Method for deeply treating organic micropollutants in leachate by coupling sludge biochar with ozone

Abstract

The invention discloses a method for deeply treating organic micropollutants in leachate by coupling sludge biochar with ozone. The method comprises the following steps: standing the sludge of a sewage treatment plant until sludge and water are separated, pouring out supernate, centrifuging the sludge, and drying to constant weight; grinding the dried sludge, pyrolyzing the sludge in a tubular furnace in an inert gas atmosphere, washing the pyrolyzed sludge with deionized water, and performing vacuum drying to obtain the sludge biochar. The sludge biochar is added into the secondary effluent of the landfill leachate at normal temperature and normal pressure, ozone is introduced, and the removal rate of the organic micropollutants can reach 90% or above after a continuous reaction is carried out for a certain time. The sludge biochar (SDBC) can efficiently activate ozone (O3) after high-temperature pyrolysis, the constructed SDBC / O3 system can react with most organic micropollutants, the reaction rate is high, and the influence of ions and pH in a water body is low.

Description

Technical Field

[0001] The invention relates to a method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone, and specifically to a method for deep treatment of organic micropollutants in leachate by coupling sludge biochar prepared by high-temperature pyrolysis of sludge with ozone, belonging to the technical field of water treatment. Background Art

[0002] At present, urban domestic waste is mainly disposed of by landfill and incineration, both of which will result in the generation of a large amount of leachate. Leachate is a high-concentration organic wastewater that contains a large amount of difficult-to-degrade organic micropollutants, inorganic salts, toxic heavy metals, pathogens, etc. Conventional biological and physical treatment processes are difficult to degrade multiple organic micropollutants at the same time. Exploring a method for efficient and simultaneous removal of multiple organic micropollutants in leachate is of great significance for controlling the environmental risks of organic micropollutants in leachate. Relevant studies have shown that leachate contains a variety of organic micropollutants, including drugs, personal care products and cosmetics. The organic micropollutants contained in the leachate infiltrate into the soil and water bodies through different pathways, which will seriously threaten the ecological environment and human health.

[0003] Advanced oxidation technology (AOPs) is a known efficient method for degrading toxic, biodegradable and persistent organic micropollutants. Its basic principle is to use the strong oxidizing free radicals generated by oxidants to oxidize organic micropollutants into small molecules or even mineralize them into CO 2 and H 2 O. As a disinfectant and oxidant, ozone can effectively disinfect, sterilize, and remove organic pollutants in water bodies, etc., and has attracted more and more attention. Ozone has strong oxidizing properties and does not have the problem of secondary pollution. It has been widely used in the removal of organic micropollutants in water bodies. However, the cost of directly introducing ozone into the water body is too high, and catalysts need to be added to promote ozone decomposition to produce more active substances. Conventional activation methods mainly include light (ultraviolet), catalysts (transition metal ions, metal oxides, etc.) and electric field activation. However, light or electric field activation has the disadvantages of poor light transmittance and high energy consumption, and metal-based catalysts have the problems of easy leaching of metals and low reusability. However, using sludge biochar as a catalyst not only realizes the resource utilization of sludge and reduces the preparation cost, but also meets the requirements of resource utilization, reduction, and harmlessness of solid waste.

[0004] With the continuous increase in the production of sludge in sewage treatment plants and residual sludge in different industries and industrial wastewater treatment plants, sludge treatment and disposal has become a bottleneck problem that restricts the further improvement of quality and efficiency of sewage treatment plants or different industries and industrial wastewater treatment plants. At present, common sludge treatment methods mainly include drying incineration, anaerobic digestion, aerobic composting, etc.; disposal methods include landfill, incineration, land use and building material utilization, etc., but studies have shown that the above treatment and disposal methods will not only cause secondary pollution to the environment to varying degrees, but also increase energy consumption, and at the same time pose a huge potential threat to human health. The use of sludge to prepare biochar catalyst can not only solve the problem of solid waste disposal, but also can be further reused for sewage treatment. The sludge biochar after high-temperature pyrolysis is a highly aromatic, porous carbon-based material with a large specific surface area. Its surface contains rich oxygen-containing functional groups, etc. In addition, the sludge contains rich metals and trace elements, which are beneficial to enhance the catalytic activation performance of sludge biochar to ozone. Traditional advanced oxidation technology is greatly affected by the background matrix of the water body, while the SDBC / O constructed in the present invention 3 The system has a strong anti-interference ability to the background matrix of water bodies, and can generate multiple active substances (ROS) and non-free radicals to synergistically degrade organic micropollutants in the leachate, so as to achieve the purpose of efficiently removing organic micropollutants in water bodies. Summary of the invention

[0005] The problem to be solved by the present invention is: based on the concept of "using waste to treat waste", the resource utilization of sludge is realized; on this basis, sludge biochar is used to activate ozone to achieve deep removal of organic micropollutants in leachate.

[0006] In order to solve the above problems, the present invention provides a method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone, which is characterized by comprising the following steps:

[0007] Step 1: Let the sludge stand until the mud and water are separated, pour out the supernatant, centrifuge the sludge and dry it to constant weight; grind the dried sludge and place it in a tubular furnace for pyrolysis under an inert gas atmosphere; wash the pyrolyzed sludge with deionized water and vacuum dry it to obtain sludge biochar.

[0008] Step 2: Add the sludge biochar obtained in step 1 and introduce ozone into the secondary effluent of the landfill leachate at room temperature and pressure, and continue the reaction for a certain period of time to achieve efficient removal of organic micropollutants.

[0009] Preferably, the sludge in step 1 is raw sludge, secondary sedimentation tank sludge, excess sludge from a sewage treatment plant, or any one of excess sludge from different industries or industrial wastewater treatment plants.

[0010] Preferably, the temperature of the sludge drying in step 1 is 80-110°C; the specific conditions of the pyrolysis are: first ventilate with inert gas for 10-30 minutes to ensure the inert gas atmosphere in the tube furnace, then increase the temperature from room temperature to 400-800°C at a heating rate of 5-10°C / min, and the pyrolysis time is 1-3 hours. The obtained sludge and sludge biochar are dried and ground and sieved.

[0011] Preferably, in step 2, the mass ratio of the dosage of sludge biochar to the reaction concentration of ozone is controlled at 3000-6000.

[0012] Preferably, the treatment conditions for the organic micropollutants in step 2 are neutral or alkaline conditions.

[0013] Preferably, the stirring reaction time in step 2 is 0.5 to 3 hours.

[0014] Technical principle of the present invention:

[0015] The present invention uses sludge to prepare biochar materials, which can not only solve the problem of solid waste disposal, but also can be further reused for sewage treatment. The sludge biochar after high-temperature pyrolysis is a highly aromatic, porous carbon-based material with a large specific surface area. Its surface contains abundant oxygen-containing functional groups, etc. In addition, the sludge contains abundant metals and trace elements, which are beneficial to enhance the catalytic activation performance of sludge biochar on ozone. Therefore, the activated SDBC / O 3 The system can effectively remove organic micropollutants from leachate.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The method of the present invention realizes resource utilization of sewage treatment plant sludge and surplus sludge from different industries and industrial wastewater treatment plants, and at the same time, uses ozone as an oxidant without secondary pollution problem to achieve the purpose of efficiently removing organic micropollutants in leachate.

[0018] 2. The material cost of the present invention is low, which can solve the problem of sludge disposal and realize resource recycling, and meet the requirements of resource utilization, reduction and harmlessness of solid waste.

[0019] 3. The present invention uses ozone as an oxidant, which has strong oxidizing properties, is produced and used immediately, does not require transportation and storage, has no safety hazards, and does not have secondary pollution problems, to deeply remove organic micropollutants in the leachate, and has strong application advantages in actual engineering.

[0020] 4. Unlike conventional advanced oxidation technologies, the present invention can efficiently remove organic micropollutants in leachate under neutral or alkaline pH conditions, which is conducive to application in actual wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The removal of sulfamethoxazole, carbamazepine and ciprofloxacin by 1.6 g / L sludge biochar and 0.3 mg / L ozone and their combination;

[0022] Figure 2 The figure shows the removal of sulfamethoxazole, carbamazepine and ciprofloxacin by combining 1.6 g / L sludge biochar and 0.3 mg / L ozone under different pH systems. DETAILED DESCRIPTION

[0023] In order to make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0024] Example 1

[0025] A method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone

[0026] This embodiment provides a method for preparing biochar by high-temperature pyrolysis of excess sludge. The sludge may be original sludge, secondary sedimentation tank sludge, excess sludge from a sewage treatment plant, or excess sludge from different industries or industrial wastewater treatment plants. In this embodiment, the secondary sedimentation tank sludge from a sewage treatment plant is taken as an example. The method comprises the following steps:

[0027] The sludge was allowed to stand until the mud and water were separated, the supernatant was poured out, the sludge was centrifuged and dried at 105°C to constant weight, the dried sludge was ground and placed in a tubular furnace for pyrolysis in a nitrogen atmosphere at a temperature of 800°C for 2h and a heating rate of 10°C / min. The pyrolyzed sludge was washed with deionized water and vacuum dried at 60°C to obtain sludge biochar, which was finally ground and passed through a 100-mesh sieve for later use.

[0028] Example 2

[0029] This embodiment provides a method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone, wherein sulfonamide antibiotic sulfamethoxazole, anti-epileptic drug carbamazepine and quinolone antibiotic ciprofloxacin are selected as target pollutants, and the specific steps include:

[0030] 60 μmol / L sulfonamide antibiotic sulfamethoxazole, anti-epileptic drug carbamazepine and quinolone antibiotic ciprofloxacin were added to the three portions of leachate (pH = 7.8), and 0.3 mg / L 3 、1.6g / L SDBC、0.3mg / LO 3and 1.6 g / L SDBC, placed in a magnetic stirrer for reaction, and samples were taken at 0, 1, 2, 3, 5, 10, 20, and 30 min for HPLC to determine the degradation of organic micropollutants. The combination of sludge biochar and ozone significantly accelerated the degradation rate of organic micropollutants in the leachate. The removal rate of the three organic micropollutants was more than 90% within 30 min, which was significantly better than the use of ozone and sludge biochar alone. The specific removal effect of organic micropollutants is as follows Figure 1 shown.

[0031] Example 3

[0032] This embodiment provides a method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone, wherein sulfonamide antibiotic sulfamethoxazole, anti-epileptic drug carbamazepine and quinolone antibiotic ciprofloxacin are selected as target pollutants, and the specific steps include:

[0033] 60 μmol / L sulfonamide antibiotic sulfamethoxazole, antiepileptic drug carbamazepine and quinolone antibiotic ciprofloxacin were added to 4 portions of filtrate (pH = 3, 5, 7.8, 9) respectively, and 1 mmol / L H 2 SO 4 and NaOH to adjust the solution pH to 3, 5, 9 (without pH adjustment, the pH of the filtrate is 7.8), and then add 0.3 mg / LO 3 and 1.6 g / L SDBC, placed in a magnetic stirrer for reaction, and samples were taken at 0, 1, 2, 3, 5, 10, 20, and 30 min for HPLC to determine the degradation of organic micropollutants. As the pH value of the solution increased from 3 to 9, the removal rates of the three organic micropollutants by the sludge biochar / ozone system were significantly improved. Neutral or alkaline conditions were more suitable for ozone oxidation to remove organic micropollutants, and the removal rate reached more than 90%. The specific removal effect of organic micropollutants is as follows Figure 2 shown.

Claims

1. A method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone, characterized in that: The following steps are involved: Step 1: Let the sludge stand until the mud and water are separated, pour out the supernatant, centrifuge the sludge and dry it to constant weight; grind the dried sludge and place it in a tubular furnace for pyrolysis under an inert gas atmosphere; wash the pyrolyzed sludge with deionized water and vacuum dry it to obtain sludge biochar. Step 2: Add sludge biochar and introduce ozone into the secondary effluent of the landfill leachate at normal temperature and pressure. Continue the reaction for a certain period of time to achieve efficient removal of organic micropollutants.

2. The method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone according to claim 1, characterized in that: The sludge in step 1 is any one of the original sludge, secondary sedimentation tank sludge, and residual sludge from a sewage treatment plant, or residual sludge from different industries or industrial wastewater treatment plants.

3. The method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone as claimed in claim 1, characterized in that: The temperature of the sludge drying in step 1 is 80-110°C; the specific conditions of the pyrolysis are: first ventilate with inert gas for 10-30 minutes to ensure the inert gas atmosphere in the tube furnace, then increase the temperature from room temperature to 400-800°C at a heating rate of 5-10°C / min, and the pyrolysis time is 1-3 hours. The obtained sludge and sludge biochar are dried and ground and sieved.

4. The method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone as claimed in claim 1, characterized in that: In the step 2, the mass ratio of the dosage of the sludge biochar to the reaction concentration of ozone is controlled at 3000-6000.

5. The method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone as claimed in claim 1, characterized in that: The treatment conditions for the organic micropollutants in step 2 are neutral or alkaline conditions.

6. The method for deep treatment of organic micropollutants in leachate by coupling sludge biochar with ozone as claimed in claim 1, characterized in that: The stirring reaction time in step 2 is 0.5 to 3 hours.

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