludge discharged from each treatment tank for 24 hours, and sludge-reduced soil-coated contact oxidation. In the constant temperature tank of sewage treatment reactor 2, the sludge discharged from each treatment tank was mixed with sodium hydroxide and heated to alkaline at pH 10 and 60 ° C. for 24 hours, and the sludge reduction soil-coated contact oxidation sewage treatment reactor 3 was treated in each treatment tank. The sludge discharged from was heated at 60 ° C. for 24 hours without mixing sodium hydroxide, and samples were taken every 0, 1, 3, 5, 8, 12, and 24 hours in a thermostatic chamber of each reactor. Measured.

Figure 4 is a chart showing the pH change according to the heating alkali treatment time of the sludge in one embodiment of the present invention.

Referring to FIG. 4, in the samples in which the sludge was heated to 60 ° C. and the samples heated to 60 ° C. without adjusting the pH, the sludge was little changed in pH according to the heating time. It was confirmed that the sample heat-treated at 60 ° C. changed to a neutralized state for the first 1 hour. The rapid neutralization of the sample subjected to the alkaline treatment of the sludge at pH 10 and 60 ° C. in a short time is a phenomenon in which the sludge is neutralized due to the chemical reaction between the protoplasm and the alkali of the sludge being exposed by the heating alkali treatment at pH 10. It seems to be caused.

2) sludge reduction effect

Samples taken every 0, 1, 3, 5, 8, 12 and 24 hours in each reactor's thermostat were neutralized with sulfuric acid and then centrifuged at 3,000 rpm for 5 minutes to give solid sludge and liquid neutral treatment solution. And neutral neutral sludge was obtained. The organic matter load (MLSS) of each obtained neutral sludge was measured, and the sludge reduction rate was computed from the organic matter load (MLSS) of each said neutral sludge.

5 is a chart showing the change of the organic load of the sludge according to the heating alkali treatment time in the embodiment of the present invention, Figure 6 is a chart showing the sludge reduction rate according to the heating alkali treatment time of the sludge in one embodiment of the present invention to be.

5 and 6, when the sludge is heated at 60 ° C. without adjusting the pH, the sludge has an organic load of 7,000 mg / L for the first sludge and an organic load of 5,000 mg / L for the sludge heated for 24 hours. 28.5% was found to be reduced.

On the other hand, when the sludge was heated to pH 10 and 60 ° C, the organic sludge of the first sludge was 7,000 mg / L, and the sludge of the sludge treated with the heating alkali for 24 hours was 3980 mg / L, resulting in a 43% reduction in sludge. When the sludge was heated to pH 13 and 60 ° C, the sludge was reduced by 72% with an organic load of 7,000 mg / L for the first sludge and 1,940 mg / L for the sludge heated for 24 hours.

Accordingly, it can be seen that the sludge reduction effect has a greater effect on sludge alkali treatment and heat treatment at the same time than the sludge heat treatment alone, and the sludge reduction effect when the heat treatment is performed at pH 13 which is strongly alkaline than pH 10 is performed. Appeared to be more excellent. This may be due to the greater function of destroying the cell wall of the sludge in the strong alkaline atmosphere than in the weak alkaline atmosphere.

3) Carbon concentration according to sludge treatment

The neutralized liquid formed by heating and neutralizing the organic material is returned to the sludge-reduced soil-coated contact oxidation sewage treatment process, whereby the microorganism of the sludge organism contained in the neutral treatment liquid is ingested as a substrate. The control of the sludge generation amount can be completed. Therefore, the carbon concentration after artificially destroying the cell wall of the sludge life can be said to be a very important factor in controlling the amount of sludge generation.

Neutralization treatment of the first (0 hour) sludge sample and the sample of alkaline sludge collected after 24 hours in each of the reactor's thermostats yielded a neutral treatment liquid that is solid / liquid separated from the neutral sludge. Carbon concentration (TOC) was measured by a TOC analyzer (product name TOC-V _CPH ; Shimadze, Kyoto, Japan).

7 is a graph showing the carbon content of the neutral treatment liquid according to the treatment time of the sludge in one embodiment of the present invention.

Referring to FIG. 7, the carbon concentration of the first sludge was measured at 40 ppm, but when the sludge was heated to 60 ° C. without adjusting the pH, the carbon concentration of the supernatant was increased to 435 ppm, and the sludge to pH 10 and 60 ° C. The carbon concentration of the supernatant was increased to 513 ppm in the heating alkaline treatment, and the carbon concentration of the supernatant was increased to 603 ppm in the heating alkali treatment at pH 13 and 60 ° C. This means that the heating alkali treatment of the sludge is sufficient to physically destroy the cell walls of the sludge organisms and to promote the use of the protoplasts of the organism as substrates of useful microorganisms in the soil and microorganisms in the treatment process.

4) Experimental observation of live cell density according to sludge treatment time

Neutralizing the samples taken every 0, 1, 3, 5, 8, 12, 24 hours in each reactor thermostat with sulfuric acid, and then diluted with 100-fold physiological saline to form a medium, and administered the R2A reagent Live cell density was observed.

8 is a photograph showing the results of cultivation observation experiment according to the treatment time of the sludge in one embodiment of the present invention.

Referring to FIG. 8, it was confirmed visually that a large number of living cells survived in the sample heated to 60 ° C. without sludge and the alkali treated sludge at pH 10 and 60 ° C. On the other hand, in the samples treated with sludge heated to pH13 and 60 ° C, the viable cells gradually decreased as the heating alkali treatment time increased. After 24 hours, the sludge decreased to 2.1 × 10 ^-3 cells / ml. Appeared.

5) Optical observation experiment of alkalized sludge

The original sludge contains a flock consisting of cell masses, protozoa, filamentous bacteria and the like, which tends to decrease with the heat alkali treatment or heat treatment of the sludge.

Samples collected after 24 hours in the thermostat of each reactor were observed by light microscopy.

9 is an optical micrograph of the alkalized sludge obtained in one embodiment of the present invention.

Referring to FIG. 9, the flocs were almost destroyed in the samples in which the sludge was heated to pH 10 at 60 ° C., but the bodies of living cells and higher organisms were still present. On the other hand, the sludge was heated to pH 13 and 60 ° C., and the samples were completely decomposed as well as live cells and higher organisms.

These results show that the structure of the cell wall of the sludge organism is important for solubilizing the sludge using cell wall destruction. Eukaryotes such as protozoa are easy to destroy because they have only a single cell wall. On the other hand, the prokaryotic cell wall is formed in a multi-layered structure with a peptidoglycan layer, which is very difficult to destroy. It can be seen that all prokaryotic cells exist without being destroyed. In contrast, optical micrographs of samples heat-treated at pH 13 and 60 ° C. showed that the eukaryotic and prokaryotic cells were almost completely destroyed. It must be done.

6) Elemental Analysis of Alkalized Sludge

Sludge form and elemental analysis were carried out by SEM / EDX (S4700, HITACHI Japan) by firing and grinding the first (0 hour) sludge sample and the sample of alkaline sludge collected after 24 hours in each reactor in each reactor. The results are shown in Table 3 below.

<Table 3>

division First sludge Heat treatment pH10 heat treatment pH13 heat treatment C 0.19 16.93 4.99 0 O 69.01 58.31 63.71 65.60 Na 0.67 0.31 2.38 9.08 Mg 2.41 2.40 1.92 3.40 Al 5.42 4.60 5.74 5.31 Si 7.69 5.90 8.39 7.23 P 8.16 6.43 6.38 3.78 K 2.14 1.24 1.27 0.88 Ca 1.65 1.82 2.64 0.35 Fe 2.65 2.60 2.59 2.09 Sum 100

In Table 3, the carbon content of the pH 13 heated alkali treated sample was found to be 0, which means that the cell wall destruction was completely progressed and the substrate in the cell was released to the outside, so that only inorganic matter remained in the sludge. It can be estimated that the organic load is reduced to about 72% in the organic load measurement experiment, and the remaining 28% is inorganic. In addition, the carbon concentrations of the heat-treated samples and the pH 10 heat-alkali-treated samples were 16.93% and 4.99%, respectively, which caused slight cell wall destruction by heat or pH 10 heat-alkali treatment in the two samples. This was not completely destroyed, meaning that the substrate in the cell was not completely released to the outside.

As described above, when the sludge is heated to a pH of 13, the viscous material is chemically decomposed, and the cell walls of the sludge organism are physically destroyed, and the liquid component and the sludge organism generated by the chemical decomposition of the viscous material of the sludge. Neutral treatment solution containing protoplasts, which are discharged by cell wall destruction, is returned to the sedimentation tank and promoted to be used as a substrate of useful microorganisms in the soil layer and microorganisms in the treatment process, and the sludge is greatly improved. Reduced to 3 or less.

1 is a structural diagram of a conventional soil-coated contact oxidation sewage treatment system

2 is a structural diagram of a soil-coated contact oxidation sewage treatment system of the present invention

3 is a photograph of a soil-coated catalytic oxidation sewage treatment reactor according to an embodiment of the present invention.

Figure 4 is a chart showing the pH change according to the heating alkali treatment time of the sludge in one embodiment of the present invention

5 is a chart showing the change in organic matter load according to the treatment time of the sludge in one embodiment of the present invention

Figure 6 is a chart showing the sludge reduction rate according to the treatment time of the sludge in one embodiment of the present invention

7 is a graph showing the carbon content of the neutral treatment liquid according to the treatment time of the sludge in one embodiment of the present invention

Figure 8 is a photograph showing the results of the observation of living cell density according to the treatment time of the precipitate in one embodiment of the present invention

9 is an optical micrograph of the alkalized sludge obtained in one embodiment of the present invention

* Explanation of symbols for the main parts of the drawings

11 sedimentation tank 12 contact aeration tank (a, b)

13: settling tank 14: contact filtration tank

15: discharge tank 16: soil layer

21: heating alkaline treatment tank 22: neutralization treatment tank

Claims (2)

delete Precipitating and separating sewage in a sedimentation tank; pre-aeration of sewage sediment separated in the sedimentation tank in a first contact aeration tank; and precipitating sludge in the sedimentation tank with primary aeration in the first contact aeration tank. Step, the second aeration of the sewage in the sludge precipitated in the sedimentation tank in the second contact aeration tank, filtering the sewage secondary aerated in the second contact aeration tank in the contact filtration tank, filtration treatment in the contact filtration tank And discharging the sewage from the discharge tank, wherein the soil is coated on the upper portion of each treatment tank, and the grass is planted. In the soil-coated contact oxidation sewage treatment method that is filled with a filter medium to treat the sewage, Forming alkalized sludge by heating and treating the sludge discharged from the contact aeration tank, the settling tank, the contact filtration tank, and the discharge tank at pH 12.8 to 13.2 and 55 to 65 ° C. for 22 to 30 hours; Neutralizing the acid by forming the alkaline sludge and separating solid / liquid into neutral sludge and neutral treatment liquid; And Sludge-reduced soil-coated contact oxidation sewage treatment method comprising the step of returning the neutral treatment liquid to the sedimentation tank and reused for sewage treatment.

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