KR20090037236A - System for producing reusable water from waste water - Google Patents

Abstract

A method for manufacturing a reusable water production system is provided to offer an improved concentrated water processing. A reusable water production system includes a preprocessing unit, a reusable water production unit(3), and an concentrated water processing unit(4). The preprocessing unit produces first processed water by removing nitrogen components and organic compounds in the sewage by using a membrane bioreactor. The preprocessing unit is the membrane bioreactor unit including an anoxic chamber(5), an aeration tank(6) and separating film module(8). A filter tub includes a filter(12) filtering phosphorous-containing aggregates in the concentrated water.

Description

Recyclable Water Production System {System for producing reusable water from waste water}

FIELD OF THE INVENTION The present invention relates to "water treatment systems" and, more particularly, to "System for producing reusable water from waste water."

As is well known, reusable water from waste water refers to domestic or industrial water obtained by treating sewage, and a recycled water production system means a sewage treatment system for obtaining living water or industrial water from sewage. do.

In the past, it has been common to discharge sewage treatment water discharged from sewage treatment plants into rivers. However, as the need to reduce the load on the development of water resources emerges, the importance of reuse of sewage treatment water is increasing. As a result, reuse of sewage treatment water is mandatory, and standards for recommending water quality for reuse water are being prepared.

The recycled water production system may be configured based on various water treatment processes that can appropriately remove contaminants contained in the sewage treatment water so that the recycled water has a water quality suitable for the purpose of use. For example, from a simple system suitable for producing low-quality recycled water consisting of solid-liquid separation and disinfection processes, to complex systems suitable for producing high-quality recycled water combined with physical, chemical and biological treatment processes. System is proposed. In particular, in the case of a recycled water production system for obtaining high-purity water such as cooling water or boiler water, there is an increasing number of cases based on filtration processes using nanomembrane or reverse osmosis membrane.

Note that, for example, in the case of a recycled water production system based on a filtration process using a separation membrane such as a nano-membrane or reverse osmosis membrane, the treatment of concentrated water is a new problem.

Concentrated water is water that is not included in the recycled water, and is water in which contaminants such as solutes and suspensions are concentrated. Sewage treated water supplied to the recycled water production system is separated into recycled and concentrated water. Recycled water is water that has passed through the membrane, and concentrated water is water that has not passed through the membrane. Therefore, contaminants that did not penetrate the membrane are concentrated in the concentrated water. Also, the higher the recycled water recovery rate, the worse the quality of the concentrated water.

Such concentrated water must be disposed of by expensive waste disposal procedures, such as, for example, discharged to distant seas. It is known that the amount of concentrated water is about 50% of the amount of influent sewage water. Thus, the cost of disposal of the brine can be a serious economic burden, and thus can seriously degrade the economic efficiency of the recycled water production system.

In order to dispose of the concentrated water without expensive waste disposal procedures, it is desirable to improve the quality of the concentrated water to a quality that can be discharged to the river by adding a separate process for removing contaminants concentrated in the concentrated water.

An example of an additional process for treating such concentrated water is disclosed in Korean Patent Publication No. 10-0550976. In this patent document, activated carbon adsorption equipment is used to remove contaminants in concentrated water. However, it is known that the concentrated water passed through the activated carbon adsorption facility still contains a high concentration of salt, so that the treated concentrated water is eventually discharged to the sea.

Therefore, there is an urgent need for improved concentrated water treatment means that can improve the quality of the concentrated water, for example, to the extent that it can be discharged to a river.

The present invention seeks to provide a recycled water production system and a brine treatment unit employing improved brine treatment means.

Recycled water production system of the present invention,

A pretreatment unit employing a MBR (membrane bio-reator) for producing primary treated water by removing nitrogen components and organics from the influent sewage;

A recycled water production unit employing a nanomembrane or a reverse osmosis membrane that separates the primary treated water into recycled and concentrated water; And

A concentrated water treatment unit for removing the phosphorus component of the concentrated water;

It includes.

The concentrated water treatment unit of the present invention,

A flocculation tank for introducing a flocculant for phosphorus-containing substances into the concentrated water to agglomerate the phosphorus-containing substances in the concentrated water, thereby forming a phosphorus-containing substance aggregate in the concentrated water; And

It includes; a filter tank is installed to filter the phosphorus-containing material aggregates in the concentrated water introduced from the flocculation tank.

In the present invention, in general, the wastewater is produced by combining a biological treatment process (MBR) and membrane separation using nano / reverse osmosis membranes. By incorporating technologies that enable the discharge to a satisfactory level, we have provided an eco-friendly and economical integrated recycled water production system.

Accordingly, various waste and waste water can be produced as recycled water having higher quality than industrial water such as cooling water, boiler water, dyeing water, and the like, and thus, it is possible to supply highly stable and high quality alternative water resources to various industrial complexes.

In addition, the existing consignment process for the treatment and disposal of concentrated water, which is one of the difficulties in preparing large-scale and large-scale facilities in the application of nano / reverse osmosis membranes, especially for recycling wastewater and wastewater, has been made. (Evaporation, drying, and others), rather than the concept of proper discharge in the field can be solved.

Hereinafter, the recycled water production system of the present invention will be described in more detail. The recycled water production system of the present invention includes a pretreatment unit, a recycled water production unit, and a concentrated water treatment unit.

The pretreatment unit removes nitrogen components and other organic matter in the influent sewage to produce primary treated water which is supplied to the recycled water production unit. The pretreatment unit employs a MBR (membrane bio-reator) process. In such a pretreatment unit, nitrogen components and organic matter in the influent sewage can be removed, for example up to about 90% by weight, through biodegradation and filtration processes. In particular, the nitrogen-containing material in the influent sewage can be effectively removed, for example, by nitrification and / or denitrification by microorganisms in the MBR process. Subsequently, the concentrated water and the recycled water generated in the recycled water production unit are derived from such primary treated water, and thus have a very low nitrogen content.

In the MBR process of the pretreatment unit, not only the nitrogen component but also the phosphorus component can be removed. However, if the simultaneous removal of the nitrogen and phosphorus components is intended, it may not be easy to maximize the removal efficiency for each of the nitrogen and phosphorus components, depending on the process conditions. In particular, due to the characteristics of the biological process associated with the removal of nitrogen and phosphorus and the small amount of sludge waste in the MBR process, it is known that the phosphorus removal ability of the MBR process tends to be somewhat inferior. In addition, in the recycled water production system of the present invention, phosphorus-containing materials can be removed from the brine treatment unit. Therefore, the MBR process of the pretreatment unit is preferably configured to be suitable for the removal of the nitrogen component, rather than the simultaneous removal of the nitrogen component and the phosphorus component. Further, it is more preferable to remove about 90% by weight or more of the nitrogen component in the influent sewage through the MBR process of the pretreatment unit. Of course, when the simultaneous removal of the nitrogen component and the phosphorus component is easy, it is not necessary to exclude the possibility of effective simultaneous removal of both. If it is necessary to increase the phosphorus removal load in the MBR process, for example, a biological phosphorus-removing process such as an anaerobic tank may be further added to the MBR process.

Suitable MBR processes for nitrogen removal include, for example, anoxic baths; Aerobic tank; And a separation membrane immersed in an aerobic tank may be used. The influent sewage is first fed into an anaerobic tank and then sent to an aerobic tank. In the aerobic tank, an oxidizing environment based on dissolved oxygen is established. Therefore, in an aerobic tank, the nitrification reaction of nitrogen-containing thing by nitrification microorganisms (for example, nitrosomonas, nitrobactor, etc.) advances. When the sewage in the aerobic tank is returned to the anaerobic tank, in the anoxic tank, denitrification reaction from the nitrified nitrogen-containing substance occurs by denitrifying microorganisms (for example, bacillus, pseudomonas, micrococcus, etc.). Through this process, the nitrogen component in the influent sewage can be effectively removed. In this MBR process, the sewage drawn out through the membrane immersed in the aerobic tank is the first treatment water. Therefore, the primary treated water drawn out through the membrane immersed in the aerobic tank has a very low TN (total nitrogen content) value. The larger the ratio of the amount of sewage return from the aerobic tank to the anoxic tank, the higher the removal rate of the nitrogen component by the nitrification-denitrification reaction, and the lower the total nitrogen content in the primary treated water. In addition, as the sewage retention time (proportional to the tank capacity) in the anoxic tank is increased, the progress of the denitrification reaction increases, so that the removal rate of the nitrogen component is increased.

More preferably, the influent sewage supplied to the MBR process of the pretreatment unit is sewage from which coarse solids are removed through the settling basin and / or screen. This is because it is possible to prevent the clogging of the separator in the MBR process due to the coarse solids.

The MBR process has a mixed liquor suspended solids (MLSS) concentration, for example, up to about 5,000 to about 15,000 mg / l, compared to conventional activated sludge processes (CAS). Since it can be kept much higher, it is possible not only to reduce the volume of each reactor, but also to significantly reduce the withdrawal / disposal amount of sludge generated in the pretreatment unit. Therefore, the recycled water production system of the present invention employing the MBR process can ensure a very high recycled water production efficiency.

The recycled water production unit separates the primary treated water supplied from the pretreatment unit into recycled water and concentrated water using a nanomembrane or reverse osmosis membrane. The primary treated water that has passed through the nanomembrane or reverse osmosis membrane becomes recycled water without contaminants and is discharged from the recycled water production system. The primary treated water that did not penetrate the nanomembrane or reverse osmosis membrane becomes concentrated water with concentrated contaminants and is supplied to the concentrated water treatment unit.

The nanomembrane or reverse osmosis membrane of the recycled water production unit may have a high salt rejection rate, for example of about 90% or more. Thus, the recycled water produced in the recycled water production unit may have a higher quality of water, such as, for example, the quality of water available for industrial water.

In the recycled water production unit, the recovery rate (that is, the ratio of recycled water production flow rate to the inflow flow rate of the primary treated water) is not particularly limited, but in general, in consideration of stable operation of the nanomembrane or reverse osmosis membrane, 50 to about 75% can be maintained. However, if the recovery rate is too high, both the quality of recycled water and the quality of concentrated water can be deteriorated. In particular, the solute concentration in the brine may rise rapidly, which may hinder the smooth operation of the brine treatment unit. Thus, it may not be desirable for the recovery to exceed about 80%. Of course, these figures are examples only and, depending on the particular system, the figures may change.

The brine treatment unit removes contaminants, in particular phosphorus-containing substances, concentrated in the brine so that the brine generated in the recycled water production unit can have a quality of water, for example, for river discharge. Play a role. Thus, the "treated brine" discharged from the brine treatment unit is derived from the primary treated water from which the nitrogen component has been removed and therefore has a very low phosphorus and nitrogen content.

For example, the brine treatment unit may include a flocculation tank for introducing a flocculant for phosphorus-containing material into the brine to agglomerate the phosphorus-containing material in the brine to thereby form a phosphorus-containing substance aggregate in the brine; And a filter tank in which a filter for filtering the phosphorus-containing material aggregate in the concentrated water introduced from the flocculation tank is installed.

In this case, the phosphorus-containing substance aggregate in the concentrated water introduced from the flocculation tank cannot pass through the filter of the filtration tank, and the filtrate passed through the filter has a very low phosphorus content. In addition, other contaminants will also get caught in the filter. And already, the "treated concentrated water" is derived from the primary treated water from which the nitrogen component has been removed, and thus has a very low nitrogen-content. Thus, the water quality of the filtrate (ie, the treated concentrated water) can be significantly improved, for example, up to the water quality that can be discharged to the stream. Phosphorus-containing aggregates and other contaminants trapped in the filter can be removed from the filtration bath together with the filter, for example after the life of the filter has expired. Therefore, it is possible to treat the contaminants of the concentrated water at a very low cost compared to disposing the whole concentrated water by an expensive waste disposal procedure.

Another embodiment of the recycled water production system of the present invention, in order to remove the membrane fouling substances contained in the primary treated water, after further pre-treatment of the primary treated water and supplied to the recycled water production unit It may further comprise an additional pretreatment unit for. Further pretreatment units include, for example, ultraviolet sterilization processes; Advanced oxidation process; Dispersant injection process; Scale inhibitor injection processes; And activated carbon adsorption process; It may include at least one process selected from.

Membrane-contaminating substances are substances that can cause "degradation of filtration due to pore blockage" to the nanomembrane or reverse osmosis membrane of the recycled water production unit supplied with the primary treated water, for example, microbial flocs or piping. Insoluble solids such as solids formed on the inner wall are detached; For example, dissolved organic substances such as undecomposed hardly dissolved dissolved organic substances (eg, humic, fulvic acid, and the like) which are untreated in the process of microbial metabolism or sewage decomposition used as influent sewage water; For example, hardness-inducing substances such as polyvalent cations or dissolved inorganic substances such as silica; Microorganisms that can grow on the surface of the reverse osmosis membrane to form a microbial membrane (slime); And the like. Such membrane fouling substances include ultraviolet sterilization process; Advanced oxidation process; Dispersant injection process; Scale inhibitor injection processes; Activated carbon adsorption process; And microfiltration membrane process; It may be removed by at least one process selected from among. If the additional pretreated primary treated water is supplied to the recycled water production system with the additional pretreatment unit, fouling of the nanomembrane or reverse osmosis membrane can be significantly reduced.

Hereinafter, the concentrated water treatment unit provided by the present invention will be described in more detail. The concentrated water treatment unit of the present invention comprises a flocculation tank for introducing a flocculant for phosphorus-containing material into the concentrated water to agglomerate the phosphorus-containing material in the concentrated water, thereby forming a phosphorus-containing material aggregate in the concentrated water; And a filtration tank provided with a filter for filtering the phosphorus-containing substance aggregate in the concentrated water introduced from the flocculation tank.

The coagulation tank serves to form a phosphorus-containing material aggregate in the concentrated water by injecting a coagulant for phosphorus-containing material into the concentrated water flowing into the coagulation tank to agglomerate the phosphorus-containing material in the concentrated water.

Among the contaminants contained in the concentrated water, one of the most obstacles for the concentrated water to have river water discharge is the phosphorus-containing contaminant which is analyzed as the total phosphorus (TP) component. Such phosphorus-containing contaminants are present in the concentrated water in dissolved, fine droplet, or fine solid particles. It has been conceived in the present invention that when the phosphorus-containing contaminants are aggregated into insoluble salts and converted into coarse particles, the removal of the phosphorus-containing contaminants can be made very efficiently. To this end, in the flocculation tank, a flocculant for phosphorus-containing material is added to the concentrated water flowing into the flocculation tank.

Examples of flocculants for phosphorus-containing materials include inorganic and organic compounds capable of "insolubilizing dissolved phosphorus components" or converting phosphorus-containing substances into aggregates of coarse particles through coagulation or flocculation. Compounds of the class may be used alone or in combination. As a flocculant for phosphorus-containing materials, for example, ferric sulfate, ferric chloride, aluminum sulfate, poly aluminum chloride (PAC), or a combination thereof may be used.

The input of the flocculant for the phosphorus-containing material may be made, for example, by metering the flocculant into the flocculation tank, intermittently or continuously, from the flocculant reservoir in fluid communication with the flocculation bath. In consideration of the ease of injecting the flocculant and the rapid mixing of the flocculant and the concentrated water, it is preferable to inject the flocculant in the form of a liquid obtained by dissolving or dispersing it in a solvent such as water.

The dosage of flocculant for the phosphorus-containing material is based on the removal of the phosphorus-containing material contained in the concentrated water. For example, the dosage of a flocculant for phosphorus-containing substances may be such that the phosphorus-containing substance in the condensate can be aggregated to such an extent that the phosphorus content remaining in the concentrate can satisfy the water quality standards for stream discharge. It can be positive. Such dosage can be readily determined by one skilled in the art, depending on the content of phosphorus-containing material in the concentrated water entering the coagulation bath. For example, the dose of flocculant for phosphorus-containing material is about 0.8 to about 1.6 mg Al for aluminum-based flocculant based on 1 mg total phosphorus (TP) of the concentrated water entering the flocculation tank. In the case of flocculants it may be adjusted to about 2.0 to about 4.0 mg Fe. Accordingly, the total phosphorus (TP) concentration of the flocculated-filtered treated water can be kept low at about 1.0 mg / L or less.

In addition, in the flocculation tank, a flocculating aid may be further added together with the flocculant for the phosphorus-containing material. The flocculent aid is an additive for improving the flocculation efficiency of the flocculant. As the coagulant aid, for example, various coagulant aids of acid, alkali, activated silica, clay, other oil and inorganic series may be used. The amount of the coagulant aid is not particularly limited, and may be appropriately selected by those skilled in the art, depending on the quality of the concentrated water flowing into the coagulation bath and the coagulant used.

Also, in the flocculation tank, aggregation of other contaminants other than the phosphorus-containing material may proceed by the flocculant for the phosphorus-containing material. Aggregates of these other contaminants can also be removed very efficiently from the filtration bath.

The coagulation bath may be in the form of a batch reactor or a continuous reactor. In order to continuously process the concentrated water continuously generated in the recycled water production system, the flocculation tank is preferably in the form of a continuous stirred tank reactor (CSTR).

In the concentrated water treated in the coagulation bath, phosphorus-containing contaminants are present as aggregates in the form of coarse particles. Therefore, the concentrated water treated in the flocculation tank flows into the filtration tank while containing the phosphorus-containing substance aggregate. At this time, the phosphorus-containing material aggregate may have a particle size of about 0.2 to about 100 μm, for example.

The filtration tank serves to filter phosphorus-containing material aggregates in the concentrated water introduced from the flocculation tank using a filter. Phosphorus-containing aggregates do not pass through the filter, so that the filtrate passing through the filter has a very low phosphorus content. In addition, aggregates of other contaminants are also trapped in the filter. Thus, the water quality of the filtrate (ie, the filtered concentrated water) can be significantly improved, for example, up to the water quality that can be discharged to the stream. Phosphorus-containing aggregates and other contaminants trapped in the filter can be removed and disposed of in a fixed amount every cycle from the filtration bath, for example, at a recovery rate of about 90 to about 95%. As such, the concentration of phosphorus-containing aggregates and other contaminants trapped in the filter in the filtration tank can be maintained at an appropriate level. In addition, it is possible to treat the contaminants in the concentrate at a very low cost compared to disposing of the entire brine by an expensive waste disposal procedure.

As the filter, any filter having a pore size that can block the permeation of the phosphorus-containing material aggregate can be used. The pore size of the filter can be, for example, about 0.1 to about 0.4 μm. Typically, given that the particle size of the phosphorus-containing aggregates is from about 0.2 to about 100 μm, the use of a filter having such pore size can substantially block the permeation of the phosphorus-containing aggregates and other contaminant particles. have. As a very preferred example, a microfiltration membrane can be used as the filter. As a more preferable example, a microfiltration membrane grade submerged hollow fiber membrane module may be used as the filter. As the hollow fiber membrane, for example, a polyethylene hollow fiber membrane, a polysulfone hollow fiber membrane, a polyvinylidene fluoride hollow fiber membrane, or a hollow fiber membrane obtained by hydrophilic treatment thereof can be used.

Hereinafter, another aspect of the present invention will be described.

For the same purpose of removing the phosphorus components in the influent sewage, instead of introducing the flocculant for the phosphorus-containing material into the concentrated water treatment unit, the flocculant for the phosphorus-containing material is added to the MBR unit which is a pretreatment unit producing the primary treated water. It is also possible to use a feeding operation. For example, if a problem occurs in the operation of the brine treatment unit, the flocculation agent for phosphorus-containing material is added to the MBR unit as much as the amount of the brine treatment unit is put into the brine treatment unit. It is possible to maintain the phosphorus concentration of the concentrated water generated from the nano-membrane or reverse osmosis membrane unit, which is a recycling water production unit, below the sewage effluent standard.

Based on this aspect of the invention, in the present invention,

A pretreatment unit employing a MBR (membrane bio-reator) for producing primary treated water by removing nitrogen components and organics from the influent sewage; And a reused water production unit employing a nanomembrane or reverse osmosis membrane to separate the primary treated water into recycled and concentrated water.

It provides a method for operating a recycled water production system, characterized in that the flocculant for phosphorus-containing material is added to the pretreatment unit.

In the present invention,

A pretreatment unit employing a MBR (membrane bio-reator) for producing primary treated water by removing nitrogen components and organics from the influent sewage; A recycled water production unit employing a nanomembrane or a reverse osmosis membrane that separates the primary treated water into recycled and concentrated water; In the operating method of the recycled water production system comprising; and a concentrated water treatment unit for removing the phosphorus component of the concentrated water,

It provides a method for operating a recycled water production system, characterized in that further adding a flocculant for phosphorus-containing material to the pretreatment unit.

Since this aspect of the present invention can be easily implemented from the contents related to the recycled water production system of the present invention described in detail above or later, further detailed description is omitted.

Hereinafter, the recycled water production system and the concentrated water treatment unit of the present invention will be described in more detail with reference to FIG. 1. 1 is a process diagram schematically showing one embodiment of the recycled water production system of the present invention. However, the technical scope of the present invention is not limited to the embodiment of FIG. 1.

The MBR unit 1 includes an anaerobic tank 5, an aerobic tank 6, and a separator module 8 immersed in the aerobic tank 6. The sewage (or wastewater) W having passed through the settling basin is introduced into the anoxic tank 5 of the MBR unit 1 after the coarse solids are removed by sieving by a fine screen or the like. The nitrogen-containing matter in the sewage flowing into the aerobic tank 6 due to natural loading is converted into nitric oxide by nitrification under the oxidizing environment of the aerobic tank 6. Part of the sewage that undergoes nitrification in the aerobic tank 6 is conveyed to the anoxic tank 5 via a conveying pump (not shown) and a conveying line 7. Nitrogen oxides in the returned sewage are denitrated with nitrogen gas and removed by the anoxic conditions of the anoxic tank 5 and the substrate of the sewage (W) flowing therein. Thus, the primary treated water W1 drawn out by the suction pump P1 through the membrane module 8 immersed in the aerobic tank 6 has a very low nitrogen concentration.

The primary treated water W1 that has passed through the MBR unit 1 is collected in the primary treated water collection tank 9. The primary treated water collection tank 9 may then serve as a buffer to ensure that the supply of primary treated water to the associated recycled water production unit 3 can be stably maintained. In addition, when the level sensor is installed in the primary treated water collection tank 9 and the supply of primary treated water from the pretreatment unit 1 is insufficient, and the level of the primary treated water collection tank 9 is lowered below a certain level, When the suction filtration operation of the recycle water production unit 3 is stopped and, on the contrary, when the primary treated water collection tank 9 is flooded due to excessive supply of the primary treated water, it is overflowed through the bypass 10. Primary treatment water can also be discharged. Primary treatment water discharged through the bypass 10 can be conveyed to the aerobic tank 6 of the pretreatment unit 1, for example.

The primary treated water collected in the collection tank 9 is supplied to the additional pretreatment unit 2 by the transfer pump P2. In FIG. 1, the UV sterilization process is adopted as the further pretreatment process (2). By the UV sterilization process, bio-fouling due to biofilm formation generated by slime formation by microbial growth on the surface of the nano / reverse osmosis membrane can be reduced. Of course, as described above, according to the analysis results of the water quality of the first raw water (W) and the primary treated water (W1) of the raw water of the nano / reverse osmosis membrane unit 3, it is possible to select and combine a variety of processes.

By using a high pressure feed pump (P3) through the UV sterilization unit (11) and the microfiltration membrane filter (12), which are additional pretreatment processes, recycled water having a higher recovery rate can be produced through the separator. Pressurized to a degree, and supplied to the nano / reverse osmosis membrane unit 13.

From the nano / reverse osmosis membrane unit 14, reused water W3 and concentrated water W4 are discharged. The recycled water production and recycled water recovery rate is related to the flux of the separator and can be controlled by using a flow control valve (not shown) installed at the membrane inlet, the recycled water discharge line, and the concentrated water discharge line.

The concentrated water W4 discharged from the nano / reverse osmosis membrane unit 13 is supplied to the flocculation tank 15 of the concentrated water treatment unit 4. The coagulant (W5) is injected into the coagulant tank (15) from the coagulant injection tank 14 to the liquid phase for rapid reaction with the concentrated water (W5). The concentrated water and the flocculant are sufficiently stirred and mixed in the flocculation tank 15, and then naturally flow down into the filtration tank 16 in which the microfiltration membrane 17 is immersed. Phosphorus-containing aggregates and other solids produced by the aggregation are excluded from the filtration tank 16, and the filtrate W6 is discharged by suction of the discharge pump P5. In this process, since the organic substance and phosphorus component of the concentrated water W4 are removed by agglomeration and filtration, the filtrate W6 can be treated below the effluent water quality standard.

On the other hand, in the reused water production system of Figure 1, the cleaning of the nano / reverse osmosis membrane unit 13 after a long time operation can be made as follows. A portion of the MBR process water W1 or the concentrated water water W6 is stored in the washing tank 18 to prepare a washing liquid W7 by dissolving chemicals such as citric acid and sodium hydroxide. In the cleaning mode of the nano / reverse osmosis membrane (13) module, the normal production water filtration process is stopped, and the washing liquid (W7) stored in the washing tank (18) is introduced into the nano / reverse osmosis membrane module by the transfer pump (P2), and then the production water line The circulating process is discharged to (W3) and the concentrated water line (W4) and flowed back into the cleaning tank 18 is mainly performed. After circulating the cleaning solution for a certain period of time, change the flow path of the concentrated water line to the outside of the system instead of the cleaning tank to completely discharge the cleaning solution, and discharge the cleaning solution in the cleaning tank through the concentrated water line. Shut off W7) and inject the normal MBR process water (W1) to finish the draining of all the cleaning liquid remaining in the pipe. At this time, the transfer pump (P2), the cleaning tank (18) in which the MBR treated water (W1) and the production water (W3) and the nano / reverse osmosis membrane concentrated water treated water (W6) for collecting the nano / reverse osmosis membrane (13) It provides the power to supply the cleaning liquid (W7) to the nano / reverse osmosis membrane (13) from. Through this cleaning process, fouling of the nano / reverse osmosis membrane 13 module can be removed.

<Example>

Under the process conditions shown in Table 1, the recycled water production system of the embodiment of FIG. 1 was operated.

MBR Unit (1) Nano / Reverse Osmosis Membrane Unit (14) Concentrated Water Treatment Units (4) Flow rate (m ³ / day) 50 30 20 Flux (L m ^-2 h ^-1 ) 12.5 13.2 25 HRT (hr) 6.6 (Aerobic: 4.1, Anaerobic: 2.5) - 0.92 (aggregation: 0.46 filtration: 0.46) SRT (day) 50 - - MLSS (mg / l) 5,700-9,270 - - Internal Transfer Rate (Q) 2 ~ 3 - - Aspiration / Pause 10 minutes / 2 minutes continuity - % Recovery - 60 95 Separator Specification material PE (PVDF coating) MPD based polyamide TFC PE Salt excretion - 99.5% (NaCl) - shape Hollow fiber Spiral-wound Hollow fiber Nominal pore size 0.4 μm - 0.4 μm The following flocculant specifications Flocculant - - FeCl ₃ usage - - 1.8 mol-Fe / mol-P

Under the process conditions of Table 1, the results of the water quality analysis of each stream obtained after four months of operation are summarized in Table 2. E. coli was measured 3 times, TBOD5 15 times and other items 30 times. In Table 2, each water quality analysis item is expressed as a minimum value and a maximum value, and the average value is indicated in parentheses.

Water quality item Influent sewage (W) 1st treatment water (W1) Recycle Water (W3) Concentrated Water (W4) Concentrated Filtrate (W6) Water quality standards for sewage treatment facilities Specific area Other Area pH 7.3 to 8.3 (7.8) 6.8 ~ 7.5 (7.1) 6.4 ~ 7.3 (6.8) - 6.4-7.8 (6.8) - - TSS (mg / L) 58.8-131.1 (80.6) 0.1 ~ 0.8 (0.33) Not detected 0.5 ~ 1.8 (1.2) 0.8 ~ 3.3 (1.7) below 10 20 or less TBOD5 (mg / L) 92.6--177.8 (122.6) 1.9 ~ 5.0 (2.9) 0.5-2.1 (1.0) 5.1 ~ 12.8 (7.6) 5.0 ~ 11.5 (7.2) below 10 20 or less TCODcr (mg / L) 158.1--280.6 (191.4) 10.0-22.3 (16.2) 0.4 ~ 2.5 (1.2) 30.9 ~ 49.7 (40.4) 26.1--36.2 (31.7)   40 or less   40 or less TCODmn (mg / L) 56.2--95.5 (71.4) 6.9-15.3 (9.8) 0.2 ~ 0.9 (0.5) 23.5 ~ 36.1 (29.5) 16.7-25.4 (21.1) TN (mg / L) 19.2-33.5 (27.9) 6.5 ~ 15.2 (10.6) 1.0 ~ 3.8 (1.9) 17.1-35.4 (24.3) 16.5-31.7 (23.5) 20 or less 60 or less TP (mg / L) 2.8 ~ 6.5 (4.1) 1.2 ~ 3.3 (2.2) 0 ~ 0.3 (0.05) 3.5-8.1 (5.7) 0.3 ~ 1.2 (0.8) 2 or less 8 or less NH4-N (mg / L) 14.6-26.2 (22.1) 0.1-4.3 (1.1) 0 ~ 0.2 (0.02) 0.2 ~ 11.3 (2.8) 0.1 ~ 10.3 (2.3) - - NO2-N (mg / L) 0 ~ 0.08 (0.02) 0 ~ 0.3 (0.06) Not detected 0 ~ 0.2 (0.03) 0 ~ 0.1 (0.007) - - NO3-N (mg / L) 0.1 ~ 5.0 (1.4) 5.1-11.7 (8.3) 0.5-3.1 (1.7) 10.1-30.6 (19.4) 9.1-29.5 (19.2) - - PO4-P (mg / L) 1.5-2.6 (2.0) 1.1-3.1 (2.0) 0 ~ 0.05 (0.006) 3.3-7.8 (4.8) 0.1 ~ 0.8 (0.4) - - Total coliform group (MPN / 100ml) 22,000 ~ 42,000 (31,000) Not detected Not detected - - 3000 or less 1000 or less

As shown in Table 2, the water quality of the concentrated water filtrate W6 is generally improved compared with the water quality of the concentrated water W4. It is particularly noteworthy that the total phosphorus content (TP) of the concentrated water filtrate (W6) is 0.8 mg / L, which is dramatically reduced compared to the total phosphorus content (TP) of 5.7 mg / L of the concentrated water (W4).

In the case of concentrated water (W4), the total phosphorus content (TP) ranges from 3.5 to 8.1 mg / L, which does not meet specific regional water quality standards (less than 2), as well as general regional water quality standards (8). It also occurs when the following) is not satisfied. Therefore, the concentrated water W4 cannot be discharged to the river as it is.

However, in the case of concentrated water filtrate (W6), it shows a total phosphorus content (TP) in the range of 0.3 to 1.2 mg / L, and these values are in addition to the general regional water quality standards (below 8), as well as specific regional water quality standards ( 2 or less). In addition, the concentrated water filtrate (W6) satisfies the water quality standards for other water quality items. Therefore, the concentrated water filtrate W6 can be discharged to the river as it is.

Thus, by using the recycled water production system of the present invention, it is possible to discharge the concentrated water filtrate (W6) to the stream, and thus, the whole concentrated water (W4) does not have to be disposed of by a costly waste disposal procedure. In this case, the problem of waste water (W4) disposal can be effectively solved.

1 is a process diagram schematically showing one embodiment of the recycled water production system of the present invention.

Claims (9)

A pretreatment unit employing a MBR (membrane bio-reator) for producing primary treated water by removing nitrogen components and organics from the influent sewage; A recycled water production unit employing a nanomembrane or a reverse osmosis membrane that separates the primary treated water into recycled and concentrated water; And A concentrated water treatment unit for removing the phosphorus component of the concentrated water; Recycling water production system comprising a. The method of claim 1, wherein the pretreatment unit is an oxygen-free tank; Aerobic tank; And a separation membrane immersed in an aerobic tank. The system of claim 1 wherein the pretreatment unit further comprises a biological phosphorus-removal process. The apparatus of claim 1, further comprising an additional pretreatment unit for supplying the recycled water production unit after further pretreatment of the primary treated water to remove the membrane fouling substances contained in the primary treated water. Recycling water production system characterized in that. A flocculation tank for introducing a flocculant for phosphorus-containing substances into the concentrated water to agglomerate the phosphorus-containing substances in the concentrated water, thereby forming a phosphorus-containing substance aggregate in the concentrated water; And, A filter tank provided with a filter for filtering phosphorus-containing material aggregates in the concentrated water introduced from the flocculation tank; Concentrated water treatment unit comprising a. 6. The concentrated water treatment according to claim 5, wherein the flocculant for phosphorus-containing material is ferric sulfate, ferric chloride, aluminum sulfate, poly aluminum chloride, or a combination thereof. unit. The concentrated water treatment unit according to claim 5, wherein the filter is a microfiltration membrane grade immersion hollow fiber membrane module. A pretreatment unit employing a MBR (membrane bio-reator) for producing primary treated water by removing nitrogen components and organics from the influent sewage; And a reused water production unit employing a nanomembrane or reverse osmosis membrane to separate the primary treated water into recycled and concentrated water. Operating method for reused water production system, characterized in that the flocculant for phosphorus-containing material is introduced into the pretreatment unit. A pretreatment unit employing a MBR (membrane bio-reator) for producing primary treated water by removing nitrogen components and organics from the influent sewage; A recycled water production unit employing a nanomembrane or a reverse osmosis membrane that separates the primary treated water into recycled and concentrated water; In the operating method of the recycled water production system comprising; and a concentrated water treatment unit for removing the phosphorus component of the concentrated water, Re-use water production system operation method characterized in that the addition of a flocculant for phosphorus-containing material to the pretreatment unit.

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