Device and method for promoting recycling of excess sludge hydrolysate and enhancing nitrogen and phosphorus removal based on nitrogen and phosphorus recovery

Abstract

The invention relates to a device and method for promoting excess sludge hydrolysate reuse and enhancing nitrogen and phosphorus removal based on nitrogen and phosphorus recovery, the device comprises a sludge conditioning pool, excess sludge is added into an inlet of the sludge conditioning pool, an outlet of the sludge conditioning pool is connected with an inlet of a hydrolytic acidification reactor through a sludge feeding pump, and the hydrolytic acidification reactor is arranged in a heating water bath pool; an outlet of the hydrolytic acidification reactor is connected with an inlet of a nitrogen and phosphorus recovery pool through a sludge outlet pump, struvite is discharged from a bottom outlet of the nitrogen and phosphorus recovery pool, and a supernatant outlet of the nitrogen and phosphorus recovery pool is connected with an inlet of the biochemical section through a hydrolysate reflux pump; stirrers are arranged in the sludge conditioning tank, the hydrolytic acidification reactor and the nitrogen and phosphorus recovery tank; according to the method, the excess sludge is subjected to high-temperature hydrolysis to recover nitrogen and phosphorus in the sludge and provide a carbon source for nitrogen and phosphorus removal, and meanwhile, the mainstream nitrogen and phosphorus removal capability is further improved and enhanced in a form of recovering nitrogen and phosphorus by struvite, so that the treatment of the excess sludge really achieves reduction, harmlessness and recycling; good popularization and application feasibility is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization and treatment of excess sludge, and particularly relates to a device and method for promoting the reuse of excess sludge hydrolysis liquid and strengthening nitrogen and phosphorus removal based on nitrogen and phosphorus recovery. Background Art

[0002] A large amount of excess sludge is generated during the sewage treatment process. Improper treatment and disposal of excess sludge will cause greater environmental pollution. Reduction, resource utilization, and harmless treatment are the main research directions for sludge treatment and disposal. Excess sludge contains a large amount of organic matter. The sludge hydrolysis and acidification technology can convert the organic matter in the sludge into volatile fatty acids while reducing the total amount of sludge. The volatile fatty acids produced by the hydrolysis and acidification of excess sludge can be used as the carbon source for the nitrogen and phosphorus removal process, effectively supplementing the deficiencies of rbCOD and VFA in the influent of the sewage treatment plant and improving the nitrogen and phosphorus removal efficiency. By fully exploiting and utilizing the "internal carbon source" of the sewage treatment plant, the cost of the sewage treatment plant can be effectively reduced, and the operation stability and reliability of the sewage treatment system can be improved.

[0003] The hydrolysis acidification liquid produced by the hydrolysis and acidification of excess sludge contains considerable amounts of dissolved proteins, polysaccharides, and VFAs. At the same time, the nitrogen and phosphorus in the excess sludge are also released. Both nitrogen and phosphorus are key elements in industry and agriculture and play an important role in economic development. Phosphate rock is a non-renewable resource. Therefore, recovering nitrogen and phosphorus from the hydrolysis acidification liquid has double benefits of economy and environmental protection, which meets the needs of ecological civilization construction; the struvite crystallization method can not only simultaneously recover nitrogen and phosphorus in the hydrolysis liquid but also produce struvite with economic value, which can be used as an agricultural slow-release fertilizer.

[0004] Currently, there is no literature reporting the combination of excess sludge hydrolysis acidification with struvite recovery of nitrogen and phosphorus in the supernatant liquid to strengthen mainstream nitrogen and phosphorus removal. Summary of the Invention

[0005] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a device and method for promoting the reuse of excess sludge hydrolysis liquid and strengthening nitrogen and phosphorus removal based on nitrogen and phosphorus recovery. By performing high-temperature hydrolysis on excess sludge to recover nitrogen and phosphorus in the sludge and provide a carbon source for nitrogen and phosphorus removal, and at the same time further improving the ability to strengthen mainstream nitrogen and phosphorus removal in the form of struvite recovery of nitrogen and phosphorus, the treatment of excess sludge can truly achieve reduction, harmlessness, and resource utilization, and has good feasibility for popularization and application.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A device for promoting the reuse of excess sludge hydrolyzate based on nitrogen and phosphorus recovery to strengthen denitrification and phosphorus removal comprises a sludge conditioning tank 1, excess sludge is added to the inlet of the sludge conditioning tank 1, the outlet of the sludge conditioning tank 1 is connected to the inlet of a hydrolysis acidification reactor 5 through a sludge feed pump 2, the hydrolysis acidification reactor 5 is placed in a heating water bath 4, the outlet of the hydrolysis acidification reactor 5 is connected to the inlet of a nitrogen and phosphorus recovery tank 7 through a sludge discharge pump 6, struvite is discharged from the bottom outlet of the nitrogen and phosphorus recovery tank 7, and the supernatant outlet of the nitrogen and phosphorus recovery tank 7 is connected to the inlet of a biochemical section 9 through a hydrolyzate reflux pump 8.

[0008] The sludge conditioning tank 1, the hydrolysis acidification reactor 5, and the nitrogen and phosphorus recovery tank 7 are provided with a stirrer 3.

[0009] A method for utilizing a device for promoting the reuse of excess sludge hydrolyzate based on nitrogen and phosphorus recovery to enhance denitrification and phosphorus removal comprises the following steps:

[0010] 1) The residual sludge discharged from the secondary sedimentation tank of the domestic sewage treatment plant and subjected to slurry treatment is transferred to the sludge conditioning tank 1, and the moisture content of the sludge is adjusted to 91% to 93% in the sludge conditioning tank 1; the adjusted sludge is then fed into the hydrolysis acidification reactor 5 by the sludge feed pump 2, and a high-temperature hydrolysis reaction is carried out for 2.5 to 3.5 days at a reaction temperature of 44° C. to 46° C. to increase the dissolution rate of intracellular solubles in the sludge; during the reaction process, the stirrer 3 continuously stirs at a speed of 80 to 100 r / min to achieve hydrolysis and acidification of the residual sludge;

[0011] 2) MgCl2 is added to the supernatant of the residual sludge after hydrolysis and acidification to form struvite with N and P dissolved by high-temperature hydrolysis, the pH of the hydrolysis and acidification solution is adjusted to 9-10, the molar ratio of the reaction elements n(Mg) : n(P) = 1.4:1, the stirring speed is 200-300 r / min, and the reaction time is 10-12 min;

[0012] 3) The supernatant treated in step 2) is returned to the biochemical section 9 to provide a carbon source for denitrification and phosphorus removal.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] (1) While reducing the amount of excess sludge through high-temperature hydrolysis, the present invention fully develops and utilizes the "internal carbon source" to provide VFAs for the biochemical stage, greatly saving the addition of carbon sources and reducing the dependence on the carbon source of the influent, which is in line with the current situation of low carbon sources in the influent of sewage treatment plants.

[0015] (2) The present invention simultaneously recovers nitrogen and phosphorus from the high-temperature hydrolysis acidification liquid through the struvite crystallization method, which has both economic and environmental benefits, and meets the needs of ecological and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of an apparatus for enhancing nitrogen and phosphorus removal by promoting the reuse of hydrolyzed liquid of excess sludge based on nitrogen and phosphorus recovery according to an embodiment of the present invention.

[0017] In the figure: 1, sludge conditioning tank; 2, sludge feed pump; 3, stirrer; 4, heating water bath tank; 5, hydrolysis acidification reactor; 6, sludge discharge pump; 7, nitrogen and phosphorus recovery tank; 8, hydrolyzed liquid reflux pump; 9, biochemical section. Specific embodiments

[0018] The present invention will be described in detail below in conjunction with embodiments and drawings.

[0019] Embodiment 1: As Figure 1 shown, an apparatus for enhancing nitrogen and phosphorus removal by promoting the reuse of hydrolyzed liquid of excess sludge based on nitrogen and phosphorus recovery includes a sludge conditioning tank 1. Excess sludge discharged from the secondary sedimentation tank of a domestic sewage treatment plant is added to the inlet of the sludge conditioning tank 1. The outlet of the sludge conditioning tank 1 is connected to the inlet of the hydrolysis acidification reactor 5 through a sludge feed pump 2. The hydrolysis acidification reactor 5 is placed in the heating water bath tank 4. The outlet of the hydrolysis acidification reactor 5 is connected to the inlet of the nitrogen and phosphorus recovery tank 7 through a sludge discharge pump 6. Struvite is discharged from the bottom outlet of the nitrogen and phosphorus recovery tank 7. The supernatant outlet of the nitrogen and phosphorus recovery tank 7 is connected to the inlet of the biochemical section 9 through a hydrolyzed liquid reflux pump 8; Stirrers 3 are provided in the sludge conditioning tank 1, the hydrolysis acidification reactor 5, and the nitrogen and phosphorus recovery tank 7.

[0020] A method for using an apparatus for enhancing nitrogen and phosphorus removal by promoting the reuse of hydrolyzed liquid of excess sludge based on nitrogen and phosphorus recovery includes the following steps:

[0021] 1) Transfer the excess sludge after being discharged from the secondary sedimentation tank of a domestic sewage treatment plant and subjected to pulping treatment to the sludge conditioning tank 1, and adjust the moisture content of the sludge to 92% in the sludge conditioning tank 1; The adjusted sludge is then fed into the hydrolysis acidification reactor 5 by the sludge feed pump 2, and a high-temperature hydrolysis reaction is carried out for 3 days at a reaction temperature of 45 °C to increase the dissolution rate of intracellular substances in the sludge; During the reaction process, the stirrer 3 continuously stirs at a rotation speed of 90 r / min to achieve the hydrolysis acidification of the excess sludge;

[0022] 2) Add MgCl2 to the supernatant of the excess sludge after hydrolysis acidification to form struvite with N and P dissolved by high-temperature hydrolysis, adjust the pH of the hydrolyzed acidified liquid to 10, the molar ratio of reaction elements n(Mg):n(P)=1.4:1, the stirring speed is 300 r / min, and the reaction time is 10 min;

[0023] 3) Return the supernatant treated in step 2) to the biochemical section 9 to provide a carbon source for nitrogen and phosphorus removal.

[0024] The technical parameters and effects of Embodiment 1 are summarized in Table 1 as follows.

[0025] Example 2: The device in Example 2 is the same as that in Example 1; the difference in the method from that in Example 1 is as follows: In step 1), the moisture content of the sludge is adjusted to 91%, and a high-temperature hydrolysis reaction is carried out for 3.5 days at a reaction temperature of 46°C, with the stirrer 3 continuously stirring at a rotation speed of 100 r / min; in step 2), the pH of the hydrolyzed acidified liquid is adjusted to 9, the molar ratio of the reaction elements n(Mg):n(P) = 1.4:1, the stirring speed is 200 r / min, and the reaction time is 12 min.

[0026] The technical parameters and effects of Example 2 are summarized in Table 1 as follows.

[0027] Example 3: The device in Example 3 is the same as that in Example 1; the difference in the method from that in Example 1 is as follows: In step 1), the moisture content of the sludge is adjusted to 93%, and a high-temperature hydrolysis reaction is carried out for 2.5 days at a reaction temperature of 44°C, with the stirrer 3 continuously stirring at a rotation speed of 80 r / min; in step 2), the pH of the hydrolyzed acidified liquid is adjusted to 9, the molar ratio of the reaction elements n(Mg):n(P) = 1.4:1, the stirring speed is 260 r / min, and the reaction time is 11 min.

[0028] The technical parameters and effects of Example 3 are summarized in Table 1 as follows.

[0029] Table 1 Summary of the implementation effects of Examples 1 - 3

[0030] Control parameters and operating effect parameters Example 1 Example 2 Example 3 Agitator speed r / min 90 100 80 Sludge moisture content % 92 91 93 High-temperature hydrolysis reaction temperature °C 45 46 44 High-temperature hydrolysis reaction time d 3 3.5 2.5 pH of hydrolyzed acidification liquid 10 9 9 Agitator speed r / min 300 200 260 Action time min after adding MgCl2 10 12 11 COD of high-temperature hydrolysis liquid mg / L 6000 6200 5500 C / N % of high-temperature hydrolysis liquid 7.45 7.5 7.4 C / P % of high-temperature hydrolysis liquid 750 700 700 Phosphate recovery rate % 96.16 95.21 94.26

[0031] In the process of resource utilization, reduction, and harmless treatment of sludge using the above examples, through the high-temperature hydrolysis acidification of excess sludge, the organic matter content in the supernatant increased by about 26 times (from about 225 mg / L to about 6000 mg / L), and at the same time, the content of volatile fatty acids accounted for about 45% of the SCOD content, providing a considerable amount of high-quality carbon sources for nitrogen and phosphorus removal in the biochemical section; secondly, when the Mg:P molar ratio is 1.4:1, the highest recovery rate of phosphate can reach 96.16%, which can further recover and utilize the resources in the hydrolyzed acidified liquid.

[0032] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An apparatus for enhancing nitrogen and phosphorus removal by promoting the reuse of the hydrolysis liquid of excess sludge based on nitrogen and phosphorus recovery, comprising a sludge conditioning tank (1), characterized in that: The excess sludge is added to the inlet of the sludge conditioning tank (1). The outlet of the sludge conditioning tank (1) is connected to the inlet of the hydrolysis acidification reactor (5) through the sludge feed pump (2). The hydrolysis acidification reactor (5) is placed in the heating water bath tank (4). The outlet of the hydrolysis acidification reactor (5) is connected to the inlet of the nitrogen and phosphorus recovery tank (7) through the sludge discharge pump (6). The bottom outlet of the nitrogen and phosphorus recovery tank (7) discharges struvite. The supernatant outlet of the nitrogen and phosphorus recovery tank (7) is connected to the inlet of the biochemical section (9) through the hydrolysis liquid reflux pump (8).

2. The device according to claim 1, characterized in that: Stirrers (3) are provided in the sludge conditioning tank (1), the hydrolysis acidification reactor (5), and the nitrogen and phosphorus recovery tank (7).

3. A method for using the device for enhancing nitrogen and phosphorus removal by promoting the reuse of the hydrolyzed solution of excess sludge based on nitrogen and phosphorus recovery according to any one of claims 1-2, characterized in that, It includes the following steps: 1) Transfer the excess sludge discharged from the secondary sedimentation tank of the domestic sewage treatment plant and subjected to pulping treatment to the sludge conditioning tank (1), and adjust the moisture content of the sludge in the sludge conditioning tank (1) to 91% - 93%; the adjusted sludge is then fed into the hydrolysis acidification reactor (5) by the sludge feed pump (2), and a high-temperature hydrolysis reaction is carried out for 2.5 - 3.5 d at a reaction temperature of 44°C - 46°C; during the reaction process, the stirrer (3) continuously stirs at a rotation speed of 80 - 100 r / min; 2) Add MgCl2 to the supernatant of the excess sludge after hydrolysis acidification to form struvite with N and P dissolved out by high-temperature hydrolysis, adjust the pH of the hydrolysis acidification liquid to 9 - 10, the molar ratio of reaction elements n(Mg)∶n(P) = 1.4∶1, the stirring speed is 200 - 300 r / min, and the reaction time is 10 - 12 min; 3) Return the supernatant treated in step 2) to the biochemical section (9).

4. The method according to claim 3, wherein: It includes the following steps: 1) Transfer the excess sludge discharged from the secondary sedimentation tank of the domestic sewage treatment plant and subjected to pulping treatment to the sludge conditioning tank (1), and adjust the moisture content of the sludge in the sludge conditioning tank (1) to 92%; the adjusted sludge is then fed into the hydrolysis acidification reactor (5) by the sludge feed pump (2), and a high-temperature hydrolysis reaction is carried out for 3 d at a reaction temperature of 45°C to increase the dissolution rate of intracellular substances in the sludge; during the reaction process, the stirrer (3) continuously stirs at a rotation speed of 90 r / min to achieve hydrolysis acidification of the excess sludge; 2) Add MgCl2 to the supernatant of the excess sludge after hydrolysis acidification to form struvite with N and P dissolved out by high-temperature hydrolysis, adjust the pH of the hydrolysis acidification liquid to 10, the molar ratio of reaction elements n(Mg)∶n(P) = 1.4∶1, the stirring speed is 300 r / min, and the reaction time is 10 min; 3) Return the supernatant treated in step 2) to the biochemical section (9) to provide a carbon source for nitrogen and phosphorus removal.

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