KR20000032313A - Treatment method of dyeing wastewater using reverse osmosis and evaporation - Google Patents

Abstract

PURPOSE: A treatment method of dyeing waste water is provided, which is characterized in that waste water is treated by reverse osmotic system, and evaporated to purify the water CONSTITUTION: Wastewater is passed through an adsorption tower which uses activated carbon as a pretreatment. Small suspended solids are removed using a micro filter in shape of cartridge. The membrane which the size of the hole is 0.2 micrometer maintains silt density index(SDI) less than 4.5. When substances which causing scales, like calcium, magnesium, and sulfate ion, are contained in the water, ion components are concentrated. So, scales are formed on the membrane module. The method removes inorganic ions within the range which scales are not generated, and remained substances are treated by evaporating so that sludge cake is formed and discharged.

Description

Dyeing Wastewater Treatment Using Reverse Osmosis and Evaporation

The present invention relates to a dyeing wastewater treatment method using a membrane and an evaporator. More specifically, the wastewater discharged from the dyeing wastewater treatment plant is treated with a reverse osmosis system and an evaporator to obtain treated water at a high recovery rate, and to process the wastewater into industrial water. It is about a method to be reused.

In general, dyeing companies use a lot of water for cooling water, process water, washing water, etc., and wastewater that has been used is discharged within the discharge limit by using physical, chemical and biological treatment methods in wastewater treatment plants. However, such a wastewater treatment method has a water quality in which the treated water cannot be used again as process water, thereby realizing only the purpose of wastewater treatment. Therefore, in order to reuse the wastewater as process water, the wastewater must be treated with the same or more water quality than the industrial water. In general, in the dyeing wastewater, unlike the domestic sewage, the content of inorganic ions that hinder the reuse as industrial water is high, and the existing wastewater treatment method cannot reuse the treated water as process water.

On the other hand, techniques for removing ionic components in water are known as reverse osmosis, electrodialysis, electrophoresis, evaporation. Reverse osmosis is a technique of removing inorganic ions in water using reverse osmosis. Osmotic phenomenon refers to a phenomenon in which a solvent of low concentration moves to a solution of high concentration with a semipermeable membrane interposed therebetween. In this case, when a pressure of more than osmotic pressure is applied to a solution of high concentration, a solvent of high concentration moves to a solution of low concentration. It is called reverse osmosis phenomenon.

There are relatively many examples of reverse osmosis membrane systems used for wastewater treatment. Representative examples thereof include "Method of treating seasonal wastewater by reverse osmosis membrane method (Korean Patent Publication No. 95-8371)", "Method and apparatus for treating wastewater of plating wastewater by hybrid system of reverse osmosis pressure and ferrite method" (Korean Patent Publication No. 95-17747), "Method and Apparatus for Treatment of Radioactive Washing Waste Using Combined Process of Reverse Osmosis Membrane and Ultrafiltration Membrane (Korean Patent Publication No. 93-20489)", No Discharge-Recycling Technology of Wastewater by Chemical Precipitation-Precision and Nanofiltration 95-11344).

However, when dyeing wastewater is highly concentrated to increase the recovery rate (percentage of treated water to original wastewater) by applying reverse osmosis method containing high concentration of inorganic ions, the inorganic ions in the wastewater are precipitated as inorganic salts and scaled in the reverse osmosis membrane module. There is a limit to the recovery rate at which the permeate can be obtained by the reverse osmosis system alone, since the formation of the sigma lowers the efficiency of the membrane. In addition, certain concentrations of substances may exceed emission limits as they are concentrated.

In order to solve the above problems, the present inventors have repeatedly studied and experimented and proposed the present invention based on the results. The present invention reprocesses the concentrated water generated in the reverse osmosis system by using an evaporator, Distilled water is reused to increase the recovery rate of the entire system as well as to provide a method that can treat the waste water (free) by treating the evaporation residue (cake), the purpose is.

1 is a process chart showing a process of treating the discharged water discharged from the dyeing wastewater treatment plant according to the method of the present invention

Figure 2 is a graph showing the electrical conductivity of the influent and permeated water by date in the reverse osmosis system

3 is a graph showing the electrical conductivity of the influent and permeated water by date in the evaporator

In order to achieve the above object, the present invention provides a method for treating wastewater, in which a large diameter material is removed from the wastewater, and then an activated carbon adsorption column is used to remove and remove the organic components of the wastewater, and the fine filtration membrane is used to A pretreatment step of removing fine suspended matter; Removing the inorganic ions from the wastewater by introducing the wastewater having undergone the pretreatment into a reverse osmosis system; And recovering distilled water by using an evaporator for the concentrated water excluded from the reverse osmosis system and discharging the evaporated residues to the outside of the system. The method relates to a dye wastewater treatment method using reverse osmosis and evaporation.

Hereinafter, the present invention will be described in detail.

In the present invention, after removing a large diameter material in the wastewater, the organic component of the wastewater is adsorbed and removed using an activated carbon adsorption tower, and a pretreatment is performed to remove fine suspended matter in the wastewater using a microfilter.

Particles and organic materials of large diameter contained in the dyeing wastewater can be removed by applying conventional methods such as sand or activated carbon adsorption tower. For example, the large diameter material is removed using sand, and the organic matter is adsorbed and removed using an activated carbon adsorption tower. The sand is usually used having an effective diameter of 0.35-0.5mm.

The fine suspended solids are removed using a micro filter, and as the micro filter, a micro filter in the form of a cartridge generally used may be used, and a backwashable precision filtration membrane capable of backwashing using air and water is preferably used. It is good to do it. In the case of the backwashable microfiltration membrane, the pore size may be selected and applied in the range of about 0.01-1 μm. For example, by using a fine filtration membrane having a pore of 0.2 μm, the SDI (Silt Density Index) value of the pretreated water is maintained at 4.5 or less (SDI value 5 or less of the spiral reverse osmosis membrane module).

In addition, in the present invention, the wastewater that passed through the pretreatment step is introduced into the reverse osmosis system to remove the inorganic ions in the wastewater.

Generally, the reverse osmosis system is divided into permeate and excluded concentrated water through the membrane due to its separation characteristics, especially when the content of scale-causing substances (Ca ⁺² , Mg ⁺² , SO ₄ ^-2 ) is high in raw wastewater. The ionic components are concentrated as much as the concentration multiple according to the recovery rate to form scale in the membrane module, which is a factor that drastically lowers the separation efficiency. Therefore, the removal of the inorganic ions using the reverse osmosis system is limited to the ratio that can be recovered according to the concentration of inorganic ions in the raw waste water. In addition, certain constituents in concentrated water may be concentrated to exceed emission limits. An example of this is as follows. That is, the discharge limit of A component is 10ppm, but if there is 5ppm in the raw wastewater, it is not a problem to discharge it as it is. However, when the wastewater is recycled at a 75% recovery rate using a reverse osmosis system, the water quality of the treated water is excellent, but the concentration of A component in the concentrated water is 4 times concentrated to about 20 ppm. In this case, the brine will exceed the emission limit.

Therefore, the present inventors recover only to the extent that scale does not occur with the reverse osmosis system, and the rest is treated by using an evaporator to recover and reuse 98% or more of the treated water as a whole.

In the present invention, the concentrated water excluded from the reverse osmosis system using the evaporator to recover the distilled water and discharge the evaporated residues to the outside of the system.

In general, membrane concentrate water is a water quality in which the inorganic ions are almost saturated, so using an evaporator is the most efficient method. However, as the evaporation proceeds in the evaporator, the inorganic ions exceed the solubility to form scale. This scale forms scales on the tubes or walls in the evaporator, which lowers thermal efficiency and causes corrosion of the device.

Such scale generation in the evaporator can suppress the scale generated on the tube or wall surface by injecting nucleation material such as CaSO ₄ separately from the outside.

The evaporator may be a conventional one, for example, manufactured by SAKAKURA, Japan. The evaporator adopts a method in which a heat source is supplied while steam passes through a plurality of horizontally arranged tubes in the reactor, and waste water is evaporated under reduced pressure as it falls from top to bottom. The evaporated distilled water is cooled through a heat exchanger and recovered and reused as treated water. Some of the evaporated residue is discharged out of the system, and most of the remainder is circulated and mixed with the replenishing water to be introduced into the evaporator. In this case, it is preferable to separately inject scale generating nuclei such as CaSO ₄ to solve scale generation in the reactor, which is the most difficult problem in the evaporator operation.

Important factors in the operation of the evaporator may be the evaporation temperature and pressure, which should be appropriately selected according to the properties of the evaporator or the target wastewater used, but in terms of energy efficiency, the evaporation temperature is set at 50 to 70 ° C. It is preferable to reduce the pressure to -500 to 700 mmHg.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

The effluent discharged from the wastewater treatment plant was treated in the same process as FIG. 1, which will be described in detail as follows.

The wastewater is treated with a pre-treatment (1) consisting of a sand filter, an activated carbon adsorption tower, and a precision filtration membrane with a pore diameter of 0.2 μm to meet the SDI 5 or less, which is the inflow condition of the reverse osmosis module. Supplied. The reverse osmosis system was a film product (FILMTEC) (BW30-2540) of the United States, in which four modules were configured in series.

The reverse osmosis system inflow was maintained at 15 l / min and the permeate was operated at 3 l / min. At this time, the operating pressure was 15-25kg / cm 2. 2 l / min of 12 l / min of concentrated water was discharged out of the system and the rest was purified again and fed into the reverse osmosis module together with supplemental water.

Therefore, the recovery rate of the reverse osmosis system was 60%. The concentrated water discharged from the reverse osmosis system is fed to the evaporator (3), which uses steam as a heat source, and the pressure in the reactor is -600 mmHg under reduced pressure and the temperature is about 60 ° C. The amount of inflow was 0.80 l / min, the amount of evaporated water was 0.75 l / min and the recovery was about 95%. Thus, the recovery of the entire system of the apparatus used in this example was 98%.

The water quality change of the wastewater operated under the above conditions was measured and the results are shown in Table 1 below.

Wastewater Pretreatment Reverse osmosis evaporator Permeate Concentrated water Distilled water Residue SS (mg / l) 7.5 0.8 0.1 2.0 0.1 350 Chromaticity (degrees) 68.1 29.1 0 71.4 0 1303 COD (mg / l) 35.9 17.3 1.7 43.8 4.5 822 Ca (mg / l) 150.0 1.32 270 2.41 3155 Cl (mg / l) 189.4 7.35 425.8 0.43 8970 Conductivity (μs / cm) 3975.0 85.2 7820 32.1 88700

As can be seen in Table 1, the suspended solids (Suspended solid) of the raw waste water was 7.5mg / l, the suspended solids of the wastewater passed through the pretreatment device was 0.8mg / l. In addition, it was found that the chromaticity and COD (chemical oxygen demand) component was also reduced during the pretreatment. The conductivity of the reverse osmosis system influent was 3975 μs / cm, and the permeate was 85.2 μs / cm with 98.5% rejection. This is better than general water quality and is sufficient for reuse as industrial water.

The electrical conductivity of the reverse osmosis system concentrated water flowing into the evaporator was 7820 μs / cm. The rejection rate of the evaporator was 99.6% and distilled water was also of sufficient water quality for industrial use.

Example 2

In the reverse osmosis system in the wastewater treatment as in Example 1, the electrical conductivity of the influent water and the electrical conductivity of the treated water were obtained by date, and the results are shown in FIG. 2.

As can be seen in Figure 2, when treating the dyeing waste water according to the present invention shows that the water quality of the treated water passing through the reverse osmosis system is sufficient to be reused as industrial water.

In addition, in the evaporator during the same wastewater treatment as in Example 1, the electrical conductivity of the influent water and the electrical conductivity of the treated water were obtained for each day, and the results are shown in FIG. 3.

As can be seen in Figure 3, when treating the dyeing waste water according to the present invention shows that the water quality of the treated water passing through the evaporator is also sufficient to be reused as industrial water.

As described above, according to the present invention, not only can 98% or more of the dyeing waste water be recovered and reused as process water, but also its water quality is much better than that of general industrial water. In addition, less than 2% of the evaporation residues can be achieved after the cake process and landfill ultimately to achieve wastewater free discharge technology.

Claims (2)

In the method of treating the dye wastewater, Removing a large diameter material from the wastewater, and then pretreating the organic components of the wastewater using the activated carbon adsorption tower, and removing the fine suspended solids from the wastewater using the microfiltration membrane; Removing the inorganic ions from the wastewater by introducing the wastewater having undergone the pretreatment into a reverse osmosis system; And Recovering the distilled water using the evaporator for the concentrated water excluded from the reverse osmosis system and discharging the evaporated residues out of the system; dyeing wastewater treatment method using a reverse osmosis method and evaporation method comprising a The method of claim 1, The recovery of the distilled water using the evaporator is performed by reducing the evaporation temperature to 50 to 70 ° C. and reducing the pressure to -500 to 700 mmHg.