Method for enhancing nitrogen and phosphorus removal effect of whole-course autotrophic nitrogen removal system

Abstract

The invention discloses a method for enhancing nitrogen and phosphorus removal effects of a whole-course autotrophic nitrogen removal system, and belongs to the technical field of sewage treatment. According to the method, the steel slag powder and the steel slag particles are applied to a nitrification section and a sulfur autotrophic denitrification section respectively, alkalinity consumed by nitrification is supplemented by adding the steel slag powder in the nitrification section, enrichment of nitrifying bacteria is facilitated, metal ions leached from the steel slag powder improve the ammonia nitrogen removal rate, meanwhile, part of phosphate is removed, and the ammonia nitrogen removal rate is increased. The average removal rate of ammonia nitrogen is 99.75%, and the average removal rate of phosphate is 23.22%. According to the invention, the denitrification potential and denitrification effect of the sulfur autotrophic denitrification section are improved, and when the HRT is 3h, the average 97.04% of total nitrogen and the average 86.4% of total phosphorus can be removed; in the denitrification process, metal ions leached from the steel slag can generate precipitates with phosphate, and H < + > generated in the denitrification process can accelerate erosion of the steel slag, so that the phosphorus removal capacity of the steel slag is improved.

Description

Technical Field

[0001] The invention relates to a method for enhancing the denitrification and dephosphorization effects of a full-process autotrophic denitrification system, and belongs to the technical field of sewage treatment. Background Art

[0002] Wastewater treatment is a major contributor to greenhouse gas emissions. Therefore, choosing to use new low-carbon, environmentally friendly and efficient wastewater treatment technologies can reduce the energy and material consumption of the treatment process, which has a dual benefit effect on "carbon emission reduction" and reducing enterprise operating costs.

[0003] Biological denitrification is a widely used method in the field of sewage treatment due to its advantages such as low cost and no secondary pollution. Traditional biological denitrification includes two steps: nitrification and denitrification. First, nitrifying bacteria oxidize ammonia nitrogen in the water body into nitrite nitrogen and nitrate nitrogen through nitrification, and then denitrifying bacteria reduce nitrite nitrogen and nitrate nitrogen to nitrogen gas through denitrification. The nitrification process generally requires an aeration device to provide an aerobic environment, and the nitrification process requires additional alkalinity, which increases the cost. Denitrifying bacteria are heterotrophic bacteria, but due to the relatively low C / N ratio in urban sewage, additional organic carbon sources are generally required to ensure the complete denitrification reaction, and excessive addition of organic carbon sources will cause secondary pollution. Therefore, the autotrophic denitrification process has received widespread attention. The most widely used autotrophic denitrification process is the sulfur autotrophic denitrification process with elemental sulfur as the electron donor. It generally adopts a fixed bed mode, which is relatively simple to operate and maintain, and has high denitrification efficiency and low cost.

[0004] However, both nitrification and sulfur autotrophic denitrification produce hydrogen ions (H + ), in order to ensure the denitrification efficiency, a large amount of alkalinity needs to be supplemented. In practical applications, limestone is usually used as an alkalinity source and inorganic carbon source in sulfur autotrophic denitrification systems, but the addition of limestone will increase the hardness of the effluent, and the area occupied by limestone cannot provide electrons, which not only does not contribute to denitrification, but may also affect the overall denitrification effect of the system. In addition, the nitrification process and the sulfur autotrophic denitrification process are mainly aimed at nitrogen pollution in sewage, and the removal effect of phosphorus in sewage is poor. Therefore, it is necessary to consider the use of other fillers to supplement alkalinity and enhance phosphorus removal.

[0005] Steel slag is the second largest solid waste in steel production, and its utilization rate is low in my country. Unused steel slag will not only hinder the intensive use of land resources, but also the accumulated steel slag will cause damage to the atmosphere, soil and other environments. Therefore, it is urgent to explore new ways to utilize steel slag resources, improve the utilization rate of steel slag, turn it into treasure, and improve economic benefits. Steel slag has the characteristics of high alkalinity, high hardness, and large specific surface area. It is usually used in heavy metal adsorption, CO2 capture and storage, acidic wastewater treatment and other fields, and can be used as an alkalinity source. In addition, the high content of metal ions in steel slag (such as Ca 2+, Fe 2+ Mg 2+ , Mn 2+ It not only has the potential to promote chemical phosphorus removal, but also can increase the activity of related denitrification functional enzymes, stimulate the secretion of redox substances and electron hopping in extracellular polymers (EPS), accelerate electron transfer, and improve denitrification efficiency.

[0006] Therefore, it is necessary to develop a method that can solve the problems of high alkalinity consumption and poor phosphorus removal effect in the whole autotrophic nitrogen and phosphorus removal process, so as to improve the nitrogen and phosphorus removal effects and achieve sewage treatment in a more low-carbon, environmentally friendly and efficient manner. Summary of the invention

[0007] In order to solve the above problems, the present invention connects nitrification and sulfur autotrophic denitrification processes in series, specifically, steel slag powder and steel slag particles are respectively applied to the nitrification section (SBR reactor) and the sulfur autotrophic denitrification section (cylindrical sulfur autotrophic denitrification filter column), so as to realize efficient and economical nitrogen and phosphorus removal and resource utilization of steel slag by a fully autotrophic process.

[0008] The first object of the present invention is to provide a method for enhancing the denitrification and phosphorus removal effect of a full-process autotrophic denitrification system, wherein the full-process autotrophic denitrification system includes a nitrification section and a sulfur autotrophic denitrification section, wherein steel slag powder is added to the nitrification section; and steel slag particles and sulfur particles are added to the sulfur autotrophic denitrification section.

[0009] In one embodiment, in the nitration stage, the steel slag powder is 400 mesh, and the amount of steel slag powder added is 4.5-6.5 g / L.

[0010] In one embodiment, in the nitration stage, when the reaction system is 4 to 4.5 L, 18 to 25 g of steel slag powder is added (ie, the amount of steel slag powder added is 4.5 to 6.5 g / L), preferably 20 g.

[0011] In one embodiment, in the sulfur autotrophic denitrification stage, the particle size of the steel slag particles is 4 to 8 mm, and the particle size of the sulfur particles is 4 to 8 mm.

[0012] In one embodiment, in the sulfur autotrophic denitrification stage, the volume ratio of slag particles to sulfur particles is 1:1-5, preferably 1:1-3, and more preferably 1:3.

[0013] In one embodiment, the influent in the nitrification stage is artificial simulated water, wherein the artificial simulated water contains 40 mg / L NH4 + -N, 4mg / L PO4 3- -P and 0.6 g / L NaHCO3.

[0014] In one embodiment, the formula of artificial simulated water distribution is: 40 mg / L NH4 +-N, 4mg / L PO4 3- -P, 0.6g / L NaHCO3 and 1mL / L trace elements.

[0015] In one embodiment, the formula of the trace elements is 3g / L MgSO4, 0.5g / L MnSO4, 0.1g / L FeSO4, 0.1g / L CaCl2, 0.1g / L ZnSO4, and 0.1g / L CuSO4.

[0016] In one embodiment, in the nitrification stage, the SS of the inoculated aerobic tank sludge is 2000-3400 mg / L, preferably 3000 mg / L.

[0017] In one embodiment, the aerobic tank sludge is taken from the aerobic tank of Yixing Concept Plant.

[0018] In one embodiment, in the nitrification section, the filler is MBBR filler, and the filling ratio of MBBR filler is 20-40%, preferably 30%.

[0019] In one embodiment, in the nitrification stage, the HRT is set to 2 to 6 hours, preferably 6 hours.

[0020] In one embodiment, the nitrification stage adopts an SBR reactor, and the operation cycle of the SBR reactor is water inlet 5 minutes, aeration and stirring 300 minutes, sedimentation 30 minutes, water outlet 5 minutes, and stagnation 20 minutes.

[0021] In one embodiment, in the nitrification stage, the working volume of the SBR reactor is 4-4.5L, and the inlet and outlet water volumes are both 1-1.5L.

[0022] In one embodiment, the effluent from the nitrification stage is used as the influent of the sulfur autotrophic denitrification stage.

[0023] In one embodiment, in the sulfur autotrophic denitrification stage, the SS of the inoculated sludge is 2000-3000 mg / L.

[0024] In one embodiment, the sludge is taken from the sulfur autotrophic denitrification pilot plant of Yixing Concept Plant.

[0025] In one embodiment, the sulfur autotrophic denitrification stage uses a cylindrical sulfur autotrophic denitrification filter column and adopts upflow continuous water inflow.

[0026] In one embodiment, in the sulfur autotrophic denitrification section, the inner diameter of the cylindrical sulfur autotrophic denitrification filter column is 5 cm, the working height is 30 cm, and the water inlet method is upflow to promote the discharge of nitrogen.

[0027] In one embodiment, in the sulfur autotrophic denitrification stage, the HRT is 1 to 3 hours, preferably 3 hours.

[0028] The second object of the present invention is to provide an application of the above method in denitrification and dephosphorization of sewage.

[0029] The third object of the present invention is to provide a fully autotrophic nitrogen removal and phosphorus removal device, which comprises a nitrification section and a sulfur autotrophic denitrification section, wherein steel slag powder is added to the nitrification section; and steel slag particles and sulfur particles are added to the sulfur autotrophic denitrification section.

[0030] In one embodiment, the main purpose of adding steel slag powder in the nitrification stage is to replenish the alkalinity consumed in the nitrification process. Adding too much steel slag powder may cause excessive release of alkalinity, resulting in a higher pH value, which inhibits the nitrification reaction. At the same time, too high a concentration of metal ions leached from the steel slag may poison nitrifying bacteria and cause the nitrifying bacteria to lyse and die. Therefore, too much steel slag powder should not be added.

[0031] In one embodiment, the main purpose of adding steel slag in the sulfur autotrophic denitrification stage is to deeply treat nitrogen and phosphorus. Compared with steel slag powder, the specific surface area of ​​steel slag particles is smaller, and the metal ions inside them are not easy to be leached. Therefore, the proportion of steel slag particles can be relatively increased, and the H generated in the sulfur autotrophic denitrification process can be further reduced. + It can accelerate the leaching of metal ions inside steel slag and enhance the effect of chemical phosphorus removal.

[0032] Beneficial Effects

[0033] (1) The present invention innovatively combines the industrial waste steel slag with the fully autotrophic denitrification and phosphorus removal process, and utilizes the advantages of the steel slag itself, such as large specific surface area, high alkalinity, and rich metal content, to realize the resource utilization of the steel slag. The test was conducted using artificial simulated water distribution, and good removal effects of pollutants such as nitrogen and phosphorus were achieved.

[0034] (2) After adding steel slag powder to the nitration stage of the present invention, the alkalinity consumed in the nitration process can be effectively supplemented, and the average removal rate of ammonia nitrogen is 99.75%. The metal ions (Ca 2+ / Fe 2+ / Fe 3+ ) can promote chemical phosphorus removal and relieve the phosphorus removal pressure of subsequent processes, with an average phosphate removal rate of 23.22%;

[0035] (3) After adding steel slag to the sulfur autotrophic denitrification stage of the present invention, the alkalinity in the system can be kept stable, and the average removal rate of TN is 97.04%. The average removal rate of TP by the metal ions released from the steel slag is 86.4%, which not only promotes the phosphorus removal performance, but also promotes the growth of functional microorganisms in the system;

[0036] (4) Both the nitrification process and the sulfur autotrophic denitrification process will produce H + , H +It can enhance the erosion of the steel slag surface, promote the release of metal ions and alkalinity inside the steel slag, and promote denitrification and phosphorus removal. Therefore, the application of steel slag in the nitrification-sulfur autotrophic denitrification process can achieve complementary advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a graph showing the removal effect and removal rate change of ammonia nitrogen in the nitrification stage of Example 1.

[0038] Figure 2 This is a graph showing the removal effect and removal rate change of ammonia nitrogen in the sulfur autotrophic denitrification stage of Example 1.

[0039] Figure 3 This is a diagram showing the removal effect of phosphate by nitrification-sulfur autotrophic denitrification in Example 1.

[0040] Figure 4 This is a diagram showing the removal effect of total phosphorus by nitrification-sulfur autotrophic denitrification in Example 1.

[0041] Figure 5 This is a diagram showing the alkalinity change during the nitrification-sulfur autotrophic denitrification process of Example 1.

[0042] Figure 6 This is a process flow chart of nitrification-sulfur autotrophic denitrification according to the present invention. DETAILED DESCRIPTION

[0043] First, the sources of raw materials, technical terms, relevant detection methods / calculation formulas and reaction equations involved in this application are introduced as follows:

[0044] 1. Raw materials involved in the following examples and comparative examples:

[0045] MBBR suspended filler was K3 filler purchased from Sipurun Technology Co., Ltd.

[0046] Steel slag powder (400 mesh) and steel slag particles with a particle size of 4 to 8 mm were purchased from Hebei Jixin Material Technology Co., Ltd.

[0047] Sulfur granules (sulfur) with a particle size of 4 to 8 mm were purchased from Weifang Kaimu Qiangfeng Biotechnology Co., Ltd.

[0048] The sludge inoculated in the present invention can be of different types. The sludge inoculated in the nitrification section is generally taken from the activated sludge in the aerobic tank, and the sludge inoculated in the sulfur autotrophic denitrification section is generally taken from the sludge in the anoxic tank. In the embodiments and comparative examples, specifically: the sludge inoculated in the nitrification section is taken from the activated sludge in the aerobic tank of Yixing Concept Plant; the sludge inoculated in the sulfur autotrophic denitrification section is taken from the sludge of the sulfur autotrophic denitrification pilot plant of Yixing Concept Plant.

[0049] 2. The porosity involved in the embodiment refers to the percentage of the internal pore volume of the cylindrical sulfur autotrophic denitrification filter column after the steel slag particles and the sulfur particles are mixed to the total volume of the steel slag particles and the sulfur particles under natural conditions.

[0050] The nitrification process or complete nitrification process refers to the main reaction in the nitrification section, and the sulfur autotrophic denitrification process refers to the main reaction in the sulfur autotrophic denitrification section.

[0051] The influent in the SBR reactor is artificial simulated water, and the formula of artificial simulated water is: 40mg / L NH4 + -N, 4mg / L PO4 3- -P, 0.6g / L NaHCO3 and 1mL / L trace elements, among which the trace element formula is 3g / LMgSO4, 0.5g / LMnSO4, 0.1g / L FeSO4, 0.1g / L CaCl2, 0.1g / L ZnSO4, 0.1g / L CuSO4.

[0052] 3. Detection method / calculation formula

[0053] Ammonia nitrogen removal rate (%) = (influent ammonia nitrogen concentration - effluent ammonia nitrogen concentration) / influent ammonia nitrogen concentration × 100%;

[0054] Total nitrogen removal rate (%) = (influent total nitrogen concentration - effluent total nitrogen concentration) / influent total nitrogen concentration × 100%;

[0055] Nitrate nitrogen removal rate (%) = (influent nitrate nitrogen concentration - effluent nitrate nitrogen concentration) / influent nitrate nitrogen concentration × 100%;

[0056] Nitrification stage phosphate removal rate (%) = (influent phosphate concentration - nitrification stage effluent phosphate concentration) / influent phosphate concentration × 100%;

[0057] Total phosphorus removal rate of nitrification stage (%) = (total phosphorus concentration of influent - total phosphorus concentration of effluent of nitrification stage) / total phosphorus concentration of influent × 100%;

[0058] Sulfur autotrophic denitrification section phosphate removal rate (%) = (sulfur autotrophic denitrification section influent phosphate concentration - sulfur autotrophic denitrification section effluent phosphate concentration) / sulfur autotrophic denitrification section influent phosphate concentration × 100%;

[0059] Total phosphorus removal rate of sulfur autotrophic denitrification section (%) = (total phosphorus concentration of sulfur autotrophic denitrification section influent - total phosphorus concentration of sulfur autotrophic denitrification section effluent) / total phosphorus concentration of sulfur autotrophic denitrification section influent × 100%;

[0060] Nitrification potential: 500mL of nitrification sludge was aerated and the dissolved oxygen was maintained at 3-5mg / L; 5mL of 12g / L ammonium chloride solution and 5mL of 12g / L sodium bicarbonate solution were added in sequence; the ammonia nitrogen concentration in the solution was measured every 10 minutes; a linear regression was performed based on the change in the ammonia nitrogen concentration in the solution (with time as the horizontal axis and ammonia nitrogen concentration as the vertical axis), and the nitrification rate curve of the activated sludge was obtained, and the nitrification potential of the system can be calculated based on the sludge concentration of the sludge system.

[0061] Nitrification potential = -slope / VSS (mg NH4 + -N / g VSS h)

[0062] Denitrification potential: At the end of each stage, the denitrification potential of the microorganisms in the cylindrical filter column was determined. The specific steps were as follows: 100 mL of filler was taken from the column and placed in a beaker. Simulated wastewater mainly containing 50 mg / L nitrate nitrogen and 0.7 g / L sodium bicarbonate was added. The mixture was placed in an oscillator and oscillated at 30 °C and 150 rpm. 10 mL of water sample was taken every 10 minutes to determine the nitrate nitrogen content in the solution. The denitrification potential value (DP) was obtained by linear analysis. The calculation formula is as follows:

[0063] DP(denitrification potential)=K×V R / V T

[0064] Where: K is the slope of the straight line obtained by linear analysis (mg NO3 - -N / L·h), VR is the volume of water added (L), VT is the volume of filler and biofilm taken (L).

[0065] The alkalinity (inlet alkalinity, nitrification section outlet alkalinity, total outlet alkalinity) is analyzed by titration.

[0066] Ammonia nitrogen concentration, nitrate nitrogen concentration, total nitrogen concentration, phosphate concentration, and total phosphorus concentration were analyzed by ultraviolet spectrophotometry.

[0067] 4. Equations for complete nitrification and sulfur autotrophic denitrification processes

[0068] The reaction equation for the complete nitration process is:

[0069] NH4 + +2O2→NO3 - +2H + +H2O

[0070] The reaction equation of elemental sulfur autotrophic denitrification process is:

[0071] 55S+20CO2+50NO3- +38H2O+4NH4 + →4C5H7O2N+25N2+55SO4 2- +64H +

[0072] Example 1: A method for enhancing the nitrogen and phosphorus removal effect of the whole autotrophic nitrogen removal system

[0073] A method for enhancing the nitrogen removal and phosphorus removal effect of a full-process autotrophic nitrogen removal system, specifically comprising:

[0074] (1) Build a full-process autotrophic denitrification system (start-up phase)

[0075] The whole autotrophic denitrification system comprises a nitrification section and a sulfur autotrophic denitrification section, and steel slag powder (400 meshes) and steel slag particles (4-8 mm) are respectively applied to the nitrification and sulfur autotrophic denitrification stages.

[0076] The nitrification section is realized by an SBR reactor with a working volume of 4.5L and an inlet and outlet volume of 1.2L. The aerobic tank sludge is inoculated and MBBR suspended filler is added. The SS of the inoculated sludge is 3000mg / L, the filling ratio of the MBBR filler is 30%, and the HRT is 6h, including 5min of water inlet, 5h of aeration and stirring, 30min of sedimentation, 5min of water outlet, and 20min of stagnation stage. Steel slag powder (400 mesh) is added to the SBR reactor, and the powder addition amount is 20g. Under the condition of aerobic aeration, the steel slag powder can be mixed with the flocculent sludge and suspended in the reactor. The effluent from the nitrification section is used as the inlet of the sulfur autotrophic denitrification section.

[0077] The sulfur autotrophic denitrification section is carried out in a cylindrical sulfur autotrophic denitrification filter column, and 4-8 mm steel slag particles and sulfur particles (4-8 mm) are completely mixed as an autotrophic denitrification functional layer, wherein the volume ratio of sulfur particles to steel slag particles is 1:3 (porosity is 46%); the inner diameter of the cylindrical sulfur autotrophic denitrification filter column is 5 cm, the working height is 30 cm, the HRT is 3 h, and the water inlet method adopts an upflow type to promote the discharge of nitrogen.

[0078] The nitrification section is inoculated with 4L of aerobic tank activated sludge (SS is about 3000mg / L), and MBBR suspended filler (filling ratio is 30%) is added and pumped into the SBR reactor; the sulfur autotrophic denitrification section is inoculated with 50mL of sulfur autotrophic denitrification pilot plant sludge (SS is about 2500mg / L) and pumped into the cylindrical sulfur autotrophic denitrification filter column;

[0079] Water was introduced into the SBR reactor of the nitrification section, and subsequent experiments were started after the nitrogen and phosphorus concentrations of the effluent were stable and the sludge acclimation was completed;

[0080] (2) Wastewater treatment

[0081] Water was continuously fed into the SBR reactor of the nitrification section for a total of 35 days. Samples were taken every 5 days to test the concentrations of ammonia nitrogen, nitrate nitrogen, total nitrogen, phosphate, and total phosphorus in the inlet and outlet water of the nitrification section and the sulfur autotrophic denitrification section.

[0082] Throughout the process, the working principle of the full autotrophic denitrification system is as follows:

[0083] Nitrification section: Under the condition of aeration and stirring (dissolved oxygen is 2-4 mg / L), steel slag powder can be mixed with flocculent sludge and MBBR suspended filler and suspended in the SBR reactor. The nitrifying bacteria attached to the flocculent sludge and MBBR suspended filler will convert the ammonia nitrogen in the influent into nitric nitrogen during aeration and stirring; after precipitation, the steel slag powder will settle at the bottom of the SBR reactor together with the flocculent sludge, which is beneficial to the subsequent effluent water quality clarification; the nitrification section can realize the removal and conversion of ammonia nitrogen, and the steel slag powder can supplement the alkalinity consumed in the nitrification process to ensure the normal progress of the nitrification process. The metal ions released by the steel slag can promote the formation of biofilm, which is beneficial to the enrichment of nitrifying bacteria. The metal ions released by the steel slag powder can also promote chemical phosphorus removal and alleviate the phosphorus removal pressure in the subsequent sulfur autotrophic denitrification process section;

[0084] Sulfur autotrophic denitrification section: The effluent from the nitrification section is used as the inlet water for the cylindrical sulfur autotrophic denitrification filter column of the sulfur autotrophic denitrification section. The inlet water adopts upflow continuous water inlet to promote the discharge of nitrogen, and the cylindrical sulfur autotrophic denitrification filter column is controlled to be anoxic. The sulfur autotrophic denitrification section can achieve deep removal of total nitrogen and total phosphorus. The added steel slag particles can supplement the alkalinity on the one hand to ensure the realization of the sulfur autotrophic denitrification process. On the other hand, the metal ions leached from the steel slag particles can also achieve chemical removal of total phosphorus.

[0085] Comparative Example 1: No steel slag powder was added in the nitrification stage

[0086] Specific implementation method is the same as Example 1, except that no steel slag powder is added in the nitrification stage to investigate the influence on the denitrification and phosphorus removal effects of the whole autotrophic denitrification system.

[0087] Comparative Example 2: No steel slag particles were added to the denitrification stage

[0088] Specific implementation method is the same as Example 1, except that no steel slag particles are added to the denitrification stage to investigate the effect on the denitrification and phosphorus removal effects of the full autotrophic denitrification system.

[0089] The total operation time was 35 days. Samples were taken every 5 days to test relevant indicators, and the average value after multiple sampling was calculated as the processing result.

[0090] Denitrification effect of the whole autotrophic denitrification system:

[0091] The denitrification results of the nitrification stage in Example 1 are as follows: Figure 1The effects of adding slag powder to the nitration stage in Example 1 and Comparative Example 1 on the relevant indicators of the stage are shown in Table 1:

[0092] Table 1

[0093]

[0094] Depend on Figure 1 From Table 1, we can see that:

[0095] In Example 1, the nitrification stage can achieve complete oxidation of ammonia nitrogen, and the ammonia nitrogen is almost completely converted into nitrate nitrogen by nitrifying bacteria, and the average removal rate of ammonia nitrogen is 99.75%; since the nitrification process requires the consumption of alkalinity, no steel slag powder is added in Comparative Example 1, and the alkalinity cannot be supplemented, and the removal rate of ammonia nitrogen is only 80.62%.

[0096] In Example 1, the steel slag powder added to the nitrification stage can replenish the alkalinity consumed in the nitrification process, so that the system pH is maintained in a suitable range for the growth and metabolism of nitrifying bacteria, which is conducive to the nitrification reaction. Therefore, its ammonia nitrogen removal rate is relatively high, averaging 99.75%; the nitrification potential in Example 1 is also improved synchronously.

[0097] The denitrification results of the sulfur autotrophic denitrification section in Example 1 are as follows: Figure 2 The results of the effects of adding steel slag particles to the sulfur autotrophic denitrification section in Example 1 and Comparative Example 2 and not adding steel slag powder to the nitrification section in Comparative Example 1 on the relevant indicators of this section are shown in Table 2:

[0098] Table 2

[0099]

[0100] In Example 1, the sulfur autotrophic denitrification stage can achieve deep removal of total nitrogen. After adding steel slag, the average removal rate of nitrate nitrogen is as high as 98.88%, and the average removal rate of total nitrogen can reach 97.04%; however, since the sulfur autotrophic denitrification process consumes a large amount of alkalinity, insufficient influent alkalinity will inhibit the progress of sulfur autotrophic denitrification and lead to the accumulation of nitrite nitrogen. Therefore, in Comparative Example 2, the average removal rate of nitrate nitrogen is only 58.31%, and the average removal rate of total nitrogen is only 50.31%.

[0101] The average nitrogen concentration of the effluent of Example 1 is 1.12 mg / L, which can meet the Class A emission standard (15 mg / L), while the average nitrogen concentration of the effluent of Comparative Example 2 is 20.88 mg / L, which cannot meet the Class B emission standard (20 mg / L);

[0102] The pH in the sulfur autotrophic denitrification filter column of Example 1 can be maintained within the appropriate range for the growth and reproduction of sulfur autotrophic bacteria, while the pH in the pure sulfur column (Comparative Example 2) is lower, only 5.39, which inhibits the activity of sulfur autotrophic denitrification-related functional bacteria. Therefore, the denitrification potential of Comparative Example 2 is poor, and the total nitrogen removal rate is relatively low.

[0103] In Comparative Example 1, since no steel slag powder was added to the nitrification stage, insufficient alkalinity would result in the inability to effectively remove ammonia nitrogen in the nitrification stage, and the presence of ammonia nitrogen would have a toxic effect on subsequent sulfur autotrophic denitrifying bacteria. Therefore, the average removal rate of nitrate nitrogen in Comparative Example 1 was only 93.82%, and the denitrification potential also dropped to 18.78 mg NO3. - -N / g VSS·h, while ammonia nitrogen cannot be effectively removed in the filter column and will be carried out with the effluent, resulting in a high effluent nitrogen concentration. The average removal rate of total nitrogen is only 73.53%.

[0104] In Example 1, adding steel slag to the sulfur autotrophic denitrification filter column can improve the denitrification potential of the system. The main reason is that the leaching of metal ions in the steel slag can promote denitrification. Studies have found that low concentrations of Fe 2+ Can effectively promote TDS (TDS = H2S + HS - +S 2- ) and NO3 - -N removal; Ca 2+ It can also promote electron transfer and bacterial metabolic activity and significantly enhance nitrate removal performance. Therefore, the denitrification potential of the sulfur autotrophic denitrification section in Example 1 is higher than that of the pure sulfur autotrophic denitrification section in Comparative Example 1 and Comparative Example 2.

[0105] In addition, by Figure 5 From Table 1, we can see that:

[0106] After steel slag is added into the SBR reactor and the sulfur autotrophic denitrification filter column, the alkalinity consumed by the nitrification section and the sulfur autotrophic denitrification section is effectively supplemented, thereby strengthening the removal of nitrogen by the whole autotrophic denitrification system.

[0107] According to the equations of complete nitrification and sulfur autotrophic denitrification, it is known that 7.14 grams of alkalinity is required to completely convert each gram of ammonia nitrogen into nitrate nitrogen, while 4.57 grams of alkalinity is required to completely reduce each gram of nitrate nitrogen by elemental sulfur autotrophic denitrification. Therefore, in theory, each cycle of the nitrification section requires 76.16 mg of alkalinity, and the sulfur autotrophic denitrification section requires 182.8 mg of alkalinity. However, the average influent alkalinity is only 166.2 mg / L, which is insufficient to support the consumption of nitrification and sulfur autotrophic denitrification processes. The addition of steel slag provides sufficient alkalinity in both the nitrification section and the sulfur autotrophic denitrification section, ensuring the realization and stability of complete denitrification, making the average alkalinity of the nitrification section effluent 116.2 mg / L and the average alkalinity of the total effluent 96.8 mg / L.

[0108] Phosphorus removal effect of the whole autotrophic nitrogen removal system:

[0109] The phosphorus removal results of the nitrification stage in Example 1 are as follows: Figure 3 The effects of adding steel slag powder to the nitration stage in Example 1 and Comparative Example 1 on the relevant indicators of the stage are shown in Table 3:

[0110] Table 3

[0111]

[0112] The phosphorus removal results of the sulfur autotrophic denitrification section in Example 1 are as follows: Figure 4 The effects of whether steel slag particles are added to the sulfur autotrophic denitrification section in Example 1 and Comparative Example 2, and whether steel slag powder is not added to the nitrification section in Comparative Example 1 on the relevant indicators of the sulfur autotrophic denitrification section are shown in Table 4:

[0113] Table 4

[0114]

[0115] Depend on Figure 3 , Figure 4 , Table 3 and Table 4 show that:

[0116] In Example 1, steel slag can achieve enhanced removal of phosphorus, where the average removal rate of phosphate in the nitrification stage is 23.22%, and the average removal rate of phosphate in the sulfur autotrophic denitrification stage is 92.83%. The removal of phosphorus by steel slag mainly depends on the leached metal ions (such as Ca 2+ / Fe 2+ / Fe 3+ etc.) come into contact with phosphates to produce precipitation.

[0117] Compared with Example 1, the nitrification section in Comparative Example 1 has almost no removal of phosphorus, and the removal of phosphorus mainly depends on the sulfur autotrophic denitrification section. The average removal rate of phosphate by steel slag particles in the sulfur autotrophic denitrification filter column is 86.28%, which shows that the partial removal of phosphorus in the nitrification section in Example 1 mainly depends on the chemical precipitation of metal ions leached from the steel slag and phosphorus. H generated by nitrification + It can promote the corrosion of the steel slag surface and improve the leaching of metal ions inside the steel slag, thereby achieving a partial phosphorus removal effect. Since the steel slag powder has a large specific surface area, in order to avoid excessive alkalinity release caused by excessive addition of steel slag powder and excessive metal ion leaching concentration inhibiting the nitrification process, the SBR reactor in Example 1 only adds a small amount of steel slag powder to maintain sufficient system alkalinity and ensure complete conversion of ammonia nitrogen.

[0118] Compared with Example 1, the average removal rate of phosphorus by the sulfur autotrophic denitrification filter column in Comparative Example 2 is lower. This shows that the partial removal of phosphorus by the sulfur autotrophic denitrification filter column in Example 1 also mainly relies on the chemical precipitation of metal ions leached from the steel slag and phosphorus, but is limited by the low solubility of the steel slag itself. The leaching of metal ions in the sulfur autotrophic denitrification filter column mainly relies on the H generated by the sulfur autotrophic denitrification. + Corrosion on the surface of steel slag.

[0119] According to the emission standards for urban sewage treatment plants, the first-level A emission standard for total phosphorus is 0.5 mg / L. The final effluent phosphorus average concentration of Example 1 is 0.25 mg / L, which reaches the first-level A emission standard; the effluent phosphorus concentration of Comparative Example 1 is 0.68 mg / L on average, which cannot reach the first-level A standard (0.5 mg / L); and the final effluent phosphorus concentration of Comparative Example 2 is 3.83 mg / L on average, which only reaches the third-level standard (5 mg / L), and cannot achieve standard emission.

[0120] Comparative Example 3: Effect of the volume ratio of sulfur particles to steel slag particles in the denitrification stage on the denitrification and phosphorus removal effects of the full autotrophic denitrification system

[0121] The specific implementation method is the same as Example 1, except that the volume ratio of sulfur particles to steel slag particles is adjusted to 1:1, 1:2, and 1:5, and the influence on the denitrification and phosphorus removal effects of the full autotrophic denitrification system is investigated.

[0122] Under different volume ratios of sulfur particles to slag particles, the results of relevant indicators are shown in Table 5 and Table 6:

[0123] Table 5

[0124]

[0125] Table 6

[0126]

[0127] It can be seen from Tables 5 and 6 that when the volume ratio of sulfur particles to steel slag particles is 1:1 (porosity is 40%) and 1:2 (porosity is 43%), the total nitrogen removal rate is above 94% on average, which can achieve effective reduction of nitrogen, and the average concentration of effluent nitrogen can also reach the Class A discharge standard (15 mg / L), but the removal rate of total phosphorus is relatively low. When the volume ratio is 1:1 and 1:2, the average removal rate of total phosphorus is 62.38% and 80.77% respectively, and the average concentration of effluent phosphorus is 1.52 and 0.79 mg / L respectively. Only when the volume ratio is 1:2 can the effluent reach the Class B standard (1 mg / L);

[0128] When the volume ratio of sulfur particles to slag particles is 1:5 (porosity is 48%), the average effluent nitrogen concentration can only reach the first level B standard (20 mg / L), and the average effluent phosphorus concentration can only reach the second level standard (3 mg / L).

[0129] Comparative Example 4: Effects of different HRTs in the denitrification stage on the nitrogen removal and phosphorus removal effects of the full autotrophic denitrification system

[0130] Specific implementation method is the same as Example 1, except that the HRT of the sulfur autotrophic denitrification section is adjusted to 1h and 2h to examine the influence on the denitrification and phosphorus removal effects of the whole autotrophic denitrification system.

[0131] Table 7

[0132]

[0133] Table 8

[0134]

[0135] It can be seen from Table 7 and Table 8 that the reduction of HRT increases the influent load, and the average removal rates of total nitrogen and total phosphorus decrease. When the HRT is 2h, the average removal rate of total nitrogen is 88.26%, and the average concentration of effluent nitrogen is 4.48mg / L, which can meet the first-level A discharge standard (15mg / L), but the average removal rate of total phosphorus is 72.18%, and the average concentration of effluent phosphorus is 1.04mg / L, which can only meet the second-level discharge standard.

[0136] After further adjusting the HRT to 1h, the average removal rates of total nitrogen and total phosphorus decreased significantly. The average effluent nitrogen concentration was 20.56mg / L, which could not meet the Level 1 B emission standard (20mg / L). The average effluent phosphorus concentration was 2.03mg / L, which could only meet the Level 2 emission standard (3mg / L).

[0137] Comparative Example 5: Adding steel slag particles in the nitrification stage

[0138] The specific implementation is the same as that of Example 1, except that steel slag particles are added to the nitrification stage instead of steel slag powder.

[0139] Results: After adding steel slag particles to the nitrification stage, aeration prevented them from being suspended. The steel slag particles all sank to the bottom of the SBR reactor, which was not conducive to the reaction with the H generated by the nitrification process. + Contact may also cause damage to the machine.

[0140] Comparative Example 6: Adding steel slag powder and sulfur particles in the denitrification stage

[0141] The specific implementation is the same as that of Example 1, except that steel slag powder and sulfur particles are added to the denitrification stage instead of steel slag particles and sulfur particles.

[0142] Results: After adding steel slag powder and sulfur particles to the denitrification section, the overall porosity was too small, which would cause internal blockage and the incoming water could not be pumped in.

[0143] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for enhancing the denitrification and phosphorus removal effect of a full-process autotrophic denitrification system, characterized in that: The whole autotrophic denitrification system comprises a nitrification section and a sulfur autotrophic denitrification section, wherein steel slag powder is added to the nitrification section, and steel slag particles and sulfur particles are added to the sulfur autotrophic denitrification section.

2. The method according to claim 1, characterized in that In the nitration stage, the steel slag powder is 400 mesh, and the addition amount of the steel slag powder is 4.5-6.5 g / L.

3. The method according to claim 1, characterized in that In the sulfur autotrophic denitrification section, the particle size of the steel slag particles is 4 to 8 mm, and the particle size of the sulfur particles is 4 to 8 mm.

4. The method according to claim 1, characterized in that: In the sulfur autotrophic denitrification section, the volume ratio of steel slag particles to sulfur particles is 1:1-3.

5. The method according to claim 1, characterized in that: The influent in the nitrification section is artificial simulated water, which contains 40 mg / L NH4 + -N, 4mg / L PO4 3- -P and 0.6 g / L NaHCO3.

6. The method according to claim 1, characterized in that In the nitrification stage, the HRT is 2 to 6 hours.

7. The method according to claim 1, characterized in that In the sulfur autotrophic denitrification section, the HRT is 1 to 3 hours.

8. The method according to claim 1, characterized in that: In the nitrification section, the SS of the inoculated sludge is 2000-3400 mg / L; in the sulfur autotrophic denitrification section, the SS of the inoculated sludge is 2000-3000 mg / L.

9. Application of the method according to claims 1 to 8 in denitrification and dephosphorization of sewage.

10. A fully autotrophic nitrogen and phosphorus removal device, characterized in that: The fully autotrophic nitrogen removal and phosphorus removal device comprises a nitrification section and a sulfur autotrophic denitrification section, wherein steel slag powder is added to the nitrification section; and steel slag particles and sulfur particles are added to the sulfur autotrophic denitrification section.

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