KR101797084B1

KR101797084B1 - Apparatus and Method for treating wastewater containing heavy-metal

Info

Publication number: KR101797084B1
Application number: KR1020160008112A
Authority: KR
Inventors: 김상식; 장일헌
Original assignee: (주)청수
Priority date: 2016-01-22
Filing date: 2016-01-22
Publication date: 2017-11-15
Also published as: KR20170088144A

Abstract

The present invention relates to a heavy metal wastewater treatment apparatus using membrane separation and a wastewater treatment method using the same, and more particularly, to a method and apparatus for treating heavy metal wastewater using membrane separation, The present invention relates to a heavy metal wastewater treatment apparatus using an improved membrane separation and a wastewater treatment method using the same.
A method for treating heavy metal wastewater using membrane separation according to the present invention comprises: a raw water treatment step (S100) for forming heavy metal hydroxides by pretreating raw water containing heavy metals; A membrane separation step (S200) of filtering raw water containing heavy metal hydroxides by using a membrane to separate treated water and raw water concentrated water; And a backwashing step (S250) of removing the precipitate by applying pressure in a direction opposite to the filtration direction in order to remove the precipitate accumulated in the membrane in the membrane separation step.

Description

TECHNICAL FIELD [0001] The present invention relates to a heavy metal wastewater treatment apparatus using membrane separation and a wastewater treatment method using the same,

The present invention relates to a heavy metal wastewater treatment apparatus using membrane separation and a wastewater treatment method using the same, and more particularly, to a method and apparatus for treating heavy metal wastewater using membranes having a gap of 1 to 3 μm without using a polymer coagulant, The present invention relates to a heavy metal wastewater treatment apparatus using an improved membrane separation and a wastewater treatment method using the same.

At present, the total amount of heavy metal-containing wastewater including plating wastewater accounts for about 20 to 25% of the total industrial wastewater.

The industrial wastewater contains various toxic substances such as copper, zinc, chromium, nickel, tin, cyanide, detergent and grease, which causes a lot of environmental problems and difficulties in cost and management due to complicated wastewater treatment methods Suffering.

Korean Unexamined Patent Publication No. 2003-0003347 (Heavy Metal Wastewater Treatment System and its Treatment) discloses a heavy metal wastewater treatment system that treats wastewater containing heavy metals by using flocculant pumped with pyrite and natural ferric chloride, It provides the method.

Thus, treatment of common heavy metal wastewater generally proceeds through coagulation-precipitation processes that produce floc using inorganic coagulants and polymer coagulants and precipitate and remove the resulting fluff.

However, the treatment efficiency of the flocculation-sedimentation process depends on the particle size distribution and the surface charge of the particles (heavy metal hydroxide) produced by flocculation of the heavy metal to be removed with an inorganic flocculant, In addition to inorganic coagulants, high cost polymer coagulant aids are used in large quantities, resulting in high cost of wastewater treatment due to excessive amount of chemicals and sludge generation.

On average, heavy metal hydroxides have a size of 2 to 10 μm, and particles of 10 μm or less are not easy to precipitate. Therefore, the particle size is increased through the use of a large amount of coagulant and an expensive polymer coagulant.

However, in this process, some of the particles are not settled, and many of them exceed the discharge standard. Therefore, in order to control the concentration of heavy metals flowing through the effluent, the filtration process may be installed after the flocculation- The increase of the loss head and backwash period and frequency of backwashing are increasing, and it is urgent to develop an alternative process that can efficiently manage metal wastewater including plating wastewater.

As a result, the separation membrane was used for the treatment of heavy metal-containing wastewater. However, due to the fouling phenomenon (covering the sediment) due to the inorganic coagulant and the polymer coagulant used in the separation membrane process, .

Korean Patent Publication No. 2003-0003347 (Heavy metal wastewater treatment system and its treatment method)

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to provide a method of separating coagulated particles by filtration of coagulated particles with a membrane having an average pore size of 1 to 3 탆, (Membrane filtration rate improvement and low filtration resistance) of the heavy metal hydroxide, and a method for treating wastewater using the same.

According to an aspect of the present invention, there is provided an apparatus for treating heavy metal wastewater using membrane separation, comprising: a raw water processing unit for storing raw water containing heavy metals and performing predetermined pretreatment to form coagulated heavy metal hydroxides; A membrane separation unit for separating the coagulated heavy metal hydroxide in raw water containing heavy metals from the treated water and raw water concentrated water; And reverse details for backwashing by supplying water pressure in the reverse direction of the flow direction of the treatment water to remove sediment accumulated in the membrane during the filtering process.

The raw water treatment unit includes a raw water tank for receiving raw water; A pH adjusting unit for adjusting the pH of the wastewater by injecting a pH adjusting agent into the wastewater in the raw water tank; And a stirring part for mixing the raw water and the pH adjusting agent.

Wherein the membrane separation unit comprises: a hollow cylindrical membrane separation housing for receiving raw water treated in the raw water treatment unit; A membrane formed in the same concentric circle as the membrane separation housing and having an average pore of 1 to 3 m; A process water discharging portion for discharging the process water that has passed through the membrane; And a concentrated water discharging portion for discharging raw water concentrated water that has not passed through the membrane.

And the reverse detail is repeatedly performed at predetermined time intervals.

In addition, the method for treating heavy metal wastewater using membrane separation according to the present invention for solving the above-mentioned problems includes a raw water treatment step (S100) for forming heavy metal hydroxide by pretreating raw water containing heavy metals; A membrane separation step (S200) of filtering raw water containing heavy metal hydroxides by using a membrane to separate treated water and raw water concentrated water; And a backwashing step (S250) of removing the precipitate by applying pressure in a direction opposite to the filtration direction in order to remove the precipitate accumulated in the membrane in the membrane separation step.

The raw water treatment step (S100) is characterized in that the pH is adjusted to 9 to 11 by stirring the raw water after injecting a pH adjusting agent into the raw water. The stirring time is 1 to 30 minutes, and the stirring speed is 30 to 90 rpm.

In the membrane separation step S200, the raw water containing the coagulated heavy metal hydroxide introduced into the membrane separation housing passes through a membrane having a pore size of 1 to 3 탆, the treated water having passed through the membrane is discharged through the treated water discharge portion, And the raw water concentrated water that has not passed through the concentrated water discharging portion is discharged to the concentrated water discharging portion.

As described above, according to the heavy metal wastewater treatment apparatus using membrane separation according to the present invention and the wastewater treatment method using the same, it is possible to prevent the aggregated particles from migrating to a membrane having an average pore size of 1 to 3 μm The filtration does not require the use of an expensive polymer flocculant, which is economical and has an effect of increasing the treatment efficiency of the heavy metal hydroxide (improvement in membrane filtration rate and low filtration resistance).

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the structure of a heavy metal wastewater treatment apparatus using membrane separation according to the present invention. FIG.
2 is a cross-sectional view of a membrane separation unit of a heavy metal wastewater treatment apparatus using membrane separation according to the present invention.
3 is a flow chart showing a method for treating heavy metal wastewater using membrane separation according to the present invention.
4 is a graph showing the neutralization curve and coagulation test results of a single synthetic wastewater according to an embodiment of the present invention.
5 is a graph showing the neutralization curves of (a) composite heavy metal synthetic wastewater containing both Cu, Zn, and Ni and (b) coagulation test results according to an embodiment of the present invention.
FIG. 6 is a graph showing the neutralization curves of coarse wastewater according to an embodiment of the present invention and coagulation test results.
FIG. 7 shows the results of particle size distribution analysis according to the pH and agitation time according to the embodiment of the present invention.
8 is a graph showing the result of the experiment of synthetic wastewater agglomeration according to the agitation condition according to the embodiment of the present invention.
9 is a schematic diagram of a membrane separation experiment method according to an embodiment of the present invention.
10 shows the filtration time of each wastewater by pH according to an embodiment of the present invention.
11 is a graph showing an initial permeation rate according to an embodiment of the present invention.
12 shows the particle size distribution of each wastewater according to an embodiment of the present invention.
FIG. 13 shows the film permeation rate when the backwash according to the embodiment of the present invention is not performed.
14 shows the membrane permeation rate in case of backwash according to the embodiment of the present invention.
15 is a transmission flux according to an embodiment of the present invention.
16 is a Recovery according to an embodiment of the present invention.
17 is a result of the concentration test according to the embodiment of the present invention.

Specific features and advantages of the present invention will be described in detail below with reference to the accompanying drawings. The detailed description of the functions and configurations of the present invention will be omitted if it is determined that the gist of the present invention may be unnecessarily blurred.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the structure of a heavy metal wastewater treatment apparatus using membrane separation according to the present invention. FIG.

The apparatus for treating heavy metal wastewater using membrane separation according to the present invention comprises a raw water treatment unit 100 for storing raw water containing heavy metals and performing predetermined pretreatment to form coagulated heavy metal hydroxides and a raw water treatment unit 100 for filtering the cohesive heavy metal hydroxides in raw water containing heavy metals And a membrane separation unit 200 for separating the treated water and raw water concentrated water.

More specifically, the raw water treatment unit 100 includes a raw water tank 110 for storing raw water, a pH adjusting unit 120 for adjusting the pH of the wastewater by injecting a pH adjusting agent into the wastewater in the raw water tank, a stirrer 130 for mixing the pH adjusting agent, a temperature sensor for measuring the temperature of the raw water contained in the raw water tank, and a chiller 140 for preventing the temperature from being maintained and rising.

The pH controller 120 includes a pH meter and a pH adjusting agent storage tank. The pH controller 120 measures the pH of the raw water mixed in the raw water tank 110 and the raw water mixed with the pH adjusting agent, and adjusts the pH The control agent can be controlled.

The pH adjusting agent is not limited as long as it is an alkaline substance, for example, sodium hydroxide (NaOH) may be used.

The stirrer 130 mixes raw water with a pH adjuster and forms a cohesive heavy metal hydroxide.

Heavy metal hydroxides are formed in the raw water treatment unit 100, and the raw water containing heavy metal hydroxides is transferred to the membrane separation unit 200 to filter the heavy metal hydroxides contained in the raw water in the membrane separation unit. At this time, the raw water treatment unit 100 and the membrane separation unit 200 are connected by a pipe and are moved by the pressure of the circulation pump.

Although not specifically described below, it is preferable to control the movement and flow of raw water and treated water including a flow meter, a pump, and a valve in a pipe connecting each component (raw water treatment section, membrane separation section, etc.).

FIG. 2 is a cross-sectional view of a membrane separation unit according to the present invention, wherein the membrane separation unit 200 includes a hollow cylindrical membrane separation housing 210 for receiving raw water treated in a raw water treatment unit, A process water discharging portion 230 for discharging the process water that has passed through the membrane, and a raw water concentrated water which has not passed through the membrane, And a concentrated water discharging portion 240 for discharging the concentrated water.

When the raw water flows into one side of the membrane separation housing 210, the raw water introduced by the predetermined pressure passes through the membrane having a pore size of 1 to 3 탆, the heavy metal hydroxide contained in the raw water is filtered and the heavy metal hydroxide is filtered (Hereinafter abbreviated as treated water) flows into the inside of the membrane.

The average particle size of the heavy metal hydroxide is 2 to 10 占 퐉, and the average pore size of the membrane is preferably 1 to 3 占 퐉 in order to prevent the membrane filtration rate and the high filtration resistance while maintaining the high removal rate of the heavy metal hydroxide.

At this time, the treated water having passed through the membrane is moved along the treated water discharging part 230, and the raw water (hereinafter abbreviated as raw water concentrated water) in which the heavy metal hydroxide which has not passed through the membrane is concentrated is discharged through the concentrated water discharging part 240 .

The raw water concentrated water discharged through the concentrated water discharging unit 240 moves to the dewatering unit 400 to remove moisture from the raw water concentrated water.

Also, the raw water concentrated water discharged through the concentrated water discharging unit 240 may be transferred to the raw water tank 110 for reprocessing.

It will be appreciated that the membrane separation unit 200 can be additionally provided in a plurality of units in consideration of the wastewater throughput and the like.

A fouling phenomenon (a phenomenon that the membrane is covered with the precipitate) occurs along with the passage of time, and since the precipitate lowers the membrane separation ability, a means for releasing it is needed.

The apparatus for treating heavy metal wastewater using membrane separation according to the present invention includes a reverse detail 300 for supplying backward pressure to the reverse direction of the flow direction of the treatment water to remove sediment accumulated in the membrane during the filtering process, The backwash by detail is repeated at predetermined time intervals for stability and continuity of the process.

The reverse detail may supply hydraulic pressure and air pressure, and when the hydraulic pressure is supplied, the reverse detail may include a backwash tank and a storage tank.

The wastewater treatment apparatus further includes a data log for storing data (flow rate, pressure, etc.) of the system, and a controller and a PLC panel capable of automatically and manually controlling the operation mode (filtration, concentration, cleaning, etc.) .

3 is a flow chart showing a method for treating heavy metal wastewater using membrane separation according to the present invention.

The method for treating heavy metal wastewater using membrane separation according to the present invention comprises a raw water treatment step (S100) of pretreating raw water containing heavy metals to form heavy metal hydroxides, and a step of filtering raw water containing heavy metal hydroxides using a membrane, And a membrane separation step (S200) for separating raw water concentrated water.

The raw water treatment step (S100) is characterized in that the pH is adjusted to 9 to 11 by adding a pH adjusting agent to the raw water and then stirring, wherein the stirring time is 1 to 30 minutes and the stirring speed is 30 to 90 rpm .

More specifically, a pH adjuster is injected and stirred into the raw water contained in the raw water tank, so that the heavy metal material contained in the raw water is agglomerated into heavy metal hydroxide.

In order to form heavy metal hydroxides, pH, stirring time and speed should be controlled. The pH is preferably 9 to 11, the stirring time is 1 to 30 minutes, and the stirring speed is 30 to 90 rpm.

The pH measurement and injection are controlled by the pH control unit, and the raw water tank contains a stirrer for mixing the raw water and the pH adjusting agent.

At this time, a temperature sensor and a chiller for measuring the temperature for controlling the temperature and preventing the raw water mixed with the raw water and the pH adjusting agent are further included to control the temperature.

On the other hand, the raw water concentrated water discharged through the concentrated water discharging portion is subjected to a dehydration step (S400) in which water is removed from the raw water concentrated water by moving to the dehydrating part.

In addition, the raw water concentrated water discharged through the concentrated water discharging portion may be passed through a conveying step (S300) in which it is conveyed to the raw water processing section and reprocessed.

A fouling phenomenon (a phenomenon that the membrane is covered with the precipitate) occurs along with the passage of time, and since the precipitate lowers the membrane separation capability, a step for releasing it is required.

The method of treating wastewater according to the present invention includes a backwashing step (S250) of removing the precipitate by applying pressure in a direction opposite to the filtration direction in order to remove precipitate accumulated in the membrane in the membrane separation step (S200).

In addition, the backwashing step S250 is repeatedly performed at a predetermined time interval for the stability and continuity of the process.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Establishment of raw water treatment conditions

_{CuSO 4 · 5H 2 O (Daejung} , Korea), ZnSO 4 · 7H 2 O (Duksan, Korea), NiSO 4 · a high concentration by using a _{6H 2 O Cu (128 mg /} L), Ni (173 mg / L) , And Zn (78 mg / L) were prepared and used in the experiment.

The coagulation experiments were carried out in the following order after securing the neutralization curves for the test subjects in order to keep the injection time of NaOH beforehand. The synthetic wastewater and the actual wastewater were preliminarily adjusted to pH 8, 9, 10, 11 by injecting a pre-calculated amount of NaOH, followed by one minute of stirring at 90 rpm and 30 minutes of stirring at 50 rpm to induce hydroxide formation Respectively. The supernatant was then obtained by filtration using Whatman 5 filter papers (2.5 μm). When required to keep the heavy metal samples were avoid degeneration by injecting _{0.2 mL HNO 3/1 L filtrate} or wastewater. Separate coagulants other than the pH control were not used except for the experiment of injecting FeCl ₃ .6H ₂ O (Duksan, Korea) into the copper synthetic wastewater at 3.9, 7.8, and 11.8 g Fe ³ ⁺ / L to investigate the coagulant loading effect.

The concentrations of heavy metals such as Cu, Zn, Ni and Pb were measured by ICP-OES (OPTIMA 7300DV, PerkinElmer, USA). The concentrations of TCOD, SCOD, TSS, VSS, method was analyzed. The particle size distributions were analyzed by particle size distribution analyzer (PRO-7000S, SeishinKigyo, Japan) after sedimentation. Jar tester was used for uniform stirring and pH meter (Orion star A211, Thermo scientific, USA) was used for pH calibration.

4 is a graph showing a neutralization curve and an aggregation test result of a single synthetic wastewater, wherein (a) is a Cu synthetic wastewater neutralization curve, (b) is a Zn synthetic wastewater neutralization curve, (E) Heavy metal removal efficiency is shown when coagulant is injected into Cu.

When pH was adjusted with 1N NaOH, it was easy to achieve pH 10 with only a small amount of NaOH injection, and a large amount of NaOH injection was required to achieve pH 11.

As a result, it was possible to achieve heavy metal removal efficiency of more than 90% by adjusting the pH without injecting the flocculant (see (d)).

The effect of coagulant (FeCl ₃ _{) on} the formation of heavy metal hydroxides was confirmed (as shown in (e)). As a result, the coagulant did not play a major role in the formation of heavy metal hydroxides.

Fig. 5 shows (a) neutralization curves of the composite heavy metal synthetic wastewater containing both Cu, Zn, and Ni and (b) coagulation test results.

It is considered that the removal rate of composite heavy metal synthetic wastewater is somewhat increased compared with that of single heavy metal synthetic wastewater because sweep precipitation occurs in the composite heavy metal synthetic wastewater during coagulation - precipitation process and promotes mutual precipitation.

Compared with the removal experiment, it can be seen that the pH showing the optimum efficiency for each heavy metal slightly varies. In the case of Ni, pH 10, Cu, Zn showed the highest removal efficiency at pH 9. At pH 9 and 10, the removal efficiencies of the three heavy metals were more than 99%, and all of the allowable standards for wastewater discharge from clean area (less than 1 mg / L of Cu, less than 1 mg / L of Zn, less than 0.1 mg / L of Ni) .

Based on the above experimental results, experiments were conducted on actual heavy metal waste water generation business wastewater (L electronic wastewater, A battery wastewater), and the characteristics are shown in Table 1.

FIG. 6 shows the neutralization curves of the actual wastewater and the coagulation test results, wherein (a) is the neutralization curve of the L electronic wastewater, (b) is the neutralization curve of the A battery wastewater, (d) shows the results of the flocculation test of the A battery wastewater.

Unlike the synthetic wastewater, in the case of the actual wastewater, the amount of NaOH required to control the pH was somewhat higher than that of the synthetic wastewater due to oil and inorganic substances coexisting in the actual wastewater.

L eutectic wastewater, it was found that all of the heavy metals could be satisfactorily met in the clean zone wastewater discharge standard only by alkali control and filtration without additional oil or inorganic flocculant at pH 9 or higher. And the optimum removal efficiency is shown. The removal efficiencies of Cu, Zn, Ni and Pb were 99.71%, 99.75%, 99.15% and 99.98%, respectively.

As a result of agglomeration experiment on battery wastewater, it was found that all of the criteria for the discharge of clean wastewater to Cu, Zn, and Ni were satisfied at pH 8 and the discharge standard was satisfied even at pH 11 at pH 11. The removal efficiencies of Cu, Zn, Ni and Pb were 92.74%, 93.98%, 87.83% and 99.7%, respectively.

FIG. 7 is a graph showing particle size distribution according to pH and agitation time. FIG. 7 (a) is a graph of particle size distribution according to pH of L electronic wastewater, and FIG. 7 (b) is a graph of particle size distribution according to agitation time of L electronic wastewater.

(a) In the graph of particle size distribution according to pH, it was confirmed that 99.9% of the particles were 2 탆 or more. This shows that the pore size of the large-diameter membrane is suitable for the complete separation of heavy metal hydroxides formed through pH control.

(b) In the graph of particle size distribution according to agitation time, it was confirmed that the particles were 2 탆 or more in all cases. This is a result indicating that even if stirring time is 1 minute, it is sufficient for formation of heavy metal hydroxide.

8 shows the results of the synthetic wastewater agglomeration experiment according to the agitation condition.

(a) shows the results of agglomeration experiments of mixed synthetic heavy metal wastewater with agitation time, and the removal efficiencies were measured at 30, 20, 10, and 1 minute agitation at pH 10, respectively. As a result, effluent discharge standards were satisfied at 1 min for Ni, Pb, 10 min for Zn, and 30 min for Cu.

(b) to (e) show the agitation speed (30, 50, 70, 90 rpm) and agitation time (5, 10, 20, 30 min) The results of the coagulation test are shown.

As a result, heavy metals removal efficiency was the best at 70 rpm and 20 min. Also, it was confirmed that the removal efficiency was higher than the condition of 10 min for 20 min condition for all the items. It is considered that the agitation time may be an important variable in the heavy metal agglomeration experiment.

Based on the above results, the experiment was performed by dividing the agitation time (3, 5, 7, 10, 15, 20, 25, 30 min) at pH 10 and 70 rpm.

(f) shows the above results, and it was found that the Cu standard 3, 5, 15 and 20 min satisfied the emission limit, and the removal efficiency was low at 7, 10, 25 and 30 min. All other heavy metals met the emission limits in all items, but showed similar trends in removal efficiency. As a result of the above experiment, it was found that the heavy metal flocculation time has a high influence on the removal efficiency.

Membrane separation Establishment of conditions

The membrane separator and the membrane separation module were made of PP material having a length of 1 m, an outer diameter of 0.85 mm, an inner diameter of 0.55 mm and an average pore size of 2 탆.

L electron wastewater, A battery wastewater and H wastewater wastewater. The water quality of each raw water is shown in Table 2.

Prior to the filtration test for each wastewater, tap water was used to measure the initial permeation rate of the membrane by operating pressure. 20 liters of wastewater with adjusted pH was loaded into the raw water tank and the time required for filtration was measured by operating the membrane device. Regeneration test was carried out by immersing the used membranes in acidic solution of pH 2 for 20 minutes and then rinsing with distilled water. The filtration rate was measured by re-filtration in the same manner. Membrane filtration experiment method Are shown in Table 3 and FIG.

In order to investigate membrane permeation rate with backwash, membrane permeation rate was measured without backwash. The permeation rate of membranes measured before and after washing was compared with that of membrane after washing for 10 minutes with NaOH solution pH controlled permeate solution. The order of the backwash process is '300 seconds (5 minutes) filtration → backwashing with permeated water for 4 seconds → air backwash for 2 seconds'.

In addition, the permeation rate was measured while discharging (enriching) the permeated water to the outside of the system. The operating conditions for performing all of the above experiments are shown in Table 4.

10 shows the filtration time of each wastewater by pH, (a) shows the results of the L company electronic wastewater, and (b) shows the results of the A company battery wastewater.

L electronic wastewater was pH 10, and A company battery wastewater had the shortest filtration time at pH 11, which is in agreement with the optimum condition of coagulation of each wastewater previously measured (Fig. 7).

FIG. 11 shows the initial permeate flow rate. The initial permeate flow rate was measured at an operating pressure of 0.05 MPa to 0.3 MPa at an interval of 0.05 MPa. As the operating pressure increased, the flow rate increased from 0.469 L / min (0.05 MPa) to 1.509 L / min (0.3 MPa).

The operating pressure was determined to be 0.2 MPa in consideration of the decrease in membrane permeation flow rate during actual wastewater operation. The reference flow rate for the actual wastewater was set to the reference flow rate of 850 L / m ² / hr. The membrane area of the membrane of the present invention is about 0.22 L / min in terms of 0.0155 m ² .

Fig. 12 shows the particle size distribution of each wastewater, in which (a) is the L-type electronic wastewater, (b) is the H-plating wastewater, and (c) At this time, each wastewater was adjusted to pH 10 or higher by using NaOH, and the particle size distribution was measured.

In the case of L wastewater, particles of 0.1 to 1.83 μm were 13.8% and particles of 2.97 μm or more were 86.2%. In case of Company A, particles of 0.1 to 1.83 μm were 43.61%, particles of 2.97 μm or more were 56.39 %. In case of Company A, the distribution of particles smaller than 2 μm, which is the average pore size of the separation membrane, is large, so that the flow rate due to pore clogging during membrane filtration is expected to decrease. In case H, particle size of 0.1 ~ 1.83 μm was 1.7% and particle size over 2.97 μm was 98.32%. In particular, particle size distribution over 10 μm was 90.36%.

Fig. 13 shows the results of the membrane permeation rate without backwash, (a), (b), and (c) e) is the permeate flow rate comparison.

(a) In the case of L wastewater, the initial permeate flow rate was 0.5948 L / min, but it decreased continuously with the elapse of filtration time, and decreased by 62% at 0.2268 L / min after 60 minutes of filtration. The reason for this is that since L was not backwashed, the ratio of particles having a diameter of 2 μm or less in the case of L company is about 15%, and the flow rate is decreased by fouling phenomenon such as fine particles in the inflow water occluding the membrane pore .

(b) In case A, the initial permeate flow rate was 0.2875 L / min. The permeate flow rate after 60 minutes of membrane filtration time was 0.1703 L / min, which showed a decrease of 40.9% compared to the initial permeate flow rate. Compared with the case of L company, the degree of decrease in flow rate was 62% and 40.9% respectively, and the decrease in width of L company was larger than that of L company. The initial permeate flow rate was 0.5948 L / min and 0.2875 L / Because the initial flow rate is as low as 48% of the L company.

(c) The initial permeate flow rate of H Company was larger than that of L Company A, and the initial permeate flow rate was 0.8568 L / min, 1.4 times and 3 times larger than that of L Company A . The permeate flux after 60 minutes of membrane filtration was 0.5946 L / min, which was 30.6% less than the initial permeate flux.

(d) - (e) show the permeate flow rate according to the ratio of the particle size distribution of 2 μm or less. Particles smaller than 2 μm in size smaller than the pore size of the membrane occlude the pores of the membrane from the beginning of operation of the membrane, This result also shows that the initial permeate flux is lower as the ratio of particles below 2 μm is higher.

14 shows the membrane permeation rate in the case of backwashing, wherein (a) shows the results of the L-type electronic wastewater, (b) shows the A-company battery wastewater, and (c) shows the results of the H-plating wastewater.

(a) Change in membrane permeation flux when backwashing of L wastewater was carried out and without backwashing. The initial permeate flow rate was 0.5948 L / min, and 0.2268 L / min. However, the initial permeate flow rate was 0.5991 L / min for backwash and 0.3691 L / min for 60 minutes after filtration, and the flow rate reduction rate was 38%. The permeate flux at the time of 60 minutes was 1.6 times higher than that of the case where the backwash was not performed, and the flow rate reduction rate was also remarkably reduced. Also, the membrane permeation flow rate was significantly higher than that of 0.22 L / min determined by the reference flow rate.

(b) In case of Company A, the decrease of the permeate flow rate is significantly reduced compared to the case of backwashing as in case of L. In the case of no backwash, the initial permeate flow rate is 0.2875 L / min, The initial permeate flow rate was 0.2881 L / min for backwash and 0.2284 L / min for 60 minutes after filtration, and the flow rate reduction rate was 20.7%.

(c) In case of Company H, the decline in the permeate flow rate was significantly reduced compared to the case where backwashing was carried out as in the case of Company L and Company A. When the backwash was not performed, the initial permeate flow rate was 0.8568 L / min and the filtrate was decreased by 30.6% at 0.5946 L / min after 60 minutes of filtration. However, when the backwash was performed, the initial permeate flow rate was 0.8984 L / The flow rate reduction rate was 16.1% at 0.7534 L / min.

15 shows the results of permeate fluxes (a), (B), (A), and (C), respectively.

(a) when L 's membrane permeation flux is the initial permeable membrane flux was 2319.1 L / m ² · hr, membrane permeation flux after 60 minutes is 850, the reference flux is set to appear as 1428.8 L / m ² · hr, the target value L / m < ² >. hr.

(b) showed lower permeation flux than that of (L) and (H) in case of company A, and it is considered that the permeation flux is low as a whole because of high distribution of sodium particles such as sodium sulfate. The initial permeation flux was 1115.3 L / m ² · hr, and the permeation flux after 60 minutes was 884.0 L / m ² · hr. The permeation flux of about 1.04 times the reference flux of 850 L / m ² · hr set as the target value Permeate flux.

(c) In the case of H Company, the permeation flux of the initial permeate was 3477.7 L / m ² · hr, and the permeation flux after 60 minutes was 2916.4 L / m ² · hr. m ² · hr, which is about 3.4 times higher.

FIG. 16 shows the results of recovery as (a), (B), (A), and (C), respectively.

(a) The permeation flux before membrane washing of L company was 0.5991 L / min and 0.3691 L / min, respectively, at the initial and 60 minutes elapse, and the membrane permeability after washing with the washing water adjusted to pH 12 with NaOH for 20 minutes The flow rates were 0.5957 L / min and 0.3418 L / min, respectively. The recovery by membrane washing was 95.9% based on the total permeation amount for 60 minutes, which was 15.9% higher than the target value of 80%.

(b) The permeate flow rate before membrane cleaning of A showed 0.2881 L / min and 0.2284 L / min, respectively, at the initial and 60 minutes elapse, and the membrane permeability after washing with the washing water adjusted to pH 12 with NaOH for 20 minutes The flow rates were 0.2867 L / min and 0.2204 L / min, respectively. The recovery by membrane washing was 100.1% based on the total permeation amount for 60 minutes, and the membrane cleaning effect by alkaline solution was very large, and the target value of 80% was achieved sufficiently.

(c) The permeation flux before membrane washing of H company was 0.8984 L / min and 0.7534 L / min at the initial and 60 minutes, respectively. The membrane was washed with a washing water adjusted to pH 12 with NaOH for 20 minutes The permeate flow rate was 0.8808 L / min and 0.7338 L / min, respectively. The recovery by membrane washing was 99.4% based on the total permeation rate for 60 minutes, and the target value of 80% was achieved sufficiently. Respectively.

Fig. 17 shows the results of the concentration test, in which (a) shows the results of the L company electronic wastewater, (b) shows the results of the A company battery wastewater, and (c) shows the results of the H company plating wastewater.

(a) For L wastewater, raw water of 133 mg / LSS adjusted to pH 10 at the initial stage of filtration was concentrated about twice as much as 286 mg / LSS. The membrane permeation flow rate decreased as the concentration progressed. The permeate flow rate at 0.3805 L / min (membrane permeation flow rate) at the initial stage of filtration was lowered to 0.2893 L / min when the concentration was doubled, and the permeate flow rate reduction rate was about 24.0% And the target flow rate (reference flow rate) exceeded 0.22 L / min.

(b) In the case of wastewater A, the SS concentration was higher than that of L and H by sodium sulfate particles. The raw water of 1,155 mg / LSS adjusted to pH 10 at the initial stage of filtration was concentrated twice as much as 2,410 mg / LSS . The membrane permeation flux decreased as the concentration proceeded. The permeate flux at 0.2364 L / min (membrane permeation flux at the beginning of filtration) decreased to 0.2139 L / min when the concentration was doubled, and the permeate flux reduction rate was 9.5% . The target flow rate (reference flow rate) was 0.22 L / min or less.

(c) In the case of H wastewater, the raw water of 403 mg / LSS adjusted to pH 10 at the initial stage of filtration was concentrated about twice as much as 832 mg / LSS. As in the case of L and Company A, membrane permeation flow rate decreased as the concentration progressed. The permeate flow rate at 0.6992 L / min (membrane permeation flow rate) at the initial stage of filtration decreased to 0.6509 L / min when the concentration was doubled, The flow rate reduction rate was 6.9%. And the membrane permeation flow rate exceeding the target flow rate (reference flow rate) of 0.22 L / min more than three times.

Table 5 shows the analysis results of treated water quality.

heavy metal enemy Treated water Removal rate
Company L
Zn 0.061 0.081 - Ni N.D. 0.034 - Cu 57.337 0.145 99.75
Company A
Zn 3.646 0.047 98.71 Ni 0.368 0.021 94.29 Cu 0.029 0.078 -
Company H
Zn 55.053 0.020 99.96 Ni 38.539 0.072 99.81 Cu 22.871 0.736 96.78

In case of L company, the main discharge heavy metal is Cu, and Zn and Ni contained in the raw water are below 0.1 mg / L. The removal efficiency of Cu was 99.75% and the concentration in treated water was 0.145 mg / L. In case of membrane filtration of A company's waste water, the removal efficiencies were 98.71% for Zn and 94.29% for Ni, and the concentrations of treated water were 0.047 mg / L and 0.021 mg / L and 0.1 mg / L or less. The removal efficiencies of Zn were 99.96% for plating wastewater of H Company, and 99.81% and 96.78% for Ni and copper, respectively. The treatment efficiencies were 0.020, 0.072, and 0.736 mg / L. In the case of Company H, the concentration of Cu was relatively high as 0.736 mg / L, whereas the concentration of Zn and Ni in treated water showed good quality of less than 0.1 mg / L, but the coagulant (Alum or iron salt, etc.) As a result of the experiment, it is considered that it will be improved by injecting a small amount of coagulant depending on the case.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken as limiting the scope of the present invention. The present invention can be variously modified or modified. The scope of the invention should, therefore, be construed in light of the claims set forth to cover many of such variations.

100:
110: raw water tank
120: raw water pH adjusting section
130: stirrer
140: Chiller
200: membrane separator
210: membrane separator housing
220: Membrane
230: process water discharging portion
240: concentrated water discharging portion
300: Station Detail
400: dehydrating part

Claims

A wastewater treatment apparatus for treating wastewater containing heavy metals,
A raw water treatment unit for storing raw water containing heavy metals and performing predetermined pretreatment to form coagulated heavy metal hydroxides;
A membrane separation unit for separating the coagulated heavy metal hydroxide in raw water containing heavy metals from the treated water and raw water concentrated water;
And reverse details for backwashing by supplying water pressure in the reverse direction of the flow direction of the treatment water to remove sediment accumulated in the membrane during the filtering process,
The raw water processing unit
The mixture is stirred at a pH of 9 to 11, stirred for 1 to 30 minutes, stirred at a rate of 30 to 90 rpm,
The membrane separation unit
A hollow cylindrical membrane separation housing for receiving raw water treated in the raw water treatment section;
A membrane formed in the same concentric circle as the membrane separation housing and having an average pore of 1 to 3 m;
A process water discharging portion for discharging the process water that has passed through the membrane;
And a concentrated water discharging portion for discharging raw water concentrated water that has not passed through the membrane,
Wherein the raw water concentrated water is transported to the raw water treatment unit for reprocessing or moved to the dehydrating part to remove moisture from the raw water concentrated water
An apparatus for treating heavy metal wastewater using membrane separation.

The method according to claim 1,
The raw water processing unit
A raw water tank for storing raw water;
A pH adjuster for adjusting the pH of the wastewater by injecting a pH adjusting agent into the wastewater in the raw water tank;
And a stirring part for mixing the raw water and the pH adjusting agent
An apparatus for treating heavy metal wastewater using membrane separation.

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The method according to claim 1,
The reverse detail
And repeatedly performed at a predetermined time interval.
An apparatus for treating heavy metal wastewater using membrane separation.

1. A wastewater treatment method for treating wastewater containing heavy metals,
A raw water treatment step (S100) of pretreating raw water containing heavy metals to form heavy metal hydroxides;
A membrane separation step (S200) of filtering raw water containing heavy metal hydroxides by using a membrane to separate treated water and raw water concentrated water;
And a backwashing step (S250) for removing the precipitate by applying pressure in a direction opposite to the filtration direction to remove the deposit accumulated on the membrane in the membrane separation step,
The raw water treatment step (SlOO)
The mixture is stirred at a pH of 9 to 11, stirred for 1 to 30 minutes, stirred at a rate of 30 to 90 rpm,
The membrane separation step (S200)
The raw water containing the coagulated heavy metal hydroxide introduced into the membrane separation housing passes through the membrane having a gap of 1 to 3 탆 and the treated water having passed through the membrane is discharged through the treated water discharge portion and the raw water concentrated water which has not passed through the membrane Is discharged to the concentrated water discharging portion,
Wherein the raw water concentrated water is conveyed to a raw water treatment unit for reprocessing and a dehydrating step for moving to a dehydrating unit and removing water from the raw water concentrated water
(METHOD FOR TREATING HEAVY METAL Wastewater Using Membrane Separation).

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