KR20200070888A - Method for pretreatment of capacitive deionization based on ingredient of raw water - Google Patents

Abstract

The present invention relates to a method for pre-treating a capacitive deionization process according to an ingredient of raw water, in which when a capacitive deionization process is applied to discharged water of a sewage/waste water treatment facility, activation of an electrode in the capacitive deionization process can be optimized by selectively applying a coagulation process, a filtering process, and a desorption process as a pre-treatment process of the capacitive deionization process according to an ingredient of the discharged water of a sewage/waste water treatment facility, that is, the gradient of the raw water. The method for pre-treating a capacitive deionization process according to an ingredient of raw water according to the present invention is a pre-treatment process for raw water introduced into a capacitive deionization apparatus, and the ingredient of the raw water is classified into less than TDS 200 ppm, TDS 200 to 700 ppm, and TDS 701 to 4000 ppm, a membrane filtering (MF) process is applied as the pre-treatment process if the ingredient of the raw water is less than TDS 200 ppm, a coagulation process, a filtering process, and an adsorption process are sequentially applied as the pre-treatment process or a ceramic separation membrane process, a filtering process, and an adsorption process are sequentially applied as the pre-treatment process if the ingredient of the raw water is TDS 701 to 4000 ppm, and only an adsorption process is applied as the pre-treatment process or a filtering process and an adsorption process are sequentially applied as the pre-treatment process if if the ingredient of the raw water is TDS 200 to 700 ppm.

Description

Method for pretreatment of capacitive deionization based on ingredient of raw water

The present invention relates to a pretreatment method of a capacitive desalination process according to the properties of raw water, and more specifically, in applying a capacitive desalination process to effluents of a sewage treatment plant, according to the properties of the effluents of a sewage treatment plant, that is, the properties of raw water. It relates to a pretreatment method of a capacitive desalination process according to the properties of raw water capable of optimizing electrode activity in a capacitive desalination process by selectively applying a coagulation, filtration and adsorption process as a pretreatment process of the capacitive desalination process.

Discharged water treated in environmental basic facilities such as wastewater treatment plants is a very stable alternative water resource in terms of water quality and quantity. The clean treated effluent can serve as a dilution water for contaminated rivers in the upstream during the dry season, can be used as high-quality industrial water, or can be supplied as an ecological flow to urban streams that have been urbanized.

Recently, the water quality of the effluent has been further improved by applying a capacitive desalination process to the effluent from the wastewater treatment plant. However, the properties of the effluent vary depending on the pollutant entering the wastewater treatment plant, and when the wastewater treatment plant and the capacitive desalination process are combined, the properties of the effluent also affect the capacitive desalination process. If the turbidity and the total organic carbon (TOC) are too high in the properties of the effluent, that is, the raw water flowing into the capacitive desalination process, it acts as a factor inhibiting the electrode activity in the capacitive desalination process.

Korea Patent Publication No. 2013-61366

The present invention has been devised to solve the above problems, and when applying the capacitive desalination process to the effluent of a wastewater treatment plant, condensing, filtering, and adsorbing processes according to the properties of the effluent of the wastewater treatment plant, that is, raw water. An object of the present invention is to provide a pretreatment method of a capacitive desalination process according to the properties of raw water, which can optimize electrode activity in a capacitive desalination process by selectively applying it as a pretreatment process of a desalination process.

In order to achieve the above object, the pre-treatment method of the electricity storage desalination process according to the properties of the raw water according to the present invention is a pre-treatment process for raw water flowing into the electricity storage desalination device, wherein the properties of the raw water are less than TDS 200ppm, TDS 200-700ppm , TDS 701 ~ 4000ppm, if the property of raw water is less than TDS 200ppm, membrane filtration process (MF) is applied as a pretreatment process, and if the property of raw water is TDS 701~4000ppm, it is a coagulation process, filtration process, adsorption process as pretreatment process Is applied sequentially or ceramic separation membrane process, filtration process, adsorption process are applied sequentially, and if the property of raw water is TDS 200~700ppm, only adsorption process is applied as pretreatment process or filtration process and adsorption process are applied sequentially. do.

If the raw water has a TDS of 200 to 700 ppm, the turbidity is 0.5 to 1.5, and if the total organic carbon (TOC) is 1 to 12, only the adsorption process is applied as a pretreatment process, the turbidity is 1.5 to 8, and the total organic carbon ( If TOC) is 12 to 30, filtration and adsorption are sequentially applied as pretreatment.

Raw water with a TDS of less than 200 ppm has a membrane contamination index (SDI) of less than 2, raw water with a TDS of 200 to 700 ppm has a membrane pollution index (SDI) of 2 to 5, and a raw water with a TDS of more than 700 ppm has a membrane contamination index (SDI). Exceeds 5

Raw water with a TDS of less than 200 ppm has a turbidity of less than 0.5 NTU, total organic carbon (TOC) is less than 2 ppm, and raw water with a TDS of more than 700 ppm has a turbidity of more than 10 NTU and total organic carbon (TOC) exceeds 30 ppm.

The filtration process and the adsorption process may be carried out independently by providing a filtration tank and an adsorption tank, respectively, or by filling both the filtration carrier and the adsorption carrier in one reaction tank so that both the filtration process and the adsorption process are performed.

The filter carrier may be activated filter media (AFM), or granular activated carbon (GAC) as an adsorbent carrier.

The pretreatment method of the capacitive desalination process according to the properties of raw water according to the present invention has the following effects.

Turbidity and total organic carbon (TOC) concentration of the raw water can be minimized by differently applying a pretreatment process according to the nature of the raw water flowing into the electricity storage desalination process, thereby improving the desalination efficiency of the electricity storage desalination process.

1 is a reference diagram for explaining a pre-treatment method of a capacitive desalination process according to the properties of raw water according to an embodiment of the present invention.
2A and 2B are experimental results showing the turbidity and TOC removal efficiency using small-capacity filtration and adsorption columns.
3A and 3B are experimental results showing turbidity and TOC removal efficiency using large-capacity filtration columns and adsorption columns.
4A and 4B are experimental results showing turbidity and TOC removal efficiency in a device in which filtration columns and adsorption columns are sequentially arranged.

Turbidity and total organic carbon (TOC) are factors that have an important effect on the activity of the electrode during the electrolytic desalination process, which is a process of removing salts contained in the raw water by electrolysis of raw water. When the turbidity and total organic carbon (TOC) of the raw water are high, the electrode deactivation is inhibited by inhibiting the electrode activity in the capacitive desalination process. Therefore, in order to improve the desalination efficiency of the capacitive desalination process, the turbidity of the raw water and the total organic carbon (TOC) must be managed at appropriate values.

Turbidity and total organic carbon (TOC) of raw water is a property of raw water having an important effect on desalination efficiency of a capacitive desalination process, and the present invention applies a selective pretreatment process in relation to turbidity and total organic carbon (TOC) of raw water Although it is suggested that turbidity and total organic carbon (TOC) are small in size, process suitability may be poor to classify and apply the pretreatment process of the present invention based on turbidity and total organic carbon (TOC).

Accordingly, the present invention applies TDS (total dissolved solids) as a criterion for distinguishing the properties of raw water in applying the selective pretreatment process of the capacitive desalination process. That is, the properties of the raw water are classified based on the values of the TDS, and an optional pretreatment process is applied to the raw water of each property.

The pretreatment process of the present invention, which is selectively applied according to the properties of raw water, is basically based on a coagulation process, a filtration process, and an adsorption process. If the raw water has a TDS of 200 to 700ppm, both the filtration process and the adsorption process are applied or only the adsorption process is applied. If the TDS of the raw water is less than 200ppm, both the filtration process and the adsorption process are omitted, and the membrane filtration process (MF) pretreatment process Can replace In addition, when the raw water has a TDS of 701 to 4000 ppm, a pretreatment process may be configured by adding a coagulation process or a ceramic separation membrane process before proceeding with a filtration process and an adsorption process.

The present invention aims to control the turbidity and total organic carbon (TOC) of the raw water flowing into the capacitive desalination process to a turbidity of 0.5 NTU or less and a total organic carbon (TOC) of 4 ppm or less through the pretreatment process.

The TDS value of raw water for applying the optional pretreatment process is classified as less than 200 ppm of TDS, 200 to 700 ppm of TDS, and 701 to 4000 ppm of TDS, depending on the characteristics of the raw water according to the pollutant. As a result of experiments, TDS is less than 200ppm, and TDS is 200~700ppm for cooling water discharged from various facilities, and 701~4000ppm for industrial complex wastewater. Is showing the TDS level.

Thus, in the case of effluent treatment plants with a TDS of less than 200 ppm, the membrane filtration process (MF) is applied by a pre-treatment process and then treated by a capacitive desalination process. In the case of a cooling water with a TDS of 200 to 700 ppm, both the filtration process and the adsorption process are pretreated. Applying or applying only the adsorption process, in the case of industrial complex wastewater with TDS of 701~4000ppm, after the filtration process and the adsorption process, a pre-treatment process in which a coagulation process or a ceramic separation membrane process is additionally applied, followed by a capacitive desalination process.

On the other hand, among the factors that determine the properties of raw water, the membrane contamination index (SDI, Silt Density Index), turbidity, and total organic carbon (TOC) show a similar tendency to TDS (Total Dissolved Solids). Specifically, raw water having a TDS of less than 200 ppm has a membrane contamination index (SDI) of less than 2, raw water having a TDS of 200 to 700 ppm has a membrane pollution index (SDI) of 2 to 5, and a raw water having a TDS exceeding 700 ppm has a membrane contamination index. (SDI) tends to exceed 5. In addition, the tendency of turbidity and total organic carbon (TOC) is also consistent with the tendency of membrane contamination index (SDI) and TDS. Raw water with TDS less than 200ppm has a turbidity of less than 0.5NTU, total organic carbon (TOC) is less than 2ppm, and raw water with TDS exceeding 700ppm tends to have a turbidity greater than 10NTU and total organic carbon (TOC) more than 30ppm. . When the raw water of TDS 200 to 700 ppm, that is, the membrane contamination index (SDI) is 2 to 5, it is subdivided into two types. This is to apply the pretreatment process more effectively. TDS 200~700ppm, that is, if the membrane pollution index (SDI) is 2~5, turbidity is 0.5~1.5, total organic carbon (TOC) is 1-12, turbidity is 1.5-8, and total organic carbon (TOC) is 12 It can be divided into cases of ∼30. In the former case, the turbidity is 0.5 to 1.5 and the total organic carbon (TOC) is 1 to 12, only the adsorption process is applied. In the latter case, the turbidity is 1.5 to 8 and the total organic carbon (TOC) is 12. In the case of ∼30, the filtration process and the adsorption process are applied together.

As described above, the pretreatment process according to the present invention is based on a coagulation process, a filtration process, and an adsorption process. The agglomeration process, the filtration process, and the adsorption process are in principle applied sequentially, and the coagulation process, the filtration process, and the adsorption Either process can be omitted because the process is applied sequentially. In addition, as mentioned above, raw water having a TDS of less than 200 ppm is subjected to a membrane filtration process (MF), and raw water with a TDS of 701 to 4000 ppm is subjected to an agglomeration process (or ceramic separation membrane process), a filtration process, and an adsorption process sequentially. For raw water of TDS 200~700ppm, turbidity is 0.5~1.5, total organic carbon (TOC) 1~12 is applied only adsorption process, turbidity is 1.5~8, total organic carbon (TOC) 12~30 is filtration process The adsorption process is applied sequentially.

The filtration process and the adsorption process can be carried out independently by providing a filtration tank and an adsorption tank, respectively, or by filling both the filtration carrier and the adsorption carrier in one reaction tank so that both the filtration process and the adsorption process can proceed. Here, in one embodiment, AFM (activated filter media) may be used as the filter carrier, and granular activated carbon (GAC) may be used as the adsorbent carrier.

In the above, the pretreatment method of the capacitive desalination process according to the properties of raw water according to an embodiment of the present invention has been described. Hereinafter, the present invention will be described in more detail through experiments.

<Experimental Example 1: The nature of the enemy>

The properties of the effluent from the sewage treatment plant, the first industrial wastewater, the second industrial wastewater, and the cooling water were analyzed, and the results are shown in Table 1 below.

<The image of the enemy>
sewer
Effluent The first
Industrial wastewater 2nd
Industrial wastewater cooling water
January February April August October TOC
(ppm) 20.07 82.41 114 10.49 11.14 12.46 10.42 3.26 Turbidity
(NTU) 1.33 26.65 35.10 1.75 2.18 23.46 7.07 7.39 Cond.
(uS/cm) 11.33 4450 5510 1240 1080 1063.5 760.25 734 pH 7.83 8.93 7.84 6.89 7.64 7.93 8.15 7.67 Fe
(ppm) - - - - 0.05 0.165 0.075 0.0525 Si
(ppm) 6.70 7.10 - 7.6 9.95 12.95 22.57 31.2 Al
(ppm) - - - - 0.003 0.0063 0.1132 0.094 TN
(ppm) 9.00 10.00 20.00 9 - - 5.3 - TP
(ppm) - - - - - - 5.175 - TDS
(ppm) 7.25 2848.00 3526.40 849.4 723.6 712.545 509.3675 491.78

<Experimental Example 2: Performance evaluation of carrier>

Granular activated carbon (GAC), ceramic separator, AFM, and miracle sand were prepared as a filter carrier or an adsorbent carrier, and the TOC and turbidity removal performance of each carrier was evaluated.

GAC, AFM, and MS were respectively charged to a column having a diameter of 3 cm and a height of 12 cm, and effluent of TDS 700 ppm or less was supplied to each column at a rate of 5 ml/min, and the TOC and turbidity changes in each column were measured. In addition, a ceramic separation membrane made of alumina material having a pore size of 0.1 µm was prepared, and after a TDS of 700 ppm or less of effluent was supplied at a rate of 5 ml/min, TOC and turbidity changes in each column were measured.

Referring to Figure 2a, the total organic carbon (TOC) showed the highest efficiency in the column filled with granular activated carbon (GAC) (TOC removal efficiency: GAC> ceramic separator> MS> AFM), Figure 2b for turbidity As shown in, the ceramic separator showed the best performance (ceramic separator> AFM> MS> GAC).

Then, the performance of GAC and AFM was evaluated by increasing the size of the column. After filling a column of 30 cm in diameter and 50 cm in height with about 23100 g of AFM and about 10400 g of GAC, after supplying effluent of TDS 700 ppm or less at a rate of 30 ml/min, the TOC change was measured and the AFM was measured in a column filled with GAC. The turbidity change was measured in the filled column.

Referring to FIG. 3A, in the case of total organic carbon (TOC), a tendency to increase after 100 minutes of filtration time was confirmed, but it was confirmed that a target value (4 ppm) was achieved. The turbidity tends to increase gradually while remaining below the target value (0.5 NTU) during the initial 200 minutes.

In the next experiment, the column filled with AFM and the column filled with GAC were sequentially placed, and the effluent under TDS 700 ppm was passed through both columns sequentially, and then the TOC and turbidity changes were measured. 4A and 4B, it can be confirmed that the TOC is kept constant compared to the GAC-only column.

Claims (6)

As a pre-treatment process for raw water flowing into the electricity storage desalination device,
The properties of raw water are divided into TDS less than 200ppm, TDS 200-700ppm, and TDS 701-4000ppm.
If the property of raw water is less than TDS 200ppm, the membrane filtration process (MF) is applied as a pre-treatment process, and when the property of raw water is TDS 701~4000ppm, a coagulation process, a filtration process, an adsorption process are sequentially applied, or a ceramic separation membrane process. Filtration process and adsorption process are applied sequentially,
If the property of the raw water is TDS 200~700ppm, the pretreatment method of the power storage type desalination process according to the property of the raw water, characterized in that only the adsorption process is applied as the pretreatment process or the filtration process and the adsorption process are sequentially applied.
According to claim 1, When the property of the raw water is TDS 200 ~ 700ppm,
If the turbidity is 0.5 to 1.5 and the total organic carbon (TOC) is 1 to 12, only the adsorption process is applied as a pretreatment process.
If turbidity is 1.5 to 8, and the total organic carbon (TOC) is 12 to 30, the pre-treatment method of the electricity storage type desalination process according to the properties of the raw water, characterized in that the filtration process and the adsorption process are sequentially applied as a pretreatment process.
The raw water of claim 1, wherein the raw water having a TDS of less than 200 ppm has a membrane fouling index (SDI) of less than 2, the raw water of a TDS 200 to 700 ppm has a membrane fouling index (SDI) of 2 to 5, and the raw water having a TDS exceeding 700 ppm is Pre-treatment method of the capacitive desalination process according to the nature of the raw water, characterized in that the membrane contamination index (SDI) exceeds 5.
The method of claim 1, wherein the raw water having a TDS of less than 200 ppm has a turbidity of less than 0.5 NTU, a total organic carbon (TOC) of less than 2 ppm, and a raw water having a TDS of more than 700 ppm has a turbidity of more than 10 NTU and a total organic carbon (TOC) of 30 ppm. Pretreatment method of the capacitive desalination process according to the properties of the raw water, characterized in that it exceeds.
The method of claim 1, wherein the filtration process and the adsorption process are carried out independently by providing a filtration tank and an adsorption tank, respectively, or both a filtration process and an adsorption process are performed by filling both a filtration carrier and an adsorption carrier in one reaction tank. Pre-treatment method of the capacitive desalination process according to the properties of the raw water, characterized in that it can be.
The method of claim 1, wherein the filtration carrier is AFM (activated filter media), and the adsorption carrier is granular activated carbon (GAC).

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