Treatment device capable of accelerating starting of autotrophic denitrification of pyrite

Abstract

The utility model discloses a treatment device capable of accelerating starting of autotrophic denitrification of pyrite, and belongs to the technical field of sewage treatment. The Fe < 3 + > dosing unit comprises a Fe < 3 + > dosing tank (4) and a dosing pump (6); according to the water inlet unit, an aeration head (2) is arranged in a raw water tank (3), the aeration head (2) is connected with a nitrogen cylinder (1) through a valve, filler filled in the reactor is modified pyrite filler particles and modified ceramsite, the bottom of the reactor is connected with an aeration pump, and a Fe < 3 + > dosing tank (4) is connected with a water inlet (7) in the bottom of the reactor (13) through a dosing pump (6). The method comprises the following steps: aerating sludge, standing, discharging water, and adding ferric iron into the water subjected to nitrogen aeration treatment to carry out accelerated reaction. By adopting the technology of the utility model, the starting can be quickly carried out for more than 10 days.

Description

Technical Field

[0001] The utility model relates to the technical field of denitrification, in particular to a treatment device capable of accelerating the start-up of autotrophic denitrification of pyrite. Background Art

[0002] Traditional biological nitrogen removal processes are basically based on heterotrophic denitrification to remove total nitrogen. However, when applied to the advanced treatment of sewage plants, due to the low C / N of the tail water, there will be a shortage of carbon sources. If TN is to be effectively removed, a large amount of organic matter needs to be added. Therefore, the operating cost will increase significantly. Moreover, in case of water quality fluctuations, how to effectively add organic matter becomes a difficult point. Excessive addition will cause waste and affect the effluent quality; insufficient addition will result in unsatisfactory denitrification effects.

[0003] Pyrite (pyrite FeS 2 ) autotrophic denitrification does not require external carbon sources. During denitrification, Fe 3+ or Fe(OH) 3 can be generated, which combines with phosphorus in water to form precipitates, thereby achieving simultaneous nitrogen and phosphorus removal. Pyrite raw materials are easily available, with low raw material costs and operating costs, less sludge production, high efficiency, and simple processes. Pyrite autotrophic denitrification consumes less alkalinity and generates less sulfate during the reaction process, and can achieve simultaneous nitrogen and phosphorus removal during the denitrification process, thus attracting much attention.

[0004] However, there are certain problems with the autotrophic denitrification system constructed with pyrite as the substrate. Pyrite is a solid and is not easily utilized by microorganisms in sewage. The growth of microorganisms is slow, resulting in slow start-up of the reactor, long system residence time, and relatively low denitrification efficiency. Therefore, it is very necessary to explore a pyrite autotrophic denitrification process with a fast start-up.

[0005] Regarding the problem of slow microbial growth, according to the results of preliminary bench-scale tests, the microorganisms in the autotrophic denitrification system with elemental sulfur as the sulfur source grow fast and the system start-up period is short.

[0006] Regarding problems such as low denitrification rate, according to literature reports, redox mediators, as electron carriers, can accelerate the transfer of electrons from the electron donor to the final electron acceptor through the cyclic conversion of their oxidized and reduced states, thereby increasing the reaction rate by one to several orders of magnitude and accelerating the conversion of pollutants, such as the reduction of nitrate nitrogen. Common redox mediators mainly include some quinone substances, riboflavin, etc.

[0007] Regarding the problem of difficult utilization of pyrite, according to literature reports, the microbial oxidation of pyrite includes direct oxidation mechanism and indirect oxidation mechanism. The direct oxidation mechanism is mainly through the oxidation of pyrite by oxygen. Indirect oxidation is through the oxidation of pyrite by Fe 3+ to generate Fe 2+and sodium thiosulfate, which is utilized by microorganisms through the sodium thiosulfate pathway to reduce NO 3 - to N 2 , Fe 2+ is oxidized by NO in an anoxic environment 3 - to generate Fe 3+ , and so on in a cycle.

[0008]

[0009]

[0010]

[0011] The bioleaching of pyrite is mainly indirect oxidation.

[0012] Based on this, after using Thiobacillus denitrificans - like microorganisms enriched with sulfur in this application, by adding Fe 3+ , the dissolution process of pyrite is promoted, and then under the redox mediator, the denitrification rate is increased, thereby accelerating the startup of the pyrite autotrophic denitrification reactor. Utility Model Content

[0013] Aiming at the deficiencies of the prior art, the utility model relates to a treatment device and application that can accelerate the autotrophic denitrification startup of pyrite.

[0014] To achieve the above - mentioned purpose, the technical solution adopted by the utility model is: a treatment device that can accelerate the autotrophic denitrification startup of pyrite, including a water inlet unit, an Fe 3+ drug - adding unit, a reactor, modified pyrite filler particles, and modified ceramsite; Fe 3+ The drug - adding unit includes an Fe 3+ drug - adding tank (4) and a drug - adding pump (6);

[0015] The water inlet unit is that an aeration head (2) is arranged in the raw water tank (3), the aeration head (2) is connected to a nitrogen cylinder (1) via a valve, and 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); Fe 3+ The Fe 3+ drug - adding tank (4) of the drug - adding unit is connected to the inlet of the drug - adding pump (6), and the outlet of the drug - adding pump (6) is connected to the water inlet (7) at the bottom of the reactor (13); the middle - lower part of the reactor (13) is a packing area (12), and the packing area is filled with sulfur - modified pyrite filler particles and quinone - compound - modified ceramsite; a water outlet (9) is arranged on the upper side of the reactor (13), and the water outlet (9) is connected to a water production tank (10); a end cover is arranged at the top port of the reactor, and an exhaust port (11) is arranged on the end cover; the lower part of the packing area (7) is connected and communicated with an aeration pump (8).

[0016] Fe 3+ The chemical dosing unit (4) is used for dosing ferric solution. The ferric can be ferric chloride, ferric sulfate, and equimolar Na 2 prepared by EDTA, or directly prepared by Fe(III)EDTA reagent, etc. The dosing concentration of ferric is 5-10 mM.

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

[0018] The preparation method of the modified pyrite particles is as follows:

[0019] S1: Immerse unmodified pyrite particles with a particle size of 2-5 mm in hydrochloric acid (preferably with a mass percentage concentration of 10%) for 20 min, and then repeatedly rinse the surface of the pyrite with tap water until the pH value of the washing effluent is neutral;

[0020] S2: Dry the pyrite obtained in step S1 with a vacuum freeze dryer and then store it sealed under nitrogen atmosphere protection;

[0021] S3: Immerse the pyrite obtained in S2 in liquid sulfur for 24 h-36 h. After the immersion is completed, place the pyrite in a low-temperature vacuum drying oven (40-50 °C) and dry it for 6-8 h. It can be considered that the pyrite modification is completed.

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

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

[0024] The treatment startup method that can accelerate the startup of sulfur-iron autotrophic denitrification is carried out by using the above device, which is characterized in that it includes the following steps:

[0025] (1) After filling the filler particles into the reactor filler area, add activated sludge (after mixing secondary sedimentation tank sludge and raw water, the mixed sludge concentration is 3000 mg / L). During this period, no water is inlet. Start the air pump to aerate for 5 min every day to make the sludge mix evenly, and then soak. Until 48 h later, let it stand, and drain the supernatant;

[0026] (2) The raw water tank is pretreated by aeration with nitrogen cylinders to remove the oxygen in the raw water and ensure that the DO in the raw water is < 0.5 mg / L. Water is fed in according to a hydraulic retention time of 12 h. When feeding water, the dosing pump is turned on to make the ferric iron concentration in the reactor 5 - 10 mM. The reactor operates continuously. Observe the TN removal rate of the effluent and the biofilm acclimation of the reactor during this period. If the TN removal rate reaches over 80% for 5 consecutive days and a brownish-yellow biofilm covers the surface of the packing, it is considered that the reactor starts successfully.

[0027] Compared with the prior art, the beneficial effects of the present utility model are as follows:

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

[0029] Second, S is added to the surface of pyrite. S elemental substance is easy to achieve the enrichment of Thiobacillus denitrificans, accelerating the start-up rate of the autotrophic denitrification reaction of pyrite.

[0030] Third, modified ceramsite is introduced into the autotrophic denitrification system of pyrite. On the one hand, the surface of pyrite is smooth, and 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 brought by backwashing to the system. On the other hand, riboflavin is on the surface of the modified ceramsite, and riboflavin can accelerate the electron transfer in the denitrification process, thereby enhancing the denitrification rate.

[0031] Fourth, the modification method in the present utility model is the impregnation method. All the operation steps adopted are conventional methods. The modification conditions are easy to control, and there is no need for a reaction environment of high temperature and high pressure, which is convenient for implementation.

[0032] Fifth, the commonly used matrix materials selected in the present utility model are simple to obtain and low in cost; the chemical reagents used for modification are all common reagents, and the modification cost is relatively low.

[0033] Sixth, the technology of the present utility model can be started quickly in more than 10 days. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the device of the present utility model.

[0035] Description of the reference numerals: 1 - nitrogen cylinder; 2 - aeration head; 3 - raw water tank; 4 - dosing tank 5 - feed water pump; 6 - dosing pump, 7 - water inlet, 8 - aeration pump, 9 - water outlet, 10 - effluent water tank, 11 - exhaust port, 12 - packing area, 13 - reactor.

[0036] Figure 2Startup operation effect diagram for the embodiment. Detailed implementation manners

[0037] To better understand the present utility model, the content of the present utility model will be further clarified below in conjunction with examples, but the content of the present utility model is not limited to the following examples only.

[0038] Example 1:

[0039] Two sets of reactors are provided. The reactor material is acrylic board. The total height of the reactor is 1000 mm, the inner diameter is 60 mm, the effective height is 700 mm, and the effective volume is 2.0 L (see the experimental device in Figure 1 , the water inlet unit includes a nitrogen cylinder 1, an aeration head 2, a raw water tank 3, a chemical dosing tank 4, a water inlet pump 5, and a chemical dosing pump 6; the reaction unit includes a water inlet 7, a water outlet 9, an exhaust port 11, pyrite or modified pyrite 12, and the water outlet unit includes a product water tank 10), and an upflow operation is adopted, and the temperature in the reactor is controlled at (33 ± 1) °C. Among them, the differences between the No. 1 and No. 2 reactors are:

[0040] ① The No. 1 reactor does not have a chemical dosing tank and a chemical dosing pump, and the packing area is unmodified pyrite and unmodified ceramsite;

[0041] ② The No. 2 reactor has a chemical dosing tank and a chemical dosing pump, and the packing area is modified pyrite and modified ceramsite. The chemical dosing tank contains Fe(III)EDTA solution with a configured concentration of 100 mM.

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

[0043] After filling the packing particles into the No. 1 and No. 2 reactors, 2 L of activated sludge is added (after mixing secondary sedimentation tank sludge and raw water, the mixed sludge concentration is 3000 mg / L). At this stage, no water is inlet, and it stays for 2 days. The air pump is turned on for aeration for 5 minutes every day to make the sludge distribution more uniform; after standing, the supernatant is discharged. The raw water tank is pretreated by aeration with a nitrogen cylinder to remove the oxygen in the raw water and ensure that the DO in the raw water < 0.5 mg / L. Both the No. 1 and No. 2 reactors are inlet with water according to a hydraulic retention time of 12 h (the flow rate of the water inlet pump is 165 mL / h). In addition, the chemical dosing pump of the No. 2 reactor is turned on (the chemical dosing flow rate is 8.3 mL / h), that is, the concentration of added Fe(III)EDTA is 5 mM. The reactor operates continuously, and the TN removal rate of the effluent and the biofilm acclimation situation of the reactor are observed during this period. If the TN removal rate reaches more than 80% for 5 consecutive days, and a brownish-yellow biofilm covers the surface of the packing, it is considered that the reactor startup is successful.

[0044] As Figure 2As shown, the TN removal rate of Reactor No. 1 reached 80% on the 24th day of continuous operation and remained stable for the following 5 consecutive days. That is, Reactor No. 1 could be quickly started within 28 days (starting from the 24th day and counting 5 days, it is the 28th day). The removal rate of Reactor No. 2 reached 80% on the 12th day of continuous operation and remained stable for the following 5 consecutive days. That is, Reactor No. 2 could be quickly started within 16 days. After the normal start of Reactor No. 2, the dosing unit was closed.

[0045] Therefore, it can be seen that the modified pyrite and ceramsite can significantly improve the start-up period of the reactor. This is mainly because: ① Since the density of sulfur is smaller than that of pyrite, and the sulfur attached to the surface of pyrite is in powder form with a large specific surface area, it is extremely easy to be utilized by microorganisms, realizing the preliminary enrichment of sulfur autotrophic denitrifying microorganisms; ② Fe 3+ can oxidize pyrite, and pyrite dissolves to form Fe2+ and thiosulfate. The enriched sulfur autotrophic denitrifying microorganisms use thiosulfate for denitrification, and Fe 2+ reacts with nitrate to regenerate Fe 3+ . In this way, the start-up time of the reactor can be significantly shortened; ③ Riboflavin can accelerate the electron transfer in the denitrification process and improve the denitrification rate. Compared with the start-up time of 28 days for traditional pyrite autotrophic denitrification, the start-up time of the reactor after pyrite modification can be shortened to 16 days.

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

[0047] Table 1 Influent water quality indicators (at the same time, the COD of the water quality was 50 mg / L)

[0048]

[0049] After the pyrite and ceramsite were modified by the impregnation method in the present utility model, the elemental sulfur on the surface of the modified pyrite was used to accelerate the enrichment of sulfur autotrophic denitrifying microorganisms. Then, by adding Fe 3+ to react with pyrite, the dissolution of pyrite was accelerated. Then, by using the riboflavin on the surface of ceramsite to combine with the process of microbial sulfur autotrophic denitrification of pyrite, the start-up time of the reactor was accelerated.

Claims

1. A treatment device capable of accelerating the start-up of autotrophic denitrification of pyrite, characterized in that: Including water inlet unit, Fe 3+ Dosing unit, reactor, modified pyrite filler particles, modified ceramsite; Fe 3+ Dosing unit includes Fe 3+ A dosing box (4) and a 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 to a nitrogen bottle (1) via a valve, and the raw water tank (3) is connected to a water inlet (7) at the bottom of the reactor (13) via a water inlet pump (5); Fe 3+ Fe in dosing unit 3+ The dosing box (4) is connected to the inlet of the dosing pump (6), and the outlet of the dosing pump (6) is connected to the water inlet (7) at the bottom of the reactor (13); the middle and lower part of the reactor (13) is a filling area (12), and the filling area is filled with sulfur-modified pyrite filling particles and quinone compound-modified ceramsite; the upper side of the reactor (13) is provided with a water outlet (9), and the water outlet (9) is connected to the water production tank (10); the top port of the reactor is provided with an end cover, and the end cover is provided with an exhaust port (11); the lower part of the filling area (12) is connected to the aeration pump (8).

2. The device according to claim 1, characterized in that Fe 3+ The dosing box (4) is used for adding trivalent iron, which is prepared by ferric chloride solution or / and ferric sulfate solution and equimolar Na2EDTA, or directly prepared by Fe(III)EDTA agent.

3. The device according to claim 1, characterized in that The sulfur-modified pyrite filler is a pyrite particle with a layer of sulfur particles on the surface, and the modified pyrite particle size is 5-10mm; the modified ceramsite is a ceramsite with quinone compounds adsorbed on the surface, and the modified ceramsite particle size is 5-10mm.

4. The device according to claim 1, characterized in that The filling volume ratio of the sulfur-modified pyrite filler particles and the quinone compound-modified ceramsite is 1:1 to 3:1, and the modified pyrite and the modified ceramsite are mixed together.

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