CN110467332A - A kind of efficient sludge conditioning and dewatering - Google Patents

Abstract

The invention discloses a method for sludge conditioning-horizontal electric field dehydration. The main steps of the method are as follows: (1) ultrasonically treat the sludge; (2) adjust the temperature and pH of the sludge; (3) in the sludge Add Thiobacillus, siderite, and persulfate, mix evenly, and react for a certain period of time; (4) connect to a horizontal electric field for dehydration. The invention combines ultrasound to destroy microbial cells, thiobacteria to promote the oxidation reaction of siderite and persulfate, stimulate the generation of sulfate radicals, form the redox cycle of Fe(II), crack the sludge structure, and combine the horizontal electric field to carry out Dehydration, give full play to their respective advantages and produce a synergistic effect, reducing the moisture content of the conditioned sludge to 50‑70%. This conditioning method has clear steps and simple operation, avoids excessive Fe ²⁺ generated by adding too much siderite, saves cost, has obvious dehydration effect, and has no secondary pollution.

Description

A kind of efficient sludge conditioning and dehydration method

technical field

An efficient sludge conditioning and dehydration method belongs to the technical field of environmental protection.

Background technique

In my country, due to the rapid development of society, economy and urbanization, municipal wastewater treatment plants (WWTPs) produce a large amount of sludge, and the sludge production is expected to exceed 60 million tons/year by 2020. The remaining sludge contains a large number of pathogenic bacteria, heavy metals and organic pesticides, which will bring harm to environmental quality and human health. The treatment and disposal of sludge has become a serious environmental problem. The "Water Pollution Prevention and Control Action Plan" promulgated by my country in 2015 specifically pointed out the need to promote sludge treatment and disposal. The sludge generated by sewage treatment facilities should be reduced, stabilized, harmless and recycled. How to effectively reduce Sludge moisture content is a key link in sludge treatment.

The treatment unit to achieve sludge reduction includes conditioning and dehydration. Among them, physical conditioning mainly includes microwave, ultrasonic, thermal hydrolysis, etc. Microwave and thermal hydrolysis mainly use external energy to generate heat, which makes sludge particles generate thermal motion, cells are thermally ruptured, and internal water is released. However, the general high-temperature pretreatment process not only consumes high energy and greatly increases the cost of pretreatment, but also causes secondary pollution to the environment with the generation of malodorous gas and toxic tail gas. Ultrasound uses ultrasonic waves to generate many bubble-like tiny cavities in the liquid, and the cavities burst instantaneously, causing the sludge bacteria micelles to be destroyed by a large shear force, thereby releasing the organic matter and water in them. The treatment effect is better, no Secondary pollution. Chemical conditioning is the use of chemical substances (pharmaceuticals) to improve sludge dewatering performance. It is simple to operate, stable in effect, and low in operating costs. It is a method widely used at present. Bioconditioning is a new technology that uses microorganisms or microbial metabolites to condition sludge. It uses carbon, nitrogen, phosphorus and other components in waste sludge as growth substrates to achieve sludge reduction and destroy the high-porosity structure of sludge. . Generally speaking, the effect of single conditioning is limited, therefore, combining different conditioning methods will be an option to improve sludge dewatering performance. The present invention adopts physical conditioning combined with chemical conditioning, which can further decompose cells inside EPS and sludge, release more bound water and convert it into free water.

The existing sludge dehydration methods can be divided into four categories: natural drying, heat drying, mechanical dehydration and electric dehydration. The natural drying method uses the gravitational action of sludge particles and natural evaporation to achieve the separation of mud and water. It occupies a large area and has a serious impact on the surrounding residents' environment. Thermal drying technology refers to the use of heating to evaporate the water in the sludge to achieve the effect of sludge-water separation, but the process equipment is complicated, and the operation requirements and energy consumption are high. Mechanical dehydration such as compression filtration, gravity settling, and centrifugation can effectively remove the free water of sludge, but interstitial water, surface water, and hydrated water are difficult to remove. During the dehydration process, with the removal of free water, particles will accumulate on the filter medium, resulting in the blockage of the medium, which will affect the further dehydration. Electric dehydration uses an external electric field to enhance the dewatering performance of sludge. The removal of water occurs on the inner and outer surfaces of each floc particle. Interstitial water and free water are removed at the same time, and the particle density increases uniformly, which can effectively improve sludge dehydration. Dehydration efficiency.

The Chinese patent application with publication number CN 109665692 A discloses a method for conditioning excess sludge based on Fenton reagent oxidation under hydrothermal conditions. This patent is to input excess sludge with a certain moisture content and Fenton's reagent into a high-pressure reactor, adjust the reaction temperature, reaction time, and initial pH to carry out hydrothermal oxidation reaction, and then dehydrate the conditioned sludge. This patent uses two kinds of strong oxidation reaction conditions to jointly condition the sludge, which improves the dehydration performance of the sludge and greatly reduces the volume of the sludge. However, this patent is carried out under high temperature and high pressure conditions, which not only consumes a lot of energy, but also high temperature is often accompanied by the problem of malodorous gas and toxic tail gas, which is relatively dangerous. Fenton's reagent needs to generate hydroxyl radicals under the condition of pH<3, the reaction conditions are relatively harsh, and it is not conducive to the subsequent treatment of sludge and easily causes secondary pollution; moreover, hydrogen peroxide is an oxidizing liquid that is easy to decompose , not easy to store and transport.

The Chinese patent application with publication number CN 109485229 A discloses a method for deep conditioning and dehydration of sludge while recovering a conditioning activator. This patent is to adjust the pH of the sludge first, and then add the zero-valent iron mixture and potassium hydrogen persulfate compound salt to heat the sludge. The treated sludge is magnetically separated to recycle the zero-valent iron. Sludge is dewatered. This patent is based on free radical chemical activation combined with thermal activation to synergistically condition sludge, which can realize the recycling of activators, but this method uses zero-valent iron as a conditioner. Because zero-valent iron has high surface energy, it is stable in the air. Very poor, and this method needs to add a large amount of zero-valent iron, accounting for 25-27% of the dry weight of the sludge, the cost is high, and the dehydration performance of the conditioned sludge is not very good.

Therefore, the present invention aims to provide an efficient conditioning sludge dewatering method with simple reaction conditions, stable reagents, convenient storage and transportation, low cost, and no secondary pollution to solve the problems existing in the prior art.

Contents of the invention

The object of the present invention is to provide an efficient sludge conditioning and dehydration method for the problems existing in the prior art. The conditioning method destroys the inner cells of the sludge by ultrasonically treating the sludge. Then, on the one hand, Thiobacillus can promote the reaction of siderite and persulfate to generate more sulfate radicals; on the other hand, Thiobacillus can reduce Fe(III) to Fe(II), forming the oxidation of Fe(II) The reduction cycle system does not need to add more reagents and at the same time oxidizes and breaks the EPS on the surface of the sludge flocs, releasing a large amount of bound water inside the EPS and sludge cells, so that the bound water is converted into free water, and at the same time it is in line with the level Electric field coupling realizes sludge dehydration. The sludge conditioning and dehydration method has simple reaction conditions, convenient storage and transportation of reagents, and can effectively reduce the moisture content of the sludge, realize sludge reduction, and facilitate subsequent treatment and disposal.

In order to achieve the above object, the present invention realizes through main steps such as physical conditioning, sludge pretreatment, chemical conditioning, sludge dehydration:

(1) Physical conditioning: Ultrasonic treatment of sludge to adjust to a suitable ultrasonic frequency;

(2) Sludge pretreatment: adjust the temperature and pH of the sludge to the appropriate range of Thiobacillus;

(3) Chemical conditioning: add a certain amount of Thiobacillus, siderite, and persulfate to the sludge, mix evenly, and stir for a certain period of time;

(4) Sludge dehydration: adjust the horizontal electric field voltage to dehydrate the sludge.

Among them, the sludge conditioning and dehydration technology is shown in Figure 1.

In particular, the dewatered sludge to be conditioned in the step is one of the remaining activated sludge, digested sludge or mixed sludge of the urban sewage treatment plant, with a moisture content of 96.00%-99.99%, preferably 97.50% -98.50%, the sludge concentration is between 18-27g/L, preferably 18-20g/L.

In particular, the physical conditioning in step (1) should be adjusted to an appropriate ultrasonic frequency, generally 20-100 kHz, preferably 5k-10 kHz.

In particular, in step (2), adjust the temperature and pH of the sludge to the suitable range for the survival of thiobacteria, the temperature is 15-40°C, preferably 25-30°C; the pH is 5-7, preferably 6-7.

Especially, the conditioning agent described in step (3) is siderite and persulfate, and the particle size of siderite is in the order of millimeters to microns, preferably 0.5-1.0mm, and the dosage is 0.05-0.2g/g TSS , preferably 0.05-0.1g/g TSS; the persulfate is preferably one or both of potassium persulfate or potassium hydrogen persulfate, and the dosage is 0.2-0.4g/g TSS, preferably 0.2-0.3g/ gTSS.

In particular, in step (3), the thiobacterium, siderite, and persulfate added to the sludge are mixed and stirred, and the stirring time is 30-60 minutes, preferably 30-40 minutes.

In particular, for the sludge electric dehydration described in step (4), the effective value of the horizontal DC electric field voltage is set at 20-60V, preferably 20-40V; the electric field dehydration time is set at 0.5-5h, preferably 2-3h.

The sludge dewatering method of the present invention has the following advantages:

1. The sludge conditioning and dehydration method of the present invention is a method of combining physical conditioning and chemical conditioning, which can give full play to the advantages of the two conditioning methods and realize deep dehydration of sludge. First, physical conditioning destroys the internal cell structure of the sludge, and then chemical conditioning promotes the reaction of siderite and persulfate through Thiobacillus, generating more sulfate radicals, cracking the sludge cells, and further releasing part of the bound water inside the cells. and transform into free water. Secondly, under the action of the horizontal electric field, the water released from the sludge is removed to improve the dehydration effect.

2. The sludge conditioning method of the present invention can release Fe in the ^siderite , give full play to the value of the siderite, form a redox cycle system of Fe(II), and save reagents.

3. The reaction condition of the sludge conditioning process of the present invention is mild and has a wide application range, and is applicable to sludge with a water content of more than 80%.

4. The material used in the sludge conditioning process of the present invention has stable properties, is convenient for storage, and has no secondary pollution.

5. The medicament used in the sludge conditioning process of the present invention is a solid medicament, which can be directly put into the solid powder when adding, and does not need to be prepared into a solution, which is simple and convenient.

6. The horizontal electric field used in the sludge dewatering process of the present invention can remove free water and part of bound water from the sludge under the action of electroosmosis, with simple operation and stable effect.

Description of drawings

Fig. 1 is a technical roadmap for sludge conditioning and dehydration of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the present invention will be described in further detail:

Implementation example 1:

The sludge to be dewatered is collected from a sewage treatment plant in a certain city, which uses the traditional activated sludge process to treat municipal sewage. The activated sludge collection point is located somewhere on the return path from the secondary sedimentation tank to the aeration tank. The sludge concentration (MLSS) reached 20.0g/L, the water content was 97.328%, and the temperature and pH were 25°C and 6.5, respectively.

1) Take 300mL of activated sludge and place it in a beaker;

2) Treat the sludge with ultrasonic waves with a frequency of 1k-5kHz for 5 minutes;

3) Add 0.02g/g TSS Thiobacillus and 0.05g/gTSS siderite and 0.10g/gTSS potassium hydrogen persulfate to the sludge, turn on the mechanical stirrer, stir the sludge, the stirring intensity is 100r/min, then keep stirring for 30min;

4) Gravity sedimentation is carried out to the conditioned sludge, and then the filtrate is discharged;

5) Turn on the DC power supply, set the effective value of the dehydration voltage to 20V, and control the dehydration time to 2h. Collect the sludge in the dehydration tank after the reaction, and measure its water content by gravimetric method.

The measurement results are shown in Table 1.

Implementation example 2:

The sludge to be dewatered is collected from a sewage treatment plant in a certain city, which uses the traditional activated sludge process to treat municipal sewage. The activated sludge collection point is located somewhere on the return path from the secondary sedimentation tank to the aeration tank. The sludge concentration (MLSS) reached 20.0g/L, the water content was 97.330%, and the temperature and pH were 25°C and 6.5, respectively.

1) Take 300mL of activated sludge and place it in a beaker;

2) Treat the sludge with ultrasonic waves with a frequency of 8k-10kHz for 25min;

3) Add 0.04g/g TSS Thiobacillus and 0.10g/gTSS Siderite and 0.20g/gTSS Potassium Hydrogen Persulfate to the sludge, turn on the mechanical stirrer, stir the sludge, the stirring intensity is 100r/min, then keep stirring for 10min;

4) Gravity sedimentation is carried out to the conditioned sludge, and then the filtrate is discharged;

5) Turn on the DC power supply, set the effective value of the dehydration voltage to 30V, and control the dehydration time to 2h. Collect the sludge in the dehydration tank after the reaction, and measure its water content by gravimetric method.

The measurement results are shown in Table 1.

Implementation example 3:

The sludge to be dewatered is collected from a sewage treatment plant in a certain city, which uses the traditional activated sludge process to treat municipal sewage. The activated sludge collection point is located somewhere on the return path from the secondary sedimentation tank to the aeration tank. The sludge concentration (MLSS) reached 20.0g/L, the water content was 97.322%, and the temperature and pH were 25°C and 6.5, respectively.

1) Take 300mL of activated sludge and place it in a beaker;

2) Treat the sludge with ultrasonic waves with a frequency of 1k-5kHz for 5 minutes;

3) Add 0.02g/g TSS Thiobacillus and 0.10g/gTSS siderite and 0.20g/gTSS potassium hydrogen persulfate to the sludge, turn on the mechanical stirrer, stir the sludge, the stirring intensity is 100r/min, then keep stirring for 30min;

4) Gravity sedimentation is carried out to the conditioned sludge, and then the filtrate is discharged;

5) Turn on the DC power supply, set the effective value of the dehydration voltage to 40V, and control the dehydration time to 3h. Collect the sludge in the dehydration tank after the reaction, and measure its water content by gravimetric method.

The measurement results are shown in Table 1.

Implementation example 4:

The sludge to be dewatered is collected from a sewage treatment plant in a certain city, which uses the traditional activated sludge process to treat municipal sewage. The activated sludge collection point is located somewhere on the return path from the secondary sedimentation tank to the aeration tank. The sludge concentration (MLSS) reached 20.0g/L, and the temperature and pH were 25°C and 6.5, respectively.

1) Take 300mL of activated sludge and place it in a beaker;

2) Treat the sludge with ultrasonic waves with a frequency of 5k-8kHz for 5 minutes;

3) Add 0.06g/g TSS Thiobacillus and 0.05g/gTSS siderite and 0.10g/gTSS potassium hydrogen persulfate to the sludge, turn on the mechanical stirrer, stir the sludge, the stirring intensity is 100r/min, then keep stirring for 30min;

4) Gravity sedimentation is carried out to the conditioned sludge, and then the filtrate is discharged;

5) Turn on the DC power supply, set the effective value of the dehydration voltage to 40V, and control the dehydration time to 3h. Collect the sludge in the dehydration tank after the reaction, and measure its water content by gravimetric method.

The measurement results are shown in Table 1.

Implementation example 5:

The sludge to be dewatered is collected from a sewage treatment plant in a certain city, which uses the traditional activated sludge process to treat municipal sewage. The activated sludge collection point is located somewhere on the return path from the secondary sedimentation tank to the aeration tank. The sludge concentration (MLSS) reached 20.0g/L, the water content was 97.328%, and the temperature and pH were 25°C and 6.5, respectively.

1) Take 300mL of activated sludge and place it in a beaker;

2) Treat the sludge with ultrasonic waves with a frequency of 5k-8kHz for 25min;

3) Add 0.04g/g TSS Thiobacillus and 0.10g/gTSS Siderite and 0.20g/gTSS Potassium Hydrogen Persulfate to the sludge, turn on the mechanical stirrer, stir the sludge, the stirring intensity is 100r/min, then keep stirring for 30min;

4) Gravity sedimentation is carried out to the conditioned sludge, and then the filtrate is discharged;

5) Turn on the DC power supply, set the effective value of the dehydration voltage to 30V, and control the dehydration time to 2h. Collect the sludge in the dehydration tank after the reaction, and measure its water content by gravimetric method.

The measurement results are shown in Table 1.

Implementation example 6:

The sludge to be dewatered is collected from a sewage treatment plant in a certain city, which uses the traditional activated sludge process to treat municipal sewage. The activated sludge collection point is located somewhere on the return path from the secondary sedimentation tank to the aeration tank. The sludge concentration (MLSS) reached 20.0g/L, the water content was 97.329%, and the temperature and pH were 25°C and 6.5, respectively.

1) Take 300mL of activated sludge and place it in a beaker;

2) Treat the sludge with ultrasonic waves with a frequency of 8k-10kHz for 25min;

3) Add 0.02g/g TSS Thiobacillus and 0.05g/gTSS siderite and 0.10g/gTSS potassium hydrogen persulfate to the sludge, turn on the mechanical stirrer, stir the sludge, the stirring intensity is 100r/min, then keep stirring for 10min;

4) Gravity sedimentation is carried out to the conditioned sludge, and then the filtrate is discharged;

5) Turn on the DC power supply, set the effective value of the dehydration voltage to 30V, and control the dehydration time to 2h. Collect the sludge in the dehydration tank after the reaction, and measure its water content by gravimetric method.

The measurement results are shown in Table 1.

Comparative example 1:

Except ultrasonic treatment time is 25min, all the other are identical with implementation example 1.

Comparative example 2:

Except that the ultrasonic frequency is 5k-8kHz, the others are the same as the implementation example 2.

Comparative example 3:

Be 10min except chemical conditioning stirring time, all the other are identical with embodiment example 3.

Comparative example 4:

Except that dehydration time is set to 2h, all the other are identical with embodiment example 4.

Comparative example 5:

Except that the dosage of Thiobacillus is 0.02g/g TSS, all the other are identical with embodiment example 5.

Comparative example 6:

Except that the dosage of Thiobacillus is 0.04g/g TSS, all the other are identical with embodiment 6.

Table 1 sludge dewatering effect of the present invention

Raw sludge moisture content (%) Moisture content of sludge after dehydration (%) Implementation Example 1 97.328 68.637 Implementation Example 2 97.330 65.328 Implementation Example 3 97.322 67.554 Implementation Example 4 97.327 66.325 Implementation Example 5 97.328 63.462 Implementation Example 6 97.329 66.879 Comparative example 1 97.328 67.027 Comparative example 2 97.330 64.864 Comparative example 3 97.322 68.137 Comparative example 4 97.327 67.013 Comparative example 5 97.328 62.968 Comparative example 6 97.329 65.975

The test results show that:

1. Ultrasonic conditioning of sludge - Thiobacillus/siderite/persulfate conditioning combined with horizontal electric field for dehydration can effectively reduce the moisture content of sludge;

2. During the sludge conditioning process, the dosage of conditioner increases, and the dehydration efficiency increases;

3. Increasing the stirring time during the sludge conditioning process is beneficial to the sludge dehydration effect;

4. Prolonging the dehydration time of the electric field and increasing the power supply voltage can effectively reduce the moisture content of the sludge;

5. Prolonging the ultrasonic time is beneficial to the sludge dewatering effect;

6. Changing the ultrasonic frequency has an impact on the sludge dewatering effect, but excessive ultrasonic frequency may lead to poor dehydration effect;

7. Increasing the dosage of bacterial agent will affect the sludge dehydration effect, but too large dosage of bacterial agent will make the dehydration effect worse.

Claims (9)

1. a kind of sludge conditioning and the method for dehydration, it is characterised in that combining ultrasonic cracks and Thiobacillus-siderite-persulfate Oxidation improves sludge, then carries out the operation of sludge electric dehydration；On the one hand Thiobacillus promotes siderite and persulfate anti- It answers, excites the generation of potentiometric titrations, Fe (III) can be reduced to Fe (II) by another aspect Thiobacillus, form Fe (II) Redox cycle system saves chemical reagent dosage；Ultrasound strengthens the above process, realizes the degradation of sludge EPS With the rupture of cell, combination water therein is converted into Free water, improves sludge electric dehydration effect.

2. the method as described in claim 1, it is characterised in that sludge is dirty using the excess sludge of municipal sewage plant, digestion Or mixtures thereof one of mud, moisture content 96.00%-99.99%, sludge concentration 18-27g/L.

3. the method as described in claim 1, it is characterised in that include the following steps:

(1) sludge is ultrasonically treated；

(2) temperature of sludge, pH are adjusted to the optimum range to Thiobacillus；

(3) a certain amount of Thiobacillus, siderite, persulfate are added into sludge, and carry out the stirring of certain time；

(4) by the sludge gravitational settling after conditioning, filtrate is discharged；

(5) power supply is opened, horizontal component of electric field voltage is adjusted, sludge is carried out dehydrating.

4. step (1) as claimed in claim 3, it is characterised in that the ultrasonication sludge 30- of frequency of use 20-100kHz 60min。

5. step (2) as claimed in claim 3, it is characterised in that the optimum range of Thiobacillus is as follows: temperature be 15-40 DEG C, PH is 5-7.

6. step (3) as claimed in claim 3, it is characterised in that improve the Thiobacillus added in the process, siderite, persulfuric acid Salt, Thiobacillus dosage are 0.02-0.10g/g TSS；Using the particle of millimeter to micron-scale, dosage is siderite 0.05-0.2g/g TSS；The dosage of persulfate is 0.2-0.4g/g TSS.

7. step (3) as claimed in claim 3, it is characterised in that churned mechanically revolving speed is set as 100-400r/min, stirs Mixing the time is 30-60min.

8. step (5) as claimed in claim 3, it is characterised in that the supply voltage of horizontal component of electric field dehydration is set as 20-60V, Dewatering time is 0.5-5h.

9. sludge conditioning dewatering as claimed in claim 3, it is characterised in that the moisture content of dehydrated sludge is up to 50- 70%.