A method for improving sludge dewatering performance while promoting sludge disinfection

Abstract

This invention belongs to the field of sludge dewatering technology and provides a method for improving sludge dewatering performance while promoting sludge disinfection. The method includes the following steps: sequentially subjecting sludge to natural sedimentation and filtration to obtain pretreated sludge; the pretreated sludge and Fe... 2+ The compounds are mixed, and the pH of the mixture is adjusted to 4-6 using acid. The resulting acidic sludge is then reacted with dichlorohydantoin (DCDMH). This invention is the first to propose a method for simultaneously improving sludge dewatering performance and sludge disinfection, achieving both good dewatering and disinfection effects. CST reduction rate can reach over 30%, SRF reduction rate can reach over 60%, microbial inactivation rate can reach over 30%, and fecal coliform count can be <100 CFU / g DS. This invention utilizes DCDMH to dissolve and slowly release HClO and Fe. 2+ The dual effect of activated DCDMH in generating strong oxidizing free radicals to disinfect sludge can greatly improve the efficiency of disinfection and sterilization.

Description

Technical Field

[0001] This invention relates to the field of sludge dewatering technology, and in particular to a method for improving sludge dewatering performance while promoting sludge disinfection. Background Technology

[0002] The activated sludge process is a biological wastewater treatment technology that primarily utilizes the metabolism of microorganisms in activated sludge to absorb, decompose, and assimilate organic pollutants in wastewater into non-toxic and harmless substances. Waste activated sludge is an unavoidable byproduct of this biological wastewater treatment process. The massive amounts of sludge produced by urban wastewater treatment plants not only increase treatment costs but also pose significant environmental health risks due to the presence of toxic and harmful substances such as heavy metals, antibiotics, endocrine disruptors, and various pathogens. Therefore, the proper disposal of sludge has become an important and challenging task.

[0003] High moisture content is a major factor limiting the effective disposal of sludge. In common urban wastewater treatment systems, unconcentrated sludge has a moisture content as high as 95-99% (including 70% free water and 30% bound water). Due to its high content of hydrophilic organic matter such as proteins and polysaccharides, it exhibits strong fluidity and high hydrophilicity, resulting in poor dewatering performance. Therefore, it cannot be directly treated by any disposal method. Thus, sludge dewatering is necessary before formal disposal to change its morphology, improve its hydrophobicity, and reduce its moisture content, thereby achieving proper sludge disposal. Common methods such as ultrasonic treatment, freeze-thaw cycles, pyrolysis, flocculation, coagulation, and compound biological enzyme regulation have been proven to effectively improve sludge dewatering performance. However, these methods suffer from problems such as large reagent dosages, low efficiency, high energy consumption, stringent reaction conditions, and secondary pollution, thus limiting the widespread application of these technologies.

[0004] In recent years, various methods have emerged to improve sludge dewatering performance by modifying dewatering methods or combining multiple technologies. The core objective is to reduce sludge moisture content and volume through physical, chemical, or biological means, thereby lowering subsequent transportation and disposal costs and reducing environmental risks. For example, Chinese patent CN108423962B, "A Method for Improving Sludge Dewatering Performance," uses a biological method, employing biosurfactants and framework constructs to jointly condition the sludge. By reducing the surface tension of water, the adsorption energy of water molecules on the sludge surface is reduced, increasing the solubility of organic matter, thus improving sludge dewatering performance. Chinese patent CN111847820A, "A Sludge Dewatering Method Based on Hydrothermal Method," uses oxidants and activators under hydrothermal conditions to disrupt cell division, converting surface-adsorbed water in the sludge into interstitial water and free water, thereby improving sludge dewatering performance. Chinese patent CN 117843215A, "Application of Cation Exchange Resin and Method for Improving Sludge Dewatering Performance," uses physicochemically adsorbed cation exchange resin as a conditioner in sludge dewatering, effectively improving solid-liquid separation and sludge dewatering performance, while reducing the consumption of conditioner in sludge dewatering and avoiding residual agents in the subsequent sludge cake. However, traditional biochemical treatment is difficult to degrade and transform high-molecular-weight organic matter with poor biodegradability.

[0005] Currently, mainstream mechanical dewatering technologies (such as belt filter presses and centrifugal dewatering) typically require the use of chemical conditioning agents (such as polyacrylamide and iron salts), but these methods suffer from problems such as chemical residues, filtrate contamination, and biochemical pollution of the sludge cake. While thermal drying technology can achieve deep dewatering, its energy consumption and costs remain high. Advanced oxidation technologies, under certain conditions, generate highly reactive free radicals with strong oxidizing capabilities, enabling the harmless decomposition of trace organic matter and improving the biodegradability of substances. This has become a research hotspot in the field of environmental pollution control and protection. Advanced oxidation technologies can disrupt the stable floc structure of sludge and simultaneously destroy sludge cells, releasing bound water and internal water within the floc structure and cells, converting them into free water. This achieves a transformation of the water form in the sludge, ultimately improving sludge dewatering performance and achieving deep dewatering. Currently, advanced oxidation mainly revolves around the classic Fenton reaction, relying on Fe... 2+ It reacts with H2O2 under strongly acidic conditions, utilizing the generated hydroxyl radicals to break down cells, and then through the Fe produced in the reaction... 3+ The Fenton reagent promotes sludge flocculation, thus improving sludge dewatering performance. Furthermore, the reaction products are non-toxic and harmless, posing less environmental risk. However, using Fenton's reagent for sludge dewatering presents the following problems: ① Requires stringent strong acid conditions, which are difficult to achieve in engineering experiments or are prohibitively expensive. ② The H₂O₂ used in the reaction has poor stability, posing an explosion risk and presenting transportation difficulties. ③ The dosage during the reaction is difficult to control, and Fe... 2+ Easily oxidized to Fe3+ This leads to deactivation, limiting the large-scale application of the Fenton reaction in sludge dewatering. Therefore, current research often focuses on Fenton-like reactions or non-Fenton advanced oxidation reactions.

[0006] Existing technologies disclose patented technologies for improving sludge dewatering performance based on advanced oxidation. Chinese patent CN111635113A, "A Method for Conditioning Sludge Dewatering Using Calcium Peroxide," uses calcium peroxide as a conditioner for sludge pretreatment. The slow release of hydrogen peroxide generated during the calcium peroxide dissolution process forms stable hydroxyl radicals in the sludge system, disrupting cell boundaries. Simultaneously, the affinity of calcium ions for extracellular polymers in the sludge induces flocculation in the sludge flocs, simultaneously improving sludge dewatering performance. Chinese patent CN 119285201A, "A Method for Improving Sludge Dewatering Performance through Composite Pretreatment," uses high-valent metal salts such as ferric salts, low-valent transition metal salts, and oxidants such as hypochlorous acid and hypochlorite to jointly treat the sludge. It utilizes the extracellular oxidation of free radicals generated by advanced oxidation and the coagulation and agglomeration of transition metal salts to achieve moderate oxidation, thereby improving sludge dewatering performance. Chinese patent CN 114436499A, "A Method for Conditioning Residual Sludge with Aluminum Sludge and Advanced Oxidation," uses Fe... 2+ / SPC treatment of aluminum-rich sludge utilizes the reaction of ferrous sulfate and sodium percarbonate to generate hydroxyl radicals that destroy sludge flocs and cells, achieving water conversion and thus improving sludge dewatering performance. The aforementioned patent uses advanced oxidation technology to destroy extracellular polymers and break down cell walls, converting bound water into free water to improve water removal and thus enhance sludge dewatering performance. However, the aforementioned patent suffers from high costs and stringent reaction conditions. Furthermore, the use of traditional Fenton's advanced oxidation reaction presents challenges such as the difficulty and high cost of storing and transporting hydrogen peroxide, as well as significant risks. In addition, the control of pathogenic microorganisms after sludge dewatering is a crucial issue for the proper disposal of sludge. Existing technologies also disclose patents related to sludge disinfection. Chinese patent CN 107973505A, "A Sludge Treatment Additive and Its Preparation Method," proposes a method for preparing a compound additive including citric acid, sodium tripolyphosphate, and oxalic acid / acetic acid, achieving sludge disinfection, sterilization, and stabilization through the interaction of different additives. Chinese patent CN112624567A, entitled "A Method for Enhancing the Alkaline Disinfection of Medical Sludge," uses a compound of alkaline enhancers such as lime and sodium hydroxide to achieve disinfection and sterilization of medical sludge, demonstrating a good sterilization effect. This patent achieves highly efficient elimination of pathogenic microorganisms in sludge through the mixing and compounding of different chemical agents. However, while the aforementioned dewatering or disinfection methods can improve the dewatering or sterilization performance of sludge, they do not mention the ability to simultaneously achieve both disinfection and dewatering effects, thus limiting the effectiveness of these methods.

[0007] Therefore, it is of great significance to develop a method that can both improve the dewatering performance of sludge and simultaneously achieve the dual effects of eliminating and inactivating pathogens in sludge. Summary of the Invention

[0008] The purpose of this invention is to provide a method for improving sludge dewatering performance and promoting sludge disinfection, addressing the shortcomings of existing technologies.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] This invention provides a method for improving sludge dewatering performance and promoting sludge disinfection, comprising the following steps:

[0011] 1) The sludge is subjected to natural sedimentation and filtration in sequence to obtain pretreated sludge;

[0012] 2) Pretreatment of sludge and Fe 2+ The compounds are mixed, and the pH of the mixture is adjusted to 4-6 using acid to obtain acidic sludge;

[0013] 3) React acidic sludge with dichlorohydantoin to obtain the reacted sludge.

[0014] Preferably, the sludge in step 1) is municipal sludge with a moisture content ≥95%.

[0015] Preferably, the temperature of natural settling in step 1) is 22-28°C, and the natural settling time is 12-36 hours; the pore size of the sieve used for filtration is 1-2 mm.

[0016] Preferably, the acid in step 2) is hydrochloric acid or sulfuric acid, and the concentration of the acid is 1 to 3 mol / L.

[0017] Preferably, the Fe in step 2) 2+ The compound is ferrous sulfate heptahydrate or ferrous chloride; Fe 2+ The mass of the compound is calculated based on the total suspended solids in the sludge; 20–40 mg of Fe is added per 1 g of total suspended solids in the sludge. 2+ Compounds.

[0018] Preferably, the mixing temperature in step 2) is 20-30°C, the mixing time is 3-8 minutes, the mixing is carried out under stirring conditions, and the stirring speed is 150-200 rpm.

[0019] Preferably, in step 3), the mass of dichlorohydantoin is calculated based on the total suspended solids in the sludge, with 20-100 mg of dichlorohydantoin added per 1 g of total suspended solids in the sludge.

[0020] Preferably, the reaction temperature in step 3) is 26–30°C, the reaction time is 1.5–2.5 h, and the reaction is carried out under stirring conditions at a stirring speed of 150–200 rpm.

[0021] Preferably, when the sludge concentration C∈(20,25), Fe is expressed as g / L(TSS). 2+ The formula for calculating the dosage of dichlorohydantoin is:

[0022] m(Fe 2+ )≈a·ΔCST+b·ΔSRF·pH+c·pH 2 +d-form 1

[0023]

[0024] m(Fe 2+ )+k·m(DCDMH)=l·ΔCST+m·ΔCST·pH+n·pH 2 Formula 3

[0025] Where ΔCST represents the CST reduction rate at a certain moment in the reaction process compared to the initial reaction; ΔSRF represents the SRF reduction rate at a certain moment in the reaction process compared to the initial reaction; m(DCDMH) represents the dosage of dichlorohydantoin; m(Fe 2+ ) represents the dosage of FeSO4·7H2O; a∈[40,60], b∈[0.5,1.5], c∈[-2.5,0], d∈[-10,10], e∈[80,100], f∈[0.1,0.3], g∈[20,40], h∈[-10,10], k∈[0.5,1.5], l∈[0.1,0.5], m∈[0.01,0.05], n∈[0,10].

[0026] The beneficial effects of this invention include the following:

[0027] 1) Simultaneous Good Dewatering and Disinfection Effects: This invention is the first to propose a method for simultaneously improving sludge dewatering performance and sludge disinfection. Compared to mainstream mechanical dewatering combined with the addition of polyacrylamide or iron salts, this invention can achieve both dewatering and sludge disinfection, reducing environmental risks. Dewatering performance: Sludge capillary time (CST) reduction rate can reach over 30%, and sludge specific resistance (SRF) reduction rate can reach over 60%; Disinfection performance: Microbial inactivation rate can reach over 30%, and total fecal coliform count <100 CFU / g DS.

[0028] 2) Improved oxidant utilization efficiency: Compared to classic advanced oxidative Fenton or Fenton-like reactions, this invention utilizes the low solubility of dichlorohydantoin (DCDMH) and Fe... 2+The sustained-release effect of the reaction can reduce the amount of reagents added and lower the treatment cost.

[0029] 3) Improve disinfection and sterilization efficiency: Commonly used disinfectants such as pure HClO are unstable, easily decompose, highly volatile, and difficult to transport; NaClO and Ca(ClO)2 have low effective chlorine content, at 10% and 30% respectively, resulting in low disinfection and sterilization efficiency. This invention uses DCDMH (with an effective chlorine content of approximately 70%) to replace commonly used chlorine-containing disinfectants, utilizing DCDMH to dissolve and slowly release HClO and Fe. 2+ The dual effect of activated DCDMH in generating strong oxidizing free radicals to disinfect sludge can greatly improve the efficiency of disinfection and sterilization.

[0030] 4) Establish an oxidation-regulation synergistic pathway: Fe 2+ Activation of DCDMH can generate Fe in situ. 3+ This further enhances the flocculation effect and improves the sludge dewatering performance.

[0031] 5) Blocking the generation of disinfection byproducts, green and harmless: This invention controls the pH value to 4-6, directionally generating HClO molecules instead of free chlorine, inhibiting the halogenation reaction with organic matter, blocking the generation of disinfection byproducts, and reducing environmental risks. Attached Figure Description

[0032] Figure 1 The CST and SRF values ​​are for the raw sludge and the sludge after the reaction in Examples 1-3.

[0033] Figure 2 The values ​​of fecal coliforms in the sludge after the reaction in Examples 1-3 are as follows;

[0034] Figure 3 The images show the three-dimensional fluorescence spectra of the raw sludge and the reacted sludge in Example 2, where a is the raw sludge and b is the reacted sludge.

[0035] Figure 4 The lactate dehydrogenase levels were measured in the raw sludge and the reacted sludge of Example 2.

[0036] Figure 5 The process flow and index testing for dewatering and disinfecting sludge according to the present invention. Detailed Implementation

[0037] This invention provides a method for improving sludge dewatering performance and promoting sludge disinfection, comprising the following steps:

[0038] 1) The sludge is subjected to natural sedimentation and filtration in sequence to obtain pretreated sludge;

[0039] 2) Pretreatment of sludge and Fe 2+The compounds are mixed, and the pH of the mixture is adjusted to 4-6 using acid to obtain acidic sludge;

[0040] 3) React acidic sludge with dichlorohydantoin to obtain the reacted sludge.

[0041] In this invention, the sludge in step 1) is preferably municipal sludge (sludge from urban sewage treatment plants), and the moisture content of the sludge is preferably ≥95%.

[0042] In this invention, the temperature of natural settling in step 1) is preferably 22-28°C, more preferably 23-27°C, and even more preferably 25-26°C; the time of natural settling is preferably 12-36h, more preferably 15-30h, and even more preferably 18-25h; the aperture of the sieve used for filtration is preferably 1-2mm, more preferably 1.2-1.8mm, and even more preferably 1.5mm.

[0043] In this invention, the purpose of natural sedimentation is to remove excess water from the sludge and to filter out excess impurities from the sludge.

[0044] In this invention, the acid in step 2) is preferably hydrochloric acid or sulfuric acid, and the concentration of the acid is preferably 1 to 3 mol / L, more preferably 1.5 to 2.5 mol / L, and even more preferably 2 mol / L.

[0045] In this invention, the pH value of the mixture is adjusted to the acidic range using acid to promote the dissolution of the reaction reagents while preventing the hydrolysis and transformation of the products.

[0046] In this invention, the Fe in step 2) 2+ The compound is preferably ferrous sulfate heptahydrate or ferrous chloride, and more preferably ferrous sulfate heptahydrate; Fe 2+ The mass of the compound is calculated based on the total suspended solids (TSS) of the sludge. The preferred dosage is 20–40 mg of Fe per 1 g of TSS. 2+ The compound, preferably with the addition of 25–35 mg of Fe, is further preferred. 2+ The compound, preferably 30 mg Fe, is preferred. 2+ Compounds.

[0047] In this invention, Fe 2+ The compound itself can improve dehydration performance through flocculation, and the dosage is less than that of DCDMH. The purpose is to induce advanced oxidation reactions, generate free radicals to disrupt cells and promote dehydration, Fe 2+ The mass of the compound is 20–40 mg / g TSS.

[0048] In this invention, the mixing temperature in step 2) is preferably 20-30°C, more preferably 23-28°C, and even more preferably 25-27°C. The mixing time is preferably 3-8 min, more preferably 4-7 min, and even more preferably 5-6 min. The mixing is preferably carried out under stirring conditions, and the stirring speed is preferably 150-200 rpm, more preferably 160-190 rpm, and even more preferably 170-180 rpm.

[0049] In this invention, the mass of DCDMH in step 3) is based on the total suspended solids of sludge. It is preferred to add 20-100 mg of DCDMH per 1 g of total suspended solids (TSS), more preferably 30-80 mg of DCDMH, and even more preferably 40-70 mg of DCDMH.

[0050] In this invention, the reaction temperature in step 3) is preferably 26-30°C, more preferably 27-29°C, and even more preferably 28°C. The reaction time is preferably 1.5-2.5 h, and even more preferably 2 h. The reaction is preferably carried out under stirring conditions, and the stirring speed is preferably 150-200 rpm, more preferably 160-190 rpm, and even more preferably 170-180 rpm.

[0051] In this invention, ferrous sulfate heptahydrate (FeSO4·7H2O) and DCDMH are solids; the reaction system mainly generates free radicals by activating DCDMH with ferrous sulfate heptahydrate, thereby playing a role in cell lysis and cell disruption.

[0052] The reaction temperature of this invention is 26–30°C, which facilitates faster dissolution of DCDMH and accelerates the reaction. The preferred stirring method is magnetic stirring or mechanical stirring at a speed of 150–200 rpm, which further facilitates faster dissolution of DCDMH and its reaction with Fe. 2+ Advanced oxidation reactions occur.

[0053] The reaction principle equation of this invention is as follows:

[0054] ①DCDMH + H₂O → HClO + X (X is an uncertain product)

[0055] ②Fe 2+ +HClO→Fe 3+ +Cl - +·OH

[0056] ③Fe 2+ +HClO→Fe 3+ +OH - +·Cl

[0057] Because DCDMH has low solubility, adjusting the pH to acidic levels is beneficial for the dissolution and hydrolysis of DCDMH to produce HClO. At the same time, an acidic pH helps prevent the decomposition of HClO and Fe. 2+ Hydrolysis deactivates the enzyme, promoting the normal progress of the reaction. Based on this, HClO in Fe... 2 + Catalysis generates ·OH (hydroxyl radicals) and ·Cl (chlorine radicals), which oxidize, cleave, and mineralize the organic matter in the sludge while simultaneously destroying cells, achieving water conversion and improving sludge dewatering performance. The Fe produced in the reaction also contributes to this process. 3+ Further enhance flocculation and improve sludge dewatering performance.

[0058] In this invention, TSS (total suspended solids in sludge, g / L) is determined as follows: a volume of municipal sludge after concentration, sedimentation, impurity removal, and mixing is weighed and dried at 103-105°C to constant weight, and the mass is recorded as M. Then, TSS = M / V.

[0059] In this invention, when the sludge concentration D ∈ (20, 25), the Fe is expressed as g / L (TSS). 2+ The formulas for calculating the DCDMH dosage are shown in Equations 1 to 3.

[0060] m(Fe 2+ )≈a·ΔCST+b·ΔSRF·pH+c·pH 2 +d-form 1

[0061]

[0062] m(Fe 2+ )+k·m(DCDMH)=l·ΔCST+m·ΔCST·pH+n·pH 2 Formula 3

[0063] Where ΔCST represents the CST reduction rate at a certain moment in the reaction process compared to the initial reaction; ΔSRF represents the SRF reduction rate at a certain moment in the reaction process compared to the initial reaction; m(DCDMH) represents the DCDMH dosage; m(Fe 2+ ) represents the dosage of FeSO4·7H2O; a∈[40,60], b∈[0.5,1.5], c∈[-2.5,0], d∈[-10,10], e∈[80,100], f∈[0.1,0.3], g∈[20,40], h∈[-10,10], k∈[0.5,1.5], l∈[0.1,0.5], m∈[0.01,0.05], n∈[0,10].

[0064] The steps for drug administration are as follows: first add Fe 2+A pH detector was used to monitor the pH in the reaction tank in real time, ensuring that the pH0 / pH1 (pH value before conditioning / pH value after pH adjustment) was 0.5–2 before adding DCDMH to initiate the reaction. The reaction temperature was 26–30℃, and the ORP (oxidation-reduction potential) was 300–1000 mV. The pH was continuously adjusted as the reaction progressed, and the achievable CST reduction rate, SRF reduction rate, and degree of microbial inactivation were preliminarily estimated based on the above calculation formulas.

[0065] The above-mentioned drug addition can be carried out automatically through automatic drug dosing equipment. The CST, SRF and their corresponding reduction rate are calculated in real time by sensor 1 connected to it, and the total number of microorganisms and fecal coliforms are measured by sensor 2. The enterprise can stop the drug dosing equipment according to its own dehydration and disinfection needs to determine the endpoint of the dehydration and disinfection reaction.

[0066] Sensor 1 is set to the following conditions:

[0067] Sensor 1 records CST and SRF data in three parallel sets every 10 minutes, starting from time 0. When... and Where A ∈ [30%, 70%], B ∈ [60%, 90%] The average CST value of the sludge before conditioning (three times). This represents the average CST of the sludge at a certain point in the conditioning process. The average value of three SRF tests on the sludge before conditioning. This represents the average of three SRF values ​​of the sludge at a specific moment during the conditioning process; it indicates a good dewatering effect and a low moisture content in the sludge cake. Enterprises can choose whether to terminate the dewatering reaction based on their own dewatering needs. When the added ferrous ions and DCDMH are at their minimum dosages, A is 30% and B is 60%; when A≈60% and B≈85%, the optimal effect is achieved, and further increasing the reaction time has little impact on the moisture content of the dewatered sludge cake.

[0068] Sensor 2 is set as follows:

[0069] Sensor 2 records the total number of microorganisms and the total number of fecal coliforms three times every 10 minutes, starting from time 0, and performs numerical calculations. The disinfection efficiency calculated by sensor 2 satisfies the following formula: and Items / g DS, where C∈[30%,50%] This represents the average of three total microbial count measurements of the sludge before conditioning. This represents the average of three total microbial count measurements of the sludge at a specific point in the conditioning process. This represents the average total fecal coliform count at a specific point in the conditioning process.

[0070] satisfy When the sludge dewatering and disinfection is completed and the sludge concentration is 1 g DS and meets the company's own disinfection and dewatering requirements, the sensors 1 and 2 transmit data, the power supply to the magnetic stirrer is cut off, and the reaction stops.

[0071] Sludge dewatering performance is determined by measuring CST (capillary suction time) and SRF (sludge specific resistance) using standard methods. CST and SRF are indicators for judging dewatering effect and are currently the most direct, rapid and accurate indicators for evaluating sludge moisture content. The lower the measured value, the better. The disinfection and sterilization effect is evaluated by measuring flow cytometry and total fecal coliform count.

[0072] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0073] In the embodiments, the sludge is the residual sludge from the secondary sedimentation tank of a wastewater treatment plant in Tianjin; DS is the amount of oven-dry sludge, in grams.

[0074] Example 1

[0075] The raw sludge was determined to have a moisture content of 97.87%, a TSS of 21.8 g / L, and an initial pH of 6.87 according to the method specified in the "Test Method for Sludge from Urban Wastewater Treatment Plants" (CJ / T221-20058). The sludge was allowed to settle naturally at 25℃ for 24 hours to remove excess water from the supernatant. Excess impurities were then filtered through a 2 mm sieve to obtain pretreated sludge.

[0076] 20 mg / g TSS of FeSO4·7H2O was added to the pretreated sludge, and the mixture was stirred at 180 rpm for 5 min at 28℃ to obtain a homogeneous solution. The pH of the solution was adjusted to 4.5 using 2 mol / L hydrochloric acid to obtain acidic sludge. 50 mg / g TSS of DCDMH was added to the acidic sludge, and the mixture was stirred at 180 rpm for 2 h at 28℃ to complete the reaction.

[0077] The sludge after reaction (conditioning) was tested for CST and SRF according to the standard "Test Methods for Sludge from Urban Wastewater Treatment Plants" (CJ / T221-2005). Compared with the sludge before conditioning, the CST reduction rate of the conditioned sludge was 49.5%, and the SRF reduction rate was 77.5%, indicating an effective improvement in sludge dewatering performance. The disinfection effect was measured, showing a microbial inactivation rate of 26.5% and a fecal coliform count of 65 CFU / g DS, which is lower than the 100 CFU / g DS requirement stipulated in the standard "Sludge Quality of Urban Wastewater Treatment Plants" (GB24188-2009), indicating a good disinfection effect.

[0078] Example 2

[0079] The raw sludge was determined to have a moisture content of 97.87%, a TSS of 21.8 g / L, and an initial pH of 6.87 according to the method specified in the "Test Method for Sludge from Urban Wastewater Treatment Plants" (CJ / T221-20058). The sludge was allowed to settle naturally at 25℃ for 24 hours to remove excess water from the supernatant. Excess impurities were then filtered through a 2 mm sieve to obtain pretreated sludge.

[0080] 30 mg / g TSS of FeSO4·7H2O was added to the pretreated sludge, and the mixture was stirred at 27°C and 180 rpm for 5 minutes to obtain a homogeneous solution. The pH of the solution was adjusted to 5 using 2 mol / L hydrochloric acid to obtain acidic sludge. 50 mg / g TSS of DCDMH was added to the acidic sludge, and the mixture was stirred at 27°C and 180 rpm for 2 hours to complete the reaction.

[0081] The sludge after reaction (conditioning) was tested for CST and SRF according to the standard "Test Methods for Sludge from Urban Wastewater Treatment Plants" (CJ / T221-20058). Compared with the sludge before conditioning, the CST reduction rate of the conditioned sludge was 57.1%, and the SRF reduction rate was 85.2%, indicating an effective improvement in sludge dewatering performance. The disinfection effect test showed that the microbial inactivation rate reached 32.6%, and the fecal coliform count was 32 CFU / g DS, which is lower than the 100 CFU / g DS requirement stipulated in the standard "Sludge Quality of Urban Wastewater Treatment Plants" (GB24188-2009), indicating a good disinfection effect.

[0082] Example 3

[0083] The raw sludge was determined to have a moisture content of 97.87%, a TSS of 21.8 g / L, and an initial pH of 6.87 according to the method specified in the "Test Method for Sludge from Urban Wastewater Treatment Plants" (CJ / T221-20058). The sludge was allowed to settle naturally at 25℃ for 24 hours to remove excess water from the supernatant. Excess impurities were then filtered through a 2 mm sieve to obtain pretreated sludge.

[0084] 30 mg / g TSS of FeSO4·7H2O was added to the pretreated sludge, and the mixture was stirred at 28℃ for 5 min on a magnetic stirrer at 180 rpm to obtain a homogeneous solution. The pH of the solution was adjusted to 5.2 using 2 mol / L hydrochloric acid to obtain acidic sludge. 100 mg / g TSS of DCDMH was added to the acidic sludge, and the mixture was stirred at 28℃ for 2 h on a magnetic stirrer at 180 rpm to complete the reaction.

[0085] The sludge after reaction (conditioning) was tested for CST and SRF according to the standard "Test Methods for Sludge from Urban Wastewater Treatment Plants" (CJ / T221-20058). Compared with the unconditioned sludge, the CST reduction rate of the conditioned sludge was 59.2%, and the SRF reduction rate was 85.6%, indicating an effective improvement in sludge dewatering performance. Disinfection results showed that the microbial inactivation rate reached 43.8%, and the fecal coliform count was 12 CFU / g DS, which is lower than the 100 CFU / g DS requirement stipulated in the standard "Sludge Quality of Urban Wastewater Treatment Plants" (GB24188-2009), indicating good disinfection effect.

[0086] The CST and SRF values ​​of the raw sludge and the sludge after the reaction in Examples 1-3 are as follows: Figure 1 As shown; the measured values ​​of fecal coliforms in the sludge after the reaction in Examples 1-3 are as follows. Figure 2 As shown.

[0087] The three-dimensional fluorescence spectra of the raw sludge and the reacted sludge in Example 2 are shown below. Figure 3 As shown, a represents the original sludge, and b represents the sludge after the reaction. The three-dimensional fluorescence spectrum is used to determine the degree of EPS structural damage. The darker the fluorescence intensity of the peak in the figure, the more severe the EPS damage (corresponding to the third value of the coordinates in peak1 and peak2, the darker the fluorescence, the lower the value). This is beneficial for the release of water bound inside the EPS.

[0088] The lactate dehydrogenase levels of the raw sludge and the reacted sludge in Example 2 are as follows: Figure 4 As shown, lactate dehydrogenase is a biological enzyme that exists only inside cells. When the cell membrane is damaged, lactate dehydrogenase is released into the extracellular space and can be detected. Therefore, it can be used to qualitatively analyze the degree of cell damage and cell death.

[0089] The process flow and index testing for sludge dewatering and disinfection of the present invention are as follows: Figure 5 As shown.

[0090] This invention proposes a method based on Fe 2+ This invention relates to a sludge dewatering method using activated DCDMH, where DCDMH slowly dissolves in water to release chlorine-containing substances, thereby killing pathogenic microorganisms. 2+ Upon activation, active species such as Cl-, ·OH (hydroxyl radicals), and HClO are released to penetrate the EPS layer, oxidizing and decomposing hydrophilic polysaccharides / proteins and disrupting pathogen cell membranes, achieving a synergistic effect of enhanced dehydration and pathogen inactivation. Simultaneously, Fe... 2+ Oxidized to Fe 3+This further enhances sludge flocculation and improves sludge dewatering performance. In addition, DCDMH possesses slow-release properties, maintaining the continuous generation of active chlorine species in the reaction system through the gradual breaking of Cl-N bonds. Compared to the traditional Fenton process, this reduces the amount of reagents required, thereby lowering treatment costs. This invention is based on Fe2... + The novel advanced oxidation system that activates DCDMH establishes a triple synergistic mechanism of oxidation-dehydration-disinfection, simultaneously achieving deep sludge dehydration and efficient inactivation of pathogens.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving sludge dewatering performance while promoting sludge disinfection, characterized in that, It includes the following steps: 1) The sludge is subjected to natural sedimentation and filtration in sequence to obtain pretreated sludge; 2) Pretreatment of sludge and Fe 2+ The compounds are mixed, and the pH of the mixture is adjusted to 4-6 using acid to obtain acidic sludge; 3) React acidic sludge with dichlorohydantoin to obtain the reacted sludge.

2. The method according to claim 1, characterized in that, Step 1) The sludge is municipal sludge with a moisture content ≥95%.

3. The method according to claim 1 or 2, characterized in that, The temperature for natural settling in step 1) is 22-28℃, and the natural settling time is 12-36h; the mesh size of the sieve used for filtration is 1-2mm.

4. The method according to claim 3, characterized in that, The acid mentioned in step 2) is hydrochloric acid or sulfuric acid, and the concentration of the acid is 1 to 3 mol / L.

5. The method according to claim 3, characterized in that, Step 2) The Fe 2+ The compound is ferrous sulfate heptahydrate or ferrous chloride; Fe 2+ The mass of the compound is calculated based on the total suspended solids in the sludge. For every 1g of total suspended solids in the sludge, 20–40 mg of Fe is added. 2+ Compounds.

6. The method according to claim 1 or 5, characterized in that, Step 2) The mixing temperature is 20-30℃, the mixing time is 3-8 minutes, the mixing is carried out under stirring conditions, and the stirring speed is 150-200 rpm.

7. The method according to claim 6, characterized in that, Step 3) The mass of dichlorohydantoin is calculated based on the total suspended solids in the sludge, with 20-100 mg of dichlorohydantoin added per 1 g of total suspended solids in the sludge.

8. The method according to claim 7, characterized in that, The reaction temperature in step 3) is 26-30℃, the reaction time is 1.5-2.5h, and the reaction is carried out under stirring conditions at a stirring speed of 150-200rpm.

9. The method according to claim 8, characterized in that, When the sludge concentration D∈(20,25), expressed in g / L(TSS), Fe 2 + The formula for calculating the dosage of dichlorohydantoin is: m(Fe 2+ ) ≈ a·ΔCST + b·ΔSRF·pH + c·pH 2 + d Equation 1 m(Fe 2+ ) + k·m(DCDMH) = l·ΔCST + m·ΔCST·pH + n·pH 2 Equation 3 Wherein, ΔCST represents the CST reduction rate at a certain moment in the reaction process compared to the initial reaction; ΔSRF represents the SRF reduction rate at a certain moment in the reaction process compared to the initial reaction; m(DCDMH) represents the dosage of dichlorohydantoin; m(Fe 2+ ) represents the dosage of FeSO4·7H2O; a∈[40,60], b∈[0.5,1.5], c∈[-2.5,0], d∈[-10,10], e∈[80,100], f∈[0.1,0.3], g∈[20,40], h∈[-10,10], k∈[0.5,1.5], l∈[0.1,0.5], m∈[0.01,0.05], n∈[0,10].

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