A method for driving denitrification by a polymerized sulfur compound

Abstract

The application provides a polymerized sulfur compound and a preparation method thereof, and a method for denitrification of sewage by using the polymerized sulfur compound, the polymerized sulfur compound is prepared from elemental sulfur and oil containing unsaturated fatty acids, the preparation method is simple, the polymerized sulfur compound is used as a filler of a biological filter, and the processes of heterotrophic denitrification for generating alkalinity and sulfur autotrophic denitrification for generating acidity can be simultaneously carried out, so that the pH of the reaction system can be better maintained in a neutral range, compared with a denitrification filter which needs to add an external organic carbon source, the biological filter using the polymerized sulfur compound as the filler does not need to add the external organic carbon source, secondary pollution can be effectively avoided, and the biological filter has the advantages of high nitrate removal rate and high total nitrogen removal load.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental engineering wastewater treatment, and particularly relates to a method for driving denitrification by polymeric sulfur compounds. BACKGROUND

[0002] Water body eutrophication not only reduces the ornamental value of the water body, but also harms the survival of organisms and increases the cost of wastewater treatment, which is a more prominent phenomenon in surface water pollution. The increase of nitrogen in the water body is one of the fundamental reasons for eutrophication, among which nitrate is the main pollutant, and various forms of nitrogen in nature can be converted into nitrate nitrogen. The national "Drinking Water Health Standards" (GB5749-2006) stipulates that the limit value of nitrate content in water is 10 mg / L, and the nitrate nitrogen content in most areas of China far exceeds this standard. Nitrate nitrogen has become one of the main sources of water pollution in China, and the content of NO3 - and NO2 - in drinking water is too high, which increases the risk of various diseases for water drinkers and damages human health. How to efficiently remove nitrogen is not only the focus of attention of government departments at all levels, but also the difficulty of water environment management.

[0003] Biological denitrification has always been considered the most economical and effective way of denitrification. Heterotrophic denitrification technology needs to consume a large amount of organic matter as a denitrification carbon source. In view of the current low carbon-nitrogen ratio of secondary effluent, the existing heterotrophic denitrification process needs to add carbon source, but due to the fluctuation of water inflow and total nitrogen concentration, the feedback of carbon source dosage and nitrogen concentration change has a time difference, and other problems, which may cause secondary pollution due to excessive addition of organic carbon source, increase the risk of COD exceeding standard in effluent, and have poor denitrification effect. At the same time, there are defects of high alkalinity and sludge production, and the high dependence on carbon source also leads to high operation cost of heterotrophic denitrification for deep denitrification.

[0004] Sulfur autotrophic denitrification technology does not need to add organic carbon source to low-carbon-nitrogen ratio wastewater, and will not cause secondary pollution of organic matter. When the inflow COD is up to standard, the effluent will not exceed the standard again. However, due to the poor solubility of elemental sulfur, the availability of dissolved electrons obtained by microorganisms from the surface of sulfur is limited, so the denitrification load of the system is limited. Secondly, sulfur-driven autotrophic denitrification is an acid-producing process, and when the pH is low, the activity of Thiobacillus will be inhibited, thereby affecting the denitrification efficiency of the system. SUMMARY

[0005] Based on the above technical background, the inventors made great efforts, and found that: the polymeric sulfur compound prepared from elemental sulfur and oil containing unsaturated fatty acid is used as filler for wastewater denitrification, both autotrophic denitrification process with sulfur and its reduced substances as electron donor and heterotrophic denitrification process with organic matter as carbon source and electron donor occur, and the polymeric sulfur compound is more easily used by microorganisms than elemental sulfur, the alkalinity produced by the heterotrophic denitrification process with organic matter in the polymeric sulfur compound filler as electron donor can offset part of the alkalinity consumed by the autotrophic denitrification process with sulfur as electron donor, so that the pH of the reaction system is better maintained in the neutral range, thereby obtaining higher denitrification effect, and the present application is completed.

[0006] The present application provides a polymeric sulfur compound prepared from elemental sulfur and oil containing unsaturated fatty acid.

[0007] The oil containing unsaturated fatty acid is selected from one or more of rapeseed oil, sunflower seed oil, olive oil and soybean oil.

[0008] The present application provides a preparation method of the polymeric sulfur compound according to the first aspect of the present application, which comprises the following steps:

[0009] Step 1, mixing and reacting elemental sulfur and oil containing unsaturated fatty acid at high temperature to obtain an intermediate product;

[0010] Step 2, washing and drying the intermediate product to prepare the polymeric sulfur compound.

[0011] The present application provides the use of the polymeric sulfur compound according to the first aspect of the present application or prepared by the preparation method according to the second aspect of the present application, which can be used as filler of a biological filter for wastewater denitrification.

[0012] The present application provides a method for wastewater denitrification using the polymeric sulfur compound according to the first aspect of the present application or prepared by the preparation method according to the second aspect of the present application.

[0013] The method places the polymeric sulfur compound in a fixed bed reactor for wastewater denitrification. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 An upflow sulfur autotrophic denitrification fixed bed reactor showing a preferred embodiment of the present application;

[0015] Figure 2 A photo showing the polymeric sulfur compound prepared in Example 1 of the present application;

[0016] Figure 3This shows a scanning electron microscope image of the polymerized sulfur compound obtained in Example 1 of the present invention;

[0017] Figure 4 This shows a high-magnification scanning electron microscope image of the polymerized sulfur compound obtained in Example 1 of the present invention;

[0018] Figure 5 The pH and alkalinity changes of the denitrification system effluent of Example 2 and Comparative Example 1 are shown when EBCT = 1h;

[0019] Figure 6 The infrared spectra of the polymerized sulfur compound, elemental sulfur, and rapeseed oil prepared in Example 1 are shown.

[0020] Explanation of icon numbers

[0021] 1-Water tank;

[0022] 2-Water pump;

[0023] 3-Reaction apparatus;

[0024] 4-Water distribution support plate. Detailed Implementation

[0025] The present invention will now be described in detail, and its features and advantages will become clearer and more apparent from these descriptions.

[0026] In existing technologies, elemental sulfur is often used as a filler for wastewater denitrification. The main microorganisms that play a role in denitrification with elemental sulfur are autotrophic denitrifying bacteria, Thiobacillus denitrification. However, autotrophic denitrification is an acid-producing process, and the activity of Thiobacillus denitrification in an acidic environment is inhibited, thereby reducing the denitrification effect. At the same time, elemental sulfur has poor solubility, which limits the acquisition of electrons from the sulfur surface by microorganisms, thus limiting the denitrification load.

[0027] The first aspect of the present invention is to provide a polymeric sulfur compound obtained from elemental sulfur and an oil containing unsaturated fatty acids.

[0028] The inventors have discovered that this polymerized sulfur compound can simultaneously undergo autotrophic and heterotrophic denitrification when treating wastewater, and can stably release carbon sources during the denitrification process. The amount of carbon source released is basically the same as that consumed in the heterotrophic denitrification process, and there is no excessive residual carbon source in the wastewater after treatment. At the same time, the alkalinity consumption is small, which can maintain the pH of the reaction system within the neutral range, achieving a good denitrification effect.

[0029] The oil containing unsaturated fatty acids is selected from one or more of rapeseed oil, olive oil, soybean oil and sunflower oil, preferably from one or two of rapeseed oil and olive oil, and more preferably from rapeseed oil. The polymerized sulfur compounds obtained from rapeseed oil have better denitrification effect and higher total nitrogen removal load.

[0030] The mass ratio of elemental sulfur and the oil containing unsaturated fatty acid is (0.5-5):1, preferably (0.7-3):1, and more preferably (0.9-1.5):1.

[0031] The mass ratio of elemental sulfur and the oil containing unsaturated fatty acid affects the sulfur content of the polymeric sulfur compound, and further affects the nitrogen removal effect and removal load of the polymeric sulfur compound on the wastewater.

[0032] The mass fraction of sulfur in the polymeric sulfur compound is 10%-90%, preferably 20%-80%, and more preferably 25%-75%. The polymeric sulfur compound with the sulfur content in the above range has more stable nitrogen removal effect, higher total nitrogen removal load, and stronger adaptability to volume load change.

[0033] The maximum total nitrogen removal load of the biofilter filled with the polymeric sulfur compound can reach 1.7 kgN / (m 3 ·d), the effluent NO3 - -N concentration is at least 0.6 mg / L, and the effluent NO2 - -N concentration is at least 0.2 mg / L.

[0034] The polymeric sulfur compound is prepared by a method comprising the following steps:

[0035] Step 1: mixing and reacting elemental sulfur and the oil containing unsaturated fatty acid at high temperature to obtain an intermediate product;

[0036] Step 2: washing and drying the intermediate product to obtain the polymeric sulfur compound.

[0037] The second aspect of the present application provides a preparation method of the polymeric sulfur compound of the first aspect of the present application, which comprises the following steps:

[0038] Step 1: mixing and reacting elemental sulfur and the oil containing unsaturated fatty acid at high temperature to obtain an intermediate product;

[0039] Step 2: washing and drying the intermediate product to obtain the polymeric sulfur compound.

[0040] The step is described and explained in detail as follows.

[0041] Step 1: mixing and reacting elemental sulfur and the oil containing unsaturated fatty acid at high temperature to obtain an intermediate product.

[0042] The mixing is preferably performed in a reaction kettle, and more preferably, the elemental sulfur is heated and melted first, and then the oil containing unsaturated fatty acid is added to the elemental sulfur.

[0043] The oil containing unsaturated fatty acid is added dropwise, and the elemental sulfur and the oil containing unsaturated fatty acid form a two-phase mixture under constant stirring.

[0044] The mixing reaction temperature is 160-200°C, preferably 170-190°C, and more preferably 180°C. The mixture is stirred constantly at this temperature until an elastic solid, i.e. the intermediate product, is obtained.

[0045] The reaction time is 10-60 min, preferably 15-45 min, and more preferably 20 min.

[0046] The oil containing unsaturated fatty acid is selected from one or more of rapeseed oil, sunflower seed oil, olive oil and soybean oil, preferably from one or both of rapeseed oil and olive oil, and more preferably rapeseed oil.

[0047] The mass ratio of the elemental sulfur to the oil containing unsaturated fatty acid is (0.1-10):1, preferably (0.2-5):1, and more preferably (0.3-4):1.

[0048] The polymeric sulfur compound prepared in the above mass ratio range has a suitable sulfur content and is good at denitrification of wastewater as a filler of a biofilter, and has a higher total nitrogen removal load and stronger adaptability to volume load change than elemental sulfur (orthorhombic sulfur).

[0049] Step 2, washing and drying the intermediate product to obtain the polymeric sulfur compound.

[0050] The intermediate product is cut into particles, and the particle size is preferably 0.1-20 mm, and more preferably 0.2-12 mm.

[0051] The specific surface area of the particles is related to the particle size, and the polymeric sulfur compound in the above particle size range has a moderate specific surface area, can be fully contacted with wastewater, and improves the nitrogen removal load.

[0052] The cut particles are washed and soaked in an alkaline solution, preferably 0.1 mol / L NaOH solution, to remove residual hydrogen sulfide.

[0053] Mechanical stirring is performed during the soaking process, and the stirring time is 60-120 min, preferably 90 min. The residual hydrogen sulfide is fully removed.

[0054] After soaking, the alkaline solution is filtered off, and the separated particles are washed with water, and the operation is repeated 2-5 times.

[0055] After washing, drying is performed, preferably air drying at room temperature, and the drying time is 20-30 h, preferably 24 h.

[0056] The polymeric sulfur compound prepared by the method can stably release carbon source in the denitrification process, and provide electron donor for the heterotrophic denitrification process. n The content of mercaptan on the polymeric sulfur compound filler increases after the denitrification process, which indicates that the polymeric sulfur compound filler itself can participate in the denitrification process, and the long-chain polysulfide group connected with C atom in the structure of the polymeric sulfur compound is changed into mercaptan (-SH) to form mercaptan. It is also found that the cyclic structure of the polymeric sulfur compound is more easily utilized by microorganisms than the cyclic structure of elemental sulfur.

[0057] The third aspect of the present application provides a use of the polymeric sulfur compound prepared by the method of the second aspect of the present application, which is used as filler of a biofilter for wastewater denitrification.

[0058] The fourth aspect of the present application provides a method for wastewater denitrification using the polymeric sulfur compound prepared by the method of the second aspect of the present application.

[0059] The method places the polymeric sulfur compound in a fixed bed reactor for wastewater denitrification.

[0060] The fixed bed reactor is made of acrylic plate. Figure 1 The fixed bed reactor is made of acrylic plate.

[0061] The inventors found that the polymeric sulfur compound used as filler of the fixed bed reactor can generate heterotrophic denitrifying bacteria, such as Stenotrophomonas and Pseudomonas aeruginosa, in the wastewater treatment process, and both autotrophic denitrification process using sulfur and its reduced substances as electron donor and heterotrophic denitrification process using organic substances as carbon source and electron donor occur, and the abundance of Thiobacillus for denitrification increases to twice of that of elemental sulfur, and the population advantage is greater.

[0062] The fixed bed reactor comprises a water tank 1, a water pump 2 and a reaction device 3, as shown in the figure. Figure 1 The water pump 2 is located between the water tank 1 and the reaction device 3, and the water tank 1, the reaction device 3 and the water pump 2 are connected by pipelines.

[0063] The wastewater is pumped into the reaction device through the lower part of the reaction device, and is discharged through the upper part of the reaction device. Before the wastewater is pumped into the reaction device, nitrogen gas is preferably used for stripping to remove dissolved oxygen in the wastewater, and the cover is sealed to efficiently remove nitrogen gas in the bed and create an anoxic environment for the growth of microorganisms, thereby ensuring normal operation of the reactor.

[0064] The lower part of the reaction device 3 is provided with a water inlet and a water distribution support plate 4, and the sewage is introduced into the reaction device through the water inlet and reaches the water outlet by passing through the filler from bottom to top.

[0065] The water distribution support plate is provided with small holes for uniformly distributing the sewage to the filler layer.

[0066] Preferably, the diameter of the small holes is 0.5-2mm, preferably 1mm.

[0067] The diameter of the reaction device 3 is 30-50mm, preferably 40mm. The height of the reactor is 170-200mm, preferably 180-190mm.

[0068] According to a preferred embodiment of the present application, the volume ratio of the polymeric sulfur compound filler to the total volume of the reaction device 3 is 1:(2-3), preferably 1:(2.5-2.8).

[0069] The volume of the polymeric sulfur compound as a filler will affect the denitrification effect on the sewage. If the amount of the filler is too small, the denitrification effect on the sewage will be poor, and if the amount of the filler is too large, the cost of sewage treatment will be increased.

[0070] The sewage to be treated is pumped into the reaction device by a water pump, and the flow rate of the sewage is 0.19-6.8mL / min, preferably 0.5-2.26mL / min, and more preferably 0.7-2mL / min.

[0071] The time for the sewage to be treated to pass through the reaction device is 5min-10h, preferably 10min-8h, and more preferably 10min-6h.

[0072] If the flow rate of the sewage is too fast or the time for the sewage to pass through the reaction device is too short, the contact time between the denitrifying bacteria in the system and the nitrate nitrogen in the water body will be reduced, the sewage will not be fully contacted with the filler, the denitrification performance in the system will be reduced, the concentration of nitrate nitrogen in the effluent will be significantly increased, resulting in poor denitrification effect, and the too fast flow rate will also affect the microorganisms in the reactor, causing the microorganisms to fall off from the surface of the filler and be discharged with the water flow, resulting in a decrease in the denitrification efficiency. If the flow rate of the sewage is too slow or the time for the sewage to pass through the reaction device is too long, the water treatment time will be prolonged, which is not conducive to improving the sewage treatment efficiency.

[0073] The present application has the following beneficial effects:

[0074] (1) Compared with the sulfur filled bed biofilter, the polymeric sulfur compound of the present application has the ability to intercept suspended pollutants, and as the filler of the biofilter, it can simultaneously carry out the heterotrophic denitrification process for producing alkalinity and the sulfur autotrophic denitrification process for producing acidity, the amount of carbon source released is basically equal to the amount of carbon source consumed in the heterotrophic denitrification process, and there is no excess residual carbon source material in the effluent, effectively avoiding secondary pollution;

[0075] (2) The polymeric sulfur compound filled bed biofilter of the present application has stronger adaptability to volume load change and more stable denitrification effect;

[0076] (3) The maximum total nitrogen removal load of the biofilter using the polymeric sulfur compound as the filler can reach 1.7 kgN / (m 3 ·d), and the optimal EBCT is 1 h, under which the concentration of NO3 - -N (nitrate nitrogen, referring to the nitrogen element contained in nitrate) in the effluent is as low as 0.6 mg / L, and the concentration of NO2 - -N is as low as 0.2 mg / L;

[0077] (4) In the process of treating sewage, the polymeric sulfur compound can stably release carbon source and consume less alkalinity, and there is no need to add alkali substances in the process of sewage treatment.

[0078] Examples

[0079] The present application is further illustrated by specific examples, which are limited to illustrate the present application and are not used to limit the scope of the present application.

[0080] Example 1

[0081] 20 g of elemental sulfur (orthorhombic sulfur, composed of S8 cyclic molecules) was added to a reaction kettle, stirred and melted, and then heated to 180℃, and then 20 g of rapeseed oil was added dropwise, and the sulfur oil was continuously stirred to form a two-phase mixture. The stirring was continued for 10 min, the sulfur oil was fully mixed, and a brownish viscous liquid was formed. The mixture was continuously heated at 180℃ for 20 min, and a glass rod was continuously stirred. Finally, a solid with elasticity was obtained.

[0082] The solid was taken out of the reaction kettle, cut into particles with diameters ranging from 0.2 mm to 12 mm (average diameter of 4 mm), soaked in a 0.1 mol / L NaOH solution, stirred at room temperature for 90 min to remove residual hydrogen sulfide, and then the particles were separated by filtration and washed with 50 mL of deionized water. The operation was repeated three times, and the particles were air-dried under room pressure for 24 h to obtain the polymeric sulfur compound, the photograph of which is shown in Figure 2 .

[0083] Example 2

[0084] The fixed bed reactor is made of acrylic plate, and the actual product is as follows Figure 1 The device main body is 40 mm in diameter and 186 mm in height, with a total volume of 233 mL, and the carrier filling volume is 85 mL. The filler is the polymeric sulfur compound prepared in Example 1. A water inlet and a water distribution support plate are arranged at the lower part of the device, and a small hole with a diameter of 1 mm is opened on the support plate to uniformly distribute water. The system is inoculated with sludge taken from the activated sludge (10 g TSS / L) in the secondary sedimentation tank of the Gaobeidian Sewage Treatment Plant in Beijing, which is placed in a closed state for a long time to become anaerobic activated sludge, and is used as seed sludge after filtration with a filter screen. Artificial water is used to simulate sewage, and the water quality is shown in Table 1:

[0085] Table 1

[0086]

[0087] The sewage passes through the reaction device in the fixed bed reactor, with a flow rate of 1.13 mL / min in the reaction device and a passing time of 1 h through the reaction device.

[0088] Example 3

[0089] The preparation of the polymeric sulfur compound is carried out in a similar manner to Example 1, except that 10 g of elemental sulfur (orthorhombic sulfur composed of S8 cyclic molecules) is added to the reaction kettle, stirred and melted, then heated to 180°C, and then 30 g of rapeseed oil is added dropwise.

[0090] Example 4

[0091] The preparation of the polymeric sulfur compound is carried out in a similar manner to Example 1, except that 30 g of elemental sulfur (orthorhombic sulfur composed of S8 cyclic molecules) is added to the reaction kettle, stirred and melted, then heated to 180°C, and then 10 g of rapeseed oil is added dropwise.

[0092] Example 5

[0093] The sewage denitrification is carried out in a similar manner to Example 2, except that the filler is the polymeric sulfur compound prepared in Example 3.

[0094] Example 6

[0095] The sewage denitrification is carried out in a similar manner to Example 2, except that the filler is the polymeric sulfur compound prepared in Example 4.

[0096] Example 7

[0097] The sewage denitrification is carried out in a similar manner to Example 2, except that the passing time through the reaction device is 6 h.

[0098] Example 8

[0099] Wastewater denitrification was carried out in a manner similar to that in Example 2, except that the time through the reaction device was 0.5 h.

[0100] Example 9

[0101] Wastewater denitrification was carried out in a similar manner to Example 2, except that the time spent in the reaction device was 15 minutes.

[0102] Example 10

[0103] Wastewater denitrification was carried out in a manner similar to that in Example 2, except that the time spent in the reaction device was 10 minutes.

[0104] Comparative Example

[0105] Comparative Example 1

[0106] Wastewater treatment was carried out in a manner similar to that in Example 2, except that the packing material in the fixed-bed reactor was elemental sulfur (orthorhombic sulfur, composed of S8 cyclic molecules), which was purchased from Sinopec Qilu Petrochemical Company, and was spherical with a particle size of 3-6 mm.

[0107] Experimental Example

[0108] Experiment Example 1: SEM Testing

[0109] The polymerized sulfur compound obtained in Example 1 was subjected to scanning electron microscopy (SEM) analysis, and the results are as follows: Figure 3 and Figure 4 As shown.

[0110] from Figure 3 As can be seen, the surface structure of polymeric sulfur compound packing is loose and layered, which can provide suitable attachment sites and a good growth environment for microbial communities. This indicates that polymeric sulfur compound packing can be a good carrier and medium for biofilm growth.

[0111] Figure 4 To obtain a scanning electron microscope image magnified 20,000 times, from Figure 4 The images clearly show that a large number of microorganisms have grown and adhered to the polymerized sulfur compound packing material. The sticky substance secreted by these microorganisms binds them tightly to the packing material, forming a dense biofilm. Furthermore, the microorganisms attached to the surface of the polymerized sulfur compound packing material are primarily spherical and rod-shaped. This demonstrates that the polymerized sulfur compound packing material can successfully support a large number of functional microbial communities, including both heterotrophic and autotrophic denitrification bacteria. This indicates that the polymerized sulfur compound packing material can serve as both an electron donor in the denitrification process and a carrier and medium for the growth and attachment of microbial communities.

[0112] Experiment Example 2: Measurement of Nitrate Nitrogen

[0113] The nitrate nitrogen of the influent and effluent was measured, and the nitrate nitrogen measurement used an ion chromatograph, model 883 Basic ICPlus, produced by Swiss Metrohm China Co., Ltd. The total nitrogen removal load: influent total nitrogen x total water volume / reaction volume. The measurement results are shown in Table 2.

[0114] Table 2

[0115] Influent nitrate nitrogen content Effluent nitrate nitrogen content Nitrate nitrogen removal rate Example 2 20.7 mg / L 0.6 mg / L 97.1％ Example 7 21.955 mg / L 0.51 mg / L 97.68％ Example 8 20.267 mg / L 0.2745 mg / L 98.65％ Example 9 19.079 mg / L 1.675 mg / L 91.22％ Example 10 19.211 mg / L 1.699 mg / L 91.16％ Comparative Example 1 19.1 mg / L 4.7 mg / L 75.3％

[0116] As can be seen from Table 2, using the polymeric sulfur compound described in Example 1 for wastewater denitrification can greatly reduce the nitrate nitrogen content of the effluent. Through the total nitrogen removal load formula, the total nitrogen removal load of Example 2 is 1.7 kg·N / (m 3 ·d), and the total nitrogen removal load of Comparative Example 1 is 0.6 kg·N / (m 3 ·d). It shows that using the polymeric sulfur compound of the present application for wastewater denitrification has a higher total nitrogen removal load.

[0117] Comparative Example 2 to Example 10, it can be seen that the time of wastewater through the reaction device will affect the removal rate of nitrate nitrogen, and the removal rate of nitrate nitrogen in wastewater is the highest when the time through the reaction device is 0.5 h.

[0118] System effluent pH and alkalinity change test of experimental example 3

[0119] The pH value of the water body will change the charge state of the substrate and microbial enzymes, thereby affecting the activity of the microbial enzymes and the degradation of the substrate by the microbial community, and the suitable reaction system pH of the denitrifying bacteria is in the range of 7-8.

[0120] The specific test process of the effluent pH and alkalinity is as follows: the filler is elemental sulfur described in Example 2 and Comparative Example 1, and the effluent pH and alkalinity under the condition of 1 h through the wastewater treatment device are tested. During the wastewater treatment process, the pH of the influent is maintained at 7.9±0.1, and the alkalinity is 212±6 mg / L. The test results are shown in Table 3. Figure 5

[0121] The pH of the system effluent of Comparative Example 1 gradually decreased from 7.9±0.1 to 6.3±0.1, and the alkalinity was 111±3 mg / L. This is because the sulfur autotrophic denitrification process is a process of consuming alkalinity. The pH of the polymeric sulfur compound system effluent of Example 2 decreased from 7.9±0.1 to 6.6±0.1, and the alkalinity was 151±20 mg / L. Compared with the higher pH and alkalinity of the system effluent of Comparative Example 1, it shows that the alkalinity produced by the heterotrophic denitrification process in the system offsets part of the acid produced by the sulfur autotrophic denitrification process, and self-balancing can be achieved.

[0122] Experimental example 4 infrared test ​

[0123] To investigate the correlation between the polymerized sulfur compound filler and the functional groups of rapeseed oil, Fourier transform infrared spectroscopy (FTIR) analysis was performed on the polymerized sulfur compound filler prepared in Example 1 and rapeseed oil, with a wavenumber range of 3250–500 cm⁻¹. -1 The test results are as follows: Figure 6 As shown.

[0124] from Figure 6 As can be seen from this, the polymerized sulfur compound filler at 1745 cm⁻¹ -1 The peak appearing at 2925 cm⁻¹ is caused by the stretching vibration of the C=O chemical bond. -1 2854cm -1 The saturated CH stretching vibration peaks appear at [value missing], which are consistent with the infrared spectrum of rapeseed oil. The stretching vibration peaks of unsaturated hydrocarbons C=CH and C=C are located at 30-10 cm⁻¹ in the infrared spectrum of rapeseed oil. -1 1650cm -1 The presence of these substances in the infrared spectrum, while they are absent in the infrared spectrum of polymeric sulfur compound fillers, indicates that sulfur reacts with olefins to form polysulfides.

[0125] Infrared spectral analysis of polymeric sulfur compounds showed that the polymeric sulfur compounds prepared by synthesizing rapeseed oil and elemental sulfur possess the characteristics of chemical bonds from both raw materials.

[0126] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. Use of a polymeric sulfur compound, characterized in that, The polymerized sulfur compound is prepared from elemental sulfur and oil containing unsaturated fatty acid; The oil containing unsaturated fatty acid is selected from one or more of rapeseed oil, sunflower oil, olive oil and soybean oil, The mass fraction of sulfur in the polymerized sulfur compound is 25% to 75%, The polymerized sulfur compound is used as filler of biofilter for denitrification of sewage, The maximum total nitrogen removal load of the polymeric sulfur compound as a filler in a biofilter is 1.7 kg N / (m 3 ·d), the effluent NO3 - -N concentration is as low as 0.6 mg / L, the effluent NO2 - -N concentration is as low as 0.2 mg / L, The preparation method of the polymerized sulfur compound comprises the following steps: 1 Step 1, mixing and reacting elemental sulfur and oil containing unsaturated fatty acid at high temperature to obtain an intermediate product, the mass ratio of the elemental sulfur and the oil containing unsaturated fatty acid is (0.2-5):1, and the mixing and reacting temperature is 160-200℃; Step 2, washing and drying the intermediate product to prepare the polymerized sulfur compound, In step 2, the intermediate product is cut into particles, and the particle size is 0.1-20mm.

2. Use according to claim 1, characterized in that, In step 1, the mass ratio of the elemental sulfur and the oil containing unsaturated fatty acid is (0.3-4):

1.

3. Use according to claim 1, characterized in that, In step 1, the mixing and reacting temperature is 170-190℃.

4. Use according to claim 1, characterized in that, In step 2, the particle size is 0.2-12mm.

5. A method for denitrification of sewage using polymeric sulfur compounds, characterized by, The polymerized sulfur compound is the polymerized sulfur compound of any one of claims 1 to 4 or prepared by the preparation method. The method places the polymerized sulfur compound in a fixed bed reactor for denitrification of sewage.

6. The method of claim 5, wherein the method is a method of denitrification of sewage. The fixed bed reactor comprises a water tank (1), a water pump (2) and a reaction device (3); The lower part of the reaction device (3) is provided with a water inlet and a water distribution supporting plate (4), and the volume ratio of the polymerized sulfur compound filler to the total volume of the reaction device is 1:(2-3).

Images