Sulfur autotrophic denitrification method to cope with fluctuating environmental conditions

Abstract

The present invention discloses a sulfur autotrophic denitrification method for coping with fluctuating environmental conditions. The method uses an improved sulfur autotrophic denitrification tank, separates the autotrophic denitrification filter into two completely separate units: a deep denitrification unit and a sulfur disproportionation unit. The original water inlet and backwash equipment are connected to the bottom of the deep denitrification unit. A reflux pump is provided on the outlet pipe of the deep denitrification unit to transfer part of the deep denitrification unit effluent to the sulfur disproportionation unit. The sulfur disproportionation unit effluent is then transferred to a mixing device via a new water inlet provided in the outlet area of the sulfur disproportionation unit. The effluent is mixed with the wastewater to be treated introduced through the original water inlet and then transferred to the deep denitrification unit. The top of the sulfur disproportionation unit is sealed, and a gas collection pipe is provided, which is connected to a gas recovery module. The nitrate and nitrogen content of the treated effluent is stable, and the effluent water quality is stable at both high and low temperatures.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment, and in particular to a sulfur autotrophic denitrification method for coping with environmental condition fluctuations. Background Art

[0002] Despite significant progress in wastewater treatment since the beginning of the 21st century, my country's water quality remains poor, and the situation regarding water pollution prevention and control is dire. Nitrogen pollution has become a major environmental issue threatening the sustainable development of China's water resources and ecological environment. With the promulgation of my country's "Ten Water Regulations," discharge standards for most wastewater treatment plants have been further tightened, with some environmentally sensitive areas facing even stricter total nitrogen emission standards. Therefore, deep denitrification is a key goal of advanced urban wastewater treatment.

[0003] Sulfur autotrophic denitrification process refers to the use of reduced sulfur (S 0 、S 2- 、S2O3 2- ) as an electron donor, using autotrophic denitrifying bacteria to remove nitrogen, no external carbon source is required, no carbon emissions are generated, and the cost of removing the same equivalent of nitric nitrogen is low, which has a high advantage. In the sulfur autotrophic denitrification process, the technology of using sulfur elemental particles as electron donors is more common. Compared with other reduced sulfur, sulfur elemental particles are solid and can serve as the basis for microbial growth and electron donors at the same time. The sulfur autotrophic denitrification filter process with sulfur elemental particles as filler constructed on this theory has a simple operation mode and high denitrification efficiency. The use of sulfide as an electron donor has the advantages of flexible addition and fast denitrification rate compared to sulfur element, but it has the risk of causing secondary pollution during use.

[0004] Sulfur autotrophic denitrification processes are sensitive to fluctuations in environmental conditions, such as influent flow, temperature, and salinity. For example, in winter, when temperatures are low or influent flows are high, the microbial reaction rate decreases, resulting in reduced denitrification efficiency and seasonal excesses in effluent total nitrogen. Alternatively, in summer, when temperatures are high, the microbial reaction rate increases, leading to increased denitrification efficiency and excessive denitrification, resulting in wasteful elemental sulfur. This can even lead to extremely low nitrate-nitrogen levels in the effluent, causing elemental sulfur to biodisproportionately produce harmful sulfides. Because the electron donor in sulfur autotrophic denitrification systems is a granular sulfur filler, the total amount of electron donors is fixed, lacking flexible and effective control measures to adapt to these environmental changes. Adjusting the filter's denitrification efficiency requires additional liquid sulfur-based electron donors, which are typically expensive, negating the cost advantage of sulfur autotrophic filters.

[0005] For example, the current daily processing capacity is 40,000m 3 Sulfur autotrophic denitrification filter, the size of which is 35×10×2.5m=875m3 , the filler is elemental sulfur particles with a particle size of 2-6mm, and the filler bed height is 2m. The influent of the filter is the secondary biochemical effluent of the domestic sewage treatment plant, with a large fluctuation of total nitrogen of 13-20mg / L, ammonia nitrogen of 0.2-0.6mg / L, a carbon-nitrogen ratio of 1-2, COD of 25-30mg / L, and SS of 5-10mg / L. During the operation of the filter, since the filter is located in the north of my country, the temperature fluctuates greatly throughout the year, and the inlet water temperature fluctuates between 15-30 degrees Celsius. The wide water temperature fluctuation causes large changes in the microbial reaction rate, which causes seasonal fluctuations in the denitrification capacity of the filter (such as Figure 2 Due to the combined effects of fluctuations in influent total nitrogen and seasonal fluctuations in the filter's denitrification capacity, the filter's effluent nitrate-nitrogen concentration failed to meet the target denitrification goal of 5 mg / L in winter (December-February). In summer (May-August), the filter's effluent nitrate-nitrogen concentration was too low (<2 mg / L), far exceeding the target, resulting in electron donor waste and poor economic efficiency. Furthermore, when the effluent nitrate-nitrogen concentration was too low, sulfur disproportionation occurred, causing harmful sulfide emissions to exceed the standard (1 mg / L, as per GB 18918-2002).

[0006] The problems of sulfur autotrophic denitrification filter failing to meet nitrogen removal standards in winter and excessive nitrogen removal and sulfide production in summer have seriously affected its widespread application. Summary of the Invention

[0007] To solve the above problems, the present inventors conducted in-depth research and divided the existing sulfur autotrophic denitrification filter into two units. The operating states of the two units were adjusted to cause a biological disproportionation reaction of elemental sulfur in one of the units. The reaction rate of the reaction unit was controlled and the sulfide produced by the reaction unit was used to adjust the denitrification efficiency of the other sulfur autotrophic denitrification filter. After the above transformation, since the total volume of the deep denitrification unit was reduced while the water treatment volume remained unchanged, its denitrification load at high temperature was reduced, thereby avoiding the phenomenon of sulfur disproportionation caused by too low nitrate in the effluent. The disproportionation product can be added to the deep denitrification unit as needed, thereby increasing the denitrification load of the deep denitrification unit in winter and avoiding the problem of excessive effluent water. The present invention was thus completed.

[0008] The object of the present invention is to provide the following aspects:

[0009] The first aspect is to deal with the sulfur autotrophic denitrification method for fluctuating environmental conditions, using an improved sulfur autotrophic denitrification tank. In the improved sulfur autotrophic denitrification, the autotrophic denitrification filter is divided into two completely separated units, a deep denitrification unit 2 and a sulfur disproportionation unit 1, wherein:

[0010] In the sulfur disproportionation unit 1 and the deep denitrification unit 2, there are respectively a water distribution area 10, a supporting layer 11, a reaction area 12 and a water outlet area 13 from bottom to top. The supporting layer is filled with pebbles, and the reaction area is filled with sulfur particles.

[0011] The original water inlet pump 3 and backwash water pump 9 are connected to the water distribution area at the bottom of the deep denitrification unit 2. A reflux pump 5 is installed on the outlet pipe of the outlet area 13 of the deep denitrification unit 2 to transport part of the outlet water of the deep denitrification unit 2 to the sulfur disproportionation unit 1.

[0012] A new water inlet pump 4 is installed in the outlet area of the sulfur disproportionation unit 1, through which the outlet water of the sulfur disproportionation unit 1 is transported to the mixing device 6, mixed with the wastewater to be treated input through the original water inlet device 3, and then transported to the deep denitrification unit 2.

[0013] The top of the sulfur disproportionation unit is sealed, and a gas collection pipeline is provided, which is connected to the gas recovery module 14 .

[0014] Second aspect: The above-mentioned sulfur autotrophic denitrification method for coping with environmental fluctuations comprises the following steps:

[0015] (1) The wastewater to be treated is transported to the deep denitrification unit 2 through the original water inlet equipment 3, while keeping the original water inlet flow unchanged;

[0016] (2) The effluent from the deep denitrification unit 2 is discharged, and part of the effluent enters the sulfur disproportionation unit 1 through the reflux pump 5. The empty bed residence time of the sulfur disproportionation unit is 2 to 10 hours;

[0017] (3) The effluent from the sulfur disproportionation unit 1 passes through the water inlet device 4, is mixed with the wastewater to be treated delivered by the original water inlet device 3 in the mixing device 6, and then enters the deep denitrification unit 2;

[0018] In the closed sulfur disproportionation unit 1, the elemental sulfur undergoes a biodisproportionation reaction to form sulfide and sulfate.

[0019] A third aspect: The above-mentioned sulfur autotrophic denitrification method for coping with environmental fluctuations further includes the following steps (4):

[0020] (4) The effluent total nitrogen and dissolved oxygen data are collected by the effluent intelligent analysis unit 8 arranged on the effluent pipe of the deep denitrification unit 2 and sent to the PLC controller. The influent total nitrogen and dissolved oxygen data of the wastewater to be treated are collected by the influent intelligent analysis unit 7 arranged at the rear end of the original influent pump 3 and sent to the PLC controller to adjust the operating parameters of the sulfur disproportionation unit.

[0021] In a preferred embodiment, the effluent intelligent analysis unit 8 is composed of a total nitrogen monitoring module (genesite SJ-TN2131) and a dissolved oxygen monitoring module (genesite DO650M) to detect the total nitrogen and dissolved oxygen in the effluent; the treatment intelligent analysis unit 7 is composed of a total nitrogen monitoring module (genesite SJ-TN2131) and a dissolved oxygen monitoring module (genesite DO650M) to detect the total nitrogen and dissolved oxygen in the wastewater to be treated.

[0022] In the present invention, the nitrogen in the wastewater to be treated and the effluent is mainly composed of nitric nitrogen, and other forms of nitrogen such as ammonia nitrogen are extremely low. The total nitrogen in the effluent is basically the same as the nitric nitrogen, and the total nitrogen content detected is used as the nitric nitrogen content, that is, the nitrate content.

[0023] A fourth aspect: In the above-mentioned sulfur autotrophic denitrification method for coping with environmental fluctuations, the process of adjusting the operating parameters of the sulfur disproportionation unit includes:

[0024] (41) Determine the design denitrification load capacity of the deep denitrification unit at the design temperature: At the design temperature, completely close the reflux pump 5, open the inlet pump 3, monitor the total nitrogen concentration of the wastewater to be treated and the effluent of the sulfur autotrophic denitrification reactor, and calculate the design denitrification load R0 of the deep denitrification unit.

[0025] R0=(C i -C e ) / t×24 / 1000

[0026] Where: R——denitrification load, kg / m 3 / d;

[0027] C i ——Influent nitrate concentration, mg / L;

[0028] C e ——Effluent nitrate concentration, mg / L;

[0029] t——empty bed residence time of deep denitrification unit, h;

[0030] (42) Determine the relationship between the ratio of sulfur autotrophic denitrification load in the sulfur disproportionation unit and the amount of sulfide produced in the sulfur disproportionation unit:

[0031] At the design temperature of the denitrification filter, the flow rate of the reflux pump 5 is maintained at 10% of the flow rate of the original water inlet pump 3, and the flow rate of the new water inlet pump 4 is changed so that the proportion of the wastewater mixed with the wastewater to be treated is continuously increased. The total nitrogen nitrate concentration of the inlet and outlet of the deep denitrification unit is measured (data at 3-5 points are measured), and the denitrification load R under different sulfur disproportionation unit outlet flow rates is obtained. The relationship between the denitrification load enhancement ratio A of the deep denitrification unit and the amount of mixed sulfide M is obtained by linear fitting calculation, and k1 and b1 are determined:

[0032] in:

[0033] R=(C i -C e ) / t×24 / 1000

[0034] R——denitrification load, kg / m 3 / d;

[0035] C i ——Influent nitrate concentration, mg / L;

[0036] C e ——Effluent nitrate concentration, mg / L;

[0037] t——empty bed residence time of deep denitrification unit, h;

[0038] A=R / R0=k1×M+b1

[0039] A——denitrification load enhancement ratio;

[0040] R——measured denitrification load, kg m -3 d -1 ;

[0041] R0——denitrification load designed for deep denitrification unit, kg m -3 d -1 ;

[0042] M——Sulfide addition amount (added from the sulfur disproportionation unit), kg m -3 d -1 ;

[0043] k1, b1——parameters to be determined

[0044] (43) Determine the relationship between the amount of sulfide produced by the sulfur disproportionation unit and the influent flow rate and nitrate concentration of the sulfur disproportionation unit influent:

[0045] At the design temperature of the denitrification filter, the new water inlet pump 4 is completely closed, and the effluent from the sulfur disproportionation unit 1 does not enter the deep denitrification unit 2 but is directly discharged. At this time, the nitrate concentration in the effluent from the deep denitrification unit is maintained at N0. The flow rate Q of the reflux pump 5 is adjusted to change the inlet flow rate of the sulfur disproportionation unit, and the amount M of sulfide produced by the sulfur disproportionation unit at this time is measured (data from 3-5 points are measured).

[0046] Mix untreated wastewater and the effluent from the deep denitrification unit, keep the influent volume of the sulfur disproportionation unit at 10% unchanged as Q0, change the mixing ratio to adjust the nitrate concentration of the influent of the sulfur disproportionation unit (8-15 mg / L), and measure the amount M of sulfide produced by the sulfur disproportionation unit (measure data at 3-5 points).

[0047] The above two sets of test data were subjected to binary linear fitting to calculate the relationship between the sulfide production of the sulfur disproportionation unit and the inlet flow rate and nitrate concentration of the sulfur disproportionation unit, and to determine k2, k3, and b2.

[0048] in:

[0049] M=k2*Q-k3*N+b2

[0050] M——sulfide production, kg m -3 d -1 ;

[0051] Q——water flow rate of sulfur disproportionation unit, %;

[0052] N——nitrate concentration in the influent of sulfur disproportionation unit, i.e. nitrate concentration in the effluent of deep denitrification unit, mg / L;

[0053] k2, k3, b2——parameters to be determined

[0054] (44) Adjust operating parameters through PLC controller:

[0055] The PLC uses the total nitrogen concentration measured by the outlet intelligent analysis module as the nitrate concentration N, and the total nitrogen concentration measured by the inlet energy analysis module as the inlet nitrate concentration C. i , determine the required denitrification load enhancement ratio A, and then calculate the required sulfide amount M, and calculate the reflux flow rate Q according to the total nitrogen concentration of the effluent, and control the effluent flow rate of the sulfur disproportionation unit, that is, the new water pump flow rate, to be the same as the reflux flow rate Q:

[0056] Q=[C i -k1×b2×R0×t-b1×R0×t-(1+k1×k3×R0×t)×N)] / k1×k2×R0×t

[0057] Q——water flow rate of sulfur disproportionation unit, %;

[0058] C i ——Influent nitrate concentration, mg / L;

[0059] N——nitrate concentration in the effluent from the deep denitrification unit, mg / L;

[0060] t——empty bed residence time of deep denitrification unit, h;

[0061] R0——denitrification load designed for deep denitrification module, kg m -3 d -1 ;

[0062] k1, k2, k3, b1, b2——parameters.

[0063] In the present invention, if the total nitrogen concentration of the wastewater to be treated increases, the ambient temperature decreases, the salinity and other factors increase the required denitrification capacity or the microbial activity is affected, that is, the total nitrogen in the effluent does not reach the set value, the PLC controller increases the reflux pump flow rate and the new water inlet equipment flow rate Q according to the required degree, thereby flexibly improving the denitrification efficiency of the deep denitrification unit.

[0064] When the total nitrogen concentration of the wastewater to be treated decreases or the ambient temperature decreases, the required denitrification capacity decreases or the microbial activity increases, that is, the total nitrogen in the effluent is too low. In order to avoid the risk of excessive denitrification, wasting fillers in the filter or generating sulfides, the PLC controller reduces the flow Q of the return pump and the new water inlet equipment according to the required reduction, and flexibly reduces the denitrification efficiency of the deep denitrification unit.

[0065] Fifth aspect: The above-mentioned sulfur autotrophic denitrification denitrification method for coping with fluctuations in environmental conditions, wherein an alkaline solution is provided in the gas recovery module 14 to absorb hydrogen sulfide gas, a pH meter and a hydrogen sulfide monitoring device are provided in the alkaline solution, and a dosing device and a drain valve are also provided. When the pH is less than 9 or the hydrogen sulfide concentration is higher than 100 mg / L, the drain valve is opened, the alkaline solution in the gas recovery module is input into the mixing device 6 to mix with the wastewater to be treated, and the dosing device water pump is started to add an equal amount of alkaline solution from the dosing tank until the pH is greater than 9 and the hydrogen sulfide concentration is lower than 100 mg / L.

[0066] A sixth aspect: the above-mentioned sulfur autotrophic denitrification method for coping with environmental condition fluctuations, wherein a sulfur particle feed port 15 and an observation window 16 are provided on the top of the sulfur disproportionation unit 1 .

[0067] Aspect 7: The above-mentioned sulfur autotrophic denitrification denitrification method for coping with fluctuations in environmental conditions, wherein the volume ratio of the sulfur disproportionation unit 1 to the deep denitrification unit 2 is 1:4-1:8, preferably 1:4-1:6, and more preferably 1:4.

[0068] Eighth aspect: The above-mentioned sulfur autotrophic denitrification denitrification method for coping with fluctuations in environmental conditions, wherein a backwash water pump is connected to the bottom of the deep denitrification unit 2. When the actual flow rate of water inlet to the deep denitrification unit 2 is lower than 90% of the design flow rate, the deep denitrification unit is flushed by the backwash water pump.

[0069] Ninth aspect: The above-mentioned sulfur autotrophic denitrification method for coping with fluctuations in environmental conditions, wherein the particle size of the pebbles filled in the water distribution area is 10-20 mm, and the particle size of the sulfur element particles filled in the reaction area is 2-6 mm.

[0070] Aspect 10: In the above-mentioned sulfur autotrophic denitrification method for coping with fluctuations in environmental conditions, the portion of the effluent from the deep denitrification unit 2 that is transported to the sulfur disproportionation unit 1 via the reflux pump 5 accounts for no more than 10%.

[0071] The beneficial effects of the present invention include:

[0072] (1) In the present invention, by transforming a sulfur disproportionation unit, the sulfide produced by the sulfur biodisproportionation reaction in the unit is used to adjust the denitrification efficiency of the sulfur autotrophic denitrification filter, providing a controllable basis for the denitrification load that is difficult to control in the sulfur autotrophic denitrification process;

[0073] (2) The method of the present invention can flexibly respond to changes in water quality, quantity, and temperature under the same process volume, with simple control and rapid feedback;

[0074] (3) The nitrate-nitrogen concentration in the effluent treated by the method of the present invention is stable, fluctuating between 3 and 5 mg / L, thus overcoming the problem of excessively high or low nitrate-nitrogen in the effluent caused by factors such as season and temperature;

[0075] (4) The method of the present invention improves safety by producing and consuming sulfide in situ in the sulfur disproportionation unit, thereby avoiding the storage and transportation of sulfide and reducing safety risks. Furthermore, a gas recovery module is used to recover sulfide overflowing from the sulfur disproportionation unit, ensuring the operational safety of filter maintenance personnel.

[0076] (5) The sulfide content in the effluent of the sulfur disproportionation unit is high, and hydrogen sulfide will be released into the gas phase under neutral pH conditions. The hydrogen sulfide gas produced by the sulfur disproportionation unit enters the gas recovery module and is absorbed by the alkaline solution. The absorbed alkaline solution is also transported to the deep denitrification unit, reducing the electronic waste caused by hydrogen sulfide overflow;

[0077] (6) The influent of the deep denitrification unit contains sulfides produced by the sulfur disproportionation unit reaction and sulfides from the gas recovery module, so its denitrification efficiency increases with the concentration of sulfides in the influent;

[0078] (7) The sulfur autotrophic denitrification filter before the transformation and the deep denitrification unit and sulfur disproportionation unit after the transformation used the same sulfur granular filler, which greatly reduced the difficulty and cost of the transformation of the original filter; as for the operating costs before and after the transformation, only the input of caustic soda and the power consumption of the reflux pump and mixing module were increased, and the operating costs did not increase significantly. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 Shows the schematic diagram of the structure of the existing sulfur autotrophic denitrification denitrification tank;

[0080] Figure 2 The denitrification effect of using an existing sulfur autotrophic denitrification tank is shown;

[0081] Figure 3a A schematic diagram of the top view of the modified sulfur autotrophic denitrification tank of the present invention is shown;

[0082] Figure 3b The main structural diagram of the sulfur autotrophic denitrification denitrification tank after the present invention is shown;

[0083] Figure 4 The sulfide production of the sulfur disproportionation unit and the sulfide production of the gas recovery module of the sulfur autotrophic denitrification denitrification tank transformed by the present invention are shown;

[0084] Figure 5 The denitrification effect of the sulfur autotrophic denitrification denitrification tank after the transformation of the present invention is shown;

[0085] Figure 6 FIG. 1 is a schematic structural diagram of the gas recovery module 14 of the present invention.

[0086] Reference numerals

[0087] 1-sulfur disproportionation unit 1

[0088] 2-Deep denitrification unit

[0089] 3-Original water inlet pump

[0090] 4-New water inlet pump

[0091] 5- Reflux pump

[0092] 6-Mixing equipment

[0093] 7-Influent intelligent analysis unit

[0094] 8-Water outlet intelligent analysis unit

[0095] 9-Backwash water pump

[0096] 10-Water District

[0097] 11-Supporting layer

[0098] 12-Reaction zone

[0099] 13-Outlet area

[0100] 14-Gas recovery module

[0101] 15-Feed port

[0102] 16-Observation window DETAILED DESCRIPTION

[0103] The present invention will be further described in detail below through the examples. Through these descriptions, the characteristics and advantages of the present invention will become more clear and distinct.

[0104] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0105] In the present invention, elemental sulfur biodisproportionation refers to the process by which autotrophic microorganisms utilize elemental sulfur as both an electron donor and an electron acceptor to produce sulfide and sulfate. This reaction requires that the water be free of dissolved oxygen, nitrates, and other highly oxidizing substances, and that the pH be neutral or alkaline.

[0106] Example

[0107] The present invention is further described below through specific examples. However, these examples are merely exemplary and do not constitute any limitation to the scope of protection of the present invention.

[0108] Comparative Example 1

[0109] Located in Ningjin, Hebei, with a daily processing capacity of 40,000m 3 Sulfur autotrophic denitrification filter, such as Figure 1 As shown, its dimensions are 35×10×2.5m=875m 3 (length, width and height), from bottom to top respectively have a water distribution area 10, a supporting layer 11, a reaction area 12 and a water outlet area 13. The water distribution area is a parallel arrangement of water pipes. The supporting area is filled with 10-20mm pebbles with a filling height of 50mm. The reaction area is filled with sulfur particles with a particle size of 2-5mm and a filling height of 200mm.

[0110] The influent of the filter tank is the secondary biological effluent of the domestic sewage treatment plant. When the actual influent flow rate is lower than 90% of the design flow rate, the deep denitrification unit is flushed by the backwash water pump.

[0111] The denitrification effect of wastewater treated by sulfur autotrophic denitrification filter is shown in Figure 2 The total nitrogen fluctuates greatly at 13-20 mg / L, ammonia nitrogen at 0.2-0.6 mg / L, the carbon-nitrogen ratio is 1-2 lower, COD at 25-30 mg / L, and SS at 5-10 mg / L.

[0112] Example 1

[0113] The sulfur autotrophic denitrification filter in the comparative example 1 was modified as follows: Figure 3a and Figure 3b As shown:

[0114] It is divided into two completely separated units, the deep denitrification unit 2 and the sulfur disproportionation unit 1, with a volume ratio of 4:1. In the sulfur disproportionation unit 1 and the deep denitrification unit 2, the water distribution area 10, the supporting layer 11, the reaction area 12 and the water outlet area 13 remain unchanged;

[0115] The original water inlet pump 3 and backwash water pump 9 are connected to the bottom of the deep denitrification unit 2, and a reflux pump 5 is installed on the outlet pipe of the outlet area 13 of the deep denitrification unit 2 to transport part of the outlet water of the deep denitrification unit 2 to the sulfur disproportionation unit 1.

[0116] A new water inlet pump 4 is installed in the outlet area of the sulfur disproportionation unit 1, through which the outlet water of the sulfur disproportionation unit 1 is transported to the mixing device 6-pipeline mixer, and is mixed with the wastewater to be treated input through the original water inlet device 3 in the mixing device 6 and then transported to the deep denitrification unit 2.

[0117] The top of the sulfur disproportionation unit is sealed and a gas collection pipe is set up to connect to the gas recovery module 14. Figure 6 Alkali solution is provided in the gas recovery module 14. The alkaline solution is sprayed and recycled in the gas recovery module 14 through a pump to absorb hydrogen sulfide gas. A pH meter and a hydrogen sulfide monitoring device are also provided in the alkaline solution. A dosing device and a drain valve are also provided. The dosing tank in the dosing device is connected to the gas recovery module 14 through a pump, and the drain valve is connected to the mixing device 6 through a pipeline.

[0118] The effluent intelligent analysis unit 8 on the effluent pipe of the deep denitrification unit 2 is composed of a total nitrogen monitoring module (genesite SJ-TN2131) and a dissolved oxygen monitoring module (genesite DO650M). It collects the total nitrogen and dissolved oxygen data of the influent and sends them to the PLC controller.

[0119] An inlet water intelligent analysis unit 7 is set at the back end of the original inlet water pump 3, including a total nitrogen monitoring module (genesite SJ-TN2131) and a dissolved oxygen monitoring module (genesite DO650M), which collects the total nitrogen and dissolved oxygen data of the wastewater to be treated and sends them to the PLC controller.

[0120] Keeping the original water inflow unchanged, the secondary biochemical effluent from the domestic sewage treatment plant is passed into the deep denitrification unit 2. When the actual flow rate of the inflow is lower than 90% of the design flow rate, the deep denitrification unit is flushed by backwashing equipment;

[0121] The effluent entering the sulfur disproportionation unit 1 through the reflux pump 5 has an empty bed residence time of 2 hours in the sulfur disproportionation unit;

[0122] When the pH of the alkali solution in the gas recovery module 14 is less than 9 or the concentration of hydrogen sulfide is higher than 100 mg / L, the drain valve is opened, and the alkali solution in the gas recovery module is input into the mixing device 6 to be mixed with the secondary biochemical effluent of the domestic sewage treatment plant to be treated, and the alkali solution is replenished from the dosing device;

[0123] The effluent water quality parameters are collected by the effluent intelligent analysis unit 8 provided on the effluent pipe of the deep denitrification unit 2, and the water quality parameters of the wastewater to be treated are collected by the inlet intelligent analysis unit 7 provided at the rear end of the original inlet pump 3, and the operating parameters of the sulfur disproportionation unit are adjusted:

[0124] (1) Determine the design denitrification load capacity of the deep denitrification unit at the design temperature: At 25°C, completely close the reflux pump 5, open the inlet pump 3, monitor the total nitrogen concentration of the wastewater to be treated and the effluent of the sulfur autotrophic denitrification reactor, and calculate the design denitrification load R0 of the deep denitrification unit;

[0125] (2) Determine the relationship between the ratio of sulfur autotrophic denitrification load in the sulfur disproportionation unit and the amount of sulfide produced in the sulfur disproportionation unit:

[0126] At 25°C, the flow rate of the reflux pump 5 was maintained at 10% of the flow rate of the original water inlet pump 3. The flow rate of the new water inlet pump 4 was changed so that the proportion of the wastewater mixed with the wastewater to be treated continued to increase. The total nitrogen nitrate concentrations of the inlet and outlet of the deep denitrification unit were measured (data at 5 points were measured). The denitrification load R under different sulfur disproportionation unit outlet flow rates was obtained. The relationship between the denitrification load enhancement ratio A of the deep denitrification unit and the amount of mixed sulfide M was obtained by linear fitting calculation, and k1=1.62 and b1=1.00 were determined:

[0127] (3) Determine the relationship between the amount of sulfide produced by the sulfur disproportionation unit and the influent flow rate and nitrate concentration of the influent of the sulfur disproportionation unit:

[0128] At the design temperature of the denitrification filter, the new water inlet pump 4 is completely closed, and the effluent from the sulfur disproportionation unit 1 does not enter the deep denitrification unit 2 but is directly discharged. At this time, the nitrate concentration in the effluent from the deep denitrification unit is maintained at N0. The flow rate Q of the reflux pump 5 is adjusted to change the inlet flow rate of the sulfur disproportionation unit, and the amount M of sulfide produced by the sulfur disproportionation unit at this time is measured (data from 3-5 points are measured).

[0129] Mix untreated wastewater and the effluent from the deep denitrification unit, keep the influent volume of the sulfur disproportionation unit at 10% unchanged as Q0, change the mixing ratio to adjust the nitrate concentration of the influent of the sulfur disproportionation unit (8-15 mg / L), and measure the amount M of sulfide produced by the sulfur disproportionation unit (measure data at 3-5 points).

[0130] The above two sets of test data were subjected to binary linear fitting to calculate the relationship between the sulfide production of the sulfur disproportionation unit and the inlet flow rate and nitrate concentration of the sulfur disproportionation unit, and it was determined that k2=4.62, k3=-0.015, and b2=0.244.

[0131] (4) Adjust operating parameters through PLC controller:

[0132] The PLC uses the total nitrogen concentration measured by the outlet intelligent analysis module as the nitrate concentration N, and the total nitrogen concentration measured by the inlet energy analysis module as the inlet nitrate concentration C. i , determine the required denitrification load enhancement ratio A, and then calculate the required amount of sulfide M, and calculate the reflux flow rate Q according to the total nitrogen concentration of the effluent, and control the effluent flow rate of the sulfur disproportionation unit, that is, the new water pump flow rate, to be the same as the reflux flow rate Q:

[0133] Q=[C i -k1×b2×R0×t-b1×R0×t-(1+k1×k3×R0×t)×N)] / k1×k2×R0×t

[0134] Q——water flow rate of sulfur disproportionation unit, %;

[0135] C i ——Influent nitrate concentration, mg / L;

[0136] N——nitrate concentration in the effluent from the deep denitrification unit, mg / L;

[0137] t——empty bed residence time of deep denitrification unit, h;

[0138] R0——denitrification load designed for deep denitrification unit, kg m -3 d -1 ;

[0139] k1=1.62;

[0140] b1=1.00;

[0141] k2=4.62;

[0142] k3=-0.015;

[0143] b2=0.244.

[0144] The sulfide production of the sulfur disproportionation unit and the sulfide production of the gas recovery module are shown in Figure 4 , denitrification effect is seen Figure 5 .

[0145] The present invention has been described in detail above with reference to preferred embodiments and exemplary examples. However, it should be noted that these specific embodiments are merely illustrative explanations of the present invention and do not constitute any limitation on the scope of protection of the present invention. Various improvements, equivalent substitutions, or modifications may be made to the technical content of the present invention and its embodiments without departing from the spirit and scope of protection of the present invention, and all of these fall within the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the appended claims.

Claims

1. A sulfur autotrophic denitrification method for denitrification in response to fluctuating environmental conditions uses an improved sulfur autotrophic denitrification tank. In the improved sulfur autotrophic denitrification, the autotrophic denitrification filter is divided into two completely separate units, a deep denitrification unit and a sulfur disproportionation unit, wherein: In the sulfur disproportionation unit and deep denitrification unit, there are water distribution area, supporting layer, reaction area and water outlet area from bottom to top respectively. The supporting layer is filled with pebbles, and the reaction area is filled with sulfur particles. Connect the original water inlet pump and backwash water pump to the water distribution area at the bottom of the deep denitrification unit, and set a reflux pump on the outlet pipe of the deep denitrification unit to transport part of the deep denitrification unit outlet water to the sulfur disproportionation unit. A new water inlet pump is installed in the outlet area of the sulfur disproportionation unit, through which the effluent from the sulfur disproportionation unit is transported to the mixing equipment, mixed with the wastewater to be treated input through the original water inlet equipment, and then transported to the deep denitrification unit. The top of the sulfur disproportionation unit is sealed, and a gas collection pipeline is set up to connect to the gas recovery module.

2. The sulfur autotrophic denitrification method for coping with environmental fluctuations as claimed in claim 1, comprising the following steps: (1) Transport the wastewater to be treated to the deep denitrification unit through the original water inlet equipment, keeping the original water inlet flow unchanged; (2) The effluent from the deep denitrification unit is discharged, and part of the effluent enters the sulfur disproportionation unit through a reflux pump. The empty bed residence time of the sulfur disproportionation unit is 2 to 10 hours; (3) The effluent from the sulfur disproportionation unit passes through the water inlet equipment, is mixed with the wastewater to be treated delivered by the original water inlet equipment in the mixing equipment, and then enters the deep denitrification unit; In the closed sulfur disproportionation unit, the elemental sulfur undergoes a biodisproportionation reaction to form sulfide and sulfate.

3. The sulfur autotrophic denitrification method for coping with environmental condition fluctuations as claimed in claim 1, further comprising the following steps: (4) The effluent total nitrogen and dissolved oxygen data are collected by the effluent intelligent analysis unit installed on the effluent pipe of the deep denitrification unit and sent to the PLC controller. The influent total nitrogen and dissolved oxygen data of the wastewater to be treated are collected by the influent intelligent analysis unit installed at the rear end of the original inlet pump and sent to the PLC controller to adjust the operating parameters of the sulfur disproportionation unit.

4. The sulfur autotrophic denitrification method for coping with environmental condition fluctuations according to claim 3, wherein: The process of adjusting the operating parameters of the sulfur disproportionation unit includes: (41) Determine the design denitrification load capacity of the deep denitrification unit at the design temperature; (42) Determine the relationship between the ratio of sulfur autotrophic denitrification load in the sulfur disproportionation unit and the amount of sulfide produced in the sulfur disproportionation unit; (43) Determine the relationship between the amount of sulfide produced by the sulfur disproportionation unit and the influent flow rate and nitrate concentration of the influent to the sulfur disproportionation unit; (44) Adjust operating parameters through PLC controller: The PLC uses the total nitrogen concentration measured by the outlet intelligent analysis module as the nitrate concentration N, and the total nitrogen concentration measured by the inlet energy analysis module as the inlet nitrate concentration C. i , determine the required denitrification load enhancement ratio A, and then calculate the required sulfide amount M, and calculate the reflux flow rate Q according to the total nitrogen concentration of the effluent, and control the effluent flow rate of the sulfur disproportionation unit, that is, the new water pump flow rate, to be the same as the reflux flow rate Q: Q=[C i -k1×b2×R0×t-b1×R0×t-(1+k1×k3×R0×t)×N)] / k1×k2×R0×t Q——water flow rate of sulfur disproportionation unit, %; C i ——Influent nitrate concentration, mg / L; N——nitrate concentration in the effluent from the deep denitrification unit, mg / L; t——empty bed residence time of deep denitrification unit, h; R0——denitrification load designed for deep denitrification module, kg m -3 d -1 ; k1, k2, k3, b1, b2——parameters.

5. The sulfur autotrophic denitrification method for coping with environmental condition fluctuations according to claim 1, wherein: Alkali solution is provided in the gas recovery module to absorb hydrogen sulfide gas. A pH meter, a hydrogen sulfide monitoring device, a dosing device and a drain valve are provided in the alkaline solution. When the pH is less than 9 or the hydrogen sulfide concentration is higher than 100 mg / L, the drain valve is opened, the alkaline solution in the gas recovery module is input into the mixing device to be mixed with the wastewater to be treated, and the dosing device water pump is started to add an equal amount of alkaline solution from the dosing tank until the pH is greater than 9 and the hydrogen sulfide concentration is lower than 100 mg / L.

6. The sulfur autotrophic denitrification method for coping with environmental condition fluctuations according to claim 1, wherein: A sulfur particle feed port and an observation window are provided on the top of the sulfur disproportionation unit.

7. The sulfur autotrophic denitrification method for coping with environmental condition fluctuations according to claim 1, wherein: The volume ratio of the sulfur disproportionation unit to the deep denitrification unit is 1:4-1:

8.

8. The sulfur autotrophic denitrification method for coping with environmental condition fluctuations according to claim 1, wherein: A backwash water pump is connected to the bottom of the deep denitrification unit. When the actual flow rate of water entering the deep denitrification unit is lower than 90% of the designed flow rate, the deep denitrification unit is flushed by the backwash water pump.

9. The sulfur autotrophic denitrification method for coping with environmental condition fluctuations according to claim 1, wherein: The particle size of the pebbles filled in the water distribution area is 10-20 mm, and the particle size of the sulfur element particles filled in the reaction area is 2-6 mm.

10. The sulfur autotrophic denitrification method for coping with environmental condition fluctuations according to claim 1, wherein: Of the effluent from the deep denitrification unit, the portion transported to the sulfur disproportionation unit via the reflux pump does not exceed 10%.

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