CN108083609A - A kind of method that municipal sludge is nursed one's health by composite reagent - Google Patents

Abstract

The invention discloses a kind of methods that municipal sludge is nursed one's health by composite reagent.Comprise the following steps：（1）PH value is first adjusted using acid solution, then adds in iron powder and active powdered carbon, after being thoroughly mixed uniformly, starts aerator and is nursed one's health, a part of substance in sludge is made mutually to be transferred to from mud in liquid phase；（2）Persulfate is added in sludge after previous step conditioning, ferrous ion activates persulfate, re-oxidation breaking sludge, so that combination water, absorption water, Interstitial Water and the abjection of free water section in sludge, to achieve the purpose that improve dewatering and increase SCOD, protein and polysaccharide in sludge supernatant；（3）After sludge conditioning, mechanical dehydration can obtain dewatered sludge.The moisture content of municipal sludge can be reduced to 55 ~ 60% by this method from 97 ~ 99%, and sludge specific resistance and volume greatly reduce, and combustion heat value greatly improves, and be advantageously implemented the innoxious of sludge, stabilisation, minimizing and recycling, had broad application prospects.

Description

A method for conditioning municipal sludge by compounding medicaments

technical field

The invention belongs to the technical field of sludge treatment, and in particular relates to a method for conditioning urban sludge by compounding medicaments applied in the deep dehydration of sludge.

Background technique

Municipal sludge is produced along with urban sewage treatment. With the rapid development of my country's society and economy, my country's sewage treatment business has been significantly developed, and the corresponding sludge production has also greatly increased, and the situation of sludge treatment and disposal is becoming more and more severe. As of September 2015, the total amount of sludge in my country has exceeded 30 million tons per year, and the disposal rate is only 56%. The moisture content in the sludge is as high as 95%~99%, the organic matter content is high, and there are also pathogenic bacteria, parasite eggs, heavy metals and some toxic and harmful refractory organic substances, etc. Therefore, after the sludge that has not been properly treated and disposed of enters the environment, Not only will it bring secondary pollution, but it will also pose a serious threat to the ecological environment and human activities. Sludge disposal methods mainly include landfill, incineration, composting and other main ways, among which landfill and incineration are more widely used in engineering practice. However, the high water content of dewatered sludge has always been an important factor restricting the subsequent treatment and disposal of municipal sludge. At present, sewage treatment plants usually use cationic polyacrylamide (CPAM) and polyaluminum chloride (PAC) to condition the thickened sludge, and then use belt filter press or centrifugal mechanical dehydration. However, because PAM long-chain adsorption bridging is easy to form clumps to wrap part of the water, the water content of the mud cake after dehydration is still as high as about 80%. The dehydrated sludge cannot reach the mechanical index, and the monomer of PAM is highly toxic, which is easy to cause secondary pollution. High sludge moisture content not only increases the cost of sludge transportation, but also makes the subsequent treatment and disposal of sludge more difficult. Therefore, the deep dehydration of sludge (reducing the water content to below 60%) is the key to the subsequent treatment and disposal of sludge.

Common sludge conditioning techniques include physical methods such as thermal conditioning, freezing conditioning, ultrasonic conditioning, and microwave conditioning; chemical conditioning methods such as inorganic flocculants, organic polymer flocculants, and electrochemistry, as well as sludge anaerobic fermentation and aerobic digestion. and other biological conditioning methods. The physical conditioning method has high energy consumption, and the cost factor limits the practical engineering application and promotion; the biological conditioning method has a relatively late research origin, so its application is seldom; the sludge chemical conditioning method is currently the most widely used sludge conditioning technology. In engineering practice, sludge is usually treated with two or more compounding conditions such as aluminum salt, iron salt, fly ash and lime. Although the water content of the sludge can be greatly reduced, the amount of conditioning agent is large and greatly This increases the dry weight of the sludge after dehydration, which brings new problems to the subsequent treatment and disposal of the sludge. Using the activated persulfate oxidation method alone can effectively decompose microbial cells and extracellular polymer EPS, but it cannot form a porous skeleton structure, so the improvement of dehydration performance is limited. Moreover, the cost increase caused by the large dosage will limit its practical application. Therefore, it is very important to develop efficient, safe and economical sludge dehydration conditioning methods for sludge disposal and resource utilization, and the key is to destroy the structure of sludge flocs and promote the release of sludge bound water and intracellular water.

Contents of the invention

Effective conditioning of sludge is the key to achieve efficient sludge dewatering. The chemical conditioning method has the advantages of fast speed, good effect and strong engineering practicability. Aiming at the shortcomings and deficiencies of the existing chemical methods, the invention provides a method for regulating municipal sludge by compounding medicaments. The method can not only effectively improve the sludge dehydration performance, but also not significantly increase the dry weight of the sludge, and is beneficial to the subsequent disposal and resource utilization of the sludge.

A method for conditioning municipal sludge through medicament compounding, comprising the steps of:

a) Inject the sludge produced by the sewage treatment plant into the conditioning tank, and add acid solution to it to adjust the pH of the sludge to 2~4; add iron powder and activated carbon powder, start the aeration device, stir evenly, and fully react 20min;

b) Add persulfate to the sludge after step a reaction, the dosage of persulfate is 1.0 mmol/gVSS, and keep the molar ratio of ferrous ion and persulfate ion between 1.0~1.5, After adding, stir well and react for 20 minutes;

c) Introduce the sludge conditioned in step b into a filter press for press filtration and dehydration, keep it under a pressure of 0.8~3MPa for 20~40min, release the pressure and discharge the material after the pressure maintaining is completed.

The acid solution described in step a is spent acid of sulfuric acid or hydrochloric acid.

The iron-to-carbon ratio of the iron powder and activated carbon powder described in step a is 1, and the amount of iron powder added per liter of sludge is 2-3g.

The persulfate described in step b is potassium persulfate or sodium persulfate, and the dosage is about 0.18-0.42g persulfate per gram of dry mud.

In steps a and b, the rotating speed adopted for fully stirring evenly is 100-300 r/min, and the reaction time is 20 minutes.

The filter press used is a plate and frame filter press.

The working principle of the present invention is as follows: the method of the present invention combines iron-carbon micro-electrolysis and Fe ²⁺ activated persulfate oxidation, and utilizes the skeleton construction and adsorption characteristics of activated carbon powder, which not only improves the dewatering performance of sludge, It also greatly improves the calorific value of the mud cake after dehydration. After the acid solution is added, the pH value of the sludge can be adjusted in advance, which is conducive to the occurrence of iron-carbon micro-electrolysis reaction after the addition of iron powder and activated carbon powder. Second, the iron and ferrous ions produced by the micro-electrolysis reaction can react with persulfate added later to activate persulfate ions and generate strong oxidant sulfate radicals (·SO ₄ ^- ), which can fully destroy sludge The floc structure makes more bound water in the sludge converted into free water that is easy to remove. At the same time, activated carbon powder can absorb part of the sludge to form a permeable and firm lattice structure, which ensures that the filter cake in the mechanical dehydration process The permeability improves the dehydration speed in the filtration and compression stages. In addition, the sludge colloid is negatively charged, and the iron ions produced during the reaction process can not only play the role of adsorption neutralization, reduce the surface charge of the sludge colloid, but also reduce or eliminate the zeta potential of the sludge colloid, effectively compressing the double layer , so that the repulsion between the particles is reduced, and the sludge flocculation and sedimentation are promoted. To sum up, the method of the present invention greatly improves the efficiency of sludge conditioning, improves the dehydration performance of sludge, and reduces the treatment cost. The specific resistance of the sludge conditioned by the method of the present invention is reduced by about 90%, the water content of the sludge is reduced from 97-99% before conditioning to 55-60%, the volume of the sludge is greatly reduced, and the treated sludge is toxic and harmful The content of substances and pathogens is very low, which is convenient for sludge transportation and subsequent treatment and disposal.

Detailed ways

The principles and features of the present invention are described below, and the examples given are only used to explain the present invention, and are not intended to limit the scope of the present invention.

1. Embodiment 1

The sludge conditioned in this example is the residual sludge produced after the treatment of urban domestic sewage by the ^A2 /O process. The pH of the sludge is 7.2, the moisture content of the sludge is 97.77%, the total solid content of the sludge is 21930mg/L, and the volatile The solid content is 14010mg/L, and the sludge specific resistance is 1.69×10 ¹³ m/Kg. Take 500mL of the remaining sludge, adjust the pH to 2.5 with dilute sulfuric acid, add 1.25g iron powder and 1.25g activated carbon powder to it, and start the aeration device, stir the reaction time for 20min, the stirring reaction temperature is 25°C, and the stirring speed is 200r/ min; then add 1.67g of sodium persulfate to fully dissolve, stir for 20min, the stirring reaction temperature is 25°C, and the stirring speed is 180r/min. Then take 100mL of the conditioned sludge and use the Buchner funnel-vacuum filtration method to conduct the sludge specific resistance test, and record the filtration time. Another 100mL of the sludge was not conditioned. As a control, the sludge specific resistance test was also carried out using the Buchner funnel-vacuum filtration method, and the filtration time was recorded. The vacuum used for suction filtration is 0.08MPa.

The test results showed that compared with the control group, the vacuum was broken after 1 minute and 30 seconds of suction filtration in the conditioning group, and a suction filter mud cake was obtained. The moisture content of the mud cake after dehydration was 58.9%. In the control group, the vacuum was not broken after 20 minutes of suction filtration, and the moisture content of the dehydrated cake was as high as 79.6%. The specific resistance of the sludge after chemical conditioning is reduced to 1.78×10 ¹² m/Kg, the specific resistance reduction rate is 89.5%, and the sludge volume is greatly reduced.

2. Embodiment 2

The sludge conditioned in this embodiment is the residual sludge produced by the oxidation ditch process for treating urban domestic sewage, with a pH value of 6.7, a moisture content of the sludge of 96%, a total solid content of the sludge of 20100 mg/L, and a volatile solid content of 13510 mg /L, the sludge specific resistance is 2.76×10 ¹³ m/Kg. Get 500mL of the remaining sludge, adjust the pH to 2.9 with dilute sulfuric acid, add 1.32g of iron powder and 1.32g of activated carbon powder therein, and start the aeration device, the stirring reaction time is 20min, the stirring reaction temperature is 25 ° C, and the stirring speed is 240r/min. Then add 1.61 g of sodium persulfate to fully dissolve, stir for 20 minutes, the stirring reaction temperature is 25° C., and the stirring speed is 200 r/min. Then take 100mL of the conditioned sludge and use the Buchner funnel-vacuum filtration method to conduct the sludge specific resistance test, and record the filtration time. This group serves as the conditioning group.

Another 100mL of the remaining sludge was not conditioned, and the sludge specific resistance test was also carried out by Buchner funnel-vacuum filtration method, and the suction filtration time was recorded. As a control group 1.

Finally, take 100 mL of the remaining sludge, add 0.2 g of ferric chloride, add 5 g of quicklime after stirring, continue stirring, add 0.6 mL of PAM solution with a mass fraction of 1%, and react for 20 minutes after stirring evenly. The stirring reaction temperature is 25 °C. The sludge specific resistance test was carried out by Buchner funnel-vacuum filtration method, and the filtration time was recorded. As the control group 2.

The vacuum used for suction filtration is 0.08MPa.

The test results showed that compared with the control group 1, the conditioning group was vacuum-broken when the suction was filtered for 1 minute and 40 seconds, and a suction-filtered mud cake was obtained. The moisture content of the mud cake after dehydration was 57.4%. The sludge specific resistance of the conditioning group decreased to 2.3×10 ¹² m/Kg, and the specific resistance reduction rate was 91.7%, indicating that the dewatering performance was significantly improved. While the control group 1 was vacuum-filtered for 20 minutes, the vacuum was not broken, and the moisture content of the obtained dewatered cake was as high as 78.8%. Control group 2 obtained cracked mud cake by suction filtration for 10 minutes. The sludge specific resistance was 6.3×10 ¹² m/Kg. Compared with control group 1, the specific resistance reduction rate was 77.17%, and the moisture content of dewatered sludge was 68.1%. Sludge dewatering performance becomes better.

The two conditioning methods of the control group 2 and the conditioning group both significantly improved the dewatering performance of the sludge, and the dehydration effect of the conditioning group was more significant, and the dosage of chemicals was relatively small, which was an acceptable range in actual engineering.

3. Embodiment 3

The sludge conditioned in this example is the remaining sludge produced after the treatment of urban domestic sewage by the A ² /O process. The pH value is 7.12, the moisture content of the sludge is 98%, the total solid content of the sludge is 19650 mg/L, and the volatile solids The content is 13170mg/L, and the specific resistance of sludge is 2.14×10 ¹³ m/Kg.

Get 500mL of the remaining sludge, adjust the pH to 3.1 with dilute sulfuric acid, add 1.28g of iron powder and 1.28g of activated carbon powder therein, and start the aeration device, the stirring reaction time is 20min, the stirring reaction temperature is 25 ° C, and the stirring speed is 230r/min. Then add 1.57g of sodium persulfate to fully dissolve, stir for 20min, the stirring reaction temperature is 25°C, and the stirring speed is 180r/min. Then take 100mL of the conditioned sludge and use the Buchner funnel-vacuum filtration method to conduct the sludge specific resistance test, and record the filtration time. This group serves as the conditioning group.

Another 100mL of the remaining sludge was taken without conditioning, and the sludge specific resistance test was also carried out by using the Buchner funnel-vacuum filtration method, and the suction filtration time was recorded. As a control group 1.

Finally, take 100mL of the remaining sludge, add 0.5mL of PAC solution with a mass fraction of 20%, stir evenly, add 0.6mL of a PAM solution with a mass fraction of 1%, and stir for 20 minutes at a temperature of 25°C. The funnel-vacuum filtration method was used to conduct the sludge specific resistance test, and the filtration time was recorded. As the control group 2.

The vacuum used in the above suction filtration is 0.08MPa.

The test results showed that the vacuum was not broken for 20 minutes of suction filtration in control group 1, and the moisture content of the obtained dewatered cake was 79%; the vacuum was broken in control group 2 for 8 minutes of suction filtration, and the sludge specific resistance was reduced to 8.2×10 ¹² m/Kg , the specific resistance reduction rate was 61.7%, the moisture content of the obtained dewatered cake was 75.8%, and the dewatering performance of the sludge was improved to a certain extent; the conditioning group obtained the cracked mud cake after 80 seconds of suction filtration, and the sludge specific resistance decreased to 1.98 ×10 ¹² m/Kg, the specific resistance reduction rate was 90.74%, and the sludge dewatering performance was significantly improved.

It can be seen that both conditioning methods can improve the dewatering performance of sludge, and the effect of the method of the present invention is obviously better than that of using PAM and PAC two kinds of flocculants. After conditioning, the water content of the mud cake is greatly reduced, and the sludge is dry The base calorific value is significantly increased, which meets the needs of sludge treatment and disposal in actual projects.

Beneficial effects: the present invention aims at the present situation that when the existing chemical conditioning method is used for deep sludge dehydration, the amount of conditioning agent is large, the conditioning effect is average, and the weight of dehydrated biscuits increases a lot, which further affects the subsequent treatment and disposal of sludge. It can effectively improve the dewatering performance of sludge, and the amount of conditioner is low, and the calorific value of the dewatered cake is significantly increased, which can be subsequently incinerated.

By using the conditioning method provided by the invention for treatment, the specific resistance of the sludge is significantly reduced, the time for obtaining cracked mud cakes by suction filtration is greatly shortened, and the moisture content of the dehydrated cakes is significantly reduced. In addition, the dosage of chemicals is less, and the obtained dehydrated cake has a higher calorific value, which meets the requirements of practical engineering applications. The above performances are obviously better than the related prior art.

The above is an illustration of the method of the present invention to help understand the method of the present invention, but the implementation is not limited by the above examples. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (6)

1. a kind of method that municipal sludge is nursed one's health by composite reagent, includes the following steps：

A) sludge generated by sewage treatment plant is injected into conditioning tank, and adds in acid solution thereto, the PH of conditioning of mud is 2 ~4；Iron powder and active powdered carbon are added in, starts aerator, stirs evenly, fully react 20min；

B) persulfate is added in the sludge after step a reactions, the dosage of persulfate is 1.0 mmol/g VSS, And it between the molar ratio of holding ferrous ion and over cure acid ion is 1.0 ~ 1.5, stirs, reacts after addition 20min；

C) sludge after step b is conditioned is introduced into filter press and carries out filter-press dehydration, kept under the pressure of 0.8 ~ 3MPa 20 ~ 40min, release blowing after the completion of pressurize.

2. a kind of method that municipal sludge is nursed one's health by composite reagent according to claim 1, it is characterised in that：Step a The acid solution is sulfuric acid or the spent acid of hydrochloric acid.

3. a kind of method that municipal sludge is nursed one's health by composite reagent according to claim 1, it is characterised in that：Step a The iron powder and the iron-carbon ratio of active powdered carbon are 1, wherein the iron powder amount that every liter of sludge is added is 2 ~ 3g.

4. a kind of method that municipal sludge is nursed one's health by composite reagent according to claim 1, it is characterised in that：Step b The persulfate is potassium peroxydisulfate or sodium peroxydisulfate, and dosage is about that every gram of dry mud adds 0.18 ~ 0.42g persulfates.

5. a kind of method that municipal sludge is nursed one's health by composite reagent according to claim 1, it is characterised in that：Fully stir Rotating speed is 100 ~ 300 r/min, reaction time 20min used by mixing uniformly.

6. a kind of method that municipal sludge is nursed one's health by composite reagent according to claim 1, it is characterised in that：It is used Filter press be plate and frame type filter-press.