A method for simultaneous denitrification and desulfurization without additional sulfur source for realizing recovery of elemental sulfur

Abstract

The present invention provides a method for synchronous denitrification and desulfurization without adding an external sulfur source to achieve the recovery of elemental sulfur, belonging to the technical field of wastewater treatment. The method is realized by using a dedicated reaction device for sulfate reduction - synchronous denitrification and desulfurization - elemental sulfur recovery. The device is autotrophic for denitrification without adding an external sulfur source. In the reactor, the floating of elemental sulfur is achieved by controlling the particle size of elemental sulfur, i.e., the upward gas flow in the reactor, and the collection of elemental sulfur is realized through a partition plate and a microfiltration membrane framework at the top. Moreover, the dedicated device operates stably, has a high denitrification and desulfurization efficiency, a low sludge yield, and can control the sulfur form in the elemental sulfur state and achieve recycling. It can not only solve the problem of difficult treatment of ammonia nitrogen and sulfate in landfill leachate, but also recycle the generated elemental sulfur.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a synchronous denitrification and desulfurization method for realizing elemental sulfur recovery without adding an external sulfur source. Background Art

[0002] In recent years, with the increase in urban garbage discharge, more and more landfill leachate has been produced. Landfill leachate is an extremely complex and highly polluted liquid that contains high concentrations of biodegradable and non-biodegradable compounds, including ammonia nitrogen, sulfate and other substances. This has become a major problem in the removal of landfill leachate.

[0003] Landfill leachate is often treated with short-range denitrification / short-range nitrification + anaerobic ammonium oxidation process, but due to NO 3- Due to the limitation of anaerobic ammonium oxidation, the total nitrogen removal rate of anaerobic ammonium oxidation generally does not exceed 89%. The addition of organic matter will enhance heterotrophic denitrification, which has an adverse effect on the anaerobic ammonium oxidation process. Therefore, the autotrophic denitrification combined with anaerobic ammonium oxidation process has been favored recently.

[0004] Sulfur autotrophic denitrification is used to treat NO3 produced by anaerobic ammonium oxidation due to its high efficiency and economy. - NO3 - Reduction to NO2 - , providing substrate for anaerobic ammonium oxidation. And because sulfur autotrophic denitrifying bacteria are chemoautotrophic bacteria, they do not need to add external carbon sources, so that anaerobic ammonium oxidizing bacteria will not be inhibited by heterotrophic bacteria. In addition, sulfur autotrophic denitrifying bacteria and anaerobic ammonium oxidizing bacteria have similar ecological niches and can achieve good symbiosis. Because of their slow growth rate, they can reduce sludge production. Therefore, it is possible to consider combining the two to achieve deeper denitrification. For example, patent CN106396098A discloses a sulfur autotrophic denitrification and denitrification reaction device, the main reactor of which is divided into four parts from bottom to top, namely, an inlet mixing zone, a sulfur autotrophic denitrification zone, an anaerobic ammonium oxidation zone and an outlet zone. The sulfur autotrophic denitrification and denitrification reaction device is used to carry out simultaneous denitrification and desulfurization of high-salinity wastewater. This method can achieve S in high-salinity wastewater in one reactor. 2- 、NO2 - and NH4 + , and accumulates elemental sulfur. This method has good treatment effect, simple operation, and can recycle elemental sulfur. However, sulfur autotrophic denitrification will produce a large amount of sulfate and elemental sulfur. When the sulfate content is high, it will accelerate the formation of methylmercury, change the original ecological regulation function, and have a significant impact on aquatic organisms and human health. It is reported that when the sulfate content is higher than 250 mg / L, it will cause intestinal diseases such as diarrhea. Therefore, the removal of sulfate has become another problem that needs to be solved in the process.

[0005] Sulfate reduction is the reduction of sulfate to sulfide by sulfate-reducing bacteria using hydrogen or organic matter as an electron donor. Since landfill leachate contains a large amount of organic matter, it is feasible to use sulfate reduction to remove sulfate from landfill leachate. Patent CN113716690A discloses a sulfur autotrophic denitrification deep nitrogen removal device using sulfate in water as a sulfur source. Its filter tower includes a sulfate reduction zone at the lower part and a sulfur autotrophic denitrification zone at the upper part. Using this device for deep nitrogen removal of wastewater can achieve sulfur autotrophic denitrification deep nitrogen removal without an external sulfur source, saving resources, maximizing the utilization rate of the sulfur source, and reducing operating costs. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for synchronous nitrogen and sulfur removal without an external sulfur source that can recover elemental sulfur in view of the deficiencies of the prior art. This method is realized by using a dedicated reaction device for sulfate reduction - synchronous nitrogen and sulfur removal - elemental sulfur recovery. The device operates stably, can achieve deep nitrogen and sulfur removal without an external sulfur source, has a low sludge yield, and can control the sulfur form in the elemental sulfur state and realize its recovery and utilization.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] On the one hand, a reaction device for sulfate reduction - synchronous nitrogen and sulfur removal - elemental sulfur recovery, the main part of its main reactor is successively a sulfate reduction zone 1, a sulfur autotrophic denitrification coupled anaerobic ammonium oxidation reaction zone (synchronous nitrogen and sulfur removal zone) 2, and an elemental sulfur recovery zone 3 from bottom to top. An inlet zone 14 is provided at the bottom of the sulfate reduction zone 1, and an outlet zone 15 is provided at the top of the elemental sulfur recovery zone 3; an air outlet 10 is provided at the top of the main reactor, and a nitrogen pipeline 9 is provided at the bottom. The entire reactor is wrapped with a light-shielding and heat-insulating layer; among them,

[0009] The sulfate reduction zone 1 and the synchronous nitrogen and sulfur removal zone 2 are separated by a partition board I with slender pores; the synchronous nitrogen and sulfur removal zone 2 and the elemental sulfur recovery zone 3 are separated by a partition board II with uniformly distributed frustum-shaped pores, and iron beads 13 are placed in the pores;

[0010] A pH on-line monitoring device and an acid-base dosing device a are provided in the middle of the sulfate reduction zone 1; when the pH exceeds the set range, an acid source or a base source is automatically added;

[0011] The synchronous nitrogen and sulfur removal zone 2 is divided into a sulfur autotrophic denitrification zone and an anaerobic ammonium oxidation reaction zone from bottom to top. An inlet B is provided at the bottom of the synchronous nitrogen and sulfur removal zone 2, a pH on-line monitoring device, an acid-base dosing device b, and a DO on-line monitoring device 5 are provided in the middle, and a reflux device 4 and a sampling port 12 are provided at the top; the reflux device 4 connects the synchronous nitrogen and sulfur removal zone 2 with the inlet zone 14; when the pH exceeds the set range, an acid source or a base source is automatically added;

[0012] At the top of the elemental sulfur recovery area 3, there is a mixed cellulose membrane 7, in the middle there is a slag discharge outlet 8, and at the center of the partition plate (II) there is a slag removal plate 6; the elemental sulfur is intercepted through the mixed cellulose membrane 7; there are two slag removal plates 6, and during slag removal, the two plates can rotate and scrape simultaneously from the clockwise and counterclockwise angles and are discharged through the slag discharge outlet 8;

[0013] At the bottom of the water inlet area 14, there is a water distributor 11 and a water inlet A;

[0014] The water outlet area 15 is provided with a water outlet 16, and the water outlet is 2 - 3 cm away from the top of the water outlet area 15.

[0015] Furthermore, the height - diameter ratio of the main reactor is 5 - 6:1, and the height ratio of the elemental sulfur recovery area 3, the synchronous denitrification and desulfurization area 2, and the sulfate reduction area 1 in the main part is 1:3.9 - 4.5:6 - 7; preferably, the height ratio of the elemental sulfur recovery area 3, the synchronous denitrification and desulfurization area 2, and the sulfate reduction area 1 is 1:4:6.5.

[0016] Furthermore, the pore diameter of the partition plate I is < 0.5 cm, and the thickness is > 3 cm; preferably, the pore diameter of the partition plate I is 0.4 cm and the thickness is 5 cm.

[0017] Furthermore, the lower - end diameter of the pore of the partition plate II is < 0.5 cm, the upper - end diameter is 0.8 - 1 cm, the thickness is 1.5 - 2.5 cm, and the iron beads 13 placed in the pore have a diameter of 0.5 - 0.6 cm; preferably, the lower - end diameter of the pore of the partition plate II is 0.35 cm, the upper - end diameter is 0.9 cm, the thickness is 2 cm, and the iron beads 13 placed in the pore have a diameter of 0.55 cm. During the operation of the reactor, the iron beads will be lifted by the upward water flow. By controlling the upward flow velocity ≤ 0.5 m / h, the iron beads can always be stable in the pore. When the water inlet stops, the iron beads will continue to settle, preventing the elemental sulfur on the partition plate from falling into the synchronous denitrification and desulfurization area.

[0018] Furthermore, the slag removal plate 6 is fixed at the center of the partition plate I and contains two baffle plates. During slag removal, the two baffle plates move from the other side of the outlet towards the slag discharge outlet 8 for slag discharge; the slag discharge outlet 8 can be freely opened and closed. It is opened when slag discharge is carried out and closed again when slag removal is completed.

[0019] Furthermore, the pore diameter of the mixed cellulose membrane 7 is 0.1 - 0.2 μm; the mixed cellulose membrane 7 is prepared by mixing oxidized cellulose, ethyl cellulose, and nano - titanium dioxide with a solvent to form a casting solution, and then prepared by the phase inversion method; the pore diameter of the mixed cellulose membrane 7 is 0.1 - 0.2 μm. The mixed cellulose membrane has a good interception effect in the aqueous system and has characteristics such as low adsorption, which can prevent elemental sulfur from flowing into the water outlet area and achieve better interception of elemental sulfur.

[0020] Furthermore, the mass ratio of the oxidized cellulose, ethyl cellulose, and nano-titanium dioxide is 10:2-5:0.1-0.5; preferably, the mass ratio of the oxidized cellulose, ethyl cellulose, and nano-titanium dioxide is 1:3:0.2.

[0021] On the other hand, a method for synchronous denitrification and desulfurization to achieve elemental sulfur recovery without an external sulfur source is carried out using the above reaction device for sulfate reduction-synchronous denitrification and desulfurization-elemental sulfur recovery.

[0022] The method for synchronous denitrification and desulfurization to achieve elemental sulfur recovery without an external sulfur source includes the following steps:

[0023] S1. Before water inlet, open the valve of the nitrogen pipeline 9 to remove oxygen.

[0024] S2. Inoculate the sulfate reduction area 1 and the synchronous denitrification and desulfurization area 2 with inoculants and cultivate them.

[0025] S3. The landfill leachate is introduced into the water inlet area 14 through the water inlet A, and the landfill leachate pretreated by nitrification is introduced into the synchronous denitrification and desulfurization area 2 through the water inlet B. The water flow is from bottom to top. The effluent from the synchronous denitrification and desulfurization area 2 is refluxed to the upper end of the water inlet area 14 through the reflux device 4, mixed with the landfill leachate from the water inlet area 14, and then flows into the sulfate reduction area 1, and then enters the synchronous denitrification and desulfurization area 2; the hydraulic retention time in the synchronous denitrification and desulfurization area 2 ≤ 1 h.

[0026] S4. Turn on the pH on-line monitoring device and the DO on-line monitoring device 5. When the pH or DO exceeds the set range, the acid source or alkali source will be automatically added or the valve of the nitrogen gas tank will be opened to adjust the pH and DO to the set range.

[0027] S5. After the landfill leachate reacts in the synchronous denitrification and desulfurization area 2, it enters the elemental sulfur recovery area 3. After running for a period of time, the elemental sulfur is intercepted by the mixed cellulose membrane 7, the effluent from the elemental sulfur recovery area 3 enters the water outlet area 15, and the nitrogen gas generated during the reaction process is discharged through the top gas outlet 10.

[0028] Furthermore, in step (2), the sulfate reduction area 1 is inoculated with sulfate-reducing bacteria, and its mixed liquor volatile suspended solids concentration (MLVSS) is controlled ≥ 12 g / L.

[0029] Furthermore, in step (2), after the sulfur autotrophic denitrification area and the anaerobic ammonium oxidation reaction area in the synchronous denitrification and desulfurization area 2 are inoculated with sulfur autotrophic denitrifying bacteria and anaerobic ammonium oxidizing bacteria respectively, the MLVSS is controlled at 6-7 g / L and 2-3 g / L respectively.

[0030] Further, in step (2), the hydraulic retention time is 40 min. Controlling the diameter of the elemental sulfur produced to be less than 1 μm facilitates the elemental sulfur to rise with the water flow to the elemental sulfur recovery area under the hydraulic agitation provided by the influent water.

[0031] Further, in step (3), the ammonia nitrogen concentration of the landfill leachate introduced through inlet A ≤ 2000 mg / L, NO3 - / SO4 2- <0.1, organic matter / SO4 2- > 3, the DO content is less than 0.1 mg / L, and the SO4 2- concentration ≥ 4000 mg / L. After the reactor is successfully started, the main functional bacteria are Desulfobacteraceae.

[0032] Further, in step (3), the NO3 of the nitrification-pretreated landfill leachate introduced through inlet B - ≥ 1300 mg / L, and the sulfate concentration ≥ 1000 mg / L. After the reactor is successfully started, Thiobacillus and Candidatus Knenenia are dominant in the reaction zone.

[0033] Further, in step (3), for the wastewater entering the simultaneous denitrification and desulfurization zone 2 from the sulfate reduction zone 1, NH4 + / SO4 2- is controlled at 0.52 - 0.73, and NH4 + / NO3 - in the simultaneous denitrification and desulfurization reaction zone 2 is 0.7 - 0.9.

[0034] Further, in step (3), the influent flow rate ratio of inlets A and B is 1:1 - 3; preferably, the influent flow rate ratio of inlets A and B is 1:2. Under reflux, the amount of sulfide required in the reaction zone is satisfied.

[0035] Further, in step (3), the reflux ratio of the simultaneous denitrification and desulfurization zone 2 is 10 - 20.

[0036] Further, in step (4), the pH set value of the sulfate reduction zone 1 is 7.1 - 8.4; the pH set range of the simultaneous denitrification and desulfurization zone 2 is 7.0 - 7.5, and the DO set value is 0.2 mg / L.

[0037] Further, the operating temperature of the device is 30 - 32 °C.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The present invention provides a reactor for sulfate reduction - simultaneous denitrification and desulfurization - elemental sulfur recovery, which realizes the completion of sulfate reduction, simultaneous denitrification and desulfurization, and elemental sulfur recovery in a single reactor. Using this device to treat landfill leachate can simultaneously remove ammonia nitrogen, sulfate, and organic matter from the landfill leachate, and can also realize the recovery of elemental sulfur;

[0040] (2) The present invention uses a device for sulfate reduction - simultaneous denitrification and desulfurization - elemental sulfur recovery to treat landfill leachate, controls the HRT of the simultaneous denitrification and desulfurization reaction zone within 1 h, controls the diameter of the generated elemental sulfur to be less than 1 μm, and uses the nitrogen gas generated in the simultaneous denitrification and desulfurization zone and the agitation caused by the influent to prevent the elemental sulfur from settling, and allows it to flow to the elemental sulfur recovery zone along with the water flow. Different from removing elemental sulfur by flocculation precipitation, this technology makes full use of the nitrogen gas generated by the reaction itself, reduces subsequent costs, and has certain economic benefits;

[0041] (3) In the device for sulfate reduction - simultaneous denitrification and desulfurization - elemental sulfur recovery of the present invention, the partition between the sulfate reduction zone and the simultaneous denitrification and desulfurization zone is a slender partition, which realizes effective stratification in a single reactor and does not affect the rising water flow at the same time; the partition between the simultaneous denitrification and desulfurization zone and the elemental sulfur recovery zone is a partition with frustum - shaped holes, and iron beads are placed in the pore channels. The iron beads will be lifted by the rising water flow but can always remain stable in the pore channels. When the water inlet stops, the iron beads will continue to settle, preventing the elemental sulfur on the partition from falling into the simultaneous denitrification and desulfurization zone, thereby improving the retention of elemental sulfur, enhancing the wastewater treatment effect, ensuring the stable treatment efficiency of landfill leachate, and having a high denitrification and desulfurization efficiency;

[0042] (4) The mixed cellulose membrane of the present invention is a microfiltration membrane, which has good retention effect in an aqueous system, and has characteristics such as good mechanical strength, strong thermal stability, and low adsorption. It can prevent elemental sulfur from flowing into the effluent area, achieve better retention of elemental sulfur, ensure the stable treatment efficiency of landfill leachate, and have a high denitrification and desulfurization efficiency. Brief Description of the Drawings

[0043] Figure 1 is a schematic diagram of the device for sulfate reduction - simultaneous denitrification and desulfurization - elemental sulfur recovery of the present invention; in the figure, sulfate reduction zone 1; simultaneous denitrification and desulfurization zone 2; elemental sulfur recovery zone 3; reflux device 4; DO on - line monitoring device 5; slag removal plate 6; mixed cellulose membrane 7; slag discharge outlet 8; nitrogen pipeline 9; gas outlet 10; water distributor 11; sampling port 12; partition I with slender pore channels; partition II with uniformly distributed frustum - shaped pore channels; influent area 14; effluent area 15; water outlet 16;

[0044] Figure 2 is a schematic diagram of the partition II with uniformly distributed frustum - shaped pore channels of the present invention; in the figure, iron beads 13. Detailed Embodiments

[0045] The following non-limiting examples can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way. The following content is merely an exemplary illustration of the scope claimed by the present invention. Those skilled in the art can make various changes and modifications to the invention of the present invention based on the disclosed content, and it should also fall within the scope claimed by the present invention.

[0046] The present invention will be further described below by way of specific examples. All chemical reagents used in the embodiments of the present invention are obtained through conventional commercial channels unless otherwise specified.

[0047] Example 1

[0048] A reaction device for sulfate reduction - simultaneous denitrification and desulfurization - elemental sulfur recovery (such as Figure 1 ), the main part of the main reactor is successively a sulfate reduction zone 1, a simultaneous denitrification and desulfurization zone 2, and an elemental sulfur recovery zone 3 from bottom to top. An inlet zone 14 is provided at the bottom of the sulfate reduction zone 1, and an outlet zone 15 is provided at the top of the elemental sulfur recovery zone 3; an air outlet 10 is provided at the top of the main reactor, and a nitrogen pipeline 9 is provided at the bottom;

[0049] The sulfate reduction zone 1 and the simultaneous denitrification and desulfurization zone 2 are separated by a partition I. The partition I has slender pore channels with a pore diameter of 0.4 cm and a thickness of 5 cm; the simultaneous denitrification and desulfurization zone 2 and the elemental sulfur recovery zone 3 are separated by a partition II. The partition II is evenly distributed with frustum-shaped pore channels. The lower end diameter of the pore channels is 0.35 cm, the upper end diameter is 0.9 cm, and the thickness is 2 cm. And iron beads 13 (such as Figure 2 ) with a diameter of 0.55 cm are provided in the pore channels; the rising flow rate is controlled at 0.4 m / h;

[0050] A pH on-line monitoring device and an acid-base dosing device a are provided in the middle of the sulfate reduction zone 1; when the pH exceeds the range of 7.1 - 8.4, an acid source or a base source is automatically added;

[0051] The simultaneous denitrification and desulfurization zone 2 is divided into a sulfur autotrophic denitrification zone and an anaerobic ammonium oxidation reaction zone from bottom to top. An inlet B is provided at the bottom of the simultaneous denitrification and desulfurization zone 2. A pH on-line monitoring device, an acid-base dosing device b, and a DO on-line monitoring device 5 are provided in the middle. A reflux device 4 and a sampling port 12 are provided at the top; the reflux device 4 connects the simultaneous denitrification and desulfurization zone 2 with the inlet zone 14; when the pH exceeds the range of 7.0 - 7.5, DO > 0.2 mg / L, or the nitrogen tank valve is opened to adjust the pH and DO to the specified range;

[0052] At the top of the elemental sulfur recovery area 3, there is a mixed cellulose membrane 7, a slag discharge outlet 8 is arranged in the middle, and a slag removal plate 6 is arranged at the center of the partition plate (II); the elemental sulfur is intercepted through the mixed cellulose membrane 7; there are two slag removal plates 6, and during slag removal, the two plates can rotate and scrape simultaneously from the clockwise and counterclockwise angles and are discharged through the slag discharge outlet 8;

[0053] At the bottom of the water inlet area 14, there is a water distributor 11 and a water inlet A;

[0054] The water outlet area 15 is provided with a water outlet 16, and the water outlet is 2 - 3 cm away from the top of the water outlet area 15.

[0055] The height - to - diameter ratio of the main reactor is 6:1, and the height ratio of the elemental sulfur recovery area 3, the synchronous denitrification and desulfurization area 2, and the sulfate reduction area 1 in the main part is 1:4:6.5.

[0056] The mixed cellulose membrane is prepared by mixing oxidized cellulose, ethyl cellulose, and nano - titanium dioxide with a mass ratio of 10:3:0.2, adding 2 mass times of dimethylformamide, stirring evenly at 70 °C to obtain a casting solution, and forming a microfiltration membrane by the phase inversion method, with an average pore diameter of 0.16 μm.

[0057] A synchronous denitrification and desulfurization method for realizing elemental sulfur recovery without an external sulfur source is realized by the above - mentioned reaction device for sulfate reduction - synchronous denitrification and desulfurization - elemental sulfur recovery, and includes the following steps:

[0058] (1) Before water inlet, open the valve of the nitrogen gas pipeline 9 for de - oxygenation;

[0059] (2) Inoculate sulfate - reducing bacteria in the sulfate reduction area 1, control its MLVSS = 15 g / L, after inoculating sulfur autotrophic denitrifying bacteria and anaerobic ammonium - oxidizing bacteria in the sulfur autotrophic denitrification area and the anaerobic ammonium - oxidation reaction area of the synchronous denitrification and desulfurization area 2 respectively, control the MLVSS to be about 6.7 g / L and 2.3 g / L respectively for cultivation;

[0060] (3) Open the water inlet A and the water inlet B, and introduce landfill leachate and nitrified - pretreated landfill leachate into the water inlet A and B respectively at a flow rate ratio of 1:2. The water flow is from bottom to top. The water outlet of the synchronous denitrification and desulfurization area 2 flows back to the upper end of the water inlet area 14 through the reflux device 4, mixes with the landfill leachate in the water inlet area 14, then flows into the sulfate reduction area 1, and then enters the synchronous denitrification and desulfurization area 2;

[0061] (4) Open the pH on - line monitoring device and the DO on - line monitoring device 5. When the pH exceeds the range of 7.1 - 8.4 or the DO exceeds 2 mg / L, the acid source or alkali source will be automatically added or the valve of the nitrogen gas tank will be opened to adjust the pH and DO;

[0062] (5) After the landfill leachate reacts in the simultaneous denitrification and desulfurization zone 2, it enters the elemental sulfur recovery zone 3. After operating for a period of time, the elemental sulfur is intercepted by the mixed cellulose membrane 7, and the effluent from the elemental sulfur recovery zone 3 enters the effluent zone. The nitrogen gas generated during the reaction process is discharged through the top gas outlet 10.

[0063] The ammonia nitrogen concentration of the landfill leachate introduced through the inlet A is 1860 mg / L, and NO3 - / SO4 2- = 0.08, organic matter / SO4 2- = 4, the DO content is 0.08 mg / L, and the SO4 2- concentration is 4250 mg / L; the NO3 - concentration of the nitrification-pretreated landfill leachate introduced through the inlet B is 1382 mg / L, and the sulfate concentration is 1057 mg / L; the sulfide concentration of the landfill leachate entering the simultaneous denitrification and desulfurization zone is 130 mg / L in terms of S, and NO2 - is 70 mg / L in terms of N, and the N / S concentration ratio is 0.54.

[0064] The device operates at 30°C, and the hydraulic retention time of the simultaneous denitrification and desulfurization zone 2 is controlled to be 40 min. It operates under these conditions for 20 days.

[0065] Example 2

[0066] The difference from Example 1 is that the hydraulic retention time of the simultaneous denitrification and desulfurization zone 2 is 1 h.

[0067] Example 3

[0068] The difference from Example 1 is that the lower end diameter of the pore channel on the partition plate II is 0.45 cm, the upper end diameter is 1 cm, the thickness is 2 cm, and the diameter of the iron beads 13 is 0.6 cm.

[0069] Example 4

[0070] The difference from Example 1 is that the lower end diameter of the pore channel on the partition plate II is 0.3 cm, the upper end diameter is 0.8 cm, the thickness is 2 cm, and the diameter of the iron beads 13 is 0.5 cm.

[0071] Comparative Example 1

[0072] The difference from Example 1 is that the hydraulic retention time of the simultaneous denitrification and desulfurization reaction zone 2 is 2 h.

[0073] Comparative Example 2

[0074] The difference from Example 1 is that no iron beads are provided in the pore channels of the partition plate II.

[0075] Comparative Example 3

[0076] The difference from Example 1 is that the lower end diameter of the pore channel on Partition II is 0.35 cm, the upper end diameter is 0.7 cm, the thickness is 2 cm, and the diameter of the iron beads 13 is 0.4 cm.

[0077] Comparative Example 4

[0078] The difference from Example 1 is that the lower end diameter of the pore channel on Partition II is 0.35 cm, the upper end diameter is 1.1 cm, the thickness is 2 cm, and the diameter of the iron beads 13 is 0.7 cm.

[0079] Comparative Example 5

[0080] The difference from Example 1 is that the mixed cellulose membrane is prepared by adding 2 mass times of dimethylformamide to a mixture of 10:0.2 of oxidized cellulose and nano-titanium dioxide, stirring evenly at 70 °C to obtain a casting solution, and using the phase inversion method.

[0081] Comparative Example 6

[0082] The difference from Example 1 is that the mixed cellulose membrane is prepared by adding 2 mass times of dimethylformamide to a mixture of 10:0.2 of ethyl cellulose and nano-titanium dioxide, stirring evenly at 70 °C to obtain a casting solution, and using the phase inversion method.

[0083] The treatment results after the device runs for 20 days are shown in the following table.

[0084]

[0085] As shown in the table, when the method described in Example 1 runs for 0 - 20 days, the SO4 2- , NO2 - concentrations in the effluent are low, and the sulfide and NO2 -The high removal rate indicates that the method for simultaneous denitrification and desulfurization without additional sulfur source for realizing the recovery of elemental sulfur according to the present invention has excellent simultaneous sulfur and nitrogen removal effect, and the formation rate of elemental sulfur reaches more than 90%, which can efficiently recover elemental sulfur. In Comparative Example 1, the hydraulic retention time in the simultaneous denitrification and desulfurization zone is higher than 1 h. Although the denitrification and desulfurization efficiency is slightly higher than that in Example 1, the formation rate of elemental sulfur is significantly lower than that in Example 1. It can be seen that controlling the hydraulic retention time in the simultaneous denitrification and desulfurization zone within 1 h, so as to control the diameter of the generated elemental sulfur to be less than 1 μm, is beneficial to realize the upward movement of elemental sulfur with the water flow to the elemental sulfur recovery zone under the hydraulic agitation provided by the influent, and can improve the recovery of elemental sulfur. In Comparative Example 2, no iron beads are arranged in the pore channels of the partition plate II between the simultaneous denitrification and desulfurization zone and the elemental sulfur recovery zone. In Comparative Examples 3 and 4, the pore channel size and the iron bead size are not within the preferred range of the present invention. Not only the flow rate of the wastewater is affected, but also the effluent quality and the formation rate of elemental sulfur are significantly reduced compared with Example 1. It can be seen that the simultaneous denitrification and desulfurization zone and the elemental sulfur recovery zone are separated by a partition plate with uniformly distributed frustum-shaped pore channels, and appropriate-sized iron beads are placed in the pore channels to prevent the slipping of elemental sulfur when the water inlet stops, so as to realize the efficient recovery of elemental sulfur and ensure the high efficiency of denitrification and desulfurization of landfill leachate. The mixed cellulose membranes in Comparative Examples 5 and 6 do not contain ethyl cellulose, and the effluent quality and the formation rate of elemental sulfur are lower than those in Example 1. It can be seen that the mixed cellulose membrane provided by the present invention has good retention effect in the aqueous system, high sulfur and nitrogen removal efficiency, and characteristics such as low adsorption, which can avoid the inflow of elemental sulfur into the effluent zone and realize better retention of elemental sulfur.

[0086] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A reaction device for sulfate reduction - simultaneous denitrification and desulfurization - elemental sulfur recovery, characterized in that, The main part of the main reactor is, from bottom to top, a sulfate reduction zone (1), a simultaneous denitrification and desulfurization zone (2), and an elemental sulfur recovery zone (3). At the bottom of the sulfate reduction zone (1) is an inlet zone (14), and at the top of the elemental sulfur recovery zone (3) is an outlet zone (15). At the top of the main reactor is an air outlet (10), and at the bottom is a nitrogen pipeline (9). The entire reactor is wrapped with a light-shielding and heat-insulating layer. Among them, the sulfate reduction zone (1) and the simultaneous denitrification and desulfurization zone (2) are separated by a partition board (I) with slender pores; the simultaneous denitrification and desulfurization zone (2) and the elemental sulfur recovery zone (3) are separated by a partition board (II) with uniformly distributed frustum-shaped pores, and iron beads (13) are placed in the pores; in the middle of the sulfate reduction zone (1) are a pH on-line monitoring device and an acid-base dosing device (a); when the pH exceeds the set range, an acid source or a base source is automatically added; the simultaneous denitrification and desulfurization zone (2) is divided into a sulfur autotrophic denitrification zone and an anaerobic ammonium oxidation reaction zone from bottom to top. At the bottom of the simultaneous denitrification and desulfurization zone (2) is an inlet (B), in the middle are a pH on-line monitoring device, an acid-base dosing device (b), and a DO on-line monitoring device (5), and at the top are a reflux device (4) and a sampling port (12). The reflux device (4) connects the simultaneous denitrification and desulfurization zone (2) with the inlet zone (14). When the pH on-line monitoring device and the acid-base dosing device (b) detect that the pH exceeds the set range, an acid source or a base source is automatically added; at the top of the elemental sulfur recovery zone (3) is a mixed cellulose membrane (7), in the middle is a slag discharge outlet (8), and at the center of the partition board (II) is a slag removal plate (6). Elemental sulfur is intercepted by the mixed cellulose membrane (7). There are two slag removal plates (6). During slag removal, the two plates can rotate and scrape simultaneously from the clockwise and counterclockwise angles and are discharged through the slag discharge outlet (8); at the bottom of the inlet zone (14) are a water distributor (11) and an inlet (A); the outlet zone (15) is provided with an outlet (16), and the outlet is 2 - 3 cm away from the top of the outlet zone (15); the lower diameter of the pores of the partition board (II) is < 0.5 cm, the upper diameter is 0.8 - 1 cm, and the thickness is 1.5 - 2.5 cm. The diameter of the iron beads (13) is 0.5 - 0.6 cm; the mixed cellulose membrane (7) is prepared by mixing oxidized cellulose, ethyl cellulose, and nano-titanium dioxide with a solvent to form a casting solution, and then prepared by the phase inversion method. The pore diameter of the mixed cellulose membrane (7) is 0.1 - 0.2 μm. The mass ratio of oxidized cellulose, ethyl cellulose, and nano-titanium dioxide is 10:2 - 5:0.1 - 0.5; among them, the sulfate reduction zone (1) is inoculated with sulfate-reducing bacteria, and the sulfur autotrophic denitrification zone and the anaerobic ammonium oxidation reaction zone of the simultaneous denitrification and desulfurization zone (2) are respectively inoculated with sulfur autotrophic denitrifying bacteria and anaerobic ammonium oxidizing bacteria; during the operation of the reactor, the iron beads will be lifted by the upward water flow. The upward flow rate is controlled ≤ 0.5 m / h so that the iron beads can always be stable in the pores. When the water inlet stops, the iron beads will continue to settle to prevent the elemental sulfur on the partition board from falling into the simultaneous denitrification and desulfurization zone.

2. The reaction device for sulfate reduction - simultaneous denitrification and desulfurization - elemental sulfur recovery according to claim 1, characterized in that, The aspect ratio of the main reactor is 5 - 6:1, and the height ratio of the elemental sulfur recovery zone (3), the simultaneous denitrification and desulfurization zone (2), and the sulfate reduction zone (1) in the main part is 1:3.9 - 4.5:6 - 7.

3. The reaction device for sulfate reduction - simultaneous denitrification and desulfurization - elemental sulfur recovery according to claim 1, characterized in that, The pore diameter of the partition plate (I) is < 0.5 cm, and the thickness is > 3 cm; the upward flow velocity in the reactor is ≤ 0.5 m / h, so that the iron beads will be lifted by the upward water flow and can be stably in the pores all the time.

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