Sewage nitrogen and phosphorus removal treatment method based on nitrification and denitrification

Abstract

The invention relates to the technical field of sewage treatment, in particular to a sewage nitrogen and phosphorus removal treatment method based on nitrification and denitrification. The sewage nitrogen and phosphorus removal treatment method based on nitrification and denitrification comprises the following steps: sequentially carrying out anaerobic treatment, anoxic treatment and aerobic treatment on sewage to obtain primary effluent and sludge, refluxing the sludge, carrying out MBBR treatment and precipitation on the primary effluent to obtain nitrification liquid and effluent, refluxing the nitrification liquid, and refluxing the effluent to obtain secondary effluent; when the anoxic treatment and the aerobic treatment are carried out, the system also comprises zeolite; the hydraulic retention time ratio of the anaerobic treatment to the anoxic treatment to the aerobic treatment is 1: (1-2): (3-6); according to the method, on the premise that the TP removal rate is kept high, the TN removal rate can be further increased, the final TN removal rate can reach 90.25% or above, the carbon source is fully and efficiently utilized, the difficulty that C / N is low is overcome, and meanwhile the good nitrogen and phosphorus removal effect is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular to a sewage denitrification and dephosphorization treatment method based on nitrification and denitrification. Background Art

[0002] At present, the main sources of domestic sewage and industrial sewage are very wide. Sewage from different sources is bound to contain different contents and types of pollutants. Therefore, technicians roughly divide sewage into different types of sewage such as high-salt sewage, high-nitrogen and phosphorus content sewage and high-COD sewage, and carry out different targeted treatments. Among them, sewage with high nitrogen and phosphorus content will lead to eutrophication of water bodies, promote excessive growth of algae, form algal blooms, consume dissolved oxygen in water bodies, affect the survival of aquatic organisms, and in severe cases, lead to imbalance of water ecosystems and even the appearance of "dead zones". The nitrogen and phosphorus in sewage with high nitrogen and phosphorus content mainly come from agricultural fertilizers, washing products, surface pollutants and chemical processing wastes. It can be seen that the discharge volume of sewage with high nitrogen and phosphorus content is very large. Effective treatment of it and reducing its pollution to water bodies are important tasks of environmental protection and water resources management.

[0003] There are many technologies that can be used to treat wastewater with high nitrogen and phosphorus content, including biological treatment, chemical treatment and physical treatment. With the gradual exploration of technicians, people have found that chemical and physical technologies are not easy to meet the discharge standards for nitrogen and phosphorus treatment, or additional chemical agents need to be added to meet the discharge standards; in contrast, biological denitrification and phosphorus removal technology has low cost and good sustainability, and is widely used in sewage treatment. Traditional biological denitrification and phosphorus removal mainly rely on nitrifying bacteria and denitrifying bacteria to complete the denitrification process under aerobic and anoxic conditions, and polyphosphate bacteria to complete the phosphorus release and excessive phosphorus absorption process during anaerobic / aerobic alternation.

[0004] However, the traditional biological denitrification and phosphorus removal technology has the problem of low C / N ratio, and the lack of carbon source has become a major problem for sewage treatment plants to treat sewage, which will lead to insufficient nitrogen and phosphorus removal, and the addition of carbon source will increase the treatment cost. Therefore, the AAO-MBBR (anaerobic / anoxic / aerobic-moving bed biofilm) process, which belongs to the double sludge process, stands out from many treatment methods. This method can fully and efficiently utilize the carbon source, overcome the difficulty of low C / N, and ultimately increase the TP removal rate of the effluent to more than 98%, and the TN removal rate to more than 78%. More importantly, the researchers further optimized its denitrification effect on this basis, in order to obtain a more complete method for treating sewage with high nitrogen and phosphorus content. Summary of the invention

[0005] In order to solve the above technical problems, the present application provides a method for treating wastewater nitrogen and phosphorus removal based on nitrification and denitrification.

[0006] The present application provides a method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, comprising the following steps: subjecting the wastewater to anaerobic treatment, anoxic treatment and aerobic treatment in sequence to obtain primary effluent and sludge, the sludge is returned, the primary effluent is treated by MBBR, and nitrification liquid and effluent are obtained after precipitation, the nitrification liquid is returned, and when the anoxic treatment is performed, the system further comprises zeolite added in an amount of 50-80 g / L; the hydraulic retention time ratio of the anaerobic treatment, the anoxic treatment and the aerobic treatment is 1:(1-2):(3-6).

[0007] The anaerobic treatment, anoxic treatment and aerobic treatment are carried out in the anaerobic zone, anoxic zone and aerobic zone respectively, the treatment temperature is 25°C, and the anaerobic zone, anoxic zone and aerobic zone are connected in sequence, the volume ratio of the three is 1:5:1, the tail end of the aerobic zone is connected to a sludge tank, and the hydraulic retention time of AAO is controlled to be 12h, where mud and water separation is achieved to obtain primary effluent and sludge, the sludge is returned to the anaerobic zone, and the primary effluent is then introduced into the MBBR zone for MBBR treatment. After treatment, it is concentrated in the sedimentation zone for stratification and standing, the upper clear liquid is the effluent, and the lower nitrified liquid is returned to the anoxic zone for further treatment.

[0008] By adopting the above technical solution, the present application adds zeolite to the anoxic treatment, which plays a role in stabilizing the denitrifying bacteria and supplementing the carbon source, effectively improving the system's denitrification and phosphorus removal efficiency. Specifically, the added zeolite can effectively provide an additional organic carbon source and enhance the rate of the denitrification reaction; zeolite can also adsorb heavy metal ions in the water, provide adsorption sites for denitrifying bacteria, and improve the survival rate and activity of denitrifying bacteria. In addition, the present application rationally regulates the hydraulic retention time ratio of anaerobic treatment, anoxic treatment, and aerobic treatment, ensuring the effective connection of each treatment stage, and further improving the treatment effect of the entire system on wastewater with high nitrogen and phosphorus content.

[0009] At the same time, the present application strictly controls the amount of zeolite added and optimizes the final sewage treatment effect. If the amount added is too low, it will not be able to effectively supplement the carbon source and provide sufficient adsorption sites, resulting in reduced nitrogen and phosphorus removal efficiency, and poor effect on improving the activity of denitrifying bacteria, thereby affecting the overall denitrification effect; if the amount added is too high, it may lead to an increase in suspended solids, affecting the stability of subsequent MBBR treatment and effluent water quality. At the same time, too much zeolite may also burden the equipment and increase operating costs.

[0010] In general, the treatment method of the present application can further improve the TN removal rate while maintaining a high TP removal rate. Finally, after testing, it was found that the TN removal rate can reach more than 90.25%. It not only fully and efficiently utilizes the carbon source and overcomes the difficulty of low C / N, but also has good denitrification and phosphorus removal effects.

[0011] Preferably, during the anoxic treatment, the amount of zeolite added is 65 g / L.

[0012] By adopting the above technical solution, the application strictly controls the addition amount of zeolite to 65g / L, which can more effectively supplement the carbon source, provide more adsorption sites, protect denitrifying bacteria, and enhance the stability and treatment effect of the system. Ultimately, this improvement increased the TN removal rate to 90.78%.

[0013] Preferably, the sludge return ratio during the sludge return is 80-150%, and the sludge age is 10-14 days.

[0014] By adopting the above-mentioned technical scheme, the present application ensures sufficient sludge return and improves nitrogen and phosphorus removal efficiency under the premise of effectively utilizing the carbon source provided by zeolite. A reasonable sludge return ratio and sludge age are set during sludge return, thereby ensuring the microbial activity in the system, enhancing the stability and processing capacity of the system, and thus achieving higher TP removal rate and TN removal rate.

[0015] Preferably, in the MBBR treatment, the dissolved oxygen content is 3-4 mg / L and the total gas volume is 0.18-0.2 m 3 / h.

[0016] By adopting the above technical scheme, the present application controls the dissolved oxygen content and total gas volume in the MBBR treatment, ensures the activity and metabolic efficiency of the microorganisms on the biofilm, and optimizes the effective transfer and distribution of oxygen, so that the microorganisms in the MBBR process can more fully utilize the C, N, P, etc. in the water for metabolism, play a role in purifying sewage, and remove ammonia nitrogen and total phosphorus in the water.

[0017] Preferably, in the MBBR treatment, the average biomass of the biofilm is 900-1100 mg / L.

[0018] By adopting the above technical scheme, the present application controls the average biomass of the biofilm in the MBBR treatment within the range of 900-1100 mg / L, which helps to improve the biodegradation capacity of the system, improve the removal efficiency of organic matter and nitrogen and phosphorus, ensure a sufficient number of microorganisms to participate in the metabolic reaction, and avoid the problem of system blockage or unstable operation caused by excessive biomass, thereby achieving efficient sewage denitrification and phosphorus removal.

[0019] Preferably, the reflux ratio of the nitrifying solution reflux is 250-400%.

[0020] By adopting the above technical solution, the present application controls the reflux ratio of the nitrification liquid reflux, significantly increases the nitrate nitrogen concentration in the system, promotes the effective implementation of the denitrification process, and further improves the nitrogen removal efficiency.

[0021] Preferably, the zeolite is prepared by the following method: hydrolyzing ethyl orthosilicate, then mixing with Al2(SO4)3·18H2O, adjusting the pH in the system to 9-11 and stirring for 10-20 hours, standing at a temperature of 120-200°C, washing the obtained solid, drying it, and then immersing it in an alkaline solution and an acid solution in turn, filtering, drying, and calcining to obtain the zeolite.

[0022] By adopting the above technical scheme, the present application uses the precursor of hydrolysis and condensation of tetraethyl orthosilicate in an acidic medium as a silicon source, and then sequentially treats it with alkali and acid to synthesize a zeolite with a mesoporous structure. The pH value, stirring time and standing temperature in the synthesis process are strictly controlled to obtain a zeolite with a good crystalline mesoporous structure, which can provide more adsorption sites for denitrifying bacteria.

[0023] Preferably, the temperature during the standing state is 180°C.

[0024] By adopting the above technical solution, the present application further controls the temperature during standing, obtains zeolite with the best adsorption capacity, enables the denitrifying bacteria to exert the greatest effect, and further improves the final TN removal rate.

[0025] Preferably, the zeolite is also pretreated, specifically, the zeolite is immersed in a 0.001-0.005 mol / L ferric nitrate solution, stirred, filtered, dried, and calcined to obtain Fe-loaded zeolite.

[0026] Preferably, the concentration of the ferric nitrate solution is 0.004 mol / L.

[0027] By adopting the above technical scheme, the present application has carried out Fe loading treatment to zeolite again, and the combination of trivalent iron ions and the skeleton of zeolite can enhance the structural stability of zeolite, reduce the structural damage during use, and this structural stabilization effect helps to maintain the mesoporous structure of zeolite, ensure its long-term adsorption effect, and make the treatment method of the present application have more stable and efficient denitrification and phosphorus removal effect. The present application also strictly controls the concentration of ferric nitrate solution, so that the Fe loaded zeolite finally obtained has good structural stability and adsorption capacity, if the concentration of ferric nitrate solution is too large, the trivalent iron ion loading is too large, then the specific surface area and pore volume of Fe loaded zeolite will be reduced, and its ability to maintain stability for denitrifying bacteria is impaired, if the concentration of ferric nitrate solution is too small, the trivalent iron ion loading is too small, then it is impossible to play a good effect of improving structural stability.

[0028] In summary, this application has the following beneficial technical effects: 1. The present invention adds zeolite in the anoxic treatment, which plays a role in stabilizing denitrifying bacteria and supplementing carbon sources, and can further improve the TN removal rate while maintaining a high TP removal rate. Finally, after testing, it is found that the TN removal rate can reach more than 90.25%, which not only fully and efficiently utilizes the carbon source, overcomes the difficulty of low C / N, but also has good denitrification and phosphorus removal effects; 2. Under the premise of effectively utilizing the carbon source provided by zeolite, the present application ensures sufficient sludge return, improves nitrogen and phosphorus removal efficiency, sets a reasonable sludge return ratio and sludge age when the sludge is returned, ensures the activity of microorganisms in the system, enhances the stability and treatment capacity of the system, controls the dissolved oxygen content and total gas volume in the MBBR treatment, ensures the activity and metabolic efficiency of microorganisms on the biofilm, optimizes the effective transfer and distribution of oxygen, so that the heterotrophic and autotrophic microorganisms on the biofilm in the MBBR can more fully utilize C, N, P, etc. in the water for metabolism, plays a role in purifying sewage, and removes ammonia nitrogen and total phosphorus in the water; 3. The present application utilizes the precursor of ethyl orthosilicate hydrolyzed and condensed in an acidic medium as a silicon source, which is then sequentially treated with alkali and acid to synthesize a zeolite with a mesoporous structure, thereby providing more adsorption sites for denitrifying bacteria. The zeolite is also subjected to Fe loading treatment to enhance the structural stability of the zeolite, reduce structural damage during use, ensure its long-term adsorption effect, and make the treatment method of the present application have a more stable and efficient denitrification and phosphorus removal effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the system used in the processing method of this application. DETAILED DESCRIPTION

[0030] Material Source The specific influent water quality of the sewage treated in this application is shown in Table 1.

[0031] Table 1 Influent water quality First, Figure 1As shown, the treatment system used in the treatment method of the present application is formed by an inlet area, an anaerobic area, an anoxic area, an aerobic area, a sludge pool, an MBBR area, a sedimentation area and an outlet area connected in sequence, wherein the anaerobic area, the anoxic area and the aerobic area constitute an AAO processor, which is pushed along the process and divided into 7 compartments. The volume ratio of the anaerobic area, the anoxic area and the aerobic area is 1:5:1. The sludge pool at the back of the AAO processor is used to achieve mud-water separation, and the bottom sludge is pumped back to the anaerobic area. The upper clear liquid is the primary effluent, which is then pumped into the MBBR area for MBBR treatment. The reactor in the MBBR area is a three-compartment series type, with a polypropylene suspended filler inside. The filler size is Φ25mm×10mm, the center is a grid structure, and the density is 0.96g / cm 3 , porosity is 95%, effective specific surface area is 1200m 2 / m 3 , the filling rate is 45%, the nitrification liquid and effluent are separated in the post-sedimentation area, the nitrification liquid is pumped back to the anoxic area, and the effluent is pumped into the effluent area to realize the denitrification and phosphorus removal of sewage.

[0032] The present application is further described in detail below in combination with preparation examples, embodiments and comparative examples.

[0033] Preparation Example 1.1 The preparation method of zeolite comprises the following steps: 120g of tetraethyl orthosilicate was put into 0.2L of water, and the pH was adjusted to 1 with 0.3mol / L hydrochloric acid solution under vigorous stirring, and then stirred at 20°C for 1d to hydrolyze the tetraethyl orthosilicate; then 27g of Al2(SO4)3·18H2O was dispersed in 400ml of deionized water, stirred evenly, and fully mixed with the above-mentioned tetraethyl orthosilicate hydrolysis solution; the pH in the system was adjusted to 11 with 12mol / L sodium hydroxide solution and then stirred vigorously for 10h, the obtained slurry was transferred to a stainless steel autoclave, and allowed to stand at 200°C for 4d, the obtained solid was washed with deionized water, dried, and then immersed in 1mol / L sodium hydroxide solution and 0.3mol / L oxalic acid solution in turn, the immersion time was 2h, taken out after immersion, filtered, dried, and calcined at 550°C for 4h to obtain zeolite.

[0034] Preparation Example 1.2 The preparation method of zeolite comprises the following steps: 120g of tetraethyl orthosilicate is put into 0.2L of water, and the pH is adjusted to 1 with 0.3mol / L hydrochloric acid solution under vigorous stirring, and then stirred at 20°C for 1d to hydrolyze the tetraethyl orthosilicate; then 27g of Al2(SO4)3·18H2O is dispersed in 400ml of deionized water, stirred evenly, and fully mixed with the above-mentioned tetraethyl orthosilicate hydrolyzate; the pH in the system is adjusted to 9 with 12mol / L sodium hydroxide solution and then vigorously stirred for 20h, the obtained slurry is transferred to a stainless steel autoclave, and allowed to stand at 120°C for 4d, the obtained solid is washed with deionized water, dried, and then immersed in 1mol / L sodium hydroxide solution and 0.3mol / L oxalic acid solution in turn, the immersion time is 2h, taken out after immersion, filtered, dried, and calcined at 550°C for 4h to obtain zeolite.

[0035] Preparation Example 2.1 The preparation method of zeolite is different from that of Preparation Example 1.1 in that the temperature during standing is 130°C, and the rest is the same as that of Preparation Example 1.1.

[0036] Preparation Example 2.2 The preparation method of zeolite is different from that of Preparation Example 1.1 in that the temperature during standing is 140°C, and the rest is the same as that of Preparation Example 1.1.

[0037] Preparation Example 2.3 The preparation method of zeolite is different from that of Preparation Example 1.1 in that the temperature during standing is 150°C, and the rest is the same as that of Preparation Example 1.1.

[0038] Preparation Example 2.4 The preparation method of zeolite is different from that of Preparation Example 1.1 in that the temperature during standing is 160°C, and the rest is the same as that of Preparation Example 1.1.

[0039] Preparation Example 2.5 The preparation method of zeolite is different from that of Preparation Example 1.1 in that the temperature during standing is 170°C, and the rest is the same as that of Preparation Example 1.1.

[0040] Preparation Example 2.6 The preparation method of zeolite is different from that of Preparation Example 1.1 in that the temperature during standing is 180°C, and the rest is the same as that of Preparation Example 1.1.

[0041] Preparation Example 2.7 The preparation method of zeolite is different from that of Preparation Example 1.1 in that the temperature during standing is 190°C, and the rest is the same as that of Preparation Example 1.1.

[0042] Preparation Example 3.1 The preparation method of zeolite is different from that of Preparation Example 2.6 in that the zeolite is also pretreated, specifically: the zeolite is immersed in a 0.001 mol / L ferric nitrate solution, stirred at 60°C for 2 hours, filtered, dried, and calcined at 550°C for 4 hours to obtain Fe-loaded zeolite.

[0043] Preparation Example 3.2 The preparation method of zeolite is different from that of Preparation Example 2.6 in that the zeolite is also pretreated, specifically: the zeolite is immersed in a 0.002 mol / L ferric nitrate solution, stirred at 60°C for 2 hours, filtered, dried, and calcined at 550°C for 4 hours to obtain Fe-loaded zeolite.

[0044] Preparation Example 3.3 The preparation method of zeolite is different from that of Preparation Example 2.6 in that the zeolite is also pretreated, specifically: the zeolite is immersed in a 0.003 mol / L ferric nitrate solution, stirred at 60°C for 2 hours, filtered, dried, and calcined at 550°C for 4 hours to obtain Fe-loaded zeolite.

[0045] Preparation Example 3.4 The preparation method of zeolite is different from that of Preparation Example 2.6 in that the zeolite is also pretreated, specifically: the zeolite is immersed in a 0.004 mol / L ferric nitrate solution, stirred at 60°C for 2 hours, filtered, dried, and calcined at 550°C for 4 hours to obtain Fe-loaded zeolite.

[0046] Preparation Example 3.5 The preparation method of zeolite is different from that of Preparation Example 2.6 in that the zeolite is also pretreated, specifically: immersing the zeolite in a 0.005 mol / L ferric nitrate solution, stirring at 60°C for 2 hours, filtering, drying, and calcining at 550°C for 4 hours to obtain Fe-loaded zeolite.

[0047] Preparation Example 3.6 The preparation method of zeolite is different from that of Preparation Example 2.6 in that the zeolite is also pretreated, specifically: the zeolite is immersed in a 0.0005 mol / L ferric nitrate solution, stirred at 60°C for 2 hours, filtered, dried, and calcined at 550°C for 4 hours to obtain Fe-loaded zeolite.

[0048] Preparation Example 3.7 The preparation method of zeolite is different from that of Preparation Example 2.6 in that the zeolite is also pretreated, specifically: the zeolite is immersed in a 0.006 mol / L ferric nitrate solution, stirred at 60°C for 2 hours, filtered, dried, and calcined at 550°C for 4 hours to obtain Fe-loaded zeolite.

[0049] Example 1.1 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, comprising the following steps: The sewage was subjected to anaerobic treatment, anoxic treatment and aerobic treatment in sequence at a treatment temperature of 25°C. The hydraulic retention time of the anaerobic treatment was 1.5 h, the hydraulic retention time of the anoxic treatment was 1.5 h, and the hydraulic retention time of the aerobic treatment was 9 h. The zeolite prepared in Preparation Example 1.1 was added in an amount of 80 g / L into the anoxic zone. After the aerobic treatment, precipitation was carried out to obtain primary effluent and sludge. The sludge was returned to the anaerobic zone at a sludge return ratio of 80%. The sludge age was 14 days. The primary effluent was introduced into the MBBR zone for MBBR treatment. The average biomass of the biofilm in the MBBR zone was 1100 mg / L, the dissolved oxygen content was 4 mg / L, and the total gas volume was 0.18 m 3 / h, and after precipitation, nitrification liquid and effluent are obtained. The nitrification liquid is returned to the anoxic zone at a reflux ratio of 250% and undergoes anoxic treatment with the water in the anoxic zone. After 40 days of overall operation, the system is stable and the effluent quality is monitored.

[0050] Example 1.2 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, comprising the following steps: The sewage was subjected to anaerobic treatment, anoxic treatment and aerobic treatment in sequence at a treatment temperature of 25°C. The hydraulic retention time of the anaerobic treatment was 2h, the hydraulic retention time of the anoxic treatment was 4h, and the hydraulic retention time of the aerobic treatment was 6h. The zeolite prepared in Preparation Example 1.2 was added in an amount of 50g / L into the anoxic zone. After the aerobic treatment, precipitation was carried out to obtain primary effluent and sludge. The sludge was returned to the anaerobic zone at a sludge return ratio of 150%. The sludge age was 10d. The primary effluent was passed into the MBBR zone for MBBR treatment. The average biomass of the biofilm in the MBBR zone was 900mg / L, the content of dissolved oxygen was 3mg / L, and the total gas volume was 0.2m 3 / h, and after precipitation, nitrification liquid and effluent are obtained. The nitrification liquid is returned to the anoxic zone at a reflux ratio of 400% and undergoes anoxic treatment with the water in the anoxic zone. After 40 days of overall operation, the system is stable and the effluent quality is monitored.

[0051] Example 2.1 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that the addition amount of the zeolite prepared in Preparation Example 1.1 is 55 g / L, and the rest is the same as Example 1.1.

[0052] Example 2.2 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that the addition amount of the zeolite prepared in Preparation Example 1.1 is 60 g / L, and the rest is the same as Example 1.1.

[0053] Example 2.3 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that the addition amount of the zeolite prepared in Preparation Example 1.1 is 65 g / L, and the rest is the same as Example 1.1.

[0054] Example 2.4 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that the addition amount of the zeolite prepared in Preparation Example 1.1 is 70 g / L, and the rest is the same as Example 1.1.

[0055] Example 2.5 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that the addition amount of the zeolite prepared in Preparation Example 1.1 is 75 g / L, and the rest is the same as Example 1.1.

[0056] Example 3.1 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that when sludge is returned, the sludge return ratio is 50%, the sludge age is 20 days, and the rest is the same as Example 1.1.

[0057] Example 3.2 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that: when sludge is returned, the sludge return ratio is 200%, the sludge age is 40 days, and the rest is the same as Example 1.1.

[0058] Example 4.1 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that: in the MBBR treatment, the content of dissolved oxygen is 2 mg / L, and the total gas volume is 0.3 m 3 / h, and the rest are the same as in Example 1.1.

[0059] Example 4.2 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that: in the MBBR treatment, the content of dissolved oxygen is 5 mg / L, and the total gas volume is 0.1 m 3 / h, and the rest are the same as in Example 1.1.

[0060] Example 5.1 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that in the MBBR treatment, the average biomass of the biofilm is 800 mg / L, and the rest is the same as Example 1.1.

[0061] Example 5.2 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 1.1 in that in the MBBR treatment, the average biomass of the biofilm is 1200 mg / L, and the rest is the same as Example 1.1.

[0062] Examples 6.1-6.7 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 2.3 in that the zeolite prepared in Preparation Example 1.1 is replaced by the zeolites prepared in Preparation Examples 2.1-2.7 respectively, and the rest is the same as Example 2.3.

[0063] Examples 7.1-7.7 A method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification, which is different from Example 6.6 in that the zeolite prepared in Preparation Example 2.6 is replaced by the zeolites prepared in Preparation Examples 3.1-3.7 respectively, and the rest is the same as Example 6.6.

[0064] Comparative Example 1.1 The difference from Example 1.1 is that the addition amount of the zeolite prepared in Preparation Example 1.1 is 40 g / L, and the rest is the same as Example 1.1.

[0065] Comparative Example 1.2 The difference from Example 1.1 is that the addition amount of the zeolite prepared in Preparation Example 1.1 is 90 g / L, and the rest is the same as Example 1.1.

[0066] Comparative Example 1.3 The difference from Example 1.1 is that the zeolite obtained in Preparation Example 1.1 is removed, and the rest is the same as Example 1.1.

[0067] Comparative Example 1.4 The difference from Example 1.1 is that 80 g / L of zeolite prepared in Preparation Example 1.1 is also added into the aerobic zone, and the rest is the same as Example 1.1.

[0068] Comparative Example 2.1 The difference from Example 1.1 is that the hydraulic retention time of anaerobic treatment is 1 hour, the hydraulic retention time of anoxic treatment is 5 hours, and the hydraulic retention time of aerobic treatment is 4 hours. The rest is the same as Example 1.1.

[0069] Comparative Example 2.2 The difference from Example 1.1 is that the hydraulic retention time of anaerobic treatment is 3 hours, the hydraulic retention time of anoxic treatment is 1 hour, and the hydraulic retention time of aerobic treatment is 6 hours. The rest is the same as Example 1.1.

[0070] Performance Testing The TN and TP contents of the treatment methods of the embodiments and comparative examples after stable operation for 40 days were determined by spectrophotometry, and the TN removal rate and TP removal rate were calculated and recorded in Table 2. After stable operation for 100 days, the TN and TP contents were determined again, and the TN removal rate and TP removal rate were calculated and recorded in Table 2.

[0071] Table 2 Effluent water quality records Data Analysis: As can be seen from Table 2, the TP removal rate of the treatment method of Examples 1.1-1.2 after 40 days of stable operation is 98.10-98.11%, and the TN removal rate is 90.25-90.27%, which proves that the treatment method of the present application can further improve the TN removal rate while maintaining the TP removal rate at a high level, not only fully and efficiently utilizing the carbon source, overcoming the difficulty of low C / N, but also having good denitrification and dephosphorization effects.

[0072] The difference between Examples 2.1-2.5 and Example 1.1 is that the dosage of zeolite is changed, and the TP removal rate and TN removal rate of Example 2.3 are significantly higher than those of other examples, proving that the present application can more effectively supplement the carbon source, provide more adsorption sites, protect denitrifying bacteria, and enhance the stability and treatment effect of the system by strictly controlling the addition amount of zeolite to 65g / L. Ultimately, this improvement increased the TN removal rate to 90.78%.

[0073] The difference between Examples 3.1-5.2 is that the sludge return ratio and sludge age, the dissolved oxygen content and total gas volume, and the average biomass of the biofilm are changed respectively. The results show that the TP removal rate and the TN removal rate are significantly lower than those in Example 1.1, which proves that the present application ensures the activity of microorganisms in the system and enhances the stability and treatment capacity of the system by setting a reasonable sludge return ratio and sludge age during sludge return. By controlling the dissolved oxygen content and total gas volume in the MBBR treatment, the activity and metabolic efficiency of microorganisms on the biofilm are ensured, and the effective transfer and distribution of oxygen are optimized. By controlling the average biomass of the biofilm in the MBBR treatment within the range of 900-1100 mg / L, the removal efficiency of nitrogen and phosphorus in the present application is improved, ensuring that a sufficient number of microorganisms participate in the metabolic reaction, while avoiding the problem of system blockage or unstable operation caused by excessive biomass, thereby achieving efficient sewage denitrification and phosphorus removal.

[0074] The difference between Examples 6.1-6.7 and Example 2.3 is that the standing temperature during the preparation of zeolite is changed. The TP removal rate and TN removal rate of Example 6.6 are significantly higher than those of other examples, proving that the present application obtains zeolite with the best adsorption capacity by controlling the standing temperature, so that the denitrifying bacteria can exert their maximum efficacy, further improving the final TN removal rate.

[0075] The difference between Examples 7.1-7.7 and Example 6.6 is that Fe is added to the zeolite, and the TP removal rate and TN removal rate are significantly higher than those of Example 6.6, which proves that the present application enhances the structural stability of the zeolite by Fe loading treatment of the zeolite, reduces structural damage during use, ensures its long-term adsorption effect, and makes the treatment method of the present application have a more stable and efficient denitrification and phosphorus removal effect.

[0076] In Examples 7.1-7.7, the TP removal rate and TN removal rate of Example 7.4 after stable operation for 40 days are significantly higher than those of other examples. At the same time, the TP removal rate and TN removal rate of stable operation for 100 days are even higher than those of other examples. This proves that the present application strictly controls the concentration of the ferric nitrate solution so that the Fe-loaded zeolite finally obtained has both good structural stability and adsorption capacity. If the concentration of the ferric nitrate solution is too high and the trivalent iron ion loading is too high, the specific surface area and pore volume of the Fe-loaded zeolite will be reduced, which will damage its ability to stabilize denitrifying bacteria. If the concentration of the ferric nitrate solution is too low and the trivalent iron ion loading is too low, the structural stability cannot be improved well.

[0077] The difference between Comparative Examples 1.1-1.2 and Example 1.1 is that the dosage of zeolite is changed, and the TP removal rate and TN removal rate are significantly lower than those of Example 1.1, which proves that the present application more effectively supplements the carbon source by controlling the addition amount of zeolite, provides more adsorption sites, protects denitrifying bacteria, and enhances the stability and treatment effect of the system.

[0078] The difference between Comparative Example 1.3 and Example 1.1 is that the zeolite is removed, and the TN removal rate drops to less than 80%, which proves that the present application adds zeolite in the anoxic treatment, which plays a role in stabilizing denitrifying bacteria and supplementing carbon sources, thereby effectively improving the nitrogen removal and phosphorus removal efficiency of the system.

[0079] The difference between Comparative Examples 2.1-2.2 and Example 1.1 is that the hydraulic retention time is different, and the TP removal rate and TN removal rate are significantly lower than those of Example 1.1, which proves that the present application ensures the effective connection of each treatment stage by reasonably regulating the hydraulic retention time ratio of anaerobic treatment, anoxic treatment and aerobic treatment, and further improves the treatment effect of the entire system on high nitrogen and phosphorus content wastewater.

[0080] The embodiments of this specific implementation method are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore, all equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for treating wastewater by denitrification and denitrification, comprising the following steps: The sewage is sequentially subjected to anaerobic treatment, anoxic treatment and aerobic treatment to obtain primary effluent and sludge, the sludge is returned, the primary effluent is treated by MBBR, and nitrification liquid and effluent are obtained after precipitation, and the nitrification liquid is returned. It is characterized in that when the anoxic treatment is carried out, the system also includes zeolite with an addition amount of 50-80g / L; the hydraulic retention time ratio of the anaerobic treatment, the anoxic treatment and the aerobic treatment is 1: (1-2): (3-6).

2. The method for treating wastewater by nitrification and denitrification according to claim 1, characterized in that: When the anoxic treatment was performed, the amount of zeolite added was 65 g / L.

3. The method for treating wastewater by nitrification and denitrification according to claim 1, characterized in that: The sludge return ratio during the sludge return is 80-150%, and the sludge age is 10-14 days.

4. The method for treating wastewater by nitrification and denitrification according to claim 1, characterized in that: In the MBBR treatment, the dissolved oxygen content is 3-4 mg / L and the total gas volume is 0.18-0.2 m 3 / h.

5. The method for treating wastewater by nitrification and denitrification according to claim 1, characterized in that: In the MBBR treatment, the average biomass of the biofilm was 900-1100 mg / L.

6. The method for treating wastewater by nitrification and denitrification according to claim 1, characterized in that: The reflux ratio of the nitrifying liquid reflux is 250-400%.

7. The method for treating wastewater by nitrification and denitrification according to claim 1, characterized in that: The zeolite is prepared by the following method: The tetraethyl orthosilicate is hydrolyzed and then mixed with Al2(SO4)3·18H2O. The pH value in the system is adjusted to 9-11 and then stirred for 10-20 hours. The solid is allowed to stand at a temperature of 120-200°C. The solid is washed and dried, and then immersed in an alkaline solution and an acid solution in turn. The zeolite is obtained after filtering, drying and calcining.

8. The method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification according to claim 7, characterized in that: The temperature during the standing is 180°C.

9. The method for treating wastewater by nitrification and denitrification according to claim 1, characterized in that: The zeolite is also pretreated, specifically: The zeolite is immersed in a 0.001-0.005 mol / L ferric nitrate solution, stirred, filtered, dried, and calcined to obtain Fe-loaded zeolite.

10. The method for treating wastewater for nitrogen and phosphorus removal based on nitrification and denitrification according to claim 9, characterized in that: The concentration of the ferric nitrate solution is 0.004 mol / L.

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