A treatment device and method for accelerating start-up of autotrophic denitrification of pyrite

Abstract

The application relates to a treatment device and method capable of accelerating the start of pyrite autotrophic denitrification, and belongs to the technical field of sewage treatment. 3+ The dosing unit comprises Fe 3+ The dosing tank (4) and the dosing pump (6); the water inlet unit is a raw water tank (3) provided with an aeration head (2), the aeration head (2) is connected with a nitrogen cylinder (1) through a valve, modified pyrite filler particles and modified ceramsite are filled in the reactor, the bottom of the reactor is connected with an aeration pump, Fe 3+ The dosing tank (4) is connected with the water inlet (7) at the bottom of the reactor (13) through the dosing pump (6). The nature sludge is aerated, static and discharged, then water treated by nitrogen aeration and added with ferric iron is used for accelerating the reaction. The technology can rapidly start in more than 10 days.

Description

Technical Field

[0001] This invention relates to the field of denitrification technology, specifically to a treatment device and method for accelerating the start-up of autotrophic denitrification in pyrite. Background Technology

[0002] Traditional biological denitrification processes are primarily based on heterotrophic denitrification to remove total nitrogen. However, when applied to advanced wastewater treatment plants, the low C / N ratio in the effluent leads to insufficient carbon sources. To effectively remove TN, a large amount of organic matter needs to be added, which significantly increases operating costs. Furthermore, effectively adding organic matter becomes a challenge when water quality fluctuates. Overdosing results in waste and affects effluent quality, while insufficient dosing fails to achieve the desired denitrification effect.

[0003] Pyrite (FeS2) autotrophic denitrification requires no external carbon source; it generates Fe during nitrogen removal. 3+ The pyrite can react with Fe(OH)3, forming a precipitate that combines with phosphorus in the water, thus achieving simultaneous nitrogen and phosphorus removal. Pyrite is readily available, has low raw material and operating costs, produces little sludge, is highly efficient, and has a simple process. Pyrite autotrophic denitrification consumes little alkalinity and produces low levels of sulfate during the reaction, and it can achieve simultaneous nitrogen and phosphorus removal during denitrification, making it a highly attractive technology.

[0004] However, autotrophic denitrification systems built using pyrite as a substrate have certain problems. Pyrite is a solid and is not easily utilized by microorganisms in wastewater, resulting in slow microbial growth, slow reactor start-up, long system retention time, and relatively low nitrogen removal efficiency. Therefore, it is essential to explore an autotrophic denitrification process using pyrite that allows for rapid start-up.

[0005] To address the issue of slow microbial growth, based on preliminary small-scale test results, the autotrophic denitrification system using elemental sulfur as the sulfur source exhibits rapid microbial growth and a short system start-up period.

[0006] To address issues such as low denitrification rates, literature reports that redox mediators, acting as electron carriers, can accelerate the transfer of electrons from electron donors to final electron acceptors through the cyclic conversion of their oxidized and reduced states. This can increase the reaction rate by one to several orders of magnitude, accelerating the conversion of pollutants, such as the reduction of nitrate nitrogen. Common redox mediators mainly include some quinones and riboflavin.

[0007] To address the difficulty in utilizing pyrite, literature reports indicate that microbial oxidation of pyrite includes both direct and indirect oxidation mechanisms. Direct oxidation primarily involves the oxidation of pyrite by oxygen. Indirect oxidation, on the other hand, involves the oxidation of Fe... 3+ Oxidize pyrite to produce Fe 2+Sodium thiosulfate, through which microorganisms utilize and reduce NO3. - into N2, Fe 2+ In an oxygen-deficient environment, it is affected by NO3. - Oxidation to produce Fe 3+ And so it goes on and on.

[0008]

[0009]

[0010]

[0011] Bioleaching of pyrite is mainly through indirect oxidation.

[0012] Based on this, this application utilizes sulfur to enrich denitrifying thiobacilli and then adds Fe... 3+ This promotes the dissolution process of pyrite, and then, under the redox medium, increases the denitrification rate, thereby accelerating the start-up of the pyrite autotrophic denitrification reactor. Summary of the Invention

[0013] In view of the shortcomings of the prior art, the present invention relates to a treatment device and its application that can accelerate the start-up of autotrophic denitrification of pyrite.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a treatment device for accelerating the start-up of autotrophic denitrification of pyrite, comprising an inlet water unit, Fe... 3+ Dosing unit, reactor, modified pyrite packing particles, modified ceramsite; Fe 3+ The dosing unit includes Fe 3+ Dosing tank (4) and dosing pump (6);

[0015] The water inlet unit is a raw water tank (3) equipped with an aeration head (2). The aeration head (2) is connected to a nitrogen cylinder (1) via a valve. The raw water tank (3) is connected to the water inlet (7) at the bottom of the reactor (13) via a water inlet pump (5). 3+ Fe in the dosing unit 3+ The dosing tank (4) is connected to the inlet of the dosing pump (6), and the outlet of the dosing pump (6) is connected to the inlet (7) at the bottom of the reactor (13). The middle and lower part of the reactor (13) is the packing zone (12), which is filled with sulfur-modified pyrite packing particles and quinone compound-modified ceramsite. The upper side of the reactor (13) is provided with an outlet (9), which is connected to the product water tank (10). The top port of the reactor is provided with an end cap, and the end cap is provided with an exhaust port (11). The lower part of the packing zone (7) is connected to the aeration pump (8).

[0016] Fe 3+The dosing unit (4) is used for adding ferric iron solution. Ferric iron can be prepared from ferric chloride, ferric sulfate and an equimolar amount of Na2EDTA, or it can be directly prepared from Fe(III)EDTA reagent. The concentration of ferric iron added is 5-10 mM.

[0017] The sulfur-modified pyrite filler consists of pyrite particles with a layer of elemental sulfur particles on their surface, and the modified pyrite particles have a particle size of 5-10 mm; the modified ceramsite consists of ceramsite particles with quinone compounds adsorbed on their surface, and the modified ceramsite particles have a particle size of 5-10 mm; the filling volume ratio of modified pyrite and modified ceramsite is 1:1 to 3:1, and the modified pyrite and modified ceramsite are mixed together.

[0018] The method for preparing the modified pyrite particles is as follows:

[0019] S1: Soak unmodified pyrite particles with a particle size of 2-5mm in hydrochloric acid (preferably 10% by mass) for 20 minutes, and then rinse the surface of the pyrite repeatedly with tap water until the pH of the effluent is neutral.

[0020] S2: The pyrite obtained in step S1 is dried in a vacuum freeze dryer and then sealed and stored under a nitrogen atmosphere.

[0021] S3: The pyrite obtained in S2 is impregnated in liquid sulfur for 24-36 hours. After impregnation, the pyrite is placed in a low-temperature vacuum drying oven (40-50℃) for 6-8 hours. The modification of the pyrite can be considered complete.

[0022] The modified ceramsite preparation method is as follows: soak the unmodified ceramsite in a quinone compound solution for 30-60 minutes;

[0023] Preferably, the quinone compound is riboflavin, and the riboflavin solution concentration is 0.003 mM.

[0024] A treatment start-up method for accelerating the autotrophic denitrification of pyrite using the above-mentioned apparatus is characterized by comprising the following steps:

[0025] (1) After filling the packing particles into the packing area of ​​the reactor, add activated sludge (sludge from the secondary sedimentation tank + raw water, the sludge concentration after mixing is 3000 mg / L). During this period, no water is added. Start the air pump to aerate for 5 minutes every day to make the sludge evenly mixed. Then soak until 48 hours later, let it stand, and then drain the supernatant.

[0026] (2) The raw water tank is pretreated by aeration with nitrogen cylinders to remove oxygen from the raw water and ensure that DO in the raw water is <0.5mg / L. Water is fed in with a hydraulic retention time of 12h. When water is fed in, the dosing pump is turned on to make the ferric iron concentration in the reactor 5-10mM. The reactor is kept running continuously. During this period, the TN removal rate of the effluent and the biofilm acclimatization of the reactor are observed. If the TN removal rate reaches more than 80% for 5 consecutive days and a brownish-yellow biofilm covers the surface of the packing, the reactor is considered to have started up successfully.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] First, by adding Fe 3+ Ferrous iron can react chemically with pyrite, promoting the dissolution of pyrite and thus accelerating its absorption and utilization by microorganisms, thereby increasing the rate of pyrite autotrophic denitrification.

[0029] Second, the addition of sulfur (S) to the surface of pyrite facilitates the enrichment of denitrifying thiobacilli, accelerating the initiation rate of the autotrophic denitrification reaction in pyrite.

[0030] Third, the introduction of modified ceramsite into the pyrite autotrophic denitrification system has several advantages. Firstly, the smooth surface of pyrite means that backwashing may cause a large loss of biomass, affecting the subsequent biological denitrification effect. The high specific surface area of ​​ceramsite is conducive to the enrichment of microorganisms and can buffer the impact of backwashing on the system. Secondly, the surface of modified ceramsite contains riboflavin, which can accelerate electron transfer in the denitrification process and thus improve the denitrification rate.

[0031] Fourth, the modification method in this invention is the impregnation method, and all the operation steps adopted are conventional methods. The modification conditions are easy to control, and no high temperature and high pressure reaction environment is required, making it easy to implement.

[0032] Fifth, the commonly used matrix materials selected in this invention are simple, readily available, and inexpensive; the chemical agents used for modification are all commonly used reagents, resulting in low modification costs.

[0033] Sixth, the technology of this invention can be started up quickly in just over 10 days. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the device of the present invention.

[0035] Explanation of reference numerals in the attached diagram: 1-Nitrogen cylinder; 2-Aeration head; 3-Raw water tank; 4-Dosing tank; 5-Inlet pump; 6-Dosing pump; 7-Inlet; 8-Aeration pump; 9-Outlet; 10-Outlet water tank; 11-Exhaust port; 12-Packing area; 13-Reactor.

[0036] Figure 2 The image shows the startup and running effect of an example. Detailed Implementation

[0037] To better understand the present invention, the following examples further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0038] Example 1:

[0039] Two reactors were set up. The reactor material was acrylic sheet. The total height of the reactor was 1000 mm, the inner diameter was 60 mm, the effective height was 700 mm, and the effective volume was 2.0 L (see experimental setup). Figure 1 The inlet unit includes a nitrogen cylinder 1, an aeration head 2, a raw water tank 3, a chemical dosing tank 4, an inlet pump 5, and a chemical dosing pump 6; the reaction unit includes an inlet 7, an outlet 9, an exhaust port 11, and pyrite or modified pyrite 12; the outlet unit includes a product water tank 10. It operates in an upflow configuration, controlling the reactor temperature at (33±1)℃. The difference between reactors 1 and 2 is as follows:

[0040] ① Reactor No. 1 has no dosing tank or dosing pump, and the packing zone consists of unmodified pyrite and unmodified ceramsite;

[0041] ② Reactor No. 2 has a dosing tank and a dosing pump. The packing zone consists of modified pyrite and modified ceramsite. The dosing tank contains Fe(III)EDTA solution with a concentration of 100 mM.

[0042] Pyrite and ceramsite are filled at a volume ratio of 2:1. The particle size of both pyrite and ceramsite is 5-10 mm. The height of the filling layer is 700 mm, and the porosity of the bed is about 60-70%.

[0043] After filling reactors 1 and 2 with packing particles, 2L of activated sludge (a mixture of secondary sedimentation tank sludge and raw water, with a sludge concentration of 3000mg / L) was added. No water was introduced during this stage; the mixture was allowed to remain for 2 days, with the air pump running for 5 minutes daily to ensure more even sludge distribution. After settling, the supernatant was drained. The raw water tank was pretreated with nitrogen to remove oxygen, ensuring DO < 0.5mg / L. Reactors 1 and 2 were fed with water at a hydraulic retention time of 12 hours (influent pump flow rate 165mL / h). Additionally, reactor 2 was dosing with a chemical dosing pump (dosing flow rate 8.3mL / h), adding Fe(III)EDTA at a concentration of 5mM. The reactors were kept running continuously, and the TN removal rate of the effluent and the biofilm acclimatization of the reactors were observed. If the TN removal rate reached over 80% for 5 consecutive days, and a brownish-yellow biofilm covered the packing surface, the reactor was considered successfully started.

[0044] like Figure 2As shown, Reactor 1 achieved an 80% TN removal rate on the 24th day of continuous operation and remained stable for the next 5 days, meaning Reactor 1 could start up rapidly within 28 days (counting 5 days from the 24th day, i.e., successfully starting up within 28 days). Reactor 2 achieved an 80% removal rate on the 12th day of continuous operation and remained stable for the next 5 days, meaning Reactor 2 could start up rapidly within 16 days. After Reactor 2 started up normally, the dosing unit was shut down.

[0045] Therefore, it can be seen that modified pyrite and ceramsite can significantly improve the reactor start-up cycle. This is mainly because ① sulfur has a lower density than pyrite, and the sulfur adhering to the surface of pyrite is in powder form with a large specific surface area, making it easily utilized by microorganisms and achieving the initial enrichment of sulfur autotrophic denitrification microorganisms; ② Fe 3+ It can oxidize pyrite, which dissolves to form Fe2+ and thiosulfate. The enriched sulfur-autotrophic denitrifying microorganisms utilize the thiosulfate for denitrification. 2+ It reacts with nitrate to regenerate Fe 3+ This cycle can further significantly shorten the reactor start-up time; ③ Riboflavin can accelerate electron transfer in the denitrification process and increase the denitrification rate. Compared with the 28-day start-up time of traditional pyrite autotrophic denitrification, the start-up time of the reactor modified with pyrite can be shortened to 16 days.

[0046] The experimental influent was simulated wastewater, and its quality was as follows:

[0047] Table 1. Influent water quality indicators (COD of the water is 50 mg / L)

[0048]

[0049] This invention modifies pyrite and ceramsite using an impregnation method. Then, it utilizes the elemental sulfur on the surface of the modified pyrite to accelerate the enrichment of sulfur-autotrophic denitrifying microorganisms. Finally, it adds Fe... 3+ It reacts with pyrite to accelerate the dissolution of pyrite, and then accelerates the reactor start-up time by utilizing the riboflavin on the surface of the ceramic particles to promote the microbial autotrophic denitrification process of pyrite.

Claims

1. A treatment method that can accelerate the start-up of autotrophic denitrification of pyrite, characterized by, The adopted device includes a water inlet unit, a Fe 3+ a dosing unit, a reactor, pyrite filler particles modified with sulfur, and ceramsite modified with a quinone compound; The water inlet unit is provided with an aeration head in the raw water tank, the aeration head is connected with the nitrogen cylinder through a valve, and the raw water tank is connected with the water inlet at the bottom of the reactor through a water inlet pump; Fe 3+ The Fe 3+ The dosing tank is connected with the inlet of the dosing pump, the outlet of the dosing pump is connected with the water inlet at the bottom of the reactor; the middle and lower parts of the reactor are the filler area, the filler area is filled with sulfur-modified pyrite filler particles and quinone compound modified haydite; the upper part of the reactor is provided with a water outlet on the side, the water outlet is connected with the water production tank; the top of the reactor is provided with an end cover, and the end cover is provided with an exhaust port; the lower part of the filler area is connected with the aeration pump in communication; The treatment method comprises the following steps: (1) After the sulfur-modified pyrite filler particles and the quinone compound-modified ceramsite are mixed together and filled into the reactor filler zone, active sludge is added, no water is added during this period, the aeration pump is started every day to aerate for 5 min, the sludge is uniformly mixed, then soaked, and after 48 h, the supernatant is discharged after standing; (2) The raw water tank is pretreated by nitrogen gas bottle aeration to remove oxygen in the raw water, so as to ensure that the DO in the raw water is less than 0.5 mg / L; the water is added according to the hydraulic retention time of 12 h, the dosing pump is started when the water is added, so that the concentration of ferric iron in the reactor is 5-10 mM, the reactor is continuously operated, the removal rate of effluent TN and the reactor biofilm acclimation during this period are observed, if the TN removal rate is more than 80% for 5 consecutive days, and the filler surface is covered with a layer of brown-yellow biofilm, it is considered that the reactor is successfully started; The preparation method of the sulfur-modified pyrite filler particles is as follows: S1: The unmodified pyrite particles are soaked in hydrochloric acid, then the surface of the pyrite is repeatedly washed with tap water until the pH value of the washing effluent is neutral; S2: The pyrite prepared in step S1 is dried by a vacuum freeze dryer and then sealed and stored under nitrogen atmosphere protection; S3: The pyrite prepared in S2 is immersed in liquid sulfur, after the immersion is completed, the pyrite is dried in a low-temperature vacuum drying box to obtain sulfur-modified pyrite filler particles; The quinone compound-modified ceramsite is obtained by soaking unmodified ceramsite in a quinone compound solution.

2. The method of claim 1, wherein, In step (1), the active sludge is mixed with the raw water after the sludge is added, and the sludge concentration is 3000 mg / L.

3. The method of claim 1, wherein, Fe 3+ The dosing unit is used for the dosing of ferric iron. The ferric iron is prepared by mixing ferric chloride solution or / and ferric sulfate solution with equimolar Na2EDTA or directly using Fe(III)EDTA reagent.

4. The method of claim 1, wherein, The particle size of the sulfur-modified pyrite filler particles is 5-10 mm; the particle size of the quinone compound-modified ceramsite is 5-10 mm.

5. The method of claim 1, wherein, The filling volume ratio of the sulfur-modified pyrite filler particles to the quinone compound-modified ceramsite is 1:1 to 3:

1.

6. The method of claim 1, wherein, The quinone compound is riboflavin, and the concentration of the riboflavin solution is 0.003 mM.

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