A method for sludge dewatering and volume reduction using filamentous fungal Fenton conditioning and its application

Abstract

This application discloses a method for sludge dewatering and volume reduction using filamentous fungi in a Fenton-like conditioning process, and its application, belonging to the field of sludge treatment technology. By inoculating filamentous fungi, especially *Penicillium jatropha* NAU-12, into the sludge, a Fenton-like reaction is triggered by the fungi's dual characteristics: inducing the transformation of endogenous inert iron-containing compounds in the sludge into amorphous active nano-iron particles and producing H2O2 through hyphal differentiation. This generates free radicals ·OH and Fe(III) beneficial for sludge dewatering, thus achieving deep dewatering (from 95% moisture content to 60%) under conditions of zero external Fenton chemical addition and no pre-acidification of the sludge. Furthermore, the resulting dewatered sludge cake exhibits minimal organic matter loss, and the dewatered filtrate has a near-neutral pH. This significantly improves the technical and economic efficiency of sludge treatment, making it a green and environmentally friendly approach.

Description

Technical Field

[0001] This application belongs to the field of sludge treatment technology, specifically relating to a method for sludge dewatering and volume reduction through filamentous fungal Fenton conditioning. Background Technology

[0002] Wastewater treatment plant sludge has a high moisture content (generally >95%), resulting in a large volume and posing significant challenges to its transportation, disposal, and resource utilization. Achieving deep dewatering and volume reduction of sludge is crucial for solving the sludge disposal problem and ensuring the sustainable development of the wastewater treatment industry.

[0003] The main methods for sludge dewatering include: mechanical dewatering, which uses mechanical pressure or centrifugal force, such as plate and frame filter presses, belt filter presses, and centrifugal dewatering machines, to dewater sludge, reducing the sludge moisture content from over 90% to about 70%–85%; natural drying, which places the sludge in a drying field and removes moisture through natural evaporation, infiltration, and draining, reducing the sludge moisture content to 60%–75%, but this takes a long time and requires a large area; and chemical dewatering, which adds flocculants, coagulants, and other chemical agents to the sludge to improve its dewatering performance. Combined with mechanical dewatering, this can further reduce the sludge moisture content from about 80% with simple mechanical dewatering to 60%–70%. Fenton advanced oxidation technology, based on Fe(II) catalysis to generate highly oxidizing free radicals (·OH, etc.) from H2O2 and Fe(III) flocculation, can significantly reduce the moisture content of sludge from 95% to about 60%, resulting in a remarkable reduction in volume. It is considered a sludge dewatering method with great engineering application potential. For example, the applicant's previous application, publication number CN114920436A, entitled "A Method for Bioleaching Treatment of Chemically Enhanced Anaerobic Digestion Sludge," is relevant.

[0004] In practical applications, the main drawbacks limiting the widespread adoption of this method are the large dosage of Fenton's reagent and the high treatment cost. Typically, to achieve a sludge moisture content of <60%, acid (such as H2SO4) must first be added to acidify the sludge pH from 7.0 to around 4.0. Then, 50–80 kg / t of Fe(II) and 60–100 kg / t of H2O2 (based on sludge dry matter) are added to initiate the Fenton chain radical reaction. Furthermore, H2O2 is a hazardous chemical, and its purchase, transportation, and storage present numerous inconveniences.

[0005] Therefore, there is an urgent need to develop a green and efficient new method that can achieve deep dewatering and volume reduction of sludge. Summary of the Invention

[0006] 1. The problem to be solved

[0007] This application addresses the problems of high dosage and cost of exogenous Fe(II) / H2O2 reagents in existing sludge Fenton oxidation dewatering technologies. It provides a method for sludge dewatering and reduction through filamentous fungal Fenton-like conditioning and its application. This method utilizes filamentous fungi, especially Penicillium simplicissimum NAU-12, to condition the sludge. Through the differentiation of its hyphae to produce H2O2 and the biological induction of inert iron-containing substances endogenous in the sludge into amorphous active nano-iron particles, a Fenton-like reaction is initiated (generating free radicals ·OH and Fe(III)). This achieves rapid release and dewatering of sludge moisture under conditions of zero addition of exogenous Fenton chemical agents (inorganic acids, organic acids, and Fe(II) / H2O2 reagents).

[0008] 2. Technical Solution

[0009] To solve the above problems, the technical solution adopted in this application is as follows:

[0010] This application provides a method for sludge dewatering and volume reduction through filamentous fungal Fenton conditioning, the method comprising:

[0011] S1, filamentous fungi are inoculated into sludge and nutrients are added; the filamentous fungi have the function of differentiating to produce H2O2 and inducing inert iron-containing compounds to transform into amorphous active nano-iron particles;

[0012] S2, the sludge is placed under stirring, mixing and aeration conditions to carry out a Fenton-like reaction. Under stirring, mixing and aeration conditions, on the one hand, the hyphae of filamentous fungi differentiate to produce H2O2, and on the other hand, the endogenous inert iron-containing substances in the sludge are induced to transform into amorphous active nano iron particles. A Fenton-like reaction occurs between the two, and free radicals ·OH and Fe(III) are generated in the system, thereby triggering the release of water held in the sludge.

[0013] S3, mechanical dewatering of the treated sludge to obtain dewatered sludge cake and filter press liquid, thereby achieving sludge dewatering and volume reduction.

[0014] Furthermore, the aforementioned filamentous fungi include Penicillium spp.

[0015] Furthermore, the aforementioned *Penicillium simplecissimum* is *Penicillium simplecissimum* NAU-12, classified as *Penicillium simplecissimum*, and deposited at the China General Microbiological Culture Collection Center (CGMCC) on July 6, 2015, with accession number CGMCC NO.10990. This microorganism was previously screened and deposited by the inventors, as detailed in Chinese Invention Patent Publication No. CN106190871A. During the research process, the applicant discovered that this microorganism has the function of differentiating to produce H2O2 and inducing inert iron-containing compounds to transform into amorphous active nano-iron particles.

[0016] Furthermore, the inoculation density of the aforementioned Penicillium tumefaciens NAU-12 was 1×10⁻⁶. 8 ~1×10 9 Spores / mL.

[0017] Furthermore, the aforementioned nutrients include phosphorus, calcium, sugar, and acid.

[0018] Furthermore, the aforementioned nutrients include K2HPO4, CaCl2·2H2O, oxalic acid, and sucrose.

[0019] Furthermore, the concentrations of the above-mentioned nutrients after addition are as follows:

[0020] K2HPO4 0.01~0.04g / L,

[0021] CaCl2·2H2O 0.01~0.036g / L,

[0022] Oxalic acid 0.01~0.02g / L,

[0023] Sucrose 0.001~0.01g / L.

[0024] Furthermore, the concentrations of the above-mentioned nutrients after addition are as follows:

[0025] K2HPO4 0.01g / L,

[0026] CaCl2·2H2O 0.036g / L

[0027] Oxalic acid 0.01 g / L

[0028] Sucrose 0.001 g / L.

[0029] Furthermore, the solids concentration of the above-mentioned sludge is 1-5%.

[0030] Furthermore, the above-mentioned mixing, aeration, and oxygenation conditions include: 20–35°C, ventilation and mixing for 2–4 days, and controlling the dissolved oxygen content to 1–2 mg / L.

[0031] Furthermore, the above-mentioned mixing, aeration, and oxygenation conditions include: 25°C and ventilated mixing for 3 days.

[0032] Furthermore, the aforementioned mechanical dehydration includes dehydration using mechanical pressure or centrifugal force.

[0033] Furthermore, the aforementioned mechanical dewatering includes using equipment such as plate and frame filter presses, belt filter presses, and centrifugal dewatering machines to dewater sludge.

[0034] This application also provides the application of the above-mentioned method of using filamentous fungi-based Fenton conditioning to achieve sludge dewatering and volume reduction in sludge dewatering and volume reduction.

[0035] A process for sludge dewatering and volume reduction, comprising the above-mentioned method of achieving sludge dewatering and volume reduction through filamentous fungal Fenton conditioning.

[0036] 3. Beneficial effects

[0037] Compared with the prior art, the advantages of this application are as follows:

[0038] (1) This application provides a method for sludge dewatering and reduction using filamentous fungal Fenton-like conditioning and its application. By inoculating filamentous fungi, especially Penicillium simplicissimum NAU-12, into the sludge, Penicillium simplicissimum NAU-12 can induce the conversion of endogenous inert iron-containing compounds in the sludge into amorphous active nano-iron particles. At the same time, the mycelial differentiation of Penicillium simplicissimum NAU-12 produces H2O2. This dual characteristic triggers a Fenton-like oxidation reaction, generating free radicals ·OH and Fe(III) that are beneficial to sludge dewatering, thereby significantly reducing the treatment cost of sludge dewatering. Compared with existing sludge dewatering technologies that rely on large amounts of exogenous Fe(II) / H2O2 chemical reagents and chemical acids, this method achieves deep sludge dewatering under conditions of zero addition of exogenous Fenton chemical agents, significantly improving economic efficiency.

[0039] (2) This application provides a method for sludge dewatering and reduction by using filamentous fungi such as Fenton conditioning. Penicillium spp. is widely present in sludge and is an indigenous microorganism with strong environmental adaptability. The nutrients required for its growth include K2HPO4, CaCl2·2H2O, oxalic acid and sucrose, which are inexpensive and readily available.

[0040] (3) The present application provides a method for sludge dewatering and reduction by using filamentous fungi-based Fenton conditioning and its application. The entire treatment process is simple, easy to operate, green, efficient, economical and practical. Attached Figure Description

[0041] Figure 1 This is the result of laser particle size analyzer detecting changes in the particle size of Fe compounds.

[0042] Figure 2 This is the result of X-ray diffraction analysis of the phase changes in Fe compounds.

[0043] Figure 3 It is an in situ staining method for detecting H2O2 and O2. ·- The result of the generation.

[0044] Figure 4 These are the appearances of sludge before (left) and after (right) Fenton treatment. Detailed Implementation

[0045] The present application will be further described below with reference to specific embodiments.

[0046] It should be noted that terms such as "upper", "lower", "left", "right", and "middle" used in this specification are only for clarity of description and are not intended to limit the scope of implementation. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of this application.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0048] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0049] As used herein, the term “about” is used to provide for the flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable.

[0050] As used herein, the term “at least one of…” is intended to be synonymous with “one or more of…”. For example, “at least one of A, B, and C” explicitly includes only A, only B, only C, and combinations thereof.

[0051] Concentration, amount, and other numerical data may be presented in range format herein. It should be understood that such range format is used solely for convenience and brevity and should be flexibly interpreted to include not only the values ​​explicitly stated as the limits of the range, but also all individual values ​​or subranges encompassed within the range, as if each value and subrange were explicitly stated. For example, a range of values ​​from about 1 to about 4.5 should be interpreted to include not only the explicitly stated limits of 1 to 4.5, but also individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that describe only a single value, such as “less than about 4.5,” which should be interpreted to include all the aforementioned values ​​and ranges. Furthermore, this interpretation should apply regardless of the breadth of the range or characteristic described.

[0052] As used in this article, "inert iron compounds" refer to iron compounds that are relatively inert chemically and do not readily participate in chemical reactions under certain conditions. Examples include hematite, whose main component is ferric oxide (Fe₂O₃); magnetite, whose main component is iron(III) oxide (Fe₃O₄); and jaundice (KFe₃(SO₄)₂(OH)₆), a potassium and iron sulfate mineral. Sludge typically contains inert iron compounds, including those introduced from industrial wastewater. Many industrial processes, such as electroplating, steel processing, and electronics manufacturing, generate wastewater containing large amounts of iron ions. During wastewater treatment, these iron ions combine with hydroxide ions, sulfides, etc., to form various iron compounds. Some of these iron compounds are converted into inert iron compounds, such as hematite and magnetite, during subsequent sludge formation and treatment. Domestic sewage also contains iron, primarily from waste generated by human activities and additives in detergents. During the biochemical reaction stage of wastewater treatment, some iron elements participate in the metabolic process of microorganisms. Microorganisms convert some iron elements into iron-containing substances within their cells. During sludge sedimentation and compaction, these iron-containing substances may be further converted into inert iron compounds. In addition, the sludge may be mixed with the natural environment. During the operation of wastewater treatment plants, sludge will come into contact with the surrounding natural environment. Soil particles, dust, etc. may be mixed into the sludge. Soil itself contains various inert iron compounds, such as hematite and jaundice, which will also lead to a certain amount of inert iron compounds in the sludge.

[0053] As used in this article, "solid concentration" is an important indicator for measuring the content of solid matter in sludge. When sludge solid concentration is expressed as a percentage (%), it refers to the proportion of the mass of solid matter in sludge to the total mass of sludge.

[0054] As used in this article, "CST" stands for Capillary Suction Time, which refers to the time required for water in sludge to permeate from the sludge onto filter paper under capillary action and diffuse a certain distance on the filter paper. The unit is seconds (s). It reflects the ease with which water in sludge passes through porous media such as filter paper. The higher the CST value, the more difficult it is to dewater the sludge.

[0055] As used in this article, "SRF" stands for Specific Resistance to Filtration, which refers to the resistance per unit mass of dry sludge per unit filtration area, expressed in m / kg. It indicates the resistance of sludge to the filter medium (such as filter cloth) during the sludge filtration and dewatering process. The higher the SRF value, the more difficult the sludge filtration and dewatering.

[0056] Example 1

[0057] This embodiment provides a method for sludge dewatering and volume reduction through filamentous fungal Fenton conditioning.

[0058] In this embodiment, the sludge was collected from a domestic wastewater treatment plant in Nanjing Jiangbei New Area, and its basic properties are shown in Table 1.

[0059] Table 1 Basic Physicochemical Properties of Sludge

[0060]

[0061] In this embodiment, the filamentous fungus is Penicillium simplecissimum NAU-12, which is deposited at the China General Microbiological Culture Collection Center on July 6, 2015, with accession number CGMCC NO.10990. This microorganism was previously screened and deposited by the inventors, as detailed in Chinese Invention Patent Publication No. CN106190871A.

[0062] In this embodiment, a method for achieving sludge dewatering and volume reduction through filamentous fungal Fenton conditioning includes:

[0063] S1. Prepare a suspension of Penicillium simplicissimum NAU-12 spores, and inoculate the Penicillium simplicissimum into sludge to achieve a bacterial density of 3 × 10⁻⁶. 8 Spores / mL; and added nutrients (g / L): K2HPO4 0.01, CaCl2·2H2O 0.036, oxalic acid 0.01, sucrose 0.001;

[0064] S2, the sludge was placed in a stirred aeration environment at 25℃, with dissolved oxygen content controlled at 1-2 mg / L, and conditioned for 3 days in a Fenton-like manner. At the beginning of conditioning (0 h) and after conditioning (72 h), changes in the particle size and mineral phase of Fe compounds were detected using a laser particle size analyzer and X-ray diffraction. In-situ staining was used to detect H2O2 and O2. ·- The generation of Fe compounds; the changes in particle size and mineral phases detected by laser particle size analyzer and X-ray diffraction, such as Figure 1 and Figure 2 As shown, a new amorphous Fe compound was generated in the system, and the particle size of the Fe compound became finer and more uniform (average particle size 350 nm). The total soluble Fe content in the system was 36 mg / L. The in-situ staining results are as follows: Figure 3 As shown, a large amount of H2O2 and O2 were generated in this system. ·- A strong peak signal of ·OH free radicals was detected; before Fenton conditioning ( Figure 4 (middle left image), back ( Figure 4 The sludge in the middle right image is like Figure 4 As shown, the sludge CST value decreased to 39s and the SRF decreased to 1.3×10⁻⁶. 11 m / kg;

[0065] S3 involves plate and frame filter press dewatering of the treated sludge to obtain a cracked dewatered sludge cake (58% moisture content) and a clear dewatered filtrate, thus achieving sludge dewatering and volume reduction.

[0066] Comparative Example 1

[0067] This comparative example uses a traditional chemical method of adding Fenton's reagent (Fe(II) / H2O2) for sludge dewatering.

[0068] The sample is the same as the sample in Example 1. The processing steps for this comparative example are as follows:

[0069] (1) Pre-acidification of sludge: Add H2SO4 at a dosage of 50 kg H2SO4 / ton to acidify the sludge pH from 7.2 to 3.7;

[0070] (2) Fenton chemical oxidation treatment of sludge: FeSO4 and H2O2 were added at doses of 50 kg / t and 80 kg / t respectively, and the mixture was stirred at 25°C and subjected to Fenton chemical conditioning for 2 hours. The total dissolved Fe content in the treatment system was found to be 88 mg / L, with a significant free radical ·OH peak signal. The sludge CST value decreased to 37 s, and the SRF decreased to 2.2 × 10⁻⁶. 11 m / kg;

[0071] (3) Mechanical dewatering: The treated sludge is dewatered by plate and frame filter press to obtain dewatered sludge cake (moisture content 56%) and dewatered filtrate.

[0072] The dewatering effects of Example 1 and Comparative Example 1 are shown in Table 2. Under the condition of zero external addition of Fenton chemical reagent, the same dewatering effect is achieved. Furthermore, the pH values ​​of the dewatered sludge cake and dewatered filtrate are close to neutral, which is safer. The loss of organic matter in the sludge is also less, which is easier for subsequent resource utilization.

[0073] Table 2 Comparison of sludge dewatering effects in Example 1 and Comparative Example 1

[0074]

[0075] Comparative Example 2

[0076] This comparative example uses a control group that only chemically adds H2O2 but does not inoculate with Penicillium simplicissimum NAU-12 for sludge dewatering.

[0077] The sample was the same as in Example 1, and the processing steps for this comparative example are as follows:

[0078] (1) Pre-acidification of sludge: Add H2SO4 at a dosage of 50 kg H2SO4 / ton to acidify the sludge pH from 7.2 to 3.7;

[0079] (2) Chemical treatment of sludge with H2O2: H2O2 reagent was added at a dosage of 80 kg / t, and the mixture was stirred at 25°C for 2 hours for chemical conditioning. Testing revealed that the total dissolved Fe content in the treatment system was only 1.2 mg / L, with no obvious free radical ·OH peak signal, indicating that the Fenton reaction did not occur significantly. The sludge CST value was 197 s, and the SRF was 2.8 × 10⁻⁶. 13 m / kg;

[0080] (3) Mechanical dewatering: The treated sludge was subjected to plate and frame filter press to obtain a dewatered sludge cake (82% moisture content) with a still high moisture content and a very turbid dewatered filtrate, indicating that the dewatering property of the treated sludge was still poor.

[0081] Comparative Example 3

[0082] This comparative example uses the method disclosed in CN114920436A, entitled "A Method for Bioleaching Treatment of Chemically Enhanced Anaerobic Digestion Sludge," to control sludge dewatering.

[0083] The sample was the same as in Example 1, and the processing steps for this comparative example are as follows:

[0084] (1) Penicillium simplicissimum NAU-12 bacterial culture;

[0085] (2) Bioleaching treatment: Penicillium tumefaciens NAU-12 bacterial solution (10%, v / v) was inoculated into the sludge and cultured in a constant temperature shaking incubator at 28℃ and 180r / min for 1 day. The water loss was replenished by weighing and water replenishment method to maintain the water content at about 97% to obtain bioleaching modified sludge. The pH of the sludge was measured to be 4.2.

[0086] (3) Chemically enhanced bioleaching conditioning: Add 60 mg / g sludge dry solids (DS) Fe to the above sludge. 2+ The sludge was incubated with 30 mg / g DS H2O2 in a constant temperature shaking incubator at 28℃ and 180 r / min for 1 h, and the pH of the sludge was determined to be 3.0.

[0087] (4) Mechanical dewatering: The treated sludge is subjected to plate and frame filter press with a feeding time of 30 min, high pressure water pressing and holding for 30 min, feeding pressure of 0.7 MPa, and diaphragm pressing pressure of 1.5 MPa to obtain a yellowish-brown dewatered sludge cake (moisture content of 58%) and clear dewatered filtrate.

[0088] As can be seen from the examples and comparative examples, the method and application of the filamentous fungal Fenton conditioning for sludge dewatering and volume reduction proposed in this application can reduce the sludge moisture content from 97% to 58%, achieving a dewatering rate of approximately 45%. This is essentially comparable to the existing Fenton reagent chemical oxidation method and the chemically enhanced sludge bioleaching method published in CN114920436A, both meeting the national standard requirement of a sludge cake moisture content of <60%. More importantly, the filamentous fungal Fenton treatment method of this application is achieved under conditions of zero external addition of Fenton chemical reagents. Furthermore, the final dewatered sludge cake and dewatered filtrate have near-neutral pH values, making it safer and resulting in less organic matter loss in the sludge, facilitating subsequent resource utilization.

Claims

1. A method for sludge dewatering and volume reduction using filamentous fungal Fenton conditioning, characterized in that, The method includes: S1, filamentous fungi are inoculated into sludge and nutrients are added; the filamentous fungi have the function of differentiating to produce H2O2 and inducing inert iron-containing compounds to transform into amorphous active nano-iron particles; S2, the sludge is placed under stirring, mixing and aeration conditions to carry out a Fenton-like reaction; S3, mechanically dewaters the treated sludge to achieve sludge dewatering and volume reduction; The filamentous fungi include Penicillium simulans; The *Penicillium* species mentioned is *Penicillium* NAU-12, classified and named as follows: Penicillium simplicissimum It is deposited at the China General Microbiological Culture Collection Center (CGMCC) on July 6, 2015, with accession number CGMCCNO.10990.

2. The method for sludge dewatering and volume reduction using filamentous fungal Fenton conditioning according to claim 1, characterized in that, The inoculation density of *Penicillium tumefaciens* NAU-12 was 1 × 10⁻⁶. 8 ~1×10 9 Spores / mL.

3. The method for sludge dewatering and volume reduction using filamentous fungal Fenton conditioning according to claim 1 or 2, characterized in that, The nutrients include phosphorus, calcium, sugar, and acid.

4. The method for sludge dewatering and volume reduction using filamentous fungal Fenton conditioning according to claim 3, characterized in that, The nutrients include K2HPO4, CaCl2·2H2O, oxalic acid, and sucrose.

5. The method for sludge dewatering and volume reduction using filamentous fungal Fenton conditioning according to claim 3, characterized in that, The concentrations of the added nutrients are as follows: K2HPO4 0.01~0.04 g / L; CaCl2·2H2O 0.01~0.036 g / L; oxalic acid 0.01~0.02 g / L; sucrose 0.001~0.01 g / L.

6. The method for sludge dewatering and volume reduction using filamentous fungal Fenton conditioning according to claim 4 or 5, characterized in that, The mixing, aeration and oxygenation conditions include: 20~35 ℃, aeration and mixing for 2~4 days, and controlling the dissolved oxygen content to 1~2 mg / L.

7. The application of the method for sludge dewatering and volume reduction using filamentous fungal Fenton conditioning as described in any one of claims 1-6 in sludge dewatering and volume reduction.

8. A sludge dewatering and weight reduction process, characterized in that, The process includes the method for sludge dewatering and volume reduction using filamentous fungal Fenton conditioning as described in any one of claims 1-6.

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