CN107244729B - Method for controlling generation of halogen-containing by-products in drinking water treatment - Google Patents
Method for controlling generation of halogen-containing by-products in drinking water treatment Download PDFInfo
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
- C02F1/4672—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electrooxydation
Abstract
The invention relates to a method for controlling the generation of halogen-containing byproducts in drinking water treatment, wherein the water body to be treated is surface water or underground water; the TOC of the water body to be treated is 0.5-3.5 mg/L, the percentage of hydrophobic natural organic matters is 40-70%, the pH value is 6.0-8.5, and the conductivity is more than 150 mu S/cm; in the treatment process, the bottom micropore aeration mode is adopted to carry out O treatment310-15% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode arranged at the bottom, and introducing direct current to two ends of the electrode; and injecting the water body to be treated into the ozone contact tower while introducing the mixed gas. Aiming at the water body, the method not only can effectively purify the water body, but also has less types and contents of toxic byproducts after purification, does not bring side effects to human bodies, and is suitable for purifying drinking water.
Description
Technical Field
The invention relates to the technical field of water treatment, in particular to a water treatment method combining ozone oxidation and electrochemistry.
Background
Natural Organic Matter (NOM) is widely present in surface water and shallow groundwater and is a very complex mixture of organic matter of different types, molecular weight, size, structural functional groups, etc. In addition, chloride ions are widely present in natural water bodies, particularly in coastal areas, and the concentration of chloride ions in surface water or underground water can be as high as several hundred milligram liters. In conventional electrochemical water treatment processes, NOM reacts with chlorine generated at the anode: NOM + HOCl → Trihalomethanes (THMs) + haloacetic acids (HAAs) + other disinfection by-products (DBPs). In addition, for common ozone disinfection, halogen-containing byproducts such as trihalomethane and haloacetic acid are directly generated in the process. Among them, Trihalomethanes (THMs) and haloacetic acids (HAAs) have been identified as carcinogenic, teratogenic, mutagenic "triprodogenic" substances, which are seriously harmful to the human body.
Electrochemical oxidation processes are often limited by mass transfer of contaminants and are not effective in removing contaminants, and ozone oxidation also has a selective oxidation problem. The electrocatalysis ozone technology is a new technology which is expected to improve the traditional electrochemistry and ozone technology, does not need secondary treatment, and greatly improves the water treatment effect.
There are many key scientific and technical issues that require systematic study in the electrocatalytic ozone technology. Wherein, the generation and control of halogen-containing byproducts (including inorganic halide and organic halide) are the core problems for determining whether the electrocatalytic ozone technology can be really applied to the water treatment, especially the fields of drinking water treatment, advanced sewage treatment and recycling and the like.
Disclosure of Invention
The invention aims to provide a water treatment method which can effectively remove pollutants in a specific water body to be treated and has less halogen-containing byproducts and low concentration in the water body.
The method comprises the following steps: the TOC of the water body to be treated is 0.5-3.5 mg/L, wherein the percentage of hydrophobic natural organic matters is 40-70%, the pH value is 6.0-8.5, and the conductivity is more than 150 mu S/cm; the method comprises the following operations:
adopting bottom micropore aeration mode to make O310-15% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode arranged at the bottom, and introducing direct current to two ends of the electrode; injecting the water body to be treated into the ozone contact tower while introducing the mixed gas, wherein the hydraulic retention time is 10-20 min, and immediately outputting the water body;
said O is3The ratio of the amount of the wastewater to be treated to the TOC is 0.3-3.0;
the current density of the cathode end is 0.3-3 mA/cm2。
For a water body with 0.5-3.5 mg/L of TOC, 6.0-8.5 of pH value and more than 150 mu S/cm of conductivity, because the TOC content is low, pollutants in water can be effectively removed by adopting more conventional operation in the process of treating the water body by utilizing an electro-catalysis ozone technology, but for a water body (accounting for the percentage of the TOC) with 40-70% of the content of hydrophobic natural organic matters (weak polar or non-polar organic matters such as benzene, polycyclic aromatic hydrocarbon and the like), a halogen-containing byproduct with higher content is usually generated in the treatment process by adopting the technology, the technical scheme of the application can effectively remove the organic matters in the water body after treating the water by adjusting the conditions of ozone and electrochemical treatment, and only a small amount of dichloroacetic acid byproduct is generated in the treated water body without generating trichloroacetic acid, the production of halogen-containing by-products can be greatly reduced compared to other treatment methods. Moreover, the method can effectively remove the common micropollutants in the water body, such as the drug micropollutants and the odor micropollutants.
Optionally, according to the method, when the content of chloride ions in the water body is greater than 5mg/L, even if the content of chloride ions in the water body is 50-400 mg/L or more, the generation of halogen-containing byproducts can be effectively controlled. The halogen-containing by-products in the water are generated by the action of the hypochlorous acid converted from the chloride ions in the water and the organic matters in the water, and the amount of the by-products converted into the hypochlorous acid is greatly increased under the condition of high content of the chloride ions in the water, so that the generation amount of the by-products is greatly increased.
Optionally, when the concentration of odor type micro-pollutants in the water body to be treated is 0.01-30 mug/L, by adopting the method disclosed by the invention, the micro-pollutants can be effectively removed, and the generation of halogen-containing byproducts can be controlled. The micro-pollutants in the water body refer to pollutants with the concentration of mu g/L or ng/L in the water body, and the odor type micro-pollutants refer to substances which can generate peculiar smell. Representative odor type micro-pollutants in the water body mainly comprise 2-methylisoborneol and geosmin; preferably, the concentration of the 2-methylisoborneol is 0.01-10 mu g/L, and the concentration of the geosmin is 0.01-10 mu g/L.
Preferably, the method controls the current density of the cathode end to be 0.8-2 mA/cm2。
Preferably, the method of the present invention, controlling O3The ratio of the amount of the wastewater to be treated to the TOC of the water to be treated is 2 to 2.5.
Optionally, under the condition that the concentration of chloride ions in the water body to be treated is higher, the method of the present application can still effectively remove the odor type micropollutants in the water, and the treatment conditions are as follows:
the TOC of the water body to be treated is 0.5-3.5 mg/L, the percentage of hydrophobic natural organic matters is 40-70%, the pH value is 6.0-8.5, the conductivity is more than 150 mu S/cm, the concentration of chloride ions is 50-400 mg/L, and the concentration of odor type micro-pollutants is 0.01-30 mu g/L, and the method comprises the following operations:
adopting bottom micropore aeration mode to make O310-15% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode arranged at the bottom, and introducing direct current to two ends of the electrode; injecting the water body to be treated into the ozone contact tower while introducing the mixed gas, wherein the hydraulic retention time is 10-20 min, and immediately outputting the water body;
said O is3The ratio of the amount of the wastewater to be treated to the TOC is 0.3-3.0;
the current density of the cathode end is 0.3-3 mA/cm2。
For the alternative scheme, the following conditions are adopted, the treatment effect is more ideal, the TOC of the water body to be treated is 0.5-3.5 mg/L, the percentage of hydrophobic natural organic matters is 40-70%, the pH value is 6.0-8.5, the conductivity is more than 150 mu S/cm, the concentration of chloride ions is 50-400 mg/L, the concentration of odor type micro pollutants in the water body is 0.01-30 mu g/L, the concentration of 2-methylisoborneol is 0.01-10 mu g/L, and the concentration of geosmin is 0.01-10 mu g/L; the method comprises the following operations:
adopting bottom micropore aeration mode to make O310-15% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode arranged at the bottom, and introducing direct current to two ends of the electrode; injecting the water body to be treated into the ozone contact tower while introducing the mixed gas, and discharging waterThe force retention time is 10-20 min, and the water body is immediately output;
said O is3The ratio of the amount of the wastewater to be treated to the TOC is 2-2.5;
the current density of the cathode end is 0.8-2 mA/cm2。
In the invention, the anode is selected from a titanium ruthenium plating electrode, a titanium platinum plating electrode, a titanium tantalum plating electrode, a titanium iridium plating electrode, a titanium rhodium plating electrode or a titanium iridium dioxide plating electrode, or an alloy electrode containing the two transition metals.
In the invention, the cathode is selected from a graphite electrode, a glassy carbon electrode, an activated carbon fiber electrode or a gas diffusion electrode; the gas diffusion electrode is a carbon paper/cloth/felt-polytetrafluoroethylene electrode, an activated carbon-polytetrafluoroethylene electrode, a carbon black-polytetrafluoroethylene electrode, a carbon nanotube-polytetrafluoroethylene electrode or a graphene-polytetrafluoroethylene electrode.
In a preferred combination, the anode is a titanium ruthenium-plated electrode; the cathode is a carbon paper-polytetrafluoroethylene electrode, a carbon black-polytetrafluoroethylene electrode or a graphite electrode.
The mixed gas of the invention can be composed of O2And O3Directly mixed or prepared by other methods, preferably by an ozone generator. The preparation method by adopting the ozone generator comprises the following specific steps: mixing O with2Passing through an ozone generator, part of O2Conversion to O3The output gas, i.e. O310-15% by volume of O2And O3And (4) mixing the gases.
Introducing O into an ozone contact tower3And O2And when the gas is mixed, the aeration mode is bottom micropore aeration, and the aeration flow rate of the micropore aeration is 0.01-10L/min. The aeration mode enables the gas entering the ozone contact tower to be dispersed into micro bubbles and to be better contacted with the water body in the ozone contact tower, and simultaneously, H generated at the bottom2O2Is carried by gas and diffused to the top of the ozone contact tower and can be mixed with O3Better reaction. The bottom of the ozone contact tower can be provided with a glass sand core, and the mixed gas becomes micro bubbles after passing through the glass sand core and can contact with the liquid in the ozone contact towerThe full contact is favorable for mass transfer.
In the present invention, O3The amount of the compound (b) can be measured by a conventional technique in the art, but the present invention is not limited thereto. As a preferred embodiment, O3The input amount can be detected by a KI absorption method, and the method comprises the following specific steps: introducing the mixed gas with the same composition as the invention into KI solution with the same introduction amount as the invention, and changing the color of the solution until O3After the KI solution absorbs the O-containing compound, the KI solution is reversely titrated by sodium thiosulfate, the color of the solution is reversely converted, and the O can be indirectly obtained by calculating the amount of the sodium thiosulfate3The amount of (2) introduced.
The electrodes adopted by the invention are abundant in the market and can be directly purchased.
The power supply used for electrifying the invention is a common direct current stabilized power supply.
The ozone generator used in the present invention preferably comprises the following components: the ozone generator is connected with the ozone contact tower, the glass sand core is arranged at the bottom of the ozone contact tower, the cathode and the anode are fixed at the upper part of the glass sand core, and the anode and the cathode are respectively connected with the anode and the cathode of the direct current power supply.
Wherein the glass sand core is a glassy spongy solid with disordered holes in the middle, and O coming out of the ozone generator3And O2The glass sand core is changed into micro bubbles with the diameter less than 1mm, the micro bubbles can be fully contacted with liquid in an ozone contact tower, mass transfer is facilitated, and the glass sand core can also be replaced by stainless steel, other corrosion-resistant ceramic materials, anti-oxidation materials such as polytetrafluoroethylene and the like and common gas distribution plates in engineering, such as microporous titanium gas distribution plates.
The Hydraulic Retention Time (HRT) of the present invention refers to the average Retention Time of the water body to be treated in the reactor.
In the actual production process, the mixed gas is introduced into the ozone contact tower, direct current is introduced to the two ends of the electrodes, the water to be treated is injected into the ozone contact tower, the water is output and the like, and a continuous and uniform running mode or an intermittent running mode can be adopted.
As a more preferred exemplary embodiment, the method of the present invention comprises the steps of: the water body to be treated is surface water or underground water; the TOC of the water body to be treated is 1.3-2.6 mg/L, the percentage of hydrophobic natural organic matters is 52-58%, the concentration of 2-methylisoborneol is 0.5-2 mug/L, the concentration of geosmin is 0.5-2 mug/L, the pH value is 6.0-8.5, and the conductivity is more than 150 mug/cm; the method comprises the following operations:
adopting bottom micropore aeration mode to make O310-15% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode arranged at the bottom, and introducing direct current to two ends of the electrode; injecting the water body to be treated into the ozone contact tower while introducing the mixed gas, wherein the hydraulic retention time is 10-20 min, and immediately outputting the water body;
said O is3The ratio of the input amount of the (D) to the TOC of the water body to be treated is 2.5;
the current density of the cathode terminal is 2mA/cm2；
The anode is a titanium ruthenium plating electrode; the cathode is a carbon paper-polytetrafluoroethylene electrode, a carbon black-polytetrafluoroethylene electrode or a graphite electrode.
The above-mentioned more preferable embodiment is still applicable when the concentration of the chloride ion is 50-300 mg/L.
As a most preferred exemplary embodiment, the method of the present invention comprises the steps of: the water body to be treated is surface water or underground water; the TOC of the water body to be treated is 2.3-2.6 mg/L, the percentage of hydrophobic natural organic matters is 52-58%, the concentration of 2-methylisoborneol is 1.0-2 mug/L, the concentration of geosmin is 1.0-2 mug/L, the pH value is 6.0-8.5, and the conductivity is more than 150 mug/cm; the method comprises the following operations:
adopting bottom micropore aeration mode to make O310-15% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode arranged at the bottom, and introducing direct current to two ends of the electrode; introducing mixed gas and simultaneously mixingInjecting the water body to be treated into the ozone contact tower, wherein the hydraulic retention time is 10-20 min, and immediately outputting the water body;
said O is3The ratio of the input amount of the (D) to the TOC of the water body to be treated is 2.5;
the current density of the cathode terminal is 2mA/cm2；
The anode is a titanium ruthenium plating electrode; the cathode is a carbon paper-polytetrafluoroethylene electrode, a carbon black-polytetrafluoroethylene electrode or a graphite electrode.
The most preferable scheme is still applicable when the concentration of the chloride ions is 50-300 mg/L, and the effect is better when the concentration of the chloride ions is 50-100 mg/L.
Another object of the invention is to protect the use of the method in the production of drinking water.
The scheme of the invention has the following beneficial effects:
after the water body is specially treated by the method, soluble organic matters in the water body can be efficiently removed, and compared with the traditional electrochemical or ozone treatment method, the method can integrate the advantages of the water body and the soluble organic matters and abandon the disadvantages of the water body and the soluble organic matters. The treated water body has low halogen-containing by-product types and content, only generates a very small amount of trichloromethane and trichloroacetic acid, and the generation of dichloroacetic acid is within an acceptable range. If the electrochemical method is directly adopted for treatment, not only the natural organic odor substances in the water body cannot be effectively removed, but also a large amount of halogen-containing byproducts are generated. The method mainly has the catalytic action guided by the cathode, and is not similar to the traditional electrochemical method, the larger the area of the anode is, the better the effect is, therefore, the area selection range of the anode is large, and the use is more flexible and free.
Drawings
FIG. 1 is a schematic view of an apparatus used in an embodiment of the present invention; in the figure: 1. a reaction column; 2. an anode; 3. a cathode; 4. a water inlet; 5. a water outlet; 6. a gas distribution plate; 7. an air inlet; 8. an air outlet; 9. a peristaltic pump; 10. a direct current power supply; 11. an ozone generator; 12. an ozone detector; 13. a water storage tank; 14. an oxygen cylinder.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Example 1
In the water body to be treated, the initial TOC value is 3.5mg/L, the initial pH value is 8.01, and the hydrophobic natural organic matters account for 60 percent of the natural organic matters. The concentration of 2-methylisoborneol in the water body is 1 mug/L, the concentration of geosmin is 1 mug/L, and the concentration of chloride ions is 50 mg/L.
The apparatus used in this example is shown in FIG. 1.
Treating a water body according to the following operations:
mixing O with2Introducing into an ozone generator to prepare O 310% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode at the bottom continuously and uniformly by adopting a bottom micropore aeration mode, and continuously introducing direct current to two ends of the electrode; continuously injecting the water body to be treated into the ozone contact tower at a constant speed while introducing the mixed gas, wherein the hydraulic retention time is 20min, and immediately outputting the water body;
said O is3The ratio of the input amount of the (D) to the TOC of the water body to be treated is 2.5;
the anode is 50cm in area2The cathode is a titanium ruthenium-plated electrode having an area of 50cm2The graphite electrode of (4); the direct current of 60mA is continuously conducted, and the current density of the cathode end is 1.2mA/cm2. The change of odor substances in the water body in the treatment process is shown in table 1, the removal rate of 2-methylisoborneol and geosmin by the electro-catalytic ozone technology can reach 80%, and the amount of toxic by-products is shown in table 2.
TABLE 1
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 70.2％ | 82.5％ |
TABLE 2
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 1.54ug/L | 19.41ug/L | 1.62ug/L |
Example 2
The treatment process was identical to the treatment conditions of example 1, except that: continuously introducing 20mA direct current, wherein the current density is 0.4mA/cm2。
The change of odorants in the treated water is shown in Table 7, and the amounts of toxic by-products are shown in Table 8.
TABLE 7
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 59.3％ | 71.8％ |
TABLE 8
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 0.23ug/L | 10.10ug/L | 0.92ug/L |
Example 3
The treatment process was identical to the treatment conditions of example 1, except that: continuously introducing 40mA direct current, wherein the current density is 0.8mA/cm2。
The change of the odor substances in the treated water body is shown in Table 3, and the amounts of toxic by-products are shown in Table 4.
TABLE 3
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 62.1％ | 75.2％ |
TABLE 4
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 0.51ug/L | 13.58ug/L | 1.13ug/L |
Example 4
The treatment process was identical to the treatment conditions of example 1, except that: continuously introducing 80mA direct current, wherein the current density is 1.6mA/cm2。
The change of the odor substances in the treated water body is shown in Table 5, and the amounts of toxic by-products are shown in Table 6.
TABLE 5
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 67.5％ | 79.3％ |
TABLE 6
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 2.31ug/L | 24.35ug/L | 2.38ug/L |
As can be seen from the above embodiments 1 to 4, for the same water body, under the condition that other conditions are not changed, the intensity of the direct current (i.e., the current density) is changed, and the treatment effects are different, but the effect is not better under the condition that the current intensity is larger, and different water bodies have different optimum conditions.
Example 5
In the water body to be treated, the initial TOC value is 0.5mg/L, the initial pH value is 6.5, and the hydrophobic natural organic matters account for 70% of the natural organic matters. The concentration of 2-methylisoborneol in the water body is 1 mug/L, the concentration of geosmin is 1 mug/L, and the concentration of chloride ions is 50 mg/L.
The apparatus used in this example is shown in FIG. 1.
Treating a water body according to the following operations:
mixing O with2Introducing into an ozone generator to prepare O315% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode at the bottom continuously and uniformly by adopting a bottom micropore aeration mode, and continuously introducing direct current to two ends of the electrode; continuously injecting the water body to be treated into the ozone contact tower at a constant speed while introducing the mixed gas, wherein the hydraulic retention time is 20min, and immediately outputting the water body;
said O is3The ratio of the input amount of the (D) to the TOC of the water body to be treated is 2;
the anode is 50cm in area2The cathode is a titanium ruthenium iridium-plated electrode with an area of 50cm2The graphite electrode of (4); the direct current of 60mA is continuously conducted, and the current density of the cathode end is 1.2mA/cm2. The change of odorants in water during the treatment is shown in Table 9, and the amounts of toxic by-products are shown in Table 10.
TABLE 9
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 75.3％ | 89.7％ |
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 0.98ug/L | 10.58ug/L | 0.75ug/L |
Example 6
Compared with example 5, the difference is that the initial TOC value in the water body is 2.5mg/L, the initial pH value is 7.5, and the hydrophobic natural organic matters account for 70 percent of the natural organic matters.
The change of odorants in the treated water is shown in Table 11, and the amounts of toxic by-products are shown in Table 12.
TABLE 11
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 73.96％ | 87.32％ |
TABLE 12
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 2.53ug/L | 26.58ug/L | 2.42ug/L |
It can be seen from examples 5 and 6 that the same treatment of water bodies having different contents of hydrophobic natural organic substances resulted in different results, and that the amount of halogen-containing by-products produced after the treatment was within the range of commercially acceptable concentrations even when the water bodies having a higher content of hydrophobic natural organic substances were treated.
Example 7
The difference compared to example 1 is that the anode has an area of 30cm2The cathode is a titanium ruthenium-plated electrode having an area of 30cm2The carbon paper electrode of (1).
The change of odorants in the treated water is shown in Table 13, and the amounts of toxic by-products are shown in Table 14.
Watch 13
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 73.96％ | 87.32％ |
TABLE 14
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 1.53ug/L | 16.58ug/L | 1.42ug/L |
Example 8
The treatment process was identical to the treatment conditions of example 1, except that: the concentration of chloride ions in the water body to be treated is 300 mg/L.
The change of odorants in the treated water is shown in Table 15, and the amounts of toxic by-products are shown in Table 16.
Watch 15
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 73.3％ | 84.1％ |
TABLE 16
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 2.15ug/L | 25.61ug/L | 1.78ug/L |
It can be seen from example 8 that the halogen-containing by-product control is equally effective after treatment even for very high concentrations of chloride ion in water.
Example 9
In the water body to be treated, the initial TOC value is 2.43mg/L, the initial pH value is 7.5, and the hydrophobic natural organic matters account for 55 percent of the natural organic matters. The concentration of 2-methylisoborneol in the water body is 1.5 mug/L, the concentration of geosmin is 1.5 mug/L, and the concentration of chloride ions is 50 mg/L.
The apparatus used in this example is shown in FIG. 1.
Treating a water body according to the following operations:
mixing O with2Introducing into an ozone generator to prepare O 310% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode at the bottom continuously and uniformly by adopting a bottom micropore aeration mode, and continuously introducing direct current to two ends of the electrode; continuously injecting the water body to be treated into the ozone contact tower at a constant speed while introducing the mixed gas, wherein the hydraulic retention time is 20min, and immediately outputting the water body;
said O is3The introduction amount and the waiting positionThe TOC ratio of the water conditioning body is 2.5;
the anode is 30cm in area2The cathode is a titanium ruthenium-plated electrode having an area of 30cm2The graphite electrode of (4); continuously supplying 60mA direct current, wherein the current density at the cathode end is 2mA/cm2. The change of odorants in the treated water is shown in Table 17, and the amounts of toxic by-products are shown in Table 16.
TABLE 17
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 78.5％ | 90.2％ |
Watch 18
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 1.12ug/L | 9.63ug/L | 1.24ug/L |
In this embodiment, the removal of the odorous substances from the water is optimized, and the amount of the disinfection by-products produced after the treatment can be controlled to a minimum.
Comparative examples 1 to 4
Comparative examples 1 to 4 correspond to examples 1 to 4, respectively, and the differences from examples 1 to 4 are that only the same direct current as in examples 1 to 4 is used for treating the water body, and ozone is not used for treating the water body, that is, direct currents of 20mA, 40mA, 60mA and 80mA are used for directly electrochemically treating the water body in comparative examples 1 to 4, and the results are shown in tables 19 to 26.
Results at 20mA current:
watch 19
Watch 20
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 12.09ug/L | 2.81ug/L | 1.24ug/L |
The result at a current of 40 mA:
TABLE 21
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 1.3％ | 3.5％ |
TABLE 22
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 124.04ug/L | 60.99ug/L | 21.69ug/L |
Results at a current of 60 mA:
TABLE 23
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 1.3％ | 3.5％ |
Watch 24
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 147.95ug/L | 64.34ug/L | 43.16ug/L |
The current is 80mA, and the result is that:
TABLE 25
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 1.3％ | 3.5％ |
Watch 26
From the above data, it can be seen that the odor substances in the water body treated by using a single direct current are basically not removed, and most importantly, high-concentration disinfection byproducts are generated under the condition of high current intensity.
Comparative example 5
The difference compared to example 1 is that the current used during the treatment is strongThe degree is 10mA/cm2At this time, the current density of the cathode was 0.2mA/cm2After the treatment, the change of the odorant in the water was as shown in Table 27, and the amounts of toxic by-products were as shown in Table 28.
Watch 27
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 58.4％ | 69.7％ |
Watch 28
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 2.67ug/L | 31.23ug/L | 4.31ug/L |
From the above data, it can be seen that if the current intensity and current density are too small, on the one hand, 2-methylisoborneol and geosmin cannot be effectively removed, and on the other hand, the concentration of dichloroacetic acid as a disinfection by-product is too high.
Comparative example 6
The difference compared with example 1 is that during the treatment, O is present3The ratio of the amount of the odorous substances to the TOC of the water to be treated was 4, the change of the odorous substances in the treated water is shown in Table 29, and the amounts of the toxic by-products are shown in Table 30.
Watch 29
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 80.2％ | 90.4％ |
Watch 30
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 2.15ug/L | 19.89ug/L | 1.45ug/L |
From the above data, it can be seen that when O3When the amount of the ozone added is increased, the removal of smelly substances and the generation of a small amount of disinfection by-products can be ensured, but the addition amount of the ozone is too large, so that bromate by-products exceeding the standard by 6 times are generated in the treatment process.
Comparative example 7
The difference compared to example 1 is that the anode has an area of 5cm2The current density at this time was 12mA/cm2The change of odorants in the treated water is shown in Table 31, and the amounts of toxic by-products are shown in Table 32.
Watch 31
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 60.2％ | 71.3％ |
Watch 32
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 8.65ug/L | 12.36ug/L | 10.52ug/L |
When the anode area is small and the current density is too large, the polarization phenomenon between the electrodes is obvious, and the current density distribution is uneven, and the data show that the dichloroacetic acid in the treated water body can be effectively controlled, but the amounts of trichloromethane and trichloroethanol are obviously improved.
Comparative example 8
Comparative example 8 corresponds to example 8, and differs from example 8 in that the water body was treated with only the same direct current as in example 8 and not with ozone, that is, in comparative example 8, the water body was electrochemically treated directly with 60mA direct current, respectively, and the change of odorant in the treated water body is shown in table 33 and the amount of toxic by-products is shown in table 34.
Watch 33
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 2.5％ | 6.1％ |
Watch 34
From the above data, it can be seen that when the high-chlorine water body is treated electrochemically, not only the odor substances can not be removed basically, but also a large amount of disinfection byproducts are generated, which seriously exceed the discharge standard.
Comparative example 9
Compared with the example 1, the difference is that the water body is treated only by adopting the ozone concentration which is the same as that of the example 1, the water body is not treated by applying direct current, the change of the odor substances in the water body after treatment is shown in a table 35, and the amount of toxic by-products is shown in a table 36.
Watch 35
| Smelling material | 2-methylisoborneol | Geosmin |
| Removal rate | 41.2％ | 50.4％ |
Watch 36
| Disinfection by-product | Trichloromethane | Dichloroacetic acid | Trichloroacetic acid |
| Concentration after treatment | 1.21ug/L | 17.42ug/L | 1.45ug/L |
From the above data, it can be seen that when ozone is introduced, and direct current is not applied, the content of disinfection byproducts in the treated water body is slightly reduced, but the removal efficiency of 2-methylisoborneol and geosmin is obviously reduced.
Although the invention has been described in detail hereinabove by way of general description, specific embodiments and experiments, it will be apparent to those skilled in the art that many modifications and improvements can be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (9)
1. A method for controlling generation of halogen-containing byproducts in drinking water treatment is characterized in that TOC of a water body to be treated is 0.5-3.5 mg/L, percentage of hydrophobic natural organic matters is 40-70%, concentration of chloride ions is greater than 5mg/L, concentration of smelly micro-pollutants in the water body is 0.01-30 mu g/L, pH value is 6.0-8.5, and conductivity is greater than 150 mu S/cm; the method comprises the following operations:
adopting bottom micropore aeration mode to make O310-15% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode arranged at the bottom, and introducing direct current to two ends of the electrode; injecting the water body to be treated into the ozone contact tower while introducing the mixed gas, wherein the hydraulic retention time is 10-20 min, and immediately outputting the water body;
said O is3The ratio of the amount of the wastewater to be treated to the TOC is 2-2.5;
the current density of the cathode end is 0.4-2 mA/cm2。
2. The method according to claim 1, wherein the concentration of chloride ions in the water body to be treated is 50-400 mg/L.
3. The method of claim 1, wherein the olfactory micropollutants in the body of water comprise 2-methylisoborneol and geosmin.
4. The method of claim 3, wherein the concentration of 2-methylisoborneol is 0.01-10 μ g/L and the concentration of geosmin is 0.01-10 μ g/L.
5. A method according to any one of claims 1 to 4, wherein in the electrode: the anode is selected from a titanium ruthenium plating electrode, a titanium platinum plating electrode, a titanium tantalum plating electrode, a titanium iridium plating electrode, a titanium rhodium plating electrode or a titanium iridium dioxide plating electrode, or an alloy electrode containing titanium ruthenium, titanium platinum, titanium tantalum, titanium rhodium or titanium iridium;
and/or the cathode is selected from a graphite electrode, a glassy carbon electrode, an activated carbon fiber electrode or a gas diffusion electrode; the gas diffusion electrode is a carbon paper/cloth/felt-polytetrafluoroethylene electrode, an activated carbon-polytetrafluoroethylene electrode, a carbon black-polytetrafluoroethylene electrode, a carbon nanotube-polytetrafluoroethylene electrode or a graphene-polytetrafluoroethylene electrode.
6. The method of claim 5, wherein the anode is a titanium ruthenium plated electrode; the cathode is a carbon paper-polytetrafluoroethylene electrode, a carbon black-polytetrafluoroethylene electrode or a graphite electrode.
7. The method according to claim 1, wherein the body of water to be treated is surface water or groundwater; the TOC of the water body to be treated is 1.3-2.6 mg/L, the percentage of hydrophobic natural organic matters is 52-58%, the concentration of 2-methylisoborneol is 0.5-2 mug/L, the concentration of geosmin is 0.5-2 mug/L, the pH value is 6.0-8.5, and the conductivity is more than 150 mug/cm; the method comprises the following operations:
adopting bottom micropore aeration mode to make O310-15% by volume of O2And O3Introducing the mixed gas into an ozone contact tower with a cathode and an anode arranged at the bottom, and introducing direct current to two ends of the electrode; injecting the water body to be treated into the ozone contact tower while introducing the mixed gas, wherein the hydraulic retention time is 10-20 min, and immediately outputting the water body;
said O is3The ratio of the input amount of the (D) to the TOC of the water body to be treated is 2.5;
the current density of the cathode terminal is 2mA/cm2；
The anode is a titanium ruthenium plating electrode; the cathode is a carbon paper-polytetrafluoroethylene electrode, a carbon black-polytetrafluoroethylene electrode or a graphite electrode.
8. The method according to claim 1, wherein the concentration of the chloride ions in the water body to be treated is 50-300 mg/L.
9. Use of the method of any one of claims 1 to 8 in the production of drinking water.
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