Method for controlling disinfection by-products and biological toxicity of sewage based on denitrification process optimization and application

Abstract

The application discloses a method for controlling disinfection by-products and biological toxicity of sewage based on a denitrification process and application in the technical field of sewage treatment, and aims at the problems that toxic disinfection by-products DBPs are easily generated and the biological toxicity of effluent is increased after the sewage is disinfected by adding chlorine. The carbon-nitrogen ratio, the hydraulic retention time and the temperature in the deep denitrification process are optimized in cooperation, the optimal coupling relationship between the temperature and the hydraulic retention time is explored, the regulation and control path of "process parameters-precursor-DBPs-toxicity" is established, the source control of DBPs is realized, and the biological toxicity of effluent is reduced. The application starts from the optimization of operation parameters in the sewage treatment process, does not need to add chemical agents or add complex equipment, can significantly reduce the ecological risk of the subsequent disinfection link while ensuring the denitrification effect, is simple to operate, low in cost, and suitable for the process optimization and upgrading of the existing sewage treatment plant.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to methods and applications for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification processes. Background Technology

[0002] Disinfection is a necessary process for urban wastewater treatment plants to kill pathogenic microorganisms and ensure the hygiene and safety of effluent. Chlorination disinfection is widely used due to its low cost and reliable effect. However, chlorine disinfectant inevitably reacts with organic matter in wastewater to generate disinfection byproducts (DBPs). Currently, more than 700 types of DBPs have been detected, many of which have been proven to have genotoxicity, cytotoxicity, and developmental toxicity. In addition to the controlled trihalomethanes and haloacetic acids, nitrogen-containing DBPs (N-DBPs) such as haloacetonitrs and halonitromethanes are also of great concern due to their higher toxicity. Furthermore, AOX (a comprehensive indicator of halogenated DBPs) and the comprehensive biotoxicity of chlorinated effluent, as key indicators for a more comprehensive assessment of the ecological risks of chlorination disinfection, also need to be controlled.

[0003] To control DBPs and biotoxicity in wastewater, in addition to optimizing the disinfection process itself (such as the type and dosage of disinfectant), reducing DBP precursors at the source is a more fundamental and effective strategy. Deep denitrification, as a tertiary treatment process, is widely used in urban wastewater treatment plants to remove nitrogen to meet increasingly stringent total nitrogen emission requirements. This process is usually located at the end of biological treatment and before the disinfection process, and the optimization of its operating parameters plays a key role in the removal of DBP precursors.

[0004] Carbon source type, carbon-to-nitrogen ratio (C / N), and hydraulic retention time (HRT) are the core process parameters for deep denitrification. Previous studies have found that, compared with sodium acetate, using glucose as an external carbon source can significantly reduce the formation potential of carbon-containing DBPs (C-DBPs), N-DBPs, and AOX, as well as biotoxic effects such as acute toxicity and genotoxicity. However, regarding C / N and HRT, existing studies mainly focus on the impact of these process parameters on denitrification efficiency and / or the properties of effluent organic matter (EfOM). As an important precursor of wastewater DBPs, EfOM is presumably expected to have a significant impact on DBPs and biotoxicity caused by subsequent disinfection processes due to C / N and HRT, but there are few reports on this. Among them, Li Xiaoshuang qualitatively studied the impact of HRT on the types and relative concentrations of chlorinated DBPs in the effluent of a sequencing batch reactor using Fourier transform ion cyclotron resonance high-resolution mass spectrometry. However, there is still a lack of systematic research on the control effects of controlled trihalomethanes and haloacetic acids, highly toxic N-DBPs, and the comprehensive indicator AOX. In addition, there is a lack of in-depth analysis and related mechanism studies of key toxic factors in chlorinated effluent.

[0005] Therefore, developing a method based on denitrification process optimization that can synergistically control the generation of multiple DBPs from the source and reduce the biotoxicity of chlorinated effluent, and exploring the regulation pathway of "process parameters-precursors-DBPs-toxicity", is of great significance for improving the ecological safety of wastewater treatment plant effluent. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned technical problems by providing a method and application for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process. This method systematically examines and optimizes the C / N ratio of the denitrification process, establishes a temperature-based HRT dynamic control strategy, explores the control mechanism, reduces the concentration of DBPs precursors from the source of the process, reduces the formation potential and biotoxicity of DBPs and AOX, and reduces the ecological risks caused by disinfection while ensuring the denitrification effect.

[0007] The present invention achieves the above objectives through the following technical solutions: As a first aspect of the present invention, a method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process is also provided. Before chlorinating wastewater for disinfection, the wastewater is first subjected to denitrification treatment. During the denitrification treatment, the carbon-nitrogen ratio of the denitrification process is controlled to be 3-6, and the hydraulic retention time is dynamically adjusted within the range of 7h-24h according to the reaction temperature of the denitrification process to form a temperature-HRT synergistic optimization strategy, so as to reduce disinfection byproducts and biotoxicity after wastewater chlorination disinfection.

[0008] After the wastewater was denitrified, its effluent was further characterized by three-dimensional fluorescence. The denitrified effluent contained fluorescent components such as tryptophan-like and humic substances. Analysis showed that the fluorescent components such as tryptophan-like and humic substances in the denitrified effluent were key precursors of AOX. After chlorination disinfection of denitrification effluent, the generation potential of DBPs and AOX was determined. Simultaneously, the toxicity of the disinfected effluent was assessed after enrichment and concentration using the acute toxicity test for luminescent bacteria. Analysis showed a significant linear positive correlation between AOX generation potential and acute toxicity of luminescent bacteria (r=0.962, p<0.001), confirming that AOX, as a comprehensive indicator of halogenated DBPs, is a key factor driving the non-specific acute toxicity of luminescent bacteria in chlorinated effluent.

[0009] As a further optimization of the present invention, the carbon-to-nitrogen ratio of the denitrification process is controlled to be 6.

[0010] As a further optimization of the present invention, the carbon-nitrogen ratio control method of the denitrification process is as follows: glucose is added to the wastewater according to the initial nitrate nitrogen concentration to achieve carbon-nitrogen ratio control of the denitrification process.

[0011] As a further optimization of the present invention, under the conditions of a reaction temperature of 10-30℃ and dissolved oxygen less than 0.5mg / L (strict anoxic conditions to ensure normal metabolism of denitrifying bacteria), sludge is inoculated into wastewater for denitrification treatment. The denitrification treatment process ends when the nitrate nitrogen concentration in the wastewater drops below 3mg / L or is completely degraded. Complete degradation means that the nitrate nitrogen concentration in the wastewater is lower than the detection limit (approximately equal to the nitrate nitrogen concentration dropping to 0mg / L), to ensure the denitrification effect and define the reaction endpoint.

[0012] As a further optimization of the present invention, when the denitrification reaction temperature is 30°C, the hydraulic retention time is controlled to be 7 hours; when the denitrification reaction temperature is 20°C, the hydraulic retention time is controlled to be 7 hours; and when the denitrification reaction temperature is 10°C, the hydraulic retention time is controlled to be 16 hours.

[0013] As a further optimization of the present invention, the concentration of suspended solids in the mixed liquor of the sludge is 2000-4000 mg / L, and the sludge is preferably from a municipal wastewater treatment plant (such as A). 2 / O process) anoxic tank sludge.

[0014] As a further optimization of the present invention, the wastewater chlorination disinfection method is as follows: first, the pH of the effluent of the wastewater after denitrification treatment is buffered to 7.0±0.2, then sodium hypochlorite is added to the wastewater, and the mixture is reacted at 25°C in the dark for 7 days. After disinfection, a quenching agent is added to the wastewater to quench the residual chlorine.

[0015] As a further optimization of the present invention, the biotoxicity is evaluated using the acute toxicity test method for luminescent bacteria. To improve the detection sensitivity, the chlorinated effluent is usually enriched and concentrated before testing.

[0016] As a further optimization of the present invention, the disinfection byproducts include trihalomethanes, haloacetic acids, hydrated trichloroacetaldehyde, haloketones, haloacetonitrs, and halonitromethanes.

[0017] As a further optimization of the present invention, the trihalomethane includes trichloromethane, monobromodichloromethane, dibromochloromethane, and tribromomethane; The haloacetic acids include monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, tribromoacetic acid, monobromomonochloroacetic acid, monobromodichloroacetic acid, and dibromomonochloroacetic acid; The haloketones include 1,1-dichloropropanone and 1,1,1-trichloropropanone; The haloacetonitrs include monochloroacetonitrile, dichloroacetonitrile, trichloroacetonitrile, monobromoacetonitrile, dibromoacetonitrile, tribromoacetonitrile, monobromochloroacetonitrile, monobromodichloroacetonitrile, and dibromochloroacetonitrile; The halonitromethanes include monochloronitromethane, dichloronitromethane, trichloronitromethane, monobromonitromethane, dibromonitromethane, monobromo-monochloronitromethane, and monobromo-dichloronitromethane.

[0018] As a second aspect of the present invention, the application of the method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process as described in any of the above claims in the harmless treatment of wastewater is also provided.

[0019] By implementing the above-mentioned optimization method of the present invention, under normal or low temperature conditions, the generation potential of representative DBPs such as trihalomethanes, haloacetic acids, and trichloronitromethanes is reduced by an average of 44% compared to the "denitrification-chlorination disinfection" process without process parameter optimization, AOX is reduced by an average of 65%, and the acute toxicity of luminescent bacteria is reduced by an average of 83%.

[0020] The beneficial effects of this invention are as follows: (1) Source control with a clear mechanism: This invention starts with the optimization of internal parameters of the denitrification process. By changing conditions such as C / N, HRT and temperature, a complete action path of "process parameters regulate fluorescent precursors → affect AOX generation → determine effluent toxicity" is established, thus realizing source control of DBPs and toxicity.

[0021] (2) Simple operation and low cost: This invention only optimizes and adjusts the process parameters of the existing denitrification process unit. It does not require the addition of additional chemical agents, the addition of expensive deep treatment facilities, or changes to the existing disinfection process. It is easy to implement in existing sewage treatment plants, and the modification and operation costs are low.

[0022] (3) Ensure denitrification and achieve dual benefits: When proposing an ecological risk control strategy, this invention fully considers the core function of denitrification. The recommended C / N and HRT are based on ensuring the effective removal of nitrate nitrogen, thus achieving the dual goals of "high-efficiency denitrification" and "low toxicity risk" and improving the overall environmental benefits of the process. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the effects of different C / N ratios on the generation potential of DBPs and AOX in chlorinated effluent and the acute toxicity of luminescent bacteria, as provided in Example 1 of the present invention. Figure 2 This is a schematic diagram illustrating the effects of different HRTs on the generation potential of DBPs and AOX in chlorinated effluent and the acute toxicity of luminescent bacteria at 30°C with a fixed C / N ratio of 6, as provided in Embodiment 2 of the present invention. Figure 3 This is a schematic diagram illustrating the effects of different HRTs on the generation potential of DBPs and AOX in chlorinated effluent and the acute toxicity of luminescent bacteria at 20°C with a fixed C / N ratio of 6, as provided in Embodiment 3 of the present invention. Figure 4 This is a schematic diagram illustrating the effects of different HRTs on the generation potential of DBPs and AOX in chlorinated effluent and the acute toxicity of luminescent bacteria at 10°C with a fixed C / N ratio of 6, as provided in Example 4 of the present invention. Figure 5 This is a linear positive correlation diagram between AOX generation potential and acute toxicity of luminescent bacteria provided in Example 5 of the present invention; Figure 6 This is a linear positive correlation diagram between the fluorescent component and AOX provided in Example 6 of the present invention; Figure 7 This is a schematic diagram showing the AOX generation potential and acute toxicity of luminescent bacteria at 20°C when the C / N ratio is 3 and 6, as provided in Comparative Example 1 of the present invention. Figure 8 This is a schematic diagram showing the AOX generation potential and acute toxicity of luminescent bacteria at 10°C and C / N ratios of 3 and 6, as provided in Comparative Example 2 of this invention. Detailed Implementation

[0024] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0025] This embodiment aims to investigate and optimize the effects of C / N ratio on DBPs and AOX generation and the acute toxicity of luminescent bacteria.

[0026] 1. Simulated wastewater preparation Using the Class A standard for total nitrogen in the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918-2002) as a reference, simulated wastewater with a nitrate nitrogen concentration of 15 mg / L was prepared. Glucose was used as the external carbon source, with C / N ratios set to 3, 4, 5, and 6, corresponding to glucose concentrations of 42.2, 56.3, 70.3, and 84.4 mg / L, respectively. In addition, each liter of simulated wastewater contained 25.0 mg KH₂PO₄, 29.0 mg MgSO₄·7H₂O, 100.0 mg NaHCO₃, 0.4 mg ZnSO₄, 0.5 mg CoCl₂·6H₂O, and 0.3 mg MnCl₂·4H₂O. The initial pH of the simulated wastewater was adjusted to 7.2 ± 0.1 using dilute acid or dilute alkali.

[0027] 2. Denitrification and chlorination disinfection Sludge from anoxic tanks of wastewater treatment plants was inoculated into simulated wastewater (the mixed liquor suspended solids (MLSS) concentration in the sludge was controlled within the common range of 2000-4000 mg / L, and in this embodiment, it was preferably controlled at ≈2000 mg / L). Denitrification was carried out at 30°C and dissolved oxygen less than 0.5 mg / L until the nitrate nitrogen concentration was less than 3 mg / L or completely degraded. Complete degradation means that the nitrate nitrogen concentration in the wastewater is lower than the detection limit (approximately equal to the nitrate nitrogen concentration dropping to 0 mg / L). In addition, the HRT during denitrification was determined to be 7 hours through preliminary experiments. After the reaction was completed, the supernatant was taken, its pH was buffered to 7.0±0.2, the effective chlorine concentration was determined according to the following formula, sodium hypochlorite solution was added, and the residual chlorine was quenched after reacting at 25°C in the dark for 7 days.

[0028] NaClO (mg-Cl2 / L) = 3×DOC (mg / L) + 8×NH3-N (mg / L) + 5×NO2-N (mg / L) + 10; where DOC refers to organic matter; NH3-N refers to ammonia nitrogen; and NO2-N refers to nitrite.

[0029] 3. Chemical detection and biotoxicity testing Disinfected water samples were collected, and the generation potential of 32 halogenated DBPs and AOX, as well as the acute toxicity of luminescent bacteria, were determined.

[0030] The 32 halogenated DBPs include 4 trihalomethanes (trichloromethane, bromodichloromethane, dibromochloromethane, tribromomethane), 9 haloacetic acids (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, tribromoacetic acid, monobromochloroacetic acid, monobromodichloroacetic acid, dibromochloroacetic acid), trichloroacetaldehyde hydrate, 2 haloketones (1,1-dichloroacetone, 1,1,1-trichloroacetone), and 9 haloacetonits (monochloroacetonitrile, dichloroacetonitrile, tri ... The study includes chloroacetonitrile, monobromoacetonitrile, dibromoacetonitrile, tribromoacetonitrile, monobromochloroacetonitrile, monobromodichloroacetonitrile, and dibromochloroacetonitrile, as well as seven halonitromethanes (monochloronitromethane, dichloronitromethane, trichloronitromethane, monobromonitromethane, dibromonitromethane, monobromochloronitromethane, and monobromodichloronitromethane); among which, trihalomethanes, haloacetic acids, hydrated trichloroacetaldehyde, and haloketones are C-DBPs, while haloacetonitrile and halonitromethanes are N-DBPs.

[0031] Sample pretreatment methods for trihalomethanes, hydrated trichloroacetaldehyde, haloketones, haloacetonitrs, and halonitromethanes were performed according to US EPA 551.1, and analysis was conducted using gas chromatography-mass spectrometry. Sample pretreatment methods for haloacetic acids were performed according to USEPA 552.2, and analysis was conducted using gas chromatography. The determination of AOX was performed according to the standard method "Determination of Adsorbable Organic Halogens (AOX) in Water by Ion Chromatography" (HJ / T83-2001).

[0032] Prior to the toxicity test, the concentrated denitrified effluent after chlorination was enriched using an automated solid-phase extraction device at an enrichment factor of 4000 times. Then, acute toxicity was determined using luminescent bacteria (Vibrio fischeri), and the results were expressed in toxicity units (TUa).

[0033] The results are as follows Figure 1 As shown, under the condition of C / N ratio of 6, although the C-DBPs generation potential is high, the N-DBPs (the main toxic substance) generation potential, AOX generation potential, and acute toxicity of luminescent bacteria show the best overall performance among all C / N conditions, resulting in lower overall ecological risk. Furthermore, the differences between N-DBPs and AOX are not significant when C / N is 5 and 6. Combined with the fact that the acute toxicity of luminescent bacteria is lowest when C / N is 6, the optimal C / N ratio is determined to be 6, considering both denitrification effect and risk control.

[0034] Example 2 This embodiment aims to investigate the effects of HRT on the generation of DBPs and AOX and the acute toxicity of luminescent bacteria at 30°C.

[0035] Except for the fixed C / N ratio of 6, the other components of the simulated wastewater and their preparation methods are the same as in Example 1; the denitrification inoculation sludge and initial conditions are also the same as in Example 1; the reaction temperature is kept constant at 30°C, and three HRT gradients of 7h, 16h and 24h are set; the reaction endpoint is determined by reaching the set HRT, and the nitrate nitrogen concentration is confirmed to be below 3mg / L at the end.

[0036] After denitrification, the steps and conditions for chlorination disinfection, DBPs and AOX detection, and acute toxicity testing of luminescent bacteria were the same as in Example 1.

[0037] The results are as follows Figure 2 As shown, extending the HRT (e.g., 24h) at 30℃ can reduce the formation of C-DBPs, N-DBPs, and AOX, as well as the acute toxicity of luminescent bacteria. However, considering that extending the HRT to 24h will significantly increase the operating cost of the wastewater treatment plant, and that the AOX formation potential and the acute toxicity of luminescent bacteria are only 18% and 16% lower than those with an HRT of 7h, respectively, the optimal HRT was ultimately determined to be 7h at 30℃, taking into account both operating costs and risk control.

[0038] Example 3 This embodiment aims to investigate the effects of HRT on the generation of DBPs and AOX and the acute toxicity of luminescent bacteria at 20°C.

[0039] Except for keeping the denitrification reaction temperature constant at 20℃, the composition of the simulated wastewater, the denitrification inoculated sludge, and the initial conditions were the same as in Example 2. Three HRT gradients of 7h, 16h, and 24h were set. The reaction endpoint was determined by reaching the set HRT, and the nitrate nitrogen concentration was confirmed to be below 3mg / L at the end.

[0040] After denitrification, the steps and conditions for chlorination disinfection, DBPs and AOX detection, and acute toxicity testing of luminescent bacteria were the same as in Example 1.

[0041] The results are as follows Figure 3 As shown, a shorter HRT (e.g., 7h) at 20℃ can significantly reduce the generation of C-DBPs, N-DBPs and AOX, as well as the acute toxicity of luminescent bacteria. Therefore, the optimal HRT at 20℃ is determined to be 7h. In addition, comparative example 2 ( Figure 2 The results show that, under the same C / N ratio conditions, lowering the denitrification reaction temperature and prolonging the HRT does not further reduce the formation of C-DBPs, N-DBPs, and AOX, nor the acute toxicity of luminescent bacteria. This is mainly related to the properties of precursor substances (such as fluorescent components) in the denitrification effluent.

[0042] Example 4 This embodiment aims to investigate the effects of HRT on DBPs and AOX generation and acute toxicity of luminescent bacteria at 10°C.

[0043] Except for keeping the denitrification reaction temperature constant at 10°C, the composition of the simulated wastewater, the denitrification inoculated sludge, and the initial conditions are the same as in Example 2. Since the denitrification rate is slower at low temperatures, only two HRT gradients of 16h and 24h are set. The reaction endpoint is determined by reaching the set HRT, and the nitrate nitrogen concentration is confirmed to be below 3mg / L or completely degraded at the end.

[0044] After denitrification, the steps and conditions for chlorination disinfection, DBPs and AOX detection, and acute toxicity testing of luminescent bacteria were the same as in Example 1.

[0045] The results are as follows Figure 4 As shown, a shorter HRT (e.g., 16h) at 10℃ can significantly reduce the generation of C-DBPs, N-DBPs and AOX, as well as the acute toxicity of luminescent bacteria. Therefore, the optimal HRT at 10℃ is determined to be 16h.

[0046] Example 5 This embodiment aims to analyze the intrinsic relationship between AOX as a comprehensive indicator and biotoxicity.

[0047] Experimental data obtained from Examples 1 to 4 at all different C / N, HRT and temperatures were summarized. The correlation between AOX generation potential and acute toxicity of luminescent bacteria was analyzed in detail using statistical software for linear regression analysis.

[0048] The results are as follows Figure 5 As shown, there is a significant linear positive correlation between AOX generation potential and acute toxicity of luminescent bacteria (r=0.962, p<0.001); this confirms that AOX, as a comprehensive indicator of halogenated DBPs, is a key factor driving the acute toxicity of non-specific luminescent bacteria in chlorinated effluent; therefore, reducing AOX generation through process optimization can directly and effectively reduce the overall biotoxicity risk of chlorinated effluent.

[0049] Example 6 This embodiment aims to elucidate the intrinsic relationship between the fluorescence characteristics of denitrification effluent and the AOX formation potential, and to reveal the regulatory mechanism of process parameter optimization on AOX and toxicity.

[0050] The samples were derived from all denitrification effluents obtained in Examples 1 to 4 at different C / N ratios, HRTs, and temperatures.

[0051] The denitrification effluent samples were uniformly diluted with ultrapure water to a dissolved organic carbon concentration of 5 mg / L to eliminate the internal filtration effect. Then, the three-dimensional fluorescence excitation-emission matrix (EEM) spectra of each sample were acquired using a fluorescence spectrometer. The detection parameters were: excitation wavelength 200-450 nm, step size 5 nm; emission wavelength 280-550 nm, step size 5 nm. Parallel factor analysis was used to model and analyze the EEM spectral dataset to determine that the denitrification effluent contained fluorescent components such as tryptophan-like and humic acid-like substances.

[0052] The maximum fluorescence intensity (Fmax) of each fluorescent component in each sample was obtained by model calculation, and the intrinsic relationship between the fluorescent components and AOX was analyzed.

[0053] The results are as follows Figure 6 As shown, there is a significant linear positive correlation between the total Fmax of fluorescent components such as tryptophan-like and humic-like substances and the AOX formation potential (r=0.962, p<0.001). This confirms that these fluorescent substances are key precursors for AOX formation. Therefore, one of the core mechanisms of controlling the denitrification process by optimizing process parameters such as C / N ratio, HRT, and temperature lies in altering the properties and content of these key fluorescent precursors, thereby achieving source control of AOX and the biotoxicity it drives.

[0054] The above conclusions can be used to explain why prolonged HRT at different temperatures leads to opposite trends in AOX and toxicity (e.g., decreased AOX and acute toxicity of luminescent bacteria in Example 2, and increased AOX and toxicity in Examples 3 and 4). Prolonging HRT at 30°C allows EfOM, as a nutrient (carbon source), to be further degraded and utilized by microorganisms, resulting in a decrease in the content of fluorescent components. Prolonging HRT at 20°C or 10°C intensifies endogenous respiration or causes cell lysis in microorganisms, releasing more new organic matter with fluorescent properties, leading to an increase in its content. This difference in the content of fluorescent components directly determines the level of AOX production and ultimately manifests as significantly different changes in biotoxicity.

[0055] Comparative Example 1 This comparative example aims to demonstrate, in comparison with the experimental group in Example 3, the crucial role of optimizing the C / N ratio to 6 in controlling the biotoxicity risk of chlorinated effluent.

[0056] Except for setting the denitrification C / N ratio to 3 and the HRT to 7h, the simulated wastewater composition (only the glucose dosage was adjusted to 42.2mg / L), denitrification inoculum sludge, and initial conditions were the same as in Example 3.

[0057] After denitrification, the steps and conditions for chlorination disinfection, DBPs and AOX detection, and acute toxicity testing of luminescent bacteria were the same as in Example 3.

[0058] The results are as follows Figure 7 As shown, the discussion focuses on the acute toxicity of AOX and luminescent bacteria. Simply reducing the C / N ratio from 6 to 3 increased the AOX generation potential by 51%, and more importantly, increased the acute toxicity of luminescent bacteria by 67%. This demonstrates that optimizing the C / N ratio to 6 has a significant effect on reducing the biotoxicity risk of chlorinated effluent.

[0059] Comparative Example 2 This comparative example aims to demonstrate, in comparison with the experimental group in Example 4, the crucial role of optimizing the C / N ratio to 6 in controlling the biotoxicity risk of chlorinated effluent.

[0060] Except for setting the denitrification C / N ratio to 3 and the HRT to 16h, the simulated wastewater composition (only the glucose dosage was adjusted to 42.2mg / L), denitrification inoculum sludge, and initial conditions were the same as in Example 4.

[0061] After denitrification, the steps and conditions for chlorination disinfection, DBPs and AOX detection, and acute toxicity testing of luminescent bacteria were the same as in Example 4.

[0062] The results are as follows Figure 8As shown, the discussion focuses on the acute toxicity of AOX and luminescent bacteria. Simply reducing the C / N ratio from 6 to 3 increased the AOX generation potential by 41% and the acute toxicity of luminescent bacteria by 68%. This demonstrates that optimizing the C / N ratio to 6 has a significant effect on reducing the biotoxicity risk of chlorinated effluent.

[0063] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process, characterized in that, The method is as follows: before chlorinating the wastewater for disinfection, the wastewater is first subjected to denitrification treatment. During the denitrification treatment, the carbon-nitrogen ratio of the denitrification process is controlled to be 3-6, and the hydraulic retention time is dynamically adjusted within the range of 7-24 hours according to the reaction temperature of the denitrification process, so as to reduce the disinfection by-products and biological toxicity after chlorination disinfection of wastewater.

2. The method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process according to claim 1, characterized in that, The carbon-to-nitrogen ratio of the denitrification process is controlled at 6.

3. The method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process according to claim 1, characterized in that, The method for controlling the carbon-to-nitrogen ratio in the denitrification process is as follows: glucose is added to the wastewater based on the initial nitrate nitrogen concentration to achieve carbon-to-nitrogen ratio control in the denitrification process.

4. The method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process according to claim 1, characterized in that, Under the conditions of reaction temperature of 10-30℃ and dissolved oxygen less than 0.5mg / L, sludge is inoculated into the wastewater for denitrification treatment. The denitrification treatment process ends when the nitrate nitrogen concentration in the wastewater drops to below 3mg / L or is completely degraded.

5. The method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process according to claim 1 or 4, characterized in that, When the denitrification reaction temperature is 30℃, the hydraulic retention time is controlled at 7h; when the denitrification reaction temperature is 20℃, the hydraulic retention time is controlled at 7h; when the denitrification reaction temperature is 10℃, the hydraulic retention time is controlled at 16h.

6. The method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process according to claim 4, characterized in that, The concentration of suspended solids in the mixed liquor of the sludge is 2000-4000 mg / L.

7. The method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process according to claim 1, characterized in that, The wastewater chlorination disinfection method is as follows: First, the pH of the effluent from the denitrification treatment wastewater is buffered to 7.0±0.

2. Then, sodium hypochlorite is added to the wastewater, and the mixture is reacted at 25°C in the dark for 7 days. After disinfection, a quenching agent is added to the wastewater to quench the residual chlorine.

8. The method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process according to claim 1, characterized in that, The disinfection byproducts include trihalomethanes, haloacetic acids, hydrated trichloroacetaldehyde, haloketones, haloacetonitrs, and halonitromethanes.

9. The method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process according to claim 8, characterized in that, The trihalomethanes include chloroform, dichlorobromodibromomethane, dichlorobromodibromomethane, and tribromomethane; The haloacetic acids include monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, dibromoacetic acid, tribromoacetic acid, monobromomonochloroacetic acid, monobromodichloroacetic acid, and dibromomonochloroacetic acid; The haloketones include 1,1-dichloropropanone and 1,1,1-trichloropropanone; The haloacetonitrs include monochloroacetonitrile, dichloroacetonitrile, trichloroacetonitrile, monobromoacetonitrile, dibromoacetonitrile, tribromoacetonitrile, monobromochloroacetonitrile, monobromodichloroacetonitrile, and dibromochloroacetonitrile; The halonitromethanes include monochloronitromethane, dichloronitromethane, trichloronitromethane, monobromonitromethane, dibromonitromethane, monobromo-monochloronitromethane, and monobromo-dichloronitromethane.

10. The application of the method for optimizing and controlling wastewater disinfection byproducts and biotoxicity based on denitrification process as described in any one of claims 1-9 in the harmless treatment of wastewater.

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