A sulfur autotrophic denitrification and phosphorus removal packing material prepared at room temperature

Abstract

This invention relates to the field of water treatment technology, and more particularly to a sulfur autotrophic denitrification and phosphorus removal packing material prepared at room temperature. The packing material uses sulfur powder and iron-rich sludge as main raw materials, and is prepared at room temperature using a hydrogel encapsulation method to create S-Fe-Ca cross-linked three-dimensional network particles for nitrogen and phosphorus removal, avoiding the need for heating the sulfur powder. The iron-rich sludge contains a large amount of Fe, Ca, Si, and Al, as well as trace elements required for microbial growth. The cross-linking and coupling of sulfur powder and iron-rich sludge not only allows for simultaneous phosphorus adsorption but also serves as the basic framework of the packing material, improving its stability and promoting microbial growth. This solves the problems of poor long-term stability, slow reaction rate, and asynchronous phosphorus removal in sulfur autotrophic denitrification processes. The packing material has a simple preparation process, low energy consumption, is easy to fill, provides long-term slow release, and has a large number of phosphorus adsorption sites, making it suitable for simultaneous nitrogen and phosphorus removal from various low C / N ratio wastewaters, such as wastewater treatment plant effluent and groundwater.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology. Specifically, this invention relates to a sulfur autotrophic denitrification denitrification and phosphorus removal packing material prepared at room temperature. Background Technology

[0002] Urban wastewater treatment plant effluent has low levels of carbon sources available to microorganisms and high concentrations of nitrate nitrogen and phosphate. Indiscriminate reuse of this effluent not only leads to eutrophication but also poses a threat to biological health. Therefore, deep removal of nitrogen and phosphorus from effluent is extremely challenging.

[0003] Biochemical treatment technologies are widely used for deep nitrogen and phosphorus removal due to their high efficiency and low cost. Among them, sulfur autotrophic denitrification is an important technology that uses low-valence sulfur instead of carbon as an electron donor to achieve nitrogen removal through autotrophic denitrification. Elemental sulfur has advantages such as low cost, non-toxicity, stability, and ease of transportation, making it the most commonly used electron donor in sulfur autotrophic denitrification processes. Its reaction equation is: However, sulfur alone has low strength and slow microbial growth when used as a biological filler. Patent CN114291900A fixes and embeds sulfur autotrophic denitrifying bacteria liquid, biological sulfur, sodium thiosulfate and activated carbon, which solves the problem of difficult fluidization of biological sulfur, but cannot achieve simultaneous phosphorus removal.

[0004] Existing research has explored the use of iron-containing materials to accelerate reaction speed and achieve simultaneous nitrogen and phosphorus removal through iron-sulfur cycling. Patent CN115417500 A involves heating sulfur to a molten state, then adding ferrous sulfide, maifanite powder, and liquid polysulfide rubber, followed by stirring and granulation. This filler exhibits good compressive strength and nitrogen and phosphorus removal efficiency, but requires converting sulfur to a molten state at high temperatures before adding other materials, resulting in high energy consumption and a low safety factor. Patent CN107176702 B directly mixes pyrite, sulfur, and siderite particles and adds them uniformly to the reactor, avoiding high-temperature heating during filler preparation. However, this method suffers from low microbial utilization and poor nitrogen and phosphorus removal efficiency. Patent CN105923757 A incorporates iron filings into a sulfur / limestone combined packed bed reactor, achieving chemical phosphorus removal through a synergistic iron-sulfur autotrophic denitrification process. This method is easily utilized by microorganisms and has good phosphorus removal efficiency, but the powdered filler can easily cause impurities to be carried in the effluent. Patent CN116605986 A provides a solid-phase slow-release filler for sulfur autotrophic denitrification prepared at low temperature. It uses polyvinyl alcohol and sodium alginate as immobilization adhesives, sulfur powder, ferrous sulfide and calcium carbonate as main raw materials, supplemented with trace elements required for microbial growth. It has the effect of denitrification and phosphorus removal, but the preparation process involves low-temperature heating and the raw material composition is complex, resulting in high cost.

[0005] Therefore, addressing the shortcomings and defects of current sulfur autotrophic denitrification packing materials, developing a packing material with a simple preparation process, low energy consumption, resistance to long-term sewage immersion, and easy microbial utilization is crucial for improving sulfur autotrophic denitrification efficiency and achieving simultaneous nitrogen and phosphorus removal. Based on this, this invention introduces iron-rich sludge into sulfur powder, utilizing hydrogel at room temperature to form a three-dimensional network structure of S-Fe-Ca crosslinked nitrogen and phosphorus removal packing material through physicochemical interactions such as hydrogen bonding, van der Waals forces, and covalent bonds. This solves the problems of poor long-term stability, slow reaction rate, and asynchronous phosphorus removal in sulfur autotrophic denitrification processes, providing a highly efficient and low-consumption treatment method for deep nitrogen and phosphorus removal in wastewater effluent. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing technologies and provides a sulfur autotrophic denitrification and phosphorus removal packing material prepared at room temperature. It solves the problems of poor long-term stability, slow reaction rate, and asynchronous phosphorus removal in the sulfur autotrophic denitrification process, and exhibits highly efficient and stable nitrogen and phosphorus removal effects. Details are as follows:

[0007] This invention provides a sulfur autotrophic denitrification and phosphorus removal packing material, characterized in that the packing material is a three-dimensional network structure of S-Fe-Ca crosslinked particles, and the raw materials for preparation include sulfur powder, iron-rich sludge, hydrogel and crosslinking agent, which has a highly efficient and stable denitrification and phosphorus removal effect.

[0008] Preferably, the weight parts of sulfur powder, iron-rich sludge, and hydrogel in the raw materials are as follows: 60-70 parts sulfur powder, 30-40 parts iron-rich sludge, and 1-3 parts hydrogel.

[0009] Preferably, the iron-rich sludge in the raw material includes one or more of water treatment plant sludge and red mud.

[0010] Preferably, the hydrogel comprises one or more of sodium alginate, polyethylene glycol, polyvinyl alcohol, and polyacrylic acid.

[0011] Preferably, the crosslinking agent includes one or more of ferric chloride, calcium chloride, aluminum chloride, zinc oxide, and magnesium oxide.

[0012] Preferably, the filler has a particle size of 5-15 mm and a compressive strength of 0.45-1.20 MPa.

[0013] This invention provides a method for preparing sulfur autotrophic denitrification and phosphorus removal packing material at room temperature, comprising the following steps:

[0014] Step (1) Prepare the hydrogel suspension and quickly stir it evenly with a mixer;

[0015] Step (2) Add sulfur powder and iron-rich sludge to the well-stirred hydrogel suspension (1) and stir quickly with a mixer to obtain a mixed suspension.

[0016] Step (3) Prepare the crosslinking agent. Add the mixed suspension prepared in step (2) to the crosslinking agent using a peristaltic pump to obtain gel spheres.

[0017] After step (4) has cured for a period of time, remove the gel ball, wash it with deionized water 3 to 4 times, and let it air dry naturally.

[0018] Furthermore, the concentration of the hydrogel suspension in step (1) is 0.1-10%.

[0019] Furthermore, in steps (1) and (2), the mixing time of the mixer is 3 to 5 minutes, and the speed is controlled at 300 to 800 rpm.

[0020] Furthermore, in step (3), the concentration of the crosslinking agent is 1-10%, and the peristaltic pump speed is 10-100 rpm.

[0021] Furthermore, the curing time in step (4) is 4 to 24 hours.

[0022] This invention also provides an application device and method for the above-mentioned sulfur autotrophic denitrification and phosphorus removal packing. The reaction device consists of an empty tank water inlet layer, a support layer, and a packing layer from bottom to top. The empty tank water inlet layer and the support layer are separated by water distribution holes. The support layer is filled with 50mm pebbles to prevent clogging and ensure uniform water distribution. The packing layer holds the packing prepared above.

[0023] Furthermore, the reactor body is an organic glass column with a length of 550mm and a diameter of 70mm. It operates by continuously feeding water from the bottom. The water is injected into the reactor from the inlet through a peristaltic pump from the water tank. One inlet is set 15mm from the base, and four outlets are set on the column. The distance between two adjacent outlets is 100mm.

[0024] Furthermore, the water inlet adopts an upward flow method, with the inlet located on the lower side of the reactor and the outlet located on the upper side of the reactor.

[0025] Furthermore, when filling the packing layer, larger particles are placed at the bottom. The water flow velocity at the bottom inlet of the reactor is relatively fast, which can play a certain buffering role and prevent microorganisms from being washed out of the reactor by the water flow. At the same time, smaller and relatively regular-shaped packing materials are interspersed among the larger packing materials. On the one hand, this can better support the entire bed and make the entire bed more stable. On the other hand, it can increase the porosity of the bed, which is conducive to the removal of gas and provides more space for the growth of microorganisms.

[0026] Furthermore, the reactor is designed with an influent nitrate concentration of 15–25 mg / L, a phosphate concentration of 1–3 mg / L, and a pH of 7.0–8.0.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) High nitrogen removal efficiency and phosphorus removal effect: Compared with common sulfur autotrophic denitrification packing materials, the packing material prepared in this invention uses sulfur powder as the matrix, introduces iron-rich sludge with high specific surface area and porosity, and crosslinks S-Fe-Ca with hydrogel at room temperature to form a stable three-dimensional network structure packing material. The sulfur in the packing material will be slowly released into the water over a long period of time, which improves the mass transfer rate of sulfur autotrophic denitrification, thereby generating more H2O. + This promotes the exposure of adsorption sites for iron and calcium in the packing material, thereby increasing the phosphorus removal rate. The denitrification and phosphorus removal method described is not a simple combination of multiple substances, but rather achieves deep denitrification and accelerated phosphorus removal through cross-linking coupling reactions between elemental sulfur and iron and calcium ions.

[0029] (2) Excellent physical and biological properties: The Ca, Si and other elements contained in the iron-rich sludge can provide a stable skeleton for this packing material, increase its compressive strength, and make it resistant to long-term immersion in sewage. In addition, the packing material of this invention has a high specific surface area and porosity, and the surface has uniform raised grooves, which facilitates the biofilm accumulation of microorganisms.

[0030] (3) Waste resource utilization, realizing waste-to-waste transformation: The denitrification and phosphorus removal packing material prepared in this invention utilizes industrial waste such as sludge from water supply plants and aluminum smelting slag as iron-rich sludge, achieving low-cost process preparation while increasing electron transfer efficiency. The prepared packing material can be used for deep denitrification and phosphorus removal of low C / N wastewater, and is a new type of high-efficiency packing material that uses waste to transform waste.

[0031] (4) This application proposes a simple and easy-to-use method for preparing fillers: Compared with the existing high-temperature heating process, this invention uses hydrogel to prepare S-Fe-Ca crosslinked sulfur autotrophic denitrification denitrification and phosphorus removal filler at room temperature, which not only does not lose the performance of raw materials, but also solves the problem of powdered materials being difficult to separate and easy to clog during application. Attached Figure Description

[0032] Figure 1 The flowchart illustrates the preparation process of the sulfur autotrophic denitrification and phosphorus removal packing material with a three-dimensional network structure provided by this invention.

[0033] Figure 2 This is a schematic diagram of the solid-phase continuous flow reactor used for simultaneous nitrogen and phosphorus removal according to the present invention.

[0034] Figure 3 This is an electron microscope image of the packing material prepared in Example 1 of the present invention.

[0035] Figure 4 This is an electron microscope image of the filler material prepared in Example 2 of the present invention.

[0036] Figure 5The diagram shows the nitrate nitrogen removal effect of the packing material prepared in Examples 3 and 4 of this invention under different hydraulic residence times in the reactor.

[0037] Figure 6 The graph shows the phosphate removal effect of the packing materials prepared in Examples 3 and 4 of this invention under different hydraulic residence times in the reactor.

[0038] Figure 7 The graph shows the changes in sulfate concentration of the packing material prepared in Examples 3 and 4 of this invention under different hydraulic residence times in the reactor. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. However, the following embodiments are further illustrations of the present invention and are not intended to limit the scope of the invention.

[0040] Example 1:

[0041] This embodiment uses water treatment plant sludge as iron-rich sludge, and provides a method for preparing a sulfur autotrophic denitrification and phosphorus removal packing material with a three-dimensional network structure using water treatment plant sludge. The optimal conditions for packing material preparation were determined through single-factor experiments and response surface methodology. The preparation method includes the following steps:

[0042] (1) Prepare a 2.0% sodium alginate hydrogel suspension and stir it quickly and evenly with a mixer;

[0043] (2) After mixing sulfur powder and sludge powder from the water supply plant at a ratio of 1.75:1, add the mixture to the uniformly stirred sodium alginate hydrogel (1) and continue to stir it quickly with a mixer to obtain a mixed suspension.

[0044] (3) Prepare 1% FeCl3 crosslinking agent, and add the suspension prepared in step (2) dropwise into the crosslinking agent using a peristaltic pump to obtain gel spheres;

[0045] (4) After curing for 4 hours, the gel balls are taken out, washed with deionized water 3 to 4 times, and then air-dried to obtain the sulfur autotrophic denitrification and dephosphorization packing material with sulfur powder / water treatment plant sludge as the matrix.

[0046] The prepared sulfur powder / water treatment plant sludge-based autotrophic denitrification and phosphorus removal packing material exhibits good structural strength and porosity, with a compressive strength of 0.45 MPa and a porosity of 31.56%. Scanning electron microscopy analysis of the prepared packing material revealed... Figure 3 As shown, it has a large specific surface area, and most of the elemental sulfur is encapsulated by sodium alginate, exhibiting sulfur slow-release characteristics to a certain extent.

[0047] Example 2:

[0048] The packing material preparation method provided in this embodiment is the same as that in Example 1, except that the added iron-rich sludge is red mud. The sulfur-autotrophic denitrification and phosphorus removal packing material prepared in this example, with sulfur powder / red mud as the matrix, has good structural strength and porosity, with a compressive strength of 0.56 MPa and a porosity of 25.46%. Scanning electron microscopy analysis of the prepared packing material revealed... Figure 4 As shown, it has a large specific surface area, and most of the elemental sulfur is encapsulated by sodium alginate, exhibiting sulfur slow-release characteristics to a certain extent.

[0049] Example 3:

[0050] This embodiment provides an application of a sulfur autotrophic denitrification and phosphorus removal packing material prepared from water treatment plant sludge in a solid-phase continuous flow reactor. A schematic diagram of the reactor structure is shown below. Figure 2 As shown.

[0051] The reactor body is a 550mm long, 70mm diameter plexiglass column. It operates using a bottom-continuous water inlet system, with water injected from a tank via a peristaltic pump through the inlet. One inlet is located 15mm from the base, and four outlets are located on the other side of the column, with a 100mm spacing between adjacent outlets. The reaction device, from bottom to top, consists of an empty tank inlet layer, a support layer, and a packing layer. The empty tank inlet layer and the packing reaction zone are separated by water distribution holes. The support layer is filled with 50mm pebbles to prevent clogging and ensure even water distribution. The packing layer contains the prepared packing material. It is used for the advanced treatment of wastewater with a nitrate nitrogen concentration of 15–25 mg / L, a phosphate concentration of 1–3 mg / L, and an influent pH of 7–8. The packing material can sustainably release sulfur for over 200 days, improving the mass transfer rate of sulfur autotrophic denitrification and thus generating more H₂. + This promotes the exposure of adsorption sites for iron and calcium in the packing material, thereby increasing the phosphorus removal rate. Elemental sulfur interacts with iron and calcium ions through cross-linking reactions to achieve efficient nitrogen and phosphorus removal. The denitrification effect at different hydraulic retention times is shown below. Figure 5 As shown, the nitrate concentration in the effluent of the system of this invention is consistently below 0.5 mg / L, with a removal rate exceeding 98%. Figure 6 It can be seen that the phosphate concentration in the effluent of the system of this invention remains stable at around 0.2 mg / L. Figure 7 It can be seen that the sulfate concentration in the effluent of the system of the present invention is basically stable below 250 mg / L, which meets the requirements of the "Surface Water Environmental Quality Standard".

[0052] Example 4:

[0053] This embodiment provides an application of a sulfur autotrophic denitrification and phosphorus removal packing material prepared from red mud in a solid-phase continuous flow reactor. A schematic diagram of the reactor structure is shown below. Figure 2 As shown.

[0054] The reactor body is a 550mm long, 70mm diameter plexiglass column. It operates using a bottom-continuous water inlet system, with water injected from a tank via a peristaltic pump into the adsorption column through the inlet. One inlet is located 15mm from the base, and four outlets are located on the other side of the column, with a 100mm spacing between adjacent outlets. The reaction device, from bottom to top, consists of an empty tank inlet layer, a support layer, and a packing layer. The empty tank inlet layer and the packing reaction zone are separated by water distribution holes. The support layer is filled with 50mm pebbles to prevent clogging and ensure even water distribution. The packing layer contains the prepared packing material. It is used for the advanced treatment of low-carbon nitrogen-containing wastewater with a nitrate nitrogen concentration of 15–25 mg / L, a phosphate concentration of 1–3 mg / L, and an influent pH of 7–8. The packing material can sustainably release sulfur for over 200 days, improving the mass transfer rate of sulfur autotrophic denitrification and thus generating more H₂. + This promotes the exposure of adsorption sites for iron and calcium in the packing material, thereby increasing the phosphorus removal rate. Elemental sulfur interacts with iron and calcium ions through cross-linking reactions to achieve efficient nitrogen and phosphorus removal. The denitrification effect at different hydraulic retention times is shown below. Figure 5 As shown, the nitrate concentration in the effluent of the system of this invention is consistently below 0.5 mg / L, with a removal rate exceeding 95%. Figure 6 It can be seen that although the system of this invention experiences a brief phosphorus release process, the phosphate concentration in the effluent remains below 0.2 mg / L after stabilization. Figure 7 It can be seen that the sulfate concentration in the effluent of the system of the present invention is stable at below 250 mg / L, which meets the requirements of the "Surface Water Environmental Quality Standard".

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention in any way. Any modifications, equivalent substitutions, or alterations made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An ambient temperature prepared amorphous iron reinforced sulfur autotrophic denitrifying dephosphorization packing material, characterized in that, The filler is a S-Fe-Ca cross-linked three-dimensional network structure particle, raw materials include sulfur powder, iron-rich sludge, hydrogel and cross-linking agent, the preparation process does not need to heat and melt sulfur powder, and has high and stable simultaneous nitrogen and phosphorus removal effect.

2. The sulfur autotrophic denitrification and phosphorus removal filler prepared at room temperature according to claim 1, characterized in that, The weight parts of the sulfur powder, the iron-rich sludge and the hydrogel in the raw materials are as follows: 60-70 parts of sulfur powder, 30-40 parts of iron-rich sludge and 1-3 parts of hydrogel.

3. The sulfur autotrophic denitrification and phosphorus removal packing prepared at room temperature according to claim 1, characterized in that, The iron-rich sludge includes one or more of waterworks sludge and red mud.

4. The sulfur autotrophic denitrification and phosphorus removal packing prepared at room temperature according to claim 1, characterized in that, The hydrogel includes one or more of sodium alginate, polyethylene glycol, polyvinyl alcohol and polyacrylic acid.

5. The sulfur autotrophic denitrification and phosphorus removal packing prepared at room temperature according to claim 1, characterized in that, The cross-linking agent includes one or more of ferric chloride, calcium chloride, aluminum chloride, zinc oxide and magnesium oxide.

6. The sulfur autotrophic denitrification and phosphorus removal packing prepared at room temperature according to claim 1, characterized in that, The particle size of the filler is 5-15 mm, and the compressive strength is 0.45-1.20 MPa.

7. A method for preparing an amorphous iron reinforced sulfur autotrophic denitrifying dephosphorization filler hydrogel at room temperature, characterized in that, The preparation method includes the following steps: Step (1) configuring a hydrogel suspension, and uniformly stirring with a blender; Step (2) adding sulfur powder and iron-rich sludge into the uniformly stirred hydrogel suspension (1), and uniformly stirring with a blender to obtain a mixed suspension; Step (3) configuring a cross-linking agent, and adding the mixed suspension prepared in step (2) into the cross-linking agent by using a peristaltic pump to obtain a gel ball; Step (4) taking out the gel ball after solidification, washing with deionized water for 3-4 times, and naturally air-drying.

8. The process for the preparation of the sulfur autotrophic denitrifying dephosphorization packing at room temperature according to claim 7, characterized by that, The concentration of the hydrogel suspension in step (1) is 0.1-10%.

9. The process for the preparation of the sulfur autotrophic denitrifying dephosphorization packing at room temperature according to claim 7, characterized by that, The concentration of the cross-linking agent in step (3) is 1-10%, and the rotation speed of the peristaltic pump is 10-100 rpm.

10. The process for the preparation of the sulfur autotrophic denitrifying dephosphorization packing at room temperature according to claim 7, characterized by that, The solidification time in step (4) is 4-24 h.

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