Method for synchronously denitrifying and dephosphorizing by using waste adsorbent

Abstract

The invention discloses a method for synchronously denitrifying and dephosphorizing by using a waste adsorbent. The method comprises the following steps: S1, pretreating the waste adsorbent; s2, sewage treatment; the waste adsorbent is used as an electron donor to provide necessary energy for sulfur autotrophic denitrifying bacteria to drive a denitrification reaction, and nitrate in a water body is reduced into nitrogen by the reaction; meanwhile, the waste adsorbent can efficiently adsorb soluble phosphorus in water, so that synchronous removal of nitrogen and phosphorus is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and specifically relates to a method for synchronous denitrification and phosphorus removal using waste adsorbents. Background Art

[0002] In the research field of controlling water eutrophication, nitrogen and phosphorus are considered the main pollutants. In traditional water treatment technologies, it is usually necessary to perform two independent steps of denitrification and phosphorus removal respectively to remove nitrogen and phosphorus. The denitrification process involves using microorganisms to reduce nitrates in water to nitrogen gas to achieve nitrogen removal; while the phosphorus removal process relies on chemical or biological means to reduce the concentration of phosphorus in water by fixing or adsorbing phosphorus. However, this step-by-step treatment strategy not only increases the complexity of the process flow but also leads to an increase in treatment costs.

[0003] Currently, there are a wide variety of sulfur autotrophic denitrification fillers on the market. These fillers use sulfur as an electron donor to achieve nitrogen removal in water through microbial action. However, most of these fillers lack the ability to synchronously remove phosphorus. In some research attempts, researchers have tried to achieve phosphorus removal by adding specific chemical reagents or adsorption materials, but this method often requires additional equipment and operating steps, which not only increases the treatment cost but may also bring new environmental risks.

[0004] To solve the above problems, if a material with phosphorus removal function can be used to effectively adsorb and remove phosphorus while removing nitrogen in water by exerting its chemical and biological functions, the water treatment process flow can be significantly simplified, the treatment cost can be reduced, and the treatment efficiency can be improved. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for synchronous denitrification and phosphorus removal using waste adsorbents.

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

[0007] S1. Pretreatment of waste adsorbents;

[0008] S1-1. Take waste adsorbents, wherein the sulfur content and iron content in the waste adsorbents are both greater than or equal to 5%; wash the waste adsorbents with deionized water until the deionized water after washing is clear, and then perform primary drying on the washed waste adsorbents;

[0009] S1-2. Place the waste adsorbents after primary drying in an acid solution with a mass concentration of 3% at a solid-liquid ratio of 1 g:5 ml and soak for 3 - 6 h;

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

[0011] S1-4. Heat-treat the waste adsorbent after the secondary drying. The heat treatment is: heat the waste adsorbent after the secondary drying to 300-500 °C under anaerobic conditions and keep it warm for 3-5 h, and the pretreatment is completed;

[0012] S2. Sewage treatment

[0013] Mix the sulfur autotrophic denitrification filler and the waste adsorbent pretreated in S1 evenly at a mass ratio of 1-4:6-9 to obtain a mixture. Add the mixture as a denitrification filler into a reactor for water treatment. From the inlet of the reactor to the outlet direction of the reactor, an anaerobic zone, a biofilm zone, and a clear water zone are successively arranged inside the reactor; the denitrification filler is located in the anaerobic zone and the biofilm zone of the reactor; start the reactor, take anaerobic sludge accounting for 50-55% of the volume of the reactor, and pour the anaerobic sludge evenly into the reactor from the inlet of the reactor for film hanging. After the film hanging is completed, then continuously introduce sewage into the reactor, and the residence time of the sewage in the reactor is 7-9 h.

[0014] Note: Through the above method, the waste adsorbent can be treated and reused. Usually, the iron content and sulfur content in these waste adsorbents are relatively high. Utilizing the characteristics exhibited by these elements, phosphorus in the sewage can be removed. Through these waste adsorbents, the denitrification for sewage treatment can be promoted, thereby improving the nitrogen removal effect in the water body. And through actual research, it is found that according to the method of the present invention for sewage treatment, the reactor performs excellently in nitrogen and phosphorus removal, and the removal efficiency of nitrogen and phosphorus is significantly improved, which can meet the national discharge standards and environmental protection requirements.

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

[0016] Further, the method of the secondary drying in S1-3 is drying at 80 °C for 5-7 h.

[0017] Note: Through the different settings of the above two drying temperatures, after the first drying removes the surface and shallow impurities, it can avoid damage to the adsorbent due to too high temperature. The second drying can more effectively remove the moisture and deep impurities inside the adsorbent after acid treatment, thereby improving the regeneration efficiency of the adsorbent; enabling the waste adsorbent to have better adsorption performance and higher treatment capacity, and can more effectively remove harmful substances in the wastewater.

[0018] Further, the acid solution is any one of dilute sulfuric acid and dilute hydrochloric acid.

[0019] Explanation: By treating the waste adsorbent with the above acid solution, under acidic conditions, H + acts with other functional groups on the adsorbent, and the presence of H + replaces heavy metal ions, thus achieving the purpose of adsorbent regeneration and improving the use efficiency of the adsorbent.

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

[0021] Explanation: Since in the biochemical treatment system, a denitrification tank is usually provided, and the denitrifying bacteria in the denitrification tank use organic matter for denitrification reaction and form anaerobic sludge at the same time. These sludges are rich in denitrifying bacteria, so they can be obtained from the denitrification tank and used for other anaerobic treatment processes or as biological fertilizers, etc. Therefore, the anaerobic sludge in the denitrification tank is directly taken for water treatment here.

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

[0023] Explanation: Using the above waste adsorbent can realize resource reuse, reduce waste discharge. At the same time, these waste adsorbents usually have a rich microporous structure and specific surface functional groups, and have a low source cost and a wide application range, with broad application prospects.

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

[0025] Explanation: Using anaerobic sludge with the above microbial content can improve the sewage treatment efficiency, reduce the sludge production, promote the recovery and utilization of bioenergy, and improve the shock resistance load capacity of the system.

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

[0027] Explanation: By applying the above voltage, denitrification can be combined with electrochemical phosphorus removal, and the waste adsorbent filler can enhance the attachment and growth of microorganisms, realizing the synergistic effect between the two and improving the overall nitrogen and phosphorus removal efficiency; in the denitrification stage, reducing the voltage is suitable for the survival of microorganisms and promotes the denitrification efficiency, and 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 a titanate coupling agent with a mass concentration of 10-15% and the waste adsorbent in a ratio of 1-3 ml: 10 g. Spray the titanate coupling agent on the surface of the waste adsorbent. After standing for 10-20 min, then use a plasma surface treatment machine to apply plasma irradiation with 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] Explanation: In the above method, through the spraying of the titanate coupling agent, the interfacial bonding force between the waste adsorbent and the subsequent treatment materials or coatings can be enhanced, and the surface properties of the waste adsorbent can be improved. At the same time, through plasma surface treatment, the chemical bonding effect on the surface of the waste adsorbent can be enhanced, its stability and durability can be improved. The plasma treatment can also improve the dispersibility and wettability of the titanate coupling agent on the surface of the adsorbent, so that the titanate coupling agent can cover the surface of the adsorbent more evenly, improving the adsorption efficiency and capacity. Applying high-frequency plasma treatment to the waste adsorbent in a nitrogen atmosphere can promote the formation of a more stable surface structure on its surface, further improving its adsorption performance and durability, enabling it to adsorb pollutants in water more efficiently and increasing the adsorption capacity at the same time.

[0030] Further, the sewage in S2 is sewage to be treated:

[0031] Before the sewage is introduced into the reactor, the theoretical value of the alkalinity demand for sulfur autotrophic denitrification of the sewage needs to be determined first. Among them, the method for the theoretical value of the alkalinity demand for sulfur autotrophic denitrification of sewage is: Obtain the content of nitrate nitrogen in the sewage, and then multiply each gram of nitrate nitrogen by 3.9 to obtain the theoretical value of the alkalinity demand for sulfur autotrophic denitrification of the sewage.

[0032] Then, detect the alkalinity of the sewage. When the alkalinity in the sewage is less than the theoretical value of the alkalinity demand for sulfur autotrophic denitrification, add an alkaline substance to adjust the alkalinity in the sewage to be greater than or equal to the theoretical value of the alkalinity demand for sulfur autotrophic denitrification. When the alkalinity in the sewage is greater than or equal to the theoretical value of the alkalinity demand for sulfur autotrophic denitrification, no adjustment is required. Among them, the above-mentioned theoretical value of the alkalinity demand for sulfur autotrophic denitrification and the alkalinity of the sewage are both in mg(CaCO 3 ) / L.

[0033] Explanation: Through the above method, it is possible to judge whether adjustment is needed according to the alkalinity of the sewage, which is beneficial to the denitrification treatment of the sewage.

[0034] The beneficial effects of the present invention are:

[0035] The present invention provides a method for water treatment using waste adsorbents, aiming to synchronize the denitrification and phosphorus removal processes in a single reactor. By setting the ratio of waste adsorbents to sulfur autotrophic denitrification fillers, it is possible to achieve the optimal simultaneous denitrification and phosphorus removal of the effluent from a membrane bioreactor (MBR), thereby simplifying the water treatment process flow and reducing the treatment cost. The waste adsorbent serves as an electron donor, providing the necessary energy for sulfur autotrophic denitrifying bacteria to drive the denitrification reaction, which reduces nitrate in the water body to nitrogen. At the same time, the iron element contained in the adsorbent can efficiently adsorb dissolved phosphorus in the water, thus achieving the simultaneous removal of nitrogen and phosphorus. Sulfur autotrophic microorganisms can use reduced sulfur (such as sulfide) as an electron donor to obtain energy. After obtaining sufficient energy and electrons, sulfur autotrophic denitrifying microorganisms will use these electrons to reduce nitrate as an electron acceptor, realizing the key step of nitrogen removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the electron microscopy scan diagram of waste adsorbent S1 before treatment in the embodiment of the present invention;

[0037] Figure 2 is the electron microscopy scan diagram of waste adsorbent S1 after treatment in the embodiment of the present invention;

[0038] Figure 3 is the nitrogen and phosphorus removal performance of sewage under different filler ratios in the embodiment of the present invention;

[0039] Figure 4 is the physical diagram of the waste adsorbent in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] To further elaborate on the methods adopted and the effects achieved by the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with experiments.

[0041] Among the currently circulating sulfur autotrophic denitrification filler products in the market, no varieties with the function of composite simultaneous phosphorus removal have been found. According to the existing technical literature, these sulfur autotrophic denitrification fillers are mainly used to remove nitrogen elements from the water body, but they cannot remove phosphorus elements while removing nitrogen. This limitation leads to the accumulation of phosphorus elements in the water body, thereby affecting the purity of the water quality. In addition, traditional separate phosphorus removal processes often require additional chemical reagents or adsorption materials, which not only increase the economic cost in the water treatment process but also make the operation process more complex and cumbersome.

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

[0043] 1) The demand for a large amount of carbon sources in the denitrification process may be difficult to meet or costly under specific conditions; 2) The denitrification and phosphorus removal processes are usually completed in different treatment units, which requires a long residence time, resulting in a large volume of treatment facilities; 3) During the denitrification process, excessive release of nitrogen gas may occur, leading to sludge bulking problems; 4) During the phosphorus removal process, chemical agents are needed for chemical phosphorus removal, which may bring additional treatment costs and potential secondary pollution problems, increasing costs and operational complexity; 5) Among the currently marketed sulfur autotrophic denitrification filler products, no varieties with the function of combined synchronous phosphorus removal have been found, and phosphorus removal cannot be achieved synchronously, resulting in the accumulation of phosphorus in the water body and affecting the quality of the treated effluent.

[0044] In view of the deficiencies in the existing technology, this study proposes an innovative integrated technology for denitrification and phosphorus removal. The aims of this technology are as follows: 1) By combining specific phosphorus-absorbing materials with sulfur autotrophic denitrification fillers, simultaneous removal of nitrogen and phosphorus is achieved, resulting in a dual purification effect; 2) Reducing the dependence on external carbon sources, simplifying the treatment process, shortening the treatment cycle, reducing the volume of required facilities, as well as equipment investment and operating costs, thus demonstrating significant economic benefits; 3) Reducing or eliminating the use of chemical agents and decreasing the possibility of secondary pollution; 4) This technology also considers the principles of environmental protection and sustainability in the reuse of waste, ensuring that the negative impact on the environment during the sewage treatment process is minimized.

[0045] In view of this, the embodiments of the present invention aim to provide an innovative filler product and a method for treating wastewater using this filler product. This filler can not only efficiently carry out sulfur autotrophic denitrification reactions but also synchronously remove phosphorus in the water body. By achieving this dual function, the water treatment process can be greatly simplified, the overall treatment cost can be reduced, and the water treatment efficiency can be significantly improved. This can not only reduce environmental pollution but also bring economic benefits and technological progress to the water treatment industry.

[0046] The embodiments of the present invention design a pretreatment method to simultaneously achieve denitrification and phosphorus removal by using waste adsorbents in combination with sulfur autotrophic denitrification fillers, treating waste with waste, reducing the cost of wastewater denitrification and phosphorus removal treatment, and improving the 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 one of the above; specifically, in Example 1 below, the MBR effluent (secondary treated effluent after membrane bioreactor treatment) during municipal sewage treatment is treated, that is, the sewage to be treated referred to in Example 1 below is the MBR effluent during municipal sewage treatment;

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

[0049] S1. Pretreatment of waste adsorbents;

[0050] The waste adsorbents used in the present invention are waste landfill gas desulfurization adsorbents, taken from a landfill gas purification treatment station at a certain location;

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

[0052] Table 1 Main elemental composition of waste adsorbents

[0053] Element C O Mg Si S Ca Ti Fe Mass percentage (%) 9.54 37.95 0.42 0.54 8.61 24.53 0.49 17.92

[0054] S1-1. Take the waste adsorbents and wash the waste adsorbents with deionized water until the deionized water after washing is in a clear state, and then perform primary drying on the washed waste adsorbents; the method of primary drying is natural air drying until completely dry;

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

[0056] S1-3. Take out the waste adsorbents after soaking, and then wash the waste adsorbents with deionized water again until the pH value of the deionized water washed out is 7, and then perform secondary drying; the method of secondary drying is drying at 80 °C for 6 h;

[0057] S1-4. Perform heat treatment on the waste adsorbents after secondary drying, and the heat treatment is: heating the waste adsorbents after secondary drying to 400 °C under anaerobic conditions and holding for 4 h, that is, the pretreatment is completed;

[0058] S2. Sewage treatment

[0059] Mix the sulfur autotrophic denitrification filler and the pretreated waste adsorbent of S1 evenly at a mass ratio of 1:9 to obtain a mixture. Add the mixture as the denitrification filler into a reactor for water treatment. Inside the reactor (a columnar continuous flow reactor), an anaerobic zone, a biofilm zone, and a clear water zone are successively arranged from the inlet of the reactor to the outlet direction of the reactor; the denitrification filler is located in the anaerobic zone and the biofilm zone of the reactor; start the reactor, take anaerobic sludge accounting for 52% of the volume of the reactor, and evenly pour the anaerobic sludge into the reactor from the inlet of the reactor for film formation. After the film formation is completed, then continuously introduce sewage into the reactor. The residence time of the sewage in the reactor is 8 h; the anaerobic sludge is obtained from the denitrification tank; the microbial content in the anaerobic sludge is 65%;

[0060] The sewage is the sewage to be treated;

[0061] Before the sewage is introduced into the reactor, it is necessary to first determine the theoretical value of the sulfur autotrophic denitrification alkalinity demand of the sewage; among them, the method for the theoretical value of the sulfur autotrophic denitrification alkalinity demand of the sewage is: obtain the content of nitrate nitrogen in the sewage, and then multiply each gram of nitrate nitrogen by 3.9 to obtain the theoretical value of the sulfur autotrophic denitrification alkalinity demand of the sewage;

[0062] Then detect the alkalinity of the sewage. When the alkalinity in the sewage is less than the theoretical value of the sulfur autotrophic denitrification alkalinity demand, add an alkaline substance (the alkaline substance in this embodiment is calcium hydroxide) to adjust until the alkalinity in the sewage is greater than or equal to the theoretical value of the sulfur autotrophic denitrification alkalinity demand; when the alkalinity in the sewage is greater than or equal to the theoretical value of the sulfur autotrophic denitrification alkalinity demand, no adjustment is required; among them, the above-mentioned theoretical value of the sulfur autotrophic denitrification alkalinity demand and the alkalinity of the sewage are both in mg(CaCO 3 ) / L;

[0063] The working principle of the reactor is: The sewage first enters the anaerobic zone of the reactor. In this area, denitrifying bacteria use organic matter as an electron donor to reduce nitrate or nitrite to nitrogen gas, achieving the removal of nitrogen. Subsequently, the sewage enters the biofilm zone, and the microorganisms attached to the filler degrade and purify the organic matter in the sewage. The treated sewage is discharged from the reactor to achieve the purpose of purifying the water quality;

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

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

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

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

[0068] 1). The scanning electron microscope analysis of the untreated waste adsorbent and the waste adsorbent treated by S1 is as Figure 1 、 Figure 2 shown; through characterization analysis, its true density is obtained as 2.5444 g / cm 3 、and the bulk density is 0.0034 g / cm 3 .

[0069] 2). If the effluent nitrate nitrogen concentration remains stable after continuous operation for 7 days, it is considered that the reactor startup is completed. Shorten the EBCT to 4 h, and collect and sample the influent and effluent of the device and the effluent at different filler heights; after the water sample is filtered through a 0.45 μm filter membrane, measure the concentrations of nitrate nitrogen and nitrite nitrogen, and measure the total phosphorus concentration of the unfiltered water sample.

[0070] The experimental results are as follows:

[0071] Analysis of sample test results

[0072] The effects of different filler filling mass ratios on the nitrate nitrogen removal effect of MBR effluent and the effluent nitrite nitrogen concentration are respectively as Figure 3 shown in a&b. The results show that the effluent nitrate nitrogen of the reactors with 4 filling mass ratios (Example 1, Example 2, Example 3 and Example 4) is at a low level, and all have good denitrification effects. The reactor with a filling mass ratio of 1:9 has the best nitrate nitrogen removal effect. However, when the filling mass ratios are 2:8, 3:7 and 4:6 (Example 2, Example 3 and Example 4), the effluent nitrite nitrogen is relatively high. The reactor is backwashed on the 2nd and 16th days of the experiment. After backwashing, the reactor needs time to recover its denitrification performance, and the higher the mass filling ratio of the waste adsorbent, the longer the recovery time of the reactor and the higher the concentration of the effluent nitrite nitrogen. The effects of different filling mass ratios on the phosphorus removal effect of the reactor and the phosphorus removal performance along the way are respectively as Figure 3 shown in c&d. The results show that the higher the mass filling ratio of the waste adsorbent, the lower the total phosphorus concentration of the reactor effluent and the better the phosphorus removal effect. This is because the main component of the waste adsorbent is iron salt. The larger the adsorbent filling ratio, the more iron salt dissolves out, the stronger the adsorption ability to phosphorus-containing compounds, and the better the phosphorus removal effect of the reactor.

[0073] From the above results, it can be seen that the combined use of sulfur autotrophic denitrification filler and waste adsorbent can completely achieve simultaneous nitrogen and phosphorus removal from the MBR effluent. When the mass ratio of sulfur autotrophic denitrification filler to waste adsorbent is 9:1, an ideal denitrification effect can be achieved, and at the same time, the phosphorus removal performance can also meet the discharge requirements of Standard GB 16889.

[0074] Example 5: The difference between this example and Example 1 is that the time parameters in S1 are different. In S1-2, the dried waste adsorbent is placed in an acid solution and soaked for 3 h; in S1-3, it is dried for 7 h; in S1-4, heating continues for 5 h.

[0075] Example 6: The difference between this example and Example 1 is that the time parameters in S1 are different. In S1-2, the dried waste adsorbent is placed in an acid solution and soaked for 6 h; in S1-3, it is dried for 5 h; in S1-4, heating continues for 3 h.

[0076] Example 7: The difference between this example and Example 1 is that in S1, it is kept at a constant temperature of 20 °C until completely dry, and in S1-4, it is heated to 300 °C under anaerobic conditions;

[0077] Example 8: The difference between this example and Example 1 is that in S1, it is kept at a constant temperature of 35 °C until completely dry, and in S1-4, it is heated to 500 °C under anaerobic conditions;

[0078] Example 9: The difference between this example and Example 1 is that in S1-3, it is washed until the pH value of the deionized water washed out is 6.

[0079] Example 10: The difference between this example and Example 1 is that in S1-3, it is washed until the pH value of the deionized water washed out 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: The difference between this example and Example 1 is that in S2, the anaerobic sludge accounts for 55% of the reactor volume; the residence time of the sewage in the reactor is 7 h; the microbial content in the anaerobic sludge is 60%.

[0084] Example 15: The difference between this example and Example 1 is that in S2, the anaerobic sludge accounts for 50% of the volume of the reactor; the residence time of the sewage in the reactor is 9 h; the microbial content in the anaerobic sludge is 70%.

[0085] Example 16: The difference between this example and Example 1 is that while starting the reactor, a DC voltage of 0.6 V is applied to the anaerobic zone in the reactor, and a DC voltage of 1.0 V is applied to the biofilm zone in the reactor.

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

[0087] Example 18: The difference between this example and Example 16 is that while starting the reactor, a DC voltage of 0.8 V is applied to the anaerobic zone in the reactor, and a DC voltage of 1.2 V is applied to the biofilm zone in the reactor.

[0088] Example 19: The difference between this example and Example 16 is that in S1-4, before heat treatment, the waste adsorbent is subjected to plasma treatment. The plasma treatment method is as follows: According to the ratio of 2 ml: 10 g, a titanate coupling agent with a mass concentration of 13% and the waste adsorbent are taken, the titanate coupling agent is sprayed on the surface of the waste adsorbent, and after standing for 15 min, then a plasma surface treatment machine (the plasma surface treatment machine used is the Tantec plasma surface treatment machine in the prior art) is used to apply plasma irradiation with a frequency of 13 MHz to the waste adsorbent in a nitrogen atmosphere, and the application time is 20 min, and the plasma treatment is completed.

[0089] Example 20: The difference between this example and Example 19 is that the plasma treatment method is as follows: According to the ratio of 1 ml: 10 g, a titanate coupling agent with a mass concentration of 10% and the waste adsorbent are taken, the titanate coupling agent is sprayed on the surface of the waste adsorbent, and after standing for 10 min, then a plasma surface treatment machine is used to apply plasma irradiation with a frequency of 14 MHz to the waste adsorbent in a nitrogen atmosphere, and the application time is 30 min, and the plasma treatment is completed.

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

[0091] II. Operate according to the methods of Examples 1 to 19 respectively, and the results are as follows:

[0092] 1. Explore the influence of different treatment methods on the water treatment results;

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

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

[0095] Comparative Example 3: The difference from Example 1 is that the waste adsorbent is not pretreated by S1;

[0096] Comparative Example 4: The difference from Example 1 is that anaerobic sludge from the river bottom is taken for treatment;

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

[0098] Take Example 1, Example 2, Example 3, Example 15, Example 16, and Comparative Examples 1 - 4, and compare the nitrate nitrogen and total phosphorus in the effluent obtained by operating according to the methods of these examples, as shown in Table 1;

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

[0100] Parameter Nitrate nitrogen removal rate % Total phosphorus removal rate % 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 can be seen from Table 1, by comparing Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that after the two fillers used in Example 1 are mixed, the water treatment effect is better. Especially when compared with the removal of total phosphorus in Comparative Example 1, this may be because in Comparative Example 1, when using general fillers for treatment, only denitrification removal of nitrogen can be achieved, while for phosphorus, the existing fillers cannot effectively remove phosphorus. It may be that the removal of phosphorus requires metal elements such as iron elements in the filler. These metal ions can chemically react with phosphate ions in the sewage to form water-insoluble precipitates, and the metal ions can also exchange with other cations in the water body. Through the ion exchange effect, the removal of phosphorus can be promoted; in Comparative Example 2, only waste adsorbents are used. Although the waste adsorbents have a good effect on the removal of phosphorus, the effect of denitrification and nitrogen removal needs to be improved. Therefore, the method of Example 1 is more preferable.

[0102] By comparing Example 1 and Comparative Example 3, it can be seen that compared with no pretreatment in Comparative Example 3, after the waste adsorbent in Example 1 is pretreated, its effect on nitrogen and phosphorus removal from sewage is better. 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, and improve the surface properties of the adsorbent. Heat treatment can remove organic matter and moisture on the surface of the adsorbent, improving the stability and adsorption capacity of the adsorbent.

[0103] By comparing Example 1 and Comparative Example 4, it can be seen that in Comparative Example 4, anaerobic sludge from the river bottom is used for water treatment. Compared with directly using the anaerobic sludge from the river bottom in the denitrification tank, there may be more impurities and sediment in the anaerobic sludge from the river bottom, which affects the sewage treatment process, resulting in a decrease in the effect of nitrogen and phosphorus removal.

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

[0105] By comparing Example 16 and Example 19, it can be seen that on the basis of Example 16, Example 19 adds a process of surface treatment of 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 sewage. This may be because through plasma surface treatment, a more stable surface structure can be promoted to form on its surface, further improving its adsorption performance and durability, enabling it to more efficiently adsorb pollutants in the water body and simultaneously increasing the adsorption capacity.

[0106] 2. Explore the influence of different treatment parameters on the experimental results of sewage treatment;

[0107] Take Example 1, Examples 5 - 15 for comparison, as shown in Table 2;

[0108] Table 2 Influence of different treatment parameters on the experimental results of sewage treatment

[0109]

[0110]

[0111] It can be seen from Table 2 that by comparing Example 1, Example 5 with Example 6, Example 7 with Example 8, it can be found that the time and temperature parameters of Example 1 are more preferable. 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 surface of the waste adsorbent and cause corresponding changes. Among them, the parameters in Example 1 are more excellent.

[0112] By comparing Example 1, Example 9 with Example 10, it can be found that the pH value of the waste adsorbent after cleaning in Example 1 has a certain influence on the result of water treatment. This may be because after the acidity and alkalinity between the waste adsorbent and the sewage change, it may affect the adsorption and reaction of the adsorbent to phosphorus atoms in the water body during the water treatment process. By comparing Example 1, Example 12 with Example 13, it can be found that the waste landfill gas desulfurization adsorbent in Example 1 is more preferable as a raw material. This may be because the elemental composition of the waste landfill gas desulfurization adsorbent is superior to that of other adsorbents. By comparing Example 1, Example 14 with Example 15, it can be found that the treatment parameters of the reactor in Example 1 are more excellent.

[0113] In summary, the present invention provides an efficient, economical and environmentally friendly synchronous denitrification and phosphorus removal technology. By optimizing the operating parameters of the reactor and the combination ratio of the fillers, the present invention not only improves the treatment efficiency, reduces the operating cost, but also reduces the potential impact on the environment. This technical solution has broad application prospects, especially in the fields of municipal sewage treatment and industrial wastewater treatment, and can provide strong technical support for realizing sustainable development.

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

[0115] (1) The fillers proposed by the present invention exhibit excellent physical and chemical stability, wide adaptability, and are suitable for variable water treatment environments. The high proportion of waste adsorbent addition helps to shorten the recovery period of the reactor, extend the service life, thereby reducing the replacement frequency and maintenance cost.

[0116] (2) The operating parameters of the reactor have been optimized in the present invention, especially the EBCT (Effective Biological Contact Time). When using waste adsorbent 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 an ideal denitrification and phosphorus removal effect.

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

[0118] To adapt to different influent water qualities and treatment requirements; it can further improve the denitrification and phosphorus removal effects of the reactor and ensure the stability and safety of the effluent water quality; for example, 3 reactors for film formation and start-up were used in the experiment, named Reactor 5, Reactor 6, and Reactor 7. The EBCT of each reactor was set to 4h. Sewage was continuously fed into the reactor and waited until the effluent nitrate nitrogen concentration reached a stable level. The influent of Reactor 5 had no alkalinity adjustment.

[0119] The theoretical formula for the alkalinity demand of sulfur autotrophic denitrification is: 1.06NO 3 - +1.11S + 0.3CO 2 +0.785H 2 O → 0.06C 5 H 7 O 2 N + 0.5N 2 +1.11SO 4 2- +1.16H + ; for example, it can be obtained from this formula that the alkalinity consumption value for removing 1 mg of nitrate nitrogen by sulfur autotrophic denitrification is 3.9 mg (calculated as CaCO 3 ); the experimental results show that the alkalinity of the sewage itself is about 1200 mg / L (calculated as CaCO 3 ), which is 400% of the theoretical value of the alkalinity demand for sulfur autotrophic denitrification and can provide sufficient alkalinity to enable sulfur autotrophic denitrification to achieve the best denitrification effect. Therefore, there is no need to adjust the alkalinity.

[0120] To prove the influence of pH on the removal effects of total nitrogen and nitrate nitrogen, 50% dilute sulfuric acid was used to adjust the influent alkalinity of Reactor 6 and Reactor 7 to 85% and 65% of the theoretical value of the alkalinity demand for sulfur autotrophic denitrification, respectively. In the experiment, the influent and effluent of each reactor were collected and sampled. After the water samples were filtered through a 0.45 μm filter membrane, the concentration of nitrate nitrogen was measured. During the 20-day operation cycle, the removal rates of total nitrogen and nitrate nitrogen were maintained above 90% and 95%, respectively. When the alkalinity dosage was adjusted to 85% of the theoretical demand value, the total nitrogen removal rate decreased to about 70%, while the nitrate nitrogen removal rate could still be maintained above 95%, showing a relatively good denitrification effect. With the continuous decrease of the alkalinity dosage, the denitrification performance showed a downward trend. When the alkalinity dosage was adjusted to 65% of the theoretical demand value, the total nitrogen removal rate decreased to about 60%, and the nitrate removal efficiency dropped below 90%. The effluent nitrate nitrogen concentration was between 6 - 12 mg / L;

[0121] The above experiment proved that alkalinity adjustment was necessary. That is to say, when the alkalinity was insufficient, the removal rates of total nitrogen and nitrate nitrogen were low, and when the alkalinity met the requirements of the examples, the removal rates of total nitrogen and nitrate nitrogen were good.

[0122] IV. Experimental effects of the biofilm formation and start-up of the sulfur autotrophic denitrification reactor;

[0123] During the biofilm formation and start-up stage of the continuous-flow sulfur autotrophic reactor, anaerobic sludge was first evenly poured into the columnar sulfur autotrophic denitrification reaction device filled with packing. Then, sewage was continuously fed into the device, and the empty bed contact time (EBCT) was set to 6 h, and the influent pH was controlled between 8 - 9. The influent and effluent of the reactor were collected and sampled. After the water samples were filtered through a 0.45 μm filter membrane, the concentrations of nitrate nitrogen and nitrite nitrogen were measured. The empty bed contact time was determined by the following formula (1):

[0124]

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

[0126] The results of the changes in the nitrate nitrogen concentration and nitrite nitrogen concentration of the influent and effluent during the start-up process of the reactor membrane biofilm formation show that the effluent nitrate nitrogen concentration of each reactor gradually decreases and stabilizes with the number of operating days, and the effluent nitrite nitrogen concentration first increases and then decreases and maintains a relatively low concentration level. In the first 4 days after start-up, the effluent nitrate nitrogen concentration of each reactor decreased rapidly, and the microorganisms grew rapidly during this period. The nitrite nitrogen concentration of each reactor reached its peak on the fourth day, and the nitrite nitrogen concentration of reactor 3 was as high as 8.86 mg / L. This may be because the reactor had not successfully formed a membrane and was in an unstable stage. The types and numbers of microorganisms were both growing rapidly, the number of nitrite-reducing bacteria was insufficient, and denitrification was incomplete. After the 4th day, the effluent nitrite nitrogen concentration of each reactor began to decrease and was basically 0 mg / L on the 7th day. At this time, the effluent nitrate nitrogen concentration also tended to 0 mg / L, and each reactor tended to a stable state. On the 10th day, the effluent nitrate nitrogen concentration and nitrite nitrogen concentration of each reactor were at a relatively low level, and it was considered that the reactor had successfully formed a membrane and subsequent experiments could be carried out.

[0127] V. Experimental results of the empty bed contact time (EBCT)

[0128] In the start-up stage, after the membrane biofilm formation of reactors 1, 2, 3, and 4 was successful, the effect of the empty bed contact time (EBCT) on the sulfur autotrophic denitrification process was explored. The EBCTs of reactors 1, 2, 3, and 4 in the experiment were set to 1, 2, 3, and 4 h respectively, and the influent pH was controlled between 8 and 9. Hydraulic backwashing was carried out when the effluent nitrate nitrogen and nitrite nitrogen concentrations increased significantly. During the experiment, the influent and effluent of each reactor were collected and sampled regularly. After the water samples were filtered through a 0.45 μm filter membrane, the concentrations of nitrate nitrogen, nitrite nitrogen, total nitrogen, and sulfate were measured.

[0129] The results show that the effluent total nitrogen and nitrate nitrogen concentrations decrease with the extension of EBCT. When EBCT is 1 h, the effluent total nitrogen concentration is basically higher than 40 mg / L, and the discharge limit in Table 2 of GB 16889 cannot be reached. There is still 10 - 20 mg / L of nitrate nitrogen concentration remaining in the effluent. When EBCT is 2 h, after a backwashing was carried out on the 6th day, the effluent total nitrogen was lower than the discharge limit, and the concentration remained between 30 and 40 mg / L. The effluent nitrate nitrogen concentration was also stable below 10 mg / L. When EBCT is 3 h and 4 h, the effluent total nitrogen remains below 30 mg / L, and the effluent nitrate nitrogen remains at a relatively low level, that is, below 5 mg / L, with a good denitrification effect. If EBCT is too short, the autotrophic microorganisms in the reactor cannot fully utilize the electron donor and nutrients, resulting in incomplete nitrate nitrogen removal. Sulfur autotrophic denitrification mainly aims at the removal of nitrate nitrogen. Therefore, by comparison, it is found that the change trends of the effluent total nitrogen concentration and nitrate nitrogen concentration of each reactor under the influence of EBCT are consistent. It can be seen that the removal laws of nitrate nitrogen and total nitrogen in this reaction system have a strong correlation.

[0130] The concentration of nitrite nitrogen in the effluent decreases with the extension of EBCT. The shorter the EBCT, the more serious the residual situation of nitrite nitrogen. When EBCT is 1 h, the concentration of nitrite nitrogen in the effluent can reach as high as 26.43 mg / L. When EBCT is 4 h, the concentration of nitrite nitrogen in the effluent is at a relatively low level, and it can be considered that there is no nitrite nitrogen accumulation. During the denitrification reaction in the sulfur autotrophic denitrification filter, intermediate products such as nitrite nitrogen appear during the reduction of nitrate nitrogen to nitrogen gas, that is, the reduction rate of intermediate products such as nitrite nitrogen to nitrogen gas is lower than the reduction rate of nitrate nitrogen, and the accumulation of intermediate products such as nitrite nitrogen will inhibit the removal of nitrate nitrogen.

[0131] The concentration of sulfate in the effluent increases with the extension of EBCT. The longer the EBCT, the greater the sulfate production. When EBCT is 4 h, the concentration of sulfate in the effluent can reach as high as 528 mg / L. The GB 16889 discharge standard does not require the concentration of sulfate in the effluent. During the sulfur autotrophic denitrification process, elemental sulfur acts as an electron donor and is oxidized under the action of microorganisms to finally form sulfate, and the nitrate nitrogen in the water gets electrons and finally becomes nitrogen gas. Therefore, the sulfate generated in this process can reflect the removal effect of nitrate nitrogen. The longer the EBCT, the better the nitrate nitrogen removal effect and the greater the sulfate production.

[0132] VI. Experimental effects of hydraulic backwashing intensity

[0133] The EBCTs of Reactor 1, Reactor 2, Reactor 3 and Reactor 4 are all set to 4 h, and the MBR effluent is continuously introduced into the device. When the nitrate nitrogen removal rate of the reactor is lower than 70%, the exploration of the influence of hydraulic backwashing intensity is carried out. The hydraulic backwashing intensities of Reactor 1, 2, 3 and 4 are set to 3 L / (m2·s), 6 L / (m2·s), 9 L / (m2·s) and 12 L / (m2·s) respectively. After backwashing, the influent and effluent of each reactor are collected and sampled, and the concentration of nitrate nitrogen is measured after the water sample is filtered through a 0.45 μm filter membrane. The greater the hydraulic backwashing intensity, the more biofilm is washed away and the fewer microorganisms remain on the surface of the packing. When the hydraulic backwashing intensity is 3 L / (m2·s), the washing force is small, and there are still many microorganisms remaining on the surface of the packing, and the packing layer is likely to be blocked again; when the hydraulic backwashing intensity is 12 L / (m2·s), the biofilm on the surface of the packing is relatively sparse, and more microorganisms are washed away, which is beneficial to alleviating the blockage situation.

Claims

1. A method for simultaneous denitrification and phosphorus removal using spent adsorbent, characterized in that: The following steps are involved: S1. Pretreatment of waste adsorbent; S1-1, taking a waste adsorbent, wherein the sulfur content and the iron content in the waste adsorbent are both greater than or equal to 5%; washing the waste adsorbent with deionized water until the deionized water after washing is clear, and then drying the washed waste adsorbent once; S1-2, placing the once dried waste adsorbent in an acid solution with a mass concentration of 3% for 3 to 6 hours at a solid-liquid ratio of 1 g:5 ml; S1-3, taking out the soaked waste adsorbent, and then washing the waste adsorbent again with deionized water until the pH value of the washed deionized water is 6-8, and then performing secondary drying; S1-4, heat-treating the waste adsorbent after the secondary drying, wherein the heat-treating comprises: heating the waste adsorbent after the secondary drying to 300-500° C. in an anaerobic environment and keeping the temperature for 3-5 hours, that is, the pretreatment is completed; S2. Wastewater treatment The sulfur autotrophic denitrification filler and the pretreated waste adsorbent of S1 are uniformly mixed in a mass ratio of 1-4:6-9 to obtain a mixture, and the mixture is added into a reactor for water treatment as a denitrification filler, and the interior of the reactor is divided into an anaerobic zone, a biofilm zone and a clear water zone in sequence from the inlet of the reactor to the outlet of the reactor; the denitrification filler is located in the anaerobic zone and the biofilm zone of the reactor; the reactor is started, anaerobic sludge accounting for 50-55% of the volume of the reactor is taken, and the anaerobic sludge is uniformly poured into the reactor from the inlet of the reactor for biofilm formation, and after the biofilm formation is completed, sewage is continuously introduced into the reactor, and the sewage stays in the reactor for 7-9 hours.

2. A method for simultaneous denitrification and phosphorus removal using waste adsorbent as claimed in claim 1, characterized in that: The primary drying method in S1-1 is air drying or constant temperature drying at 20 to 35° C. until completely dried.

3. The method for simultaneous denitrification and phosphorus removal using waste adsorbent according to claim 1, characterized in that: The secondary drying method in S1-3 is drying at 80° C. for 5 to 7 hours.

4. The method for simultaneous denitrification and phosphorus removal using waste adsorbent according to claim 1, characterized in that: The acid solution is any one of dilute sulfuric acid and dilute hydrochloric acid.

5. The method for simultaneous denitrification and phosphorus removal using waste adsorbent according to claim 1, characterized in that: The anaerobic sludge is obtained from a denitrification tank.

6. The method for simultaneous denitrification and phosphorus removal using spent adsorbent as claimed in claim 1, characterized in that: The waste adsorbent is any one of a waste landfill gas desulfurization adsorbent, a natural mineral adsorbent or a synthetic adsorbent.

7. The method for simultaneous denitrification and phosphorus removal using spent adsorbent according to claim 1, characterized in that: The microorganism content in the anaerobic sludge is 60-70%.

8. The method for simultaneous denitrification and phosphorus removal using spent adsorbent as claimed in claim 1, characterized in that: When the reactor is started, a DC voltage of 0.5 to 0.8 V is applied to the anaerobic zone in the reactor, and a DC voltage of 0.9 to 1.2 V is applied to the biofilm zone of the reactor.

9. The method for simultaneous denitrification and phosphorus removal using waste adsorbent according to claim 1, characterized in that: In S1-4, before the heat treatment, the waste adsorbent is subjected to plasma treatment, and the plasma treatment method is as follows: according to the ratio of 1 to 3 ml: 10 g, a titanate coupling agent and a waste adsorbent with a mass concentration of 10 to 15% are taken, and the titanate coupling agent is sprayed on the surface of the waste adsorbent. After standing for 10 to 20 minutes, a plasma surface treatment machine is used to apply plasma irradiation with a frequency of 12 to 14 MHz to the waste adsorbent in a nitrogen atmosphere for 15 to 30 minutes, and the plasma treatment is completed.

10. The method for simultaneous denitrification and phosphorus removal using spent adsorbent according to claim 1, characterized in that: The sewage described in S2 is sewage to be treated: Before the sewage is introduced into the reactor, the theoretical value of the sulfur autotrophic denitrification alkalinity requirement of the sewage needs to be determined; wherein the method for the theoretical value of the sulfur autotrophic denitrification alkalinity requirement of the sewage is: obtaining the content of nitrate nitrogen in the sewage, and then multiplying each gram of nitrate nitrogen by a ratio of 3.9 to obtain the theoretical value of the sulfur autotrophic denitrification alkalinity requirement of the sewage; Then detect the alkalinity of the sewage. When the alkalinity in the sewage is less than the theoretical value of the alkalinity requirement for sulfur autotrophic denitrification, add alkaline substances to adjust the alkalinity in the sewage to be greater than or equal to the theoretical value of the alkalinity requirement for sulfur autotrophic denitrification; when the alkalinity in the sewage is greater than or equal to the theoretical value of the alkalinity requirement for sulfur autotrophic denitrification, no adjustment is required; wherein, the theoretical value of the alkalinity requirement for sulfur autotrophic denitrification and the alkalinity of the sewage are both measured in mg(CaCO3) / L.

Images