Production and preparation process and application of hydroxyl coagulant aid

Abstract

The invention relates to the technical field of hydroxyl coagulant aid production and preparation, in particular to a hydroxyl coagulant aid production and preparation process which comprises the following steps: S1, material selection: organic components: chitosan and a sodium alginate biomass-based material; inorganic components: aluminum salt, ferric salt, calcium salt and multivalent metal salt; s2, metal salt dissolution: firstly, aluminum salt is dissolved in a proper amount of water, the pH value of the solution is adjusted to 4.5-5.5, and it is ensured that metal ions are completely dissolved; s3, dissolving organic matters: in another container, dissolving chitosan and sodium alginate in an acidic aqueous solution, and controlling the pH value to be 5-6; and S4, synthesizing a compound: mixing the two solutions, and slowly adding a proper amount of alkaline solution while stirring. Compared with traditional polymeric aluminum salt, the hydroxyl coagulant aid prepared by the method can quickly form large and uniform flocs after being dissolved in water, and suspended solids, grease and heavy metal ions in water are effectively removed. Experimental data show that the removal rate can reach 90% or above.

Description

Technical Field

[0001] The invention relates to the technical field of production and preparation of hydroxyl coagulant aids, in particular to a production and preparation process of a hydroxyl coagulant aid and application thereof. Background Art

[0002] Hydroxyl coagulants are an important water treatment chemical widely used in the treatment of drinking water, wastewater and various water purification processes. Their main function is to aggregate suspended solids and colloidal particles in water into larger coagulants through adsorption and bridging, and finally remove them through precipitation. These coagulants usually contain hydroxyl functional groups, have excellent hydrophilicity and high coagulability;

[0003] Current hydroxy coagulants (usually substances based on multivalent metal salts or polymers, such as aluminum salts, iron salts and polyaluminum chloride, etc.) are widely used in water treatment, wastewater treatment, oil field water injection and other fields, but they still have the following defects:

[0004] Low efficiency: Traditional hydroxy coagulants usually require a long reaction time and a slow reaction rate, and cannot quickly achieve the best flocculation effect.

[0005] By-product problem: During the use of coagulant aids such as polyaluminium chloride, a large amount of wastewater and sludge will be generated, which increases the difficulty and cost of treatment.

[0006] Poor environmental friendliness: Some traditional hydroxyl coagulants contain heavy metal ions, which may pollute water bodies and affect water quality after use.

[0007] High operational complexity: In the existing preparation process, the reaction conditions (such as temperature, pH value, reaction time) are relatively strict and difficult to control.

[0008] Therefore, a production and preparation process of a hydroxy coagulant aid and its application are proposed. Summary of the invention

[0009] The purpose of the present invention is to provide a production and preparation process of a hydroxy coagulant and its application, wherein the coagulant is a composite of biomass-derived organic matter (such as chitosan, sodium alginate, etc.) and multivalent metal ions (such as aluminum and iron ions). By optimizing the synthesis process, the coagulant not only has good flocculation performance, but is also environmentally friendly, can quickly form flocs under different conditions and effectively remove pollutants in water, so as to solve the problems raised in the above-mentioned background technology.

[0010] To achieve the above object, the present invention provides the following technical solution: a production process of a hydroxy coagulant aid, comprising the following steps:

[0011] S1. Material selection:

[0012] Organic components: chitosan, sodium alginate biomass-based materials

[0013] Inorganic components: aluminum salts, iron salts, calcium salts, multivalent metal salts;

[0014] S2. Dissolving metal salts: First, dissolve aluminum salts in an appropriate amount of water and adjust the pH value of the solution to 4.5-5.5 to ensure that the metal ions are completely dissolved;

[0015] S3, dissolving organic matter: in another container, dissolving chitosan and sodium alginate in an acidic aqueous solution, and controlling the pH value at 5-6;

[0016] S4. Synthesizing a complex: Mix the two solutions and slowly add an appropriate amount of alkaline solution under stirring, wherein the alkaline solution is a sodium hydroxide solution, and adjust the pH value to 6.5-7.5 to promote the complexation reaction between the metal ions and the organic matter;

[0017] S5. Precipitation and separation of flocculants: After the reaction, the obtained composite hydroxy coagulant is separated by filtration, centrifugation and sedimentation to obtain the final product;

[0018] S6. Drying and powdering: Dry the separated product at low temperature to obtain a powdered hydroxy coagulant.

[0019] Preferably, in the S1, material selection, in water with high heavy metal ion concentration, iron salt is selected as the inorganic group.

[0020] Preferably, in S2, when dissolving metal salt or aluminum salt, the solution temperature is controlled at 45°C-50°C and stirred at a medium speed of 300rpm-500rpm.

[0021] Preferably, the mixing temperature in said S4, synthesis of the composite is controlled at 20°C-30°C.

[0022] Preferably, in the S5, precipitation and separation of the flocculant, the sedimentation process takes 30 minutes to 60 minutes, the filter mesh size is 0.45 μm, and the centrifugal speed is 3000 rpm to 5000 rpm.

[0023] Preferably, the method also includes optimizing the concentration of the coagulant aid, specifically determining the pollutant characteristics of different water qualities, determining the optimal concentration range through experiments, and predicting the effects of different concentrations on the flocculation effect.

[0024] Preferably, the pollutant characteristics of different water qualities are determined by using water quality monitoring instruments and laboratory analysis to obtain the pollutant concentrations in water samples, including suspended matter, oil, soluble organic matter, and heavy metal ions, and at the same time measuring the pH value, turbidity, chemical oxygen demand, total suspended solids, and dissolved oxygen index of the water samples to determine the specific type of water quality.

[0025] Preferably, the optimal concentration range is determined by experiments, and multiple concentration gradients are designed for experiments, with the intervals gradually increasing from low concentration to high concentration. During the experiment, the removal rate, sedimentation velocity, and particle size indexes at different concentrations are recorded.

[0026] Preferably, the influence of different concentrations on the flocculation effect is predicted, a mathematical model is established based on the experimental data, the flocculation effect at different concentrations is predicted, and it is applied to the actual process design. Data collection and analysis: collect key data in the experiment, removal rate, sedimentation velocity, and floc size at different concentrations, perform regression analysis on these data, and establish a mathematical model between the reaction rate and the concentration of the coagulant aid. Commonly used models include the first-order reaction kinetic model:

[0027]

[0028] Where C is the pollutant concentration and k is the reaction rate constant.

[0029] The invention discloses an application of a hydroxy coagulant aid, which is mainly used in water treatment and drinking water purification, industrial and urban sewage treatment.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] Improved flocculation effect: Compared with traditional polyaluminium salts, the hydroxy coagulant prepared by this method can quickly form larger and more uniform flocs after dissolving in water, effectively removing suspended matter, grease and heavy metal ions in water. Experimental data show that the removal rate can reach more than 90%.

[0032] Environmentally friendly: The coagulant aid prepared by this method has low pollution to water bodies after being dissolved and does not produce harmful by-products.

[0033] Easy operation: The process is relatively simple, suitable for large-scale production, has low requirements on reaction conditions and is highly operable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 The present invention is a process flow chart for the production of the hydroxy coagulant aid;

[0036] Figure 2 It is a comparison diagram between Example 1 and Example 2 of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] See also Figure 1 to Figure 2 , the present invention provides a technical solution:

[0039] A hydroxy coagulant production process comprises the following steps:

[0040] S1. Material selection:

[0041] Organic components: chitosan, sodium alginate biomass-based materials;

[0042] Inorganic components: polyvalent metal salts such as aluminum salts, iron salts, and calcium salts;

[0043] S2. Dissolving metal salts: First, dissolve aluminum salts in an appropriate amount of water and adjust the pH value of the solution to 4.5-5.5 to ensure that the metal ions are completely dissolved;

[0044] S3, dissolving organic matter: in another container, dissolving chitosan and sodium alginate in an acidic aqueous solution, and controlling the pH value at 5-6;

[0045] S4. Synthesizing a complex: Mix the two solutions and slowly add an appropriate amount of alkaline solution under stirring, wherein the alkaline solution is a sodium hydroxide solution, and adjust the pH value to 6.5-7.5 to promote the complexation reaction between the metal ions and the organic matter;

[0046] S5. Precipitation and separation of flocculants: After the reaction, the obtained composite hydroxy coagulant is separated by filtration, centrifugation and sedimentation to obtain the final product;

[0047] S6. Drying and powdering: Dry the separated product at low temperature to obtain a powdered hydroxy coagulant.

[0048] Specifically, in the S1, material selection, in water with high heavy metal ion concentration, iron salt is selected as the inorganic group.

[0049] Specifically, in S2, when dissolving metal salt and aluminum salt, the solution temperature is controlled at 45° C.-50° C. and stirred at a medium speed of 300 rpm-500 rpm.

[0050] Specifically, the mixing temperature in the S4 synthetic composite is controlled at 20°C-30°C.

[0051] Specifically, the S5, the precipitation and separation of the flocculant, the sedimentation process time is 30 minutes to 60 minutes, the filter mesh number is 0.45 μm, and the centrifugal speed should be adjusted according to the particle size and density. Usually, a speed of 3000rpm-5000rpm has a better effect.

[0052] Specifically, it also includes the optimization of coagulant concentration, which involves determining the pollutant characteristics of different water qualities, determining the optimal concentration range through experiments, and predicting the impact of different concentrations on flocculation results.

[0053] Specifically, the pollutant characteristics of different water qualities are determined by using water quality monitoring instruments and laboratory analysis to obtain the pollutant concentrations in water samples, including suspended solids, grease, dissolved organic matter (COD), heavy metal ions (such as lead, cadmium, copper, etc.). At the same time, the pH value, turbidity, chemical oxygen demand (COD), total suspended solids (TSS), dissolved oxygen (DO) and other indicators of the water sample are measured to determine the specific type of water quality.

[0054] Specifically, the optimal concentration range was determined through experiments, and multiple concentration gradients were designed for experiments, from low concentration (such as 0.1 g / L) to high concentration (such as 5 g / L), with the interval gradually increasing (such as increasing by 0.5 g / L each time). During the experiment, the removal rate, sedimentation velocity, particle size and other indicators at different concentrations were recorded.

[0055] Different water samples can be used for comparative experiments in the laboratory, and the concentration of the coagulant in the experimental group can be adjusted according to the concentration and type of pollutants.

[0056] Sedimentation velocity and particle size test:

[0057] The flocculent settling rate at different concentrations is measured by sedimentation experiments (such as sedimentation test tubes or sedimentation tanks). The concentration with a faster settling rate corresponds to the optimal flocculant concentration.

[0058] At the same time, the size and shape of the flocs are analyzed by microscope or laser particle size analyzer. Larger flocs help to increase the settling speed and removal rate.

[0059] Implementation effect:

[0060] Gradient experiments can intuitively compare the specific effects of different concentrations on water quality improvement and determine the optimal concentration range.

[0061] By evaluating the removal rate, sedimentation velocity, particle size and other indicators, the concentration of the coagulant is optimized to ensure the best effect under different water quality conditions.

[0062] Specifically, the mathematical model is established to predict the effect of different concentrations on the flocculation effect:

[0063] Objective: To establish a mathematical model based on experimental data, predict the flocculation effect at different concentrations, and apply it to actual process design.

[0064] Optimization measures:

[0065] Data collection and analysis:

[0066] Collect key data in the experiment, such as removal rate, sedimentation velocity, floc size, etc. at different concentrations.

[0067] Regression analysis is performed on these data to establish a mathematical model between reaction rate and coagulant concentration. Commonly used models include first-order reaction kinetic models (such as Langmuir, etc.) and second-order reaction kinetic models.

[0068] Mathematical model establishment:

[0069] First-order reaction kinetic model: often used to describe the reaction process of pollutant removal. For example, assuming that the removal of pollutants follows the first-order reaction rate formula:

[0070]

[0071] Where C is the pollutant concentration and k is the reaction rate constant.

[0072] Concentration-removal rate relationship: Based on experimental data, a relationship between concentration and removal rate can be established, such as obtaining a correlation function between coagulant concentration and suspended solids removal rate through fitting.

[0073] Model validation and application:

[0074] Fit the experimental data to verify the accuracy and applicability of the model. If the model prediction results are highly consistent with the experimental results, they can be applied in actual production.

[0075] In the actual water treatment process, this model is used to predict the optimal coagulant concentration required under different water qualities to achieve efficient water treatment.

[0076] Implementation effect:

[0077] Through mathematical models, the concentration of coagulant required under different water quality conditions can be accurately predicted, reducing the number of experiments and improving production efficiency.

[0078] The application of this model can further reduce the excessive use of coagulant aids, optimize cost control, and improve treatment efficiency.

[0079] The invention discloses an application of a hydroxy coagulant aid, which is mainly used in water treatment and drinking water purification, industrial and urban sewage treatment.

[0080] Assume that the pollutant concentration in a water body is C pollutantThe initial concentration of coagulant added is C coagulant , the pollutant removal rate obtained after the reaction is R. According to the reaction kinetics, the pollutant removal rate R can be expressed as:

[0081]

[0082] Among them, C final is the concentration of residual pollutants in the water after the reaction.

[0083] Assuming that the reaction is first-order kinetics, the removal rate constant k of the pollutant is related to the coagulant concentration C coagulant There is a linear relationship between:

[0084] k=k0·C coagulant

[0085] Where k0 is a constant. Based on the above relationship and experimental data, the optimal concentration of the coagulant can be determined to optimize the preparation process.

[0086] Embodiment 1:

[0087] Materials: chitosan 0.5 g / L, aluminum sulfate 1.0 g / L, pH 6.0, reaction time 30 minutes.

[0088] Results: The removal rate of suspended solids reached 92% and the removal rate of chromaticity was 85%.

[0089] Embodiment 2:

[0090] Materials: Sodium alginate 0.3 g / L, iron salt 1.2 g / L, pH 6.8, reaction time 25 minutes.

[0091] Results: The oil removal rate in water was 95%, and the COD removal rate was 88%.

[0092] 1. Water treatment and drinking water purification

[0093] Application Background:

[0094] During the purification process of urban drinking water, suspended matter, silt, organic matter and microorganisms in the water need to be removed.

[0095] Coagulants such as polyaluminium salts and iron salts used in traditional water treatment methods (such as flocculation and sedimentation) sometimes cause secondary pollution.

[0096] Application process:

[0097] Preparation of novel hydroxy coagulant aid: According to the above-mentioned preparation process, chitosan or sodium alginate is compounded with aluminum salt or iron salt to form a novel hydroxy coagulant aid.

[0098] Flocculation experiment: In water treatment, a certain amount of new hydroxyl coagulant is added to remove suspended matter, colloids and bacteria in the water through flocculation reaction.

[0099] Reaction optimization: By adjusting the concentration of the coagulant, pH value and reaction time, it can achieve efficient removal of pollutants in water in a short time.

[0100] Effect verification:

[0101] Experimental data show that after using the new hydroxyl coagulant, the removal rate of suspended matter in water can reach more than 95%, the chromaticity removal rate is 90%, and the E. coli removal rate reaches 99%.

[0102] Compared with traditional polyaluminium salts, the new coagulant aid can quickly form large-particle flocs in a shorter reaction time, has a faster sedimentation rate and higher reaction efficiency.

[0103] Application advantages:

[0104] Efficient flocculation: quickly remove suspended matter in water and reduce the dosage of flocculants.

[0105] Environmentally friendly: reduce the generation of harmful by-products and avoid heavy metal ion pollution.

[0106] 2. Wastewater treatment (such as industrial wastewater, urban sewage treatment)

[0107] Application Background:

[0108] Industrial wastewater and urban sewage often contain toxic and harmful substances, such as heavy metal ions, oil, acid and alkali substances and other pollutants. Traditional treatment methods are costly and the treatment effects are unstable.

[0109] Application process:

[0110] Addition of new coagulant aid: Design a reasonable coagulant aid concentration according to the characteristics of wastewater quality. The new hydroxy coagulant aid can remove grease, suspended matter, heavy metal ions, etc. in water through synergistic flocculation.

[0111] Treatment process: Add appropriate concentration of hydroxyl coagulant to the wastewater to promote the aggregation and sedimentation of pollutants, and then remove the pollutants through sedimentation, filtration and other methods.

[0112] Effect verification:

[0113] Experimental treatment of wastewater containing grease and heavy metal ions showed that the new coagulant can effectively remove grease (removal rate of 92%) and heavy metal ions (removal rate of 85%).

[0114] The experiment also showed that the use of new coagulant aids can reduce the chemical oxygen demand (COD) and total suspended solids (TSS) concentrations of wastewater and improve water quality.

[0115] Application advantages:

[0116] Wide adaptability: It can treat various types of wastewater, especially complex wastewater containing oil and heavy metal ions.

[0117] Low cost: By optimizing the concentration of coagulant aid and reaction conditions, the cost of wastewater treatment is reduced.

[0118] 3. Oilfield water injection

[0119] Application Background:

[0120] Suspended particles and impurities in oilfield injection water may cause equipment blockage and increase the difficulty of water reinjection, affecting oilfield production efficiency.

[0121] Application process:

[0122] Use of new hydroxy coagulant aid: In the process of oil field water injection, new hydroxy coagulant aid is used to remove suspended solids and particulate matter in the injection water.

[0123] Addition process: Add the new hydroxy coagulant into the water injection system to promote the sedimentation and flocculation of suspended matter and improve the water quality of the injection.

[0124] Effect verification:

[0125] Experiments show that the new coagulant aid can effectively remove suspended particles and colloidal substances in the water injection system and reduce the blockage of the water injection pipe.

[0126] The improvement of water quality for oilfield injection has increased injection efficiency and reduced the frequency of equipment maintenance.

[0127] Application advantages:

[0128] Improve water injection efficiency: remove suspended matter, reduce pipe blockage, and reduce maintenance costs.

[0129] Extend equipment life: Reduce corrosion and damage to equipment caused by sediments generated during oil field water injection.

[0130] 4. Aquaculture and wastewater reuse

[0131] Application Background:

[0132] In aquaculture, poor water quality can easily lead to problems such as slow fish growth and disease transmission, and effective water quality management measures are needed.

[0133] Application process:

[0134] Water purification: The new hydroxyl coagulant is used in aquaculture pond water treatment to remove plankton, organic matter and sediments in the water.

[0135] Wastewater reuse: By adding a new type of hydroxyl coagulant, pollutants in aquaculture wastewater can be settled and can be reused in aquaculture ponds or other water bodies after treatment.

[0136] Effect verification:

[0137] In aquaculture pond applications, the new coagulant can effectively remove organic matter, plankton and bacteria in the water, improve water quality and increase the transparency of the aquaculture environment.

[0138] In the wastewater reuse experiment, after the wastewater is treated, the pollutant removal rate in the water can reach more than 90%, and the quality of the reused water meets the requirements of aquaculture.

[0139] Application advantages:

[0140] Improve water quality: remove harmful substances in the water and improve the quality of the aquaculture environment.

[0141] Reusability: Treated water can be reused, saving water resources and reducing costs.

[0142] 5. Industrial waste gas treatment (such as dust removal and air purification)

[0143] Application Background:

[0144] In industrial production, waste gas (such as dust, volatile organic compounds, acidic gases, etc.) causes serious pollution and requires efficient treatment technology.

[0145] Application process:

[0146] Dust removal and gas purification: By adding a new type of hydroxyl coagulant during the exhaust gas purification process, harmful substances in the exhaust gas are removed through wet adsorption and flocculation.

[0147] Adsorption tower design: Add the new coagulant aid into the exhaust gas adsorption tower through the spray system, and use its efficient adsorption performance to remove particulate matter and harmful gases in the exhaust gas.

[0148] Effect verification:

[0149] In the waste gas treatment experiment, the new coagulant can effectively remove particulate matter and acidic gases in the waste gas, with a removal efficiency of more than 95%.

[0150] Through the combination of wet adsorption and flocculation, dust emissions are reduced and the air quality in the factory is improved.

[0151] Application advantages:

[0152] Efficient removal: effectively remove pollutants in exhaust gas and improve purification efficiency.

[0153] Save resources: Reduce dependence on traditional dust removers and chemical adsorbents, and reduce processing costs.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for producing a hydroxy coagulant aid, characterized in that: The steps include: S1. Material selection: Organic components: chitosan, sodium alginate biomass-based materials; Inorganic components: aluminum salts, iron salts, calcium salts, multivalent metal salts; S2. Dissolving metal salts: First, dissolve aluminum salts in an appropriate amount of water and adjust the pH value of the solution to 4.5-5.5 to ensure that the metal ions are completely dissolved; S3, dissolving organic matter: in another container, dissolving chitosan and sodium alginate in an acidic aqueous solution, and controlling the pH value at 5-6; S4. Synthesizing a complex: Mix the two solutions and slowly add an appropriate amount of alkaline solution under stirring, wherein the alkaline solution is a sodium hydroxide solution, and adjust the pH value to 6.5-7.5 to promote the complexation reaction between the metal ions and the organic matter; S5. Precipitation and separation of flocculants: After the reaction, the obtained composite hydroxy coagulant is separated by filtration, centrifugation and sedimentation to obtain the final product; S6. Drying and powdering: Dry the separated product at low temperature to obtain a powdered hydroxy coagulant.

2. A hydroxy coagulant aid production and preparation process according to claim 1, characterized in that: S1, material selection, in water with high heavy metal ion concentration, select iron salt as the inorganic group.

3. A hydroxy coagulant production process according to claim 2, characterized in that: In the step S2, the metal salt is dissolved. When the aluminum salt is dissolved, the solution temperature is controlled at 45° C.-50° C. and the solution is stirred at a medium speed of 300 rpm-500 rpm.

4. A hydroxy coagulant production process according to claim 3, characterized in that: The mixing temperature in the S4 and synthetic composite is controlled at 20°C-30°C.

5. A hydroxy coagulant production process according to claim 4, characterized in that: The precipitation and separation of S5 and flocculant takes 30-60 minutes, the filter mesh is 0.45 μm, and the centrifugal speed is 3000 rpm-5000 rpm.

6. A process for producing a hydroxy coagulant aid according to claim 5, characterized in that: It also includes the optimization of coagulant concentration, specifically determining the pollutant characteristics of different water qualities, determining the optimal concentration range through experiments, and predicting the impact of different concentrations on flocculation results.

7. A process for producing a hydroxy coagulant aid according to claim 6, characterized in that: Determine the pollutant characteristics of different water qualities by using water quality monitoring instruments and laboratory analysis to obtain the pollutant concentrations in water samples, including suspended matter, grease, dissolved organic matter, and heavy metal ions. At the same time, measure the pH value, turbidity, chemical oxygen demand, total suspended solids, and dissolved oxygen indicators of water samples to determine the specific type of water quality.

8. A process for producing a hydroxy coagulant aid according to claim 7, characterized in that: The optimal concentration range was determined through experiments, and multiple concentration gradients were designed for experiments. The intervals were gradually increased from low concentration to high concentration. During the experiment, the removal rate, sedimentation velocity, and particle size indicators at different concentrations were recorded.

9. A process for producing a hydroxy coagulant aid according to claim 8, characterized in that: Predict the effect of different concentrations on flocculation effect, establish a mathematical model based on experimental data, predict the flocculation effect at different concentrations, and apply it to actual process design. Data collection and analysis: collect key data in the experiment, removal rate, sedimentation rate, and floc size at different concentrations, perform regression analysis on these data, and establish a mathematical model between reaction rate and coagulant concentration. Commonly used models include the first-order reaction kinetic model: Where C is the pollutant concentration and k is the reaction rate constant.

10. An application of a hydroxy coagulant aid, characterized in that: Mainly used in water treatment and drinking water purification, industrial and urban sewage treatment.

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