KR101827525B1 - Method for small medium size sewage advanced treatment using float media filtering - Google Patents

Abstract

The present invention relates to an anaerobic treatment step of introducing sewage into an oxygen-free anaerobic tank; An aeration or anaerobic treatment step of introducing the anaerobically treated sewage into an aeration tank having a dissolved oxygen concentration of 1.0-2.0 mg / L or an oxygen-free anoxic tank having an oxygen concentration of 0.1 mg / L or less; And introducing the aerated or anaerobic treated sewage into an aeration tank containing a flotation-packed treatment water tank, wherein the aeration tank has an aerated treatment concentration of 1.0-2.0 mg / L, and the flotation media And then backwashed through an operation of taking out the floated treatment water filled in the floating filter medium from the aeration tank.
According to the present invention, nitrogen and phosphorus can be removed at a shorter hydraulic retention time than conventional sewage treatment methods, an aeration treatment or anaerobic treatment is performed according to the state of the inflowed sewage, a specific treatment flow rate is set, The floating filter media can be backwashed and the removal efficiency of nitrogen and phosphorus can be improved.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for treating sewage sludge,

The present invention relates to a small and medium sized sewage treatment method using floating filter media. More specifically, the present invention relates to an invention in which treatment efficiency of nitrogen and phosphorus is increased by aerating or anaerobic treatment depending on the state of sewage used in sewage treatment and controlling the treatment flow rate.

As the food industry has become more sophisticated and the living standard has improved, the living environment has changed in the direction of personal hygiene and cleanliness. Organic and other pollutants contained in synthetic detergent, shampoo, soap, And the water quality of the rivers and lakes was greatly deteriorated. The disruption of water supply due to the loss of value of domestic water resources is not limited to urban areas, but spreads to rural areas. Most rural areas are located in the water supply districts of water supply in urban areas. Supply of sewage treatment facilities is urgent. Especially, in rural areas of Korea, pollution factors continue to increase due to population density, increase of livestock facilities, various amusement facilities and development of agriculture and development districts, while investments in environmental infrastructure such as sewage pipes and treatment plants are absolutely insufficient.

Therefore, it is necessary to develop an optimal water treatment system to mitigate the technical difficulties of wastewater treatment in farming and fishing villages, taking into consideration the characteristics of the water environment in rural areas.

The sewage treatment method is divided into biological treatment which removes organic matter by microorganisms according to the treatment principle, chemical treatment which removes heavy metals by using chemicals, and physical treatment which removes impurities and solid substances by a machine such as a screen. Most commonly, biological treatment is used, which is divided into two groups according to microbial growth methods, suspended microorganism method and adherent microorganism method. It is divided into aerobic and anaerobic treatment methods in relation to oxygen. It is divided into car treatment and advanced treatment.

The sewage treatment method can be classified according to the growth of microorganisms such as suspended growth method and adhesion growth method, or anaerobic treatment method and anaerobic / aerobic method according to anaerobic and aerobic methods. Among the various sewage treatment methods, there are 26 methods such as standard activated sludge method, contact oxidation method, and live-in method, which are developed by the treatment methods developed for the domestic sewage treatment in rural areas of Korea. Efficient and excellent sewage treatment technology.

In the present invention, the conventional treatment technology, which only focuses on the removal of organic substances (BOD) and suspended solids (SS), is one step further, and the technology capable of simultaneously removing nitrogen and phosphorus, which are substances of eutrophication and red tide, Experiments were conducted to meet the criteria of ease of maintenance, simplicity of disposal of sludge, water quality satisfaction of planned effluent, reactivity to inflow sewage and water quality change, possibility of advanced treatment and ease of enlargement, Finally, the present invention has been completed.

Accordingly, it is an object of the present invention to provide a small-scale high-grade sewage treatment technology capable of removing nitrogen and phosphorus efficiently by controlling the treatment flow rate, aeration treatment and the like with a shorter hydraulic retention time than existing sewage treatment methods.

It is another object of the present invention to provide a small and medium-sized sewage treatment technology capable of effectively performing backwashing without requiring additional backwash water for backwashing floating filter media and also maintaining the quality of treated water.

According to one aspect of the present invention, there is provided a sewage treatment method comprising the steps of: a) anaerobic treatment step of introducing sewage into an anaerobic tank without oxygen; b) an aerobic or anaerobic treatment step of introducing the anaerobically treated sewage into an aeration tank having a dissolved oxygen concentration of 1.0-2.0 mg / L or an oxygen-free anoxic tank having an oxygen concentration of 0.1 mg / L or less; And c) introducing the aerated or anaerobically treated sewage into an aeration tank containing a flotation-packed treatment water tank, wherein the aeration tank has an aerated treatment concentration of 1.0-2.0 mg / L, The filter material can be backwashed through an operation of taking out the treated water tank filled with the floating filter medium outside the aeration tank.

In one embodiment of the present invention, the steps a) to c) may be operated at a hydraulic retention time of 2-6 hr.

In one embodiment of the present invention, the hydraulic retention time may be 5-6 hrs, 1- 3-30 hrs, .

In one embodiment of the present invention, the sewage treatment can be carried out with a treatment capacity of 25-125 m ³ / day.

In one embodiment of the present invention, the sewage can be maintained at a mixed liquer suspended solids concentration in the range of 2500-3500 mg / L.

In one embodiment of the present invention, the floating filter medium may be formed of a material selected from the group consisting of expanded polypropylene, polypropylene, polyethylene, polystyrene, and ethylene vinyl acetate It can be any one selected.

In one embodiment of the present invention, the floating media may have a density of 800-900 kg / m ³ , a diameter of 3-4 mm, and a specific surface area of 1500-2000 m ² / m ³ , A density of 870 kg / m ³ , a diameter of 3.8 mm, and a specific surface area of 1750 m ² / m ³ .

In an embodiment of the present invention, the floating filter medium is filled in the treated water tank at a filling rate of 50-60%, and may be backwashed at a cycle of 12-18 h once.

The treatment water tank may have a mesh-type wire mesh at a lower portion spaced apart from the floating filter medium.

As described above, according to the present invention, nitrogen and phosphorus can be removed at a shorter hydraulic retention time than the conventional sewage treatment method.

According to the present invention, an aeration treatment or anaerobic treatment is performed according to the state of the inflowed sewage, a specific treatment flow rate is set, a recyclable floating filter material performs additional organic matter decomposition and nitrification, and the sludge produced in the sewage treatment process is returned And the removal efficiency of nitrogen and phosphorus can be improved by recycling.

In addition, according to the present invention, effective backwashing can be performed without backwash water for backwashing floating filter media, and the quality of treated water can be stably maintained.

FIG. 1 is a diagram of an apparatus capable of performing a small-scale high-level sewage treatment according to the present invention.
FIG. 2A is a perspective view of a floating filter medium treatment tank according to the present invention, and FIG. 2B is a diagram showing a backwashing process of a floating filter medium.
3 is a graph showing TBOD (total BOD) values of influent and effluent during treatment according to the sewage treatment method of the present invention.
4 is a graph showing SBOD (soluble BOD) values of influent and effluent during treatment according to the sewage treatment method of the present invention.
5 is a graph showing Suspended Solid (SS) values of influent and effluent during treatment according to the sewage treatment method of the present invention.
6 is a graph showing COD (Chemical Oxygen Demand) values of influent and effluent during processing according to the sewage treatment method of the present invention.
7 is a graph showing the number of E. coli in the influent and the effluent during the treatment according to the sewage treatment method of the present invention.
8 is a graph showing the values of NH ₄ -N values of influent and effluent during treatment according to the sewage treatment method of the present invention.
9 is a graph showing TN (total nitrogen) values of influent and effluent during treatment according to the sewage treatment method of the present invention.
10 is a graph showing TP (total phosphorus) values of influent and effluent during treatment according to the sewage treatment method of the present invention.

The present invention relates to a small and medium sized sewage treatment method using floating filter media. More specifically, the present invention relates to an invention in which treatment efficiency of nitrogen and phosphorus is increased by aerating or anaerobic treatment depending on the state of sewage used in sewage treatment and controlling the treatment flow rate.

In the present invention, sewage is a collective term such as sewage, rainwater and wastewater of a factory. In a typical municipal wastewater, an oxygen-requiring substance, sediment, grease, oil, scum, pathogenic bacteria, Substances, pesticides, refractory organic compounds, heavy metals and so on. The characteristics of sewage can be represented by turbidity (international turbidity unit), suspended solids (ppm), total dissolved solids (ppm), pH (pH), dissolved oxygen (ppm, mg / L) and biochemical oxygen demand biochemical oxygen demand (BOD) is used as a measure of oxygen demand. The sewage treatment process is classified into three types: primary treatment in which impurities such as rocks, grease, and scum are removed, secondary treatment in which treated water is obtained through biological treatment, and tertiary treatment or advanced treatment in which the quality of treated water is improved.

Specifically, the primary treatment is a physical treatment step, which removes impurities and contaminants in the sewage introduced by screen, sedimentation, flow adjustment, etc., stabilizes the fluctuation of the influent water as much as possible, . Usually, the treatment includes the screen, the needle set, the crusher, the flow rate adjusting tank, and the settling tank.

Secondary treatment is a process based on a biological process in which microorganisms consume oxygen and is a step of removing contaminants that have not been removed in the primary treatment, mainly solubility materials and some of the suspended materials.

The tertiary treatmnt or advanced treatment is a step for the removal of nitrogen and phosphorus as a term for various treatment processes performed on the effluent from the secondary treatment. In closed water bodies such as lakes and reservoir basins, the emission standards are set for nitrogen, phosphorus, etc. as well as BOD for the prevention of eutrophication.

Nitrogen is one of the substances to be subjected to advanced treatment, and chemical methods, biological methods, ion exchange methods and membrane techniques can be used. When the nitrogen is removed through the biological treatment process, nitrification, in which ammonia nitrogen is converted into nitrate through microbial mediated reaction in an aerobic environment, and denitrification in which nitrate is removed into nitrogen gas in an oxygen-deficient environment such as an anaerobic or anaerobic environment .

First, ammonium ions (NH ₄ ⁺ ) are the first inorganic minerals that occur during the biodegradation of organic nitrogen compounds. They are oxidized to nitrite (NO ₂ ^- ) by Nitrosomonas bacteria in the aerobic environment, followed by nitrite It is oxidized to nitrate (NO ₃ ^- ) by Nitrobacter bacteria. The reaction formula for this process is as follows.

2NH ₄ ⁺ + 3O ₂ ? 4H ⁺ + 2NO ₂ ^- + 2H ₂ O

^{_{2NO 2 - + O 2 → 2NO}} 3 -

Nitrate can then be removed by denitrification in an oxygen deficient environment as follows.

4NO ₃ ^- + 5 (CH ₂ O) + 4H ^{+ -} > 2N ₂ (g) + 5CO ₂ (g) + 7H ₂ O

The nitrogen gas produced in the reaction forms bubbles in the sludge flocs to float the sludge. This phenomenon is disadvantageous in that the sedimentation of the sludge is hindered and the load of organic matter is increased. However, when this phenomenon is used under the proper conditions, nitrogen can be removed.

In advanced treatment, removal of phosphorus is essential to reduce algal growth. Algae grow even in the presence of 0.05 mg / L of phosphoric acid (PO ₄ ^{3 -} ), so very low concentrations of phosphoric acid (PO ₄ ^{3 -} ) must be maintained to inhibit algal growth. Since urban wastewater contains about 25 mg / L of phosphate (orthophosphate, polyphosphate, insoluble phosphate), phosphorus removal efficiency should be very high to inhibit algal growth.

Phosphorus can be removed after (1) the primary clarifier of the sewage treatment process, (2) the aeration tank of the activated sludge, or (3) the secondary wastewater treatment, which removes about 20% of the phosphorus contained in the sewage through the activated sludge process. Generally, there are almost no phosphorus dissolved in water, pH, NO _x , SRT, HRT and other substances. In a typical activated sludge plant it exhibits a low pH, where the phosphate forms H ₂ PO ₄ ^- . However, in the case of water with relatively high hardness, when the higher rate of expansion is maintained, the carbon dioxide is transferred to the atmosphere and the pH is raised, resulting in the following reaction.

5Ca ₂ + + 3HPO ₄ ^2- + H ₂ O → Ca ₅ OH (PO ₄ ) ₃ (s) + 4H ⁺

The reaction is highly dependent on the concentration of hydrogen ions, but the reaction proceeds to the left at low pH where the hydrogen ion concentration is high. Thus, under anaerobic conditions, which are more acidic, phosphate is dissolved again in solution.

Sewage treatment can be classified into floating growth method and adhesion growth method according to microorganism growth and can be classified into aerobic treatment method and anaerobic / aerobic parallel method depending on presence or absence of oxygen.

Treatment with floating microorganisms is a method of treating pollutants by using activated sludge as growth nutrients in which organic and inorganic salts in sewage are nutrient salts. The floc is formed by metabolic action such as oxidative decomposition by organisms. The mixed liquid is separated from the sedimentation tank by the supernatant and sludge, and the treated water is discharged and a part of the sludge is returned and removed as surplus sludge. The amount of sludge generated is large and a sludge conveying device is required.

Floating growth methods include standard activated sludge method, long time width method, stepwise width method, contact stabilization method, inhalation method, batch activated sludge method (SBR), advanced treatment method of high concentration organic wastewater, oxidation method, oxidation method, Bio-Reactor), Bacillus bacteria treatment (B3 system), KS BNR method, Imhoff method, anaerobic digestion method, intermittent aeration method (STAR process).

Treatment with an adherent microorganism is a method of immobilizing microorganisms in a medium in the reaction tank and oxidizing and decomposing pollutants in the sewage to convert it into gas or cell proliferation. The immobilized carrier biofilm method and the fluidized bed biofilm method Respectively. The biofilm method using the contact carrier is generally effective in reducing sludge generation and maintenance, facilitating the removal of pollutants with a low decomposition rate due to a large amount of microorganisms in the reaction tank and a variety of biological forms, and is resistant to changes in water temperature and load, Is an effective method.

 Adhesive growth methods include contact oxidation, inter-station contact oxidation, anaerobic / aerobic contact (SCS), suspended microbial contact (HBC), soil-covered contact width technique, soil trench method, rotating disk contact method (RBC) (KDHST), cyanobarbital contact method (CNR), three-step contact aeration method, membrane separation method, anaerobic contact aeration type treatment device (KSST) and waste water treatment method using waste vinyl filter media.

Anaerobic treatment is a method of treating wastewater using anaerobic microorganisms that survive in the absence of oxygen. The solids and suspended solids contained in the incoming wastewater are separated from the water and do not come into contact with oxygen in the sediment, but the anaerobic microorganisms that propagate even in the absence of oxygen gradually proliferate in the sediments and the sediments are decomposed by the microorganisms. Organic materials decomposed into anaerobic microorganisms are starch, fat, fiber and protein, which are decomposed by the action of anaerobic microorganisms and converted into methane gas or carbon dioxide gas, converting organic matter into inorganic matter.

Aerobic treatment is a method of decomposing and oxidizing organic matter in sewage by aerobic microorganisms that live on respiration by oxygen in the air. Some of the pollutants in sewage are used as active energy (feed) for aerobic microorganisms and some are used for the formation of microbial bodies (sludge). The aerobic microorganisms decompose and oxidize organic matter (solubility) that is not treated by anaerobic microorganisms, converting them into methane gas or carbon dioxide gas to mineralize organic matter. At this time, essential requirements for the growth and growth of microorganisms must be provided. , Air (aeration in air), food (organic matter content in sewage), and temperature (15-30 ° C) should be properly equipped to achieve the best treatment.

Aerobic treatment methods include standard activated sludge method, long-time width method, step wiping method, contact stabilization method, inhalation method, oxidizing method, cyanobarbital contact method (CNR), microbial naturally purifying method (Bio-Reactor) (HBC), and rotating disc contact method (RBC). The anaerobic / aerobic concurrent methods include batch activated sludge (SBR), high-level treatment of manure high concentration organic wastewater, (KSST), anaerobic contact aeration system (KSST), soil type contact method (CNR), anaerobic and aerobic contact circulation method (SCS), liquid corrosion method, microbial control method (KDHST), KS BNR method, intermittent aeration method , Soil trench method, membrane separation method, and oxidation method.

According to an embodiment of the present invention, there is provided a sewage treatment method comprising: a) an anaerobic treatment step of introducing sewage into an anaerobic tank without oxygen; b) an aerobic or anaerobic treatment step of introducing the anaerobically treated sewage into an aeration tank having a dissolved oxygen concentration of 1.0-2.0 mg / L or an oxygen-free anoxic tank having an oxygen concentration of 0.1 mg / L or less; And c) introducing the aerated or anaerobically treated sewage into an aeration tank containing a flotation-packed treatment water tank, wherein the aeration tank has an aerated treatment concentration of 1.0-2.0 mg / L, The filter material can be backwashed through an operation of taking out the treated water tank filled with the floating filter medium outside the aeration tank.

In the present invention, the anaerobic treatment step in step a) is carried out by introducing sewage into an anaerobic tank having no oxygen at an oxygen concentration of 0 mg / L, whereby denitrification and release of soluble phosphorus are caused by anaerobic microorganisms.

In the present invention, the aeration or anaerobic treatment step in the step b) is operated in an anoxic tank so as to perform anaerobic treatment when nitrification nitrate is sufficiently performed during the inflow of sewage and a nitrate nitrogen (NO ₃ ^- ) of a high concentration is introduced, Ion (NH ₄ ⁺ ) If there is a lot of nitrogen component and nitrification is to be performed first, it operates as an aeration tank.

According to the present invention, in the aeration treatment step of step c), when a sewage is introduced, a microbial film is formed on the floating filter material filled in the floating filter material treatment tank, and organic matter is decomposed by the formed film and further nitrification is performed .

According to an embodiment of the present invention, the steps a) to c) may be operated at a hydraulic retention time of 2-6 hr, It can be operated with hydraulic retention time of 3-5 hrs for 30-100 days, and hydraulic retention time of 2-3 hrs for 100-140 days.

The hydraulic retention time means a time period during which a fluid at a constant flow rate can be retained in a given set. The hydraulic retention time is calculated as follows. It may also represent the mean time for a soluble compound to remain in the designed bioreactor.

A shorter hydraulic retention time can shorten the treatment time and bring the system compact, but generally the removal efficiency tends to decrease when treated with short HRT. However, the present invention has developed a sewage treatment method having a short HRT with excellent treatment efficiency through control of aeration or anaerobic treatment, floating media and sludge return.

According to one embodiment of the present invention, the wastewater treatment may be used for small to medium sized wastewater treatment with a treatment capacity of 25-125 m < ³ > / day, It is appropriate that the treatment capacity is 100 m ³ / day.

In one embodiment of the present invention, the sewage was maintained at a mixed liquer suspended solid (MLSS) concentration in the range of 2500-3500 mg / L during the experiment.

The MLSS is also referred to as mixed liquid suspended solids, and refers to the average suspension concentration (mg / L) of the mixed liquid in the aeration tank in the activated sludge process. For good sludge treatment, it is necessary to adjust the MLSS to an appropriate range. It is also used to estimate the F / M ratio, which is an indicator of the amount of microorganisms in the aeration tank. The higher the MLSS, the smaller the BOD load and the smaller the bubble formation in the aeration tank. On the other hand, when the MLSS is too high, the sludge does not settle in the final sedimentation tank, which is ideal for the growth of bacteria and fungi in the activated sludge of the biological wastewater treatment system. bulking. When it is difficult to measure MLSS daily in the operation management, the sludge settling rate (30 minutes SV) is measured for 30 minutes and used as an index of MLSS. The return sludge rate for maintaining proper MLSS concentration is calculated by the following formula It is recommended.

R = MLSS-Cp / Cr-MLSSX100

In the above equation, R means the sludge conveyed, Cp means the SS (suspended solids) of the raw water, and Cr means the SS of the conveyed sludge.

According to an embodiment of the present invention, the step c) includes the step of introducing the aerated or anaerobic treated wastewater into the aeration tank containing the flotation tank filled with flotation media, So that the backwash water can be backwashed through the backwashing operation of the flushing water.

Small and medium scale sewage treatment methods using floating filter media developed to meet site limits and more stringent effluent regulations were developed in Europe in the early 1990s for the treatment of biological aerated filters (BAFs) It is a kind of technology that simultaneously removes organic matter and nitrogen by using microorganisms adhering to the surface of the filter media as well as the physical filtering function of the filter media.

The present invention is a process in which organic matter removal and nitrification by a microorganism attached to the surface of a charged floating filter material occurs simultaneously with physical filtration by a biological filter material layer, and it is advantageous that a small area is small and maintenance is easy have. In recent years, as the regulation of total nitrogen has been strengthened, the present invention requires an additional denitrification process, so that an independent anaerobic tank has been introduced at the front end of the process. In the next stage, a selective tank is operated as an anoxic tank or an aeration tank .

The aeration tank and the floating filter medium treatment tank, which are the core processes of the present invention, operate in a state where a reactor filled with floating filter media at a rate of 50 to 60% is accommodated in a conventional activated sludge aeration tank, It is a reaction tank in which microorganisms are mixed. In a typical floating filter medium tank, the floating filter media float in the aeration tank, so it may be lost by overflowing the aeration tank. Therefore, a separate facility is needed to prevent this. However, in the present invention, the floating filter medium is accommodated in the aeration tank while being confined in a separate reactor, thereby facilitating the maintenance of the floating filter medium while preventing the floating of the floating filter medium. Optimized suspended growth of the aeration tank As the organic matter is removed by the microorganisms, it is possible to remove the nitrogen particularly by SS, Escherichia coli and nitrifying microorganisms in the adherent microorganisms by floating media and adherent microorganisms. The final treated water is sucked and produced from the floating filter medium filling reactor by a pump.

In general biogenic aerobic filtration process, excessively grown adherent microorganisms and floating substances on the surface of the charged floating filter material are filtered to cause clogging in the filter media, resulting in excessive pressure for producing the treated water, diffusion of dissolved oxygen into the biofilm And thus there is a problem that the offensive odor is generated due to the anaerobicization inside the reaction tank or the effluent quality is deteriorated by the separation of the microorganisms. Therefore, it is necessary to periodically backwash the biomass to remove excess biomass. In the biological aerobic filtration process, the final treated water is used for backwashing and the treated backwash water is returned to the first stage anaerobic tank. Therefore, cyclic backwashing in biological aerobic filtration process is one of the important factors to determine the efficiency of the reactor. Determination of the optimum backwash cycle is important to improve process efficiency and economical efficiency by stabilizing the treated water quality and minimizing backwash water quantity. The present invention can perform effective backwashing without requiring additional backwash water for backwashing, and can also stably maintain the quality of the treated water.

On the other hand, one of the advantages of the biological aerobic filtration process is that by maintaining the proper DO concentration in the reaction tank, a DO concentration gradient is formed in the adherent microbial floc and the nitrification reaction proceeds on the floc surface, The nitrate nitrogen and the electron donor produced in the process can induce a simultaneous nitrification / denitrification reaction in which denitrification proceeds by denitrifying microorganisms. However, since the nitrifying microorganisms are slow in growth rate and sensitive to temperature, DO concentration, pH, etc., frequent backwashing can not maintain a high concentration of nitrifying microorganisms.

Therefore, in the present invention, the floating filter material treatment tank impregnated once / 12 hours to once / 18 hours with a backwashing method for alleviating the clogging of the floating filter medium and suppressing the desorption of the sensitive nitrifying microorganisms to the maximum, A simple operation of taking out was performed. The treated water tank filled with floating filter media at a ratio of 50% to 60% by only backwashing these operations can be used to regulate the arrangement of floating filter media and to remove excess microorganisms and suspended substances, thereby minimizing the pressure rise due to clogging do. In addition, the nitrification and denitrifying microorganisms, which are easily separated by the conventional backwash using water and air, are well preserved on the surface of the floating filter media, so that the nitrogen removal effect by nitrification and denitrification is particularly excellent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram of an apparatus capable of performing a medium-sized and high-level sewage treatment according to the present invention, and shows the entire structure including a treatment water tank filled with floating filter media. The floating filter media treatment tank is located in a fixed frame of the aeration tank, and air is introduced from below and the treated water is produced by suction of the pump. The fixed frame is a baffle type, Thereby preventing the user from shaking.

2A is a perspective view showing a treatment water tank filled with a floating filter medium according to an embodiment of the present invention. With reference to this, the treatment water tank may have a mesh-type wire mesh at an interval smaller than the diameter of the floating filter medium. That is, the floating filter medium treating water tank is composed of a wire mesh of a mesh whose bottom surface is smaller than the diameter of the floating filter medium, so that air inflow from the bottom is free, but the floating filter medium is prevented from being lost during backwashing. The upper surface has a 2 mm diameter hole for the inflow of the inflow air and a treated water inlet at the center.

FIG. 2B is a graph showing the backwashing process of the floating filter medium. Referring to FIG. 2B, when the floating filter medium tank contained in the aeration tank is discharged from the aeration tank during backwashing, And the floating material that caused clogging.

In one embodiment of the present invention, the floating media may have a density of 800-900 kg / m ³ , a diameter of 3-4 mm, and a specific surface area of 1500-2000 m ² / m ³ , A floating filter material having a density of 870 kg / m ³ , a diameter of 3.8 mm, and a specific surface area of 1750 m ² / m ³ can be used. The floating filter material may be any one selected from the group consisting of expanded polypropylene, polypropylene, polyethylene, polystyrene, and ethylene vinyl acetate. Since the floating filter medium having density, size, specific surface area, and material has relatively high density (but less than water), fine pores are not formed in the aeration tank. However, due to the nature of floating filter medium, the floating filter medium treatment tank is taken out of the aeration tank It is possible to perform backwashing only by the operation, and thus it is possible to save the treated water and air used in backwashing the existing floating filter media. In addition, backwashing by simple manipulation of floating filter media can improve nitrogen removal efficiency by nitrification and denitrification by preserving the nitrifying and denitrifying microorganisms, which have been easily separated by conventional backwashing with water and air, on the surface of floating filter media .

Hereinafter, the present invention will be described in detail with reference to examples. However, these examples are intended to further illustrate the present invention, and the scope of the present invention is not limited to these examples.

≪ Example 1 > Small-scale high-grade sewage treatment

The influent source was sewage from the sewerage system of Inje University and the influent water quality is shown in Table 1 below.

TBOD (mg / L) SBOD (mg / L) SS (mg / L) Escherichia coli (water / L) COD _Mn (mg / L) NH ₄ -N (mg / L) TN (mg / L) TP (mg / L) 86-172 12-73 60-330 330-2400 120-185 11-22 13-27 1.5-3.8

A total of 200 l of 50 cm x 40 cm x 100 cm (height x width x length) devices were used and operated for a total of 140 days from October 8, 2014 to February 24, 2015. The HRT value was adjusted by changing the flow rate to have a value of 2-6 hr. Specifically, it was adjusted to 5-6 hrs from the start of sewage treatment to 30 days, 3-5 hrs from 30-100 days, and 2-3 hrs from 100-140 days.

Sewage passing through the screen was introduced into an anaerobic tank without oxygen, and then temporary anaerobic treatment was performed. The anaerobically treated sewage was introduced into the next step, select, and treated with anoxic tank or aeration tank according to the removal efficiency of the whole process. After 30 days from the start of operation, it was operated as anoxic tank and then operated as aeration tank. The total nitrogen concentration in the effluent was somewhat higher during the anoxic tank operation, but the total nitrogen removal rate was stabilized by the operation of the aeration tank. Anoxic or aerated sewage was aerated by aeration tank with dissolved oxygen concentration of 1.0-2.0 mg / L.

The floating filter media inside the aeration tank is filled with floating filter media made of polypropylene having a density of 800-900 kg / m ³ , a diameter of 3-4 mm, and a specific surface area of 1500-2000 m ² / m ³ Not only performs the filtration function when sewage is introduced, but also forms a microbial film on the surface of the floating filter media to perform decomposition of organic matter. A simple operation was performed to take out the floating filter material treatment tank impregnated in a period of 12 hours with the backwashing method for alleviating clogging of floating filter media after sewage treatment and to suppress the desorption of sensitive nitrifying bacteria as much as possible (Figures 1 and 2 Reference).

< Example  2> Floating media  Evaluation of removal rate by density and filling rate

Two different materials and characteristics of floating media were used to evaluate the removal rate by different loading rates (50%, 75%, 100%). The characteristics of the two floating media (A, B) are as follows.

A: foamed polystyrene material, diameter 3 mm, density 25 kg / m ³ , specific surface area 2000 m ² / m ³

B: polypropylene material, diameter 3.8 mm, density 870 kg / m ³ , specific surface area 1750 m ² / m ³

The operation was performed with a hydraulic retention time (HRT) of 5 to 6 hr for the first 5 to 6 hrs and then a final HRT of 2 to 3 hrs. Table 2 shows treatment efficiencies of the floating filter media A and B by different packing ratios. The treatment efficiency is the average value of the efficiencies operated in different HRTs.

Removal rate by floating media A (%) Removal rate by floating media B (%) Charging rate (100%) Charging rate (75%) Charging rate (50%) Charging rate (100%) Charging rate (75%) Charging rate (50%) TBOD 96.6 92.4 87.6 92.4 88.4 85.1 SBOD 94.6 93.2 86.5 92.7 91.5 89.5 SS 97.9 93.2 86.5 92.6 84.8 78.7 COD 91.7 88.6 84.1 89.7 85.1 85.0 Escherichia coli 92.6 86.7 78.2 87.1 78.4 75.6 TN 69.3 67.3 66.5 88.9 84.5 76.4

As both filler ratios were lower, the treatment efficiency of all items decreased. This is a sufficiently predictable result that, if the filling rate is high, more soluble substances can be removed by more adherent microorganisms as well as removal of the floating matter due to the greater physical filtration effect. From this result, it can be said that high filling rate is advantageous in terms of stabilization of the treated water quality, but since the high filling rate causes more clogging due to filtration and requires more backwashing to solve it, . In this respect, although the filling rate was reduced to 75% and 50%, the removal rate remained mostly above 80% except for some items.

The removal rate by floating media B was somewhat lower in all items except TN than the removal rate by floating media A, because the higher density of floating media B formed looser pores. The loose pores can also be confirmed by the fact that the removal of SS and Escherichia coli, which are especially suspended substances, is lowered by floating material B. The solubility of SBOD, COD and TN was not much worse than that of floating media A.

In particular, the removal rate of TN was significantly better than that of floating media B because of the different backwashing methods applied to the two media. It is assumed that floating particulate material A was sprayed with water and air for 5 to 10 seconds from the direction opposite to the treatment direction, so that some adherent microorganisms, especially nitrifying microorganisms, were desorbed during this process. On the other hand, the floating filter medium B was backwashed only by removing the floating filter media from the aeration tank. Thus, the nitrifying microorganisms, which are slow in growth and sensitive to the surrounding environment, could be well preserved on the surface of the filter media.

< Example  3> Floating media  Density and HRT In accordance Backwash  Performance evaluation

Since the floating filter material A of Example 2 was a foamed polystyrene material and had a very low density, a fine pore was formed due to a strong float upon impregnation into the aeration tank. Therefore, the backwashing was performed by spraying the treatment water in the direction opposite to the treatment time for about 5 to 10 seconds until the clogging was sufficiently solved in visual confirmation. Since the floating material B of the second embodiment has a relatively high density (but less than water) as a polypropylene material, fine pores as large as the floating filter material A are not formed during the aeration tank impregnation. However, due to the characteristics of the filter material, It was possible to perform backwashing only by an operation of pulling out. The backwash effect for floating media A and B was confirmed by the pressure before and after backwash. As a result, both backfill media were sufficiently backwashed by the above operation, and the pressure almost returned to the initial value. The average pressure increase values obtained in the backwashing operation after 12 hours of filtration operation in the operation of the different hydraulic retention time (HRT) are shown in Table 3 below.

(-) pressure rise (kg _f / cm ²⁾ HRT 5-6 hours HRT 3-5 hours HRT 2-3 hours Floating media A 1.54 2.76 4.08 Floating media B 0.53 1.16 1.78

As the filtration progresses, the pores of the filter material are blocked by the contaminants and the resistance increases. This can be confirmed by the number of losses or the increase of the pressure. Since the treatment apparatus according to the present invention has a structure in which the treated water is sucked and produced in the floating filter medium treatment tank impregnated in the aeration tank, the increase in resistance due to clogging of the filter media becomes an increase in the negative pressure. Therefore, a larger (-) pressure means that more clogging has occurred and that backwashing to solve the problem requires more energy.

As shown in the results of Table 3 above, (-) pressure is increased as the HRT is shortened in both floating media A and B. Also, it can be seen that the pressure rise of the floating filter medium B is much lower than that of the floating filter medium A. This is because of the relatively high density and large size of the floating filter medium B, the clogging due to the floating material was relatively small because the pores of the larger and loose structure were formed.

The average pressure values measured while performing backwash after filtration for 24 hours in the same experiment are shown in Table 4 below.

(-) pressure rise (kg _f / cm ²⁾ HRT 5-6 hours HRT 3-5 hours HRT 2-3 hours Floating media A 4.48 8.83 11.63 Floating media B 1.26 2.94 4.12

When the filtration duration was increased from 12 hours to 24 hours, the rise in pressure was about three times higher than that of floating media A, and the frequency of floating media B was about 2.4 times higher. Since the increase of the pressure due to the increase of the filtration duration was also low in the floating filter medium B, the floating filter medium B showed better results in terms of pressure increase due to filtration and backwashing. In addition, the operation performed with the floating filter medium B can be performed by backwashing only the operation of removing the floating filter medium impregnated with the aeration tank from the aeration tank, thereby saving the water and air used in the backwashing of the floating filter medium A . In addition, the simple operation of backwashing of floating filter medium B also has a great advantage of protecting noxious bacteria that are sensitive to the surrounding environment, which is difficult to grow on the surface of filter media.

< Example  4> Small and Medium Scale Advanced sewage treatment  Operation result

The values of TBOD (total BOD), SBOD (soluble BOD), SS (suspended solids), COD (chemical oxygen demand), coliform counts, NH ₄ -N, TN and TP values of the influent and effluent during the 140- Respectively.

As a result, the TBOD value was stable below 5 mg / L in effluent after treatment regardless of influent water quality (86-172 mg / L) and 2-6 hr flow rate change. The removal rate was 95% or more for 140 days (see FIG. 3).

The SBOD value was stable at less than 3 mg / L in effluent after treatment regardless of influent water quality (12-73 mg / L) and 2-6 hr flow rate change. The removal rate was more than 90% for 140 days (see FIG. 4).

SS values were stable at less than 10 mg / L in effluent after treatment regardless of influent water quality (60-330 mg / L) and 2-6 hr flow rate change. The removal rate was 95% or more for 140 days (see FIG. 5).

The COD value was stable at 20 mg / L or less and 10 mg / L or less for effluent after treatment regardless of influent water quality (120-185 mg / L) and 2-6 hr flow rate change. The removal rate was more than 90% for 140 days (see FIG. 6).

The number of E. coli was stable at 100 ml / L or less in effluent after treatment regardless of influent water quality (330-2400 / L) and 2-6 hr flow rate change. The removal rate was more than 90% for 140 days, but the removal rate decreased to less than 85% when the flow rate was 2-3 hr (see FIG. 3).

NH ₄ -N values were less than 10 mg / L in effluent after treatment, regardless of influent water quality (86-172 mg / L) and 2-6 hr flow rate change, but the treated water quality decreased at low temperature. In October and November, the treatment efficiency was more than 80%, but in the winter of December to February, the treatment efficiency was 50-70% (see FIG. 8).

The T-N values were stable at less than 10 mg / L in effluent after treatment regardless of influent water quality (13-27 mg / L) and 2-6 hr flow rate change. The treatment efficiency was 60-80% for 140 days, but the treatment efficiency decreased at low temperatures (see FIG. 9).

The T-P values were stable at less than 1 mg / L in effluent after treatment regardless of influent water quality (1.5-3.8 mg / L) and 2-6 hr flow rate change. The removal rate was 70-90% for 140 days (see FIG. 10).

That is, although the sewage treatment according to the present invention was operated at a speed of 2-6 hr, which is shorter than the conventional sewage treatment method, the aeration or anaerobic treatment was performed according to the state of the inflowed sewage, Especially, TBOD, SBOD, SS and COD showed excellent removal rate of more than 90%. Particularly, according to the present invention, it was confirmed that excellent treatment efficiency was maintained even in HRT of 2-3 hr.

In addition, the produced sludge can be transported and recycled to improve the removal efficiency of nitrogen and phosphorus, and the floating filter material filled in the floating filter material treatment tank can be recycled by backwashing, which is also economical.

The present invention has been described above with reference to preferred embodiments thereof. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The disclosed embodiments should, therefore, be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (10)

As a medium and small scale sewage treatment method,
a) an anaerobic treatment step of introducing the sewage into an oxygen free anaerobic tank;
b) an aerobic or anaerobic treatment step of introducing the anaerobically treated sewage into an aeration tank having a dissolved oxygen concentration of 1.0-2.0 mg / L or an oxygen-free anoxic tank having an oxygen concentration of 0.1 mg / L or less; And
c) introducing the aerated or anoxic treated sewage into an aeration tank containing a flotation-packed treatment water tank, wherein the aeration tank has an aerated treatment concentration of 1.0-2.0 mg / L,
The floating filter medium is backwashed through an operation of taking out the floated treatment water tank filled with the floating filter medium out of the aeration tank,
The steps a) to c) are operated at a hydraulic retention time of 2-6 hr,
The hydraulic retention time is 5-6 hr from 1 to 30 days after the start of operation, 3-5 hr from 30-100 days, 2-3 hr from 100-140 days,
The floating filter medium is a polypropylene having a density of 800-900 kg / m ³ , a diameter of 3-4 mm, and a specific surface area of 1500-2000 m ² / m ³ ,
Wherein the floating filter medium is filled in the treatment water tank at a filling rate of 50 to 60%.
delete delete The method according to claim 1,
Wherein said wastewater treatment is carried out with a treatment capacity of 25-125 m &lt; ³ &gt; / day.
The method according to claim 1,
Wherein the mixed liquid in the aeration tank is maintained at a mixed liquer suspended solid (MLSS) concentration in the range of 2500-3500 mg / L.
delete delete delete The method according to claim 1,
Wherein the floating filter media is backwashed at a cycle of 12-18 hrs per cycle.
The method according to claim 1,
Wherein the treatment water tank has a mesh-type wire mesh at a lower portion and at intervals smaller than the diameter of the floating filter medium.

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