Suspension material loaded with porous elemental sulfur and alkaline substance as well as preparation method and application of suspension material

Abstract

The invention relates to the technical field of sewage treatment, and discloses a porous elemental sulfur and alkaline substance loaded suspension material as well as a preparation method and application thereof. The suspension material is prepared from the following components in percentage by weight: 50 to 70 weight percent of elemental sulfur, 15 to 30 weight percent of a slow-release alkaline material, 3 to 8 weight percent of a foaming agent, 10 to 25 weight percent of a light material and 2 to 5 weight percent of a binder. Through the synergistic effect of the slow-release sulfur and the alkaline substance, continuous electron donors are provided for sulfur autotrophic denitrification, acidic substances generated by the reaction can be effectively neutralized, the pH value of the system is maintained within the optimal range of 6.5-8.0, and the problems that in traditional sulfur autotrophic denitrification, the pH fluctuation is large, and the denitrification efficiency is unstable are solved. The suspension material disclosed by the invention can be directly added into a heterotrophic denitrification unit or an anaerobic ammonia oxidation unit of a sewage treatment plant, so that the denitrification efficiency is improved, and an efficient, economical and sustainable technical scheme is provided for upgrading and reconstruction of a biological denitrification process of the sewage treatment plant.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a suspension material loaded with porous elemental sulfur and alkaline substances, and a preparation method and application thereof. Background Art

[0002] Biological denitrification is the core biochemical process of sewage denitrification. It mainly removes nitrate nitrogen and nitrite nitrogen by gradually reducing them to nitrogen gas through microbial mediation in anoxic environment. Traditional heterotrophic denitrification technology relies on organic matter as an electron donor, but the carbon-nitrogen ratio (C / N) of the influent of sewage treatment plants is generally low, which limits its denitrification activity. Therefore, it is necessary to continuously add exogenous carbon sources such as methanol and sodium acetate to maintain the denitrification process, which leads to high operating costs.

[0003] Existing studies have shown that the coupling of traditional heterotrophic denitrification technology and sulfur autotrophic denitrification has significant synergistic advantages. First, sulfur autotrophic denitrification uses elemental sulfur or other sulfides as electron donors, without the need for additional organic carbon sources, thereby avoiding the increased operating costs and potential pollution problems caused by the addition of external carbon sources in traditional heterotrophic denitrification. Secondly, the coupling system can achieve higher denitrification efficiency by optimizing the utilization of electron donors and acceptors, and the total nitrogen removal rate can reach 94.68% to 97.72%, which is significantly better than the single denitrification process. In addition, the amount of sludge produced during sulfur autotrophic denitrification is small, which can effectively reduce the cost of sludge treatment. At the same time, the synergistic effect of different microorganisms in the coupling system can improve the shock resistance and stability of the system, and realize resource recycling through resource recovery (such as precipitation recovery of elemental sulfur). In addition, the coupling process can also reduce the competition of microorganisms for substrates and further optimize the denitrification process.

[0004] Although the coupling technology of heterotrophic denitrification and sulfur autotrophic denitrification has significant advantages, it also has some shortcomings. First, a large amount of sulfate and acidic substances will be produced during the sulfur autotrophic denitrification process, which will lead to a decrease in the system pH, and additional alkalinity needs to be supplemented to maintain a suitable pH environment. Secondly, when elemental sulfur is used as an electron donor, its water solubility is extremely low, which limits the mass transfer rate and reaction efficiency, and small particles of sulfur may cause reactor blockage. In addition, when sulfide is used as an electron donor, high concentrations of sulfide will have a toxic inhibitory effect on microorganisms, and nitrite may accumulate during the reaction process, affecting the stability of the system and denitrification efficiency. Finally, the coupling process has high requirements for reaction conditions. Parameters such as pH, dissolved oxygen and hydraulic retention time need to be strictly controlled, otherwise it will affect the overall treatment effect. These limitations have limited the widespread application of this coupling technology to a certain extent.

[0005] This invention originates from the National Key R&D Program project "Research and Development and Integrated Demonstration of Urban Living Water-Saving Technology and Equipment" (2021YFC3201302). Summary of the invention

[0006] The purpose of the present invention is to provide a suspension material loaded with porous elemental sulfur and alkaline substances and a preparation method and application thereof based on the above technical problems.

[0007] In order to achieve the above object, the first aspect of the present invention provides a suspension material loaded with porous elemental sulfur and alkaline substances, wherein the suspension material comprises the following components in terms of weight percentage:

[0008] 50wt% to 70wt% of elemental sulfur, 15wt% to 30wt% of slow-release alkaline material, 3wt% to 8wt% of foaming agent, 10wt% to 25wt% of lightweight material, and 2wt% to 5wt% of binder;

[0009] The average particle size of the elemental sulfur is less than 100 μm; the average particle size of the sustained-release alkaline material is less than 50 μm.

[0010] The second aspect of the present invention provides a method for preparing the suspension material loaded with porous elemental sulfur and alkaline substances according to the first aspect of the present invention, the method comprising:

[0011] The elemental sulfur is crushed to an average particle size of less than 100 μm, and the magnesium oxide is crushed to an average particle size of less than 50 μm; the raw materials are weighed according to the ratio, mixed with water to obtain a material with a moisture content of 18-20%, granulated to obtain particles with an average particle size of 1.5-2 mm, naturally dried in the sun, heated for foaming, and cooled for solidification;

[0012] The conditions of the heating foaming treatment are as follows: nitrogen atmosphere, temperature of 60 to 150° C., and time of 10 to 30 minutes.

[0013] The third aspect of the present invention provides an application of a suspended material loaded with porous elemental sulfur and alkaline substances as described in the first aspect of the present invention in synergistic denitrification, wherein the suspended material loaded with porous elemental sulfur and alkaline substances at a concentration of 1 to 5 g / L is added to a heterotrophic denitrification unit or an anaerobic ammonia oxidation unit of a sewage treatment plant for treatment.

[0014] The suspension material loaded with porous elemental sulfur and alkaline substances provided by the present invention and its preparation method and application have at least the following beneficial effects:

[0015] (1) High efficiency denitrification and pH stability: The present invention not only provides a continuous electron donor for sulfur autotrophic denitrification through the synergistic effect of slow-release sulfur and alkaline substances, but also effectively neutralizes the acidic substances produced by the reaction, maintaining the system pH in the optimal range of 6.5-8.0, thereby solving the problems of large pH fluctuations and unstable denitrification efficiency in traditional sulfur autotrophic denitrification.

[0016] (2) Porous structure and high reactivity: The porous structure of the present invention significantly increases the specific surface area and reactivity of elemental sulfur, and enhances the efficiency of sulfur autotrophic denitrification. At the same time, the lightweight property makes the material easy to suspend in water, improves the mass transfer efficiency, and further optimizes the denitrification performance.

[0017] (3) Promote the formation of granular sludge: The porous structure and lightweight characteristics of the present invention provide a good attachment carrier for microorganisms, significantly promote the formation of granular sludge, and increase the concentration and activity of microorganisms; by coupling with traditional heterotrophic denitrification and anaerobic ammonium oxidation processes, the denitrification performance and operational stability of the system are further enhanced.

[0018] (4) Easy operation and economical efficiency: The material of the present invention can be directly added to the sewage biological denitrification treatment unit, which is easy to operate and has low operating costs. At the same time, the slow-release characteristics extend the service life of the material and further reduce the frequency of addition, which has significant economic and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of preparing a suspension material loaded with porous elemental sulfur and alkaline substances according to an embodiment of the present invention;

[0020] Figure 2 This is a diagram of the actual application form of the suspension material loaded with porous elemental sulfur and alkaline substances obtained in an embodiment of the present invention;

[0021] Figure 3 It is a cross-sectional view of the suspension material loaded with porous elemental sulfur and alkaline substances obtained in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0023] As mentioned above, the first aspect of the present invention provides a suspension material loaded with porous elemental sulfur and alkaline substances, wherein the suspension material comprises the following components in terms of weight percentage:

[0024] 50wt% to 70wt% of elemental sulfur, 15wt% to 30wt% of slow-release alkaline material, 3wt% to 8wt% of foaming agent, 10wt% to 25wt% of lightweight material, and 2wt% to 5wt% of binder;

[0025] The average particle size of the elemental sulfur is less than 100 μm; the average particle size of the sustained-release alkaline material is less than 50 μm.

[0026] Preferably, the sustained-release alkaline material is selected from at least one of magnesium oxide, calcium oxide, magnesium hydroxide and calcium hydroxide.

[0027] Further preferably, the foaming agent is sodium bicarbonate, ammonium bicarbonate or p-toluenesulfonyl hydrazide.

[0028] Preferably, the lightweight material is floating beads, expanded perlite or hollow glass microspheres.

[0029] More preferably, the binder is polyvinyl alcohol, polyvinyl acetate or silicate cement.

[0030] As mentioned above, the second aspect of the present invention provides a method for preparing the suspension material loaded with porous elemental sulfur and alkaline substances according to the first aspect of the present invention, the method comprising:

[0031] The elemental sulfur is crushed to an average particle size of less than 100 μm, and the magnesium oxide is crushed to an average particle size of less than 50 μm; the raw materials are weighed according to the ratio, mixed with water to obtain a material with a moisture content of 18-20%, granulated to obtain particles with an average particle size of 1.5-2 mm, naturally dried in the sun, heated for foaming, and cooled for solidification;

[0032] The conditions of the heating foaming treatment are as follows: nitrogen atmosphere, temperature of 120-160° C., and time of 10-30 min.

[0033] In the present invention, a slow-release sulfur suspension material with a porous structure is prepared by compounding a slow-release alkaline material with elemental sulfur, and adding a foaming agent and a lightweight material. In the material, elemental sulfur acts as an electron donor, and nitrate is reduced to nitrogen gas through sulfur autotrophic denitrification. At the same time, the slow-release alkaline material continuously neutralizes the acidic substances produced by the reaction, and maintains the system pH in the optimal range of 6.5-8.0. Its porous structure significantly increases the specific surface area and reaction activity of sulfur, and its lightweight characteristics make the material easy to suspend and enhance the mass transfer efficiency, while providing an attachment carrier for microorganisms to promote the formation of granular sludge. When applied, the material is directly added to the autotrophic denitrification or anaerobic ammonium oxidation unit, and an efficient and stable denitrification effect is achieved through the synergistic effect of sulfur autotrophic denitrification and anaerobic ammonium oxidation. In addition, the slow-release characteristics of the material extend the service life, and it has the advantages of simple operation, stable operation, low cost, etc., and is suitable for deep denitrification and low-carbon source wastewater treatment in sewage treatment.

[0034] As mentioned above, the third aspect of the present invention provides an application of a suspended material loaded with porous elemental sulfur and alkaline substances as described in the first aspect of the present invention in synergistic denitrification, wherein the suspended material loaded with porous elemental sulfur and alkaline substances at a concentration of 1 to 5 g / L is added to the heterotrophic denitrification unit or the anaerobic ammonia oxidation unit of the sewage treatment plant for treatment.

[0035] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, the raw materials are all commercially available.

[0036] Example 1

[0037] A suspension material loaded with porous elemental sulfur and alkaline substances, comprising the following components in weight percentage:

[0038] Elemental sulfur 60wt%, magnesium oxide 20wt%, sodium bicarbonate 5wt%, floating beads 10wt%, polyvinyl alcohol 5wt%.

[0039] A method for preparing a suspension material loaded with porous elemental sulfur and alkaline substances comprises (eg Figure 1 shown):

[0040] The elemental sulfur is crushed to an average particle size of less than 100 μm, and the magnesium oxide is crushed to an average particle size of less than 50 μm; the raw materials are weighed according to the ratio, mixed with water to obtain a material with a water content of 18%, granulated to obtain particles with an average particle size of 1.5 mm, naturally dried in the sun, heated and foamed for 30 minutes at a temperature of 140° C. in a nitrogen atmosphere, and cooled to obtain a suspension material A (such as Figure 2 and Figure 3 shown).

[0041] Example 2

[0042] A suspension material loaded with porous elemental sulfur and alkaline substances, comprising the following components in weight percentage:

[0043] Elemental sulfur 50wt%, magnesium oxide 30wt%, ammonium bicarbonate 5wt%, expanded perlite 10wt%, and silicate cement 5wt%.

[0044] A method for preparing a suspension material loaded with porous elemental sulfur and alkaline substances comprises (eg Figure 1 shown):

[0045] The elemental sulfur is crushed to an average particle size of less than 100 μm, and the calcium oxide is crushed to an average particle size of less than 50 μm; the raw materials are weighed according to the ratio, mixed with water to obtain a material with a moisture content of 20%, granulated to obtain particles with an average particle size of 2 mm, naturally dried in the sun, heated and foamed at 150° C. in a nitrogen atmosphere for 20 minutes, and cooled to obtain a suspension material B loaded with porous elemental sulfur and alkaline substances.

[0046] Example 3

[0047] A suspension material loaded with porous elemental sulfur and alkaline substances, comprising the following components in weight percentage:

[0048] Elemental sulfur 55wt%, calcium hydroxide 25wt%, sodium bicarbonate 6wt%, hollow glass microspheres 10wt%, polyvinyl alcohol 4wt%.

[0049] A method for preparing a suspension material loaded with porous elemental sulfur and alkaline substances comprises (eg Figure 1 shown):

[0050] The elemental sulfur is crushed to an average particle size of less than 100 μm, and the calcium hydroxide is crushed to an average particle size of less than 50 μm; the raw materials are weighed according to the ratio, mixed with water to obtain a material with a moisture content of 18%, granulated to obtain particles with an average particle size of 1.6 mm, naturally dried in the sun, heated and foamed in a nitrogen atmosphere at a temperature of 150° C. for 25 minutes, and cooled to obtain a suspended material C loaded with porous elemental sulfur and alkaline substances.

[0051] Application Example 1

[0052] The effective volume of the construction is 3m 3 The complete mixing reactor system was used to treat the sewage from the anoxic tank of a certain urban sewage treatment plant (see Table 1 for water quality). 1.5 g / L suspended material A was continuously added for sewage treatment. The system operation data was recorded for 30 consecutive days, and the effluent water quality results shown in Table 1 were obtained.

[0053] The parameters of the complete mixing reactor system are set as follows: the activated sludge concentration is 2 g / L, nitrogen is introduced through a microporous aeration device to adjust the dissolved oxygen concentration to 0.5 mg / L, the hydraulic retention time is 4 h, and the sludge return ratio is 50%.

[0054] Comparative application example 1

[0055] The method of Application Example 1 is followed, except that the suspension material A is not added, and the remaining steps and parameters are the same as those of Application Example 1.

[0056] Comparative Application Example 2

[0057] The method of Example 1 is followed, except that elemental sulfur with an average particle size of 1 mm is used to replace the suspension material A. The remaining steps and parameters are the same as those of Example 1.

[0058] Table 1

[0059]

[0060]

[0061] In Table 1, R1 is the effluent quality in Comparative Application Example 1, R2 is the effluent quality in Comparative Application Example 2, and R3 is the effluent quality in Application Example 1.

[0062] As can be seen from Table 1, compared with Comparative Application Example 1 and Comparative Application Example 2, the system of Application Example 1 of the present invention exhibits significant advantages in pollutant removal efficiency improvement and operational stability, as follows:

[0063] Nitrate nitrogen removal efficiency: The nitrate nitrogen removal efficiency in Application Example 1 of the present invention is increased by 21.1% compared with Comparative Application Example 1 and 8.6% compared with Comparative Example 2, and there is almost no nitrite accumulation phenomenon;

[0064] System stability: The pH fluctuation range of the system in Application Example 1 of the present invention is controlled within 0.8, and no obvious acidification phenomenon observed in Comparative Application Example 2 occurs;

[0065] Byproduct control: In the application example 1 of the present invention, the amount of hydrogen sulfide generated is 0.2 mg / L, and the concentration of sulfate byproducts is reduced by 59.6% compared with the comparative application example 2;

[0066] The results show that the suspended material A described in the embodiment of the present invention has a unique composite structure, which can effectively avoid the acidification risk and accumulation of sulfur metabolic byproducts in the traditional sulfur autotrophic process while enhancing the denitrification efficiency.

[0067] Application Example 2

[0068] An upflow anaerobic sludge blanket reactor system with an effective volume of 1m3 was used, and actual sludge digestion liquid was used as the treatment object (water quality characteristics are shown in Table 2). 1g / L suspended material B was continuously added, and the actual sludge digestion liquid was subjected to short-range nitrification anaerobic ammonia oxidation treatment. The system operation data was recorded for 30 consecutive days, and the effluent water quality results shown in Table 2 were obtained;

[0069] The parameters of the upflow anaerobic sludge blanket reactor system were set as follows: the sludge concentration was 3 g / L, the dissolved oxygen concentration was precisely controlled to be less than 0.2 mg / L by nitrogen microporous aeration, and the hydraulic retention time was 10 h.

[0070] Comparative Application Example 3

[0071] The method of Application Example 2 is followed, except that the suspension material B is not added, and the remaining steps and parameters are the same as those of Application Example 2.

[0072] Table 2

[0073]

[0074] In Table 2, R4 is the effluent quality in Comparative Application Example 3, and R5 is the effluent quality in Application Example 2.

[0075] As shown in Table 2, the introduction of suspended material B significantly improves the system performance, as follows:

[0076] Nitrate nitrogen effluent concentration: compared with the nitrate nitrogen effluent concentration of 36.9 mg / L in Application Example 3, the nitrate nitrogen effluent concentration in Application Example 2 of the present invention was 6.5 mg / L, a decrease of 82.4%;

[0077] System stability: The pH value fluctuation range of the system in Application Example 2 of the present invention is stable at 6.8-7.5, while the pH value fluctuation range of the system in Comparative Application Example 3 is 7.3-8.6. It can be seen that Application Example 2 of the present invention effectively avoids the common pH surge phenomenon in high ammonia nitrogen systems.

[0078] Application Example 3

[0079] The effective volume is 2m 3 The continuous flow moving bed biofilm reactor system was used to treat the secondary effluent of a certain urban sewage treatment plant (water quality parameters are shown in Table 3), and 2 g / L suspended material C was continuously added to perform deep denitrification treatment on the secondary effluent of the certain urban sewage treatment plant. The system operation data was recorded for 30 consecutive days, and the effluent water quality results shown in Table 3 were obtained;

[0080] The parameters of the continuous flow moving bed biofilm reactor system are set as follows: the inoculation source is the sulfur autotrophic denitrification sludge that has been domesticated for a long time in a certain urban sewage treatment plant, and the MLSS of the sulfur autotrophic denitrification sludge is 3g / L, and the proportion of sulfur oxidizing bacteria is >65%; the dissolved oxygen DO is maintained at <0.5mg / L through a nitrogen microporous aeration system; and the hydraulic retention time is controlled to 12h.

[0081] Comparative Application Example 4

[0082] The method of Application Example 3 is followed, except that step (1) is not performed, and in step (2), a commercially available ferrosulphide composite filler is used to replace the suspension material C. The remaining steps and parameters are the same as those of Application Example 3.

[0083] Table 3

[0084]

[0085] In Table 3, "influent water quality*" represents the water quality of the secondary effluent from a certain city sewage treatment plant, R1 represents the effluent water quality in the effluent water quality of comparative application example 4, and R2 represents the effluent water quality in application example 3.

[0086] It can be seen from Table 3 that the introduction of suspended material C significantly improves the system performance, as follows:

[0087] Denitrification efficiency: Compared with comparative application example 4, the denitrification efficiency of application example 3 of the present invention is reduced by 56.0%, and the nitrite nitrogen concentration of the effluent of application example 3 of the present invention is lower. Furthermore, the nitrate nitrogen concentration of the effluent in application example 3 of the present invention is stabilized at 1.1 mg / L, while the nitrate nitrogen concentration of the effluent in comparative application example 4 is 2.5 mg / L.

[0088] System stability: In the application example 3 of the present invention, the system pH is stably maintained at 6.7-7.5, while in the comparative application example 4, the system pH drops sharply (the lowest pH is 5.5), so that the microbial activity is inhibited;

[0089] Byproduct control: H in Application Example 3 of the present invention 2 The release amount of S is 0.2 mg / L, which is 87.5% lower than that of Comparative Example 4. 4 2- The generated amount is 69.6 mg / L, which is 22.7% lower than that of comparative application example 4;

[0090] The above results show that suspended material C successfully constructed an efficient and stable sulfur autotrophic denitrification microenvironment through its gradient structure design, providing a reliable technical option for the effluent of sewage treatment plants to meet the standards.

[0091] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A suspension material loaded with porous elemental sulfur and alkaline substances, characterized in that: The suspension material comprises the following components in terms of weight percentage: 50wt% to 70wt% of elemental sulfur, 15wt% to 30wt% of slow-release alkaline material, 3wt% to 8wt% of foaming agent, 10wt% to 25wt% of lightweight material, and 2wt% to 5wt% of binder; The average particle size of the elemental sulfur is less than 100 μm; the average particle size of the sustained-release alkaline material is less than 50 μm.

2. The suspension material according to claim 1, characterized in that: The sustained-release alkaline material is selected from at least one of magnesium oxide, calcium oxide, magnesium hydroxide and calcium hydroxide.

3. The suspension material according to claim 1 or 2, characterized in that: The foaming agent is sodium bicarbonate, ammonium bicarbonate or p-toluenesulfonyl hydrazide.

4. The suspension material according to claim 1 or 2, characterized in that: The lightweight material is floating beads, expanded perlite or hollow glass microspheres.

5. The suspension material according to claim 1 or 2, characterized in that: The binder is polyvinyl alcohol, polyvinyl acetate or silicate cement.

6. A method for preparing a suspension material loaded with porous elemental sulfur and alkaline substances as claimed in any one of claims 1 to 5, characterized in that: The method includes: The elemental sulfur is crushed to an average particle size of less than 100 μm, and the magnesium oxide is crushed to an average particle size of less than 50 μm; the raw materials are weighed according to the ratio, mixed with water to obtain a material with a moisture content of 18-20%, granulated to obtain particles with an average particle size of 1.5-2 mm, naturally dried in the sun, heated for foaming, and cooled for solidification; The conditions of the heating foaming treatment are as follows: nitrogen atmosphere, temperature of 120-160° C., and time of 10-30 min.

7. Use of a suspended material loaded with porous elemental sulfur and alkaline substances as claimed in any one of claims 1 to 5 in synergistic denitrification, characterized in that: The suspended material loaded with porous elemental sulfur and alkaline substances at a concentration of 1 to 5 g / L is added to the heterotrophic denitrification unit or anaerobic ammonia oxidation unit of the sewage treatment plant for treatment.

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