Device and method for simultaneous nitrogen and phosphorus removal of low c / n sewage

Abstract

The application discloses a device and method for simultaneous nitrogen and phosphorus removal of low C / N sewage, and the device comprises a reactor main body, a first water distribution layer, a supporting layer, a front filter material layer, a second water distribution layer, a ferrous sulfide layer, a rear filter material layer and a water outlet layer are sequentially arranged in the reactor main body from bottom to top, a water inlet is arranged at the bottom of the reactor main body, and the water outlet layer is provided with a water outlet; the ferrous sulfide layer is arranged with ferrous sulfides with different particle sizes, and the particle sizes of the ferrous sulfides are sequentially 0.45-0.9 mm, 0.15-0.45 mm, less than 0.15 mm, 0.15-0.45 mm and 0.45-0.9 mm from bottom to top. After the ferrous sulfide layer is inoculated with sulfur, iron autotrophic denitrifying bacteria and heterotrophic denitrifying bacteria, the device for simultaneous nitrogen and phosphorus removal of low C / N sewage can be used for treating low C / N sewage. The application constructs a sulfur autotrophic-iron autotrophic-heterotrophic coupled denitrification system of three substrates of sulfur, iron and carbon, improves the nitrogen removal efficiency, realizes the simultaneous nitrogen and phosphorus removal of low C / N sewage under the condition that no external carbon source is added, and saves the treatment cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sewage treatment, and particularly relates to a device and method for simultaneous denitrification and phosphorus removal of low C / N sewage. BACKGROUND

[0002] Rural domestic sewage treatment is an important part of rural human settlement environment improvement, and denitrification and phosphorus removal is the key to sewage treatment. If not properly treated, it can easily cause water eutrophication, water quality deterioration and a series of problems. However, due to the fact that rural domestic sewage treatment facilities are mostly based on urban sewage treatment processes (such as A 2 O, AO, etc.), these treatment processes cannot adapt to the characteristics of low carbon-nitrogen ratio (C / N) of rural domestic sewage, resulting in difficulty in stabilizing total nitrogen to meet the standard, with a standard compliance rate of only 15-51%. Therefore, how to effectively remove nitrogen and phosphorus in low C / N sewage has become a problem to be solved.

[0003] At present, biological denitrification is a relatively economical and effective denitrification method. Heterotrophic denitrification using organic matter as an electron donor is the most common biological denitrification method. Denitrifying bacteria consume organic matter in sewage as an electron donor to realize the transformation of nitrate and nitrite to nitrogen under anaerobic or anoxic conditions, and has the advantages of fast growth rate and short domestication time.

[0004] Based on the principle of heterotrophic denitrification, a variety of mature processes have been developed and widely applied. However, for low C / N sewage, due to the lack of organic carbon source, the denitrifying bacteria cannot provide sufficient electron donor, resulting in low denitrification efficiency and non-compliance of total nitrogen in effluent.

[0005] It is generally believed that the C / N ratio in sewage should be greater than 5 to ensure efficient heterotrophic denitrification. When the C / N ratio is less than 5, external carbon source is needed to increase the C / N ratio. However, in actual operation, the addition of external carbon source not only increases the treatment cost, but also increases the production of excess sludge. If the amount of organic carbon source is not properly controlled, the COD of the effluent will be high.

[0006] In summary, low C / N sewage represented by rural domestic sewage is faced with problems such as low denitrification efficiency in the denitrification stage, non-compliance of total nitrogen in effluent, high cost of external carbon source and difficulty in controlling the amount of external carbon source.

[0007] The Chinese patent document with publication number CN 111875048 A discloses a self-sustaining and heterotrophic denitrification synergistic nitrogen and phosphorus removal reaction device, which comprises a reaction cavity, a sludge reaction zone (9), a pyrite layer (11), a green stone layer (12), and a supporting layer (4) arranged in the reaction cavity from top to bottom, a water inlet arranged at the bottom of the reaction cavity, a water outlet arranged at the upper part of the reaction cavity, and a sealing device arranged at the top of the reaction cavity. According to the embodiment 1, the total nitrogen concentration of the influent is 30 mg / L, the total phosphorus concentration of the influent is 1-2 mg / L, the total nitrogen of the effluent obtained by using the process is less than 10 mg / L, and the total phosphorus of the effluent is less than 0.5 mg / L. The process is not complete in removing nitrogen and phosphorus, and further deep denitrification and phosphorus removal treatment is required.

[0008] The Chinese patent document with publication number CN 115385446 A discloses a sulfur autotrophic and heterotrophic coupled denitrification device and method, which comprises a reactor main body, a water distribution layer, a supporting layer, a filter material layer, a reaction layer, a sedimentation layer, and a water outlet layer arranged in the reactor from bottom to top; the filter material layer is arranged with special filter material, and the special filter material is attached with sulfur autotrophic denitrifying bacteria and heterotrophic denitrifying bacteria; the mass percentage of each component of the special filter material is: sulfur 60-80%, prismatic pyrite 15%, green stone powder 10%, activated carbon 1-5%, and adhesive 5-10%. Additional carbon source needs to be added during the treatment process.

[0009] Nitrite nitrogen (NO2 - -N) as an intermediate product of the denitrification process not only poses a serious threat to biological and human health, but also has a toxic effect on denitrifying bacteria, seriously inhibiting the denitrification process, and further damaging the normal operation of the conventional wastewater biological treatment process. In addition, in the conventional denitrification process, a large amount of NO2 - -N accumulates in the wastewater, which is re-oxidized to nitrate nitrogen (NO3 - -N) in the subsequent aerobic reactor, increasing the oxygen demand for denitrification, not only causing the treatment effect to decline, but also wasting energy. SUMMARY

[0010] The present application provides a device and method for simultaneous nitrogen and phosphorus removal from low C / N wastewater, which can completely remove nitrogen and phosphorus without the need for further deep denitrification and phosphorus removal, and the content of nitrite nitrogen in the treated effluent is low.

[0011] The technical solution of the present application is as follows:

[0012] The first aspect of the present application provides a device for simultaneous nitrogen and phosphorus removal of low C / N sewage, comprising a reactor main body, wherein a first water distribution layer, a supporting layer, a front filter material layer, a second water distribution layer, a ferrous sulfide layer, a rear filter material layer and a water outlet layer are sequentially arranged in the reactor main body from bottom to top; the reactor main body is provided with a water inlet at the bottom, and the water outlet layer is provided with a water outlet.

[0013] The ferrous sulfide layer is arranged with ferrous sulfide of different particle sizes; in the ferrous sulfide layer, the particle sizes of the ferrous sulfide are 0.45-0.9 mm, 0.15-0.45 mm, less than 0.15 mm, 0.15-0.45 mm and 0.45-0.9 mm from bottom to top.

[0014] After the ferrous sulfide layer is inoculated with sulfur autotrophic denitrifying bacteria, iron autotrophic denitrifying bacteria and heterotrophic denitrifying bacteria, the device for simultaneous nitrogen and phosphorus removal of low C / N sewage can be used for treating low C / N sewage.

[0015] The low C / N sewage to be treated enters the reactor from the bottom of the reactor, and realizes denitrification under the synergistic denitrification of the sulfur autotrophic denitrifying bacteria, the iron autotrophic denitrifying bacteria and the heterotrophic denitrifying bacteria in the ferrous sulfide layer; at the same time, iron reacts with phosphate to realize phosphorus removal.

[0016] The low C / N nitrate sewage to be treated enters the reactor from the bottom of the reactor main body, is uniformly distributed by the first water distribution layer, and then sequentially flows through the supporting layer and the front filter material layer, so that the solid particulate matters in the sewage are intercepted by the filter material; then, the uniformly distributed water reenters the ferrous sulfide layer after being uniformly distributed again by the second water distribution plate; in the ferrous sulfide layer, the sulfur autotrophic denitrifying bacteria and the iron autotrophic denitrifying bacteria respectively use sulfur and iron in the ferrous sulfide as electron donors and nitrate as electron acceptor to perform autotrophic denitrification; the heterotrophic denitrifying bacteria use organic matters in the sewage as electron donors and nitrate as electron acceptor to perform heterotrophic denitrification; the ferrous ions released by the ferrous sulfide in water and the iron ions and phosphate ions generated by the iron autotrophic denitrification react to form a precipitate, thereby realizing simultaneous phosphorus removal.

[0017] In the process of sulfur and iron autotrophic denitrification, NO3 - is converted to NO2 - slowly, NO2 - is converted to N2 quickly; in the process of heterotrophic denitrification, NO3 - is converted to NO2 - quickly, and NO2 - is converted to N2 slowly; coupling the two processes forms complementation, improves the reaction rate of each stage of denitrification, and further improves the overall denitrification efficiency.

[0018] The ferrous sulfide layer in the application is specially designed. If only large-particle ferrous sulfide is used, the specific surface area of the ferrous sulfide is small, which is not conducive to the adhesion and reproduction of denitrifying bacteria, resulting in poor treatment effect; if only small-particle ferrous sulfide is used, the porosity of the ferrous sulfide reaction layer is low, which is prone to blockage and dead zones, and also leads to poor treatment effect, increases the frequency of reactor maintenance and improves the operation difficulty. In view of this, the design of the ferrous sulfide particle size gradient change in the application not only ensures a high specific surface area, but also reduces the probability of blockage, realizes stable, efficient and low-energy consumption treatment of low C / N sewage, and completely removes nitrate and phosphorus in the effluent, so that deep treatment is not needed, and the content of nitrite nitrogen in the effluent is low, and there is no accumulation of nitrite nitrogen.

[0019] The water inlet is connected to a sewage tank for storing sewage through a water inlet pump and a pipeline.

[0020] The first water distribution layer is provided with a first water distribution plate, and the first water distribution plate is uniformly provided with circular holes with an opening rate of 20-25%.

[0021] The first water distribution layer is used for uniformly distributing the sewage into the supporting layer.

[0022] The supporting layer is arranged with cobblestones, and the filling height accounts for 8-12% of the total working height.

[0023] The supporting layer is used for supporting the front filter material layer.

[0024] The front filter material layer comprises a first filter material layer and a second filter material layer; the first filter material layer is arranged with zeolite, and the filling height accounts for 8-12% of the total working height; and the second filter material layer is arranged with quartz sand, and the filling height accounts for 10-15% of the total working height.

[0025] The first filter material layer is used for preliminarily filtering and removing large solid particles in the sewage, and the second filter material layer is used for further filtering and removing small solid particles in the sewage.

[0026] The second water distribution layer is provided with a second water distribution plate, and the second water distribution plate is uniformly provided with circular holes with an opening rate of 15-20%.

[0027] The second water distribution layer is used for uniformly distributing the sewage into the ferrous sulfide layer.

[0028] In the ferrous sulfide layer, the filling heights of ferrous sulfides with different particle sizes from bottom to top account for 3-5%, 5-8%, 10-15%, 5-8% and 3-5% of the total working height, respectively.

[0029] The screening step of ferrous sulfide particles is as follows: the blocky ferrous sulfide is put into a ball mill for grinding, then is screened with screens with pore diameters of 0.9 mm, 0.45 mm and 0.15 mm in sequence to obtain ferrous sulfide particles with different particle sizes, then the ferrous sulfide particles with different particle sizes are respectively soaked in a dilute hydrochloric acid solution for 12-48 h, and finally are rinsed with water.

[0030] The rear filter layer comprises a third filter layer and a fourth filter layer; the third filter layer is arranged with zeolite, and the filling height accounts for 8-12% of the total working height, which is used for preventing the ferrous sulfide from being disturbed upward by water flow, and preliminarily filtering the ferrous sulfide and the active sludge with large particle sizes.

[0031] The fourth filter layer is arranged with glass wool, and the filling height accounts for 8-12% of the total working height, which is used for filtering the ferrous sulfide and the active sludge with small particle sizes.

[0032] Preferably, the effluent layer is arranged with pH and temperature on-line monitoring devices, which are used for monitoring the pH and temperature of the reaction system in real time, and ensuring that the pH and temperature are within the range suitable for the growth and metabolism of the sulfur- and iron-autotrophic denitrifying bacteria and the heterotrophic denitrifying bacteria; the effluent layer is arranged with an effluent outlet connected to a clean water pool through an effluent pipeline.

[0033] Preferably, the reactor body is provided with an air outlet at the top, which is used for collecting gas samples and detecting the concentrations of nitrogen and hydrogen sulfide.

[0034] Preferably, the reactor body is provided with a heat preservation layer on the outer wall, which is used for maintaining the temperature inside the reactor body stable.

[0035] Preferably, the reactor body is provided with a drain outlet at the bottom, and the drain outlet is connected with a drain valve and a drain pipeline, which are used for emptying the internal sewage when the reactor is overhauled and maintained.

[0036] In the second aspect, the present application provides a method for denitrification and phosphorus removal based on a device for simultaneous denitrification and phosphorus removal of low C / N sewage, which comprises the following steps:

[0037] (1) inoculating the sulfur autotrophic denitrifying bacteria, the iron autotrophic denitrifying bacteria and the heterotrophic denitrifying bacteria in the ferrous sulfide layer;

[0038] (2) introducing the low C / N sewage to be treated into the reactor body from the water inlet at the bottom of the reactor body, and realizing denitrification under the synergistic denitrification of the sulfur autotrophic denitrifying bacteria, the iron autotrophic denitrifying bacteria and the heterotrophic denitrifying bacteria; and realizing phosphorus removal through the reaction of iron ions and phosphate.

[0039] In the ferrous sulfide layer, the sulfur autotrophic denitrifying bacteria and the iron autotrophic denitrifying bacteria take the sulfur and the iron in the ferrous sulfide as the electron donors and take the nitrate as the electron acceptor to perform autotrophic denitrification; the heterotrophic denitrifying bacteria take the organic matter in the sewage as the electron donor and take the nitrate as the electron acceptor to perform heterotrophic denitrification; the ferrous ions released by the ferrous sulfide in the water and the iron ions and the phosphate ions generated by the iron autotrophic denitrification react to form a precipitate, thereby realizing simultaneous phosphorus removal.

[0040] Preferably, the step (1) comprises:

[0041] (1-1) obtaining anaerobic activated sludge, and inoculating the anaerobic activated sludge into the sulfur iron autotrophic denitrification medium and the heterotrophic denitrification medium respectively to obtain sulfur and iron autotrophic denitrification sludge and heterotrophic denitrification sludge;

[0042] (1-2) inoculating the sulfur and iron autotrophic denitrification sludge and the heterotrophic denitrification sludge into the ferrous sulfide layer according to the total suspended solid (TSS) mass of the sludge after domestication by equal sludge mass;

[0043] (1-3) using low C / N ratio simulated sewage as influent to perform biofilm formation, and performing the step (2) after the biofilm formation is successful.

[0044] Preferably, in the step (2), the pH value in the reaction system is maintained at 6-8, and the temperature is maintained at 25-35℃.

[0045] Preferably, in the step (2), the hydraulic retention time in the reactor body is 0.5-4h, and the effluent meets the discharge standard.

[0046] Preferably, the C / N of the low C / N sewage to be treated is 1-4.

[0047] Further, in the low C / N sewage to be treated, the nitrate nitrogen concentration is 1-100mg / L, and the phosphate concentration is 0.5-5mg / L.

[0048] Further preferably, in the low C / N sewage to be treated, the nitrate nitrogen concentration is 10-50mg / L, and the phosphate concentration is 0.5-5mg / L.

[0049] Compared with the prior art, the present application has the following beneficial effects:

[0050] (1) The present application takes the sulfur and the iron in the ferrous sulfide and the organic matter in the sewage as the electron donors to construct a sulfur autotrophic-iron autotrophic-heterotrophic coupled denitrification system of three substrates of sulfur, iron and carbon, and does not need any form of external carbon source, thereby saving 100% of the external carbon source, reducing the operation cost, and improving the denitrification efficiency.

[0051] (2) In this invention, the ferrous ions released by ferrous sulfide in water and the ferric ions generated by iron autotrophic denitrification can react with phosphate ions to form precipitates, thereby achieving simultaneous phosphorus removal.

[0052] (3) The sulfur autotrophic-iron autotrophic-heterotrophic coupled denitrification system constructed in this invention utilizes the NO3- in the heterotrophic denitrification process. - To NO2 - Rapid conversion and sulfur-iron autotrophic denitrification process NO2 - The mechanism of rapid conversion to N2 couples the two to form a complementary relationship, which improves the reaction rate of each stage of denitrification and thus greatly enhances the overall nitrogen removal efficiency.

[0053] (4) The sulfur autotrophic-iron autotrophic-heterotrophic coupled denitrification system constructed in this invention utilizes the mechanism of acid production by iron autotrophic denitrification and alkali production by sulfur autotrophic and heterotrophic denitrification to form an acid-base balance during the denitrification reaction without the need for additional pH adjustment.

[0054] (5) The device of the present invention has a simple structure and is easy to operate. The ferrous sulfide used as a sulfur source and iron source does not need to be modified, is easy to obtain, has a rough surface, and is easy for bacteria to attach. The method provided for treating low C / N wastewater and simultaneously removing nitrogen and phosphorus has low operating cost and strong practicality.

[0055] (6) The design of the ferrous sulfide particle size gradient in this invention ensures a high specific surface area, thoroughly removes nitrates and phosphorus from the treated water without requiring further deep treatment, and simultaneously reduces nitrite nitrogen (NO2) in the effluent. - The low C / N content reduces the probability of clogging, and no clogging has occurred during long-term operation, achieving stable, efficient, and low-energy treatment of low C / N wastewater. Attached Figure Description

[0056] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0057] Figure 1 This is a schematic diagram of the structure of the ferrous sulfide-enhanced ferrous sulfide autotrophic-heterotrophic coupled denitrification treatment device for low C / N wastewater synchronous denitrification and phosphorus removal according to the present invention. The specific device consists of the following components: wastewater tank (1), inlet pump (2), outlet (3), first water distribution plate (4), support layer (5), first filter layer (6), second filter layer (7), second water distribution plate (8), ferrous sulfide layer (9), third filter layer (10), fourth filter layer (11), effluent layer (12), outlet (13), air outlet (14), pH online monitoring device (15), temperature online monitoring device (16), and insulation layer (17).

[0058] Figure 2is the change graph of effluent nitrate concentration when the embodiment 1 of the present application uses ferrous sulfide with gradient change of particle size to strengthen the sulfur-iron autotrophic and heterotrophic coupled denitrification device to treat low C / N ratio simulated domestic sewage nitration liquid;

[0059] Figure 3 is the change graph of effluent nitrate, nitrite and phosphate concentrations when the embodiment 2 of the present application uses ferrous sulfide with gradient change of particle size to strengthen the sulfur-iron autotrophic and heterotrophic coupled denitrification device to treat low C / N ratio nitration liquid in a rural domestic sewage treatment facility;

[0060] Figure 4 is the change graph of effluent nitrate, nitrite and phosphate concentrations when the comparative example 1 of the present application uses single larger particle size (0.9-1mm) ferrous sulfide to strengthen the sulfur-iron autotrophic and heterotrophic coupled denitrification device to treat low C / N ratio nitration liquid in a rural domestic sewage treatment facility. DETAILED DESCRIPTION

[0061] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The present application is further described in conjunction with the accompanying drawings and examples.

[0062] In one embodiment of the present application, as shown in Figure 1 The device for simultaneously removing nitrogen and phosphorus by using ferrous sulfide to strengthen sulfur-iron autotrophic and heterotrophic coupled denitrification to treat low C / N sewage according to the present application comprises a sewage tank (1) and a reactor main body, and the reactor is internally provided with a first water distribution layer (4), a supporting layer (5), a first filter material layer (6), a second filter material layer (7), a second water distribution layer (8), a ferrous sulfide layer (9), a third filter material layer (10), a fourth filter material layer (11), and a water outlet layer (12) from bottom to top.

[0063] The sewage tank (1) is used for collecting low C / N ratio nitrate sewage, and is connected with the reactor main body through a water inlet pipe. A water inlet pump (2) is used to pump the sewage from the bottom of the reactor main body into the reactor.

[0064] The first water distribution layer (4) is provided with a water distribution plate, which is in the form of a uniformly distributed circular hole structure with an opening rate of 20-25%, and is used for uniformly distributing the sewage into the supporting layer.

[0065] The supporting layer (5) is arranged with pebbles, and the filling height accounts for 10% of the total working height, and is used for supporting the first filter material layer (6) and the second filter material layer (7).

[0066] The first filter layer (6) is arranged with zeolite, and the filling height accounts for 10% of the total working height, which is used for preliminary filtration to remove larger solid particles in sewage.

[0067] The second filter layer (7) is arranged with quartz sand, and the filling height accounts for 13% of the total working height, which is used for further filtration to remove small solid particles in sewage.

[0068] The second water distribution layer (8) is provided with a water distribution plate, which is a uniformly distributed circular hole structure with an opening rate of 15-20%, and is used for uniformly distributing sewage into the ferrous sulfide layer.

[0069] The ferrous sulfide layer (9) is arranged with ferrous sulfide with different particle sizes, and the particle sizes of the ferrous sulfide from bottom to top are 0.45-0.9mm, 0.15-0.45mm, less than 0.15mm, 0.15-0.45mm, and 0.45-0.9mm, and the filling heights from bottom to top account for 3.8%, 6.7%, 12.3%, 6.7%, and 3.8% of the total working height, respectively. The particle size screening steps of the ferrous sulfide are as follows: the blocky ferrous sulfide is put into a ball mill for sufficient grinding, then the ferrous sulfide is screened with screens with hole diameters of 0.9mm, 0.45mm, and 0.15mm in sequence to obtain ferrous sulfides with different particle sizes, then the ferrous sulfides with different particle sizes are soaked in dilute hydrochloric acid solution for 48h, and finally the ferrous sulfides are washed clean with water.

[0070] The third filter layer (10) is arranged with zeolite, and the filling height accounts for 10% of the total working height, which is used for preventing the ferrous sulfide from being disturbed upward by water flow, and for preliminarily filtering ferrous sulfides with larger particle sizes and sloughed activated sludge.

[0071] The fourth filter layer (11) is arranged with glass wool, and the filling height accounts for 10% of the total working height, which is used for filtering ferrous sulfides with smaller particle sizes and sloughed activated sludge.

[0072] The effluent layer (12) is arranged with a pH online monitoring device (15) and a temperature online monitoring device (16) for real-time monitoring of the pH and temperature of the reaction system, ensuring that the pH is within the range of 6-8 and the temperature is within the range of 25-35℃. The effluent layer is arranged with an effluent outlet (13) connected to a clean water pool through an effluent pipeline.

[0073] The reactor main body is provided with a gas outlet (14) at the top for collecting gas samples to detect the concentrations of nitrogen and hydrogen sulfide, and to prevent hydrogen sulfide from exceeding the standard.

[0074] The reactor main body is provided with a drain outlet (3) at the bottom, and a drain valve and a drain pipe are connected to the drain outlet, which is used to empty the internal sewage when the reactor is overhauled and maintained.

[0075] The working principle of the reactor is as follows:

[0076] The nitrate wastewater to be treated enters the inside of the reactor from the bottom of the reactor, is uniformly distributed by the water distribution plate, then flows through the supporting layer, the first filter material layer and the second filter material layer in sequence, the solid particles in the wastewater are intercepted by the filter material, then is uniformly distributed again by the water distribution plate, and enters the ferrous sulfide layer. In the ferrous sulfide layer, the sulfur autotrophic denitrifying bacteria and the iron autotrophic denitrifying bacteria respectively take the sulfur and iron in the ferrous sulfide as the electron donor and the nitrate as the electron acceptor to perform autotrophic denitrification. The heterotrophic denitrifying bacteria take the organic matter in the wastewater as the electron donor and the nitrate as the electron acceptor to perform heterotrophic denitrification. The ferrous ions released by the ferrous sulfide in water and the iron ions and phosphate ions generated by the iron autotrophic denitrification react to form a precipitate, thereby realizing simultaneous phosphorus removal. The alkalinity generated in the sulfur autotrophic and heterotrophic denitrification processes can effectively supplement the alkalinity consumed in the iron autotrophic denitrification process, thereby balancing the pH.

[0077] The debugging and running mode of the device for treating low C / N wastewater by using ferrous sulfide to strengthen sulfur-iron autotrophic and heterotrophic coupled denitrification for simultaneous denitrification and phosphorus removal in the embodiment is as follows:

[0078] Step one: The activated sludge is taken from the anaerobic tank or anaerobic zone of the biochemical treatment process of the municipal wastewater treatment plant, is divided into two identical anaerobic tanks, is left to stand for 1 day to degrade the liquid-phase organic matter, the supernatant is discarded, and then the sulfur-iron autotrophic denitrification medium and the heterotrophic denitrification medium are respectively added to perform domestication. The medium is replaced every 2 days. Before replacement, the stirring is stopped, the sludge is left to stand, the supernatant is discarded after the sludge is precipitated, and the same volume of new medium as the supernatant is added. The oxygen is removed to form an anaerobic environment. The anaerobic tank is sealed and is cultured at 30℃. When the nitrate removal rate is stably above 80%, it is considered that the domestication is completed.

[0079] The sulfur-iron autotrophic denitrification medium is composed of Na2S2O3·5H2O, FeSO4·7H2O, NaNO3, KH2PO4, NH4Cl, NaHCO3 and MgCl2·6H2O; and the heterotrophic denitrification medium is composed of CH3COONa, NaNO3, KH2PO4, NH4Cl, FeSO4·7H2O and MgSO4·7H2O.

[0080] Step two: According to the total suspended solid (TSS) mass of the sludge after domestication, the sulfur-iron autotrophic denitrification sludge and the heterotrophic denitrification sludge after domestication are inoculated into the ferrous sulfide layer of the reactor at equal sludge mass.

[0081] Step three: The simulated domestic wastewater nitration liquid with a C / N ratio of 3 is used as the influent to perform biofilm formation. The hydraulic retention time is set to 2h. The NO3 - -N concentration is 40mg / L, the PO4 3- -P concentration is 2mg / L. When the effluent NO3 - -N concentration is stably less than 5mg / L, the PO4 3-When the P concentration is less than 0.5 mg / L, it is considered that the biofilm formation is completed, and the sewage treatment can be carried out.

[0082] The simulated domestic sewage nitrification liquid is composed of CH3COONa, NaNO3, KH2PO4, CaCl2·2H2O, MgSO4·7H2O and trace element nutrient solution.

[0083] In another embodiment of the present application, a method for simultaneous denitrification and phosphorus removal of low C / N sewage by using ferrous sulfide to strengthen sulfur-iron autotrophic heterotrophic coupled denitrification is provided. The nitrate sewage to be treated enters the inside of the reactor from the bottom of the reactor, is uniformly distributed by the water distribution plate, and then flows through the supporting layer, the first filter material layer and the second filter material layer in turn. The solid particulate matters in the sewage are intercepted by the filter material, and then are uniformly distributed again by the water distribution plate and enter the ferrous sulfide layer. In the ferrous sulfide layer, the sulfur autotrophic denitrifying bacteria and the iron autotrophic denitrifying bacteria respectively use sulfur and iron in the ferrous sulfide as the electron donor and nitrate as the electron acceptor to perform autotrophic denitrification. The heterotrophic denitrifying bacteria use the organic matters in the sewage as the electron donor and nitrate as the electron acceptor to perform heterotrophic denitrification. The ferrous ions released by the ferrous sulfide in water and the iron ions and phosphate ions generated by the iron autotrophic denitrification react to form a precipitate, so that the simultaneous phosphorus removal is realized. In the sulfur-iron autotrophic denitrification process, NO3 - is converted to NO2 - slowly, NO2 - is converted to N2 quickly. The heterotrophic denitrification process is opposite to the above process, NO3 - is converted to NO2 - quickly, and NO2 - is converted to N2 slowly. The coupling of the two processes forms complementation, improves the reaction rate of each stage of denitrification, and further improves the overall denitrification efficiency.

[0084] The method for using ferrous sulfide to strengthen sulfur-iron autotrophic heterotrophic coupled denitrification in the embodiment constructs a sulfur autotrophic-iron autotrophic-heterotrophic coupled denitrification system of three substrates of sulfur, iron and carbon, improves the denitrification efficiency, and realizes the simultaneous denitrification and phosphorus removal of low C / N sewage without additional carbon source.

[0085] Example 1

[0086] Three reactors which are completely same are prepared and are named as R1, R2 and R3. 100 mL of sulfur-iron autotrophic denitrification sludge is inoculated into the ferrous sulfide layer of the R1 reactor, 100 mL of heterotrophic denitrification sludge is inoculated into the ferrous sulfide layer of the R2 reactor, and 50 mL of sulfur-iron autotrophic denitrification sludge and 50 mL of heterotrophic denitrification sludge are inoculated into the ferrous sulfide layer of the R3 reactor. The TSS of the sulfur-iron autotrophic denitrification sludge and the heterotrophic denitrification sludge is approximately equal, which is 9.2 g / L. After inoculation, the simulated domestic sewage nitrification liquid with a C / N ratio of 2 is used as the influent, and the initial NO3 -The concentration of N is 40 mg / L, the hydraulic retention time is set to 1 h, the effluent is collected into the influent tank and then pumped into the reactor for continuous reaction, and the above operation is repeated until the reaction is 12 h.

[0087] As shown in Figure 2 Figure 3, the sulfur-iron autotrophic heterotrophic coupling group (R3) NO3 - The removal effect of N is the best, followed by the heterotrophic group (R2), the autotrophic group (R1) NO3 - The removal effect of N is the worst, and the sulfur-iron autotrophic heterotrophic coupling can effectively improve the denitrification reaction rate and NO3 - The removal rate of N.

[0088] Example 2

[0089] The nitrification liquid in a rural domestic sewage treatment facility has a C / N ratio of 1.8-2.9, and the concentration of NO3 - The concentration of N is 30-42 mg / L, and the concentration of PO4 3- The concentration of P is 1.4-2.3 mg / L, and the sulfur-iron autotrophic heterotrophic coupling denitrification and simultaneous nitrogen and phosphorus removal device with gradient change of particle size of ferrous sulfide is used to treat the sewage, the hydraulic retention time is 2 h, and continuous operation is performed for 20 days, as shown in Figure 3 The concentration of NO3 - The concentration of N is less than 1.54 mg / L, and the average value is 0.34 mg / L, the concentration of NO2 - The concentration of N is less than 4.58 mg / L, and the average value is 3.34 mg / L, the concentration of nitrite is low, and the concentration of PO4 3- The concentration of P is below the detection limit, and the pH value of the water body during the operation is 7.8-7.9, and the pH value is stable.

[0090] Comparative Example 1

[0091] The sulfur-iron autotrophic heterotrophic coupling denitrification and simultaneous nitrogen and phosphorus removal device in Example 2 is replaced by a single larger particle size (0.9-1 mm) ferrous sulfide layer, and the other conditions are the same as in Example 2, the hydraulic retention time is 2 h, and continuous operation is performed for 20 days, as shown in Figure 4 The concentration of NO3 - The concentration of N is 7.12-19.92 mg / L, and the average value is 11.77 mg / L, the removal effect of nitrate is poor, the concentration of NO2 - The concentration of N is 8.82-19.8 mg / L, and the average value is 14.72 mg / L, the concentration of nitrite is high, and the concentration of PO4 3- The concentration of P is below the detection limit to 1.3 mg / L, and the average value is 0.32 mg / L, and the removal effect of phosphate is poor in stability.

[0092] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments and applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

[0093] The accompanying drawings show structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not drawn to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

Claims

1. A device for simultaneous nitrogen and phosphorus removal from low C / N sewage, characterized in that, The reactor body is internally sequentially provided from bottom to top with a first water distribution layer, a supporting layer, a front filter layer, a second water distribution layer, a ferrous sulfide layer, a rear filter layer and a water outlet layer; the reactor body bottom is provided with a water inlet, and the water outlet layer is provided with a water outlet; The ferrous sulfide layer is arranged with ferrous sulfide of different particle sizes; in the ferrous sulfide layer, the particle sizes of the ferrous sulfide are sequentially 0.45-0.9 mm, 0.15-0.45 mm, less than 0.15 mm, 0.15-0.45 mm and 0.45-0.9 mm from bottom to top. In the ferrous sulfide layer, the filling heights of the ferrous sulfide of different particle sizes sequentially account for 3-5%, 5-8%, 10-15%, 5-8% and 3-5% of the total working height from bottom to top.

2. The device for simultaneous nitrogen and phosphorus removal from low C / N sewage according to claim 1, characterized in that, The first water distribution layer is provided with a first water distribution plate, and the first water distribution plate is uniformly distributed with round holes with an opening rate of 20-25%; the second water distribution layer is provided with a second water distribution plate, and the second water distribution plate is uniformly distributed with round holes with an opening rate of 15-20%.

3. The device for simultaneous nitrogen and phosphorus removal from low C / N sewage according to claim 1, characterized in that, The supporting layer is arranged with cobblestones, and the filling height accounts for 8-12% of the total working height.

4. The device for simultaneous nitrogen and phosphorus removal from low C / N sewage according to claim 1, characterized in that, The front filter layer includes a first filter layer and a second filter layer; the first filter layer is arranged with zeolite, and the filling height accounts for 8-12% of the total working height; the second filter layer is arranged with quartz sand, and the filling height accounts for 10-15% of the total working height.

5. The device for simultaneous nitrogen and phosphorus removal from low C / N sewage according to claim 1, characterized in that, The rear filter layer includes a third filter layer and a fourth filter layer; the third filter layer is arranged with zeolite, and the filling height accounts for 8-12% of the total working height; the fourth filter layer is arranged with glass wool, and the filling height accounts for 8-12% of the total working height.

6. The device for simultaneous denitrification and phosphorus removal of low C / N sewage according to claim 1, characterized in that, The water outlet layer is arranged with pH and temperature online monitoring devices.

7. A method for denitrification and dephosphorization based on the device for simultaneous denitrification and dephosphorization of low C / N sewage according to any one of claims 1-6, characterized in that, The method comprises: (1) inoculating sulfur autotrophic denitrifying bacteria, iron autotrophic denitrifying bacteria and heterotrophic denitrifying bacteria in the ferrous sulfide layer; (2) introducing the low C / N wastewater to be treated into the reactor body from the water inlet at the bottom of the reactor body, so that the denitrification is realized under the synergistic denitrification of the sulfur autotrophic denitrifying bacteria, the iron autotrophic denitrifying bacteria and the heterotrophic denitrifying bacteria; the iron ions react with the phosphate to realize the phosphorus removal.

8. The method of denitrification and dephosphorization according to claim 7, characterized by, Step (1) comprises: (1-1) obtaining anaerobic activated sludge, and respectively domesticating the sludge with a sulfur-iron autotrophic denitrification medium and a heterotrophic denitrification medium to obtain sulfur, iron autotrophic denitrification sludge and heterotrophic denitrification sludge; (1-2) inoculating the domesticated sulfur-iron autotrophic denitrification sludge and the heterotrophic denitrification sludge into the ferrous sulfide layer according to the total suspended solid mass of the sludge after domestication; (1-3) using low C / N ratio simulated wastewater as the influent to carry out biofilm formation, and carrying out step (2) after the biofilm formation is successful.

9. The method of denitrification and phosphorus removal according to claim 7, characterized in that, In step (2), the hydraulic retention time in the reactor body is 0.5-4 h, and the effluent meets the discharge standard.

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