A method for sulfur autotrophic denitrification and nitrogen removal based on dynamic regulation of orthophosphate concentration

Abstract

The application belongs to the technical field of sewage treatment and specifically relates to a sulfur autotrophic denitrification method based on dynamic regulation and control of orthophosphate concentration, which comprises the following steps: monitoring the orthophosphate concentration, nitrate concentration, pH and suspended solid concentration of the water inlet end and water outlet end of a sulfur autotrophic denitrification filter; when the water outlet end nitrate concentration is greater than the design water outlet value and the water inlet end orthophosphate concentration is less than 0.1 mg / L, if the water inlet end suspended solid concentration is less than or equal to the design value, the phosphorus removal agent is reduced; if the water inlet end suspended solid concentration is greater than the design value, the phosphorus removal agent is increased; when the water inlet end orthophosphate concentration is less than 0.1 mg / L, orthophosphate is added; when the water outlet end nitrate concentration is greater than the design water outlet value and the water outlet end orthophosphate concentration reaches the design discharge concentration of the water outlet orthophosphate, the backflow is started and the orthophosphate is supplemented according to the water inlet end orthophosphate concentration; when the water outlet end nitrate concentration is less than the design value, the phosphorus removal agent is increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a sulfur autotrophic denitrification method based on dynamic regulation of orthophosphate concentration. BACKGROUND

[0002] Sulfur autotrophic denitrification technology is an environmentally friendly biological wastewater denitrification process, and its core mechanism is that sulfur-oxidizing bacteria use reduced sulfur as an electron donor to reduce nitrate to nitrogen gas under anoxic conditions. Such reduced sulfur usually has the advantages of high substrate utilization rate, high reduction potential, easy availability, and lower cost compared to heterotrophic denitrification, making sulfur autotrophic denitrification technology highly concerned in the field of water body denitrification. Among them, the autotrophic denitrification biofilter using granular carriers of elemental sulfur compounded with other inorganic compounds as electron donors, referred to as sulfur autotrophic denitrification filter, has become one of the mainstream technologies for deep denitrification. Compared with traditional heterotrophic denitrification, sulfur autotrophic denitrification technology has the advantages of high denitrification efficiency, no need for organic carbon source, low sludge production, low operation cost, and greenhouse gas emission reduction. In recent years, research on related sulfur autotrophic denitrification technology has also increased, mainly focusing on process parameter optimization, environmental inhibition factor analysis, and functional bacterial community analysis. These research results deepen the understanding and recognition of sulfur autotrophic denitrification technology, and provide theoretical support and technical path for optimizing biological denitrification process.

[0003] Sulfur autotrophic denitrification technology shows great potential, but the denitrification effect will be affected by more factors in the actual application process. Past studies have shown that empty bed contact time, water temperature, and influent nitrate load can affect the effect of sulfur autotrophic denitrification. Recent studies have found that orthophosphate, as a necessary component of adenosine triphosphate synthesis, is crucial to maintaining the metabolism of sulfur autotrophic denitrification microorganisms and improving the efficiency of denitrification. When the orthophosphate concentration in the influent is extremely low, the denitrification effect of sulfur autotrophic denitrification will decrease significantly, and even a systematic collapse of denitrification performance may occur. For sulfur autotrophic denitrification filters, which are usually used as deep treatment processes in wastewater treatment plants, the influent is affected by various treatment units in the front end, especially when the temperature is too low in winter, the dosage of coagulants and flocculants increases, which easily causes the orthophosphate concentration of the influent of the sulfur autotrophic denitrification filter to be too low, resulting in a significant reduction in the nitrate removal capacity of the sulfur autotrophic denitrification filter. When the water temperature is high in summer, due to the increased biological activity, excessive denitrification may occur when the orthophosphate in the influent is maintained at a normal level. For example, a sulfur autotrophic denitrification filter with a treatment capacity of 300 m 3 / h, the filter is filled with granular carriers of elemental sulfur compounded with other inorganic compounds, and the total volume of the filter is about 203 m 3The filter pool inlet water is the high-efficiency sedimentation tank outlet water of the domestic sewage treatment plant, and the monitoring period is 3-8 mg / L of nitrate, 0-0.07 mg / L of orthophosphate, 0-2 mg / L of ammonia nitrogen, and 18-29 mg / L of chemical oxygen demand. Since the sewage treatment plant is located in northern China, in order to improve the sedimentation effect of the front-end high-efficiency sedimentation tank in seasonal change, the flocculant dosage is increased, so that the inlet water of the sulfur autotrophic denitrification filter pool faces the phenomenon of serious shortage of orthophosphate concentration, and the outlet water nitrate concentration also has little change, losing the effect of deep denitrification. The phenomenon that the sulfur autotrophic denitrification filter pool cannot work due to the too low orthophosphate concentration of the inlet water seriously affects its popularization and application. SUMMARY

[0004] In order to solve the above problems, the present application, through monitoring the water quality data of the actual water plant, combined with the synchronous regulation of the small test experimental device, aiming at the problem that the influence of the orthophosphate concentration on the denitrification efficiency in the existing sulfur autotrophic denitrification process is not clear and lacks regulation, based on the relevant experimental result verification, a sulfur autotrophic denitrification denitrification method based on dynamic regulation of orthophosphate concentration is proposed.

[0005] The present application aims to provide the following aspects:

[0006] The first aspect of the present application provides a sulfur autotrophic denitrification denitrification method based on dynamic regulation of orthophosphate concentration, comprising the following steps:

[0007] Real-time monitoring of the orthophosphate concentration, nitrate concentration, pH and suspended solid concentration of the inlet and outlet of the sulfur autotrophic denitrification filter pool;

[0008] When the outlet water nitrate concentration is greater than the design outlet value and the inlet water orthophosphate concentration is less than 0.1 mg / L, if the inlet water suspended solid concentration is less than or equal to the design value, gradually reduce the dosing amount of phosphorus removal agent in the phosphorus removal process section to make the inlet water orthophosphate concentration greater than or equal to 0.1 mg / L; if the inlet water suspended solid concentration is greater than the design value, gradually increase the dosing amount of phosphorus removal agent to ensure that the inlet water suspended solid concentration meets the standard, and then evaluate the inlet water orthophosphate concentration; when the inlet water orthophosphate concentration is still less than 0.1 mg / L, add orthophosphate to make the inlet water orthophosphate concentration greater than or equal to 0.1 mg / L, and adjust the pH of the inlet water to 6.5-8.5;

[0009] When the outlet water nitrate concentration is greater than the design outlet value and the outlet water orthophosphate concentration is greater than 0.1 mg / L or the outlet water orthophosphate concentration reaches the design outlet orthophosphate concentration, start the reflux to make part of the outlet water reflux to the inlet, and add orthophosphate according to the inlet water orthophosphate concentration after reflux to ensure that the outlet water nitrate and orthophosphate concentrations meet the standard;

[0010] When the nitrate concentration at the effluent end is less than the design value, the phosphorus removal agent dosage of the phosphorus removal process section is increased, so that the orthophosphate concentration at the influent end is less than 0.1 mg / L.

[0011] Among them, the total phosphorus emission standard of general municipal and industrial sewage plants is ≤0.3 mg / L, the sulfur autotrophic denitrification system has a certain phosphorus removal performance, and the specific control amount is limited to the orthophosphate at the effluent end = 0.3 mg / L; at the same time, the sulfur autotrophic denitrification system generally has a part of the phosphorus removal function while denitrifying, so that the orthophosphate concentration at the effluent end is generally lower than that at the influent end, and when there is reflux, the orthophosphate of the original influent is diluted, so that the orthophosphate needs to be supplemented at the influent end, and the specific dosage is limited to the orthophosphate concentration at the effluent end after reflux 0.3 mg / L.

[0012] As a preferred embodiment of the present application, the design value of the suspended solid concentration at the influent end is set to 50 mg / L according to the autotrophic denitrification biological denitrification fixed bed system technical specification T / CSUC 77-2024, the design value of the nitrate concentration at the effluent end is 1 mg / L-300 mg / L, and the design emission concentration of the orthophosphate at the effluent end is 0.1 mg / L-0.3 mg / L.

[0013] As a preferred embodiment of the present application, the dosage of the orthophosphate is calculated according to the following formula:

[0014] ;

[0015] Among them, M is the dosage of orthophosphate, kg / d; C1 is the orthophosphate concentration at the influent end, mg / L; C2 is the design emission concentration of the orthophosphate at the effluent end, the value range is 0.1 mg / L-0.3 mg / L, and the specific design emission value of the orthophosphate concentration at the effluent end is limited; Q is the influent flow at the influent end of the sulfur autotrophic denitrification filter, m 3 / d; N p is the relative atomic mass of phosphorus element; is the relative molecular mass of the added orthophosphate.

[0016] As a preferred embodiment of the present application, the reflux water amount of the opened reflux is calculated according to the following formula:

[0017] ;

[0018] Among them, Q' is the water flow of the reflux to the influent end when the nitrate concentration at the effluent end of the sulfur autotrophic denitrification filter exceeds the standard, m³ / h; n2 is the effluent nitrate concentration, mg / L; n1 is the nitrate concentration when the standard is reached, 1 mg / L; q is the effluent flow when the effluent nitrate concentration reaches the standard, m³ / h.

[0019] As a preferred embodiment of the present application, the phosphorus removal agent is selected from aluminum sulfate, aluminum chloride, polyaluminum chloride, ferric chloride, ferrous sulfate, polyaluminum ferric chloride, polyferric sulfate or polyacrylamide.

[0020] Further preferably, the phosphorus removal agent is selected from polyaluminum chloride or polyacrylamide.

[0021] In a second aspect of the present application, a sulfur autotrophic denitrification system for implementing the above method is provided, which comprises:

[0022] a sulfur autotrophic denitrification filter;

[0023] a water quality monitoring unit for monitoring the concentrations of orthophosphate, nitrate, pH and suspended solids at the influent end and the effluent end of the sulfur autotrophic denitrification filter in real time;

[0024] a phosphorus removal agent dosing device for dosing the phosphorus removal agent to the phosphorus removal process section;

[0025] an influent end dosing device for dosing orthophosphate to the influent end;

[0026] a reflux pump for refluxing part of the effluent at the effluent end to the influent end; and

[0027] a PLC controller for controlling the water quality monitoring unit, the phosphorus removal agent dosing device, the influent end dosing device and the reflux pump.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] Through the comparison and monitoring of the actual sulfur autotrophic denitrification filter in the water plant and the small-scale test, it is found that the sulfur autotrophic denitrification filter has a sensitivity to the concentration of PO4 3-

[0030] Minimum orthophosphate concentration determination: the experimental gradient sets the influent orthophosphate concentration at 0 mg / L, 0.05 mg / L and 0.1 mg / L. It is found that when the influent orthophosphate concentration is lower than 0.1 mg / L, the system has almost no removal effect on nitrate with a concentration of ≥3 mg / L. When the orthophosphate is ≥0.1 mg / L, the metabolic activity of sulfur autotrophic denitrification microorganisms is significantly restored, which can ensure that the effluent nitrate concentration is maintained below 1 mg / L.

[0031] Denitrification load potential determination: in the PO4 3- ​Under the condition of maintaining at least 0.1 mg / L, the system can tolerate the fluctuation of nitrate concentration, the nitrate concentration of the influent of the sulfur autotrophic denitrification filter can fluctuate between 2 mg / L and 8 mg / L, and the effluent nitrate is stably maintained below 1 mg / L; even if the nitrate concentration is increased to 18 mg / L in the simulation experiment, under the condition of the orthophosphate concentration, the nitrate removal rate can still be more than 90%, and the denitrification load is 0.6 kgN / m3·d, which exceeds the denitrification load 0.3 kgN / m3·d of the conventional design of the sulfur autotrophic denitrification filter.

[0032] In order to realize the denitrification effect regulation of the sulfur autotrophic denitrification filter, a "three-level response, two-way linkage" regulation strategy is constructed.

[0033] Monitoring method: the online water quality monitor is used to monitor the orthophosphate and nitrate concentrations of the influent and effluent of the sulfur autotrophic denitrification filter in real time every day, the influent pH and SS are also detected, and the real-time feedback is fed back to the control end.

[0034] Regulation rule:

[0035] First-level response, i.e., front-end priority regulation: when the effluent nitrate concentration is greater than the design value and the influent orthophosphate is less than 0.1 mg / L, if the SS of the influent of the sulfur autotrophic denitrification filter is less than or equal to the design value, the dosing amount of the phosphorus removal agent such as polyaluminum chloride and polyacrylamide in the front-end phosphorus removal process section is gradually reduced, the endogenous phosphorus in the sewage is fully utilized to make the orthophosphate concentration of the influent of the sulfur autotrophic denitrification filter be greater than or equal to 0.1 mg / L; when it is detected that the SS concentration of the influent of the sulfur autotrophic denitrification filter is greater than the design value, the dosing amount of the phosphorus removal agent is increased in steps to ensure that the SS of the influent of the sulfur autotrophic denitrification filter meets the standard, avoid the blockage of the sulfur autotrophic denitrification filter, and re-evaluate the orthophosphate concentration of the influent of the sulfur autotrophic denitrification filter;

[0036] Second-level response, i.e., end self-dosing: when the orthophosphate is still less than 0.1 mg / L after the first-level regulation, the potassium dihydrogen phosphate is calculated according to formula (1) and added, the orthophosphate concentration of the influent of the sulfur autotrophic denitrification filter is accurately maintained at 0.1 mg / L to 0.3 mg / L, and the pH of the influent of the sulfur autotrophic denitrification filter is adjusted to 6.5 to 8.5 through sodium bicarbonate to maintain the best survival environment of the sulfur autotrophic denitrification microorganism;

[0037] Three-stage response, i.e. reflux compensation and inhibition: when the nitrate concentration at the outlet end is greater than the designed outlet value, and the orthophosphate concentration at the outlet end is greater than 0.1 mg / L or the orthophosphate concentration at the outlet end reaches the designed discharge concentration of the orthophosphate at the outlet end, the reflux is opened according to formula (2), part of Q is refluxed to the water inlet end of the sulfur autotrophic denitrification filter tank, and the required supplemental orthophosphate amount is recalculated according to formula (1), so as to guarantee that the sulfur autotrophic denitrification filter tank outlet meets the discharge standard; when the sulfur autotrophic denitrification filter tank outlet nitrate is less than the designed value, the phosphorus removal agent dosage of the front-end phosphorus removal process section is increased, so that the sulfur autotrophic denitrification filter tank inlet orthophosphate is less than 0.1 mg / L, so as to avoid excessive consumption of the autotrophic denitrification filter material.

[0038] The orthophosphate required to be added in the application is realized by the drug potassium dihydrogen phosphate, and the daily addition amount M is calculated in the following manner:

[0039] Formula (1)

[0040] M - potassium dihydrogen phosphate addition amount, kg / d;

[0041] C1 - inlet end orthophosphate concentration, mg / L;

[0042] C2 - minimum orthophosphate concentration requirement, the value range is 0.1 mg / L to 0.3 mg / L, and the designed discharge value of the outlet orthophosphate concentration is limited;

[0043] Q - sulfur autotrophic denitrification filter tank inlet flow;

[0044] N p - relative atomic mass of phosphorus element;

[0045] - relative molecular mass of potassium dihydrogen phosphate;

[0046] When adjusting pH, the application uses a 5% sodium bicarbonate solution, monitors pH in real time, keeps the water quality environment in a slightly alkaline state with a pH of 6.5 to 8.5, and maintains the stability of sulfur autotrophic denitrification.

[0047] When reflux is required, the reflux water is delivered to the sulfur autotrophic denitrification filter tank inlet end by a water pump, and the reflux water amount Q' is calculated in the following manner:

[0048] Formula (2)

[0049] Q' - water flow rate refluxed to the inlet end when the sulfur autotrophic denitrification filter tank outlet nitrate concentration is greater than the designed value, m³ / h;

[0050] n2 - outlet end nitrate concentration, mg / L;

[0051] n1 - nitrate concentration at the standard, 1 mg / L;

[0052] q - effluent flow rate at the standard for nitrate concentration and orthophosphate, m³ / h.

[0053] Third aspect: cross-process intelligent system integration and process scene expansion

[0054] Cross-process intelligent coordination system

[0055] Hardware expansion, i.e. bidirectional communication module: add a communication module with the front-end phosphorus removal agent dosing device in the PLC controller to realize bidirectional transmission of data instructions.

[0056] Add a "phosphorus removal agent adjustment priority" judgment layer to preferentially select the control path with the lowest cost and make full use of endogenous orthophosphate. Under the condition that the influent suspended solids of the sulfur autotrophic denitrification filter are less than 50 mg / L, the front-end phosphorus removal agent dosage is preferentially reduced, which can not only reduce the phosphorus removal agent dosage, but also reduce the cost of influent orthophosphate supplement.

[0057] High load compatibility: through threshold control, the system can flexibly cope with extreme loads with a nitrate concentration of ≤18 mg / L, and the average denitrification load can reach 0.6 kgN / m³·d, which expands the process application scene.

[0058] The present application has the following characteristics:

[0059] 1. Clearly define the denitrification performance limiting factor to improve denitrification stability

[0060] Significant improvement in denitrification efficiency: through experiments, it is determined that the critical threshold of orthophosphate in the influent of the sulfur autotrophic denitrification filter is 0.1 mg / L. When the concentration is ≥0.1 mg / L, the effluent nitrate concentration can be stably reduced to less than 1 mg / L, and the total nitrogen index of the sulfur autotrophic denitrification system effluent reaches the surface water quality of Class IV water.

[0061] 2. Dynamic control logic, fully utilize endogenous phosphorus in raw water

[0062] Bidirectional linkage, cost reduction and efficiency improvement: when the influent PO4 3- <0.1 mg / L, preferentially link the front-end phosphorus removal process to reduce the dosage of phosphorus removal agent, utilize the endogenous phosphorus in sewage to increase the orthophosphate concentration in the influent of the sulfur autotrophic denitrification filter, and only start the orthophosphate dosage system in the influent of the sulfur autotrophic denitrification filter when adjustment is ineffective, to minimize external agent dependence;

[0063] 3. Precise nitrogen control to avoid excessive consumption of sulfur-based carriers filled in the sulfur autotrophic denitrification system. When the denitrification amount exceeds the design requirement, actively increase the front-end phosphorus removal agent dosage to suppress the orthophosphate in the influent of the sulfur autotrophic denitrification filter to <0.05 mg / L, and reduce the consumption of sulfur autotrophic filler.

[0064] 3. High load processing capacity, expanding application scenarios

[0065] Resistant to extreme loads: Under the condition of orthophosphate > 0.1 mg / L, the system's denitrification load is as high as 0.8 kgN / m³·d, and the removal rate of nitrate is more than 98%, which can cope with fluctuations in water quality conditions.

[0066] The dosing system of the sulfur autotrophic denitrification filter can adjust the pH to 7-9 by sodium bicarbonate, maintain the water environment suitable for sulfur autotrophic denitrification conditions, and maintain denitrification stability.

[0067] 4. Strong project adaptability

[0068] Compatible with existing sulfur autotrophic denitrification filters: simple construction, configuration equipment including online monitoring of water quality monitoring unit of orthophosphate, nitrate, and SS, reflux pump, intelligent dosing device, front-end phosphorus removal process dosing system communication, and no change to the original wastewater treatment process, suitable for existing wastewater plant modification.

[0069] Intelligent control: integrated multi-parameter SS+PO4 3- +NO3 - Trigger logic, realize full-automatic operation, reduce manual intervention.

[0070] 5. Win-win of environmental and economic benefits

[0071] Reduce by-product production: by accurately adding PO4 3- , avoid the increase of chemical sludge production and waste caused by excessive orthophosphate.

[0072] Reduce consumption and increase efficiency: under the premise of not significantly increasing the operation and maintenance cost of the wastewater treatment plant, steadily increase the denitrification amount.

[0073] 6. Multi-index coordination, safe and effective control of effluent

[0074] Dual protection mechanism: in the process of adjusting the orthophosphate of the sulfur autotrophic denitrification filter, the SS concentration is monitored in real time and the dynamic adjustment of polyaluminum chloride and polyacrylamide is adjusted, to ensure that the risk of sulfur autotrophic denitrification filter blockage is controllable;

[0075] 7. Precise feedback mechanism to ensure stable water quality

[0076] The effluent is also monitored for orthophosphate and nitrate concentration to ensure that the effluent water quality meets the requirements. When an anomaly occurs, the reflux system is started in time to protect the receiving water quality from being affected. BRIEF DESCRIPTION OF DRAWINGS

[0077] Figure 1 is a sulfur autotrophic denitrification filter; 1, inlet pipe, 2, inlet overflow weir, 3, outlet pipe;

[0078] Figure 2 yes Figure 1 4. Support layer; 5. Reaction zone; 6. Water collection zone;

[0079] Figure 3 yes Figure 2 Top view;

[0080] Figure 4 This refers to the denitrification effect of wastewater treated by a sulfur autotrophic denitrification filter.

[0081] Figure 5 This refers to the denitrification effect of the pilot-scale device;

[0082] Figure 6 The nitrogen removal load of the pilot-scale device and the sulfur autotrophic denitrification filter;

[0083] Figure 7 The system includes: 7. Sulfur autotrophic denitrification filter modification; 8. Water quality monitoring unit; 9. Phosphorus removal agent dosing device; 10. Inlet dosing device; 11. Return water pump; 12. PLC controller.

[0084] Figure 8 The influent and effluent contain nitrate nitrogen and orthophosphate after the modification of the sulfur autotrophic denitrification filter.

[0085] Figure 9 It is the suspended solids (SS) in the influent and effluent after the sulfur autotrophic denitrification filter was modified. Detailed Implementation

[0086] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0087] This invention achieves, for the first time, a dynamic balance of reagent, energy, and material consumption across the entire process chain of a sulfur autotrophic denitrification system through two major innovations: bidirectional linkage between front-end phosphorus removal and end-end filter, and tiered control including priority adjustment, autonomous dosing, and reflux assurance. Compared to existing technologies, it not only solves the problem of nitrogen removal failure but also breaks through by upgrading the operation mode from "passive remediation" to "active prevention," providing a system solution for deep nitrogen removal in wastewater treatment plants that combines high efficiency, economy, and sustainability.

[0088] The application monitors the nitrate and orthophosphate concentration of the water entering the sulfur autotrophic denitrification filter in real time by setting a water quality monitoring unit at the water inlet end of the sulfur autotrophic denitrification filter, and adjusts the dosing device of the front phosphorus removal process section and the dosing device of the water inlet of the sulfur autotrophic denitrification filter in linkage. When the sulfur autotrophic denitrification filter is in the situation that the orthophosphate concentration is insufficient and the nitrate needs to be further removed, the dosing amount of the front phosphorus removal process section is adjusted first. When the dosing amount is adjusted, the orthophosphate concentration of the water inlet of the sulfur autotrophic denitrification filter still cannot be met, and the orthophosphate concentration is increased by adding chemicals at the water inlet end of the sulfur autotrophic denitrification filter, so as to ensure that the sulfur autotrophic denitrification filter stably plays a role of denitrification. When the nitrate concentration of the water inlet is too low or the sulfur autotrophic denitrification filter does not need to remove more nitrate, the dosing device of the front phosphorus removal process section is adjusted in time to reduce the orthophosphate concentration of the water inlet of the sulfur autotrophic denitrification filter, so as to accurately control the denitrification amount of the sulfur autotrophic denitrification filter and reduce the overconsumption of the carrier, thereby realizing more economical operation. After the above modification, the denitrification effect of the sulfur autotrophic denitrification filter is avoided to decline, the stability of the effluent water quality of the sewage treatment plant is ensured, the water quality safety of the receiving water body is protected, and more economical operation of the sewage treatment plant can be realized

[0089] In the application, the sulfur autotrophic denitrification is driven based on elemental sulfur or a sulfur-based particulate carrier as a substrate, the treatment unit is a deep treatment denitrification unit, and is located at the end of the sewage treatment plant. The required orthophosphate is an inorganic orthophosphate. The sulfur-based particulate carrier is a particulate carrier based on elemental sulfur and other inorganic compounds.

[0090] The following is a specific description of the examples:

[0091] Example 1

[0092] A simulation small test device of the sulfur autotrophic denitrification filter is set in the laboratory, which is a columnar experimental device filled with elemental sulfur S 0 The particulate carrier filler particles compounded with other inorganic compounds have a filling volume of about 825 cm³, and the water inlet is taken from the actual water inlet of the sulfur autotrophic denitrification filter. A long empty bed contact time is adopted at the initial stage to supplement sufficient orthophosphate in the water inlet, so as to ensure that the small test experimental device is successfully biofilm formed. The nitrate, ammonia nitrogen, orthophosphate, COD, pH, dissolved oxygen DO and temperature of the inlet and outlet water are monitored daily. After the biofilm is stably formed and the nitrate removal effect is stable, the empty bed contact time is set to 30 min, and potassium dihydrogen phosphate is added in the water inlet to quantitatively control the orthophosphate concentration in the water inlet. Three orthophosphate gradients of 0 mg / L, 0.05 mg / L and 0.1 mg / L are set, and the nitrate concentration of the outlet water is monitored under these gradients. The removal rate and denitrification load are calculated, and the results are as follows Figure 5 、 Figure 6 .

[0093] The experimental results show that when the reactor is running for 7 days just after the biofilm formation, the device still maintains a certain nitrate removal effect even without additional addition of orthophosphate, which may be because the excess orthophosphate in the influent is adsorbed in the device during the biofilm formation, and can be supplemented to the sulfur autotrophic denitrification microorganisms in a short period during the subsequent operation, thereby maintaining the denitrification effect. However, the removal rate soon decreases rapidly due to the continuous lack of orthophosphate, and finally approaches zero. Then, the orthophosphate concentration in the influent is adjusted to 0.05 mg / L and 0.1 mg / L respectively, and it is found that only when the orthophosphate concentration reaches 0.1 mg / L, the nitrate can be stably removed, and the removal rate is relatively high, and the effluent nitrate is less than 1 mg / L. It can be determined that the orthophosphate concentration of 0.1 mg / L meets the denitrification demand of the sulfur autotrophic denitrification system, and can activate the sulfur autotrophic denitrification microorganisms to play a role.

[0094] Subsequently, further potassium nitrate is added to the influent, and when the small-scale device is running for 25 days, the influent nitrate concentration is increased to 18 mg / L. The effluent nitrate removal rate of the small-scale device decreases, but the denitrification load further increases, which basically reaches the limit under this orthophosphate concentration, and can meet the demand of the actual sulfur autotrophic denitrification filter for denitrification load.

[0095] The above example 1 proves the regulating effect of the influent orthophosphate on the sulfur autotrophic denitrification filter, and determines that the minimum orthophosphate concentration under this operating condition is 0.1 mg / L, which provides a reference for the regulation in actual operation.

[0096] Example 2:

[0097] The existing sulfur autotrophic denitrification filter is modified, as shown in Figure 7 The sulfur autotrophic denitrification filter, a water quality monitoring unit 7, a phosphorus removal agent dosing device 8, an influent end dosing device 9, a reflux water pump 10 and a PLC controller 11 are included. The water quality monitoring unit 7 is used to monitor the orthophosphate concentration, the nitrate concentration, the pH and the suspended solid concentration of the influent end and the effluent end of the sulfur autotrophic denitrification filter in real time. The phosphorus removal agent dosing device 8 is used to add a phosphorus removal agent to the phosphorus removal process section. The influent end dosing device 9 is used to add orthophosphate to the influent end. The reflux water pump 10 is used to reflux part of the effluent at the effluent end to the influent end. The PLC controller 11 is used to control the water quality monitoring unit 7, the phosphorus removal agent dosing device 8, the influent end dosing device 9 and the reflux water pump 10.

[0098] The water quality monitoring unit 7 is composed of a nitrate monitoring module, a orthophosphate monitoring module, a pH monitoring module and an SS detection module, collects the data of nitrate, orthophosphate, pH and SS at the inlet and outlet, and sends the data to the sulfur autotrophic denitrification filter PLC controller 11. The sulfur autotrophic denitrification filter PLC controller 11 communicates with the phosphorus removal agent dosing device 8 of the front-end phosphorus removal process section and the inlet dosing device 9 installed on the sulfur autotrophic denitrification filter inlet pipe branch.

[0099] The parameters of the water quality monitoring unit 7 are set as follows: the design value of the suspended solid SS concentration at the inlet is 20 mg / L, the design value of the nitrate concentration at the outlet is 1 mg / L, and the design value of the orthophosphate concentration at the outlet is 0.3 mg / L. It should be noted that the design value of the suspended solid concentration at the inlet can be 50 mg / L, the design value of the nitrate concentration at the outlet can be 1 mg / L-300 mg / L, and the design value of the orthophosphate concentration at the outlet can be 0.1 mg / L-0.3 mg / L, as long as it meets the requirements within the industry recommended standard. In this experiment, the suspended solid concentration at the inlet is designed to be 20 mg / L, which is better than the industry recommended standard.

[0100] (1) When the sulfur autotrophic denitrification filter is put into operation, the water quality monitoring unit 7 monitors that the nitrate concentration at the outlet is greater than 1 mg / L and the orthophosphate concentration at the inlet is less than 0.1 mg / L, and outputs the instruction to the PLC controller 11:

[0101] Instruction ①: The priority is to judge the SS concentration of the sulfur autotrophic denitrification filter inlet. When the inlet SS concentration is lower than the design concentration 20 mg / L of the sulfur autotrophic denitrification filter inlet, the dosing amount of polyaluminum chloride and polyacrylamide in the front-end phosphorus removal process section is reduced, the polyaluminum chloride dosing amount is adjusted from 350 L / h to 140 L / h, the polyacrylamide dosing amount is adjusted from 10 L / h to 4 L / h, so that the orthophosphate concentration at the inlet is greater than or equal to 0.1 mg / L;

[0102] Instruction ②: When the SS concentration of the sulfur autotrophic denitrification filter inlet presents a trend close to the design concentration 20 mg / L of the sulfur autotrophic denitrification filter inlet, the dosing amount of polyaluminum chloride and polyacrylamide in the front-end phosphorus removal process section is increased, the polyaluminum chloride dosing amount is adjusted from 140 L / h to 220 L / h, the polyacrylamide dosing amount is adjusted from 4 L / h to 7 L / h, and the inlet dosing device of the sulfur autotrophic denitrification filter is started. The dosing amount is calculated according to formula (1);

[0103] Formula (1)

[0104] Wherein, M is the positive phosphate dosage, kg / d; C1 is the influent end positive phosphate concentration, mg / L; C2 is the minimum concentration requirement of positive phosphate, the value range is 0.1 mg / L~0.3 mg / L, and the specific value is limited by the effluent positive phosphate concentration design discharge value; Q is the influent end influent flow of the sulfur autotrophic denitrification filter, m 3 / d; N p is the relative atomic mass of phosphorus element; is the relative molecular mass of the added positive phosphate.

[0105] Instruction ③: After reducing the dosages of polyaluminum chloride and polyacrylamide, when the influent SS concentration of the sulfur autotrophic denitrification filter is higher than the design SS concentration of the sulfur autotrophic denitrification filter by 20 mg / L and the influent end positive phosphate PO4 3- concentration is less than 0.1 mg / L, slowly increase the dosages of polyaluminum chloride and polyacrylamide in the front phosphorus removal process section, maintain the current dosages of polyaluminum chloride and polyacrylamide when the influent SS concentration of the sulfur autotrophic denitrification filter is met, and start the influent end dosing device 9 of the sulfur autotrophic denitrification filter. The positive phosphate dosage is calculated according to formula (1), and the influent end pH is adjusted to 7.0.

[0106] (2) When the nitrate concentration at the effluent end of the sulfur autotrophic denitrification system is higher than the design effluent concentration of the system, and the influent end positive phosphate concentration is less than 0.1 mg / L, execute the above instruction ①;

[0107] When the effluent nitrate concentration exceeds 1 mg / L, and the effluent end positive phosphate concentration is 0.3 mg / L, the PLC controller 11 triggers the backflow pump 10, calculates the backflow flow according to formula (2), starts the backflow pump 10, and backflows part of the effluent to the influent end to ensure that the effluent nitrate nitrogen of the sulfur autotrophic denitrification system meets the discharge standard, and the remaining effluent is discharged according to the original effluent mode;

[0108] Formula (2)

[0109] Q' is the water flow rate backflowed to the influent end when the effluent nitrate of the sulfur autotrophic denitrification filter exceeds the standard, m³ / h;

[0110] n2 is the effluent nitrate concentration, mg / L;

[0111] n1 is the nitrate concentration when it meets the standard, 1 mg / L;

[0112] q is the effluent flow rate when the effluent meets the standard, m³ / h.

[0113] (3) When the effluent detects that the nitrate concentration is less than 1 mg / L, increase the dosages of polyaluminum chloride and polyacrylamide in the front phosphorus removal process section to avoid excessive consumption of the autotrophic denitrification filler.

[0114] After the transformation, the sulfur autotrophic denitrification system can maintain long-term effective denitrification, avoid the destruction of the water quality of the receiving water body, realize the economic operation of multiple indicators and the whole system, and the operation effect after the transformation is as shown in Figure 8 、 Figure 9 On the fourth day of continuous operation, all the transformations were completed, and on the fifth day after the transformation, the sulfur autotrophic denitrification system realized that the effluent was stable < 1 mg / L, the influent SS was stable < 20 mg / L, and the effluent orthophosphate concentration was stable < 0.3 mg / L, which can realize sufficient utilization of the endogenous phosphorus in the sewage, reduce the additional supplement of orthophosphate by more than 65%, and reduce the use amount of the front-end phosphorus removal agent by more than 30%.

[0115] Comparative Example 1

[0116] The project is located in Tianjin, and the sulfur autotrophic denitrification filter with a treatment capacity of 300 m³ / h is as shown in Figures 1-3 , which is sequentially from bottom to top a water collecting area 6, a supporting layer 4, and a reaction area 5. Water distribution is connected through the water inlet pipe 1 and the water inlet overflow weir 2 on both sides. The supporting layer 4 is filled with pebbles, and the reaction area 5 is filled with granular carrier fillers compounded with elemental sulfur and other inorganic compounds, with a filling volume of about 203 m³.

[0117] The sulfur autotrophic denitrification filter is fed with the effluent of the high-efficiency sedimentation tank of the domestic wastewater treatment plant, and an intelligent backwashing device is provided to perform regular backwashing.

[0118] The denitrification effect of wastewater treated by the sulfur autotrophic denitrification filter is shown in Figure 4 , the influent nitrate concentration is 3 mg / L~8 mg / L, the orthophosphate concentration is 0 mg / L~0.07 mg / L, the ammonia nitrogen concentration is 0 mg / L~2 mg / L, the chemical oxygen demand COD is 18 mg / L~29 mg / L, and the effluent nitrate is almost not removed most of the time.

[0119] The above examples are only preferred embodiments of the present application, and are not a limitation on the technical solutions of the present application. Any technical solutions that can be realized on the basis of the above examples without creative labor shall be considered to fall within the protection scope of the present application.

Claims

1. A sulfur autotrophic denitrification method based on dynamic control of orthophosphate concentration, characterized in that, Includes the following steps: Real-time monitoring of orthophosphate concentration, nitrate concentration, pH and suspended solids concentration at the inlet and outlet of the sulfur autotrophic denitrification filter; When the nitrate concentration at the effluent is greater than the design effluent value and the orthophosphate concentration at the influent is less than 0.1 mg / L, if the suspended solids concentration at the influent is ≤ the design value, gradually reduce the dosage of the phosphorus removal agent in the phosphorus removal process section to ensure that the orthophosphate concentration at the influent is ≥ 0.1 mg / L; if the suspended solids concentration at the influent is > the design value, gradually increase the dosage of the phosphorus removal agent to ensure that the suspended solids concentration at the influent meets the standard, and then reassess the orthophosphate concentration at the influent; when the orthophosphate concentration at the influent is still less than 0.1 mg / L, add orthophosphate to ensure that the orthophosphate concentration at the influent is ≥ 0.1 mg / L, and adjust the pH at the influent to 6.5~8.5; When the nitrate concentration at the outlet is greater than the design outlet value and the orthophosphate concentration at the outlet is greater than 0.1 mg / L or the orthophosphate concentration at the outlet reaches the design discharge concentration of orthophosphate, the backflow is activated to allow part of the outlet water to flow back to the inlet. Orthophosphate is then added according to the orthophosphate concentration at the inlet after the backflow to ensure that the nitrate and orthophosphate concentrations at the outlet meet the standards. When the nitrate concentration at the effluent is lower than the design value, increase the dosage of the phosphorus removal agent in the phosphorus removal process section to make the orthophosphate concentration at the influent less than 0.1 mg / L; The design value for the suspended solids concentration at the inlet is 50 mg / L, the design value for the nitrate concentration at the outlet is 1 mg / L to 300 mg / L, and the design discharge concentration for orthophosphate at the outlet is 0.1 mg / L to 0.3 mg / L.

2. The sulfur autotrophic denitrification method based on dynamic control of orthophosphate concentration according to claim 1, characterized in that, The design value for the suspended solids concentration at the inlet is 20 mg / L, the design value for the nitrate concentration at the outlet is 1 mg / L, and the design discharge concentration for orthophosphate at the outlet is 0.3 mg / L.

3. The sulfur autotrophic denitrification method based on dynamic control of orthophosphate concentration according to claim 1, characterized in that, The phosphorus removal agent is selected from any one of aluminum sulfate, aluminum chloride, polyaluminum chloride, ferric chloride, ferrous sulfate, polyaluminum ferric chloride, and polyferric sulfate.

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