KR0164580B1 - A water recycling system using membrane process and operating method thereof - Google Patents

Abstract

The present invention relates to a heavy water system for purifying and reused sewage and wastewater, and a method of operating the same. The flow rate for adjusting the flow rate while temporarily storing the screen 20 connected to the sewage discharge source 10 and the screened sewage is temporarily stored. The control tank 30, the contact oxidation tank 40 for biologically treating the wastewater introduced from the flow rate adjusting tank 30, the membrane raw water supply tank 50 for temporarily storing and supplying the biofilm treated wastewater to the next step, ultrafiltration By providing the optimal water treatment system and its optimum operating conditions, including the ultrafiltration device 60 for discharging the sewage supplied from the supply tank 5 by ultrafiltration membrane, the wastewater can be treated with It can be used for purposes that are not needed, thereby saving water resources and reducing environmental pollution.

Description

Heavy water system using membrane treatment and its operation method

1 is a schematic diagram of a water-based system combining a conventional membrane treatment with a biological treatment.

Figure 2 (a) is a schematic diagram of a water system of the present invention.

(b) is a process flow chart in the system of FIG.

3 is a structural diagram of HBC-Ring which is a medium used in the catalytic oxidation tank of the present invention.

4 is a graph showing the concentration state of the effluent compared to the influent of the oxidizing tank by date.

Figure 5 (a) and (b) is a graph showing the flux (flux) change according to the permeation pressure of the tubular and hollow fiber type ultrafiltration membrane.

6 (a) and (b) are graphs showing the change of permeate flux and per flux pressure of tubular and hollow fiber type ultrafiltration membranes.

7 is a graph showing the power required per 1㎥ of water per pressure.

8 (a) and (b) are graphs showing the change in fluxv according to the inflow flow rate (flow rate) of the tubular and hollow fiber type ultrafiltration membranes.

9 is a graph showing the average flux change with increasing flow rate.

10 is a graph showing the power required per unit permeate according to the increase in flow rate.

11 (a) and (b) are graphs showing flux changes according to cleaning methods.

* Explanation of symbols for main parts of the drawings

10: Sewage discharge source 20: Screen

30: flow rate adjusting tank 40: contact oxidation tank

41: medium fixing frame 42: diffuser

50 membrane raw water supply tank 55 simple settling tank

60: ultrafiltration device 61: membrane module mounting portion

62: inflow pump 63, 64, 68: pressure gauge

65, 66: flow meter 67: backwash pump

The present invention relates to a heavy water system and a method for transporting the same, and in particular, by using the membrane treatment, the sewage and wastewater can be used for applications that do not require high cleanliness such as flush toilets, thereby reducing water resources. The present invention relates to a heavy water system that reduces environmental pollution and a method of operating the same.

The demand for water is increasing rapidly due to the progress of industrialization and the improvement of living standard, but the supply of water is reaching its limit due to the lack of water source, and this situation is getting worse due to the lack of sewage and wastewater treatment facilities. It's getting serious.

Under such circumstances, measures to prevent water pollution have been taken in various ways, and on the other hand, introduction of heavy water is one of the most promising ways to solve water problems more fundamentally.

Water is a facility that cleans and discards used water for many applications that do not require the same level of cleanliness as drinking water, and is used for flush toilets, cooling water, cleaning water, and water. It is based on the type of water consumption that takes up a large part of the total tap water without requiring high cleanliness such as water, car wash, firefighting, etc.The introduction of this water system reduces water volume and saves water resources. In addition, it is expected to reduce the amount of sewage and reduce the environmental pollution caused by sewage pollutants.

The water treatment method in such a water system may be applied to the biological treatment method, physicochemical treatment method, membrane treatment method, etc., which have been used as a water treatment method, but is reasonably selected in consideration of predetermined cleanliness, economy, and practicality. Only then will it be practical to meet expectations.

Conventionally, the water-based water system was introduced in some parts, but there were many problems to be widely used in terms of cleanliness and economics, and there was a problem that frequent shutdowns and water quality irregularities occurred because the operation method was not properly established.

Accordingly, the present invention is one of the methods for solving the water problem by reducing the amount of water by reducing the amount of water source and reducing the amount of sewage by reducing the environmental pollution caused by sewage pollutants, while satisfying the cleanliness of the predetermined cleanliness, which is economical The purpose of the present invention is to provide a method of operating a water system, which can be operated under optimum conditions.

In order to achieve the object as described above, the present invention comprehensively examines the prior art related to water treatment, and on the basis of this process, constructs the water-based water system of the present invention, and directly processes the system to find an optimal operating condition. Was done.

Therefore, the present invention first looks at the prior art associated with water treatment.

BACKGROUND OF THE INVENTION Biological treatments, which have been frequently used for sewage and wastewater treatment, are used to treat organic materials and suspended solids in sewage and wastewater using biochemical metabolism of microorganisms, such as activated sludge treatment and biofilm treatment.

Here, the biofilm method differs from the activated sludge method in which the active microorganisms are suspended in a suspended state in that the active microorganisms responsible for the wastewater treatment are attached to the medium and operated. The biofilm method has the following characteristics and advantages compared to the activated sludge method. Have

① Nitrogen removal rate is high.

② There are many microbial groups involved in the treatment, which can remove a wide range of pollutants.

③ The treatment capacity per unit volume is significantly higher than that of activated sludge method.

④ The amount of excess sludge is small.

⑤ Energy saving and easy operation and maintenance.

⑥ Stable operation efficiency can be obtained.

On the other hand, the biofilm method is difficult to maintain the concentration of microorganisms and influence factors in a normal state, and the phenomenon of closing, peeling and desorption by attached microorganisms cannot be avoided. If the concentration of the influent wastewater is not high, the medium is easily closed.

Such biofilm treatment methods are classified into aerobic treatment method and anaerobic treatment method according to the presence or absence of oxygen supply, and aerobic treatment methods include biofilm filtration method, catalytic oxidation method, fixed bed or fluidized bed biofilm method, and anaerobic rotary disc method. Anaerobic Upflow Sludge Filtration and Anaerobic Biofilm Fluidized Bed Method.

The contact biooxidation process is a method of oxidizing and separating organic substances in wastewater by biochemical reaction by circulating and contacting biofilm formed on the surface of a contact medium filled in water with wastewater. It is also called fixed bed activated sludge method, contact aeration method, immersion filter method, and is classified into side aeration type, front aeration type, central aeration type, etc. according to the circulation method by aeration and swirl flow. This process was developed to compensate for the shortcomings of activated sludge method, but its application is gradually expanding, but there is still much to consider.

On the other hand, the physicochemical treatment uses physical or chemical reactions such as pH adjustment, redox, filtration, adsorption, ion exchange, etc., and is not economical for wastewater treatment.

In the membrane treatment method, the gas phase or liquid mixture is concentrated, separated, and purified by driving force such as concentration difference, pressure difference, or potential difference across the membrane by using the membrane. In the wastewater and water treatment fields, mechanical pressure is mainly used as a driving force, and reverse osmosis (RO), ultrafiltration (UF), and microfiltration are used depending on the size of the particles to be excluded. (microfiltration, MF), etc.

The MF membrane (fine filtration membrane) has a larger process (0.05-10 μm) than other membranes, and thus has a large permeate flow rate, and various fields such as food industry, chemical industry, biochemical industry, as well as wastewater and water treatment fields. In the case of water treatment, suspended solids and bacteria that are not normally removed by sand filtration are the main separation targets. However, due to deterioration of water quality and lack of removal of pathogens such as viruses, it is not suitable for application to heavy water.

The UF membrane (ultrafiltration membrane) has a pore size of about 0.001-0.05 μm, and the subject of treatment in water treatment is a bacterium, colloid, emulsion, protein or polymer component having a molecular weight of about 5,000-300,000. The main advantage of this ultrafiltration membrane is that it is operated at a lower pressure (1-3 kg / m2) than the reverse osmosis membrane described later, and a higher permeate flow rate can be obtained. This UF film is partly used in the field of heavy water in recent years.

In addition, the RO membrane (reverse osmosis membrane) is a semi-permeable membrane through which water is permeable but solutes (ions or molecules) are not permeable. The principle of the RO membrane method is a low concentration solution to a certain equilibrium when a solution having a different concentration exists between the semi-permeable membranes. It is based on the osmotic phenomenon in which the solvent (water) moves from the side to the high concentration solution, and is a method of obtaining purified water from the semipermeable membrane by applying pressure above the osmotic pressure to reverse the osmotic phenomenon. Such reverse osmosis membranes are limited to inorganic ions or low molecular organic materials, and were originally developed as desalination processes for desalination of seawater, but are currently used to produce pure and ultrapure waters for desalination processes and pharmaceutical industries. It is also applied to many desalination processes. On the other hand, considering the application of semipermeable membranes to the field of heavy water, RO membranes operate at high pressure (10-60 kg / m 2) and have a low permeate flux, and when combined with biological treatment, It is considered to be very low in practicality because it may be concentrated and adversely affect microorganisms.

Membrane filtration, on the other hand, is a flow rather than direct filtration or dead-end filtration, in which the solid particles that are excluded by the flow direction are directed perpendicular to the filter media form a block, which significantly reduces the filtrate flux. A cross flow method flowing along this membrane surface is commonly used. This cross-flow filtration method introduces raw water at a high flow rate (approximately 1-2.5m / sec in sewage application) compared to the membrane permeation rate, which increases the pump size, but reduces the accumulation of particles, resulting in stable permeation yield. Not only are they obtainable, but they also have the advantage of extending the life of the membrane.

In membrane filtration processes it is known that permeate flux is proportional to the permeation pressure difference and inversely proportional to the viscosity of the fluid. The viscosity of the fluid is also related to the temperature and concentration of the solution. Therefore, in the case of pure solvent (water) containing no solute, the flux increases linearly by increasing the temperature or increasing the application pressure.

However, when separating membranes containing macromolecules such as colloids or proteins, a linear relationship does not exist between the permeation pressure and the flux and the limiting flux does not increase even if the input is increased above a certain permeation pressure. Will be reached. This is due to concentration polarization caused by the colloidal or polymeric material excluded by the membrane remaining on the membrane surface. Concentration polarization is a phenomenon in which the solute concentration is higher than the feed liquid concentration near the membrane surface because the solute is excluded by the membrane and only the solvent penetrates the membrane. Due to this concentration polarization, a cake layer may be formed on the membrane surface or, in severe cases, a gel layer may be formed. This is also the problem of membrane fouling.

In addition, in order to commercially use membrane separation technology, a module form loaded in a pressure vessel is required to easily pressurize the membrane, and the module may be plate and frame, tubular, or b depending on the form. Spiral wound, hollow fiber (inner pressure type and internal pressure type), and the like. Each of these modules differs in membrane area, membrane cleaning method, and tolerance to suspended substances. Therefore, it is necessary to select an appropriate type of module according to its purpose. On the other hand, there are two types of modules that are currently used for heavy water.

Currently, the membrane separation process is developed for the separation, concentration, and purification of tides and various substances in the production field as inorganic and polymer membranes are developed from various materials with excellent membrane performance and physicochemical stability, and related technologies are developed accordingly. In addition to being used, as technology for effective use of resources and environmental conservation in the field of wastewater treatment, the use of organic materials and water is increasingly being used for recovery and reuse.

In particular, the use of membrane treatment technology for water treatment such as sewage and waste water has the following advantages.

① Multiple components in water can be removed at the same time

② The treated water quality is good and stable.

③ It is suitable for the area where the installation area is small and it is difficult to secure the site.

④ Simple operation and fully automatic.

⑤ Can remove fine particles in water without using flocculant.

⑥ Small amount of sludge is generated.

However, the main reason why the membrane separation process is not widely used despite the above advantages is because of economic problems related to the membrane permeation rate.

In other words, membrane economics should be considered as the most important factor along with 'solid-liquid separation performance' because membrane permeation flux decreases gradually as membrane contamination progresses. Therefore, in order to efficiently operate the membrane separation process, it is important to extend the life of the membrane by at least reducing the rate of degradation of the membrane performance. The degradation of the membrane performance is caused by deterioration and contamination of the membrane itself.

Membrane deterioration may include physical degradation such as darkening or damage of the membrane itself due to pressure, chemical chloride such as hydrolysis, oxidation, and biological degradation in which the membrane material is changed by microorganisms. As a result, the film degradation is irreversibly irreversible, and the only countermeasure is to operate in a condition that does not cause deterioration. Therefore, it is important to select a membrane having excellent resistance as well as pretreatment for removing the deterioration of the membrane.

Membrane fouling is not an intrinsic change in the membrane itself, but a change in membrane performance due to external factors. Such membrane contamination has been found to be highly related to the properties of the membrane, and efforts to change the membrane surface polarity or to improve the membrane material have been made to prevent membrane contamination, while cleaning operations are required during the process.

When the membrane separation process is applied to sewage and wastewater treatment including heavy water, the most common causes of membrane contamination include gel layer formation and pore plugging due to concentration polarization. As the solute remains near the membrane surface, the solute concentration near the membrane surface becomes higher than that of the feed solution, and the dissolved substance may be precipitated to produce scale. In the case of raw water containing a large amount of suspended substances or colloids, a gel layer may be formed. do.

This concentration polarization greatly affects the performance of the RO film and the UF film. In addition to operating at a suitable pressure to prevent the formation of a gel layer as much as possible, the flow velocity near the membrane surface is increased to increase shear force or promote turbulence. However, complete prevention is not possible, so membrane cleaning is sometimes needed to physically remove the gel layer or dissolve it with chemicals.

Pore blockage occurs mainly when the pore size is large, and the material forming the gel layer penetrates into the membrane pore size and blocks, or depending on the membrane material, a specific protein or water-soluble polymer can be pored by chemical affinity. It arises by adhering inside, and it becomes a problem especially in an MF film | membrane with a large pore size compared with other membrane | film | coat.

Membrane fouling is inevitable in the membrane separation process, but in order to reduce the contamination rate as much as possible, the selection of a suitable membrane module (membrane material, membrane type, module type, membrane surface treatment), pretreatment of raw water (pH adjustment, softening ion) Exchanges, scale inhibitors, flocculation, filtration, particulate additions, maintenance of proper operating conditions (flow rates, recovery rates, temperatures), effective cleaning of membranes, etc. are required.

On the other hand, the cleaning method of the membrane is largely physical cleaning and chemical cleaning, the physical cleaning is a method of removing contaminants by blocking the physical force such as water or air, gel or cake layer formed in a relatively short period of time, The cleaning method by flow rate is mainly used, and chemical cleaning is to contact and react with chemicals to decompose or reduce the molecular weight or to easily detach the contaminants which are difficult to remove by physical cleaning.

The use of the above-described film treatment for heavy water is expected to have many advantages as described above, but on the other hand, there are many cases that cause problems in operation due to the large amount of organic or suspended matter in sewage and wastewater (heavy water). In addition, there is an uneconomical problem because membrane contamination becomes easy. Therefore, the use in combination with the above-described biological treatment is under consideration. In fact, some operations seem to be in operation.

FIG. 1 shows an example of the combined biotreatment-ultrafiltration method in which the membrane treatment is biologically treated. The activated sludge method is a form in which the precipitate is replaced with an UF membrane device (ultrafiltration device). This method is superior in solid-liquid separation function compared to the sedimentation basin, and because the organic material such as BOD and COD is removed from the bioreactor, it not only produces high quality permeate but also includes microorganisms that do not pass the UF membrane. By returning the concentrated water back to the bioreactor there is an advantage that can be treated with a high concentration of biological. Therefore, it is possible to maintain the MLSS about twice as high as the conventional activated sludge method, thereby reducing the aeration volume by 1/2. In particular, microorganisms with low growth rate, such as nitrifying bacteria, can be maintained at high concentrations, and thus, there is an advantage in that high processing is possible. .

However, since the biological treatment-ultrafiltration method basically uses the activated sludge method in the biological treatment, there is a problem that the inherent disadvantages of the activated sludge method such as the need for the return of the sludge remain.

Therefore, the present invention introduces the catalytic oxidation method in the biological treatment method as a previous step of the membrane treatment to compensate for the disadvantages of the membrane treatment, the first step is the catalytic oxidation method, the second step is characterized by the ultrafiltration membrane treatment method.

Hereinafter will be described in detail with reference to the accompanying drawings and specific experimental example of the heavy water system and the operation method according to the present invention.

FIG. 2 (a) schematically shows the water system according to the present invention. The screen 20 connected to the wastewater discharge source 10 and the flow rate adjusting tank 30 for adjusting the flow rate while temporarily storing the wastewater being screened ), The contact oxidation tank 40 for biologically treating the sewage introduced from the flow rate adjustment tank 30, the membrane raw water supply tank 50 for temporarily storing the biofilm treated sewage and supplying it to the next step, the ultrafiltration supply tank ( And an ultrafiltration device 60 for discharging wastewater supplied from 5) by ultrafiltration membrane treatment. On the other hand, when the flow of the sewage treatment process in the water system of the present invention as shown in Figure 2 (b).

The ultrafiltration membrane separation device 60 is a batch type to fill a certain amount of contact oxidation tank 40 effluent in the membrane raw water supply tank 50 and to return the concentrated water separated by the membrane back to the raw water supply tank 50 In this case, since the temperature difference (about 5 ℃) is generated between each process before and after due to the heat generated from the raw water supply pump, it is preferable to make it continuous in order to minimize the effect thereof.

On the other hand, in order to continue the membrane separation process, it is necessary to first remove the solids in the effluent of the contact oxidation tank 40. For this purpose, the ultrafiltration supply tank 50, before the outflow from the contact oxidation tank 40 It is better to install a simple settling tank (55) for sedimentation of the outflow water.

The contact oxidation tank 40 is installed in order to biologically remove contaminants such as SS and organic substances in sewage as an ultrafiltration preliminary step, as shown in FIG. As the treated water moves in a zigzag to the next thread, the filling of media in each chamber fixes the HBC-ring to the cuboid-shaped media fixing frame 41, and the mold 41 is 20, 10 at the bottom, side, and water surface, respectively. , 10 cm apart. And in the lower center of the 1,2 chambers and the lower right of the 3,4 chambers, the diffuser 42 is installed to purify the sewage in the form of a central aeration and side aeration, respectively, and supply oxygen.

For example, the specifications of the contact oxidation tank are shown in Table 1 below.

* Reactor material: PVC

Inlet pump: max. 2 units of 8.21 / min diaphram pump (1 spare)

* Air diffuser: max. 2 210 / min Hiblow air pumps (spare 1)

In addition, a medium for allowing microorganisms to attach and multiply in the contact oxidation tank 40 was HBC-Ring (hanging bio contactor-Ring) made of polyvinylidene chloride. This HBC-Ring is a form in which the cyclic polyvinyl chloride fibers are radially attached to the media body, as shown in FIG. 3, and the optimum loads for the incoming BOD and SS are determined according to the treatment capacity. The sewage treatment facility installation standards are announced, which are shown in Table 2 below.

In addition, the simple settling tank 55 has a cylindrical shape of 50 cm in diameter and 65 cm in height, having an effective capacity of 100 l, and a hydraulic residence time of about 2 hours.

In addition, the raw water supply tank 50 has a cylindrical diameter of 35 cm and a height of 50 cm, and an effective capacity of 50 l, in order to minimize the effects of the temperature rise on the upper portion of the raw water and the feed pump introduced from the simple settling tank (55). Due to the increased temperature of the concentrated water was mixed with each other to make a hole 2cm in diameter (not shown) to flow out.

The ultrafiltration membrane separation device 60 has a separation structure so that the membrane module mounting portion 61 can be installed in the tubular and hollow fiber type ultrafiltration membranes in a compatible manner, and the raw water is supplied from the raw water supply tank 50 to supply pressure. An inflow pump 62 is provided. The inflow pump 62 has a flow rate control pump, for example, a rotary vane pump (capacity max. 15 l / min).

Then, the pressure gauge 63 is attached to the inlet side of the membrane module mounting unit 61, another pressure gauge 64 and the flowmeter 65 are attached to the outlet side thereof, and the flowmeter 66 is attached to the permeate side. By measuring the membrane inflow (concentration) and the permeate, the operating conditions can be easily managed.

In addition, a backwash pump 67 of the same type as the inflow pump 62 is installed on the permeate side of the membrane module mounting portion 61 for backwashing during hollow fiber type ultrafiltration operation, and a pressure gauge 68 for pressure control during backwashing. ) Is also installed.

The ultrafiltration membranes used in the ultrafiltration membrane separator 60 are tubular and hollow fiber type (external pressure type), and the specifications thereof are shown in Table 3 as an example.

As described above, the experimental operation was performed with the water-based system according to the specific embodiment of the present invention. The experimental conditions and the experimental results are as described below.

The influent sewage used in the experiment was sewage including kitchen drain, wash and bath drainage, and manure, and its characteristics are shown in Table 4 below.

The operation method or test method is as follows.

That is, the contact oxidation tank 40 was commissioned for one month in order to sufficiently attach the microorganisms required for the sewage treatment on the medium, and the operating conditions of the contact oxidation tank 40 were inflow flow rate 6㎥ / day, hydraulic retention time ( HRT) 24 hours, and the air supply amount is 4.8㎥ / hr in two rooms, 3.6㎥ / hr in two rooms, 1.8㎥ / hr in three rooms, 1.8㎥ / hr in four rooms so that the air supply is 2㎥ air / hr per 1㎥ of oxidation tank. Was injected.

In addition, in order to grasp the change in flux according to the operating conditions such as pressure, flow rate and cleaning conditions in the ultrafiltration membrane device 60, the membrane inflow pressure is 1.0 to 4.0 kgf / in tubular type in consideration of the maximum allowable permeation pressure of the membrane. Up to 2 cm 2, in the case of hollow yarns were increased by 0.5 kgf / cm 2 from 1.0 to 3.0 kgf / cm 2 respectively. At this time, the membrane inflow was kept constant at 12 L / min.

The flow rate was changed to 6, 9, 12, 15 L / min after the membrane inflow was kept constant at 2.5 kgf / cm 2 in the tubular shape and 1.5 kgf / cm 2 in the hollow fiber type.

In addition, the cleaning conditions for increasing the frequency of cleaning and increasing the cleaning time are surface flushing in the case of tubular type, and backwashing in the case of hollow fiber type, but the cleaning time is 30 seconds with the interval of 10 minutes for tubular surface cleaning. It was changed to 60 seconds and 120 seconds, while the cleaning time was fixed to 60 seconds and the cleaning interval was changed to 10 minutes, 30 minutes, and 60 minutes. At this time, the operating conditions were the membrane inflow pressure of 2.5 kgf / cm 2 and the flow rate of 12 L / min, and the washing conditions were the membrane inflow pressure of 1.0 kgf / cm 2 and the flow rate of 15 L / min. In the case of the hollow fiber type, the backwash interval and time were set to 15 minutes, 15 seconds, 30 minutes, and 30 seconds, respectively. At this time, the operating conditions were the membrane inflow pressure of 1.5 kgf / cm 2 and the flow rate of 12 L / min, and the reverse washing conditions were the membrane inflow pressure of 2.5 kgf / cm 2 and the flow rate of 15 L / min. On the other hand, after performing the experiments for each of the above conditions, when the experiment of the following conditions, sufficient surface cleaning (tubular), backwashing (hollow fiber type), chemical cleaning to remove the contaminants so that other variables do not work.

The analysis items and methods in this experiment are shown in Table 5 below. Samples were collected twice a week for analysis. Water temperature, pH, and DO were measured directly at the site. It was analyzed using an analyzer.

The results of the above experiment are as described below.

The performance of the contact oxidizer, that is, the concentration of BOD, COD, and SS of the influent to the influent by day is shown in FIG. 4, and this is shown in a chart for a certain period (before and after the artificial sludge removal operation). Same as

* () Is average

As shown in Table 6 and FIG. 4, the BOD, COD, and SS concentrations of the effluent during the first experimental period were very high, indicating a low removal efficiency, which is due to the severe desorption and deterioration of the aeration tank. This is because the fluctuations in SS of the influent were large and the inflow concentrations of BOD, COD, and SS were high.

During the second experiment period, not only the variation of BOD, COD, and SS concentrations of influent was small but also the influent concentration was relatively low, thus showing relatively high removal efficiency.

From these results, the HBC-Ring medium will vary depending on the interfering substances, aeration method, reactor type, etc., but the BOD and SS loading limits are 150 mg each under the experimental conditions (inflow rate 6㎥ / day, HRT 24hr). It can be seen that / l, about 150mg / ℓ. In addition, when the concentration of the influent water is high, the efficiency of the aeration tank is reduced, if the artificial sludge removal operation has a certain improvement effect, but did not meet the expectations, it is preferable to keep the above load limit.

In addition, as shown in Table 6, the concentration and average removal rate of nitrogen and phosphorus were measured, and the results are shown in Table 7 below.

Table 7 shows that the sludge removal operation has little effect on the removal efficiency of total nitrogen and total phosphorus in the aeration tank.

The experiment on the ultrafiltration membrane separator was carried out during the period when the contact oxidation tank was stable. The temperature of the membrane inflow water (oxidation tank sediment effluent) was 25-27 ° C, and the turbidity was 4-6 NTU (SS 10-15 mg / ℓ). It was carried out under the conditions of, and the result is as follows.

First, the flux change according to the permeation pressure is shown in FIG. 5 (a) for the tubular shape and FIG. 5 (b) for the hollow fiber type, wherein the membrane outlet pressure is 0.5kgf / cm 2 for both the tubular and hollow fiber types. The permeation pressure is obtained by subtracting 0.5 kgf / cm 2 from the membrane inlet pressure.

As can be seen from FIG. 5 (a) and (b), as the permeation pressure increases, both the tubular and the hollow fiber types show not only the initial flux but also the final flux after 2 hours, and shows a constant flux value after the start of operation. The average permeate flow rate after the test was 1.320-2.211ℓ / hr for the tubular shape and 4.453-5.949ℓ / hr for the hollow fiber type at the permeation pressure of 0.5-2.5kgf / ㎠. At the same pressure, the value was more than 2 times higher. However, the average permeation flux was 55-92.11 and 44.53-59.49ℓ / hr · m² in tubular and hollow fiber type under the same pressure condition, so the permeate efficiency per unit area was better than that of the hollow fiber type.

On the other hand, the average permeation flow rate, flux, flux per unit permeation pressure between 1-2 hours after the start of operation was as Table 8 below.

As can be seen in Table 8, the flux increases as the permeation pressure increases, but the flux per permeation pressure associated with the required power of the pump gradually decreases. This is shown graphically in Figures 6 (a) and (b).

The required power according to the permeation pressure can be obtained by the following equations (1) and (2), where P = ωQH Equation 1 where P is power (KW), ω is specific gravity of water (KN / ㎥), and Q is concentrated water quantity (㎥ / s). H is the head of the pump that moves the raw water through the pressure difference.

H = (P-P) / ω Equation 2

(P: membrane inflow pressure (kN / ㎡),

P: membrane outflow pressure (kN / ㎡))

The calculated results are shown in the table below.

7 shows the power required per 1 m 3 of the permeated water in the tubular and hollow fiber types according to the pressure using the results in Table 9. As shown, the power used to obtain the same amount of permeate is increased as the pressure increases, and the case of the tubular shape having a small membrane area is larger than that of the hollow fiber type.

In summary, increasing the permeation pressure increases the flux, but the required power efficiency decreases. If the pressure is high, the membrane fouling rate increases, which may adversely affect the membrane life. Therefore, it is preferable to keep the permeation pressure as low as possible within the allowable flux in consideration of the film area, installation cost, and the like.

The flux change according to the inflow flow rate (flow rate) is shown in FIGS. 8 (a) and (b) for the tubular and hollow fiber types, respectively, wherein the permeation pressure is 1.5 kgf / cm 2 for tubular and 1.0 kgf for hollow fiber. / Cm 2, and the inner diameter was 12.5 mm in the tubular shape, so that the flow rate can be calculated for the flow rate value. However, in the case of the hollow fiber type, the passage area is not known, and thus the flow rate cannot be calculated.

Figure 9 shows the average flux value between 1-2 hours of operation, and it can be seen that the flux increase is greatest when the flow rate is increased from 6 to 9 l / min in both the tubular and hollow fiber types, taking into account the required power of the pump. When the flow rate is 9-10l / min (1.2-1.3m / sec) is preferable that about.

Figure 10 shows the results of calculating the power required to obtain the unit permeate amount according to the flow rate increase at the penetration pressure of the tubular 1.5 kgf / cm 2 and the hollow fiber type 1.0 kgf / cm 2. Similarly, it can be seen that the hollow fiber type has a much smaller increase in power required to obtain the unit permeate with increasing flow rate. This means that the hollow fiber type with a large membrane area has less power than the tubular type when improving the permeate flux when increasing the pressure or flow rate.

The flux change according to the cleaning method (cleaning time and cleaning interval), in particular, the physical cleaning method is as shown in Figs. 11 (a) and (b) in the case of tubular type, wherein the cleaning method uses 1 kgf / cm 2 of raw water. A flow rate of 15 l / min was introduced at the pressure. As can be seen from the figure, the change in flux when the cleaning interval was changed was more significant than when the cleaning time was changed, and the shorter the cleaning interval, the higher the flux value was maintained.

From the above results, it can be seen that when cleaning the surface with the same amount of raw water, a shorter cleaning interval and time than the longer cleaning interval and time are effective.

Finally, the results of analyzing the water quality of the effluent flowing through the membrane were as shown in Table 10 below.

As can be seen in Table 10, the permeated water quality was no difference between the tubular and hollow fiber type, it can be seen that all the items satisfy the water quality standards of Korea as shown in Table 11 below.

On the other hand, the reason why the pH of the membrane inflow water (contact oxidant effluent) is lowered is that the NO-N concentration (13.13 mg / l) of the membrane inflow water is significantly higher than the NH-N concentration (2.17 mg / l). This may be due to the active nitrification in the aeration tank. Therefore, there is a need to prevent the effect (pipe corrosion) caused by the pH decrease.

From the results of the above experiments, the operation method of the heavy water system according to the present invention firstly, when the SS fluctuation range of the influent is large, and the BOD, COD, SS inlet concentration is large, the medium of the contact oxidation tank has a severe desorption phenomenon, and When the sludge removal efficiency is high due to the high concentration of the influent, the sludge removal operation did not meet the expectations. Therefore, it is preferable to keep the load limit (150 mg / l, respectively) for the BOD and SS of the microbial medium. Increasing the pressure increases the flux but the required power efficiency decreases.As the pressure increases, the membrane fouling rate increases, which may adversely affect the life of the membrane.The permeation pressure is determined by considering the membrane area and installation cost. It is desirable to keep as low as possible within the acceptable range.

Third, when the flow rate is increased from 6 to 9ℓ / min in both tubular and hollow fiber types, the flux increase is the largest. Therefore, the flow rate is 9-10ℓ / min (1.2-1.3m / sec, considering the pump's required power). Fourth, like the increase in pressure, the power required to obtain the unit permeate with the increase of the flow rate is much smaller than that of the hollow fiber type. Therefore, when the permeation flux is increased when the pressure or flow rate is increased, The large hollow fiber type is advantageous in terms of power consumption compared to the tubular type. Fifth, when cleaning the surface with the same amount of raw water, a shorter cleaning interval and time than a longer cleaning interval and time can be seen.

As described in detail above, the present invention provides a method of operating a water-based water system that allows the operation of the water-based water system according to the present invention, while satisfying a predetermined degree of cleanliness, while being economical and practical. As a result, the amount of water is reduced to save water resources, and the amount of sewage is reduced to reduce environmental pollution by sewage pollutants. Accordingly, it helps to efficiently solve the water problem that has recently emerged as a serious problem.

Claims (6)

The screen 20 connected to the wastewater discharge source 10, the flow rate adjusting tank 30 for adjusting the flow rate while temporarily storing the sewage coming out of the screen treatment, the contact oxidation tank for biologically treating the wastewater introduced from the flow rate adjusting tank 30 ( 40), the membrane raw water supply tank 50 for temporarily storing the biofilm treated sewage and supplying to the next step, and the ultrafiltration device 60 for discharging the sewage supplied from the raw water supply tank 50 by ultrafiltration treatment. In the heavy water system configured to include, the ultrafiltration device 60 is installed on the membrane module mounting portion 61 of the ultrafiltration membrane, so that the membrane module mounting portion 61 can be installed in the tubular and hollow fiber type ultrafiltration membrane in a compatible manner. Water-based system characterized in that the separation structure. The backwash pump (67) is provided on the permeate side of the membrane module mounting portion (61) for backwashing during hollow fiber type ultrafiltration, and the backwash pump (67) is provided for pressure control during backwashing. Heavy water system, characterized in that the pressure gauge (68) is installed. The screen 20 connected to the wastewater discharge source 10, the flow rate adjusting tank 30 for adjusting the flow rate while temporarily storing the sewage coming out of the screen treatment, the contact oxidation tank for biologically treating the wastewater introduced from the flow rate adjusting tank 30 ( 40), the membrane raw water supply tank 50 for temporarily storing the biofilm treated sewage and supplying to the next step, and the ultrafiltration device 60 for discharging the sewage supplied from the raw water supply tank 50 by ultrafiltration treatment. In the operation method of the system for purifying sewage and wastewater by using a heavy water system including the water, the contact oxidation tank (40) microbial medium load to 150 mg / L or less for influent BOD and SS Water supply system characterized in that the giving. The method of claim 3, wherein the permeation pressure of the ultrafiltration membrane is maintained in the range of 1.0 to 4.0 kgf / cm2. The method of operating a water-based water system according to claim 3, wherein the flow rate of the ultrafiltration membrane is 9-10 L / min. The method of claim 3, wherein the ultrafiltration membrane is cleaned at a cleaning interval of 10 to 60 minutes and a cleaning time of 30 seconds to 60 seconds.