A method for culturing aerobic granular sludge

Abstract

The present invention discloses a method for culturing aerobic granular sludge. The method includes: using a mixture of activated sludge and oily sludge for treating aromatic hydrocarbon-containing wastewater to construct an inoculated sludge system, and adopting the intermittent activated sludge method for the inoculated sludge system, that is, in each cycle, aerobic granular sludge is cultured in the order of influent water, aeration, sedimentation, and drainage in sequence. During aeration, the dissolved oxygen (DO) is controlled to be 0.5 - 1.0 mg / L. During the culturing period, the pH value of the system is controlled to be 6.5 - 7.5, and the temperature is 28 - 35 °C. The method of the present invention can effectively promote sludge granulation and realize the recycling of resources.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a method for culturing aerobic granular sludge. Background Art

[0002] Aerobic granular sludge is an aggregate of multi-species microorganisms and is considered a special self-immobilized organism. Compared with ordinary activated sludge, granular sludge has the advantages of a compact structure, excellent sedimentation performance, and strong shock load resistance, becoming a new research hotspot in the field of wastewater biological treatment. However, the sludge granulation process takes a long time, resulting in a long start-up time for the process.

[0003] CN112551683A discloses a method for rapid cultivation and stabilization of aerobic granular sludge based on the synthesis of quorum sensing signal molecules. This method uses aerobic activated sludge as the seed sludge, and by adding sulfate to the influent of the aeration tank, and utilizing the up-regulation mechanism of sulfate on the synthesis of quorum sensing signal molecule homoserine lactone (AHLs), symbiosis between aerobic bacteria and sulfate-reducing bacteria in the activated sludge is achieved to maintain the stability of the core area inside the granular sludge, thereby enhancing the stability of aerobic granular sludge during long-term operation, and at the same time improving the effect of pollutant removal by the sludge in the early stage of granulation. However, the end product of sulfate-reducing bacteria is sulfide, which easily causes peculiar smells in the water body.

[0004] CN108773899A discloses a method for rapid cultivation of aerobic granular sludge and a culture medium. The cultivation method includes the step of culturing the inoculated sludge using a culture medium containing As 3+ . This cultivation method does not require additional addition of fine particles as induced crystal nuclei, but accelerates the granulation process of the inoculated sludge through a culture medium containing As 3+ , thereby realizing the rapid cultivation of aerobic granular sludge. During the cultivation process, As 3+ is oxidized and converted into As 5+ , and after treatment, it can achieve up-to-standard discharge. Although the aerobic granular sludge prepared by this method has better biological phosphorus removal effect, the dosage of As 3+ needs to be strictly monitored during the formation process of activated sludge, otherwise it will affect the biological activity. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a method for culturing aerobic granular sludge. Using the method of the present invention can effectively promote sludge granulation and achieve the recycling of resources.

[0006] The present invention provides a method for culturing aerobic granular sludge, comprising: using a mixture of activated sludge and oily sludge for treating aromatic hydrocarbon-containing wastewater to construct an inoculated sludge system, and adopting the intermittent activated sludge method for the inoculated sludge system, that is, in each cycle, aerobic granular sludge is cultured in the order of influent water, aeration, sedimentation, and drainage. During aeration, the dissolved oxygen (DO) is controlled at 0.5-1.0 mg / L. During the culturing period, the pH value of the system is controlled at 6.5-7.5, and the temperature is 28-35 °C.

[0007] Further, the oily sludge is oily sludge generated from oil fields and / or hydrocarbon oil storage tanks, etc., with an oil content of 10%-50%, preferably 25%-45%. The hydrocarbon oil is preferably crude oil.

[0008] Further, the activated sludge for treating aromatic hydrocarbon-containing wastewater is the activated sludge discharged from the biochemical unit for treating aromatic hydrocarbon-containing wastewater. The activated sludge is flocculent sludge.

[0009] Further, the aromatic hydrocarbon-containing wastewater can be at least one of printing and dyeing wastewater, pharmaceutical wastewater, essence and spice wastewater, and Lurgi gasifier coal chemical wastewater, preferably Lurgi gasifier coal chemical wastewater.

[0010] Further, the mass ratio of the oily sludge to the activated sludge for treating aromatic hydrocarbon-containing wastewater is 0.5:100-9:100, preferably 0.5:100-2:100, and further 1:100-2:100.

[0011] Further, after inoculating the activated sludge for treating aromatic hydrocarbon-containing wastewater, the MLSS is 2000-5000 mg / L, and the inoculated sludge system is introduced into the reactor, and then aerobic granular sludge is cultured according to the intermittent reaction. Each operation cycle sequentially undergoes influent water, aeration, sedimentation, and drainage. Each operation cycle can generally be 4-12 hours, wherein the aeration time accounts for 70%-98%, and the influent water, sedimentation, and drainage times can be adjusted according to the actual situation. Generally, the sedimentation time can be controlled at 5-15 min. Further, the drainage ratio is controlled according to the conventional intermittent activated sludge method, generally not higher than 60%.

[0012] Further, during the intermittent reaction process, the influent volume load of the wastewater to be treated is increased gradually until the designed influent load is reached. The initial influent volume load of the wastewater to be treated can be 5%-30% of the designed influent volume load. The amplitude of increasing the influent volume load of the wastewater to be treated each time is 5%-20% of the designed influent volume load. The condition for increasing the influent volume load of the wastewater to be treated can be that when the discharged water in the current cycle meets the designed discharge index, the influent volume load of the wastewater to be treated is increased in the next cycle.

[0013] Further, in the batch reaction process, when the influent volume loading reaches the designed influent volume loading and the SVI5 / SVI30 ratio is 1 ± 0.1, the cultivation of aerobic granular sludge is completed.

[0014] Further, after the influent enters, a nutrient agent is added to the reactor, and the volume addition amount of the nutrient agent is 15% - 40% of the influent wastewater volume. Further preferably, the nutrient agent is added once every 1 - 2 cycles until the sludge granulation is completed.

[0015] Further, the preparation method of the nutrient agent is as follows: The aerobic granular sludge is crushed, and then Na2CO3 is added so that the concentration of Na2CO3 in the crushed aerobic granular sludge is 0.005 g / mL - 0.015 g / mL. It is left standing at 70 - 85 °C for 2 - 4 h, and then the pH value of the separated supernatant is adjusted to 7.5 - 8.5 to obtain the nutrient agent. Among them, Na2CO3 can be replaced by the waste alkali produced from coal - to - olefins, and the mass content of Na2CO3 in the waste alkali is 90% - 98%. The aerobic granular sludge is undehydrated sludge with a moisture content of 95wt% - 99wt%.

[0016] Further, in the wastewater to be treated, the total hardness is 250 mg / L - 1100 mg / L, and the hard calcium is 200 mg / L - 600 mg / L. If the total hardness of the wastewater is not within the above range, it needs to be adjusted by adding inorganic ions or a hard - removal method.

[0017] Further, in the wastewater to be treated, the COD is 1000 mg / L - 5000 mg / L, and the ammonia nitrogen is 30 mg / L - 80 mg / L.

[0018] Further, in the wastewater to be treated, COD / TN is at least greater than 5, preferably 7 - 25.

[0019] Further, the wastewater to be treated is organic wastewater, and the organic wastewater can be municipal wastewater and / or industrial wastewater. The industrial wastewater can be at least one of slaughter wastewater, beer wastewater, dairy wastewater, etc.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. In the method of the present invention, an inoculated sludge system is constructed by using a mixture of activated sludge for treating aromatic hydrocarbon-containing wastewater and oily sludge, and aerobic granular sludge is cultivated by the intermittent activated sludge method. By controlling the cultivation conditions, aerobic sludge can be rapidly granulated. Among them, the activated sludge for treating aromatic hydrocarbon-containing wastewater is rich in bacteria that secrete quorum sensing signal molecules and second messengers. During the cultivation of aerobic sludge, under the action of chemicals in the oily sludge, it can promote the up-regulation of the secretion of quorum sensing signal molecules and second messengers, enabling the rapid granulation of aerobic sludge. In addition, the microorganisms in the activated sludge for treating aromatic hydrocarbon-containing wastewater have a strong ability to treat oily sludge, which can avoid secondary pollution of oily sludge while ensuring the activity of the sludge.

[0022] 2. In the method of the present invention, by adding specific nutrients, it is possible to simultaneously ensure the microbial treatment effect, promote the secretion of quorum sensing signal molecules and second messengers in the sludge system, and promote sludge granulation. The nutrient prepared by a specific method is rich in nutrients that are easily absorbed by microorganisms and rich in polysaccharides with special structures, which promotes sludge granulation. By a specific dosage, the ion concentration therein can stimulate the up-regulation of the secretion of quorum sensing signal molecules and second messengers in the sludge system. In addition, the raw material of this nutrient is aerobic granular sludge, which does not inhibit the activity of bacteria; because the nutrient contains extracellular polymers and has good bioflocculability, even when using the waste alkali generated from coal-to-olefins production, no secondary pollution will occur.

[0023] 3. In the method of the present invention, the materials used are preferably excess sludge and waste alkali, which can make the excess sludge and waste alkali resourceful while promoting granulation, meeting the background of the current circular economy. Detailed Embodiments

[0024] The method provided by the present invention will be further described below in combination with embodiments to comparatively reflect the effects and advantages of the method of the present invention, but the present invention is not limited thereby.

[0025] In the present invention, unless otherwise specified, percentages refer to mass fractions.

[0026] In the present invention, SVI refers to the sludge volume index, SVI5 = 5-minute sludge sedimentation volume (SV5) (mL / L) / MLSS (g / L), and SVI30 = 30-minute sludge sedimentation volume (SV30) (mL / L) / MLSS (g / L). Among them, SV5 (or SV30) is the sludge sedimentation volume at 5 minutes (or 30 minutes). The well-mixed activated sludge mixture in the aeration tank is quickly poured into a 1000 mL graduated cylinder until it reaches the full scale, and left to stand for 5 minutes (or 30 minutes), then the volume ratio (mL / L) of the sedimented sludge to the taken mixture. MLSS is measured by the conventional gravimetric method in the industry.

[0027] In the present invention, the COD concentration is determined by the method of GB11914-89 "Determination of Chemical Oxygen Demand in Water - Dichromate Method"; the ammonia nitrogen concentration is determined by the method of GB7478-87 "Determination of Ammonium in Water - Distillation and Titration Method", and the total nitrogen concentration (TN) is determined by the method of GB11894-89 "Determination of Total Nitrogen in Water - Alkaline Potassium Persulfate Digestion UV Spectrophotometry".

[0028] In the present invention, the total hardness is measured by the method of GB7477-1987 "Determination of Total Calcium and Magnesium - EDTA Titration Method", and the calcium hardness is measured by the method of GB7476-1987 "Determination of Calcium - EDTA Titration Method".

[0029] In the present invention, the test method for the oil content of oily sludge adopts the method of "Determination of Mineral Oil in Municipal Sludge - Infrared Spectrophotometry" in CJ / T221-2005 "Inspection Methods for Sludge from Municipal Wastewater Treatment Plants" for sewage.

[0030] Example 1

[0031] The preparation method of the nutrient agent used in this example is as follows: 100 ml of aerobic granular sludge (containing 97% water) is crushed by a homogenizing grinder, and then 1 g of waste alkali from coal-to-olefins is added. The content of Na2CO3 in the waste alkali is 95%. After mixing evenly, it is left standing at 80 °C for 3 h, centrifuged (3000 rmp, 3 min) to obtain the supernatant, and the pH value of the supernatant is adjusted to 8 to obtain the nutrient agent.

[0032] The activated sludge discharged from the biochemical unit treating Lurgi gasification wastewater and the bottom sludge of the crude oil tank with an oil content of 30.5% are used as inoculated sludge in a ratio of 100:1 by the original mass ratio and inoculated in the reactor. The inoculation is carried out according to the inoculation amount of MLSS of 4000 mg / L after inoculating the activated sludge. Each cycle is set to 6 h, with 10 min of water inlet, 340 min of aeration, 5 min of sedimentation, and 5 min of drainage.

[0033] Feed the reactor with the wastewater to be treated, whose water quality is COD content of 1200 mg / L, ammonia nitrogen content of 60 mg / L, total nitrogen content of 75 mg / L, total hardness of 400 mg / L, and calcium hardness of 280 mg / L. The initial influent volume load of the wastewater to be treated is 20% of the designed influent volume load, and perform periodic operation according to the cycle set in this embodiment. When the drainage meets the design discharge index, i.e., COD < 50 mg / L, ammonia nitrogen < 8 mg / L, total nitrogen < 30 mg / L, in the next cycle, increase the designed influent volume load by 10% until the influent volume increases to the designed load, and then continuously operate according to the set cycle. Among them, after the first cycle of water inlet, add a nutrient agent to the reactor, and the volume dosage of the nutrient agent is 20% of the volume of the wastewater inlet. After that, add the nutrient agent once every cycle according to 20% of the volume of the wastewater inlet; in the culture system, pH = 7, T = 30 °C, and control DO = 1 mg / L during aeration. When the aerobic granular sludge reaches an SVI5 / SVI30 ratio of about 1, the sludge granulation is completed. The time for the completion of cultivation is 19 days.

[0034] Example 2

[0035] The preparation method of the nutrient agent is the same as that in Example 1.

[0036] Take the activated sludge discharged from the biochemical unit treating Lurgi gasification wastewater and the bottom sludge of the crude oil tank with an oil content of 41.2% as the inoculated sludge in a ratio of 100:2 by the original mass ratio, and inoculate it in the reactor. The inoculation is carried out according to the inoculation amount of MLSS of 3000 mg / L after inoculating the activated sludge. Set each cycle to be 8 h, with 40 min of water inlet, 420 min of aeration, 10 min of sedimentation, and 10 min of drainage.

[0037] Feed the reactor with the wastewater to be treated, whose water quality is COD content of 2850 mg / L, ammonia nitrogen content of 44 mg / L, total nitrogen content of 128 mg / L, total hardness of 650 mg / L, and calcium hardness of 430 mg / L. The initial influent volume load of the wastewater to be treated is 10% of the designed influent volume load, and perform periodic operation according to the cycle set in this embodiment. When the drainage meets the design discharge index, i.e., COD < 75 mg / L, ammonia nitrogen < 10 mg / L, total nitrogen < 15 mg / L, in the next cycle, increase the designed influent volume load by 15% until the influent volume increases to the designed load, and then continuously operate according to the set cycle. Among them, after the first cycle of water inlet, add a nutrient agent to the reactor, and the volume dosage of the nutrient agent is 35% of the volume of the wastewater inlet. After that, add the nutrient agent once every cycle according to 25% of the volume of the wastewater inlet; in the culture system, pH = 7.3, T = 32 °C, and control DO = 0.9 mg / L during aeration. When the aerobic granular sludge reaches an SVI5 / SVI30 ratio of about 1, the sludge granulation is completed. The time for the completion of cultivation is 19 days.

[0038] Example 3

[0039] The preparation method of the nutrient agent used in this example is as follows: 100 ml of aerobic granular sludge (containing 97% water) is crushed by a homogenizing grinder, and then 0.5 g of waste alkali from coal-to-olefin production is added. The content of Na2CO3 in the waste alkali is 95%. After mixing evenly, it is left standing at 70 °C for 2 h, and then centrifuged (3000 rmp, 3 min) to separate the supernatant. The pH value of the supernatant is adjusted to 8 to obtain the nutrient agent.

[0040] The activated sludge discharged from the biochemical unit for treating spice and essence production wastewater and the bottom sludge of a diesel oil tank with an oil content of 50% are used as inoculated sludge at a ratio of 100:0.5 by the original mass ratio, and inoculation is carried out in the reactor. The inoculation is carried out according to the MLSS of 2500 mg / L after inoculating the activated sludge. Each cycle is set to 6 h, with 10 min of influent, 330 min of aeration, 15 min of sedimentation, and 5 min of drainage. The final drainage ratio is 60%.

[0041] Wastewater is fed into the reactor, and the quality of the wastewater is the same as that in Example 1. The initial influent volume load of the wastewater to be treated is 30% of the designed influent volume load. Periodic operation is carried out according to the cycle set in this example. When the drainage meets the design discharge indicators, i.e., COD < 50 mg / L, ammonia nitrogen < 8 mg / L, and total nitrogen < 30 mg / L, the amplitude of increasing the designed influent volume load in the next cycle is 15% until the influent volume increases to the designed load, and then continuous operation is carried out according to the set cycle. Among them, after the influent in the first cycle, a nutrient agent is added to the reactor, and the volume dosage of the nutrient agent is 15% of the volume of the wastewater influent. After that, every other cycle, the nutrient agent is added once at 15% of the volume of the wastewater influent; in the culture system, pH = 7.5, T = 35 °C, and the DO is controlled at 0.8 mg / L during aeration. When the SVI5 / SVI30 ratio of the aerobic granular sludge reaches about 1, the sludge granulation is completed. The cultivation time is 25 days.

[0042] Example 4

[0043] The activated sludge discharged from the biochemical unit for treating Lurgi gasification wastewater and the bottom sludge of a crude oil tank with an oil content of 30.5% are used as inoculated sludge at a ratio of 100:0.5 by the original mass ratio. The others are the same as in Example 1. When the SVI5 / SVI30 ratio of the aerobic granular sludge reaches about 1, the sludge granulation is completed. The cultivation time is 22 days.

[0044] Example 5

[0045] The activated sludge discharged from the biochemical unit treating Lurgi gasification wastewater and the bottom sludge of the crude oil tank with an oil content of 11.5% were used as the inoculated sludge at the original mass ratio of 100:1. The others were the same as in Example 1. When the SVI5 / SVI30 ratio of the aerobic granular sludge reached about 1, the sludge granulation was completed. The cultivation was completed in 22 days.

[0046] Example 6

[0047] The activated sludge discharged from the biochemical unit treating spice and essence production wastewater and the bottom sludge of the crude oil tank with an oil content of 30.5% were used to establish the inoculated sludge at the original mass ratio of 100:1. The others were the same as in Example 1. When the SVI5 / SVI30 ratio of the aerobic granular sludge reached about 1, the sludge granulation was completed. The cultivation was completed in 24 days.

[0048] Example 7

[0049] In this example, the activated sludge discharged from the biochemical unit treating Lurgi gasification wastewater and the bottom sludge of the crude oil tank with an oil content of 30.5% were used as the inoculated sludge at the original mass ratio of 100:8. The others were the same as in Example 1. When the SVI5 / SVI30 ratio of the aerobic granular sludge reached about 1, the sludge granulation was completed. The cultivation was completed in 28 days.

[0050] Example 8

[0051] After the water inlet, no nutrient agent was added, and the others were the same as in Example 1. When the SVI5 / SVI30 ratio of the aerobic granular sludge reached about 1, the sludge granulation was completed. The cultivation was completed in 30 days.

[0052] Comparative Example 1

[0053] The activated sludge discharged from the biochemical unit treating domestic sewage and the bottom sludge of the crude oil tank with an oil content of 30.5% were used as the inoculated sludge, and the others were the same as in Example 1. When the SVI5 / SVI30 ratio of the aerobic granular sludge reached about 1, the sludge granulation was completed. The cultivation was completed in 58 days.

[0054] Comparative Example 2

[0055] The activated sludge treating Lurgi gasification was used, but no bottom sludge of the crude oil tank was added. The others were the same as in Example 8. When the SVI5 / SVI30 ratio of the aerobic granular sludge reached about 1, the sludge granulation was completed. The cultivation was completed in 50 days.

[0056] Comparative Example 3

[0057] Using the activated sludge discharged from the biochemical unit treating domestic sewage and the bottom sludge of the crude oil tank with an oil content of 30.5% as the inoculated sludge, and the others are the same as in Example 8. When the aerobic granular sludge reaches an SVI5 / SVI30 ratio of about 1, the sludge granulation is completed. The cultivation is completed in 70 days.

Claims

1. A method for culturing aerobic granular sludge, characterized in that, The method includes: using a mixture of activated sludge for treating aromatic hydrocarbon-containing wastewater and oily sludge to construct an inoculated sludge system, and adopting the intermittent activated sludge method for the inoculated sludge system, that is, in each cycle, aerobic granular sludge is cultured in the order of influent, aeration, sedimentation, and drainage. During aeration, the dissolved oxygen (DO) is controlled at 0.5 - 1.0 mg / L. During the culture period, the pH value of the system is controlled at 6.5 - 7.5, and the temperature is controlled at 28 - 35 °C.

2. The cultivation method according to claim 1, characterized in that, The oily sludge is oily sludge generated from oil fields and / or hydrocarbon oil storage tanks, and the oil content is 10% - 50%.

3. The cultivation method according to claim 1, characterized in that, The oily sludge is oily sludge generated from oil fields and / or hydrocarbon oil storage tanks, and the oil content is 25% - 45%.

4. The cultivation method according to claim 1, characterized in that, The activated sludge for treating aromatic hydrocarbon-containing wastewater is the activated sludge discharged from the biochemical unit for treating aromatic hydrocarbon-containing wastewater.

5. The cultivation method according to claim 1 or 4, characterized in that, The aromatic hydrocarbon-containing wastewater is at least one of printing and dyeing wastewater, pharmaceutical wastewater, essence and spice wastewater, and Lurgi gasifier coal chemical wastewater.

6. The cultivation method according to claim 1 or 4, characterized in that, The aromatic hydrocarbon-containing wastewater is Lurgi gasifier coal chemical wastewater.

7. The cultivation method according to claim 1, characterized in that The mass ratio of the oily sludge to the activated sludge for treating aromatic hydrocarbon-containing wastewater is 0.5:100 - 9:

100.

8. The culturing method according to claim 1, characterized in that, The mass ratio of the oily sludge to the activated sludge for treating aromatic hydrocarbon-containing wastewater is 0.5:100 - 2:

100.

9. The cultivation method according to claim 1, characterized in that, The mass ratio of the oily sludge to the activated sludge for treating aromatic hydrocarbon-containing wastewater is 1:100 - 2:

100.

10. The culturing method according to claim 1, characterized in that, After inoculating the activated sludge for treating aromatic hydrocarbon-containing wastewater, when the MLSS is 2000 - 5000 mg / L, the inoculated sludge system is connected to the reactor, and then aerobic granular sludge is cultured according to the intermittent reaction. Each operation cycle sequentially undergoes influent, aeration, sedimentation, and drainage.

11. The cultivation method according to claim 10, characterized in that, Each operation cycle is 4 - 12 hours, in which the aeration time accounts for 70% - 98%, and the sedimentation time is controlled at 5 - 15 min.

12. The cultivation method according to claim 10 or 11, characterized in that, During the intermittent reaction process, when the influent volume load reaches the designed influent volume load and when the SVI5 / SVI30 ratio is 1 ± 0.1, the cultivation of aerobic granular sludge is completed.

13. The culturing method according to claim 1, characterized in that, After influent, a nutrient agent is added to the reactor, and the volume addition amount of the nutrient agent is 15% - 40% of the influent volume of the wastewater.

14. The cultivation method according to claim 13, characterized in that, The preparation method of the nutrient agent is: crushing the aerobic granular sludge, and then adding Na2CO3 so that the concentration of Na2CO3 in the crushed aerobic granular sludge is 0.005 g / mL - 0.015 g / mL, standing at 70 - 85 °C for 2 - 4 h, and then adjusting the pH value of the separated supernatant to 7.5 - 8.5 to obtain the nutrient agent.

15. The cultivation method according to claim 1 or 10 or 11, characterized in that, In the wastewater to be treated, the total hardness is 250 mg / L - 1100 mg / L, and the hard calcium is 200 mg / L - 600 mg / L.

16. The culturing method according to claim 1 or 10 or 11, characterized in that, In the wastewater to be treated, the COD is 1000 mg / L - 5000 mg / L, and the ammonia nitrogen is 30 mg / L - 80 mg / L.

17. The cultivation method according to claim 15, characterized in that, In the wastewater to be treated, the COD is 1000 mg / L - 5000 mg / L, and the ammonia nitrogen is 30 mg / L - 80 mg / L.

18. The culturing method according to claim 15, characterized in that, In the wastewater to be treated, COD / TN is at least greater than 5.

19. The culturing method according to claim 18, characterized in that, In the wastewater to be treated, COD / TN is 7 - 25.

20. The cultivation method according to any one of claims 1, 10 or 18, characterized in that, The incoming wastewater to be treated is organic wastewater, and the organic wastewater is municipal wastewater and / or industrial wastewater, and the industrial wastewater is at least one of slaughter wastewater, beer wastewater, and dairy wastewater.