KR20000039560A - Tertiary treatment of wastewater - Google Patents

Abstract

PURPOSE: A tertiary treatment of wastewater is provided, which is characterized in that raw water is filtered, and organic matters are adsorbed by activated carbon, then ionic matters are treated by osmotic pressure. CONSTITUTION: Organic matters included in wastewater are cohered by using inorganic cohesion agent like alum and polymer cohesion agent. The size of cohered floc and intensity are appropriate, so the amount of remained agent can be reduced. Raw water including surface active agent is difficult to disintegrate biologically, so, activated carbon is used for adsorbing. A filtration device which uses dead-end flow form is provided. The membrane of the filtration device is made of poly acrylo nitrile, and remained organic matters are piled on the membrane. Pressured air is passed through the membrane for scrubbing, so, operating pressure can also be lowered.

Description

Advanced purification of wastewater from factory

The present invention relates to a method for highly purified treatment of wastewater from a steel mill, and more specifically, after the flocculation flotation and multi-layer filtration of the raw wastewater, the organic matter caused by the nonionic surfactant component is removed by using activated carbon adsorption. Then, a high-molecular-weight reverse filtration apparatus removes the organic material and the suspended substance with high molecular weight, and then treats with reverse osmosis membrane to remove the ionic substance, and then the reverse osmosis membrane treated water is reused as manufacturing process water and reverse osmosis membrane concentrated water is again activated carbon adsorption method. By discharging and discharging, it not only has a superior purification performance compared to the conventional treatment method of wastewater from the steel mill, but also does not use the coagulation sedimentation method, thus eliminating the need for a large site for coagulation sedimentation and significantly lowering the investment and operating costs. It is economical and can reuse most of the generated waste water It relates to a method for purifying highly improved canning factory waste water can greatly reduce the pollution of the groundwater or cloth.

Steel cans used in beverage containers are manufactured by a process as shown in the accompanying drawings, in which a steel coil as a raw material is brought in to make a cup by a press, and foreign substances or lubricants on the surface of the cup are removed for printing and internal coating. To this end, degreasing and washing processes are performed, and most of the wastewater is generated in the degreasing and washing process, and the generated wastewater contains water-soluble oils and fine amounts of free oil in the wastewater, and includes biodegradable substances including surfactants. Since it is low, it is treated by a chemical method. As shown in FIG. 1, the raw wastewater for canning is pH 6-8, COD 50-60 ppm, solids (SS) 50-60 ppm, n- Hexane is wastewater with 40-50 ppm.

The general treatment process of the wastewater plant can be as shown in the accompanying drawings, Figure 2, which will be described in more detail for the accompanying drawings.

First, treatment with an oil / water separator to remove free oil from the raw wastewater, and then primary flocculation precipitation treatment by addition of FeCl ₃ , NaOH and anionic polymer flocculant to remove water-soluble oils, suspended solids and organic substances. Then, in order to lower the concentration of organic matter, secondary coagulation sedimentation treatment was performed by adding FeCl ₃ , NaOH, and anionic polymer coagulant together with powdered activated carbon (100 mesh or less), and then to remove residual solids from the coagulation sedimentation treatment water. Filter through a sand filtration device. Then, the activated carbon adsorption column is used to reduce organic matter and discharge the same.

However, the method has a problem that requires a large site for the flocculation sedimentation treatment, and because powdered activated carbon is used, a large amount of inorganic flocculant and polymer flocculant must be added for flocculation, and it is not economical due to high operating cost. There is a problem of increasing the conductivity in the treated water.

In addition, the conventional waste water purification method in the steel can factory can additionally introduce a wastewater recycling method, such wastewater recycling method is treated with a reverse osmosis membrane after the cross-flow microfiltration or ultrafiltration treatment. It is reused in the manufacturing process, and the concentrated water is treated using an oxidation method, and then discharged or concentrated by an evaporator. However, in the case of the cross-flow microfiltration or ultrafiltration treatment, a high operating cost is required according to the operating pressure of the pump, and chemical cleaning is performed to remove contaminants generated in the filtration membrane from the filtration membrane. If necessary, even if the cleaning of the drug, there is a problem that the treated water amount of the membrane is difficult to recover to 100%.

In addition, in the method of treating the concentrated water of the reverse osmosis membrane, when the treatment by the Fenton method is excessively expensive, and when treated with ultraviolet (UV), the operating cost due to power consumption is not economical, Treatment with an evaporator is a method suitable for high concentration wastewater has a very high operating costs.

Therefore, it has excellent purification treatment ability compared to the existing treatment method of wastewater in the steel mill, and also does not use the flocculation sedimentation method, so it does not need a large site for flocculation sedimentation, and it is possible to reduce the investment cost and operation cost significantly. The aim is to provide an improved method for the advanced purification of wastewater from the factory, which can reuse most of the generated wastewater, thus greatly reducing pollution of rivers and groundwater.

1 is a schematic view showing a manufacturing process of the tube,

2 is a schematic view showing a conventional process of treating wastewater from a steel mill,

Figure 3 is a schematic diagram showing the treatment process of the canister factory wastewater according to the present invention.

The present invention relates to a method for purifying a wastewater plant.

a) a process of flocculating flotation of the total raw wastewater generated in the steel mill;

b) filtering the flotation water with a multilayer filtration apparatus and then adsorbing the coal-based activated carbon adsorption apparatus having a particle size of 8 to 30 mesh;

c) filtering the activated carbon adsorption treated water with an ultrafiltration device;

d) filtering the ultrafiltration treated water with a reverse osmosis membrane to separate the reverse osmosis membrane treated water and the reverse osmosis membrane concentrated water; And

e) The reverse osmosis membrane treated water is reused in a manufacturing process, and the reverse osmosis membrane concentrated water is adsorbed by an activated carbon adsorption tower.

With reference to Figure 3 attached to the wastewater purification treatment method according to the present invention will be described in detail for each process as follows.

First, the organic material contained in the general wastewater generated in the steel pipe manufacturing plant is agglomerated by adding 800-1,200ppm of Alum-based inorganic coagulant and 2-3ppm of acrylic acid-based anionic polymer coagulant, and then pressurizing the agglomerated wastewater. Use flotation equipment to handle the injury. In this case, when the alum-based inorganic coagulant and acrylic acid anionic polymer coagulant are used, the cost is low, the size of the flocculated flocs is appropriate and the strength is high, thereby reducing the chemical cost and reducing the residual coagulant, and the conductivity of the wastewater. It can reduce the extent of the rise and also improve the removal efficiency of free oil, which is difficult to treat by the sedimentation method because it is floating on the surface of the waste water by introducing the flotation process, and the required site can be reduced. If the alum-based inorganic coagulant is added below 800 ppm, there is a problem in that the flocculation floc is not well formed. On the other hand, when it is added in excess of 1,200 ppm, the flocculation floc has a small size. Not desirable In addition, when the acrylic acid-based anionic polymer coagulant is added below 2 ppm, the flocculation of the aggregated floc is small, which is not preferable. On the other hand, when it is added in excess of 3 ppm, the polymer coagulant remains and the filtration medium is filtered. This is undesirable because it can clump together.

The flotation treatment water containing the fine floc produced through the flotation treatment is removed using a multilayer filter.

As a next step, the raw waste water contains a surfactant component, which is difficult to decompose chemically and biologically. Therefore, the adsorption treatment is performed using coal-based activated carbon having a particle size of 8 to 30 mesh that easily adsorbs the surfactant component. Therefore, the chemical oxygen demand caused by the surfactant component can be greatly reduced. In this case, when the particle size of the activated carbon is less than 8 mesh, the pore between the activated carbons is wide and the filtration efficiency is not preferable. On the other hand, when the particle size exceeds 30 mesh, the pore size is too small and the filtration flow rate is low. This is undesirable because it requires a decrease and a large backwash flow rate.

Next, as a pretreatment process of reverse osmosis membrane for recycling wastewater, ultrafiltration is performed using a dead-end flow type ultrafiltration apparatus capable of backwashing. The ultrafiltration membrane used in the ultrafiltration apparatus has a pore size of 0.01 μm and uses a hollow fiber form as a material of the elastic polyacrylonitrile (PAN).

The filtration principle of the ultrafiltration device is as follows. Activated carbon adsorption column treated water is passed from the outside of the ultrafiltration membrane to the inside. At this time, the remaining organic material and the suspended material is accumulated outside the ultrafiltration membrane during the filtration process, the flow of the filtered water is a dead-end flow method, all the treated water is filtered. Then, when the limit permeate amount is reached, the operating pressure increases because the suspended substance accumulates on the surface of the ultrafiltration membrane. Therefore, in order to lower the operating pressure and reduce the contamination of the ultrafiltration membrane, the ultrafiltration membrane is backwashed. This backwashing passes the ultrafiltration treated water from the inside of the filtration membrane to the outside, and the contaminants accumulated in the pores of the membrane and the contaminants accumulated on the surface. After removing some of them, scrubbing is performed by introducing compressed air from the outside so that the hollow fiber membranes can be shaken severely from side to side to remove the suspended substances attached to the outside of the filtration membrane, and the washing water used for the filtration membrane is washed from the ultrafiltration membrane. Discharge it. Filtration, backwashing, scrubbing of compressed air, and the repeated discharge of the washing material can reduce the operating pressure of the filtration membrane and reduce the contamination of the filtration membrane.

After the ultrafiltration treatment, the ultrafiltration treated water completely removed from the suspension material is introduced into the reverse osmosis membrane, and the reverse osmosis membrane is stably separated from the reverse osmosis membrane treated water and the reverse osmosis membrane concentrated water by reducing ionic substances and organic substances. The reverse osmosis membrane treated water passed through the reverse osmosis membrane is reused as a manufacturing process water, and the reverse osmosis membrane concentrated water concentrated through the reverse osmosis membrane is discharged after treating with activated carbon adsorption tower, so that only a small amount of the total wastewater is discharged to the outside. .

Although this invention is demonstrated in more detail based on an Example, this invention is not limited by an Example.

Example

Wastewater purification treatment process according to the invention was used, but was carried out with the composition, content and conditions shown in Table 1. In addition, COD _Cr and COD _Mn were measured by a conventional method, and the results are shown in Table 1 below.

Treatment fee basis

1. Alum-based coagulant (C1): 60 won / ㎏ (specific gravity 1.2)

2. FeCl ₃ : 200 won / ㎏ (specific gravity 1.4)

3. Powdered activated carbon: 1500 won / ㎏

4. Granular activated carbon of coal series: 1,500 won / ㎏

Comparative Examples 1 to 4

Attached drawings In the conventional wastewater purification process as shown in Figure 2, but using the same method as the above embodiment.

division Wastewater Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example Furtherance Alum Coagulant (ppm) ¹⁾ - - 1000 1000 1000 1000 FeCl ₃ (ppm) - 1000 - - - - Organic Sorbent (ppm) - 500 500 - - - Anionic polymer coagulant (ppm) ²⁾ - 2 2 2 2 2 Powdered activated carbon (ppm) ³⁾ - - - 500 500 Granular activated carbon adsorption treatment ⁴⁾ pH adjustment - 7 7 7 7 7 test results COD _Cr 152 35 30 34 31 10 COD _Mn 52 16.8 14.2 14.9 14.3 5 COD _Mn removal rate (%) - 67.7 72.7 71.3 72.5 90 Treatment Fee (KRW / ㎥) - 1180 972 1030 822 576 1) Product Name: C1, Company Name: Shinjin Chemicals 2) Product Name: A-601P, Company Name: Yiyang Chemicals3): Product Name: SPC-100, Company Name: Samchully Products4 ): Granular activated carbon adsorption capacity: 0.1 kg of COD removal / 1 kg of activated carbon

In the results of Table 1, when the existing wastewater purification process is used (Comparative Example 3), the wastewater purification process according to the present invention is compared with the treatment cost of 972 won / m 3 and the COD _Mn removal rate of 72.7%. In the case of use (Example), the treatment cost was 576 won / m 3, and the COD _Mn removal rate was 90%, resulting in a much improved result in terms of reduction in treatment cost and COD _Mn removal rate.

Experimental Example: Water quality analysis for each step of the treatment process according to the present invention

By the wastewater purification process according to the present invention, the wastewater (500 tons / day) generated in the steel production plant is highly purified, and the following equation 1 is used to estimate the pollution rate generated by the colloid and particles of the wastewater. The SDI (Silt Density Index) calculated by the above was used to measure the flow rate and flow rate through the flat membrane having 0.45 μm pores of 47 mm diameter under 30 psi pressure.

In Equation 1 above:

TI is the time taken to penetrate 500 ml at the beginning of the experiment,

TF is the time taken to penetrate 500 ml after F minutes,

F is the elapsed time in minutes.

And turbidity was measured by a spectrophotometer, TDS (Total Dissolved Solid) was measured by a TDS meter. In addition, the raw wastewater according to the present invention and the treated water quality of each apparatus are shown in Table 2 below.

division General wastewater Flocculation flotation Multilayer filtration water Activated Carbon Filtration Ultrafiltration Treatment Reverse Osmosis Membrane Treatment Water Reverse osmosis membrane concentrated water → Activated carbon filtration COD _Cr Measured value (ppm) 152 65 60 10 10 5 32 → 18 Removal rate (%) - 57 8 83 - - 43 COD _Mn Measured value (ppm) 52 36 34 3 3 One 10 → 5 Removal rate (%) - 30 7 91 - - 50 Turbidity Measured value (ppm) - 0.53 0.45 0.35 0.30 0.15 2.90 → 2.86 Removal rate (%) - - 15 22 - 50 3 TDS Measured value (ppm) 1,580 1,690 1,690 1,680 1,680 80 4,700 → 4,650 Removal rate (%) - - - - - 95 -

In the results of Table 2, when flocculation flotation treatment of raw water, the oil was removed from 50 ppm to less than 1 ppm, COD _Mn showed 30% removal efficiency, using granular activated carbon to remove organic matter, COD _Mn removal rate was higher than 90% and turbidity removal rate was 22%. In addition, when the ultrafiltration treatment was performed to remove the suspended substances, the SDI of permeated water showed a value of 0.5 or less, which showed good water quality as the inflow of the reverse osmosis membrane. When the concentrated water of the reverse osmosis membrane was treated with activated carbon, COD _Cr was 18ppm, and COD _Mn was 5ppm, indicating that there was little effect on environmental pollution even when discharged to the outside.

Therefore, the confectionery plant wastewater purification method according to the present invention has a much better purification treatment ability than the existing plant-based plant wastewater purification process, and does not use the flocculation sedimentation method. It is economical because it is not necessary, and the investment cost and operation cost can be greatly reduced, and most of the generated wastewater can be reused, which greatly reduces the pollution of rivers and groundwater.

Claims (3)

In the method for purifying the canning plant wastewater, a) a process of flocculating flotation of the total raw wastewater generated in the steel mill; b) filtering the flotation water with a multilayer filtration apparatus and then adsorbing the coal-based activated carbon adsorption apparatus having a particle size of 8 to 30 mesh; c) filtering the activated carbon adsorption treated water with an ultrafiltration device; d) filtering the ultrafiltration treated water with a reverse osmosis membrane to separate the reverse osmosis membrane treated water and the reverse osmosis membrane concentrated water; And and e) reusing the reverse osmosis membrane treated water in a manufacturing process, and discharging the reverse osmosis membrane concentrated water with an activated carbon adsorption tower to discharge the purified water. 2. The method of claim 1, wherein the flocculation flotation treatment comprises adding 800-1,200 ppm of an alum inorganic coagulant and 2-3 ppm of an acrylic acid anionic polymer coagulant. The method of claim 1, wherein the ultrafiltration device is filtered using a dead-end flow method, and the ultrafiltration membrane is made of polyacrylonitrile.