Method for reducing adding amount of flocculating agent in industrial wastewater treatment

Abstract

The invention discloses a method for reducing the dosage of a flocculating agent in industrial wastewater treatment, which comprises the following steps: treating industrial wastewater by using a continuous flow microreactor, respectively filling the industrial wastewater and a flocculating agent solution into an injector, adjusting the flow rate of an injection pump, simultaneously pumping the flocculating agent solution and the wastewater into a mixing cavity of a coagulation reactor, the coagulation reactor can be a two-channel impinging stream reactor or a multi-channel vortex flow reactor, and continuous coagulation treatment of the wastewater is achieved in the rapid mixing process of the industrial wastewater and the flocculant solution. The wastewater treatment cost is further reduced. The flocculating agent can be prevented from self-settling, the adding amount of the flocculating agent is remarkably reduced, and the size of coagulation equipment is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment, and in particular to a method for treating industrial wastewater through a microreactor so as to reduce the dosage of a flocculant. Background Art

[0002] Flocculation is a water treatment technology that has been used in industry for a long time. The factors that affect the flocculation effect mainly include internal factors and external factors. The internal factor is the interaction between the flocculant and the pollutant, and the influencing factors include the molecular weight, charge density and hydrophilicity of the flocculant. The external factor is the flow state of the flow field, and the influencing factors include the velocity, concentration gradient and micro-mixing degree of the fluid. At present, most of the coagulation reactors used in industry are intermittent reactors. Such reactors have problems such as low degree of automation, poor particle collision efficiency and easy self-sinking of water treatment agents, which affect the flocculation effect.

[0003] Compared with traditional kettle reactors, continuous flow microreactor mixing has many advantages. The first is the short mixing time. Due to the high inlet velocity, the time for multiple fluids to achieve homogeneous mixing can be shortened to 3 milliseconds. Secondly, by changing the flow rate ratio of the two inlet fluids, the saturation of the mixed solution can be easily controlled, which is particularly important for improving coagulation efficiency and reducing the amount of flocculant added. In addition, continuous flow microreactors are easy to achieve continuous operation, and large-scale production can be easily achieved by connecting multiple reactors in parallel. This parallel expansion method can effectively overcome the amplification effect of traditional reactors, which is conducive to the pilot scale-up and industrial application of coagulation reactors.

[0004] Since the continuous flow microreactor can control the degree of coagulation by adjusting the micro-mixing degree and supersaturation of the flow field, the use of a continuous flow microreactor as a coagulation reactor can significantly reduce the amount of flocculant added, avoid the self-settling of the flocculant, reduce the size of the coagulation equipment, and achieve continuous coagulation of industrial wastewater, thereby further reducing the cost of wastewater treatment. Summary of the invention

[0005] The purpose of the present invention is to provide a method for reducing the dosage of flocculants in the treatment of industrial wastewater. The method uses a continuous flow microreactor to treat industrial wastewater, and the industrial wastewater and the flocculant solution are respectively loaded into a syringe, and the flow rate of the injection pump is adjusted to simultaneously pump the flocculant solution and the wastewater into the mixing chamber of the coagulation reactor. The coagulation reactor can be a two-channel impinging flow reactor or a multi-channel vortex flow reactor. In the rapid mixing process of the industrial wastewater and the flocculant solution, the continuous coagulation treatment of the wastewater is achieved. Compared with traditional flocculation, this method can significantly reduce the dosage of flocculants, avoid the self-sinking of flocculants, reduce the size of coagulation equipment, achieve continuous coagulation of industrial wastewater, and further reduce the cost of wastewater treatment.

[0006] The method for reducing the dosage of flocculant in industrial wastewater treatment according to the present invention is carried out according to the following steps:

[0007] a. Dissolve the flocculant in water to prepare a flocculant solution with a concentration of 0.01-20 g / L, pour the wastewater with a concentration of 0.1-20 g / L into a beaker, and use hydrochloric acid or sodium hydroxide to adjust the pH value of the solution to 1.0-11.0;

[0008] b. The flocculant and wastewater in step a are respectively packed into two or four identical syringes in the continuous flow microreactor, and fixed to the same syringe pump through pipelines;

[0009] c. The flow rate of the syringe pump is controlled at 1-200 mL / min, and the solution in the syringe in step b is passed into the continuous flow microreactor. After the inside of the reactor is stabilized, the coagulated wastewater continuously flows out from the outlet of the continuous flow microreactor.

[0010] The continuous flow microreactor described in step b is an impinging flow coagulation reactor or a vortex flow coagulation reactor.

[0011] The method for reducing the dosage of flocculant in industrial wastewater treatment described in the present invention comprises the following steps: in the vortex flow coagulation reactor described in the method, each syringe is connected to an inlet end of the vortex flow coagulation reactor through the pipeline; there are four syringes, one for placing flocculant solution, one for placing industrial wastewater, and the other two for placing dilute acid solution;

[0012] In the impinging flow coagulation reactor, each syringe is connected to an inlet end of the impinging flow coagulation reactor through the pipeline; there are two syringes, one for placing flocculant solution and the other for placing industrial wastewater.

[0013] The coagulation reactor is a multi-channel vortex coagulator or an impinging flow coagulator, which can achieve rapid and continuous mixing of industrial wastewater and flocculant solution. The high-intensity mixing ensures that the solute reaches supersaturation instantly, achieving simultaneous precipitation of pollutants and flocculants, thereby improving flocculation efficiency and reducing flocculant dosage.

[0014] The present invention discloses a method for reducing the dosage of flocculants in industrial wastewater treatment. In the method, the continuous flow microreactor is an impingement flow coagulation reactor or a vortex flow coagulation reactor, and experiments are performed respectively:

[0015] The vortex flow coagulation reactor is used to avoid the self-sinking of flocculants and reduce the amount of flocculants added. The specific steps are as follows:

[0016] Using a vortex reactor as a mixer, 0.25 g / L of dye wastewater and 0.025-0.3 g / L of flocculant solution were respectively loaded into two 50 mL glass syringes, and the glass syringes were installed on a syringe pump. Two syringes for placing dilute acid solutions were fixed on another syringe pump. The flow rate of the syringe pump was adjusted to 15 mL / min, and the syringe pump was started to pump flocculant solution, dye wastewater and dilute acid solution into the mixing chamber of the vortex reactor to obtain optimized coagulation conditions. The experiment fixed the dye concentration C0=0.25 g / L, and the traditional flocculation and continuous flow coagulation methods were carried out under the same conditions, stirred for 5 minutes, and allowed to stand. The obtained mixed system was filtered with filter paper, and the absorbance in the filtrate was measured with an ultraviolet spectrophotometer to calculate the residual amount of the dye in the filtrate, and then the decolorization rate of the flocculant on the dye was calculated.

[0017] Figure 1 The effect of continuous flow coagulation and traditional kettle method on the decolorization rate of dyes in vortex flow coagulation reactor is shown in Figure 2. Figure 1 As shown in a, when the concentration of flocculant is in the range of 0.025-0.3 g / L, the dye chromaticity removal rate of wastewater treated by continuous flow coagulation is significantly higher than that of the traditional intermittent method. This is because the dye flocculation in a micro-reaction-limited environment is completely different from the traditional kettle method. The flocculant solution, dye wastewater and dilute acid solution collide at high speed in a small volume and spatially limited mixing zone, which strengthens the multiphase mass transfer process. In addition, during the high-speed collision of the four fluids, a strong turbulent area is formed in the mixing chamber to promote rapid micro-mixing, which is conducive to strengthening the collision and aggregation of flocs. Therefore, under the same decolorization rate, the continuous flow coagulation method can significantly reduce the amount of flocculant. Figure 1 b is the effect of flocculant dosage on dye adsorption in the vortex flow coagulation reactor. Compared with traditional flocculation, continuous flow coagulation obviously helps to increase the dye adsorption; for example, when the flocculant dosage is 0.025g / L, the adsorption capacity of wastewater treated by continuous flow coagulation is almost 1.52 times that of the traditional kettle method. The high adsorption capacity of continuous flow coagulation is due to the fact that this method can effectively inhibit flocculant agglomeration, and many active adsorption sites can be fully exposed on the surface of nano-adsorbent. This experimental data is consistent with the results of dye chromaticity removal rate.

[0018] The experiment of preventing flocculant from self-sinking and reducing flocculant dosage in impinging flow coagulation reactor is as follows:

[0019] Using an impinging stream reactor as a mixer, 0.25 g / L of dye wastewater and 0.025-0.5 g / L of flocculant solution were respectively loaded into two 50 mL glass syringes, the glass syringes were installed on a syringe pump, the syringe pump flow rate was adjusted to 20 mL / min, the syringe pump was started to pump the flocculant solution and dye wastewater into the impinging stream coagulator at the same time, the experiment fixed the dye concentration C0 = 0.2 g / L, the traditional flocculation and continuous flow coagulation methods were carried out under the same conditions, stirred for 5 minutes, and allowed to stand. The obtained mixed system was filtered with filter paper, and the absorbance in the filtrate was measured with an ultraviolet spectrophotometer to calculate the residual amount of dye in the filtrate, and then the decolorization rate of the dye by the flocculant was calculated.

[0020] Figure 2 The effect of continuous flow coagulation method in impinging stream reactor and traditional kettle method on dye decolorization rate, such as Figure 2 As shown in a, when the flocculant concentration is in the range of 0.025-0.5 g / L, the dye removal rate of wastewater treated by continuous flow coagulation is significantly higher than that of the traditional intermittent method. The high dye removal efficiency of the continuous flow coagulation method is due to the fact that this method can effectively avoid the self-settling of flocculants and reduce the amount of flocculants added. In summary, compared with traditional flocculation, the use of a dual-channel impinging flow reactor can also significantly reduce the amount of flocculants used. Figure 2 b is the effect of flocculant dosage on dye adsorption in the impinging stream reactor. Compared with traditional flocculation, continuous flow coagulation obviously helps to increase the dye adsorption; for example, when 0.5g / L Na2SO4 is added, the adsorption capacity of wastewater treated by continuous flow coagulation is almost 1.77 times that of the traditional kettle method. The high adsorption capacity of continuous flow coagulation is due to the fact that this method can effectively inhibit flocculant agglomeration, and many active adsorption sites can be fully exposed on the surface of nano-adsorbent. This experimental data is consistent with the results of dye chromaticity removal rate. Figure 2 cd is an electron microscope picture of nanoparticles flushed out by the continuous flow coagulation method and the traditional kettle method in the impinging stream reactor. It can be clearly seen from the figure that the continuous flow coagulation method obtains small-sized and narrow-diameter nanoparticles, while the traditional kettle method obtains nanoparticles with relatively large particle sizes. Therefore, the flocculation effect of the continuous flow coagulation method is better than that of the traditional kettle method.

[0021] The specific steps of the experiment of adjusting pH to broaden the flocculation platform in the vortex flow coagulation reactor are as follows:

[0022] Using a vortex reactor as a mixer, 0.25 g / L of dye wastewater and 0.025-0.5 g / L of flocculant solution were respectively placed into two 50 mL glass syringes, which were then mounted on a syringe pump. The two syringes for the dilute acid solution were fixed on another syringe pump. The syringe pump flow rate was adjusted to 15 mL / min, and the syringe pump was started to simultaneously pump the flocculant solution, dye wastewater, and dilute acid solution into the mixing chamber of the vortex reactor. The effect of flocculation pH on the flocculation effect was studied, and the optimized coagulation conditions were obtained. Figure 3 As shown, when the pH is 1.4, the best flocculation platform of the flocculant (removal rate is above 95%) is 0.075-0.1 g / L; when the pH is 1.7, the best flocculation platform of the flocculant becomes 0.075-0.2 g / L; when the pH is adjusted to 2.0, the best flocculation platform of the flocculant becomes 0.1-0.4 g / L.

[0023] The specific steps of adjusting pH to broaden the flocculation platform in the impinging stream coagulation reactor are as follows:

[0024] Using the impinging stream reactor as a mixer, 0.2 g / L of dye wastewater and 0.025-0.75 g / L of flocculant solution were respectively loaded into two 50 mL glass syringes, and the glass syringes were installed on the syringe pump. The flow rate of the syringe pump was adjusted to 20 mL / min. The syringe pump was started to pump the flocculant solution and dye wastewater into the mixing chamber of the impinging stream reactor at the same time. The effect of flocculation pH on the flocculation effect was studied, and the optimized coagulation conditions were obtained, such as Figure 4 As shown, when the pH is 1.7, the best flocculation platform of the flocculant (removal rate is above 95%) is 0.2-0.45 g / L; when the pH is 1.9, the best flocculation platform of the flocculant becomes 0.25-0.5 g / L; when the pH is adjusted to 2.1, the best flocculation platform of the flocculant becomes 0.25-0.75 g / L.

[0025] The specific steps of the experiment of changing the salt concentration to broaden the flocculation platform in the vortex flow coagulation reactor are as follows:

[0026] Using a vortex reactor as a mixer, 0.25 g / L of dye wastewater and 0.025-0.5 g / L of flocculant solution were respectively loaded into two 50 mL glass syringes, which were installed on a syringe pump. Two syringes for deionized water and brine of different concentrations were fixed on another syringe pump. The flow rate of the syringe pump was adjusted to 15 mL / min, and the syringe pump was started to simultaneously pump the flocculant solution, dye wastewater and dilute acid solution into the mixing chamber of the vortex reactor. The effect of different salt concentrations on the flocculation effect was studied to obtain the optimized coagulation conditions.

[0027] Depend on Figure 5It can be seen that in the vortex flow coagulation reactor, the flocculation window gradually widens with the increase of salt content. In salt-free wastewater, an excess of flocculant will result in an obvious re-stabilization phenomenon. It can be observed that with the increase of the amount of flocculant, the decolorization rate shows a rapid downward trend. This is because when the flocculant is added in excess, after the positive charge on the polymer chain segment neutralizes the negative charge of the dye, a large amount of positive charge remains on the molecular chain, which not only increases the hydrophilicity of the flocs, but also due to the Coulomb repulsion between the same charges, the flocs are redispersed in the solution. The flocculation platform can be significantly broadened by regulating the salt content of the flocculation system.

[0028] The experiment of changing the salt concentration to broaden the flocculation platform in the impinging stream coagulation reactor is as follows:

[0029] Using the impinging stream reactor as a mixer, 0.2 g / L of salt-containing dye wastewater and 0.025-0.8 g / L of flocculant solution were respectively loaded into two 50 mL glass syringes, which were installed on the syringe pump. The flow rate of the syringe pump was adjusted to 20 mL / min. The syringe pump was started to pump the flocculant solution and dye wastewater into the mixing chamber of the impinging stream reactor at the same time. The effect of different salt concentrations on the flocculation effect was studied to obtain the optimized coagulation conditions.

[0030] Depend on Figure 6 It can be seen that in the impinging flow coagulation reactor, with the increase of salt content, the flocculation platform gradually widens. In salt-free wastewater, an excess of flocculant will cause an obvious re-stabilization phenomenon. It can be observed that with the increase of flocculant dosage, the decolorization rate shows a rapid downward trend. This is because when the flocculant is added in excess, after the positive charge on the polymer chain segment neutralizes the negative charge of the dye, a large amount of positive charge remains on the molecular chain, which not only increases the hydrophilicity of the flocs, but also due to the Coulomb repulsion between the same charges, the flocs are redispersed in the solution. Figure 6 It can be seen that the flocculation window can be significantly widened by changing the salt concentration of the flocculation system.

[0031] The specific steps of the continuous coagulation treatment experiment of wastewater in the impinging flow coagulation reactor are as follows:

[0032] Using the impinging flow reactor as the mixing chamber, the flocculant solution and dye wastewater were respectively loaded into two 50mL glass syringes. The syringes were connected to the injection pumps through pipelines. By adjusting the flow rate of the injection pump, the reaction time of the flocculant and dye wastewater in the mixer was controlled to achieve rapid and continuous mixing of the wastewater and flocculant solution.

[0033] The method for reducing the amount of flocculant added in industrial wastewater treatment described in the present invention has beneficial effects: compared with traditional flocculation, the printing and dyeing wastewater treatment method of the present invention can achieve the same wastewater treatment effect while achieving continuous flow coagulation treatment. Not only can it avoid the self-settling of flocculants and reduce the amount of flocculants added, but it can also greatly reduce the size of coagulation equipment, thereby realizing continuous and efficient coagulation treatment of industrial wastewater and further reducing the cost of wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is an experimental effect diagram of the vortex flow coagulation reactor in the present invention to avoid the self-sinking of flocculants and reduce the dosage of flocculants.

[0035] Figure 2 This is an experimental effect diagram of preventing the self-sinking of flocculants and reducing the dosage of flocculants in the impinging flow coagulation reactor of the present invention.

[0036] Figure 3 This is an experimental effect diagram of adjusting pH to broaden the flocculation platform in a vortex flow coagulation reactor according to the present invention.

[0037] Figure 4 This is an experimental effect diagram of adjusting pH to broaden the flocculation platform in an impinging flow coagulation reactor according to the present invention.

[0038] Figure 5 This is an experimental effect diagram of changing the salt concentration in a vortex flow coagulation reactor to broaden the flocculation platform according to the present invention.

[0039] Figure 6 This is an experimental effect diagram of changing the salt concentration in the impinging flow coagulator to broaden the flocculation platform according to the present invention.

[0040] Figure 7 It is an experimental effect diagram of adjusting the flow rate to control the mixing time in the impinging flow coagulator of the present invention. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clear, the implementation modes of the present invention will be further described in detail below in conjunction with specific embodiments.

[0042] Example 1

[0043] The vortex flow coagulation reactor is used, and the specific steps are as follows:

[0044] a. Dissolve the flocculant in water to prepare a flocculant solution with a concentration of 0.01 g / L, pour the wastewater with a concentration of 0.1 g / L into a beaker, and use hydrochloric acid to adjust the pH value of the solution to 1.0;

[0045] b. The flocculant, wastewater and dilute acid solution in step a are respectively packed into four identical syringes in a continuous flow microreactor which is a vortex flow coagulation reactor, and fixed to the same injection pump through pipelines;

[0046] c. The flow rate of the injection pump is controlled at 15 mL / min. The solution in the syringe in step b is passed into the continuous flow microreactor vortex flow coagulation reactor. After the inside of the reactor is stabilized, the coagulated wastewater continuously flows out of the outlet of the continuous flow microreactor vortex flow coagulation reactor.

[0047] Example 2

[0048] Impinging flow coagulation reactor, the specific steps are as follows:

[0049] a. Dissolve the flocculant in water to prepare a flocculant solution with a concentration of 0.5 g / L, pour the wastewater with a concentration of 0.25 g / L into a beaker, and use hydrochloric acid to adjust the pH value of the solution to 5.0;

[0050] b. The flocculant and wastewater in step a are respectively packed into two identical syringes in a continuous flow microreactor which is an impinging flow coagulation reactor, and fixed to the same injection pump through pipelines;

[0051] c. The flow rate of the injection pump is controlled at 20 mL / min. The injection pump is started to pump the flocculant solution and the dye wastewater into the impinging flow coagulant at the same time. The solution in the syringe in step b is passed into the continuous flow microreactor. After the inside of the reactor is stabilized, the coagulated wastewater continuously flows out of the outlet of the continuous flow microreactor which is the impinging flow coagulant.

[0052] Example 3

[0053] The vortex flow coagulation reactor has the following specific steps:

[0054] a. Dissolve the flocculant in water to prepare a flocculant solution with a concentration of 5 g / L, pour the wastewater with a concentration of 5 g / L into a beaker, and use sodium hydroxide to adjust the pH value of the solution to 10;

[0055] b. The flocculant, wastewater and dilute acid solution in step a are respectively loaded into four identical syringes in a continuous flow microreactor vortex coagulation reactor, and fixed to the same syringe pump through pipelines;

[0056] c. The flow rate of the syringe pump is controlled at 10 mL / min, and the solution in the syringe in step b is passed into the continuous flow microreactor as a vortex flow coagulation reactor. After the inside of the reactor is stabilized, the coagulated wastewater continuously flows out of the outlet of the continuous flow microreactor as a vortex flow coagulation reactor.

[0057] Example 4

[0058] Impinging flow coagulation reactor, the specific steps are as follows:

[0059] a. Dissolve the flocculant in water to prepare a flocculant solution with a concentration of 10 g / L, pour the wastewater with a concentration of 15 g / L into a beaker, and use sodium hydroxide to adjust the pH value of the solution to 8.0;

[0060] b. The flocculant and wastewater in step a are respectively packed into two identical syringes in a continuous flow microreactor which is an impinging flow coagulation reactor, and fixed to the same injection pump through pipelines;

[0061] c. The flow rate of the syringe pump is controlled at 50 mL / min, and the solution in the syringe in step b is passed into the continuous flow microreactor as an impinging flow coagulation reactor. After the inside of the reactor is stabilized, the coagulated wastewater continuously flows out from the outlet of the continuous flow microreactor as an impinging flow coagulation reactor.

[0062] Example 5

[0063] The vortex flow coagulation reactor has the following specific steps:

[0064] a. Dissolve the flocculant in water to prepare a flocculant solution with a concentration of 15 g / L, pour the wastewater with a concentration of 20 g / L into a beaker, and use sodium hydroxide to adjust the pH value of the solution to 9.0;

[0065] b. The flocculant, wastewater and dilute acid solution in step a are respectively packed into four identical syringes in a continuous flow microreactor which is a vortex flow coagulation reactor, and fixed to the same injection pump through pipelines;

[0066] c. The flow rate of the syringe pump is controlled at 200 mL / min, and the solution in the syringe in step b is passed into the continuous flow microreactor as a vortex flow coagulation reactor. After the inside of the reactor is stabilized, the coagulated wastewater continuously flows out of the outlet of the continuous flow microreactor as a vortex flow coagulation reactor.

[0067] Example 6

[0068] Impinging flow coagulation reactor, the specific steps are as follows:

[0069] a. Dissolve the flocculant in water to prepare a flocculant solution with a concentration of 20 g / L, pour the wastewater with a concentration of 20 g / L into a beaker, and use sodium hydroxide to adjust the pH value of the solution to 11.0;

[0070] b. The flocculant and wastewater in step a are respectively packed into two identical syringes in a continuous flow microreactor which is an impinging flow coagulation reactor, and fixed to the same injection pump through pipelines;

[0071] c. The flow rate of the syringe pump is controlled at 100 mL / min, and the solution in the syringe in step b is passed into the continuous flow microreactor as an impinging flow coagulation reactor. After the inside of the reactor is stabilized, the coagulated wastewater continuously flows out from the outlet of the continuous flow microreactor as an impinging flow coagulation reactor.

[0072] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for reducing the amount of flocculant added in industrial wastewater treatment, characterized in that: Follow these steps: a. Dissolve the flocculant in water to prepare a flocculant solution with a concentration of 0.01-20 g / L, pour the wastewater with a concentration of 0.1-20 g / L into a beaker, and use hydrochloric acid or sodium hydroxide to adjust the pH value of the solution to 1.0-11.0; b. The flocculant and wastewater in step a are respectively packed into two or four identical syringes in the continuous flow microreactor, and fixed to the same syringe pump through pipelines; c. The flow rate of the syringe pump is controlled at 1-200 mL / min, and the solution in the syringe in step b is passed into the continuous flow microreactor. After the inside of the reactor is stabilized, the coagulated wastewater continuously flows out from the outlet of the continuous flow microreactor.

2. A method for reducing the amount of flocculant added in treating industrial wastewater according to claim 1, characterized in that: The continuous flow microreactor described in step b is an impinging flow coagulation reactor or a vortex flow coagulation reactor.

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