Method for gradient removal of perchlorate and nitrate in fireworks and firecracker wastewater

Abstract

This invention discloses a method for the stepwise removal of perchlorate and nitrate from fireworks and firecracker wastewater, comprising the following steps: (1) Denitrification removal step: Wastewater containing perchlorate and nitrate is introduced into a denitrification reactor, and the oxidation-reduction potential in the denitrification reactor is controlled at -100mV to -200mV by micro-aeration or intermittent aeration; and a first part of carbon source is added to achieve preferential removal of nitrate; (2) Perchlorate reduction step: The effluent after treatment in step (1) is introduced into a perchlorate reactor; by terminating aeration and selecting a closed anaerobic reactor, the anaerobic environment is maintained, and the oxidation-reduction potential in the perchlorate reactor is controlled to decrease to -250mV to -350mV; and a second part of carbon source is added to achieve perchlorate reduction. This invention achieves stepwise and efficient removal of perchlorate and nitrate.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for the tiered removal of perchlorate and nitrate from fireworks and firecracker wastewater. Background Technology

[0002] The production process of fireworks and firecrackers produces substances containing high concentrations of perchlorate (ClO4). - ) and nitrates (NO3) - Both perchlorate and nitrate are strong oxidizing pollutants and often exist in the form of compound pollution, 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 carcinogenic, teratogenic, and mutagenic diseases.

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

[0004] However, in systems where the two pollutants coexist, the microbial reduction process suffers from significant competitive inhibition; when electron donors (carbon sources) are limited, when NO3... - -N and ClO4 - When coexisting, denitrifying bacteria typically have a higher affinity for electron donors than perchlorate-reducing bacteria. Denitrifying bacteria preferentially utilize carbon sources, thus inhibiting the metabolic activity of perchlorate-reducing bacteria and resulting in low perchlorate removal efficiency. Excessive addition of carbon sources to ensure perchlorate reduction not only wastes resources but may also lead to excessive total organic carbon in the effluent and even induce side reactions such as sulfate reduction, producing secondary pollutants like hydrogen sulfide. Furthermore, traditional biological treatment processes lack precise control over the microbial metabolic environment, making it difficult to achieve simultaneous and efficient removal of both pollutants. This results in unstable system operation and poor resistance to load shocks.

[0005] Therefore, existing technologies lack a precise control mechanism for electron donor allocation when treating the combined pollution of perchlorate and nitrate in fireworks and firecracker wastewater, and cannot solve the problem of competitive inhibition between the two types of pollutants; they also fail to construct a phased microbial metabolic environment control system, resulting in weak system resistance to shocks and easy microbial inactivation and secondary pollution caused by load fluctuations. Summary of the Invention

[0006] To address the aforementioned technical deficiencies, this invention proposes a method for the stepwise removal of perchlorate and nitrate from fireworks and firecracker wastewater. By optimizing the oxidation-reduction potential (ORP) gradient, the staged addition strategy of carbon source, the targeted enrichment of functional microbial communities, and the stepwise control of pollutant load, the method achieves efficient stepwise removal of perchlorate and nitrate. This solves the problems of low perchlorate removal efficiency, low carbon source utilization, and easy secondary pollution caused by competitive inhibition in existing technologies.

[0007] The method for the tiered removal of perchlorate and nitrate from fireworks and firecracker wastewater of the present invention includes the following steps:

[0008] (1) Denitrification removal step: Wastewater containing perchlorate and nitrate is introduced into the denitrification reactor. The oxidation-reduction potential in the denitrification reactor is controlled to be -100mV to -200mV by micro-aeration or intermittent aeration. The first part of the carbon source is added to achieve preferential removal of nitrate.

[0009] (2) Perchlorate reduction step: The effluent after step (1) is introduced into the perchlorate reactor; by terminating aeration and selecting a closed anaerobic reactor, the anaerobic environment is maintained, and the oxidation-reduction potential in the perchlorate reactor is controlled to decrease to -250mV to -350mV; and a second carbon source is added to achieve perchlorate reduction.

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

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

[0012] Preferably, the method further includes a step of targeted enrichment of functional microbial communities, wherein:

[0013] In the denitrification reactor, the hydraulic retention time was controlled at 3.5±0.2h, the temperature at 30±1℃, and the pH at 7.2±0.3; a bacterial community with both denitrification and perchlorate reduction functions was selectively enriched.

[0014] In the perchlorate reactor, the hydraulic retention time was controlled at 6.0±0.3h and the temperature at 30±1℃; perchlorate-reducing bacteria were selectively enriched.

[0015] Preferably, the bacterial community that combines 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 includes a pollutant load tiered control step, which increases the pollutant concentration in a stepwise manner.

[0018] NO3 - The gradient loading stage for -N pollutants is: 800gN / (m³) 3 ·d)→1200gN / (m 3 ·d)→1400gN / (m 3 ·d)) to achieve a nitrate volumetric loading of 1400 gN / (m³) in the denitrification reactor. 3 ·d);

[0019] ClO4 - The pollutant gradient load enhancement stage is: 1200g ClO4 - / (m 3 ·d)→1900gClO4 - / (m 3 ·d)→2250gClO4 - / (m 3 ·d)) to achieve a perchlorate volumetric loading of 2250 g ClO4 in the perchlorate reactor. - / (m 3 ·d).

[0020] Preferably, the denitrification reactor is a baffle plate reactor; the perchlorate reactor is an upflow anaerobic reactor; the upflow velocity of the upflow anaerobic reactor is 2-3 m / h, and the sludge suspended concentration is maintained at not less than 8 g VSS / L through internal recirculation.

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

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. This invention achieves the separation of metabolic pathways through redox potential gradient regulation, fundamentally solving the problem of competitive inhibition. In the denitrification stage, the ORP is controlled at -100mV to -200mV, creating an optimal metabolic environment for denitrifying bacteria to preferentially and efficiently remove nitrates. Simultaneously, this potential is insufficient to activate perchlorate reductase, thus inhibiting competition. Subsequently, in the perchlorate stage, the ORP is reduced to -250mV to -350mV, creating a dedicated and optimal strong reducing environment for perchlorate reductase bacteria after the removal of nitrate competitors. This invention establishes two clearly defined ORP ranges, solving the problem of competitive inhibition between two types of pollutants.

[0024] 2. This invention achieves efficient distribution of electron donors through segmented and precise carbon source addition, balancing treatment efficiency and economy. In the denitrification stage, it is administered according to CH3COO... - NO3 - Adding electrons at a molar ratio of -N=1:1, "supplying electrons on demand," ensures efficient nitrate removal without carbon source residue; in the perchlorate stage, it is then added according to CH3COO - :ClO4 - A carbon source is supplemented at a molar ratio of 2:1, specifically for perchlorate reduction. This method precisely directs the 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. This invention achieves targeted enrichment of functional microbial communities by controlling specific environmental conditions and pollutant load gradients at different stages. In the denitrification stage, microbial communities with both functionalities are enriched, enhancing the system's adaptability to complex pollution and its pretreatment capabilities; in the perchlorate stage, highly efficient and specific microbial communities are enriched. This "specialized division of labor" microbial ecosystem not only has extremely high treatment efficiency but also possesses strong buffering capacity and resistance to load shocks, ensuring the long-term stable operation of the system.

[0026] 4. This invention increases the pollutant load in a stepped manner, enabling the system to adapt to and stably treat high-concentration wastewater, with volumetric loads of nitrate and perchlorate of 1400 gN / (m³). 3 ·d) and 2250gClO4 - / (m 3 (d) This process far surpasses traditional methods and produces no intermediate product accumulation. Furthermore, by combining flow control (upflow velocity and internal sludge recirculation) with the upflow anaerobic reactor, this invention effectively retains high-concentration functional sludge and enhances mass transfer efficiency. In other words, this invention possesses the ability to operate stably under high load conditions, demonstrating significant potential for industrial application. Detailed Implementation

[0027] To better understand the content of this invention, specific embodiments will be used to further illustrate the invention below. The following embodiments are based on the technology of this invention and provide detailed implementation methods and operating steps. However, the scope of protection of this invention is not limited to the following embodiments; that is, all other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] The method for the tiered removal of perchlorate and nitrate from fireworks and firecracker wastewater of the present invention includes the following steps:

[0029] (1) Denitrification removal step: Wastewater containing perchlorate and nitrate is introduced into the denitrification reactor. The oxidation-reduction potential (ORP) in the denitrification reactor is precisely controlled to be -100mV to -200mV through micro-aeration or intermittent aeration. Within this ORP range, the ubiquinone-cytochrome c electron transport chain of denitrifying bacteria reaches the optimal reduction state, improving the efficiency of NADH electron carrier transport to the enzyme system; maximizing the utilization of the reductive metabolic activity and electron donor supply of microorganisms, nitrate can be efficiently reduced to nitrogen gas without nitrite accumulation; at the same time, the activity of perchlorate-reducing bacteria is inhibited, avoiding their competition 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 no lower than -200mV to avoid excessive reduction and activation of perchlorate-reducing bacteria, and to prevent 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 oxidation-reduction 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, which can create a strong reducing environment and enhance the metabolic activity of perchlorate-reducing bacteria.

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

[0033] In any embodiment of the present invention, the denitrification reactor is a baffle-type reactor, which has a baffle-type multi-stage reaction zone and a vertical flow sedimentation zone, and a built-in low-speed stirrer to maintain an oxygen-deficient environment; the perchlorate reactor is an upflow anaerobic reactor, which has a biological reaction zone and a sedimentation zone.

[0034] In the denitrification reactor, the redox potential was controlled at -130±20mV, the hydraulic retention time at 3.5±0.2h, the temperature at 30±1℃, and the pH at 7.2±0.3. Simultaneously, a first part of the carbon source was added at the inlet, and by controlling the carbon-nitrogen ratio, a bacterial community of Propionivibrio, Dethiosulfatibacter, and Lentimicrobium, which have both denitrification and perchlorate partial reduction functions, was selectively enriched; thereby improving the treatment capacity and stability of complex pollutants.

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

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

[0037] After 40 days of enrichment, qPCR analysis showed that the proportions of Dechlorosoma, Leptonema, and Ciceribacter were 18.4±2.8%, 7.7±1.6%, and 5.9±1.1%, respectively, achieving highly efficient perchlorate removal. The average perchlorate removal rate was 99±0.2%, and the system's resistance to load shocks was also significantly improved (ClO4 concentration fluctuated by ±30%). - Removal rate > 99.5%.

[0038] In any embodiment of the present invention, in the denitrification removal step, the first portion of the carbon source is CH3COO in molar ratio. - NO3 - -N = 1:1 addition; used to prioritize the needs of denitrification reaction, ensuring nitrate removal rate >99% and no carbon source waste; in the perchlorate reduction step, the second part of the carbon source is CH3COO in molar ratio - :ClO4 -The ratio of carbon source to carbon is 2:1, which is used to ensure the electron donor required for perchlorate reduction, while avoiding excessive carbon source that would lead to residual organic matter in the effluent; the preferred carbon source is sodium acetate.

[0039] In any embodiment of the present invention, the denitrification removal step further includes NO3. - -N pollutant gradient load enhancement control and ClO4 - Pollutant gradient load enhancement control; the NO3 - The N-pollutant gradient loading process consists of three stages. Stage I: Initial 800 gN / (m³) 3 ·d), Stage II: 1200 gN / (m) on day 20 3 ·d), Stage III: 1400 gN / (m) on day 40 3 •d)); Volumetric load gradient control is achieved by gradually increasing the influent nitrate concentration at 1400 gN / (m³). 3 ·d) NO3 in effluent under load - -N = 0.02 ± 0.05 mg / L, nitrite did not accumulate, and this load threshold can ensure the integrity of denitrification.

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

[0041] This invention increases the concentration of pollutants in the influent in a stepwise manner; the nitrate volumetric loading of the denitrification reactor can be stabilized at 1400 gN / (m³). 3 ·d) The perchlorate volumetric loading of the perchlorate reactor can be stabilized at 2250 g ClO4 - / (m 3 ·d) Under this load, the system can still maintain a high efficiency and stable removal effect, and there is no accumulation of intermediate products such as nitrite or chlorate.

[0042] The upward flow velocity of the upflow anaerobic reactor is 2–3 m / h, while the sludge suspended concentration is maintained at no less than 8 g VSS / L through internal reflux. This flow pattern control and oxidation-reduction potential regulation create a synergistic effect, enhancing the sludge-water mass transfer efficiency, preventing sludge loss, and ensuring the retention of high-concentration functional microbial communities.

[0043] To further understand the technical solution of the present invention, the following embodiments are provided;

[0044] Example 1

[0045] The characteristics of the test water quality are as follows: ClO4 - The concentration was 308±5.6 mg / L, NO3 - -N concentration: 157±4.2 mg / L. The experimental environment temperature was 25℃. The experimental apparatus was a baffle-type reactor made of plexiglass. The total HRT of the apparatus was 10 h, and the total influent flow rate was 0.5 L / h.

[0046] In the denitrification reactor stage, three parallel experiments were set up using micro-aeration or intermittent aeration methods, with ORP precisely controlled at -120±20mV, -150±20mV and -180±20mV respectively, and each group running for an average of 20 days.

[0047] During the perchlorate reduction stage, the test water was the effluent after denitrification treatment, and the ClO4 content was measured. - The concentration was 305±5.2 mg / L, NO3 - -N concentration 30±1.5mg / L, SO4 - With a concentration of 101±4.3 mg / L, three parallel experiments were set up by controlling the nitrogen purging and the upward flow rate. The ORP was precisely controlled at -230±20 mV, -300±20 mV and -330±20 mV respectively, and each group was run for an average of 20 days.

[0048] After the system stabilized, the results are as follows:

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

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

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

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

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

[0054] ORP at -330±20mV, 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 in this invention can achieve efficient and stable removal of nitrates 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 settings are -300±20mV, -50±20mV, +50±20mV and +150±20mV, respectively, while other parameters are the same as in Example 1.

[0058] During the perchlorate reduction stage, the ORP settings were -200±20mV, -100±20mV, and -400±20mV, respectively, with other parameters being the same as in Example 1.

[0059] Experimental results show that:

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

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

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

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

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

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

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

[0067] The results of Comparative Example 1 demonstrate that excessively low ORP (e.g., -300mV) in the denitrification reactor stage leads to unnecessary carbon source competition, while excessively high ORP (≥-50mV) results in inhibited denitrifying enzyme activity, reduced electron transport chain efficiency, and inability to maintain efficient nitrate removal; the removal efficiency is significantly lower than that of Example 1.

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

[0069] Example 2

[0070] In a laboratory continuous flow experiment, this invention employs a two-stage bioreactor to treat nitrate-containing (NO3) compounds. - -N=150±5mg / L) and perchlorate (ClO4) - Simulated wastewater (300±10mg / L).

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

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

[0073] This embodiment demonstrates that the segmented and precise dosing strategy can efficiently allocate electron flow, solving the problem of competitive suppression, ensuring efficient utilization of carbon sources, and avoiding 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 once, while other parameters (water quality, equipment, and total carbon source dosage) are the same as in Example 2.

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

[0077] This result demonstrates that excessive addition at a single point leads to a severe imbalance in electron distribution, and perchlorate-reducing bacteria are inhibited due to a 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, while all other parameters are the same as in Example 2.

[0080] Group 1 Experiment (Insufficient Carbon Source): Denitrification Section CH3COO - NO3 - -N = 0.8:1, perchlorate segment CH3COO - :ClO4 - =1.5:1. As a result, due to a severe shortage of carbon source, NO3 in the effluent from the denitrification section... - -N increased to 22.3±3.1 mg / L (removal rate 85.3%), and residual nitrate competitively inhibited the activity of perchlorate-reducing bacteria, leading to an increase in ClO4 in the effluent from the perchlorate stage. -The concentration of saturated plasma was as high as 163±11 mg / L (with a removal rate of only 45.6%), while the total oxygen concentration (TOC) decreased to 2.1±0.5 mg / L, confirming the scarcity of electron donors.

[0081] Group 2 Experiments (Excess Carbon Source): Denitrification Section CH3COO - NO3 - -N = 1.5:1, perchlorate segment CH3COO - :ClO4 - =3:1. As a result, although the denitrification stage achieved NO3... - -N = 0.03 ± 0.01 mg / L, but VFA accumulates in the effluent; after this carbon-rich wastewater enters the perchlorate stage, it triggers the proliferation of sulfate-reducing bacteria and a surge in methanogenic bacteria activity, leading to the inhibition of perchlorate-reducing bacteria and a decrease in effluent ClO4. - =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, it induces secondary pollution.

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

[0083] Example 3

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

[0085] The denitrification stage was controlled by adjusting ORP to -130±20mV, HRT to 6h, temperature to 30±1℃, and pH to 7.2±0.3, with a stepwise increase in loading, ultimately achieving a volumetric loading of 1400gN / (m³). 3 Stable operation was achieved under d) conditions with no nitrite accumulation; the functional bacterial communities of Propionivibrio, Dethiosulfatibacter, and Lentimicrobium were successfully enriched, with a total proportion of 36.8±0.9%. The perchlorate stage was controlled by adjusting ORP to -310±10mV and HRT to 8h, and by gradually increasing the loading rate (1200→1900→2250g / (m²)). 3 ·d)), at a final load of 2250g / (m 3 •d) Stable operation with no intermediate products such as chlorate detected; successfully enriched functional bacterial groups of Dechlorosoma, Leptonema and Ciceribacter, with a total proportion of 43.5±1.2%.

[0086] After the system ran continuously for 100 days, the NO3 in the effluent from the denitrification section... - -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 of stopping the influent, the abundance of functional bacteria in both stages remained above 19.3%, demonstrating that the targeted enrichment strategy endowed the system with excellent long-term stability.

[0087] Comparative Example 4

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

[0089] As a result, the volumetric loading of the denitrification section directly increased to 1800 gN / (m³). 3 ·d), exceeding the threshold, leading to nitrite accumulation in the effluent; the perchlorate stage directly discharges 2800g / (m 3 •d) Overloading operation led to a sharp decline in perchlorate removal rate;

[0090] In addition, NO3 in the effluent from the denitrification section - -N residue reached 15.7±3.4 mg / L, and ClO4 was absent. - Pre-removal capacity; the dominant bacterial community in the perchlorate zone evolves to Desulfovibrio (sulfur-reducing bacteria), ClO4 - The effluent concentration rose to 12.3±6.1 mg / L; after the system stopped receiving water for 72 hours, the activity of the functional bacteria was irreversibly lost.

[0091] Therefore, it can be seen that the targeted enrichment of functional microbial communities and the tiered control of pollutant load are the core elements for the efficient and stable operation of the system in this invention.

[0092] This invention can have other embodiments based on the above preparation method, which will not be listed one by one. Therefore, any simple modifications, equivalent changes and alterations made by any person skilled in the art to the above embodiments without departing from the scope of the technical solution of this invention shall still fall within the scope of the technical solution of this invention.

Claims

1. A method for the stepwise removal of perchlorate and nitrate from fireworks and firecracker wastewater, characterized in that, Includes the following steps: (1) Denitrification removal step: Wastewater containing perchlorate and nitrate is introduced into the denitrification reactor. The oxidation-reduction potential in the denitrification reactor is controlled at -100mV to -200mV by micro-aeration or intermittent aeration. A first part of the carbon source is added to achieve preferential removal of nitrate. The first part of the carbon source is CH3COO at a molar ratio. - NO3 - -N=1:1 addition; (2) Perchlorate reduction step: The effluent treated in step (1) is introduced into the perchlorate reactor; by terminating aeration and selecting a closed anaerobic reactor, the anaerobic environment is maintained, and the oxidation-reduction potential in the perchlorate reactor is controlled to decrease to -250mV~-350mV; and a second carbon source is added to achieve perchlorate reduction; the second carbon source is added in molar ratio CH3COO - :ClO4 - =2:1 ratio for addition; The method further includes a step of targeted enrichment of functional microbial communities, wherein: In the denitrification reactor, the hydraulic retention time was controlled at 3.5±0.2h, the temperature at 30±1℃, and the pH at 7.2±0.3; a bacterial community with both denitrification and perchlorate reduction functions was selectively enriched. In the perchlorate reactor, the hydraulic retention time was controlled at 6.0±0.3h and the temperature at 30±1℃; perchlorate-reducing bacteria were selectively enriched. The method also includes a pollutant load tiered control step, which increases the pollutant concentration in a stepwise manner. NO3 - The gradient loading stage for -N pollutants is: 800gN / (m³) 3 ·d) →1200gN / (m 3 ·d) →1400gN / (m 3 ·d), so that the nitrate volumetric loading of the denitrification reactor reaches 1400 gN / (m³). 3 ·d); ClO4 - The pollutant gradient load enhancement stage is: 1200g ClO4 - / (m 3 ·d) →1900gClO4 - / (m 3 ·d) → 2250gClO4 - / (m 3 ·d), to make the perchlorate volumetric loading of the perchlorate reactor reach 2250gClO4. - / (m 3 ·d).

2. The method for the tiered removal of perchlorate and nitrate from fireworks and firecracker wastewater as described in claim 1, characterized in that, The bacterial community that combines denitrification and perchlorate reduction functions includes Propionivibrio, Dethiosulfatibacter, and Lentimicrobium.

3. The method for the tiered removal of perchlorate and nitrate from fireworks and firecracker wastewater as described in claim 1, characterized in that, The perchlorate-reducing bacteria include Dechlorosoma, Leptonema, and Ciceribacter.

4. The method for the tiered removal of perchlorate and nitrate from fireworks and firecracker wastewater as described in claim 1, characterized in that, The denitrification reactor is a baffle plate reactor; the perchlorate reactor is an upflow anaerobic reactor; the upflow velocity of the upflow anaerobic reactor is 2~3m / h, and the sludge suspended concentration is maintained at not less than 8gVSS / L through internal recirculation.

5. The method for the tiered removal of perchlorate and nitrate from fireworks and firecracker wastewater as described in claim 1, characterized in that, In the denitrification removal step, the oxidation-reduction potential is controlled at -130±20mV; in the perchlorate reduction step, the oxidation-reduction potential is controlled at -310±10mV.