Method for improving biological sulfate removal efficiency

Abstract

The invention belongs to the technical field of biological environmental protection, and relates to a method for improving biological sulfate removal efficiency. According to the process, sulfate is better removed through multiple stages, pH adjustment of inlet water is combined with addition of zero-valent iron in the three-stage A bioreactor, FeS precipitation is generated by the zero-valent iron and S < 2-> ions in the system, a large number of S < 2-> ions are removed, meanwhile, the reaction efficiency of sulfate reducing bacteria is promoted, and conversion of sulfate radicals is improved; the dissolved oxygen concentration is controlled in the aerobic tank, sulfur ions are converted, S2-and SO4 < 2-> ions in water are further removed, and the sulfate radical removal rate of final effluent can be larger than or equal to 90%.

Description

Technical Field

[0001] The invention belongs to the technical field of biological environmental protection and relates to a method for improving the efficiency of biological sulfate removal. Background Art

[0002] Among the numerous industrial wastewaters, sulfate wastewater is one of the most polluting and harmful. Sulfate wastewater has a wide range of sources and complex components. It can be divided into two categories based on whether it contains organic matter: the first type of wastewater contains a large amount of sulfate and high-concentration organic matter, such as food and amino acid industrial wastewater, pharmaceutical industrial wastewater and some chemical industrial wastewater; the second type of wastewater also contains a large amount of sulfate, but almost no organic matter, mainly including acidic mining wastewater, metallurgical industrial wastewater, seawater and brackish water and some chemical industrial wastewater.

[0003] With the increase in the application of agricultural fertilizers (ammonium sulfate) and the discharge of large amounts of industrial wastewater from some factories, the sulfate content in groundwater in some areas has changed greatly. The discharge of large amounts of sulfate will cause great harm and will cause mineralization of the receiving water body; the sulfate dissolved in the water will cause sulfation of the free lime in the cement, corroding the concrete; the sulfate in the water will produce reverse sulfidation when it is in anoxic state, and its product H2S will corrode the drainage pipes. In addition, the sulfate in the water is the main nutrient source for the rapid growth of anaerobic sludge, and it is also easy to cause other metal ions, especially heavy metal ions, to dissolve in the water. Once there is too much sulfur in the water, it will be ingested by the human body, causing diarrhea and gastroenteritis, which seriously threatens human survival and development. In addition, acid rain can easily corrode metal materials, house buildings, cotton and chemical fiber fabrics, leather and paper products, causing their epidermis to peel off, fade and be damaged, and can also cause plant leaves to turn yellow or even die.

[0004] With the development of society, sulfate pollution control has become an urgent problem to be solved. The research and development of new technologies have shown broad prospects for the treatment of sulfate-containing bodies. In order to ensure the safety of water resources, clean production processes that treat water from the source are the direction of future development.

[0005] At present, sulfate wastewater treatment methods can be divided into two categories: one is containing a large amount of sulfate but less organic matter, this type of water mainly uses chemical precipitation and electrodialysis methods, these methods are costly, and will produce a large amount of hazardous waste, causing secondary pollution. The other type of wastewater has a high content of sulfate and organic matter, and this type of wastewater is particularly suitable for sulfate removal using biological methods; and biochemical processes as its core technology are being studied more and more deeply.

[0006] However, the biological treatment methods in the prior art are not ideal due to various limitations, including (1) the reaction efficiency of anaerobic sludge is generally poor, and a large amount of sulfate ions are not converted; (2) the S produced by anaerobic sludge 2- The ions are unstable and may form H2S gas to pollute the environment, or be converted into SO4 in the subsequent process. 2- ions, the entire treatment process fails. Therefore, how to stably and effectively remove SO4 from wastewater 2- Ions become a problem that needs to be solved urgently. Summary of the invention

[0007] In view of the problems in the prior art, the present invention provides a method for improving the efficiency of biological sulfate removal. The process uses anaerobic sludge as the main biological agent and adopts the AAAO process to remove sulfate in water.

[0008] The technical solution of the present invention includes: A method for improving the efficiency of biological desulfurization, the method is specifically an AAAO process, wherein: (1) Add anaerobic sludge to the AAA bioreactor and control its initial volume concentration to 5% to 10% to convert SO4 2- Restore to S 2- ion; (2) Adding Fe to the AAA bioreactor 0 , control the Fe content in each level of A 0 Concentration 50~300 mg / Ld. Within this range, zero-valent iron can be used very well. If the amount is less than the above, the effect is poor. If the amount is more than the above, zero-valent iron cannot be used, resulting in serious waste and affecting the treatment effect of the entire anaerobic system.

[0009] Preferably, a regulating tank is provided before the AAAO process to adjust the pH of the influent to 5.5-6.5.

[0010] More preferably, the pH of the first stage A is strictly controlled at 5.5-6.5, and sulfuric acid, sodium hydroxide and other pH regulators commonly used in the art can be added for adjustment.

[0011] Preferably, the aerobic tank O bioreactor is slightly aerated, and its dissolved oxygen concentration is controlled at 1.0-1.5 mg / L to remove the S produced in the AAA bioreactor. 2- The ions are gradually oxidized into sulfur and adsorbed into the sludge for removal. When the dissolved oxygen concentration exceeds the upper limit, sulfide cannot be converted into sulfur but sulfate.

[0012] Preferably, in the AAA bioreactor, COD (mg / L): SO4 2- (mg / L) = 0.7~1.5: 1. It can reduce sulfate ions with maximum efficiency.

[0013] Preferably, in order to improve the conversion efficiency of anaerobic sludge, the dissolved oxygen content of the three-stage A is strictly controlled, and the specific control parameters are: the dissolved oxygen content in the first stage A is 0.3-0.7 mg / L; the dissolved oxygen content in the second stage A is 0.1-0.3 mg / L; the dissolved oxygen content in the third stage A is 0.3-0.7 mg / L.

[0014] Preferably, the carbon source is supplemented according to the water inflow, and the supplemented carbon source is a combination of glucose and ethanol. More preferably, the mass ratio of glucose to ethanol is 10:1 to 20:1.

[0015] Preferably, the carbon source is added to the water COD (mg / L) and SO4 2- (mg / L) ratio is 0.7~1.5:1.

[0016] Preferably, in order to better remove sulfate, the hydraulic retention time of each stage should be strictly controlled. The specific control parameters are: the hydraulic retention time (HRT) of each level A is 1.0-1.5 d; the hydraulic retention time (HRT) of O is 0.5-2.0 d.

[0017] In addition, an induced draft system can be set up in each biological reaction of the AAAO process to collect and organize the generated biological waste, including H2S, so as to improve the biological reaction efficiency of each process section, protect the on-site environment, and meet the requirements of biological environmental protection.

[0018] The anaerobic sludge described in the present invention is conventional activated sludge with sulfate reduction in the art, and its form and contained bacteria are not specifically limited, and it can be homemade or commercially available anaerobic granular sludge, etc. In addition to the above-mentioned processes, other processes not described are all completed using existing technologies.

[0019] The beneficial effects of the present invention are: In the AAAO process of the present invention, after the anaerobic reaction in the first stage A, the conditions in the second stage A are more suitable for the growth and action of sulfate-reducing bacteria, and at the same time, 2- The ion generation is greater, which is more beneficial to powder Fe 0 dissolution and reaction, it can be said that the second stage A is the main action area, and the third stage A plays a supplementary reaction role; however, in the AAO process of the prior art, the anaerobic state in the first stage A is not sufficient, the growth of sulfate-reducing bacteria is not good, and the effect is not good. The second stage A is mainly in anoxic state, which is not conducive to the growth of sulfate-reducing bacteria and cannot achieve a good removal effect.

[0020] In summary, the process of the present invention achieves better sulfate removal through multiple stages, wherein the pH adjustment of the influent is combined with the addition of zero-valent iron in the tertiary A bioreactor to remove sulfate in the system. 2- ions produce FeS precipitation, removing a large amount of S 2- ions, promote the reaction efficiency of sulfate-reducing bacteria and improve the conversion of sulfate radicals; control the dissolved oxygen concentration in the aerobic pool, convert sulfur ions, and further remove S in the water. 2- With SO4 2- ions, and the final effluent sulfate removal rate can be ≥90%. Using the process of the present invention, the sulfate content in sewage within ≤5000 mg / L can be treated very well, which is very suitable for application in the industrial wastewater treatment industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The SO4 effluent from the biochemical system in Example 1 2- Indicator change chart; Figure 2 The COD and SO4 of the effluent from the system in Example 2 2- Indicator change chart; Figure 3 The SO4 in the biochemical system effluent of Example 3 2- Indicator change chart; Figure 4 Comparative example of biochemical system effluent SO4 2- Indicator change chart. DETAILED DESCRIPTION

[0022] The above contents of the present invention are further described in detail below through specific implementation methods, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples. All technologies implemented based on the above contents of the present invention belong to the scope of the present invention. Unless otherwise specified, the following embodiments are all completed using conventional existing technologies.

[0023] In the following Examples 1 and 3, the anaerobic sludge used was anaerobic granular sludge commercially available from Shandong Luxing Environmental Protection Company.

[0024] In Example 2, the anaerobic sludge used was anaerobic granular sludge commercially available from Shandong Boxing Xiangchi Holding Company. Example 1

[0025] The daily condensate wastewater generated by a power plant in a chemical park is 400-500 m³, with a sulfate content of about 3500 mg / L, a low COD content of ≤50 mg / L, and NH4 + -N is 3-10 mg / L. The AAAO process of the present invention is applied to the treatment of the condensation wastewater, as follows: Since the condensed wastewater contains less nutrients, the influent COD (mg / L) is adjusted by controlling the amount of glucose and ethanol (the mass ratio of glucose to ethanol is 15:1): SO4 2- (mg / L) = 0.8:1 to adapt to the growth of anaerobic sludge.

[0026] (1) In each level of anaerobic (AAA) system, 500m3 of water is introduced 3 About 5% of anaerobic sludge is added to each level of anaerobic (AAA) system.

[0027] (2) After the system has adapted for 24 hours (during the adaptation period, the system does not take in or out water), it begins to slowly take in water, with the initial water inflow controlled at 5m 3 / h, and then increase the water intake every 3 days, each time by 5m 3 / h, and the water inflow increased to 20m3 on the 10th day of operation 3 / h normal water inflow. The hydraulic retention time of each level A is 1 day, and the hydraulic retention time of O tank is 1 day.

[0028] In both steps (1) and (2), sulfuric acid must be added to the regulating tank to adjust the pH of the influent to around 6.5, and Fe is added to each level of the anaerobic (AAA) system at a concentration of 150 mg / Ld. 0 , and strictly control the pH of the first-stage A to stabilize it at 6.0-6.5; adjust the speed to control the dissolved oxygen of the first-stage A, second-stage A, and third-stage A to stabilize them at 0.3-0.5 mg / L, 0.1-0.2 mg / L, and 0.4-0.6 mg / L respectively. In step (2), the DO is stabilized at 1.0-1.5 mg / L by controlling the aeration of the O tank.

[0029] Through the above adjustments, the pH of secondary A and tertiary A are stabilized at 5.5-6.0 and 6.3-6.8 respectively, and no further adjustment is required during the process.

[0030] like Figure 1 As shown in the figure, after the power plant condensate wastewater adopts this process, after a certain period of adaptation, the sulfate index of the effluent steadily decreases from the initial 3500 mg / L to ≤50 mg / L, and the sulfate removal efficiency reaches 98.9%. Compared with the original physical and chemical methods on site, it is both efficient and economical. Example 2

[0031] The daily production of chemical wastewater in a chemical park is 200-300 m³, the sulfate content is about 5000 mg / L, the COD content is ≤1500 mg / L, and the NH4 + -N is around 300 mg / L. Due to the high sulfate content in the influent of our plant, the COD treatment effect of the overall system is reduced and the effluent index is high.

[0032] The AAAO process of the present invention is applied to the wastewater treatment, specifically as follows: Because the wastewater contains high nutrients, the influent COD (mg / L) is adjusted by controlling the amount of glucose and ethanol supplement (the mass ratio of glucose to ethanol is 12:1): SO4 2- (mg / L) = 1.0:1 to adapt to the growth of anaerobic sludge.

[0033] (1) In each level of anaerobic (AAA) system, 300m of water is introduced 3 About 5%, add anaerobic sludge to each level of anaerobic (AAA) system. In the first level A tank, strictly control the pH to 6.0-6.5, adjust the stirring speed, and strictly control the DO (mg / L): the first level A is 0.3-0.5 mg / L, the second level A is 0.1-0.2 mg / L, and the third level A is 0.4-0.6 mg / L.

[0034] (2) After the system has adapted for 24 hours (during the adaptation period, the system does not take in or out water), it begins to slowly take in water. The water intake in the first 3 days is controlled at 5m 3 / h(120m 3 / d), and then resume normal water inflow for 10m 3 / h(240m 3 / d). The hydraulic retention time of each level A is 1d, and the hydraulic retention time of O pool is 2d.

[0035] In both steps (1) and (2), sulfuric acid must be added to the regulating tank to adjust the pH of the influent to around 6.5, and Fe is added to each level of the anaerobic (AAA) system at a concentration of 200 mg / Ld. 0 In the first-stage A pool, the pH is strictly controlled at 6.0-6.5; the rotation speed is adjusted to control the dissolved oxygen of the first-stage A, second-stage A, and third-stage A to stabilize them at 0.3-0.5 mg / L, 0.1-0.2 mg / L, and 0.4-0.6 mg / L, respectively; in step (2), the aeration of the O pool is controlled to stabilize the DO at 1.0-1.5 mg / L.

[0036] Through the above adjustments, the pH of secondary A and tertiary A are stabilized at 5.6-6.1 and 6.4-6.7 respectively, and no further adjustment is required during the process.

[0037] like Figure 2As shown in the figure, after the chemical plant wastewater adopts this process, after a certain period of adaptation, the sulfate index of the effluent steadily decreases from the initial 5000 mg / L to ≤100 mg / L, and the sulfate removal efficiency reaches 98.3%. With the removal of sulfate, the COD residual volume steadily decreases, and the final effluent COD is stabilized at ≤80 mg / L; the COD degradation rate rises to 95.3%; the inhibition by sulfate is well relieved. Example 3

[0038] The daily production of petrochemical thermal cycle wastewater in a chemical park is 1000-1200 m³, the sulfate content is about 1700 mg / L, the COD content is low ≤50 mg / L, and the pH is 6.0-6.5. Due to the high sulfate content, the discharge requirements are not met. The AAAO process of the present invention is applied to the treatment of the condensation wastewater, as follows: Because the wastewater contains less nutrients, the influent COD (mg / L) is adjusted by controlling the amount of glucose and ethanol (the mass ratio of glucose to ethanol is 15:1): SO4 2- (mg / L) = 0.8 to adapt to the growth of anaerobic sludge.

[0039] (1) In each level of anaerobic (AAA) system, 1100m3 of water is introduced 3 About 5% of anaerobic sludge is added to each level of anaerobic (AAA) system.

[0040] (2) After the system has adapted for 24 hours (during the adaptation period, the system does not take in or out water), it starts to slowly take in water. The water intake in the first 3 days is controlled at 200-300m 3 / d, the water intake from the 4th to the 6th day is controlled at 300-500m 3 / d, the water intake from the 7th to the 9th day is controlled at 500-800m 3 / d, and on the 10th day, the water flow rate is increased to 800-1200 m³ / d, and the water flow is normal. The hydraulic retention time of each level A is 1 day, and the hydraulic retention time of O pool is 2 days.

[0041] In steps (1) and (2), Fe was added to each level of the anaerobic (AAA) system at a concentration of 90 mg / Ld. 0 , the pH of the first-stage A pool is strictly controlled at 6.0-6.5; the rotation speed is adjusted to control the dissolved oxygen of the first-stage A, second-stage A, and third-stage A to stabilize them at 0.3-0.7 mg / L, 0.1-0.3 mg / L, and 0.3-0.6 mg / L respectively. In step (2), the aeration of the O pool is controlled to stabilize the DO at 1.0-1.5 mg / L.

[0042] Through the above adjustments, the pH of secondary A and tertiary A are stabilized at 5.5-6.0 and 6.0-6.5 respectively, and no further adjustment is required during the process.

[0043] like Figure 3 As shown in the figure, after a certain period of adaptation, the sulfate index of the effluent steadily decreased, from the initial 1700 mg / L to ≤50 mg / L, and the sulfate removal efficiency reached 99.0%, and the sulfate was well removed. Comparative Example

[0044] A comparative experiment was conducted for the same wastewater in Example 3. The conventional AAO process was used, and Fe was not added to the anaerobic (AAA) system at each level. 0 , other process conditions (such as anaerobic sludge, water inlet setting, hydraulic retention time, etc.) are the same as those in Example 3.

[0045] The specific AAO process conditions are as follows: the pH and DO of the first stage A are about 6.5 and 0.1-0.2 mg / L respectively; the pH and DO of the second stage A are stable at about 6.3 and 0.5-0.8 mg / L respectively, and the DO of the aerobic tank is 2-4 mg / L.

[0046] like Figure 4 As shown, after a certain period of adaptation, the effluent sulfate index decreased from an initial 1700 mg / L to 602 mg / L, and the sulfate removal efficiency reached 64.80%. Compared with Example 3, the sulfate removal efficiency was reduced and the adaptation period was longer.

Claims

1. A method for improving the efficiency of biological desulfurization, characterized in that: The method is specifically an AAAO process, wherein: (1) Add anaerobic sludge to the AAA bioreactor and control its initial volume concentration to 5% to 10% to convert SO4 2- Restore to S 2- ion; (2) Adding Fe to the AAA bioreactor 0 , control the Fe content in each level of A 0 Concentration 50~300 mg / Ld.

2. A method for improving biological desulfurization efficiency according to claim 1, characterized in that: A regulating tank is set before the AAAO process to adjust the pH of the influent to 5.5-6.

5.

3. A method for improving biological desulfurization efficiency according to claim 1, characterized in that: The first level A strictly controls the pH value between 5.5 and 6.

5.

4. The method for improving biological desulfurization efficiency according to claim 1, characterized in that: The aerobic pool O bioreactor is slightly aerated, and its dissolved oxygen concentration is controlled at 1.0-1.5 mg / L.

5. The method for improving biological desulfurization efficiency according to claim 1, characterized in that: Control COD (mg / L): SO4 in AAA bioreactor 2- (mg / L) = 0.7~1.5:

1.

6. The method for improving biological desulfurization efficiency according to claim 1, characterized in that: The specific control parameters of the dissolved oxygen content of the tertiary A are: the dissolved oxygen content in the first stage A is 0.3-0.7 mg / L; the dissolved oxygen content in the second stage A is 0.1-0.3 mg / L; the dissolved oxygen content in the third stage A is 0.3-0.7 mg / L.

7. The method for improving biological desulfurization efficiency according to claim 1, characterized in that: According to the influent conditions, carbon sources are added to the COD (mg / L) and SO4 in the water. 2- (mg / L) ratio is 0.7~1.5:

1.

8. A method for improving biological desulfurization efficiency according to claim 7, characterized in that: The supplemented carbon source was a combination of glucose and ethanol.

9. A method for improving biological desulfurization efficiency according to claim 8, characterized in that: The mass ratio of glucose to ethanol is 10:1 to 20:

1.

10. The method for improving biological desulfurization efficiency according to claim 1, characterized in that: Control the hydraulic retention time of each section. The specific control parameters are: the hydraulic retention time of each level A is 1.0 to 1.5 d; the hydraulic retention time of O is 0.5 to 2.0 d.

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