Method for echelon removal of perchlorate and nitrate in fireworks and crackers wastewater

Abstract

The invention discloses a method for echelon removal of perchlorate and nitrate in fireworks and crackers wastewater, which comprises the following steps: (1) denitrification removal: introducing wastewater containing perchlorate and nitrate into a denitrification reactor, and controlling the oxidation-reduction potential in the denitrification reactor to be-100mV to-200mV in a micro-aeration or intermittent aeration mode; adding a first part of a carbon source to realize preferential removal of nitrate; (2) perchlorate reduction: introducing the effluent treated in the step (1) into a perchlorate reactor; the method comprises the following steps: stopping aeration, selecting a closed anaerobic reactor, maintaining an anaerobic environment, and controlling the oxidation-reduction potential in a perchlorate reactor to be reduced to-250 mV to-350 mV; and adding a second part of the carbon source to realize reduction of the perchlorate. The method provided by the invention realizes step-by-step efficient removal of perchlorate and nitrate.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for gradually removing perchlorate and nitrate in fireworks and firecracker wastewater. Background Art

[0002] The production process of fireworks and firecrackers produces high concentrations of perchlorate (ClO4 - ) and nitrate (NO3 - ) wastewater; both are strong oxidizing pollutants, often existing in a combined pollution form, posing a potential threat to the ecological environment and human health. Perchlorate can interfere with thyroid function, while nitrate can lead to eutrophication and the risk of "three hazards" (hazards, disease, and pollution).

[0003] Biological methods are currently considered an effective way to treat wastewater containing perchlorate and nitrate due to their economical and environmentally friendly characteristics. This method primarily utilizes microorganisms under anaerobic or anoxic conditions to reduce perchlorate and nitrate using organic matter as electron donors and electron acceptors, ultimately converting them into harmless chloride ions (Cl-) and nitrogen gas (N2), respectively.

[0004] However, in the system where two pollutants coexist, there is a significant competitive inhibition problem in the microbial reduction process; when the electron donor (carbon source) is limited, when NO3 - -N and ClO4 - When coexisting, denitrifying bacteria usually have a higher affinity for electron donors than perchlorate-reducing bacteria. Denitrifying bacteria will preferentially utilize carbon sources, thereby inhibiting the metabolic activity of perchlorate-reducing bacteria and resulting in low perchlorate removal efficiency. If excessive carbon sources are added to ensure perchlorate reduction, it will not only waste resources, but may also cause the total organic carbon content in the effluent to exceed the standard, and even induce side reactions such as sulfate reduction, producing secondary pollutants such as hydrogen sulfide. In addition, traditional biological treatment processes lack precise control of the microbial metabolic environment, making it difficult to achieve simultaneous and efficient removal of both pollutants. The system operation is unstable and has poor resistance to load shock.

[0005] Therefore, when treating the combined pollution of perchlorate and nitrate in fireworks and firecracker wastewater, the existing technology lacks a precise control mechanism for the distribution of electron donors and cannot solve the problem of competitive inhibition between the two types of pollutants; it also does not construct a phased microbial metabolic environment control system, resulting in weak shock resistance of the system and load fluctuations that can easily cause microbial inactivation and secondary pollution. Summary of the Invention

[0006] In response to the above-mentioned technical defects, the present invention proposes a method for the step-by-step removal of perchlorate and nitrate in fireworks and firecracker wastewater. By optimizing the redox potential (ORP) gradient, the staged addition strategy of the carbon source, the targeted enrichment of the functional bacteria and the step-by-step control of the pollutant load, the step-by-step and efficient removal of perchlorate and nitrate is achieved; so as to solve the problems in the existing technology such as low perchlorate removal efficiency, low carbon source utilization and easy secondary pollution caused by competitive inhibition.

[0007] The method for removing perchlorate and nitrate in fireworks and firecracker wastewater in stages according to the present invention comprises the following steps:

[0008] (1) Denitrification removal step: introducing the wastewater containing perchlorate and nitrate into the denitrification reactor, controlling the redox potential in the denitrification reactor to -100 mV to -200 mV by micro-aeration or intermittent aeration; and adding the first portion of carbon source to achieve preferential removal of nitrate;

[0009] (2) Perchlorate reduction step: introducing the effluent treated in step (1) into a perchlorate reactor; maintaining an anaerobic environment by terminating aeration and selecting a closed anaerobic reactor, controlling the redox potential in the perchlorate reactor to decrease to -250 mV to -350 mV; and adding a second portion of carbon source to achieve perchlorate reduction.

[0010] Preferably, in the denitrification removal step, the first portion of carbon source is CH3COO in molar ratio - :NO3 - -N=1:1 dosing.

[0011] Preferably, in the perchlorate reduction step, the second portion of carbon source is CH3COO - :ClO4 - =2:1 addition.

[0012] Preferably, the method further comprises a step of targeted enrichment of functional bacterial flora, wherein:

[0013] In the denitrification reactor, the hydraulic retention time is controlled to be 3.5±0.2h, the temperature is 30±1°C, and the pH is 7.2±0.3; and the bacterial community having both denitrification and perchlorate reduction functions is enriched in a targeted manner;

[0014] In the perchlorate reactor, the hydraulic retention time is controlled to be 6.0±0.3h and the temperature is controlled to be 30±1°C; and the perchlorate-reducing bacteria are directionally enriched.

[0015] Preferably, the bacterial community having both denitrification and perchlorate reduction functions includes Propionivibrio, Dethiosulfatibacter and Lentimicrobium.

[0016] Preferably, the perchlorate-reducing bacteria include Dechlorosoma, Leptonema and Ciceribacter.

[0017] Preferably, the method further comprises a step of controlling the pollutant load by increasing the pollutant concentration in a stepwise manner.

[0018] NO3 - -N pollutant gradient load increase stage: 800gN / (m 3 ·d)→1200gN / (m 3 ·d)→1400gN / (m 3 d)) to make the nitrate volume load of the denitrification reactor reach 1400gN / (m 3 d);

[0019] ClO4 - Pollutant gradient load increase stage: 1200gClO4 - / (m 3 d) → 1900gClO4 - / (m 3 d) → 2250gClO4 - / (m 3 d)) to bring the perchlorate volumetric load of the perchlorate reactor to 2250 g ClO4 - / (m 3 ·d).

[0020] Preferably, the denitrification reactor is a baffled reactor; the perchlorate reactor is an upflow anaerobic reactor; the upward flow rate of the upflow anaerobic reactor is 2 to 3 m / h, and the sludge suspension concentration is maintained at not less than 8 gVSS / L by internal recirculation.

[0021] Preferably, in the denitrification removal step, the redox potential is preferably controlled to be -130±20 mV; and in the perchlorate reduction step, the redox potential is preferably controlled to be -310±10 mV.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention achieves the separation of metabolic pathways through redox potential gradient regulation, fundamentally solving the problem of competitive inhibition. In the denitrification section, the ORP is controlled at -100mV to -200mV, creating an optimal metabolic environment for denitrifying bacteria, preferentially and efficiently removing nitrate. At the same time, this potential is not enough to activate perchlorate reductase, thereby inhibiting competition. Subsequently, in the perchlorate section, the ORP is reduced to -250mV to -350mV, creating an exclusive, optimal strong reducing environment for perchlorate-reducing bacteria under the condition that the nitrate competitor has been removed. The present invention sets two clearly defined ORP ranges, solving the problem of competitive inhibition of two types of pollutants.

[0024] 2. The present invention achieves efficient distribution of electron donors by accurately adding carbon sources in sections, taking into account both treatment efficiency and economy. - :NO3 - -N=1:1 molar ratio is added to “supply on demand” electron donors to ensure efficient nitrate removal without carbon source residue; in the perchlorate section, CH3COO - :ClO4 - =2:1 molar ratio of carbon source supplementation, specifically for perchlorate reduction. This method precisely directs electron flow to the target reaction, greatly improving carbon source utilization efficiency and avoiding secondary pollution problems such as excessive TOC, methanogenesis, or sulfate reduction caused by excessive carbon source.

[0025] 3. By controlling specific environmental conditions and pollutant load gradients at different stages, this invention achieves targeted enrichment of functional bacterial communities. In the denitrification stage, bacteria with dual functions are enriched, improving the system's adaptability and pretreatment capabilities for combined pollution. In the perchlorate stage, highly efficient, specialized bacterial communities are enriched. This "specialized division of labor" microbial ecosystem not only achieves extremely high treatment efficiency but also provides strong buffering and resistance to load shocks, ensuring the long-term stable operation of the system.

[0026] 4. The present invention increases the pollutant load in a step-by-step manner, so that the system can adapt to and stably treat high-concentration wastewater. The volumetric loads of nitrate and perchlorate are 1400gN / (m 3 d) and 2250gClO4 - / (m 3 d), far surpassing conventional processes and eliminating the accumulation of intermediate products. Furthermore, the present invention, combined with the flow regime control (upward flow velocity and sludge recirculation) of the upflow anaerobic reactor, effectively retains high-concentration functional sludge and enhances mass transfer efficiency. This means the present invention is capable of stable operation under high-load conditions and has great potential for industrial application. DETAILED DESCRIPTION

[0027] In order to better understand the content of the present invention, the present invention will be further described below with reference to specific examples. The following examples are based on the technology of the present invention and provide detailed implementation methods and operating steps, but the scope of protection of the present invention is not limited to the following examples. That is, based on the examples of the present invention, all other examples obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] The method for removing perchlorate and nitrate in fireworks and firecracker wastewater in stages according to the present invention comprises the following steps:

[0029] (1) Denitrification removal step: The wastewater containing perchlorate and nitrate is introduced into the denitrification reactor. Through micro-aeration or intermittent aeration, the redox potential (ORP) in the denitrification reactor is precisely controlled to -100mV to -200mV. Within this ORP range, the ubiquinone-cytochrome c electron transport chain of the denitrifying bacteria reaches the optimal reduction state, improving the efficiency of the electron carrier NADH to the enzyme system; maximizing the reduction metabolic activity and electron donor supply of the microorganisms, it can efficiently reduce nitrate to nitrogen gas without nitrite accumulation; at the same time, the activity of perchlorate-reducing bacteria is inhibited to prevent them from competing with denitrifying bacteria for carbon sources, thereby achieving preferential and efficient removal of nitrate.

[0030] In the denitrification removal step, the ORP is controlled to be not less than -200 mV to avoid excessive reduction and activation of perchlorate-reducing bacteria, thereby preventing the carbon source from being competitively consumed.

[0031] (2) Perchlorate Reduction Step: The effluent from the denitrification step is introduced into the perchlorate reactor. By terminating aeration and using a closed anaerobic reactor, the redox potential in the perchlorate reactor is further reduced to -250mV to -350mV. This ORP range is the optimal potential range for perchlorate reductase (PcrA) activation, creating a strong reducing environment and enhancing the metabolic activity of perchlorate-reducing bacteria.

[0032] Controlling the ORP to be no less than -350 mV in the perchlorate reduction step can effectively avoid activation of sulfate-reducing bacteria due to excessive reduction and prevent the generation of secondary sulfide pollution.

[0033] As any embodiment of the present invention, the denitrification reactor adopts a baffled reactor, which is equipped with a baffled multi-stage reaction zone and a vertical flow sedimentation zone, and a built-in low-speed agitator to maintain an anoxic environment; the perchlorate reactor adopts an upflow anaerobic reactor, which is equipped with a biological reaction zone and a sedimentation zone.

[0034] In the denitrification reactor, the redox potential in the baffled reactor was controlled at -130±20mV, the hydraulic retention time was 3.5±0.2h, the temperature was 30±1℃, and the pH was 7.2±0.3. At the same time, the first part of the carbon source was added at the water inlet. By controlling the carbon-nitrogen ratio, the bacterial communities of Propionivibrio, Dethiosulfatibacter, and Lentimicrobium with both denitrification and partial perchlorate reduction functions were enriched in a targeted manner, thereby improving the treatment capacity and stability of complex pollutants.

[0035] After 30 days of enrichment, qPCR detection of Propionivibrio, Dethiosulfatibacter and Lentimicrobium accounted for 15.3±3.8%, 8.9±2.2% and 6.4±1.3%, respectively, achieving the denitrification stage ClO4 - The simultaneous removal rate was 38.5±2.1%. In this stage, bacteria with both denitrification and perchlorate reduction functions were enriched, improving the system's adaptability to complex pollution.

[0036] In the perchlorate reactor, the redox potential in the upflow anaerobic reactor was controlled at -310±10mV, the hydraulic retention time was 6.0±0.3h, and the temperature was 30±1°C. Simultaneously, a second portion of carbon source was continuously added to the bottom of the biological reaction zone, specifically for the reduction of perchlorate, ultimately reducing it completely to chloride ions. Through a strictly anaerobic environment, perchlorate-reducing bacteria such as Dechlorosoma, Leptonema, and Ciceribacter were enriched in a targeted manner to ensure deep removal of perchlorate.

[0037] After 40 days of enrichment, qPCR detection showed that Dechlorosoma, Leptonema and Ciceribacter accounted for 18.4±2.8%, 7.7±1.6% and 5.9±1.1% respectively, achieving efficient removal of perchlorate, with an average removal rate of 99±0.2%. The system's ability to resist load shock was also significantly improved (ClO4 - Removal rate>99.5%).

[0038] As any embodiment of the present invention, in the denitrification removal step, the first portion of carbon source is CH3COO in a molar ratio of - :NO3 - -N=1:1 addition; used to prioritize the denitrification reaction requirements, ensuring nitrate removal efficiency>99% and no carbon source waste; in the perchlorate reduction step, the second part of the carbon source is CH3COO in molar ratio - :ClO4 -=2:1 to ensure the electron donor required for perchlorate reduction and avoid excessive carbon source causing organic matter residue in the effluent; the carbon source is preferably sodium acetate.

[0039] As any embodiment of the present invention, in the denitrification removal step, the step further includes NO3 - -N pollutant gradient load increase control and ClO4 - Pollutant gradient load enhancement control; the NO3 - The process of increasing the gradient load of -N pollutants includes three stages: Stage I: initial 800gN / (m 3 ·d), Stage II: 1200gN / (m 3 ·d), Stage III: 1400gN / (m 3 d)); Volumetric load gradient control is achieved by step-by-step increasing of influent nitrate concentration, at 1400gN / (m 3 ·d) NO3 in outlet water under load - -N=0.02±0.05mg / L, nitrite did not accumulate, and this load threshold can ensure the integrity of denitrification.

[0040] The ClO4 - The pollutant gradient load increase process includes three stages: Stage I: 1200gClO4 - / (m 3 d), Stage II: 1900g ClO4 - / (m 3 d), Stage III: 2250 g ClO4 - / (m 3 d)). At a perchlorate loading of 2250 g ClO4 - / (m 3 ·d), ClO4 can be achieved - The average removal rate is 99.2±0.5%, and there is no substrate effect and intermediate products (such as ClO3 - )accumulation.

[0041] The present invention increases the concentration of influent pollutants in a step-by-step manner; the nitrate volume load of the denitrification reactor can be stabilized at 1400gN / (m 3 d) The perchlorate volumetric load of the perchlorate reactor can be stabilized at 2250gClO4 - / (m 3 d) Under this load, the system can still maintain a high efficiency and stable removal effect without the accumulation of intermediate products such as nitrite or chlorate.

[0042] The upward flow rate of the anaerobic upflow reactor is 2-3 m / h, while internal recirculation maintains a sludge suspension concentration of no less than 8 gVSS / L. This flow pattern control, combined with redox potential regulation, creates a synergistic effect, enhancing sludge-water mass transfer efficiency, preventing sludge loss, and ensuring the retention of a high concentration of functional bacteria.

[0043] In order to further understand the technical solution of the present invention, the following examples are given;

[0044] Example 1

[0045] The test water quality characteristics are as follows: ClO4 - The concentration is 308±5.6mg / L, NO3 - -N concentration was 157±4.2 mg / L. The test environment temperature was 25°C, the test apparatus used a baffled reactor made of organic glass, the total HRT of the apparatus was 10 h, and the total water flow rate was 0.5 L / h.

[0046] In the denitrification reactor stage, three parallel experiments were set up through micro-aeration or intermittent aeration to precisely control ORP at -120±20mV, -150±20mV and -180±20mV respectively. Each group ran for an average of 20 days.

[0047] In the perchlorate reduction stage, the test water quality is the effluent after denitrification treatment, and the ClO4 - The concentration is 305±5.2mg / L, NO3 - -N concentration 30±1.5mg / L, SO4 - The concentration was 101±4.3 mg / L. Through nitrogen purging and upward flow rate control, three parallel experiments were set up to accurately control ORP at -230±20 mV, -300±20 mV and -330±20 mV respectively. Each group was run for an average of 20 days.

[0048] After stable operation, the results are as follows:

[0049] ORP in -120±20mV system, NO3 - The average effluent concentration of -N was 0.02±0.05 mg / L, and the removal rate was 99.9%±0.12%.

[0050] ORP in -150±20mV system, NO3 - The average effluent concentration of -N was 0.01±0.04 mg / L, and the removal rate was 99.9%±0.08%.

[0051] ORP in -180±20mV system, NO3 - The average effluent concentration of -N was 0.04±0.02 mg / L, and the removal rate was 99.9%±0.21%.

[0052] ORP in -230±20mV system, ClO4 - The average effluent concentration was 0.51±0.8 mg / L, and the removal rate was 99.5%±0.6%.

[0053] ORP at -300±20mV system, ClO4 - The average effluent concentration was 0.09±0.03 mg / L, and the removal rate was 99.9%±0.08%.

[0054] ORP in -330±20mV system, ClO4 - The average effluent concentration was 0.13±0.05 mg / L, and the removal rate was 99.7%±0.21%.

[0055] The results show that the ORP range (-100mV to -200mV) proposed by the present invention can achieve efficient and stable removal of nitrate without nitrite accumulation. The ORP range (-250mV to -350mV) can achieve efficient, stable removal of perchlorate without secondary pollution.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 1 is that in the denitrification reactor stage, the ORP setting groups are -300±20mV, -50±20mV, +50±20mV and +150±20mV, respectively, and the other parameters are the same as those in Example 1.

[0058] During the perchlorate reduction stage, the ORP setting groups were -200±20 mV, -100±20 mV, and -400±20 mV, respectively. Other parameters were the same as those in Example 1.

[0059] The experimental results show that:

[0060] ORP at -300±20mV system, NO3 - The average effluent concentration of -N was 0.43±0.08 mg / L, the removal rate dropped to 98.7%±0.32%, and some perchlorate began to be reduced, causing competition for carbon sources.

[0061] ORP in -50±20mV system, NO3 - The average effluent concentration of -N increased to 10.8±2.23 mg / L, and the removal rate decreased to 93.2%±2.11%.

[0062] ORP in the +50±20mV system, NO3 - The average effluent concentration of -N increased to 19.6±1.23 mg / L, and the removal rate decreased to 87.5%±1.02%.

[0063] ORP in the system of +150±20mV, NO3 - The average effluent concentration of -N increased to 36.7±5.03 mg / L, and the removal rate decreased to 76.6%±4.02%.

[0064] ORP at -200±20mV system, ClO4 - The average effluent concentration increased to 4.3±2.8mg / L, and the removal rate decreased to 98.2%±2.31%.

[0065] ORP at -100±20mV system, ClO4 - The average effluent concentration increased to 18.3±4.2 mg / L, and the removal rate decreased to 94.2%±3.01% (insufficient activity of perchlorate-reducing bacteria).

[0066] ORP at -400±20mV system, ClO4 - The average effluent concentration increased to 13.1±10.2 mg / L, and the removal rate dropped to 95.6%±5.12% (with a noticeable sulfur odor).

[0067] The results of Comparative Example 1 show that when the ORP in the denitrification reactor stage is too low (e.g., -300 mV), unnecessary carbon source competition will be triggered, while when the ORP is too high (≥-50 mV), the denitrification enzyme activity is inhibited, the efficiency of the electron transport chain is reduced, and the efficient removal of nitrate cannot be maintained; the removal efficiency is significantly lower than that in Example 1.

[0068] When the ORP is higher than -250 mV during the perchlorate reduction stage, the perchlorate reduction environment is insufficient and the activity of reducing bacteria is limited; when the ORP is lower than -350 mV, side reactions such as sulfate reduction are triggered, causing secondary pollution and affecting the perchlorate removal effect, and the removal efficiency is lower than that of Example 1.

[0069] Example 2

[0070] In the laboratory continuous flow test, the present invention adopts a two-stage bioreactor to treat nitrate (NO3 - -N=150±5mg / L) and perchlorate (ClO4 - =300±10mg / L) of simulated wastewater.

[0071] The denitrification section uses a baffled reactor, controlling ORP = -150 ± 20mV, HRT = 6h, and CH3COO - :NO3 - -N=1:1 molar ratio of sodium acetate was added. The perchlorate reduction section used an upflow anaerobic reactor, controlled ORP=-300±20mV, HRT=8h, and supplemented with CH3COO- :ClO4 - = 2:1 molar ratio of sodium acetate.

[0072] After the system has been running stably for 35 days, the denitrification section effluent NO3 - -N=0.05±0.02mg / L (removal rate 99.97%), ClO4 in perchlorate section effluent - =0.9±0.3mg / L (total removal rate 99.7%). TOC of the whole effluent is 8.5±0.9mg / L and no sulfide is generated.

[0073] This embodiment shows that the segmented precise dosing strategy can efficiently distribute the electron flow, which not only solves the competitive inhibition, but also ensures the efficient utilization of carbon sources and avoids secondary pollution.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 2 is that all carbon sources are added to the inlet of the denitrification section at one time, and other parameters (water quality, device and total carbon source addition) are the same as those in Example 2.

[0076] The results showed that the denitrification effluent NO3 - -N=0.1±0.05mg / L (removal rate 99.93%), but excessive carbon source leads to the accumulation of volatile fatty acids (VFA) detected at the inlet of the subsequent perchlorate section, the system pH drops, and the final effluent ClO4 - =98±12 mg / L (total removal rate is only 52%), and methane generation was detected at the same time.

[0077] This result proves that single-point excessive addition leads to a serious imbalance in electron distribution, and perchlorate-reducing bacteria are inhibited due to the lack of effective electron donors.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 2 is that the carbon source addition ratio is adjusted, and other parameters are the same as those in Example 2.

[0080] The first group of experiments (insufficient carbon source): denitrification section CH3COO - :NO3 - -N=0.8:1, perchlorate section CH3COO - :ClO4 - =1.5:1. As a result, due to the serious lack of carbon source, the effluent NO3 - -N rises to 22.3±3.1mg / L (removal rate 85.3%), and the residual nitrate competitively inhibits the activity of perchlorate-reducing bacteria, resulting in ClO4 in the perchlorate section effluent. -As high as 163±11 mg / L (removal rate of only 45.6%), while TOC dropped to 2.1±0.5 mg / L, confirming the lack of electron donors.

[0081] The second group of experiments (carbon source excess): denitrification section CH3COO - :NO3 - -N=1.5:1, perchlorate section CH3COO - :ClO4 - =3:1. As a result, the denitrification section achieved NO3 - -N=0.03±0.01mg / L, but VFA accumulates in the effluent; after this carbon-rich wastewater enters the perchlorate section, it triggers the proliferation of sulfate-reducing bacteria and the surge in the activity of methanogens, resulting in the inhibition of perchlorate-reducing bacteria and the accumulation of ClO4 in the effluent. - =89.2±6.4mg / L (removal rate 70.3%), and the final effluent TOC exceeded the standard to 52.8±4.1mg / L. When the carbon source is insufficient, the pollutant removal rate drops sharply, and when it is excessive, secondary pollution is induced.

[0082] This result proves that the carbon source addition molar ratio proposed in the present invention is the key to achieving high-efficiency and low-consumption treatment.

[0083] Example 3

[0084] Using actual wastewater from fireworks (NO3 - -N=180±10mg / L,ClO4 - =350±12 mg / L), and carried out targeted enrichment and long-term operation according to the method of the present invention.

[0085] The denitrification section was controlled by controlling ORP = -130 ± 20 mV, HRT = 6 h, temperature 30 ± 1 ° C and pH = 7.2 ± 0.3, and increasing the load step by step. Finally, the volume load was 1400 gN / (m 3 d) and stable operation without nitrite accumulation; Propionivibrio, Dethiosulfatibacter and Lentimicrobium functional bacteria were successfully enriched, with a total proportion of 36.8±0.9%. The perchlorate section was controlled by controlling ORP = -310±10mV, HRT = 8h, and step-by-step increasing the load (1200→1900→2250g / (m 3 ·d)), at the final load of 2250g / (m 3 d) under stable operation, with no detection of intermediate products such as chlorate; and successful enrichment of Dechlorosoma, Leptonema, and Ciceribacter functional bacteria, with a total proportion of 43.5±1.2%.

[0086] After the system has been running continuously for 100 days, the denitrification section effluent NO3 - -N=0.07±0.03mg / L, and ClO4 - The pre-removal rate reached 41.2±1.7%; the final effluent ClO4 - =0.2±0.08 mg / L (total removal rate 99.8%). After 30 days without water inflow, the abundance of functional bacteria in the two sections remained above 19.3%, proving that the targeted enrichment strategy gave the system excellent long-term stability.

[0087] Comparative Example 4

[0088] The difference between this comparative example and Example 3 is that: no directional enrichment is performed, ordinary activated sludge is used for startup; and no fine environmental conditions and load gradient control are performed.

[0089] As a result, the volume load of the denitrification section increased directly to 1800gN / (m 3 ·d), exceeding the threshold, resulting in nitrite accumulation in the effluent; the perchlorate section is directly treated at 2800g / (m 3 d) Overload operation leads to a sharp drop in perchlorate removal efficiency;

[0090] In addition, the denitrification effluent NO3 - -N residual content reaches 15.7±3.4mg / L, and there is no ClO4 - Pre-removal capacity; the dominant bacterial community in the perchlorate section is Desulfovibrio (sulfur-reducing bacteria), ClO4 - The effluent concentration rose to 12.3±6.1 mg / L; after the system stopped supplying water for 72 hours, the activity of functional bacteria was irreversibly lost.

[0091] This shows that the targeted enrichment of functional bacteria and the cascade control of pollutant loads in the present invention play a core role in the efficient and stable operation of the system.

[0092] The present invention can have other embodiments according to the above preparation method, which are not listed one by one. Therefore, any simple modification, equivalent change and modification made by any person skilled in the art to the above embodiment according to the technical essence of the present invention without departing from the scope of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for removing perchlorate and nitrate in fireworks wastewater in stages, characterized in that: The following steps are involved: (1) Denitrification removal step: introducing the wastewater containing perchlorate and nitrate into the denitrification reactor, controlling the redox potential in the denitrification reactor to -100 mV to -200 mV by micro-aeration or intermittent aeration; and adding the first portion of carbon source to achieve preferential removal of nitrate; (2) Perchlorate reduction step: introducing the effluent treated in step (1) into a perchlorate reactor; maintaining an anaerobic environment by terminating aeration and selecting a closed anaerobic reactor, controlling the redox potential in the perchlorate reactor to decrease to -250 mV to -350 mV; and adding a second portion of carbon source to achieve perchlorate reduction.

2. The method for removing perchlorate and nitrate in fireworks wastewater according to claim 1, wherein: In the denitrification removal step, the first portion of carbon source is CH3COO in molar ratio - :NO3 - -N=1:1 dosing.

3. The method for removing perchlorate and nitrate in fireworks wastewater according to claim 1, characterized in that: In the perchlorate reduction step, the second portion of carbon source is CH3COO - :ClO4 - =2:1 addition.

4. The method for removing perchlorate and nitrate in fireworks wastewater in stages according to any one of claims 1 to 3, characterized in that: The method further comprises a step of targeted enrichment of functional bacterial flora, wherein: In the denitrification reactor, the hydraulic retention time is controlled to be 3.5±0.2h, the temperature is 30±1°C, and the pH is 7.2±0.3; and the bacterial community having both denitrification and perchlorate reduction functions is enriched in a targeted manner; In the perchlorate reactor, the hydraulic retention time is controlled to be 6.0±0.3h and the temperature is controlled to be 30±1°C; and the perchlorate-reducing bacteria are enriched in a directionally manner.

5. The method for removing perchlorate and nitrate in fireworks wastewater according to claim 4, characterized in that: The bacterial community with both denitrification and perchlorate reduction functions includes Propionivibrio, Dethiosulfatibacter and Lentimicrobium.

6. The method for removing perchlorate and nitrate in fireworks wastewater according to claim 4, characterized in that: The perchlorate-reducing bacteria include Dechlorosoma, Leptonema and Ciceribacter.

7. The method for removing perchlorate and nitrate in fireworks wastewater according to claim 1, characterized in that: The method also includes a pollutant load step control step, which increases the pollutant concentration in a step-by-step manner. NO3 - -N pollutant gradient load increase stage: 800gN / (m 3 ·d)→1200gN / (m 3 ·d)→1400gN / (m 3 ·d), so that the nitrate volume load of the denitrification reactor reaches 1400gN / (m 3 d); ClO4 - Pollutant gradient load increase stage: 1200gClO4 - / (m 3 d) → 1900gClO4 - / (m 3 d) → 2250gClO4 - / (m 3 d) bringing the perchlorate volumetric loading of the perchlorate reactor to 2250 g ClO4 - / (m 3 ·d).

8. The method for removing perchlorate and nitrate in fireworks wastewater according to claim 1, wherein: The denitrification reactor is a baffled reactor; the perchlorate reactor is an upflow anaerobic reactor; the upward flow rate of the upflow anaerobic reactor is 2-3 m / h, and the sludge suspension concentration is maintained at not less than 8 gVSS / L through internal recirculation.

9. The method for removing perchlorate and nitrate in fireworks wastewater according to claim 1, wherein: In the denitrification removal step, the redox potential is controlled to be -130±20 mV; in the perchlorate reduction step, the redox potential is controlled to be -310±10 mV.