Sewage phosphorus removal and enrichment process method based on aerobic granular sludge

Abstract

The invention belongs to the technical field of sewage recovery, and particularly relates to a sewage phosphorus removal and enrichment process method based on aerobic granular sludge. The process comprises the following specific steps: 1) inoculating mature aerobic granular sludge in a granular sludge phosphorus absorption reactor, and absorbing and removing phosphorus in sewage by the aerobic granular sludge under aerobic or anaerobic-aerobic alternating conditions; 2) conveying the phosphorus-absorbed aerobic granular sludge to a granular sludge phosphorus release reactor through a sludge-water separation conveying system; 3) adding a carbon source into the granular sludge phosphorus release reactor, and releasing phosphorus in the aerobic granular sludge by using the carbon source under an anaerobic condition to form a phosphorus-rich solution; and 4) returning the aerobic granular sludge in which phosphorus is released to the granular sludge phosphorus absorption reactor through a sludge-water separation conveying system. The process can be used for synchronous removal and enrichment of phosphorus in municipal sewage or industrial sewage, the residual sludge amount in the process is small, the granular sludge stability is good, the volume utilization rate of the reactor is high, the process can be continuously operated, and the operation energy consumption is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage recovery, and in particular relates to a process for removing and enriching phosphorus in sewage based on aerobic granular sludge. Background Art

[0002] Phosphorus is a non-renewable resource facing depletion. Discharged wastewater (such as municipal sewage) contains phosphorus, which not only causes environmental problems such as eutrophication but also represents a waste of phosphorus resources. Removing and recovering phosphorus from wastewater is crucial for the recycling of phosphorus resources and the protection of aquatic environments.

[0003] Phosphorus concentrations in municipal wastewater are generally low (<10 mg / L), making direct phosphorus recovery from wastewater difficult. The enhanced biological phosphorus removal (EBPR) process currently used in municipal wastewater treatment plants primarily relies on the discharge of excess sludge to remove phosphorus. In the field of phosphorus resource recovery, existing technologies, such as sidestream phosphorus recovery processes (such as struvite crystallization), achieve phosphorus recovery by extracting phosphates from the supernatant of anaerobic fermentation of excess sludge. These phosphorus removal and recovery processes are subject to challenges such as complex operation, high costs, large land requirements, and high sludge production.

[0004] Aerobic granular sludge (AGS) based on microbial self-flocculation is an emerging wastewater treatment technology with advantages such as high microbial concentration, good sludge settling performance, and small reactor footprint. It is being widely used for nitrogen and phosphorus removal in wastewater. Currently, phosphorus recovery using AGS technology is mainly achieved in two ways: (1) similar to the phosphorus recovery method of traditional activated sludge, the phosphorus-enriched AGS is treated as residual sludge. After treatment, the AGS is severely damaged and loses its pollutant removal capacity; (2) using the anaerobic zone (such as continuous flow anaerobic-aerobic-precipitation process) or anaerobic period (such as sequencing batch process) set in the wastewater treatment process, AGS releases phosphorus under anaerobic conditions to form a high concentration of phosphorus-containing wastewater, and then performs in-situ or ex-situ chemical treatment to recover phosphorus. Such methods generally have problems such as poor AGS stability, low reactor volume utilization, inability to operate continuously, and low phosphorus recovery rate. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, this application provides the following technical solutions:

[0006] The present invention provides a process for removing and enriching phosphorus from sewage based on aerobic granular sludge, comprising the following steps:

[0007] S11: adding phosphorus-containing wastewater to a reactor containing aerobic granular sludge, and performing aerobic treatment or anaerobic-aerobic alternating treatment, so that phosphorus in the phosphorus-containing wastewater is absorbed by the aerobic granular sludge; the aerobic granular sludge is enriched with phosphorus-accumulating bacteria;

[0008] S12: performing mud-water separation, the sludge obtained after the mud-water separation enters a reactor containing water, and a degradable carbon source is introduced for anaerobic treatment, so that the phosphorus in the sludge is released into the water;

[0009] S13: performing secondary mud-water separation to obtain a phosphorus-rich base liquid and secondary sludge, and re-discharging the secondary sludge into the reactor containing aerobic granular sludge, while the phosphorus-rich base liquid remains in the reactor containing water;

[0010] S14: Repeat steps S11 to S13 several times to complete the wastewater phosphorus removal and enrichment process based on aerobic granular sludge.

[0011] Preferably, the reactor containing aerobic granular sludge is selected from a sequencing batch reactor or a continuous flow reactor; when a sequencing batch reactor is used, aerobic treatment is performed in step S11.

[0012] Preferably, the steps S11 to S13 are repeated 4 times a day for 6 hours; and the aerobic treatment or the anaerobic-aerobic alternating treatment is repeated for 4-5 hours.

[0013] Furthermore, the continuous flow reactor includes an aerobic operation area and an anaerobic operation area.

[0014] Furthermore, when the sequencing batch reactor is used, steps S11 to S13 are repeated 4-8 times per day.

[0015] Preferably, in step S12, the sewage after mud-water separation is directly discharged or re-enters the reactor described in step S11.

[0016] Preferably, in step S12, a stirring system is provided at the bottom of the reactor containing water.

[0017] Furthermore, in the step S12, the stirring system is used for stirring during anaerobic treatment.

[0018] Preferably, the degradation carbon source is selected from methanol, ethanol, acetic acid or wastewater and waste liquid; the wastewater and waste liquid contains methanol, ethanol or acetic acid.

[0019] Preferably, in the reactor containing water, the water is selected from clean water or tap water.

[0020] Preferably, in step S14, the phosphorus concentration in the phosphorus-rich base liquid in the reactor containing water reaches 120-150 mg / L.

[0021] Specifically, the sewage phosphorus removal and enrichment process based on aerobic granular sludge includes the following steps:

[0022] Mature aerobic granular sludge (polyphosphate bacteria are enriched in the aerobic granular sludge) is inoculated into the AGS phosphorus absorption reactor, and the sewage enters the AGS phosphorus absorption reactor. The AGS phosphorus absorption reactor is operated under aerobic or anaerobic-aerobic alternating conditions. The phosphorus in the sewage is absorbed and removed by the polyphosphate bacteria in the aerobic granular sludge under aerobic conditions.

[0023] At the same time, the aerobic granular sludge that has absorbed phosphorus is separated from the sewage through the mud-water separation and transportation system. The sewage is returned to the reactor, and the granular sludge is transported to the granular sludge phosphorus release reactor.

[0024] At the same time, a phosphorus-rich base liquid (usually clean water or tap water initially) is added to the reactor, the reactor is maintained under anaerobic conditions, and the granular sludge and the phosphorus-rich base liquid are mixed through a stirring device; at the same time, a degradation carbon source (such as methanol, ethanol, acetic acid or wastewater containing these carbon sources) that can be utilized by polyphosphate bacteria is supplied to the AGS phosphorus release reactor through a carbon source addition system, and the polyphosphate bacteria in the aerobic granular sludge utilizes the carbon source to release phosphorus into the phosphorus-rich base liquid, forming a high-concentration phosphorus solution;

[0025] At the same time, the aerobic granular sludge that has released phosphorus is first separated from the phosphorus-rich base liquid through the mud-water separation and transportation system, and then the granular sludge is transported back to the AGS phosphorus absorption reactor to reabsorb and remove phosphorus in the sewage under aerobic conditions.

[0026] The above cycle process is continuously carried out until the phosphorus concentration in the phosphorus-rich solution in the AGS phosphorus release reactor reaches 120-150 mg / L. The high-concentration phosphorus solution in the AGS phosphorus release reactor is then discharged for subsequent phosphorus recovery, and new phosphorus-rich base liquid is added to the AGS phosphorus absorption reactor.

[0027] The technical solution of the present invention has the following advantages over the prior art:

[0028] The process of the present invention can (1) be used for the simultaneous removal and enrichment of phosphorus in municipal sewage or industrial sewage; (2) the phosphorus-rich environment formed can promote the enrichment of polyphosphate bacteria and improve the stability of granular sludge; (3) the loss of aerobic granular sludge is small, and the aerobic phosphorus absorption and anaerobic phosphorus release functions can be continuously exerted; (4) the process is highly flexible, can be operated continuously or intermittently, and has low operating energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a process flow chart of the intermittent operation mode in Example 1; wherein the solid arrow represents the water delivery pipe, the dashed arrow represents the AGS delivery pipe, and the dotted arrow represents the mud-water mixture delivery pipe.

[0030] Figure 2This is a process flow chart of the intermittent operation mode in Example 2; wherein the solid arrow represents the water delivery pipe, the dotted arrow represents the AGS delivery pipe, and the dotted arrow represents the mud-water mixture delivery pipe.

[0031] Explanation of the accompanying symbols: 1-AGS phosphorus absorption reactor, 2-mud and water separation system, 3-AGS phosphorus release reactor, 4-aeration device, 5-stirring device, 6-carbon source adding device. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0033] Example 1

[0034] This embodiment is an intermittent operation mode, that is, the AGS phosphorus absorption reactor 1 is a sequencing batch reactor (SBR, each cycle generally includes water intake, aeration or stirring-aeration, sedimentation, drainage, and idle stages), and operates 4 cycles per day, each cycle is 6 hours, to ensure that the phosphorus in the sewage meets the discharge standard when the water is discharged in each cycle.

[0035] First, the aerobic stage lasts for 4 hours. At the end of the aerobic stage, part (which can be adjusted according to the situation) of the mud-water mixture is separated from the water by the mud-water separation system 2. The aerobic granular sludge that has absorbed phosphorus is transported to the AGS phosphorus release reactor 3 containing a phosphorus-rich base liquid (first water). The carbon source dosing device 6 and the stirring device 5 are started. The polyphosphate bacteria in the aerobic granular sludge absorb the carbon source and release phosphorus under anaerobic conditions. The phosphorus concentration in the phosphorus-rich base liquid continues to rise until the phosphorus release is complete (i.e., the phosphorus concentration in the phosphorus-rich base liquid no longer increases significantly). All the granular sludge in the AGS phosphorus release reactor 3 is separated from the water by the mud-water separation system 2 again and then transported back to the AGS phosphorus absorption reactor 1. Depending on the specific situation, the above process is repeated continuously. After the phosphorus concentration in the phosphorus-rich base liquid in the AGS phosphorus release reactor 3 reaches 120-150 mg / L, the high-concentration phosphorus solution can be recovered and the phosphorus-rich base liquid in the AGS phosphorus release reactor 3 is replaced with clean water or tap water.

[0036] Example 2

[0037] This embodiment is a continuous operation mode. The AGS phosphorus absorption reactor 1 is a continuous flow reactor, which operates aerobically for 5 hours or alternately operates anaerobic-aerobic for 5 hours (AO process, Figure 2 ) to ensure that the phosphorus content in the effluent meets the discharge standards.

[0038] The sludge-water mixture enters the sludge-water separation system 2 from the aerobic zone, with the effluent discharged directly. The retained granular sludge is continuously transported to the AGS phosphorus-release reactor 3 containing a phosphorus-rich base solution. The carbon source dosing device 6 and the stirring device 5 operate continuously, and the phosphorus-accumulating bacteria in the aerobic granular sludge absorb the carbon source and release phosphorus under anaerobic conditions, causing the phosphorus concentration in the phosphorus-rich base solution to continuously rise. The granular sludge, which has released phosphorus, is continuously transported to the sludge-water separation system 2 for separation. After this, the granular sludge is transported back to the AGS phosphorus-absorbing reactor 1 (anaerobic zone). The high-concentration phosphorus solution can be recovered until the phosphorus concentration in the phosphorus-rich base solution reaches 120-150 mg / L. At this time, the phosphorus-rich base solution in the AGS phosphorus-release reactor 3 is replaced with clean water or tap water.

[0039] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A process for removing and enriching phosphorus from sewage based on aerobic granular sludge, characterized in that: The steps include: S11: adding phosphorus-containing wastewater to a reactor containing aerobic granular sludge, and performing aerobic treatment or anaerobic-aerobic alternating treatment, so that phosphorus in the phosphorus-containing wastewater is absorbed by the aerobic granular sludge; the aerobic granular sludge is enriched with phosphorus-accumulating bacteria; S12: performing mud-water separation, the sludge obtained after the mud-water separation enters a reactor containing water, and a degradable carbon source is introduced for anaerobic treatment, so that the phosphorus in the sludge is released into the water; S13: performing secondary mud-water separation to obtain a phosphorus-rich base liquid and secondary sludge, and re-discharging the secondary sludge into the reactor containing aerobic granular sludge, while the phosphorus-rich base liquid remains in the reactor containing water; S14: Repeat steps S11 to S13 several times to complete the wastewater phosphorus removal and enrichment process based on aerobic granular sludge.

2. The process for removing and enriching phosphorus from wastewater based on aerobic granular sludge according to claim 1, characterized in that: The reactor containing aerobic granular sludge is selected from a sequencing batch reactor or a continuous flow reactor; when a sequencing batch reactor is used, aerobic treatment is performed in step S11.

3. The process for removing and enriching phosphorus from wastewater based on aerobic granular sludge according to claim 2, characterized in that: The continuous flow reactor includes an aerobic operation area and an anaerobic operation area.

4. The process for removing and enriching phosphorus from wastewater based on aerobic granular sludge according to claim 2, characterized in that: When the sequencing batch reactor is used, steps S11 to S13 are repeated 4-8 times per day.

5. The process for removing and enriching phosphorus from wastewater based on aerobic granular sludge according to claim 1, characterized in that: In step S12, the wastewater after the mud-water separation is directly discharged or re-enters the reactor described in step S11.

6. The process for removing and enriching phosphorus from wastewater based on aerobic granular sludge according to claim 1, characterized in that: In the step S12, a stirring system is provided at the bottom of the reactor containing water.

7. The process for removing and enriching phosphorus from wastewater based on aerobic granular sludge according to claim 6, characterized in that: In the step S12, the stirring system is used for stirring during anaerobic treatment.

8. The process for removing and enriching phosphorus from wastewater based on aerobic granular sludge according to claim 1, characterized in that: The degradation carbon source is selected from methanol, ethanol, acetic acid or waste water and waste liquid; the waste water and waste liquid contains methanol, ethanol or acetic acid.

9. The process for removing and enriching phosphorus from wastewater based on aerobic granular sludge according to claim 1, characterized in that: In the reactor containing water, the water is selected from clean water or tap water.

10. The process for removing and enriching phosphorus from wastewater based on aerobic granular sludge according to claim 1, characterized in that: In the step S14, the phosphorus concentration in the phosphorus-rich base liquid in the reactor containing water reaches 120-150 mg / L.

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