A method for treating the entire amount of sludge from a municipal sewage treatment plant as a resource

Abstract

The present invention discloses a method for treating the full amount of sludge from a municipal sewage treatment plant as a resource, and relates to the technical field of environmental engineering. The present invention uses ozone to oxidize the contents of sludge cells, uses black soldier fly pupa shell slurry and polydimethyldiallyl ammonium chloride as conditioning materials and materials for improving the water retention performance of residues, thereby achieving the degradation of volatile organic matter in the sludge and the efficient removal of heavy metals in the sludge, and then preparing the dehydrated product into a soil water retention material, and the heavy metals separated from the sludge are recovered in the form of ferrites, and the organic carbon in the liquid phase is used as a carbon source for the sewage treatment plant, thereby achieving the full amount of sludge as a resource.

Description

Technical Field

[0001] The invention relates to the technical field of environmental engineering, and in particular to a method for processing sludge from a municipal sewage treatment plant in full resource utilization. Background Art

[0002] In recent years, sludge has been produced in large quantities as a by-product of the main process of urban sewage treatment plants and has become the largest urban organic solid waste after urban domestic waste.

[0003] The current sludge disposal methods mainly include land use, incineration, landfill and building material utilization. However, due to the low organic matter content and high sulfide content of sludge, conventional anaerobic digestion is difficult to make the sludge reach the stabilization standard after treatment; sludge is often enriched with a large amount of heavy metals, which will also bring certain risks to subsequent disposal, and conventional stabilization methods often have high processing costs and huge investment costs, and also cause waste of resources.

[0004] Therefore, if the full treatment of sludge can be achieved to make it harmless, reduce its volume and make it a resource, it will be of great significance to reduce the treatment cost of sludge in sewage treatment plants and promote the resource utilization of sludge. Summary of the invention

[0005] The purpose of the present invention is to provide a method for fully recycling sludge from urban sewage treatment plants, so as to reduce the organic matter content in the sludge, efficiently remove heavy metals, and improve resource utilization, thereby achieving low-cost treatment of sludge and efficient recycling of resources.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a method for treating the entire amount of sludge from a municipal sewage treatment plant as a resource, comprising the following steps:

[0008] (1) adding ferrous sulfate to concentrated sludge from a municipal sewage treatment plant and performing ozone oxidation treatment to obtain ozone-treated sludge;

[0009] (2) adding pupa shell powder slurry and polydimethyldiallyl ammonium chloride to the sludge after ozone treatment so that the pH value of the sludge is 6.1-6.8 to obtain conditioned sludge;

[0010] The method for preparing the pupa shell powder slurry comprises the following steps: grinding the pupa shell of black soldier fly, adding sulfuric acid and soaking it to obtain the pupa shell powder slurry;

[0011] (3) centrifuging the conditioned sludge, drying the solid phase obtained by centrifugation to obtain organic soil with water-retaining function; adjusting the pH of the liquid phase obtained by centrifugation to between 8 and 9 using lime water, then adding ferrous sulfate and hydrogen peroxide, and centrifuging after the reaction to obtain sediment and supernatant;

[0012] (4) drying the sediment and then calcining it to obtain ferrite; and returning the supernatant to the sewage treatment plant as a carbon source.

[0013] Furthermore, in step (1), the solid content of the concentrated sludge is 2%-3%, and the amount of ferrous sulfate added is 200-300 mg / L.

[0014] Furthermore, in step (1), the ozone concentration of the ozone oxidation treatment is 5-30 g / m 3 , the processing time is 20-40 minutes.

[0015] Furthermore, in step (2), the mass concentration of the sulfuric acid is 30%; the mass volume ratio of the black soldier fly pupa shell to the sulfuric acid is 30%-60%; and the soaking time is more than 60 minutes, more preferably 30-75 minutes.

[0016] Furthermore, in step (2), the amount of the pupa shell powder slurry added to the ozone-treated sludge is 0.5%-2% by volume; and the amount of the polydimethyldiallylammonium chloride added is 0.1%-0.3% by volume of the ozone-treated sludge.

[0017] Furthermore, in step (3), 200-300 mg / L of ferrous sulfate is added to the liquid phase after adjusting the pH value by weight volume ratio; 0.5%-1.0% of hydrogen peroxide is added to the liquid phase after adjusting the pH value by volume ratio. Preferably, the mass volume concentration of the hydrogen peroxide is 30%.

[0018] Furthermore, the calcination temperature in step (4) is 850°C; the COD of the supernatant in step (4) is 2000-5000 mg / L, and the carbon-nitrogen ratio is 12-20.

[0019] The present invention adopts ozone to oxidize the sludge cell contents, utilizes black soldier fly pupa shell slurry and polydimethyldiallyl ammonium chloride as conditioning materials and materials for improving the water retention performance of residues, so that the volatile organic matter in the sludge is degraded by more than 40%, and the heavy metals in the sludge are removed by more than 40%. The dehydrated products are prepared into soil water retention materials, the heavy metals separated from the sludge are recovered in the form of ferrites, and the organic carbon in the liquid phase is utilized as a carbon source for the sewage treatment plant, thereby realizing the full resource utilization of the sludge.

[0020] The technical principles of the present invention are as follows:

[0021] (1) The present invention adds ferrous sulfate to the sludge and then performs ozone treatment, which is an iron-catalyzed ozone oxidation treatment. On the one hand, ozone completely destroys the bacterial cell membrane in the sludge, prompting the release of polysaccharides and proteins in the bacteria into the liquid phase; on the other hand, ozone degrades organic matter in the sludge, including extracellular polymers, and promotes the oxidation and dissolution of reduced heavy metals combined with the sludge into the liquid phase. The sludge cells are mainly left with skeletons such as cell walls, so that the organic matter removal rate after sludge dehydration reaches 40%-53%.

[0022] (2) Heavy metals in sludge mainly exist in the form of sulfides. After ozone oxidation treatment, the removal rate of heavy metals in sludge particles is 40%-80%, and heavy metals are dissolved into the liquid phase in large quantities in the form of ions.

[0023] (3) The shell of black soldier flies is similar to chitin, and its acid leaching product has a coagulation function, while polydimethyldiallyl ammonium chloride can play a flocculation and bridging role in sludge. After conditioning by the two, the particles mainly composed of the sludge cell wall skeleton form sediment after centrifugation. In addition, after the pupa shell powder is treated with sulfuric acid, a large number of hydrophilic groups such as hydroxyl (-OH) and amino (-NH2) are formed, which not only have a conditioning effect on the sludge, but also enter the sludge sediment to improve the water retention effect of the sediment product.

[0024] (4) The sludge cell wall skeleton is used as sediment. During the separation process, pupa shell powder and polydimethyldiallyl ammonium chloride, which have strong hydrophilicity and water retention, are mixed in as conditioners, which also improves the water retention of the dehydrated sediment.

[0025] (5) After the heavy metals in the sludge are dissolved in the liquid phase in the form of ions, the pH of the liquid phase is adjusted to 8-9, and after treatment with ferrous sulfate and hydrogen peroxide, the heavy metals and iron salts are co-precipitated to form ferrite sludge. After calcination, the ferrite sludge forms a ferrite product. The carbon-nitrogen ratio in the liquid phase is 12-20, which is much higher than the carbon-nitrogen ratio of the sewage treatment plant inlet water of about 4. Therefore, it can play a role in supplementing the carbon source for the denitrification and phosphorus removal of the sewage treatment plant, reducing the cost of purchasing carbon sources for the sewage treatment plant.

[0026] The more specific processing steps of the present invention are as follows:

[0027] (1) Place concentrated sludge with a solid content of 2%-3% from a sewage treatment plant into an ozone oxidation treatment tank, and add 200-300 mg / L of ferrous sulfate according to the weight / sludge volume ratio.

[0028] (2) Start the ozone generator to oxidize the sludge with ozone. The specific parameters are: ozone concentration of 5-30g / m 3, the inflation rate is 0.1-0.5m 3 / h, the treatment time is 20-40 minutes (the treatment time is based on the removal rate of volatile organic matter exceeding 40% after sludge centrifugal treatment).

[0029] (3) The shells discarded after the extraction of black soldier fly pupae are ground with a crusher to a particle size of 1.0-10 μm, which is pupa shell powder. Pupa shell powder and sulfuric acid (concentration of 30%) are mixed in a mass volume ratio of 30%-60% and processed for 30-75 minutes to form a pupa shell powder slurry.

[0030] (4) After ozone treatment, add pupa shell powder slurry to the sludge at a ratio of 0.5%-2% (V / V) by volume weight ratio. After mixing evenly, add polydimethyldiallylammonium chloride at a ratio of 0.1%-0.3% (W / V). At this time, the pH of the sludge is 6.1-6.8. This is the sludge after conditioning treatment.

[0031] (5) The conditioned sludge is centrifuged and then separated into solid and liquid parts to form a solid phase and a liquid phase; the solid phase is dried and can be used as organic fertile soil with water retention function.

[0032] (6) Lime water was added to the liquid phase to adjust its pH to 8-9, and 200-300 mg / L of ferrous sulfate was added by weight volume ratio (W / V) and 0.5%-1.0% (V / V) of 30% (W / V) hydrogen peroxide was added by volume ratio. After reacting for 1 hour, centrifugation was performed to form two parts: sediment and supernatant. After the sediment is dried and calcined at 850°C, ferrite (main components are Fe3O4 and FeCr2O4, with iron mass fraction of 35.68-38.42%, oxygen mass fraction of 42.96-45.32%, and chromium mass fraction of 8.68-11.75%) is formed and put on the market for sale; the COD of the supernatant can be as high as 2000-5000 mg / L and the carbon-nitrogen ratio is 12-20, so it can be used as high-carbon wastewater returned to the sewage treatment plant as a carbon source for denitrification and phosphorus removal in the biochemical pool, solving the problem of insufficient carbon source for denitrification and phosphorus removal in the sewage treatment plant.

[0033] The present invention discloses the following technical effects:

[0034] The present invention can efficiently remove organic matter and heavy metals in sludge from urban sewage treatment plants, and improve the water retention performance of solid phase sediments by adding a conditioning agent, thereby facilitating the land utilization thereof; the heavy metals in the liquid phase product can be prepared into ferrite products in the form of iron salt co-precipitation and sold on the market, thereby reducing the sludge treatment cost; the liquid phase containing high organic matter and high carbon-nitrogen ratio can replace the carbon source used for nitrogen and phosphorus removal in the sewage treatment plant, thereby reducing the purchase of carbon sources for the sewage treatment plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0039] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0040] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0041] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0042] Example 1

[0043] Full resource treatment of sludge from urban sewage treatment plants:

[0044] (1) Take the concentrated sludge with a solid content of 2% from the municipal sewage treatment plant, place it in an ozone oxidation treatment tank, add 300 mg / L (W / V) ferrous sulfate, and then 3 The filling rate is 30g / m 3 After 35 minutes of ozone treatment, the removal rate of volatile organic matter and heavy metals in the sludge after centrifugal treatment was 50% and 55%, respectively.

[0045] (2) The black soldier fly pupa shells were ground by a crusher to a particle size of 8 μm, and then the pupa shell powder was added to 30% sulfuric acid at a mass volume ratio of 30%, and soaked for 75 minutes before use.

[0046] (3) Add 1% (V / V) pupa shell powder slurry to the sludge treated with ozone in step (1), mix well, and then add 0.2% (W / V) polydimethyldiallyl ammonium chloride to condition the sludge. At this time, the pH of the sludge is 6.6.

[0047] (4) The sludge conditioned in step (3) is then subjected to solid-liquid separation, and the solid phase is dried to prepare soil water-retaining materials; the liquid phase is firstly adjusted to pH 8.0 by adding lime water, and then 200 mg / L (W / V) of ferrous sulfate and 0.5% (V / V) of 30% hydrogen peroxide are added. After reacting for 1 hour, the sediment and the supernatant are separated by centrifugation, and the sediment is dried and calcined at 850° C. to prepare ferrite, and the COD of the supernatant is 3500 mg / L and the carbon-nitrogen ratio is 18, which is returned to the sewage treatment plant.

[0048] The soil water-retaining material prepared in Example 1 of the present invention has a high water absorption rate and a high salt water absorption rate. The natural water absorption capacity reaches 620g / g in 10 minutes, and the salt water absorption rate is 32g / g; the water release rate is low, the water retention capacity is strong, the 12h water retention rate is 95.5%, the 24h water retention rate is 81%, the 48h water retention rate is 50%, the 72h water retention rate is 16%, and the 96h water retention rate is 3.2%; the heavy metal content is lower than the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB 15618-2018). The main components of the prepared ferrite are Fe3O4 and FeCr2O4, the iron mass fraction is 35.68%, the oxygen mass fraction is 45.32%, and the chromium mass fraction is 11.75%.

[0049] Example 2

[0050] Full resource treatment of sludge from urban sewage treatment plants:

[0051] (1) Take the concentrated sludge with a solid content of 3% from the urban sewage treatment plant, place it in an ozone oxidation treatment tank, add 280 mg / L (W / V) ferrous sulfate, and then press 0.4 m 3 The filling rate is 20 g / m 3 The ozone treatment has a volatile organic compound removal rate of 45% and a heavy metal removal rate of 80% after 40 minutes of treatment.

[0052] (2) Grind the black soldier fly pupa shell into a powder of 1 micron using a crusher, then add the pupa shell powder to 30% sulfuric acid at a mass volume ratio of 40%, soak for 65 minutes and set aside.

[0053] (3) The prepared pupa shell powder slurry is added to the sludge treated with ozone in step (1) at a ratio of 0.5% (V / V), mixed evenly, and then 0.1% (W / V) of polydimethyldiallyl ammonium chloride is added for conditioning, and the pH of the sludge is 6.1.

[0054] (4) The sludge conditioned in step (3) is centrifuged to separate into a solid phase and a liquid phase, and the solid phase is dried to prepare a soil water-retaining material; lime water is added to the liquid phase to adjust the pH to 8.6, followed by adding 250 mg / L (W / V) of ferrous sulfate and 0.8% (V / V) of 30% hydrogen peroxide. After reacting for 1 hour, the sludge is centrifuged to separate into a sediment and a supernatant. The sediment is dried and calcined at 850° C. to prepare ferrite, and the supernatant with a COD of 5000 mg / L and a carbon-nitrogen ratio of 20 is returned to the sewage treatment plant.

[0055] The soil water-retaining material prepared in Example 2 of the present invention has a high water absorption rate and a high salt water absorption rate. The natural water absorption capacity reaches 640g / g in 10 minutes, and the salt water absorption rate is 35g / g; the water release rate is low, the water retention capacity is strong, the 12h water retention rate is 96.5%, the 24h water retention rate is 80%, the 48h water retention rate is 48%, the 72h water retention rate is 15%, and the 96h water retention rate is 3.5%; the heavy metal content is lower than the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB 15618-2018). The main components of the prepared ferrite are Fe3O4 and FeCr2O4, the iron mass fraction is 37.21%, the oxygen mass fraction is 43.65%, and the chromium mass fraction is 9.83%.

[0056] Example 3

[0057] (1) Take the concentrated sludge with a solid content of 2% from the urban sewage treatment plant, place it in an ozone oxidation treatment tank, add 200 mg / L of ferrous sulfate, and then 3 The filling rate is 5g / m 3After 20 minutes of ozone treatment, the removal rate of volatile organic compounds reached 53% and the removal rate of heavy metals reached 40%.

[0058] (2) The black soldier fly pupa shell is ground into 10 micron pupa shell powder by a crusher, and then the pupa shell powder is added into 30% sulfuric acid at a mass volume ratio of 60%, and the mixture is soaked for 30 minutes to obtain a pupa shell powder slurry.

[0059] (3) The prepared pupa shell powder slurry is added to the sludge after ozone treatment in step (1) at a ratio of 2% (V / V), and then mixed evenly, and then 0.3% (W / V) of polydimethyldiallyl ammonium chloride is added to condition the sludge, at which time the pH value is 6.8.

[0060] (4) The sludge conditioned in step (3) is subjected to solid-liquid separation, and the separated solid phase is dried to prepare soil water-retaining materials; lime water is added to the liquid phase to adjust the pH to 9.0, and then 300 mg / L of ferrous sulfate and 1.0% (V / V) 30% hydrogen peroxide are added. After reacting for 1 hour, the sediment and the supernatant are separated. The sediment is dried and calcined at 850°C to prepare ferrite; the COD of the supernatant is 2000 mg / L and the carbon-nitrogen ratio is 12, and it is returned to the sewage treatment plant as a carbon source.

[0061] The soil water-retaining material prepared in Example 3 of the present invention has a high water absorption rate and a high salt water absorption rate. The natural water absorption for 10 minutes reaches 600g / g, and the salt water absorption rate is 33g / g; the water release rate is low, the water retention capacity is strong, the 12h water retention rate is 94.5%, the 24h water retention rate is 83%, the 48h water retention rate is 52%, the 72h water retention rate is 16%, and the 96h water retention rate is 4.2%; the heavy metal content is lower than the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB 15618-2018). The main components of the prepared ferrite are Fe3O4 and FeCr2O4, the iron mass fraction is 36.94%, the oxygen mass fraction is 44.86%, and the chromium mass fraction is 10.32%.

[0062] Example 4

[0063] (1) Take the concentrated sludge with a solid content of 3% from the municipal sewage treatment plant, place it in an ozone oxidation treatment tank, add 240 mg / L of ferrous sulfate, start the ozone generator, and press 0.2 m 3 / h filling rate filled with 10g / m 3 After 20 minutes of ozone treatment, the removal rate of volatile organic compounds was 40% and the removal rate of heavy metals was 75%.

[0064] (2) The black soldier fly pupa shells were ground into 15 μm pupa shell powder using a crusher, and the pupa shell powder was added into 30% sulfuric acid at a mass volume ratio of 50%, and soaked for 70 minutes to prepare a pupa shell powder slurry.

[0065] (3) Add 1.5% (V / V) pupa shell powder slurry to the ozone-treated sludge, mix well and then add 0.1% (W / V) polydimethyldiallyl ammonium chloride. After conditioning, the pH of the sludge is 6.5.

[0066] (4) The sludge conditioned in step (3) is subjected to solid-liquid separation, and the solid phase is dried to prepare soil water-retaining material; the liquid phase is firstly adjusted to pH 8.4 by adding lime water, and then 280 mg / L (W / V) of ferrous sulfate and 0.8% (V / V) of 30% hydrogen peroxide are added, and centrifugation is performed after reacting for 1 hour. The sediment after centrifugation is dried and calcined at 850°C to prepare ferrite. The supernatant has a COD of 3000 mg / L and a carbon-nitrogen ratio of 15, and is returned to the sewage treatment plant as a carbon source.

[0067] The soil water-retaining material prepared in Example 4 of the present invention has a high water absorption rate and a high salt water absorption rate. The natural water absorption capacity reaches 590g / g in 10 minutes, and the salt water absorption rate is 38g / g; the water release rate is low, and the water retention capacity is strong. The water retention rate is 94.8% for 12 hours, 82% for 24 hours, 51% for 48 hours, 17% for 72 hours, and 3.8% for 96 hours; the heavy metal content is lower than the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB 15618-2018). The main components of the prepared ferrite are Fe3O4 and FeCr2O4, with an iron mass fraction of 38.42%, an oxygen mass fraction of 42.96%, and a chromium mass fraction of 8.68%.

[0068] The present invention adds 200-300 mg / L of ferrous sulfate and 5-30 g / L of ferrous sulfate to the concentrated sludge. 3 After ozone oxidation treatment, the prepared pupa shell powder slurry with coagulation function and polydimethyldiallyl ammonium chloride are added and centrifuged. The solid phase is dried to prepare a water-retaining material, and the liquid phase is added with lime water to adjust the pH to 8-9, and ferrous sulfate and hydrogen peroxide are added for reaction and separated again. The separated sediment is dried and calcined to prepare ferrite, and the supernatant is returned to the sewage treatment plant as a carbon source with high COD. The present invention can realize the resource utilization of sludge, and has the advantages of simple method, low treatment cost, and high resource utilization rate.

[0069] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for fully utilizing sludge from a municipal sewage treatment plant, characterized in that: The following steps are involved: (1) adding ferrous sulfate to concentrated sludge from a municipal sewage treatment plant and performing ozone oxidation treatment to obtain ozone-treated sludge; (2) adding pupa shell powder slurry and polydimethyldiallyl ammonium chloride to the sludge after ozone treatment so that the pH of the sludge is 6.1-6.8 to obtain conditioned sludge; The method for preparing the pupa shell powder slurry comprises the following steps: grinding the black soldier fly pupa shell, adding sulfuric acid and soaking it to obtain the pupa shell powder slurry; (3) centrifuging the conditioned sludge, drying the solid phase obtained by centrifugation to obtain organic soil with water-retaining function; adjusting the pH of the liquid phase obtained by centrifugation to between 8 and 9 using lime water, then adding ferrous sulfate and hydrogen peroxide, and centrifuging after the reaction to obtain sediment and supernatant; (4) drying the sediment and then calcining it to obtain ferrite; the supernatant is returned to the sewage treatment plant as a carbon source; In step (1), the solid content of the concentrated sludge is 2%-3%, and the amount of ferrous sulfate added is 200-300 mg / L; In step (1), the ozone concentration of the ozone oxidation treatment is 5-30 g / m 3 , the processing time is 20-40 minutes; In step (2), the mass concentration of the sulfuric acid is 30%; the mass volume ratio of the black soldier fly pupa shell to the sulfuric acid is 30%-60%; and the soaking time is 30-75 minutes; In step (2), the amount of the pupa shell powder slurry added to the ozone-treated sludge is 0.5%-2% by volume; the amount of the polydimethyldiallylammonium chloride added is 0.1%-0.3% by volume of the ozone-treated sludge; In step (3), 200-300 mg / L of ferrous sulfate is added to the liquid phase after the pH value is adjusted by weight to volume ratio; 0.5%-1.0% of hydrogen peroxide is added to the liquid phase after the pH value is adjusted by volume ratio; The calcination temperature in step (4) is 850°C.

2. The processing method according to claim 1, characterized in that: The mass volume concentration of the hydrogen peroxide is 30%.

3. The processing method according to claim 1, characterized in that: The COD of the supernatant in step (4) is 2000-5000 mg / L, and the carbon-nitrogen ratio is 12-20.

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