Reduction and high-value utilization method of activated sludge

Abstract

The invention relates to a reduction and high-value utilization method of activated sludge, which comprises the following steps of: introducing ozone nano-microbubbles into residual sludge, enabling ozone and the residual sludge to be subjected to wall-breaking cell lysis reaction, and then transferring into anaerobic hydrolytic acidification reaction; after the hydrolytic acidification reaction is finished, sodium hypochlorite is added and stirred, and meanwhile, ozone nano-micro bubbles are introduced again to carry out an ammonia / amine nitrogen denitrification reaction; after the ammonia / amine nitrogen denitrification reaction is finished, polyaluminum chloride is added for a coagulation phosphorus removal reaction; solid-liquid separation is carried out after phosphorus removal, a liquid phase is used as a carbon source for sewage treatment, and sludge reduction is realized after solid-phase filter pressing and dewatering. According to the method, the residual activated sludge is subjected to ozone nano-microbubble oxidation wall breaking and cell dissolving, hydrolytic acidification, chlorine-oxygen free radical (ClO) ammonia / amine nitrogen denitrification and coagulating sedimentation phosphorus removal, so that the reduction of the residual activated sludge and the efficient conversion of the sludge into a water treatment carbon source are realized.

Description

Technical Field

[0001] The present invention relates to a technology in the field of sewage and wastewater treatment, specifically a method for reducing and increasing the value of activated sludge. Background Art

[0002] The activated sludge process is widely used for the biological treatment of municipal and industrial wastewater, but it produces a considerable amount of excess sludge. Traditional treatment methods, such as landfill, incineration, and agricultural use, are limited due to secondary pollution and other issues. Therefore, sludge reduction and resource utilization are of great significance. Problems with existing sludge conversion technologies include: ① Existing advanced oxidation technologies, including ozone oxidation and Fenton oxidation, produce low concentrations of hydroxyl radicals (HO•), resulting in low efficiency in sludge cell wall disruption and lysis, and low concentrations of released dissolved organic matter and carbon sources. ② Existing advanced oxidation technologies, including those enhanced through a combination of existing technologies, can improve the ability of sludge cells to break down and lyse cells to a certain extent. However, the released soluble organic matter still contains large amounts of ammonia nitrogen, organic amine nitrogen, and inorganic phosphorus compounds. If these organic substances containing ammonia / amine nitrogen and inorganic phosphorus are directly used as carbon sources for wastewater treatment, the ammonia nitrogen, organic amine nitrogen, and phosphorus compounds mixed in them will also consume a large amount of carbon source, further reducing the efficiency of the carbon source. Although existing technologies can remove nitrogen from ammonia nitrogen and organic amine nitrogen in carbon sources through short-term nitrification and denitrification, this process is not only complex but also results in a significant loss of carbon source. ③ Using hydrolysis and acidification technology to convert sludge into a carbon source is time-consuming and inefficient. At the same time, the anaerobic process will also further release ammonia nitrogen, organic amine nitrogen, and inorganic phosphorus compounds, reducing the efficiency of the carbon source. Summary of the Invention

[0003] In response to the above-mentioned deficiencies in the prior art, the present invention proposes a method for reducing and maximizing the value of activated sludge. By subjecting the remaining activated sludge to ozone nano-bubble oxidation, cell wall breaking and lysis, hydrolysis and acidification, chlorine oxide free radical (ClO•) ammonia / amine nitrogen denitrification, and coagulation and precipitation phosphorus removal, the remaining activated sludge can be reduced and efficiently converted into a carbon source for water treatment.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a method for reducing and high-value utilization of activated sludge. The method comprises the following steps: introducing ozone nano-micro bubbles into excess sludge, causing the ozone and the excess sludge to undergo a cell wall-breaking and lysis reaction, and then switching to an anaerobic hydrolysis and acidification reaction; adding sodium hypochlorite after the hydrolysis and acidification reaction is completed and stirring is carried out, while introducing ozone nano-micro bubbles again to form ClO· to carry out an ammonia / amine nitrogen denitrification reaction; adding polyaluminum chloride after the ammonia / amine nitrogen denitrification reaction is completed to carry out a coagulation and phosphorus removal reaction; and carrying out solid-liquid separation after phosphorus removal, using the liquid phase as a carbon source for sewage treatment, and carrying out solid phase filter press dehydration to achieve sludge reduction.

[0006] The ozone nano-micro bubbles are introduced by setting the pressure of the nano-micro bubble device to 0.4-0.6 MPa and the ozone flow rate to 1-3 mg O3 L -1 Wet sludge min -1 , generating microbubbles with a diameter of 10-50μm and nanobubbles with a diameter less than 200nm.

[0007] The cell wall breaking and lysis reaction has a reaction time of 15 to 25 minutes.

[0008] The anaerobic hydrolysis and acidification reaction has a hydrolysis and acidification time of 48 to 72 hours.

[0009] The dosage of the sodium hypochlorite is 200-2000 mg L -1 .

[0010] The stirring speed is 3000 rpm -1 .

[0011] The ammonia / amine nitrogen denitrogenation reaction has a reaction time of 1-3 minutes.

[0012] The dosage of the polyaluminium chloride is 300~800mg L -1 Wet sludge.

[0013] Technical Effects

[0014] The present invention aims to solve the problem of converting excess activated sludge into high-quality carbon sources for water treatment, and thereby achieve a significant reduction in excess activated sludge. Ozone nano-micro bubble technology is used to enhance ozone decomposition to form highly oxidizing HO•, and HO• is used to oxidize the sludge cell walls to break and lyse the cells to release dissolved organic matter; by controlling the short wall-breaking and lysing reaction time of ozone nano-micro bubbles to 15-25 minutes, excessive oxidation of the system is prevented and energy consumption is reduced; then, anaerobic hydrolysis and acidification are cleverly used to further improve the conversion rate of sludge to dissolved organic matter - that is, the conversion rate of sludge to carbon source and the bioavailability of carbon source, thereby shortening the reaction time of ozone nano-micro bubbles, reducing energy consumption costs, and significantly shortening the anaerobic hydrolysis and acidification reaction time. The purpose of the present invention is to use the ammonia nitrogen and organic amine nitrogen released by the ClO• / Cl• oxidation sludge as nitrogen gas to achieve ammonia / amine nitrogen denitrification; polyaluminum chloride is used for coagulation and precipitation to remove phosphorus, thereby greatly reducing the phosphorus content in the liquid carbon source; after the above-mentioned process treatment of the present invention, the efficient conversion of sludge to carbon source is achieved, the resource utilization rate of sludge is improved, and the subsequent treatment volume of sludge is greatly reduced. More importantly, the prepared carbon source has enhanced bioavailability after anaerobic hydrolysis and acidification, and the nitrogen and phosphorus contents are significantly reduced, and finally a high-quality liquid carbon source is obtained. Therefore, compared with the existing technology, the sludge conversion efficiency to carbon source is high, the sludge reduction degree is large, the anaerobic acidification time is short, the carbon source concentration is high, the quality is high, the bioavailability is strong, the nitrogen content is low, the phosphorus content is low, the treatment process does not foam, and solid-liquid separation is easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Flowchart of an embodiment. DETAILED DESCRIPTION

[0016] Example 1

[0017] This embodiment includes the following steps: placing excess sludge in a reaction container, introducing ozone nano-micro bubbles into the excess sludge, the pressure of the nano-micro bubble device is 0.5 MPa, the bubbles are composed of micro bubbles with a diameter of 10-50 μm and nano bubbles with a diameter of less than 200 nm, and the ozone flow rate is 2 mg O3 L -1 Wet sludge min -1 , reaction time 20 min; after the ozone reaction is complete, anaerobic hydrolysis acidification reaction is carried out for 60 h; then sodium hypochlorite 1000 mg L -1 , stirring speed 3000 rpm -1 , and then introduce ozone nano-micro bubbles again, the pressure of the nano-micro bubble device is 0.5 MPa, and the ozone flow rate is 2 mg O3 L -1 Wet sludge min -1 The reaction time was 2 min for ammonia / amine nitrogen denitrification, and then polyaluminium chloride 700 mg L-1 Wet sludge is used for coagulation and phosphorus removal. After phosphorus removal, solid-liquid separation is performed. The dissolved chemical oxygen demand is ~ 55%. The liquid phase is used as a carbon source for wastewater treatment. The ammonia nitrogen concentration is 4.8 mg L -1 , total phosphorus concentration 9.2 mg L -1 , the sludge is reduced after solid phase filter pressing and dehydration.

[0018] The effects of Example 1 are illustrated below with four comparative examples.

[0019] Comparative Example 1

[0020] The residual sludge was placed in a reaction vessel. Ozone nanobubbles were introduced into the residual sludge. The pressure of the nanobubble device was 0.5 MPa. The bubbles were composed of microbubbles with a diameter of 10-50 μm and nanobubbles with a diameter of less than 200 nm. The ozone flow rate was 2 mg O3 L -1 Wet sludge.min -1 , and sodium hypochlorite 1000 mg / L was added, stirring was started simultaneously, the stirring speed was 3000 rpm, and the reaction time was 20 min. After the reaction was completed, the dissolved chemical oxygen demand was > 43%, solid-liquid separation was carried out, and the liquid phase was used as a carbon source for wastewater treatment. The ammonia nitrogen concentration was 5.3 mg / L and the total phosphorus concentration was 84.3 mg L -1 , solid phase filter press dehydration treatment.

[0021] Comparative Example 2

[0022] The remaining sludge was placed in a reaction vessel and ozone nano-bubbles were introduced into the remaining sludge. The pressure of the nano-bubble device was 0.5 MPa and the ozone flow rate was 2 mg O3 L -1 Wet sludge min -1 The reaction time was 20 min. After the ozone reaction was complete, the anaerobic hydrolysis and acidification process was started for 60 h. The dissolved chemical oxygen demand was ~ 55%, and the ammonia nitrogen concentration in the liquid phase was 350.7 mg L -1 , total phosphorus concentration 210.6 mg L -1 , solid phase filter press dehydration treatment.

[0023] Comparative Example 3

[0024] In the case of other conditions unchanged in Example 1, 700 mg L polyaluminium chloride was not added. -1 Wet sludge was used for coagulation and phosphorus removal. After the reaction, the ammonia nitrogen concentration in the liquid phase was 5.1 mg L -1 , total phosphorus concentration 215.2 mg L -1 .

[0025] Comparative Example 4

[0026] In Example 1, except that ozone nanobubbles were not introduced into the excess sludge in the first step of the process, other conditions remained unchanged. After the final solid-liquid separation, the soluble chemical oxygen demand of the excess sludge was <7%.

[0027] Example 2

[0028] This embodiment includes the following steps: placing excess sludge in a reaction container, introducing ozone nano-micro bubbles into the excess sludge, the nano-micro bubble device pressure is 0.4 MPa, and the ozone flow rate is 1 mg O3 L -1 Wet sludge min -1 , reaction time 25min; after the ozone reaction is complete, anaerobic hydrolysis acidification is carried out for 48h; then sodium hypochlorite 200mg L -1 , stirring speed 3000 rpm -1 , and ozone nano-micro bubbles were introduced, the pressure of the nano-micro bubble device was 0.4 MPa, and the ozone flow rate was 1 mg O3L -1 Wet sludge min -1 The reaction time was 1 min for ammonia / amine nitrogen denitrification, and then 300 mg L polyaluminium chloride was added. -1 Wet sludge was used for coagulation and phosphorus removal. After phosphorus removal, solid-liquid separation was performed. The dissolved chemical oxygen demand was 54%. The liquid phase was used as a carbon source for wastewater treatment. The ammonia nitrogen concentration was 8.1 mg L -1 , total phosphorus concentration 12.2 mg L -1 , the sludge is reduced after solid phase filter pressing and dehydration.

[0029] Example 3

[0030] This embodiment includes the following steps: placing excess sludge in a reaction container, introducing ozone nano-micro bubbles into the excess sludge, the nano-micro bubble device pressure is 0.6 MPa, and the ozone flow rate is 3 mg O3 L -1 Wet sludge min -1 , reaction time 15min; after the ozone reaction is complete, enter anaerobic hydrolysis acidification, time 72h; then add sodium hypochlorite 2000 mg L -1 , stirring speed 3000 rpm -1 , and ozone nano-micro bubbles were introduced, the pressure of the nano-micro bubble device was 0.6 Mpa, and the ozone flow rate was 3 mg O3L -1 Wet sludge min -1 The reaction time was 3 min for ammonia / amine nitrogen denitrification, and then 800 mg L polyaluminium chloride was added. -1 Wet sludge was used for coagulation and phosphorus removal. After phosphorus removal, solid-liquid separation was performed. The dissolved chemical oxygen demand was 56%. The liquid phase was used as a carbon source for wastewater treatment. The ammonia nitrogen concentration was 7.1 mg L -1, total phosphorus concentration 9.0 mg L -1 , the sludge is reduced after solid phase filter pressing and dehydration.

[0031] Compared to existing technologies, this method first utilizes the localized high temperature and high pressure generated by the collapse of nano-micro bubbles, coupled with ozone to generate a large amount of HO·, promoting sludge cell wall lysis and releasing organic matter from the cell sap. This process then utilizes anaerobic hydrolysis and acidification to further enhance the hydrolysis and acidification of lysed cell wall materials and cell wall fragments, increasing the sludge's conversion rate to a carbon source and generating substances such as fatty acids that are more readily utilized by microorganisms, thereby improving conversion quality. Because the ozone nano-micro bubbles disrupt the cell walls and lyse the sludge, the hydrolysis and acidification time of this method is significantly shortened, from the traditional 10+ days to 48-72 hours. The ammonia nitrogen and organic amine nitrogen produced in the cell wall breaking and lysis process and the anaerobic hydrolysis and acidification process are efficiently denitrified by the high concentration of HO• formed by ozone nano-micro bubbles and the selective and rapid reaction with hypochlorite to generate ClO•. Compared with other denitrification methods, the denitrification of ammonia nitrogen and organic amine nitrogen oxidized by ClO• has good selectivity, fast denitrification rate, no interference from strong oxidizing species such as HO• (which can effectively avoid the formation of nitrate nitrogen), and low toxic by-products. In addition, the local high temperature and high pressure and the strong oxidizing effect of HO• generated when the ozone nano-micro bubbles collapse can also remove Cl in the system. - Oxidized to Cl·, Cl· can also participate in the cyclic denitrification of ammonia nitrogen and organic amine nitrogen, achieving efficient denitrification. Although existing advanced oxidation technologies such as ozone oxidation have also been used to treat ammonia nitrogen wastewater, the reaction of ammonia nitrogen with ozone and other HO· can only further convert it into nitrate nitrogen and cannot achieve ammonia nitrogen denitrification. Subsequently, phosphorus is removed through flocculation and precipitation of polyaluminum chloride. After solid-liquid separation, a high-conversion, high-quality, low-nitrogen and low-phosphorus liquid carbon source is obtained, and the solid phase is significantly reduced.

[0032] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.

Claims

1. A method for reducing activated sludge and increasing its value, characterized in that: By introducing ozone nano-bubbles into the residual sludge, the ozone and the residual sludge undergo a cell-breaking and lysis reaction, and then the anaerobic hydrolysis and acidification reaction is started; after the hydrolysis and acidification reaction is completed, sodium hypochlorite is added and stirred, and ozone nano-bubbles are introduced again to form ClO• to carry out ammonia / amine nitrogen denitrification reaction; after the ammonia / amine nitrogen denitrification reaction is completed, polyaluminum chloride is added to carry out coagulation and phosphorus removal reaction; after phosphorus removal, solid-liquid separation is carried out, and the liquid phase is used as the carbon source for sewage treatment. After the solid phase is dehydrated by filter press, the sludge is reduced.

2. The method for reducing and maximizing the value of activated sludge according to claim 1, wherein: The ozone nano-micro bubbles are introduced by setting the pressure of the nano-micro bubble device to 0.4-0.6 MPa and the ozone flow rate to 1-3 mg O3 L -1 Wet sludge min -1 , generating microbubbles with a diameter of 10-50μm and nanobubbles with a diameter less than 200nm.

3. The method for reducing and maximizing the value of activated sludge according to claim 1, wherein: The cell wall breaking and lysis reaction has a reaction time of 15 to 25 minutes.

4. The method for reducing and maximizing the value of activated sludge according to claim 1, wherein: The anaerobic hydrolysis and acidification reaction has a hydrolysis and acidification time of 48 to 72 hours.

5. The method for reducing and maximizing the value of activated sludge according to claim 1, wherein: The dosage of the sodium hypochlorite is 200-2000 mg L -1 .

6. The method for reducing and maximizing the value of activated sludge according to claim 1, wherein: The stirring speed is 3000 rpm -1 .

7. The method for reducing and increasing the value of activated sludge according to claim 1, wherein: The ammonia / amine nitrogen denitrogenation reaction has a reaction time of 1-3 minutes.

8. The method for reducing and increasing the value of activated sludge according to claim 1, wherein: The dosage of the polyaluminium chloride is 300~800mg L -1 Wet sludge.

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