Method for treating domestic sewage, sludge and carcasses of sick animals

Abstract

The present application relates to a kind of domestic sewage, sludge and dead animal collaborative processing method, comprising: sludge hydrolysis treatment, dead animal processing method after and domestic sewage are mixed to prepare pulp, the above-mentioned two are mixed, overflow liquid and underflow liquid are obtained by cyclone separation of mixed liquid, overflow liquid is fermented to produce acid to prepare carbon source, underflow liquid high-efficiency anaerobic digestion produces biogas, nutrient soil is prepared after biogas residue dewatering, dewatering liquid and sewage treatment plant influent are mixed together for processing.Compared with prior art, the present application can make full use of steam waste heat after sludge hydrolysis, and a large amount of pulping water can be saved by applying sewage and dead animal pulping, without the need to build dead animal processing station, harmless treatment of dead animal can be realized in sewage treatment plant, sewage plant does not need to purchase commercial carbon source, and effective treatment and resource utilization of solid phase and liquid phase in sludge and dead animal can be realized, and the overall treatment cost of sewage, sludge and dead animal is expected to be greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of resource and environmental protection technology, specifically relating to a method for the co-treatment of domestic sewage, sludge and dead animals. Background Technology

[0002] Many wastewater treatment plants in my country suffer from insufficient carbon-to-nitrogen ratios in their influent, failing to meet the requirements for nitrogen and phosphorus removal. This necessitates the addition of commercial carbon sources such as methanol and sodium acetate, resulting in a high proportion of carbon source costs in the operating costs of wastewater treatment plants.

[0003] With the significant improvement in my country's wastewater treatment capacity, sludge production has also increased year by year. Anaerobic digestion after hot hydrolysis of sludge is one of the main methods of sludge treatment. Hot hydrolysis technology involves adding sludge and saturated steam at 150–260°C to a closed reactor. The saturated steam heats the sludge, thereby breaking down the sludge cell walls, dissolving organic matter, and killing pathogens. Anaerobic digestion of the hydrolyzed sludge can reduce, stabilize, and render the sludge harmless, while also producing biogas for resource recovery. While sludge has high nitrogen and phosphorus content, the organic matter content of sludge in most parts of my country, especially in the south, is low. Therefore, the biogas production capacity of anaerobic digestion after hot hydrolysis remains insufficient, limiting the application and promotion of anaerobic digestion technology in southern my country.

[0004] Anaerobic digestion can degrade large amounts of solid organic matter. Currently, anaerobic digestion of sludge alone or in combination with other organic matter is widely used. During anaerobic digestion, a large amount of organic matter is removed through methanogenesis, while organic nitrogen is converted to ammonia nitrogen through ammonification. The resulting anaerobic digestate exhibits high ammonia nitrogen and a low carbon-to-nitrogen ratio. A small amount of anaerobic digestate can be treated together with wastewater influent, but large amounts can burden wastewater treatment plants and affect effluent quality. Additionally, sludge is also frequently used for acid production through fermentation alone or in combination with other organic matter. However, due to the short fermentation cycle, a large amount of solid organic matter cannot be effectively utilized, and incomplete stabilization remains a problem. How to effectively treat and utilize the solid and liquid phases of sludge and dead animal remains one of the main challenges.

[0005] To address the above problems, this invention provides a method for the co-treatment of domestic sewage, sludge, and dead animals. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a method for the co-treatment of domestic sewage, sludge, and dead animals; it achieves effective treatment and resource utilization of the solid and liquid phases in sludge and dead animals.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention relates to a method for the co-treatment of domestic sewage, sludge, and dead animals, comprising the following steps:

[0009] S1. The sludge is subjected to hot hydrolysis to obtain hot hydrolysis sludge slurry;

[0010] S2. Wet treatment of diseased and dead animals:

[0011] S2-1. The saturated steam obtained from the thermal hydrolysis of sludge in step S1 is used for the wet treatment of dead animals after passing through a heat exchanger.

[0012] S2-2. After the humidified dead animals are crushed, impurities removed, and oil removed, they are mixed with domestic sewage to make pulp, thus obtaining dead animal pulp.

[0013] S3. The hot hydrolysis sludge slurry and the slurry of the dead animals are mixed, and the mixture is separated by hydrocyclone to obtain overflow and underflow.

[0014] S4. Ferment the overflow liquid to obtain hydrolyzed acidified liquid;

[0015] S5. Anaerobic digestion of the underflow liquid;

[0016] S6. The anaerobic digested sludge is separated into solid and liquid components by filter press.

[0017] In one embodiment of the present invention, in step S1, the initial moisture content of the sludge is 75% to 85%.

[0018] In one embodiment of the present invention, in step S1, the conditions for the hydrolysis of the sludge are: hydrolysis temperature of 150℃~250℃ and time of 10min~60min.

[0019] In one embodiment of the present invention, in step S2, the particle size of the slurry from the dead animals is ≤10mm and the solid content is 10% to 20%.

[0020] In one embodiment of the present invention, in step S2, the humidification treatment conditions are: humidification temperature of 135℃~160℃ and time of 30min~60min.

[0021] In one embodiment of the present invention, in step S3, the solid content ratio of the hot hydrolysis sludge slurry and the wet effluent from dead animals is 1:5 to 5:1.

[0022] In one embodiment of the present invention, in step S3, the flow rate ratio of the underflow liquid to the overflow liquid is 1:2 to 1:6.

[0023] In one embodiment of the present invention, in step S4, the solid residence time for fermentation to produce acid is controlled to be 3-5 days, and the fermentation temperature is controlled to be 25℃-50℃.

[0024] In one embodiment of the present invention, in step S4, the hydrolyzed acidified liquid is used as a carbon source for nitrogen and phosphorus removal in wastewater treatment.

[0025] In one embodiment of the present invention, step S5 further includes using the biogas produced by anaerobic digestion as an energy source for a steam boiler to produce steam required for sludge hydrolysis. Currently, for some sludge with low organic matter content, the biogas production capacity after anaerobic digestion following hydrolysis is still insufficient, limiting the application and promotion of anaerobic digestion technology in southern my country. However, the present invention improves the methanogenic capacity through the synergistic anaerobic digestion of sludge and dead animals, which can provide sufficient heat sources for sludge treatment processes such as steam boilers and anaerobic digestion facility insulation.

[0026] In one embodiment of the present invention, in step S5, the solid retention time of the anaerobic digestion is controlled to be 12 days to 21 days, and the digestion temperature is controlled to be 35°C to 38°C.

[0027] In one embodiment of the present invention, in step S6, a plate and frame filter press is used for solid-liquid separation; the pressure of plate and frame dewatering is controlled at 1.5MPa to 6MPa, and the time is controlled at 20min to 40min.

[0028] As one embodiment of the present invention, step S6 further includes crushing the solid particles after dewatering the biogas residue to a particle size ≤10mm to obtain nutrient soil.

[0029] As one embodiment of the present invention, step S6 further includes treating the liquid after dewatering the biogas residue together with the influent of the sewage treatment plant.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1) Constructing a separate wet processing station for dead animals requires a large amount of steam, and the wet processing of dead animals also generates wastewater, necessitating the construction of wastewater treatment facilities. This invention fully utilizes the waste heat from the hydrolysis of sludge to process dead animals. Using wastewater and dead animals for pulping saves a significant amount of water used for pulping, eliminating the need for a new dead animal processing station; the harmless treatment of dead animals can be achieved within the wastewater treatment plant. Furthermore, the composition and basic characteristics of dead animals and sludge are highly complementary. Compared to separate digestion, synergistic anaerobic digestion effectively balances the nutrients in the anaerobic digestion substrate, thereby improving the stability and efficiency of the anaerobic digestion system and significantly increasing biogas production. Moreover, during the high-pressure pressing process, the meat and bone meal in the dead animals provides a water passage for the dewatering process, improving sludge dewatering efficiency compared to separate sludge dewatering.

[0032] 2) Anaerobic digestion can degrade a large amount of solid organic matter. Currently, there are many applications of anaerobic digestion of sludge alone or anaerobic digestion of sludge in combination with other organic matter. Because a large amount of organic matter is removed through methanogenesis during anaerobic digestion, and organic nitrogen is converted into ammonia nitrogen through ammonification, the biogas slurry produced by anaerobic digestion is characterized by high ammonia nitrogen and low carbon-nitrogen ratio. A small amount of anaerobic digestion biogas slurry can be treated together with the influent of the sewage treatment plant, but a large amount of biogas slurry will burden the sewage treatment plant and affect the quality of the effluent. In addition, there are many applications of sludge fermentation to produce acid alone or sludge fermentation in combination with other organic matter to produce acid. However, due to the short fermentation acid production cycle, a large amount of solid organic matter cannot be effectively utilized, and there is still a problem of incomplete stabilization. This invention controls the solid content ratio of sludge hydrolysis liquid and dead animal wet liquid, separates the mixed liquid using a hydrocyclone separator, and further controls the flow ratio of underflow and overflow liquid. This results in an overflow liquid with high dissolved solids content and low insoluble solids content, and an underflow liquid with low dissolved solids content and high insoluble solids content. The overflow liquid is highly efficient for fermentation and acid production, and the acidified liquid can replace commercial carbon sources for denitrification, phosphorus removal, and carbon source addition in wastewater treatment. The underflow liquid undergoes anaerobic digestion, producing biogas with high efficiency and significantly reducing the volume of the anaerobic digester. Ultimately, this invention achieves effective treatment and resource utilization of the solid and liquid phases in sludge and dead animals.

[0033] 3) The nutrient soil prepared from biogas residue is rich in nutrients such as humic acid, calcium, nitrogen, phosphorus, and potassium. Calcium ions can replace sodium ions in saline-alkali soil through ion exchange. The replaced sodium ions complex with humic acid functional groups to form sodium humate, thereby effectively reducing soil alkalinity, stimulating plant growth, enhancing their salt resistance, improving seed germination rate, and promoting soil improvement and ecological protection forest construction in saline-alkali areas. Attached Figure Description

[0034] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0035] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0036] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0037] Example 1

[0038] like Figure 1 As shown, sludge with a moisture content of 83% is first hydrolyzed at 165℃ for 30 minutes to obtain sludge hydrolysate. The saturated steam from the hydrolyzed sludge is then passed through a heat exchanger, and dead animals are treated with a wet treatment method at 135℃ for 30 minutes. The wetted dead animals are then mixed with domestic sewage, crushed, impurities removed, oil removed, and pulped to obtain a dead animal slurry with a particle size ≤10mm and a solids content of 15%. The sludge hydrolysate and the dead animal slurry are then combined... The two liquids are mixed with a solid content ratio of 1:1. The mixture is then separated by cyclone separation to obtain overflow and underflow, with a flow rate ratio of 1:3. The overflow is fermented to obtain hydrolyzed acidified liquid, with a solid residence time of 3 days and a fermentation temperature of 35℃. The hydrolyzed acidified liquid replaces commercial carbon sources in wastewater treatment for nitrogen and phosphorus removal, achieving Class A discharge standards. The underflow is anaerobically digested at 38℃ for 12 days, yielding a biogas production of 352 m³. 3 / t DS, the biogas produced provides steam for the thermal hydrolysis of sludge through a steam boiler, and the whole process does not require additional energy. After the biogas residue is conditioned with 0.3% PAM, it is pressed for 30 minutes under 2MPa conditions using a plate and frame dewatering machine. The moisture content of the dewatered cake is 57%. The dewatered cake is crushed to a particle size of less than 10mm to obtain nutrient soil. The dewatered liquid is treated together with the influent of the sewage treatment plant.

[0039] In areas with saline-alkali soil, this nutrient soil is mixed with the soil at a ratio of 20% by weight, and then camel thorn is planted at a ratio of 1m. 2 In the saline-alkali soil, the amount of nutrient soil used was 2.5 kg. The results showed that soil porosity increased from 40.32% to 45.75%, electrical conductivity decreased from 331.74 μS / cm to 323.18 μS / cm, pH decreased from 10.66 to 9.89, and Na+ decreased. 2+ The concentration of Ca decreased from 898.78 mg / kg to 718.34 mg / kg. 2+ The concentration of Mg increased from 11.06 mg / kg to 36.62 mg / kg. 2+ The concentration of Cl increased from 105 mg / kg to 189.72 mg / kg. - The concentration was reduced from 25.56 mg / kg to 19.25 mg / kg, and the seed germination rate reached 94%.

[0040] Example 2

[0041] All other conditions and methods in this embodiment are the same as in Embodiment 1, except that:

[0042] (1) In this embodiment, the sludge hot hydrolysis slurry and the slurry of dead animals are mixed, and the solid content ratio of the two is 5:1;

[0043] (2) In this embodiment, the overflow liquid is fermented to obtain hydrolyzed acidified liquid, the solid residence time of fermentation is controlled to be 3 days, and the fermentation temperature is controlled to be 45℃.

[0044] (3) In this embodiment, the underflow liquid was anaerobically digested at 38°C for 18 days.

[0045] Hydrolyzed acidified liquid replaces commercial carbon sources in wastewater treatment processes for nitrogen and phosphorus removal, achieving Class A discharge standards for effluent. Biogas produced from anaerobic digestion provides steam for sludge hydrolysis via a steam boiler, eliminating the need for additional energy inputs. In areas with saline-alkali soil, this nutrient-rich soil, mixed with other soil at a weight ratio of 20%, is used to plant camel thorn, relative to a 1m... 2 The saline-alkali soil was treated with 2.5 kg of nutrient soil, and the seed germination rate was found to be 90%.

[0046] Example 3

[0047] All other conditions and methods in this embodiment are the same as in Embodiment 1, except that:

[0048] (1) In this embodiment, the sludge hot hydrolysis slurry and the slurry of dead animals are mixed, and the solid content ratio of the two is 1:5;

[0049] (2) In this embodiment, the overflow liquid is fermented to obtain hydrolyzed acidified liquid, the solid residence time of fermentation is controlled to be 4 days, and the fermentation temperature is controlled to be 25℃.

[0050] Hydrolyzed acidified liquid replaces commercial carbon sources in wastewater treatment processes for nitrogen and phosphorus removal, achieving Class A discharge standards for effluent. Biogas produced from anaerobic digestion provides steam for sludge hydrolysis via a steam boiler, eliminating the need for additional energy inputs. In areas with saline-alkali soil, this nutrient-rich soil, mixed with other soil at a weight ratio of 20%, is used to plant camel thorn, relative to a 1m... 2 The saline-alkali soil was treated with 2.5 kg of nutrient soil, and the seed germination rate was found to be 93%.

[0051] Example 4

[0052] All other conditions and methods in this embodiment are the same as in Embodiment 1, except that:

[0053] (1) In this embodiment, the mixture of sludge hydrolysis slurry and dead animal slurry is separated by cyclone separation to obtain overflow and underflow, with the flow ratio of underflow to overflow being 1:2.

[0054] (2) In this embodiment, the overflow liquid is fermented to obtain hydrolyzed acidified liquid, the solid residence time of fermentation is controlled to be 5 days, and the fermentation temperature is controlled to be 35℃.

[0055] Hydrolyzed acidified liquid replaces commercial carbon sources in wastewater treatment processes for nitrogen and phosphorus removal, achieving Class A discharge standards for effluent. Biogas produced from anaerobic digestion provides steam for sludge hydrolysis via a steam boiler, eliminating the need for additional energy inputs. In areas with saline-alkali soil, this nutrient-rich soil, mixed with other soil at a weight ratio of 20%, is used to plant camel thorn, relative to a 1m... 2 The saline-alkali soil was treated with 2.5 kg of nutrient soil, and the seed germination rate was found to be 94%.

[0056] Example 5

[0057] All other conditions and methods in this embodiment are the same as in Embodiment 1, except that:

[0058] (1) In this embodiment, the mixture of sludge hydrolysis slurry and dead animal slurry is separated by cyclone separation to obtain overflow and underflow, with the flow ratio of underflow to overflow being 1:6.

[0059] (2) In this embodiment, the overflow liquid is fermented to obtain hydrolyzed acidified liquid, the solid residence time of fermentation is controlled to be 4 days, and the fermentation temperature is controlled to be 50℃.

[0060] Hydrolyzed acidified liquid replaces commercial carbon sources in wastewater treatment processes for nitrogen and phosphorus removal, achieving Class A discharge standards for effluent. Biogas produced from anaerobic digestion provides steam for sludge hydrolysis via a steam boiler, eliminating the need for additional energy inputs. In areas with saline-alkali soil, this nutrient-rich soil, mixed with other soil at a weight ratio of 20%, is used to plant camel thorn, relative to a 1m... 2 The saline-alkali soil was treated with 2.5 kg of nutrient soil, and the seed germination rate was found to be 92%.

[0061] Comparative Example 1

[0062] The other conditions and methods in this comparative example are the same as in Example 1. The difference from Example 1 is that the sludge hot hydrolysis slurry and the wet slurry of dead animals are mixed, and the solid content ratio of the two is 8:1.

[0063] The biogas production from anaerobic digestion is 256 m³. 3 / t DS, in areas with saline-alkali soil, mix this nutrient soil with the soil at a ratio of 20% by weight, and then plant camel thorns, relative to 1m 2 The saline-alkali soil was treated with 2.5 kg of nutrient soil, and the seed germination rate was found to be 82%.

[0064] Comparative Example 2

[0065] The other conditions and methods in this comparative example are the same as in Example 1. The difference from Example 1 is that the above mixture is separated by cyclone separation to obtain overflow liquid and underflow liquid, and the flow ratio of overflow liquid to underflow liquid is 10:1.

[0066] Hydrolyzed acidified liquid is used as a substitute for commercial carbon sources in wastewater treatment processes for nitrogen and phosphorus removal. The SS in the effluent is 12 mg / L, which exceeds the Class A discharge standard of SS ≤ 10 mg / L.

[0067] In summary, this invention provides a method for the co-treatment of domestic sewage, sludge, and dead animals, comprising: hydrolyzing sludge to obtain sludge hydrolysate; treating dead animals by wet processing to obtain dead animal wet matter; mixing the sludge hydrolysate and dead animal wet matter to obtain a mixed liquid; separating the mixed liquid by hydrocyclone separation to obtain overflow and underflow; fermenting the overflow to obtain acidified liquid; anaerobic digesting the underflow to produce biogas; dewatering the biogas residue to prepare nutrient soil; and mixing the dewatered liquid with the influent of a sewage treatment plant for joint treatment. Compared with existing technologies, this invention can fully utilize the waste heat from the hydrolysate of sludge, save a significant amount of water for pulping by using sewage and dead animals for pulping, eliminate the need for new dead animal treatment plants, achieve harmless treatment of dead animals within the sewage treatment plant, eliminate the need for sewage treatment plants to purchase commercial carbon sources, and achieve effective treatment and resource utilization of the solid and liquid phases in sludge and dead animals, and is expected to significantly reduce the overall treatment cost of sewage, sludge, and dead animals.

[0068] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for co-treatment of domestic sewage, sludge and carcasses of sick animals, characterized in that, The method comprises the following steps: S1, performing thermal hydrolysis treatment on sludge to obtain sludge thermal hydrolysis slurry; S2, performing wetting method treatment on dead animals: S2-1, using saturated steam after the thermal hydrolysis of the sludge in step S1 to perform wetting method treatment on dead animals after passing through a heat exchanger; S2-2, mixing the wetted dead animals and domestic sewage, and then performing crushing, impurity removal and oil removal to obtain dead animal slurry; S3, mixing the sludge thermal hydrolysis slurry and the dead animal slurry, and then performing cyclone separation on the mixture to obtain overflow liquid and underflow liquid; S4, fermenting the overflow liquid to obtain hydrolysis acidification liquid; S5, performing anaerobic digestion on the underflow liquid; S6, performing solid-liquid separation on the sludge after anaerobic digestion by pressure filtration.

2. The method for co-treatment of domestic sewage, sludge and carcass of sick animals according to claim 1, characterized in that, In step S3, the solid content ratio of the sludge thermal hydrolysis slurry and the dead animal slurry is 1:5-5:

1.

3. The method for co-treatment of domestic sewage, sludge and carcass of sick animals according to claim 1, characterized in that, In step S3, the flow ratio of the underflow liquid and the overflow liquid is 1:2-1:

6.

4. The method for co-treatment of domestic sewage, sludge and carcass of sick animals according to claim 1, characterized in that, In step S4, the solid retention time of the fermentation is controlled to be 3-5 days, and the fermentation temperature is controlled to be 25-50℃.

5. The method for co-treatment of domestic sewage, sludge and carcass of sick animals according to claim 1, characterized in that, In step S4, the hydrolysis acidification liquid is used as a carbon source for denitrification and phosphorus removal in sewage treatment.

6. The method of co-treatment of domestic sewage, sludge and carcasses of sick animals according to claim 1, characterized in that, In step S5, the solid retention time of the anaerobic digestion is controlled to be 12-21 days, and the digestion temperature is controlled to be 35-38℃.

7. The method of co-treatment of domestic sewage, sludge and carcasses of sick animals according to claim 1, characterized in that, In step S5, the biogas produced by anaerobic digestion is used as energy for a steam boiler to produce steam required for sludge thermal hydrolysis.

8. The method of co-treatment of domestic sewage, sludge and carcasses of sick animals according to claim 1, characterized in that, In step S6, plate and frame filter presses are used for solid-liquid separation; the pressure for plate and frame dewatering is controlled to be 1.5-6 MPa, and the pressing time is controlled to be 20-40 min.

9. The method of co-treatment of domestic sewage, sludge and carcasses of sick animals according to claim 1, characterized in that, In step S6, the solid after dewatering of the biogas residue is crushed to a particle size of ≤10 mm to obtain nutrient soil.

10. The method of co-treatment of domestic sewage, sludge and carcasses of sick animals according to claim 1, characterized in that, In step S6, the liquid after dewatering of the biogas residue is treated together with influent from a sewage treatment plant.

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