KR102197621B1 - Method for pretreatment of capacitive deionization based on ingredient of raw water - Google Patents

Abstract

In the present invention, in applying the capacitive desalination process to the effluent of a wastewater treatment plant, the condensation, filtration, and adsorption processes are selectively applied as the pretreatment process of the capacitive desalination process according to the properties of the effluent of the wastewater treatment plant, that is, the properties of the raw water. It relates to a pretreatment method of a capacitive desalination process according to the properties of raw water that can optimize electrode activity in a food desalination process.The pretreatment method of the capacitive desalination process according to the properties of raw water according to the present invention is provided in a capacitive desalination device. As a pretreatment process for the incoming raw water, the properties of the raw water are classified into less than 200ppm TDS, 200~700ppm TDS, and 701~4000ppm TDS.If the properties of the raw water are less than 200ppm TDS, a membrane filtration process (MF) is applied as a pretreatment process. If the nature of the raw water is TDS 701~4000ppm, the coagulation process, the filtration process, and the adsorption process are sequentially applied as the pretreatment process, or the ceramic separation membrane process, the filtration process, and the adsorption process are sequentially applied, and if the property of the raw water is TDS 200~700ppm It is characterized in that only the adsorption process is applied as the pretreatment process or the filtration process and the adsorption process are sequentially applied.

Description

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

The present invention relates to a pretreatment method of a storage type desalination process according to the nature of raw water, and more particularly, in applying the storage type desalination process to the effluent of a wastewater treatment plant, the properties of the effluent from a wastewater treatment plant, that is, according to the properties of the raw water. The present invention 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 coagulation, filtration, and adsorption processes as a pretreatment process of a capacitive desalination process.

The effluent treated at basic environmental facilities such as a sewage treatment plant is a very stable alternative water resource in terms of water quality and quantity. Cleanly treated effluent can serve as dilution water for contaminated rivers upstream during the dry season, can be used as high-quality industrial water, and can be supplied as ecological flow to urban rivers that have been dried up by urbanization.

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

Korean Patent Publication No. 2013-61366

The present invention was conceived to solve the above problems, and in applying a storage-type desalination process to the effluent of a wastewater treatment plant, the condensation, filtration, and adsorption processes are stored according to the properties of the effluent of the wastewater treatment plant, that is, the properties of the raw water. An object thereof is to provide a pretreatment method for a capacitive desalination process according to the properties of raw water that can optimize electrode activity in a capacitive desalination process by selectively applying it as a pretreatment process for a food desalination process.

The pretreatment method of the capacitive desalination process according to the characteristics of the raw water according to the present invention to achieve the above object is a pretreatment process for raw water flowing into the capacitive desalination device, and the properties of the raw water are less than 200 ppm TDS and 200 ~ 700 ppm TDS. , TDS 701~4000ppm.If the property of raw water is less than 200ppm of TDS, the membrane filtration process (MF) is applied as the pretreatment process, and if the property of the raw water is TDS 701~4000ppm, the coagulation process, filtration process, adsorption process are used as the pretreatment process. Is applied sequentially or a ceramic separation membrane process, a filtration process, and an adsorption process are sequentially applied.If the property of the raw water is TDS 200-700 ppm, only the adsorption process is applied as the pretreatment process, or the filtration process and the adsorption process are sequentially applied. do.

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

Raw water with TDS less than 200ppm has a membrane pollution index (SDI) less than 2, raw water with TDS 200~700ppm has a membrane pollution index (SDI) of 2-5, and raw water with TDS exceeding 700ppm has a membrane fouling index (SDI) Exceeds 5.

Raw water with a TDS of less than 200 ppm has a turbidity of less than 0.5 NTU and a total organic carbon (TOC) of less than 2 ppm, and a raw water with a TDS of more than 700 ppm has a turbidity of more than 10 NTU and a total organic carbon (TOC) of more than 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 a filter carrier and an adsorption carrier in one reaction tank, one filtration process and an adsorption process may both proceed.

The filter carrier may be AFM (activated filter media), and the adsorption carrier may be granular activated carbon (GAC).

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

The turbidity and total organic carbon (TOC) concentration of raw water can be minimized by applying a different pretreatment process according to the nature of the raw water flowing into the capacitive desalination process, thereby improving the desalination efficiency of the capacitive desalination process.

1 is a reference diagram for explaining a pretreatment 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 turbidity and TOC removal efficiency using a small-capacity filtration column and adsorption column.
3A and 3B are experimental results showing turbidity and TOC removal efficiency using a large-capacity filtration column and adsorption column.
4A and 4B are experimental results showing turbidity and TOC removal efficiency in a device in which a filtration column and an adsorption column are sequentially arranged.

In the capacitive desalination process, which is a process of removing salts contained in raw water by electrolyzing raw water, factors that have an important influence on the activity of electrodes are turbidity and total organic carbon (TOC). If the turbidity of raw water and the total organic carbon (TOC) are high, the electrode activity in the capacitive desalination process is inhibited and the desalination efficiency decreases. Therefore, in order to improve the desalination efficiency of the capacitive desalination process, the turbidity and total organic carbon (TOC) of raw water must be managed to an appropriate value.

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

Accordingly, the present invention applies TDS (total dissolved solids) as a criterion for classifying the properties of raw water in applying the selective pretreatment process of the capacitive desalination process. That is, the properties of raw water are classified based on the value of TDS, and a selective 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 TDS of raw water is 200-700 ppm, apply both the filtration and adsorption process or only the adsorption process. If the TDS of the raw water is less than 200 ppm, skip both the filtration and adsorption process and pretreat with the membrane filtration process (MF). Can be replaced. In addition, when the TDS of raw water is 701 to 4000 ppm, a pretreatment process may be configured by adding a coagulation process or a ceramic separation membrane process before proceeding with the filtration process and the adsorption process.

An object of the present invention is to control the turbidity and total organic carbon (TOC) of raw water introduced into the capacitive desalination process through such a pretreatment process to a turbidity of 0.5 NTU or less and a total organic carbon (TOC) of 4 ppm or less.

The TDS value of raw water for applying the selective pretreatment process is classified as less than 200ppm TDS, 200~700ppm TDS, and 701~4000ppm TDS according to the characteristics of the raw water depending on the pollutant source. As a result of measurement through experiments, the TDS of the sewage treatment plant, which is one of the raw water of the storage desalination process, has a TDS of less than 200 ppm, and the cooling water discharged from various facilities has a TDS of 200-700 ppm, and industrial complex wastewater is 701-4000 ppm. Is showing the TDS value of

Therefore, in the case of effluent water from a sewage treatment plant with TDS less than 200 ppm, the membrane filtration process (MF) is treated by a capacitive desalination process after applying a pre-treatment process, and in the case of cooling water with TDS 200-700 ppm, both the filtration process and the adsorption process are pre-processed In the case of industrial complex wastewater with a TDS of 701 to 4000 ppm, the capacitive desalination process is performed after a coagulation process or a pretreatment process with additional ceramic separation membrane process applied before proceeding with the filtration process and adsorption 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) have similar tendency to TDS (Total Dissolved Solids). Specifically, raw water with TDS less than 200 ppm has a membrane pollution index (SDI) less than 2, raw water with TDS 200-700 ppm has a membrane pollution index (SDI) of 2-5, and raw water with a TDS exceeding 700 ppm has a membrane pollution 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 a TDS of less than 200 ppm has a turbidity of less than 0.5 NTU and a total organic carbon (TOC) of less than 2 ppm, and a raw water with a TDS of more than 700 ppm tends to have a turbidity of more than 10 NTU and a total organic carbon (TOC) of more than 30 ppm. . In the case of raw water with TDS of 200 to 700 ppm, that is, with a membrane contamination index (SDI) of 2 to 5, it is subdivided into two types. This is to apply the pretreatment process more effectively. If the TDS is 200 to 700 ppm, that is, when the membrane contamination index (SDI) is 2 to 5, the turbidity is 0.5 to 1.5 and the total organic carbon (TOC) is 1 to 12, and the turbidity is 1.5 to 8 and the total organic carbon (TOC) is 12 It can be classified into the case of ∼30. In the former case, that is, when 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, that is, the turbidity is 1.5 to 8 and the total organic carbon (TOC) is 12 In the case of ∼30, both filtration and adsorption processes are applied.

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

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 a filter carrier and an adsorption carrier in one reaction tank, one filtration process and an adsorption process may both proceed. Here, as an embodiment, activated filter media (AFM) may be used as the filter carrier, and granular activated carbon (GAC) may be used as the adsorption 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: Characteristics of raw water>

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

<Constellation of the enemy>
sewer
Effluent First
Industrial complex wastewater Second
Industrial complex 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 separation membrane, AFM, and MS (miracle sand) were prepared as a filter carrier or adsorption carrier, and the TOC and turbidity removal ability of each carrier was evaluated.

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

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

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

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

In the next experiment, a column filled with AFM and a column filled with GAC were sequentially drained, and water having a TDS of 700 ppm or less was sequentially passed through both columns, and then TOC and turbidity changes were measured. Referring to FIGS. 4A and 4B, it can be seen that the TOC is kept constant compared to the GAC alone column.

Claims (6)

As a pretreatment process for raw water flowing into the storage type desalination device,
The properties of raw water are classified into less than 200ppm TDS, 200~700ppm TDS, and 701~4000ppm TDS,
If the property of the raw water is less than 200 ppm of TDS, the membrane filtration process (MF) is applied as the pretreatment process, and when the property of the raw water is TDS 701 to 4000 ppm, the coagulation process, filtration process, and adsorption process are sequentially applied as the pretreatment process, or the ceramic separator process, Filtration process and adsorption process are sequentially applied,
If the nature of the raw water is TDS 200~700ppm, only the adsorption process is applied as the pretreatment process or the filtration process and the adsorption process are applied sequentially.
If the nature of raw water is 200-700 ppm TDS,
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 the pretreatment process.
If the turbidity is 1.5-8 and the total organic carbon (TOC) is 12-30, the filtration process and the adsorption process are sequentially applied as a pretreatment process.
The pretreatment method of the capacitive desalination process according to the properties of the raw water, characterized in that the turbidity of the raw water flowing into the capacitive desalination process through the pretreatment process is controlled to 0.5 NTU or less and the total organic carbon (TOC) to 4 ppm or less.
delete The method of claim 1, wherein the raw water having a TDS of less than 200 ppm has a membrane contamination index (SDI) of less than 2, the raw water having a TDS of 200 to 700 ppm has a membrane contamination index (SDI) of 2 to 5, and the raw water having a TDS exceeding 700 ppm is A pretreatment method of a capacitive desalination process according to the properties of 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 and a total organic carbon (TOC) of less than 2 ppm, and the 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 exceeding.
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 one filtration process and an adsorption process are both carried out by filling both the filter carrier and the adsorption carrier in one reaction tank. The pretreatment method of the capacitive desalination process according to the properties of the raw water, characterized in that it can be.
The method of claim 5, wherein the filter carrier is activated filter media (AFM), and the adsorption carrier is granular activated carbon (GAC).

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