Method for improving sludge dewatering performance effect applied to different sewage treatment processes

Abstract

The invention relates to the technical field of municipal sludge dewatering, in particular to a method for improving sludge dewatering performance of different typical sewage treatment processes. According to the method, firstly, the optimal working condition suitable for the municipal excess sludge is provided, secondly, persulfate conditioning parameters suitable for various municipal sludge are summarized, then an optimization model is established through a response surface method, the sludge conditioning efficiency of Fe (II) / PMS (persulfate) is enhanced, and the sludge conditioning efficiency of the municipal excess sludge is improved. By analyzing particle size distribution, protein, polysaccharide and three-dimensional fluorescence spectrum indexes before and after the sludge is conditioned by the activated persulfate oxidation method, and by taking the sludge dewatering performance as an evaluation index, the action mechanism of the sludge conditioned by the activated persulfate oxidation method is explored; and determining the influence of the internal structure of the sludge extracellular polymeric substance (EPS) on the sludge dewatering performance, and finally comparing the optimal fitting effect and experimental verification conclusion of AAO, oxidation ditch and MSBR sludge to obtain the optimal condition so as to effectively improve the sludge dewatering performance.

Description

Technical Field

[0001] The present invention relates to the technical field of municipal sludge dewatering, and particularly to the use efficiency of an activated persulfate agent applied to improving the sludge dewatering performance in the treatment of excess sludge from different processes. Background Art

[0002] In recent years, as a by-product of sewage and wastewater treatment, the safe disposal of sludge has attracted wide attention in the industry and outside.

[0003] Currently, the main sludge conditioning technologies are divided into physical methods, chemical methods and biological methods.

[0004] Physical conditioning technology: By destroying the microbial cell wall and EPS structure, the destruction of sludge flocs is achieved, causing the dissolution of organic matter inside the sludge flocs and the release of the bound water therein. It mainly includes heat treatment method, ultrasonic method and freeze-thaw method, etc. Disadvantages: The heat treatment method has the problem of high energy consumption caused by high temperature, which is difficult to solve. The construction and popularization of ultrasonic equipment and other aspects have hindered the practice of this technology in the field of sludge conditioning. In-depth research is also needed on the optimization control of this technology. The freeze-thaw method has relatively harsh use conditions and is severely limited by climate change.

[0005] Biological conditioning technology: It mainly includes biological enzyme method and biological leaching method. The biological enzyme treatment method improves the sludge dewatering performance by adding cellulase, lysozyme, protease, etc. This technology has mild action conditions and fast catalytic speed, but the action mechanism of this technology has not been fully clarified at present. Different from the rapid catalysis of biological enzymes, the biological leaching method has a longer application time due to the replacement of bacterial species in its action principle, and the longer action time also increases the difficulty of its engineering application.

[0006] Chemical conditioning technology: By adding agents to destroy sludge flocs, it mainly includes acid-base treatment method, coagulant, flocculant conditioning, advanced oxidation method. Although the acid-base conditioning technology is simple to use and easy to operate, problems such as the addition and storage of agents, the addition and maintenance of dosing equipment, and the pH neutralization after treatment limit its application. The method of adding polymer conditioning agents can improve the sludge dewatering performance to a certain extent, but it is difficult to improve its sludge dewatering performance significantly. The persulfate oxidation method is a research hotspot in sludge conditioning in recent years and is commonly used in the fields of treating refractory organic pollutants, soil remediation, etc. This technology provides a longer effective reaction time and can be activated by traditional methods such as sound, light, electricity, heat, Fenton oxidation method and combined technologies. While generating new free radicals, it does not narrow its application scope. Some studies have shown that this technology can significantly improve the sludge dewatering performance in the pretreatment stage of sludge dewatering, so this technology has been rapidly applied to the research of various sludge dewatering such as municipal sludge and paper-making sludge. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to take sludge flocs as the starting point and focus on the synergistic optimization of sludge flocs during actual conditioning.

[0008] To solve the above technical problems, the technical solution adopted by the present invention is as follows: applying the usage method of activated persulfate reagent to improve the sludge dewatering performance when treating the excess sludge of different processes, which is characterized in that: studying the influence of single factors on the sludge dewatering performance; exploring the sludge conditioning effect after applying it to the municipal sludge treated by different processes; carrying out the stirring process research on the Fe(Ⅱ) / PMS (persulfate) conditioned sludge; studying the dehydration conditioning mechanism of the Fe(Ⅱ) / PMS system on the sludge of three processes;

[0009] A further technical solution lies in that the conventional single factors are the dosage of PMS, the dosage of FeSO4, temperature and the initial pH of the sludge. According to the similarities and differences in the conditioning parameters and dewatering performance changes of different excess sludges, the persulfate conditioning parameters applicable to various municipal sludges are summarized as follows: the dosages of PMS and FeSO4 are both 1.2 mmol / gVSS (volatile suspended solids of sludge), the pH is 7, and it is not recommended to increase the temperature.

[0010] A further technical solution lies in taking the reduction rate of capillary suction time (CST) and sludge specific resistance (SRF) as the evaluation indexes of sludge dewatering performance.

[0011] A further technical solution lies in that the processes applied to the municipal sludge treated by different processes are AAO process, oxidation ditch process and MSBR process.

[0012] A further technical solution lies in that on the basis of the optimized parameters for conditioning sludge in the early stage of the conditioning efficiency enhancement of the ferrous-activated persulfate system for conditioning sludge, combined with the operation mode of adding polymer conditioning agent in the sewage treatment plant, exploring the influence of the change of stirring conditions after adding the agent on the conditioning efficiency of the activated persulfate for conditioning sludge, and establishing an optimization model by the response surface method to enhance the conditioning efficiency of the Fe(Ⅱ) / PMS for conditioning sludge.

[0013] A further technical solution lies in the research on the influence mechanism of the composition structure of extracellular polymeric substances (EPS) of sludge on the ferrous-activated persulfate for conditioning sludge. Through the analysis of the particle size distribution, protein, polysaccharide and three-dimensional fluorescence spectrum indexes of the sludge of three processes before and after being conditioned by the activated persulfate oxidation method, taking the sludge dewatering performance as the evaluation index, exploring the action mechanism of the activated persulfate oxidation method for conditioning sludge, and clarifying the influence of the internal structure of EPS on the sludge dewatering performance.

[0014] Beneficial effects: The present invention relates to a comparative study on various different sludges; in terms of optimizing the efficiency of improving sludge dewatering performance, the persulfate system is studied based on the actual operating conditions; and in terms of exploring the action mechanism, the focus is on the relationship between the sludge composition structure and sludge dewatering performance, and a method for improving the sludge dewatering performance of different typical sewage treatment processes is proposed. Brief Description of the Drawings

[0015] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0016] Figure 1 It is the effect diagram of the influence of the PMS dosage on the sludge dewatering performance in the present invention;

[0017] Figure 2 It is the effect diagram of the influence of the FeSO4 dosage on the sludge dewatering performance in the present invention;

[0018] Figure 3 It is the sludge response surface diagram during the sludge treatment of the AAO process in the present invention;

[0019] Figure 4 It is the sludge response surface diagram during the sludge treatment of the oxidation ditch process in the present invention;

[0020] Figure 5 It is the sludge response surface diagram during the sludge treatment of the MSBR process in the present invention;

[0021] Figure 6 It is the change diagram of the sludge dewatering performance before and after the treatment with the Fe(Ⅱ) / PMS system; Specific Embodiments

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0023] (1) To study the influencing factors of conditioning municipal sludge with the Fe(Ⅱ) / PMS system, the present invention uses the same evaluation indexes and experimental environment. By conditioning the excess sludge of the AAO oxidation ditch and MSBR processes with Fe(Ⅱ) / PMS, the capillary suction time (CST) reduction rate and sludge specific resistance (SRF) are used as the evaluation indexes of sludge dewatering performance, and single-factor experiments are adopted to investigate the influence of PMS dosage, FeSO4 dosage, initial pH, and initial temperature on sludge dewatering performance.

[0024] (See Appendix Figure 1 、 2 ).

[0025] (2) Research on the stirring process of conditioning municipal sludge by the Fe(Ⅱ) / PMS system. In this invention, the Box-Behnken design was carried out using Design-Expert 12 software. With the CST reduction rate as the response value, the PMS stirring speed, PMS stirring time, FeSO4 stirring speed, and FeSO4 stirring time were used as response factors to establish an experimental optimization with four levels and three factors. On the basis of the above-confirmed optimal conditioning parameters, the excess sludge from the AAO, oxidation ditch, and MSBR processes was used as the experimental object to investigate the influence effect of stirring parameters on the Fe(Ⅱ) / PMS-conditioned sludge, and to explore the optimal working conditions.

[0026] In the experimental design of stirring parameters, based on the above-optimized dosing conditions, the dosing sequence of adding PMS first and then FeSO4 was adopted. Except for the FeSO4 dosing amount of 1.4 mmol / gVSS for AAO sludge, the dosing amounts of PMS and FeSO4 for the three types of sludge were both 1.2 mmol / gVSS. The influence effect of four influencing factors, namely PMS stirring speed, PMS stirring time, FeSO4 stirring speed, and FeSO4 stirring time, on the dewatering performance of Fe(Ⅱ) / PMS-conditioned sludge was investigated.

[0027] Comparing the optimal fitting effect and experimental verification conclusions of AAO, oxidation ditch, and MSBR sludge, it is considered that when the PMS stirring speed is 100 r / min, the PMS stirring time is 19 min, the FeSO4 stirring speed is 230 r / min, and the FeSO4 stirring time is 60 min, Fe(Ⅱ) / PMS can effectively improve the sludge dewatering performance (see Appendix Figure 3 、 4 、5).

[0028] (3) This invention studies the dehydration conditioning mechanism of the Fe(Ⅱ) / PMS system on the sludge of three processes, and conducts research on the influence of the composition structure of sludge EPS and its internal proteins on the sludge dewatering performance. Using the excess sludge from the AAO, oxidation ditch, and MSBR processes as the experimental object, and the CST reduction rate as the evaluation index of sludge dewatering performance, the particle size distribution, protein and polysaccharide content, and changes in fluorescent protein components were investigated, and correlation analysis was carried out in combination with the sludge dewatering performance to reveal the internal action mechanism of the persulfate oxidation method for conditioning sludge. This study mainly analyzed the CST as the measurement index of sludge dewatering performance. The three types of sludge were respectively treated with the Fe(Ⅱ) / PMS system, and the changes in their sludge dewatering performance are shown in Appendix Figure 6 as follows.

[0029] It can be seen that the treatment effect of the oxidation ditch sludge is the worst, with the CST decreasing from 30.2 s to 25 s, and the CST reduction rate being only 17%. While the CST of the AAO sludge and MABR sludge decreased by about 40% after treatment. FromFigure 6 In comparison with the CST of [process names], the dewatering effect of the oxidation ditch is the best. This is because the sludge in the AAO and MSBR processes is in the late stage of the declining growth phase of the growth curve, while the oxidation ditch process belongs to the extended aeration method, and its sludge is in the endogenous respiration phase of the growth curve. The organic matter is stabilized, and the binding of a small amount of organic matter to bound water is weak, and more free water results in a lower CST of the oxidation ditch. Research shows that the treatment effect of the Fe(Ⅱ) / PMS system on the oxidation ditch sludge is less than that on the AAO and MSBR sludges (see attachment Figure 6 ).

Claims

1. A method for using an activated persulfate agent for improving sludge dewatering performance in treating excess sludge from different processes Characterized in that Taking sludge flocs as the starting point, it focuses on summarizing the synergistic optimization of sludge flocs during actual conditioning.

2. The method for using an activated persulfate agent for improving sludge dewatering performance in treating excess sludge from different processes according to claim 1, Characterized in that Study the influence of single factors on sludge dewatering performance. Each conventional single factor includes the dosage of persulfate (PMS), the dosage of FeSO4, temperature and initial pH.

3. The method for using an activated persulfate agent for improving sludge dewatering performance in treating excess sludge from different processes according to claim 1, Characterized in that Taking the reduction rate of capillary suction time (CST) and sludge specific resistance (SRF) as the evaluation indexes of sludge dewatering performance.

4. The method for using an activated persulfate agent for improving sludge dewatering performance in treating excess sludge from different processes according to claim 1, Characterized in that The processes used for municipal sludge treated by different processes are AAO process, oxidation ditch process and MSBR process.

5. The method for using an activated persulfate agent for improving sludge dewatering performance in treating excess sludge from different processes according to claim 1, Characterized in that Adjusting the co - addition of sludge extracellular polymer (PMS) and FeSO4 can reduce the side reactions of the conditioner with sludge. By adjusting the stirring parameters, the CST reduction rates of the three kinds of sludge have a variable range of 10 - 45%.

6. The method for using an activated persulfate agent for improving sludge dewatering performance in treating excess sludge from different processes according to claim 1, Characterized in that Investigate the particle size distribution, protein and polysaccharide contents and the changes of fluorescent protein components, and conduct a correlation analysis in combination with sludge dewatering performance, and it is concluded that the EPS structure and fluorescent protein composition of sludge are the key factors affecting sludge dewatering performance.

7. The method for using an activated persulfate agent for improving sludge dewatering performance in treating excess sludge from different processes according to claim 1, Characterized in that Through the research on the stirring process of conditioning municipal sludge by the Fe(Ⅱ) / PMS system and the research on the dehydration conditioning mechanism of the Fe(Ⅱ) / PMS system for sludge from three processes, it is concluded that the inventive method has good conditioning effects when applied to the sludge of MSBR and A2O processes. When applied to oxidation ditch sludge, the dehydration effect is not as good as the previous two processes but there is also an improvement.

8. The method for using an activated persulfate agent for improving sludge dewatering performance in treating excess sludge from different processes according to claim 1, Characterized in that According to the similarities and differences in the conditioning parameters and dewatering performance changes of different excess sludges, the persulfate conditioning parameters applicable to various municipal sludges are that the dosages of PMS and FeSO4 are both 1.2 mmol / gVSS, the PH is 7, and it is not recommended to increase the temperature.

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