Method for simultaneous denitrification and phosphorus removal using waste adsorbent

Abstract

The application discloses a method for simultaneously denitrifying and removing phosphorus by using waste adsorbent, which comprises the following steps: S1, waste adsorbent pretreatment; S2, sewage treatment; the waste adsorbent serves as an electron donor to provide necessary energy for sulfur autotrophic denitrifying bacteria to drive a denitrification reaction, and the reaction reduces nitrate in water into nitrogen; meanwhile, the waste adsorbent can efficiently adsorb dissolved phosphorus in water, so that the nitrogen and phosphorus are simultaneously removed.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a method for simultaneous denitrification and phosphorus removal using waste adsorbents. Background Technology

[0002] In the field of eutrophication control research, nitrogen and phosphorus are considered the main pollutants. Traditional water treatment technologies typically require two separate steps: denitrification and phosphorus removal. Denitrification involves using microorganisms to reduce nitrates in the water to nitrogen gas, thus removing nitrogen. Phosphorus removal, on the other hand, relies on chemical or biological methods to reduce phosphorus concentration by fixing or absorbing it from the water. However, this step-by-step approach not only increases the complexity of the process but also leads to higher treatment costs.

[0003] Currently, there are many types of sulfur-autotrophic denitrification packing materials on the market. These packing materials utilize sulfur as an electron donor to remove nitrogen from water through microbial action. However, most of these packing materials lack the ability to simultaneously remove phosphorus. In some research attempts, researchers have tried to achieve phosphorus removal by adding specific chemical reagents or adsorbent materials, but this method often requires additional equipment and operational steps, which not only increases treatment costs but may also introduce new environmental risks.

[0004] To address the aforementioned issues, if materials with phosphorus removal capabilities can be utilized, leveraging their chemical and biological functions to effectively adsorb and remove phosphorus while removing nitrogen from water, the water treatment process can be significantly simplified, treatment costs reduced, and treatment efficiency improved. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for simultaneous denitrification and phosphorus removal using waste adsorbents.

[0006] A method for simultaneous denitrification and phosphorus removal using waste adsorbent includes the following steps:

[0007] S1. Pretreatment of waste adsorbent;

[0008] S1-1. Take the waste adsorbent, wherein the sulfur content and iron content in the waste adsorbent are both greater than or equal to 5%; wash the waste adsorbent with deionized water until the deionized water is clear, and then dry the washed waste adsorbent once.

[0009] S1-2. According to the solid-liquid ratio of 1g:5ml, the waste adsorbent after one drying is placed in an acid solution with a mass concentration of 3% for 3-6 hours.

[0010] S1-3. Take out the soaked waste adsorbent, then wash the waste adsorbent again with deionized water until the pH value of the washed deionized water is 6-8, and then perform secondary drying.

[0011] S1-4. The waste adsorbent after secondary drying is subjected to heat treatment. The heat treatment is as follows: the waste adsorbent after secondary drying is heated to 300-500°C under oxygen-free conditions and kept at that temperature for 3-5 hours, which completes the pretreatment.

[0012] S2, Wastewater Treatment

[0013] Sulfur autotrophic denitrification packing material and pretreated waste adsorbent of S1 are mixed evenly at a mass ratio of 1-4:6-9 to obtain a mixture. This mixture is added to a reactor for water treatment as denitrification packing material. The reactor has an anaerobic zone, a biofilm zone, and a clear water zone arranged sequentially from the reactor inlet to the reactor outlet. The denitrification packing material is located in the anaerobic zone and the biofilm zone of the reactor. The reactor is started, and anaerobic sludge accounting for 50-55% of the reactor volume is taken and evenly poured into the reactor from the reactor inlet to form a biofilm. After the biofilm formation is completed, wastewater is continuously introduced into the reactor. The wastewater stays in the reactor for 7-9 hours.

[0014] Explanation: The above method can treat and reuse waste adsorbents. These waste adsorbents typically have high iron and sulfur content. Utilizing the properties of these elements, phosphorus can be removed from wastewater. These waste adsorbents can promote denitrification in wastewater treatment, thereby improving the nitrogen removal efficiency in the water. Furthermore, research has shown that the reactor used in wastewater treatment according to the method of this invention performs excellently in nitrogen and phosphorus removal, with significantly improved nitrogen and phosphorus removal efficiency, meeting national emission standards and environmental protection requirements.

[0015] Furthermore, the drying method described in S1-1 is natural air drying or constant temperature drying at 20-35°C until completely dry.

[0016] Furthermore, the secondary drying method described in S1-3 involves drying at 80°C for 5–7 hours.

[0017] Explanation: By setting the two different drying temperatures, the first drying process removes surface and shallow impurities, preventing the adsorbent from being damaged by excessive temperature. The second drying process, which involves acid treatment, can more effectively remove moisture and deep impurities from the adsorbent, thereby improving the regeneration efficiency of the adsorbent. This results in the waste adsorbent having better adsorption performance and higher treatment capacity, enabling it to more effectively remove harmful substances from wastewater.

[0018] Furthermore, the acid solution is either dilute sulfuric acid or dilute hydrochloric acid.

[0019] Note: By treating the waste adsorbent with the above-mentioned acid solution, it is possible to achieve the desired acidity under acidic conditions. + H interacts with other functional groups on the adsorbent + The presence of these substances replaces heavy metal ions, thereby achieving the purpose of adsorbent regeneration and improving the efficiency of adsorbent use.

[0020] Furthermore, the anaerobic sludge is obtained from the denitrification tank.

[0021] Note: Since biological treatment systems typically include denitrification tanks, where denitrifying bacteria utilize organic matter for denitrification, simultaneously forming anaerobic sludge. This sludge is rich in denitrifying bacteria and can therefore be obtained from the denitrification tank for use in other anaerobic treatment processes or as bio-fertilizer. Therefore, the anaerobic sludge from the denitrification tank is directly used for water treatment here.

[0022] Furthermore, the waste adsorbent is any one of waste landfill gas desulfurization adsorbent, natural mineral adsorbent, or synthetic adsorbent.

[0023] Note: The above-mentioned waste adsorbents can be used to achieve resource reuse and reduce waste emissions. At the same time, these waste adsorbents usually have abundant microporous structures and specific surface functional groups, and have low source costs and wide application range, showing broad application prospects.

[0024] Furthermore, the microbial content in the anaerobic sludge is 60-70%.

[0025] Note: Using anaerobic sludge with the above-mentioned microbial content can improve wastewater treatment efficiency, reduce sludge production, promote the recovery and utilization of bioenergy, and enhance the system's resistance to shock loads.

[0026] Furthermore, while starting the reactor, a DC voltage of 0.5 to 0.8V is applied to the anaerobic zone of the reactor, and a DC voltage of 0.9 to 1.2V is applied to the biofilm zone of the reactor.

[0027] Explanation: By applying the voltage mentioned above, denitrification and electrochemical phosphorus removal can be combined, and the waste adsorbent packing can enhance the attachment and growth of microorganisms, achieving a synergistic effect between the two and improving the overall nitrogen and phosphorus removal efficiency. In the denitrification stage, reducing the voltage can be suitable for the survival of microorganisms and promote the efficiency of denitrification. In the phosphorus removal stage, increasing the voltage can further improve the phosphorus removal efficiency.

[0028] Further, in S1-4, before heat treatment, the waste adsorbent is subjected to plasma treatment. The plasma treatment method is as follows: take titanate coupling agent and waste adsorbent with a mass concentration of 10-15% according to the ratio of 1-3 ml: 10 g, spray the titanate coupling agent on the surface of the waste adsorbent, let it stand for 10-20 min, and then use a plasma surface treatment machine to apply plasma irradiation at a frequency of 12-14 MHz to the waste adsorbent in a nitrogen atmosphere for 15-30 min, and the plasma treatment is completed.

[0029] Note: In the above methods, spraying with titanate coupling agents enhances the interfacial bonding between the waste adsorbent and subsequent treatment materials or coatings, and improves the surface properties of the waste adsorbent. Simultaneously, plasma surface treatment enhances the chemical bonding on the surface of the waste adsorbent, improving its stability and durability. Plasma treatment also improves the dispersibility and wettability of the titanate coupling agent on the adsorbent surface, allowing for a more uniform coverage and increased adsorption efficiency and capacity. Applying high-frequency plasma treatment to the waste adsorbent under a nitrogen atmosphere promotes the formation of a more stable surface structure, further improving its adsorption performance and durability, enabling it to more efficiently adsorb pollutants in water while increasing adsorption capacity.

[0030] Furthermore, the wastewater mentioned in S2 is wastewater to be treated:

[0031] Before the wastewater is introduced into the reactor, the theoretical value of the sulfur autotrophic denitrification alkalinity required for the wastewater needs to be determined. The method for determining the theoretical value of the sulfur autotrophic denitrification alkalinity required for the wastewater is as follows: obtain the nitrate nitrogen content in the wastewater, and then multiply each g of nitrate nitrogen by 3.9 to obtain the theoretical value of the sulfur autotrophic denitrification alkalinity required for the wastewater.

[0032] The alkalinity of the wastewater is then tested. If the alkalinity of the wastewater is less than the theoretical value required for sulfur autotrophic denitrification, an alkaline substance is added to adjust the alkalinity of the wastewater to be greater than or equal to the theoretical value required for sulfur autotrophic denitrification. If the alkalinity of the wastewater is greater than or equal to the theoretical value required for sulfur autotrophic denitrification, no adjustment is required. The theoretical value required for sulfur autotrophic denitrification and the alkalinity of the wastewater are both expressed in mg(CaCO3) / L.

[0033] Note: The above method can be used to determine whether the alkalinity of wastewater needs to be adjusted, which is beneficial for the denitrification treatment of wastewater.

[0034] The beneficial effects of this invention are:

[0035] This invention provides a method for water treatment using waste adsorbent, aiming to achieve simultaneous denitrification and phosphorus removal processes in a single reactor. By setting the ratio of waste adsorbent to sulfur autotrophic denitrification packing, optimal simultaneous denitrification and phosphorus removal can be achieved for the effluent of a membrane bioreactor (MBR), thereby simplifying the water treatment process and reducing treatment costs. The waste adsorbent acts as an electron donor, providing the necessary energy for sulfur autotrophic denitrifying bacteria to drive the denitrification reaction, which reduces nitrates in the water to nitrogen. Simultaneously, the iron element contained in the adsorbent can efficiently adsorb dissolved phosphorus in the water, thus achieving simultaneous removal of nitrogen and phosphorus. Sulfotrophic microorganisms can use reduced sulfur (such as sulfides) as an electron donor to obtain energy. After obtaining sufficient energy and electrons, sulfur autotrophic denitrifying microorganisms will use these electrons to reduce nitrates as electron acceptors, achieving the key step of denitrification. Attached Figure Description

[0036] Figure 1 This is a scanning electron microscope image of the waste adsorbent S1 before treatment according to an embodiment of the present invention;

[0037] Figure 2 This is a scanning electron microscope image of the waste adsorbent S1 after treatment according to an embodiment of the present invention;

[0038] Figure 3 This invention describes the nitrogen and phosphorus removal performance of wastewater under different packing ratios in various embodiments.

[0039] Figure 4 This is a photograph of the waste adsorbent from an embodiment of the present invention. Detailed Implementation

[0040] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0041] Among the sulfur-autotrophic denitrification packing materials currently available on the market, none possess a combined simultaneous phosphorus removal function. According to existing technical literature, these sulfur-autotrophic denitrification packing materials are primarily used to remove nitrogen from water; however, they cannot remove phosphorus simultaneously. This limitation leads to the accumulation of phosphorus in the water, thus affecting water purity. Furthermore, traditional standalone phosphorus removal processes often require additional chemical reagents or adsorption materials, which not only increases the economic cost of water treatment but also makes the operation more complex and cumbersome.

[0042] Currently, the main limitations faced by denitrification and phosphorus removal technologies include the following:

[0043] 1) The denitrification process requires a large amount of carbon source, which may be difficult to meet or costly under certain conditions; 2) Denitrification and phosphorus removal processes are usually completed in different treatment units, which requires a long residence time and results in large treatment facilities; 3) During denitrification, excessive release of nitrogen may occur, leading to sludge bulking; 4) During phosphorus removal, chemical phosphorus removal requires the use of chemical agents, which may bring additional treatment costs and potential secondary pollution problems, increasing costs and operational complexity; 5) Among the sulfur autotrophic denitrification packing products currently on the market, no varieties with composite simultaneous phosphorus removal function have been found, which cannot remove phosphorus simultaneously, leading to the accumulation of phosphorus in the water and affecting the quality of the treated effluent.

[0044] To address the shortcomings of existing technologies, this study proposes an innovative integrated denitrification and phosphorus removal technology. This technology aims to achieve the following objectives: 1) By combining specific phosphorus absorption materials with sulfur-autotrophic denitrification packing, it achieves simultaneous removal of nitrogen and phosphorus, resulting in a dual purification effect; 2) It reduces dependence on external carbon sources, simplifies the treatment process, shortens the treatment cycle, and reduces the required facility volume, equipment investment, and operating costs, thus demonstrating significant economic benefits; 3) It reduces or eliminates the use of chemical agents, lowering the possibility of secondary pollution; 4) The technology also considers environmental protection and sustainability principles in waste recycling, ensuring that the negative environmental impact during wastewater treatment is minimized.

[0045] Therefore, this invention aims to provide an innovative packing material product and a method for treating wastewater using this product. This packing material can not only efficiently perform sulfur autotrophic denitrification reactions but also simultaneously remove phosphorus from water. This dual functionality significantly simplifies the water treatment process, reduces overall treatment costs, and substantially improves water treatment efficiency. This not only reduces environmental pollution but also brings economic benefits and technological advancements to the water treatment industry.

[0046] This invention, through the design of a pretreatment method, utilizes waste adsorbent in conjunction with sulfur autotrophic denitrification packing to simultaneously achieve denitrification and phosphorus removal, thus treating waste with waste, reducing the cost of wastewater denitrification and phosphorus removal, and improving treatment efficiency.

[0047] This implementation scheme can be used for denitrification and phosphorus removal treatment of municipal sewage, high ammonia nitrogen wastewater (such as landfill leachate) or industrial wastewater. That is, the sewage to be treated in the scheme can be any of the above. Specifically, in the following Example 1, the MBR effluent (secondary treated effluent after membrane bioreactor treatment) in the municipal sewage treatment process is treated. That is, the sewage to be treated referred to in the following Example 1 is the MBR effluent in the municipal sewage treatment process.

[0048] Example 1: A method for simultaneous denitrification and phosphorus removal using waste adsorbent, comprising the following steps:

[0049] S1. Pretreatment of waste adsorbent;

[0050] The waste adsorbent used in this invention is a waste landfill gas desulfurization adsorbent, which is taken from a landfill gas purification and treatment station in a certain place.

[0051] Its main elemental composition and main components are shown in Tables 1 and 2.

[0052] Table 1. Main elemental composition of waste adsorbent

[0053] Quality percentage (%) 9.54 37.95 0.42 0.54 8.61 24.53 0.49 17.92

[0054] S1-1. Take the waste adsorbent and wash it with deionized water until the deionized water is clear. Then, dry the washed waste adsorbent once. The method of drying once is to air dry it naturally until it is completely dry.

[0055] S1-2. According to the solid-liquid ratio of 1g:5ml, the waste adsorbent after one drying is placed in an acid solution with a mass concentration of 3% and soaked for 3-6 hours (in an acid-resistant reaction vessel, such as a glass container); the acid solution is dilute sulfuric acid.

[0056] S1-3. Remove the soaked waste adsorbent, then wash the waste adsorbent again with deionized water until the pH of the washed deionized water is 7, and then perform secondary drying; the secondary drying method is to dry at 80°C for 6 hours.

[0057] S1-4. The waste adsorbent after secondary drying is subjected to heat treatment. The heat treatment is as follows: the waste adsorbent after secondary drying is heated to 400°C under oxygen-free conditions and kept at that temperature for 4 hours, which means the pretreatment is completed.

[0058] S2, Wastewater Treatment

[0059] Sulfur autotrophic denitrification packing material and pretreated waste adsorbent of S1 were mixed uniformly at a mass ratio of 1:9 to obtain a mixture. This mixture was then added to a reactor (column continuous flow reactor) as denitrification packing material for water treatment. The reactor, from inlet to outlet, was sequentially divided into an anaerobic zone, a biofilm zone, and a clear water zone. The denitrification packing material was located in both the anaerobic and biofilm zones. The reactor was started, and anaerobic sludge, occupying 52% of the reactor volume, was uniformly poured into the reactor through the inlet to form a biofilm. After biofilm formation, wastewater was continuously introduced into the reactor, with a residence time of 8 hours. The anaerobic sludge was obtained from the denitrification tank, and its microbial content was 65%.

[0060] The wastewater mentioned is wastewater to be treated;

[0061] Before the wastewater is introduced into the reactor, the theoretical value of the sulfur autotrophic denitrification alkalinity required for the wastewater needs to be determined. The method for determining the theoretical value of the sulfur autotrophic denitrification alkalinity required for the wastewater is as follows: obtain the nitrate nitrogen content in the wastewater, and then multiply each g of nitrate nitrogen by 3.9 to obtain the theoretical value of the sulfur autotrophic denitrification alkalinity required for the wastewater.

[0062] The alkalinity of the wastewater is then tested. If the alkalinity of the wastewater is lower than the theoretical value required for sulfur autotrophic denitrification, an alkaline substance (calcium hydroxide in this embodiment) is added to adjust the alkalinity of the wastewater to be greater than or equal to the theoretical value required for sulfur autotrophic denitrification. If the alkalinity of the wastewater is greater than or equal to the theoretical value required for sulfur autotrophic denitrification, no adjustment is required. The theoretical value required for sulfur autotrophic denitrification and the alkalinity of the wastewater are both expressed in mg(CaCO3) / L.

[0063] The reactor operates as follows: Wastewater first enters the anaerobic zone, where denitrifying bacteria use organic matter as electron donors to reduce nitrates or nitrites to nitrogen gas, thus removing nitrogen. Subsequently, the wastewater enters the biofilm zone, where microorganisms attached to the packing material degrade and purify the organic matter in the wastewater. The treated wastewater is then discharged from the reactor, achieving the goal of water purification.

[0064] Example 2: The difference from the example is that the mass ratio of the waste adsorbent to the sulfur autotrophic packing material in the reactor is 2:8.

[0065] Example 3: The difference from the example is that the mass ratio of the waste adsorbent to the sulfur autotrophic packing material in the reactor is 3:7.

[0066] Example 4: The difference from the example is that the mass ratio of the waste adsorbent to the sulfur autotrophic packing material in the reactor is 4:6.

[0067] I. To test the water treatment effect under different packing ratios, the following experiments were conducted on Examples 1-4:

[0068] 1) Scanning electron microscopy analysis of untreated waste adsorbent and waste adsorbent treated with S1, as follows: Figure 1 , Figure 2 As shown; characterization analysis revealed its true density to be 2.5444 g / cm³. 3 The bulk density is 0.0034 g / cm³. 3 .

[0069] 2) If the reactor is considered to have started up successfully after 7 days of continuous operation and the nitrate nitrogen concentration in the effluent remains stable, the EBCT is shortened to 4 hours. Samples are collected from the inlet and outlet water of the device and from the effluent at different packing heights. The concentrations of nitrate nitrogen and nitrite nitrogen are measured after the water samples are filtered through a 0.45μm filter membrane. The total phosphorus concentration is measured from the unfiltered water samples.

[0070] The experimental results are as follows:

[0071] Sample test result analysis

[0072] The effects of different packing mass ratios on the nitrate removal efficiency and nitrite concentration in MBR effluent are as follows: Figure 3 As shown in a&b. The results show that the effluent nitrate nitrogen levels of the reactors (Examples 1, 2, 3, and 4) with different packing ratios were all low, indicating good denitrification effects. The reactor with a packing ratio of 1:9 showed the best nitrate nitrogen removal effect. However, the effluent nitrite nitrogen levels were higher when the packing ratios were 2:8, 3:7, and 4:6 (Examples 2, 3, and 4). Backwashing of the reactors was performed on the 2nd and 16th days of the experiment. After backwashing, the reactors needed time to recover their denitrification performance. The higher the packing ratio of the spent adsorbent, the longer the recovery time and the higher the effluent nitrite nitrogen concentration. The effects of different packing ratios on the phosphorus removal effect and the phosphorus removal performance along the reactor flow path are shown in the figures below. Figure 3 As shown in c&d. The results show that the higher the mass ratio of the spent adsorbent, the lower the total phosphorus concentration in the reactor effluent, and the better the phosphorus removal effect. This is because the main component of the spent adsorbent is iron salt. The higher the adsorbent filling ratio, the more iron salt dissolves, the stronger the adsorption capacity for phosphorus-containing compounds, and the better the phosphorus removal effect of the reactor.

[0073] The results above demonstrate that the combined use of sulfur-autotrophic denitrification packing material and spent adsorbent can achieve simultaneous nitrogen and phosphorus removal in MBR effluent. A mass ratio of 9:1 for the sulfur-autotrophic denitrification packing material and spent adsorbent achieves a relatively ideal nitrogen removal effect, while the phosphorus removal performance also meets the discharge requirements of standard GB 16889.

[0074] Example 5: This example differs from Example 1 in that the time parameters in S1 are different. In S1-2, the dried waste adsorbent is soaked in an acid solution for 3 hours; in S1-3, it is dried for 7 hours; and in S1-4, it is heated for 5 hours.

[0075] Example 6: This example differs from Example 1 in that the time parameters in S1 are different. In S1-2, the dried waste adsorbent is soaked in an acid solution for 6 hours; in S1-3, it is dried for 5 hours; and in S1-4, it is heated for 3 hours.

[0076] Example 7: This example differs from Example 1 in that in S1, the temperature is kept constant at 20°C until completely dry, and in S1-4, the temperature is heated to 300°C under oxygen-free conditions.

[0077] Example 8: This example differs from Example 1 in that in S1, the temperature is kept constant at 35°C until completely dry, and in S1-4, the temperature is heated to 500°C under oxygen-free conditions.

[0078] Example 9: The difference between this example and Example 1 is that S1-3 is used for washing until the pH value of the deionized water is 6.

[0079] Example 10: The difference between this example and Example 1 is that S1-3 is used for washing until the pH value of the deionized water is 8.

[0080] Example 11: The difference between this example and Example 1 is that the acid solution is dilute hydrochloric acid.

[0081] Example 12: The difference between this example and Example 1 is that the waste adsorbent is a natural mineral adsorbent.

[0082] Example 13: The difference between this example and Example 1 is that the waste adsorbent is a synthetic adsorbent.

[0083] Example 14: This example differs from Example 1 in that, in S2, the anaerobic sludge occupies 55% of the reactor volume; the wastewater has a residence time of 7 hours in the reactor; and the microbial content in the anaerobic sludge is 60%.

[0084] Example 15: This example differs from Example 1 in that, in S2, the anaerobic sludge occupies 50% of the reactor volume; the wastewater has a residence time of 9 hours in the reactor; and the microbial content in the anaerobic sludge is 70%.

[0085] Example 16: This example differs from Example 1 in that, at the same time as starting the reactor, a DC voltage of 0.6V is applied to the anaerobic zone of the reactor, and a DC voltage of 1.0V is applied to the biofilm zone of the reactor.

[0086] Example 17: This example differs from Example 16 in that, while starting the reactor, a DC voltage of 0.5V is applied to the anaerobic zone of the reactor, and a DC voltage of 0.9V is applied to the biofilm zone of the reactor.

[0087] Example 18: This example differs from Example 16 in that, at the same time as starting the reactor, a DC voltage of 0.8V is applied to the anaerobic zone of the reactor, and a DC voltage of 1.2V is applied to the biofilm zone of the reactor.

[0088] Example 19: This example differs from Example 16 in that, in S1-4, before heat treatment, the waste adsorbent is subjected to plasma treatment. The plasma treatment method is as follows: taking a 13% titanate coupling agent and the waste adsorbent at a ratio of 2ml:10g, spraying the titanate coupling agent onto the surface of the waste adsorbent, letting it stand for 15 minutes, and then using a plasma surface treatment machine (the plasma surface treatment machine used is the existing Tantec plasma surface treatment machine) to irradiate the waste adsorbent with a plasma frequency of 13MHz under a nitrogen atmosphere for 20 minutes, thus completing the plasma treatment.

[0089] Example 20: This example differs from Example 19 in that the plasma treatment method is as follows: A titanate coupling agent and waste adsorbent with a mass concentration of 10% are taken at a ratio of 1 ml: 10 g. The titanate coupling agent is sprayed onto the surface of the waste adsorbent. After standing for 10 minutes, a plasma surface treatment machine is used to irradiate the waste adsorbent with plasma at a frequency of 14 MHz under a nitrogen atmosphere for 30 minutes. The plasma treatment is then complete.

[0090] Example 21: The difference between this example and Example 19 is that the plasma treatment method is as follows: Take a 15% titanate coupling agent and waste adsorbent at a ratio of 3ml:10g, spray the titanate coupling agent onto the surface of the waste adsorbent, let it stand for 20 minutes, and then use a plasma surface treatment machine to apply plasma irradiation at a frequency of 12MHz to the waste adsorbent in a nitrogen atmosphere for 15 minutes. The plasma treatment is then completed.

[0091] II. The methods described in Examples 1 to 19 were executed respectively, and the results are as follows:

[0092] 1. Investigate the impact of different treatment methods on water treatment results;

[0093] Comparative Example 1: The difference from Example 1 is that only sulfur autotrophic denitrification packing material is used, and waste adsorbent is not used;

[0094] Comparative Example 2: The difference from Example 1 is that only the waste adsorbent was used, and the sulfur autotrophic denitrification packing was not used;

[0095] Comparative Example 3: Unlike Example 1, the waste adsorbent was not pretreated with S1.

[0096] Comparative Example 4: The difference from Example 1 is that anaerobic sludge from the riverbed was used for treatment;

[0097] Comparative Example 5: The difference from Example 16 is that a DC voltage of 0.9 to 1.2 V is applied to both the anaerobic zone and the biofilm zone in the reactor.

[0098] Table 1 shows the comparison of nitrate nitrogen and total phosphorus in the effluent from Examples 1, 2, 3, 15, 16, and Comparative Examples 1 to 4, which were operated according to the methods of these examples.

[0099] Table 1. Effects of different treatment methods on the experimental results of water treatment.

[0100] Example 1 87 55 Example 16 90 68 Example 19 94 71 Comparative Example 1 65 15 Comparative Example 2 60 46 Comparative Example 3 80 51 Comparative Example 4 75 47 Comparative Example 5 91 70

[0101] As shown in Table 1, comparing Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that the water treatment effect obtained by mixing the two types of packing materials used in Example 1 is better, especially compared with the removal of total phosphorus in Comparative Example 1. This may be because, in Comparative Example 1, the use of general packing materials can only remove nitrogen through denitrification, while existing packing materials cannot effectively remove phosphorus. This may be because phosphorus removal requires metal elements such as iron in the packing materials. These metal ions can react chemically with phosphate ions in wastewater to form precipitates that are insoluble in water. Furthermore, metal ions can exchange with other cations in the water, promoting phosphorus removal through ion exchange. In Comparative Example 2, only waste adsorbent was used. Although waste adsorbent has a good effect on phosphorus removal, its effect on denitrification nitrogen removal needs to be improved. Therefore, the method in Example 1 is preferred.

[0102] Comparing Example 1 and Comparative Example 3, it can be seen that, compared with Comparative Example 3 without pretreatment, Example 1 with pretreatment of the waste adsorbent has a better effect on nitrogen and phosphorus removal from wastewater. This may be because the pretreatment method can remove impurities such as metal oxides on the surface of the adsorbent, restore and improve the purity of the adsorbent, improve the surface properties of the adsorbent, and heat treatment can remove organic matter and moisture on the surface of the adsorbent, thereby improving the stability and adsorption capacity of the adsorbent.

[0103] Comparing Example 1 and Comparative Example 4, it can be seen that in Comparative Example 4, anaerobic sludge from the riverbed was used for water treatment. Compared with directly using a denitrification tank, the anaerobic sludge from the riverbed may contain more impurities and silt, which affects the wastewater treatment process and thus reduces the nitrogen and phosphorus removal efficiency.

[0104] Comparing Example 1 and Example 16, it can be seen that the denitrification and phosphorus removal effects are improved after applying voltage in Example 16. This may be because the voltage can combine denitrification with electrochemical phosphorus removal, and the waste adsorbent packing can enhance the attachment and growth of microorganisms, achieving a synergistic effect between the two and improving the overall denitrification and phosphorus removal efficiency.

[0105] Comparing Example 16 and Example 19, it can be seen that Example 19, based on Example 16, adds a surface treatment process for the waste adsorbent. According to the results in Table 1, the method in Example 19 has a good effect on nitrogen and phosphorus removal from wastewater. This may be because plasma surface treatment can promote the formation of a more stable surface structure, further improve its adsorption performance and durability, and enable it to adsorb pollutants in water more efficiently, while increasing the adsorption capacity.

[0106] 2. Investigate the effects of different treatment parameters on the experimental results of wastewater treatment;

[0107] Comparisons were made between Examples 1 and Examples 5-15, as shown in Table 2;

[0108] Table 2. Effects of different treatment parameters on wastewater treatment experimental results.

[0109]

[0110]

[0111] As can be seen from Table 2, comparing Examples 1, 5 and 6, and Examples 7 and 8, it can be found that the time and temperature parameters in Example 1 are preferred. This may be because the purpose of pretreatment is to improve the purity of the adsorbent and improve the surface properties of the adsorbent. If the temperature and time change accordingly, it may affect the performance state of the waste adsorbent surface and cause it to change accordingly. Among them, the parameters in Example 1 are preferred.

[0112] Comparing Examples 1, 9, and 10, it can be found that the pH value of the cleaned waste adsorbent in Example 1 has a certain impact on the water treatment results. This may be because the change in pH between the waste adsorbent and the wastewater may affect the adsorption and reaction of phosphorus atoms in the water during the water treatment process. Comparing Examples 1, 12, and 13, it can be found that the waste landfill gas desulfurization adsorbent in Example 1 is a preferred raw material. This may be because the waste landfill gas desulfurization adsorbent has a superior elemental composition compared to other adsorbents. Comparing Examples 1, 14, and 15, it can be found that the reactor treatment parameters in Example 1 are superior.

[0113] In summary, this invention provides a highly efficient, economical, and environmentally friendly technology for simultaneous denitrification and phosphorus removal. By optimizing the reactor's operating parameters and the ratio of packing materials, this invention not only improves treatment efficiency and reduces operating costs but also minimizes potential environmental impact. This technical solution has broad application prospects, particularly in municipal wastewater treatment and industrial wastewater treatment, and can provide strong technical support for achieving sustainable development.

[0114] Specifically, the embodiments of the present invention have the following characteristics:

[0115] (1) The packing material proposed in this invention exhibits excellent physicochemical stability and wide adaptability, making it suitable for diverse water treatment environments. A high proportion of waste adsorbent addition helps shorten the reactor recovery cycle and extend its service life, thereby reducing replacement frequency and maintenance costs.

[0116] (2) The present invention optimizes the operating parameters of the reactor, especially the EBCT (Effective Biocontact Time). When the waste adsorbent is used alone, the EBCT is set to 24 hours; while when the two are used in combination, the EBCT can be shortened to 4 hours to achieve the ideal nitrogen and phosphorus removal effect.

[0117] III. Experimental results of adjusting pH value;

[0118] To adapt to different influent water qualities and treatment requirements, the reactors can further improve nitrogen and phosphorus removal efficiency, ensuring the stability and safety of effluent quality. For example, three biofilm-based reactors were used in the experiment, named reactor 5, reactor 6, and reactor 7. The EBCT (Extended Effluent Tolerance Time) for each reactor was set to 4 hours. Wastewater was continuously introduced into the reactors until the effluent nitrate nitrogen concentration reached a stable level. Reactor 5 did not have its influent alkalinity adjusted.

[0119] The theoretical formula for calculating the alkalinity requirement for sulfur autotrophic denitrification is: 1.06NO3 - +1.11S+0.3CO2+0.785H2O→0.06C5H7O2N+0.5N2+1.11SO4 2- +1.16H + For example, according to this formula, the alkalinity consumption value for removing 1 mg of nitrate nitrogen through sulfur autotrophic denitrification is 3.9 mg (calculated as CaCO3). Experimental results show that the alkalinity of the wastewater itself is about 1200 mg / L (calculated as CaCO3), which is 400% of the theoretical alkalinity requirement for sulfur autotrophic denitrification. It can provide sufficient alkalinity for sulfur autotrophic denitrification to achieve the best nitrogen removal effect, so there is no need to adjust the alkalinity.

[0120] To demonstrate the effect of pH on the removal efficiency of total nitrogen and nitrate nitrogen, the influent alkalinity of reactors 6 and 7 was adjusted to 85% and 65% of the theoretical alkalinity requirements for sulfur autotrophic denitrification, respectively, using 50% dilute sulfuric acid. Samples of the influent and effluent from each reactor were collected and filtered through a 0.45 μm filter membrane to determine the nitrate nitrogen concentration. During the 20-day operating period, the total nitrogen and nitrate nitrogen removal rates remained above 90% and 95%, respectively. When the alkalinity was adjusted to 85% of the theoretical requirement, the total nitrogen removal rate decreased to approximately 70%, while the nitrate nitrogen removal rate remained above 95%, still exhibiting excellent denitrification performance. With a continuous decrease in alkalinity, the denitrification performance showed a downward trend. When the alkalinity was adjusted to 65% of the theoretical requirement, the total nitrogen removal rate decreased to approximately 60%, and the nitrate removal efficiency dropped below 90%, with the effluent nitrate nitrogen concentration between 6-12 mg / L.

[0121] The above experiments demonstrate that alkalinity adjustment is necessary. That is, when alkalinity is insufficient, the removal rates of total nitrogen and nitrate nitrogen are lower, while when the alkalinity meets the requirements of the examples, the removal rates of total nitrogen and nitrate nitrogen are better.

[0122] IV. Experimental results of biofilm formation start-up in a sulfur autotrophic denitrification reactor;

[0123] In the biofilm formation start-up stage of the continuous flow sulfur autotrophic reactor, anaerobic sludge is first uniformly poured into a columnar sulfur autotrophic denitrification reactor filled with packing material; then, wastewater is continuously introduced into the reactor, and the empty bed retention time (EBCT) is set to 6 hours, with the influent pH controlled between 8 and 9. Samples of the reactor influent and effluent are collected. The concentrations of nitrate nitrogen and nitrite nitrogen are measured after filtration through a 0.45 μm filter membrane. The empty bed retention time is determined by the following formula (1):

[0124]

[0125] In the formula, EBCT is the empty bed residence time, h; V is the packing volume, L; Q is the influent flow rate, L / h;

[0126] The results of the changes in nitrate and nitrite concentrations in the influent and effluent during the reactor biofilm formation and start-up process showed that the effluent nitrate concentration in each reactor gradually decreased and stabilized with the number of operating days, while the effluent nitrite concentration first increased and then decreased, maintaining a low concentration level. During the first four days after start-up, the effluent nitrate concentration in each reactor decreased rapidly, indicating rapid microbial growth. The nitrite concentration in each reactor peaked on the fourth day, reaching as high as 8.86 mg / L in reactor 3. This may be because the reactor had not yet successfully formed a biofilm and was in an unstable stage, with both the types and numbers of microorganisms growing rapidly, resulting in insufficient nitrite-reducing bacteria and incomplete denitrification. After the fourth day, the effluent nitrite concentration in each reactor began to decrease, reaching approximately 0 mg / L on the seventh day. At this point, the effluent nitrate concentration also tended to be 0 mg / L, indicating that the reactors had reached a stable state. On the tenth day, both the effluent nitrate and nitrite concentrations in each reactor were at low levels, indicating successful biofilm formation and allowing for subsequent experiments.

[0127] V. Experimental Results of Empty Bed Time (EBCT)

[0128] During the start-up phase, after successful biofilm formation in reactors 1, 2, 3, and 4, the effect of empty bed residence time (EBCT) on the sulfur autotrophic denitrification process was investigated. In the experiment, the EBCT of reactors 1, 2, 3, and 4 were set to 1, 2, 3, and 4 hours, respectively. The influent pH was controlled between 8 and 9. Hydraulic backwashing was performed when the effluent nitrate and nitrite concentrations significantly increased. Influent and effluent samples from each reactor were collected periodically during the experiment. After filtration through a 0.45 μm filter membrane, the concentrations of nitrate, nitrite, total nitrogen, and sulfate were measured.

[0129] The results showed that the concentrations of total nitrogen and nitrate nitrogen in the effluent decreased with the extension of the extracorporeal membrane oxygenation (EBCT). When the EBCT was 1 hour, the total nitrogen concentration in the effluent was generally higher than 40 mg / L, failing to meet the discharge limit in Table 2 of GB 16889, and a residual nitrate nitrogen concentration of 10-20 mg / L remained in the effluent. When the EBCT was 2 hours, after a backwash on the 6th day, the total nitrogen concentration in the effluent was lower than the discharge limit, remaining at 30-40 mg / L, and the nitrate nitrogen concentration also stabilized below 10 mg / L. When the EBCT was 3 hours and 4 hours, the total nitrogen concentration in the effluent remained below 30 mg / L, and the nitrate nitrogen concentration remained at a low level, below 5 mg / L, indicating a good denitrification effect. If the EBCT was too short, the autotrophic microorganisms in the reactor could not fully utilize the electron donors and nutrients, resulting in incomplete nitrate nitrogen removal. Sulfur autotrophic denitrification is mainly aimed at the removal of nitrate nitrogen. Therefore, the comparison shows that the changes in total nitrogen concentration and nitrate nitrogen concentration in the effluent of each reactor under the influence of EBCT are consistent, indicating that the reaction system has a strong correlation with the removal patterns of nitrate nitrogen and total nitrogen.

[0130] The effluent nitrite concentration decreases with increasing EBCT (Excessive Extended Cutoff Time); the shorter the EBCT, the more severe the nitrite residue. With an EBCT of 1 hour, the effluent nitrite concentration can reach as high as 26.43 mg / L. With an EBCT of 4 hours, the effluent nitrite concentration is at a low level, and it can be considered that no nitrite accumulation has occurred. During the denitrification reaction in the sulfur autotrophic denitrification filter, intermediate products such as nitrite are produced during the reduction of nitrate nitrogen to nitrogen gas. That is, the rate at which intermediate products such as nitrite are reduced to nitrogen gas is lower than the reduction rate of nitrate nitrogen. The accumulation of intermediate products such as nitrite inhibits nitrate removal.

[0131] The effluent sulfate concentration increases with the extension of the extracorporeal membrane oxygenation (EBCT) period; the longer the EBCT, the greater the sulfate production. With an EBCT of 4 hours, the effluent sulfate concentration can reach as high as 528 mg / L. The GB 16889 discharge standard does not specify requirements for effluent sulfate concentration. In the sulfur autotrophic denitrification process, elemental sulfur acts as an electron donor, being oxidized by microorganisms to ultimately form sulfate, while nitrate nitrogen in the water gains electrons and is converted into nitrogen gas. Therefore, the sulfate generated in this process reflects the nitrate nitrogen removal efficiency; the longer the EBCT, the better the nitrate nitrogen removal efficiency and the greater the sulfate production.

[0132] VI. Experimental Results of Hydraulic Backwashing Intensity

[0133] The backwash time (EBCT) of reactors 1, 2, 3, and 4 was set to 4 hours. MBR effluent was continuously fed into the reactors until the nitrate removal rate was below 70%, at which point the effect of backwash intensity was investigated. The backwash intensities for reactors 1, 2, 3, and 4 were set to 3 L / (m²·s), 6 L / (m²·s), 9 L / (m²·s), and 12 L / (m²·s), respectively. After backwashing, samples of the influent and effluent from each reactor were collected and filtered through a 0.45 μm filter membrane to determine the nitrate concentration. Higher backwash intensities resulted in more biofilm being washed away, leaving fewer microorganisms on the packing surface. At a backwash intensity of 3 L / (m²·s), the washing force was relatively weak, leaving many microorganisms on the packing surface and making the packing layer prone to re-clogging. At a backwash intensity of 12 L / (m²·s), the biofilm on the packing surface was sparser, removing more microorganisms and alleviating clogging.

Claims

1. A method for simultaneous denitrification and phosphorus removal using waste adsorbent, characterized in that, Includes the following steps: S1. Pretreatment of waste adsorbent; S1-1. Take the waste adsorbent, wherein the sulfur content and iron content in the waste adsorbent are both greater than or equal to 5%; wash the waste adsorbent with deionized water until the deionized water is clear, and then dry the washed waste adsorbent once. S1-2. According to the solid-liquid ratio of 1g:5ml, the waste adsorbent after one drying is placed in an acid solution with a mass concentration of 3% for 3-6 hours. S1-3. Take out the soaked waste adsorbent, then wash the waste adsorbent again with deionized water until the pH value of the washed deionized water is 6~8, and then perform secondary drying. The waste adsorbent is subjected to plasma treatment. The plasma treatment method is as follows: take titanate coupling agent and waste adsorbent with a mass concentration of 10-15% according to the ratio of 1-3 ml: 10 g, spray the titanate coupling agent on the surface of the waste adsorbent, let it stand for 10-20 min, and then use a plasma surface treatment machine to apply plasma irradiation of 12-14 MHz frequency to the waste adsorbent under a nitrogen atmosphere for 15-30 min. The plasma treatment is then completed. S1-4. The waste adsorbent is subjected to heat treatment, wherein the heat treatment is performed by heating the waste adsorbent to 300~500℃ under oxygen-free conditions and keeping it at that temperature for 3~5 hours, thus completing the pretreatment. S2, Wastewater Treatment Sulfur autotrophic denitrification packing material and pretreated waste adsorbent of S1 are mixed evenly at a mass ratio of 1~4:6~9 to obtain a mixture. This mixture is added to a reactor for water treatment as denitrification packing material. The reactor is divided into an anaerobic zone, a biofilm zone, and a clear water zone from the inlet to the outlet. The denitrification packing material is located in the anaerobic zone and the biofilm zone. The reactor is started, and anaerobic sludge accounting for 50~55% of the reactor volume is taken and evenly poured into the reactor from the inlet to form a biofilm. After the biofilm formation is completed, wastewater is continuously introduced into the reactor. The wastewater stays in the reactor for 7~9 hours. The wastewater in question is wastewater to be treated. Before the wastewater is introduced into the reactor, the theoretical value of the sulfur autotrophic denitrification alkalinity required for the wastewater needs to be determined. The method for determining the theoretical value of the sulfur autotrophic denitrification alkalinity required for the wastewater is as follows: obtain the nitrate nitrogen content in the wastewater, and then multiply each mg of nitrate nitrogen by a ratio of 3.9 to obtain the theoretical value of the sulfur autotrophic denitrification alkalinity required for the wastewater. The alkalinity of the wastewater is then tested. If the alkalinity of the wastewater is less than the theoretical value required for sulfur autotrophic denitrification, an alkaline substance is added to adjust the alkalinity of the wastewater to be greater than or equal to the theoretical value required for sulfur autotrophic denitrification. If the alkalinity of the wastewater is greater than or equal to the theoretical value required for sulfur autotrophic denitrification, no adjustment is required. The theoretical value required for sulfur autotrophic denitrification and the alkalinity of the wastewater are both expressed in mg (CaCO3) / L.

2. The method for simultaneous denitrification and phosphorus removal using waste adsorbent as described in claim 1, characterized in that, The drying method described in S1-1 is natural air drying or constant temperature at 20~35℃ until completely dry.

3. The method for simultaneous denitrification and phosphorus removal using waste adsorbent as described in claim 1, characterized in that, The secondary drying method described in S1-3 is to dry at 80℃ for 5~7 hours.

4. The method for simultaneous denitrification and phosphorus removal using waste adsorbent as described in claim 1, characterized in that, The acid solution is either dilute sulfuric acid or dilute hydrochloric acid.

5. The method for simultaneous denitrification and phosphorus removal using waste adsorbent as described in claim 1, characterized in that, The anaerobic sludge is obtained from the denitrification tank.

6. The method for simultaneous denitrification and phosphorus removal using waste adsorbent as described in claim 1, characterized in that, The waste adsorbent is a waste landfill gas desulfurization adsorbent.

7. The method for simultaneous denitrification and phosphorus removal using waste adsorbent as described in claim 1, characterized in that, The waste adsorbent is a natural mineral adsorbent or a synthetic adsorbent.

8. The method for simultaneous denitrification and phosphorus removal using waste adsorbent as described in claim 1, characterized in that, The microbial content in the anaerobic sludge is 60-70%.

9. The method for simultaneous denitrification and phosphorus removal using waste adsorbent as described in claim 1, characterized in that, Simultaneously with starting the reactor, a DC voltage of 0.5~0.8V is applied to the anaerobic zone of the reactor, and a DC voltage of 0.9~1.2V is applied to the biofilm zone of the reactor.

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