Method for strengthening coagulation and removing algae in drinking water plant

Abstract

The application discloses a method for strengthening coagulation and removing algae in a drinking water plant, and comprises the following steps: resin fluidization: pumping raw water containing algae into a resin column filled with 102 resin, and allowing the raw water containing algae to fully contact with 102 resin particles from bottom to top, so that the 102 resin particles are in a fluidized state; organic matter targeted adsorption: when the raw water containing algae passes through a fluidized bed layer, collision adsorption and targeted adsorption are performed between the raw water and the 102 particles in the fluidized state; coagulant positive action: after the targeted adsorption of the organic matter, the coagulant positively combines with the algae cells, so that the algae cells are more likely to be in an aggregated state; and algae cell strengthened coagulation. The application solves the problem that the prior art cannot achieve targeted adsorption on hydrophilic macromolecular organic matter, selectively removes organic matter which has a significant inhibitory effect on coagulation, realizes that the coagulant preferentially positively acts on the algae cells, and effectively strengthens the coagulation removal effect of the algae cells, and simultaneously reduces the generation risk of disinfection by-products.

Description

TECHNICAL FIELD

[0001] The present application relates to a drinking water treatment method, in particular to a method for removing algae by enhanced coagulation in a drinking water plant. BACKGROUND

[0002] With the intensification of global climate change and water body eutrophication, excessive proliferation of algae often leads to water bloom in water sources, which seriously threatens water ecological safety and drinking water safety. Water bloom not only includes algae cells, but also algae-derived organic matter produced during the growth and metabolism of algae cells. The presence of algae-derived organic matter can significantly inhibit coagulation efficiency, affect the treatment effect of water plant process, and increase the treatment cost of water plant. In addition, algae-derived organic matter is also an important precursor of disinfection by-products, which can cause many hazards to human health. Most drinking water plants use the coagulation-sedimentation-sand filtration-advanced oxidation-disinfection process for deep treatment. However, when the number of algae increases, it is difficult to achieve the removal effect by using only the above process, and it is impossible to effectively control the generation of disinfection by-products. Therefore, it is necessary to propose an efficient and safe algae removal technology for drinking water plants to improve the removal effect of algae, reduce the risk of disinfection by-product generation, and protect human drinking water health.

[0003] The currently studied enhanced coagulation algae removal technologies are pre-oxidation enhanced coagulation and activated carbon adsorption enhanced coagulation. However, both of them have the problem of no target selectivity for the object. Pre-oxidation (using potassium permanganate pre-oxidation or ozone pre-oxidation) has an oxidation effect on both algae cells and algae-derived organic matter, but excessive pre-oxidation can lead to the release of a large amount of intracellular algae-derived organic matter, increasing the risk of disinfection by-product generation. Similarly, activated carbon has no selectivity for adsorption of organic matter, and cannot achieve targeted adsorption of the part of organic matter that inhibits coagulation. It is easy to reach saturation and increase the cost of drinking water treatment. The existing document 1 (patent number CN 111620473A) discloses a water treatment method, which pre-treats raw water by a pre-ozone column, then coagulates and precipitates, and then post-treats by a post-ozone column. This patent uses ozone multiple times, but frequent use of ozone can easily lead to the rupture of algae cells and the release of a large amount of intracellular organic matter, increasing the risk of disinfection by-product generation. Document 2 (patent number CN 106242004A; Qu Fangshu. Membrane fouling characteristics and control in ultrafiltration treatment of high-algae water [D]. Harbin Institute of Technology, 2014) uses a combination of powdered activated carbon and polydimethyl diallyl ammonium chloride coagulation technology to achieve rapid removal of water disinfection by-product precursors and purification of water, which is a very effective water pretreatment method. However, the powdered activated carbon adsorption pretreatment in this patent mainly targets hydrophobic small molecular organic matter, and the adsorption effect on hydrophilic macromolecular organic matter is not obvious, and cannot achieve targeted adsorption. SUMMARY

[0004] The present application aims to provide a method for strengthening coagulation and removing algae in a drinking water plant, which solves the problem of the prior art that there is no target selectivity for the action object and the hydrophilic macromolecular organic matter cannot be targeted adsorbed. The specific resin particles in a fluidized state are used to selectively adsorb the organic matter in the algae-containing raw water, the organic matter which has a significant inhibitory effect on coagulation is removed by adsorption, the coagulant is preferentially positively acted on the algae cells, the coagulation removal effect of the algae cells is effectively strengthened, and the risk of generating disinfection by-products is also reduced.

[0005] In order to achieve the above-mentioned purpose, the present application provides a method for strengthening coagulation and removing algae in a drinking water plant, which comprises:

[0006] (1) resin fluidization: pumping the algae-containing raw water into a resin column filled with 102 resin, and allowing the algae-containing raw water to fully contact with the 102 resin particles from bottom to top, so that the 102 resin particles are in a fluidized state; the 102 resin particles are strong basic anion exchange resin with quaternary ammonium groups on the macroporous structure of styrene-divinylbenzene copolymer, the density is 1.05-1.10 g / ml, the particle size is 0.615-1.25 mm, and the internal pore size of the resin is 1.5-2.5 μm;

[0007] (2) targeted adsorption of organic matter: when the algae-containing raw water passes through the fluidized bed, the algae-containing raw water collides with and is adsorbed by the 102 particles in a fluidized state;

[0008] (3) positive action of coagulant: after the targeted adsorption of organic matter in step (2), the coagulant positively combines with the algae cells, so that the algae cells are more likely to be in an aggregated state; the components (which have been removed) in the algae-derived organic matter that inhibit coagulation no longer occupy the coagulant sites, and the coagulant can preferentially positively combine with the algae cells. The organic matter in the system that has an inhibitory effect on coagulation is (molecular weight of 3-100 KDa, high content of negative functional groups (such as carboxyl, functional groups that can occupy coagulant binding sites), and this part of the substance is mainly protein and acidic polysaccharide in algae-derived organic matter, which can enhance the adsorption of coagulant to the algae cells.

[0009] (4) strengthened coagulation of algae cells: under the same coagulant dosage, the strengthened coagulation of algae cells per unit algae cell occurs. The organic matter that has a promoting effect on coagulation helps the unit algae cell to obtain more coagulant under the same coagulant dosage.

[0010] Preferably, in step (1), the pumping speed of the algae-containing raw water is 4 L / min; and the moving speed of the 102 resin particles in a fluidized state is 0.2 m / s.

[0011] Preferably, in step (1), the mass of the 102 resin in the resin column and the volume of the resin column are 432 g:400 mL.

[0012] Preferably, in step (2), the 102 resin particles only adsorb and remove organic matter that has an inhibitory effect on coagulation.

[0013] More preferably, the organic matter includes proteins and acidic polysaccharides.

[0014] Preferably, it also includes algae removal and resin regeneration and reuse.

[0015] More preferably, in the algae removal, the coagulant dosage is 2 mg / L.

[0016] More preferably, the resin regeneration and reuse includes the following: after the 102 resin is saturated, the resin is first treated with a sodium hydroxide solution column, then treated with a hydrochloric acid solution column, and then washed with water.

[0017] More preferably, the concentration of the sodium hydroxide solution is 4%, and the column treatment speed is 3 BV / h.

[0018] More preferably, the concentration of the hydrochloric acid solution is 4%, and the column treatment speed is 2 BV / h.

[0019] The method for removing algae by enhanced coagulation in a drinking water plant according to the present application solves the problem of the prior art that there is no target selectivity for the object of action, and that it is impossible to achieve targeted adsorption of hydrophilic macromolecular organic matter, and has the following advantages:

[0020] 1. The resin material used in the present application is safe and non-toxic, and does not need to add chemical agents to the water body. Moreover, the resin after use can be recycled and reused, the process is simple, the cost is low, and the risk of producing disinfection by-products can be effectively reduced.

[0021] 2. The present application uses resin particles in a fluidized state to selectively target and adsorb organic matter in raw water containing algae. The selectivity only adsorbs the part of the organic matter that has a significant inhibitory effect on coagulation. At the same time, the amorphous channels formed between the fluidized resin particles can allow algae cells to pass through the dynamic channels between the resin particles smoothly and efficiently without clogging the resin.

[0022] 3. After the original inhibitory organic matter in the raw water containing algae is targeted and adsorbed, the coagulant can preferentially act on the surface of the algae cells, forming a positive effect of the coagulant. At the same time, the remaining macromolecular organic matter (organic matter that has a promoting effect on coagulation) in the raw water containing algae can promote the netting effect of the coagulant. Therefore, the coagulation efficiency of the algae cells can be doubled, the consumption of the coagulant can be reduced, and the treatment cost can be saved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Process flow chart of the method of the present application.

[0024] Figure 2 Efficiency chart of removing algae for Example 1 and Comparative Example 1 of the present application.

[0025] Figure 3 Comparison chart of dissolved organic carbon content before and after adsorption for Example 1 and Comparative Example 1 of the present application.

[0026] Figure 4 Infrared spectrum analysis chart after treatment for Example 1 and Comparative Example 1 of the present application.

[0027] Figure 5 Comparison chart of disinfection by-product concentration for Example 1 of the present application and prior art. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0029] The reagents involved in the embodiments and comparative examples of the present application are as follows:

[0030] 1. The manufacturer of 102 resin particles is Pansheng Technology; the model is ASD-102; and the specification is white opaque spherical particles.

[0031] 2. The manufacturer of 105 resin particles is Pansheng Technology; the model is ASD-102; and the specification is white opaque spherical particles.

[0032] 3. The manufacturer of the resin column is Shanghai Dibai Biological Technology Co., Ltd.; the model is L112305; and the specification is column inner diameter ф35 mm, column length 400 mm, and pressure resistance 2 bar.

[0033] Example 1

[0034] A method for removing algae by enhanced coagulation in a drinking water plant, as shown in Figure 1 the process flow chart of the method of the present application, the method comprises:

[0035] (1) resin fluidization: fluidizing the raw water containing algae (the number of algae in the raw water is 1×10 104 L / min, and the raw water containing algae was contacted with the 102 resin particles from bottom to top, so that the 102 resin particles were in a fluidized state similar to a fluidized bed, and the moving speed of the 102 resin particles in the fluidized bed was 0.2 m / s; wherein the 102 resin particles were strong basic anion exchange resin with quaternary ammonium groups on the macroporous structure of styrene-divinylbenzene copolymer, the density was 1.05-1.10 g / ml, the particle size was 0.615-1.25 mm, and the internal pore size of the resin was 1.5-2.5 μm.

[0036] (2) Targeted adsorption of organic matter: when the raw water containing algae passed through the fluidized bed, collision adsorption and targeted adsorption were carried out between the 102 particles in the fluidized state. The organic matter removed by the 102 resin particles was only the organic matter that inhibited coagulation, and the organic matter that inhibited coagulation was the organic matter with a molecular weight of 3-100 KDa and high content of negative functional groups (such as carboxyl, functional groups that occupied the coagulant binding sites), which was mainly protein and acidic polysaccharide in the algae-derived organic matter, and still existed in the system.

[0037] (3) Positive effect of coagulant: after the targeted adsorption of the 102 resin particles, the coagulation-inhibiting components in the algae-derived organic matter (which had been removed) no longer occupied the coagulant sites, the coagulant could be positively combined with the algae cells, and the coagulation-promoting organic matter in the system could enhance the adsorption of the coagulant to the algae cells, so that the algae cells were more likely to be in an aggregated state.

[0038] (4) Strengthened coagulation of algae cells: after the above steps, the coagulation-inhibiting organic matter had been removed by targeted adsorption, and the coagulation-promoting organic matter still existed in the system, which helped the unit algae cell to obtain more coagulant under the same coagulant dosage, and strengthened coagulation of the algae cells occurred.

[0039] (5) Algae removal: after coagulation, the raw water after the adsorption of the 102 resin particles was subjected to the conventional treatment process of a drinking water plant, i.e. air flotation-sand filtration-high level oxidation-disinfection, to completely remove the algae and disinfect; wherein the coagulant dosage was 2 mg / L, and the raw water after the adsorption of the 102 resin particles was used to remove the algae.

[0040] (6) Resin regeneration and reuse: after the 102 resin was saturated, 4% sodium hydroxide solution was passed through the column at a flow rate of 3 BV / h, then 4% hydrochloric acid solution was passed through the column at a flow rate of 2 BV / h, and finally tap water was used for cleaning, so that the 102 resin could be reused.

[0041] Comparative Example 1

[0042] A method for enhanced coagulation and algae removal in a drinking water plant is basically the same as in Example 1, except that:

[0043] In step (1), 102 resin is adjusted to 105 resin while maintaining the same mass; the moving speed of 105 resin particles in the fluidized bed is 0.1 m / s; wherein 105 resin particles are a weakly polar adsorption resin with a polystyrene skeleton as the main component and containing active groups, with a density of 1.25 to 1.35 g / ml, a particle size of 0.815 to 1.15 mm, and a pore size of 2 to 4 μm.

[0044] In step (2), the raw water containing algae undergoes collision adsorption and targeted adsorption with the fluidized 105 particles as it passes through the fluidized bed. The organic matter removed by the 105 resin particles is a component that has no significant impact on coagulation.

[0045] In step (3), after adsorption by 105 resin particles, the components that inhibit coagulation in the algal organic matter still exist.

[0046] In step (4), after the above processing steps, the organic matter that originally inhibited coagulation was not removed, and enhanced coagulation of algal cells could not occur.

[0047] In step (5), the raw water adsorbed by 102 resin particles is adjusted to the raw water adsorbed by 105 resin particles.

[0048] In step (6), after the resin is saturated with adsorption, it is first rinsed with tap water, and then regenerated with 2-3 BV methanol solution at a flow rate of 2 BV / h. After regeneration, the resin is rinsed with tap water until the effluent has no obvious methanol odor.

[0049] Experimental Example 1 compares and analyzes the method of the present invention with Comparative Example 1 and the prior art.

[0050] The same amount of raw water containing algae was treated using the methods of Example 1 of the present invention, Comparative Example 1, and the prior art.

[0051] like Figure 2 The figure shows the efficiency graphs for algae removal in Example 1 and Comparative Example 1 of the present invention. Figure 2 It can be seen that when the coagulant dosage is 2 mg / L, the final algae removal rate after adsorption using 102 resin particles in Example 1 of the present invention is 95.57%, while the final algae removal rate after adsorption using 105 fluidized resin particles in Comparative Example 1 is 7.53%, and the final algae removal rate of untreated algae-containing raw water is only 7.96% under the same coagulant dosage.

[0052] Meanwhile, to achieve an algae removal rate of over 95%, 5 mg / L of coagulant needs to be added to the untreated algae-containing raw water. The reason for this is that the organic matter removed by the 102 resin particles in Example 1 of this invention only contains organic matter that inhibits coagulation, including proteins and acidic polysaccharides, while organic matter that promotes coagulation remains in the system. Furthermore, the organic matter that promotes coagulation, at the same coagulant dosage, helps each algal cell receive more coagulant, resulting in enhanced coagulation of the algal cells and making them more prone to aggregation. Therefore, compared to untreated algae-containing raw water, this invention saves approximately 60% of the coagulant dosage.

[0053] like Figure 3 The figure shows a comparison of the dissolved organic carbon content before and after adsorption between Example 1 and Comparative Example 1 of the present invention. Figure 3 It can be seen that in Example 1 of this invention, after treating raw water containing algae with 102 resin particles, the concentration of dissolved organic carbon (DOC) decreased from 13.80 mg / L to 3.84 mg / L, with 72% of the organic matter (dissolved organic carbon) being adsorbed and removed. In Comparative Example 1, after treating raw water containing algae with 105 resin particles, the DOC concentration decreased from 13.80 mg / L to 8.39 mg / L, with 39% of the organic matter being adsorbed and removed. The reason for this difference is that the organic matter adsorbed and removed by the 105 resin particles consists of components that have no significant impact on coagulation; while the organic matter adsorbed and removed by the 102 resin particles is only organic matter that inhibits coagulation, including proteins and acidic polysaccharides, while organic matter that promotes coagulation remains in the system.

[0054] like Figure 4 The image shows the infrared spectra of Example 1 and Comparative Example 1 after processing. Figure 4 It can be seen that, compared with the original water containing algae, the water adsorbed by the 102 fluidized resin particles in Example 1 of this invention has a lower concentration at 1386 cm⁻¹. -1 The decrease in peak intensity at the point may be due to a reduction in the number of carboxyl groups (negatively charged functional groups) that inhibit coagulation. Simultaneously, amorphous channels form between the fluidized 102 resin particles, allowing algal cells to pass smoothly through and enter subsequent treatment steps. In contrast, after adsorption by 105 resin particles, the functional groups of the 105 resin and the algae-containing water showed no significant change. Components in the algal organic matter that inhibit coagulation still exist; for example, some small molecules (<3 kDa) and negatively charged functional groups occupy coagulant sites, preventing the coagulant from preferentially binding to algal cells.

[0055] like Figure 5The figure shows the disinfection by-product concentration comparison between the embodiment 1 of the present application and the prior art. From the figure, it can be seen that, compared with the potassium permanganate pre-oxidation enhanced coagulation and the ozone pre-oxidation enhanced coagulation in the background art, the resin targeted adsorption in the embodiment 1 of the present application can reduce the total amount of disinfection by-products by 30%, and the content of trichloroacetic acid and dichloroacetic acid which are more toxic to human body is reduced to 25%. Figure 5

[0056] When the algae removal rates of the embodiment 1 of the present application and the pre-oxidation (potassium permanganate or ozone) in the prior art are both 95%, the removal rate of the embodiment 1 of the present application on the dissolved organic carbon is 43.95%; while the removal rate of the potassium permanganate in the prior art on the dissolved organic carbon is 14.24%, and the removal rate of the ozone in the prior art on the dissolved organic carbon is 36.15%. Therefore, the efficiency of the embodiment 1 of the present application in removing organic matters is higher than that of the pre-oxidation.

[0057] Although the content of the present application has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation to the present application. After reading the above content, various modifications and substitutions to the present application will be apparent to those skilled in the art. Therefore, the protection scope of the present application should be defined by the appended claims.​

Claims

1. A method for enhanced coagulation and algae removal in a drinking water plant, characterized in that, The method includes: (1) Resin fluidization: Raw water containing algae is pumped into a resin column containing 102 resin. The raw water containing algae comes into full contact with the 102 resin particles from bottom to top, so that the 102 resin particles are in a fluidized state. The 102 resin particles are strong basic anion exchange resins with quaternary ammonium groups on macroporous styrene-divinylbenzene copolymers. The density is 1.05~1.10g / ml, the particle size is 0.615~1.25mm, and the internal pore size of the resin is 1.5~2.5μm. (2) Organic matter targeted adsorption: When raw water containing algae passes through the fluidized bed, it undergoes collision adsorption and targeted adsorption with the fluidized 102 particles; (3) Positive effect of coagulant: After the targeted adsorption of organic matter in step (2), the coagulant binds positively to algal cells, making it easier for algal cells to aggregate. (4) Enhanced coagulation by algal cells: Under the same amount of coagulant, enhanced coagulation of algal cells occurs per unit algal cell; In step (1), the pumping rate of the raw water containing algae is 4 L / min; the fluidized movement speed of the 102 resin particles is 0.2 m / s. In step (2), the 102 resin particles only adsorb and remove organic matter that has an inhibitory effect on coagulation; The organic matter includes proteins and acidic polysaccharides.

2. The method according to claim 1, characterized in that, In step (1), the mass ratio of 102 resin in the resin column containing 102 resin to the volume ratio of the resin column is 432g:400m.

3. The method according to claim 1, characterized in that, It also includes algae removal and resin regeneration and reuse.

4. The method according to claim 3, characterized in that, In the algae removal process, the coagulant dosage is 2 mg / L.

5. The method according to claim 3, characterized in that, The resin regeneration and reuse includes the following: 102 After the resin is saturated with adsorption, it is first treated by column chromatography with sodium hydroxide solution, then by column chromatography with hydrochloric acid solution, and finally washed with water.

6. The method according to claim 5, characterized in that, The sodium hydroxide solution has a concentration of 4% and a flow rate of 3 BV / h.

7. The method according to claim 5, characterized in that, The hydrochloric acid solution has a concentration of 4% and a flow rate of 2 BV / h.

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