A method for degrading pharmaceutical pollutants in nitrated urine by using endogenous nitrate ultraviolet activation

Abstract

The application discloses a method for degrading drug pollutants in nitrated urine by utilizing endogenous nitrate ultraviolet activation, and relates to the technical field of sewage advanced treatment and resource utilization, and comprises the following steps: irradiating nitrated urine obtained through biological nitrification treatment by using an ultraviolet light source; generating active oxygen species and active nitrogen species in situ in the nitrated urine by ultraviolet photolysis of nitrate in the nitrated urine; and oxidatively degrading drug pollutants in the nitrated urine. The method relies on naturally existing nitrate in the nitrated urine as an oxidant precursor, generates active species in situ through 254nm ultraviolet light excitation, efficiently degrades drug pollutants of various structural types, does not need to additionally add an external oxidant, avoids loss of nutrient salts, reduces operation cost, and guarantees the safety and resource utilization value of urine-based fertilizer.

Description

Technical Field

[0001] This invention relates to the field of advanced wastewater treatment and resource utilization technology, specifically to a method for degrading pharmaceutical contaminants in nitrified urine using ultraviolet activation of endogenous nitrates. Background Technology

[0002] Urine accounts for less than 1% of the total volume of domestic sewage, yet it contributes approximately 88% of the nitrogen load, 57% of the phosphorus load, and 90% of the potassium load to urban wastewater treatment plants. Urine source separation (USS) technology collects and treats urine separately at the source, reducing the operational load on wastewater treatment plants and enabling efficient nutrient recovery, converting urine into liquid fertilizer for agricultural use. Compared to producing fertilizers from increasingly depleted natural resources, directly recovering nutrients from urine offers greater cost-effectiveness and sustainability.

[0003] Urine nitrification is one of the most mature and thoroughly validated urine stabilization and fertilizer preparation technologies. This process uses an aerobic biological process to partially oxidize the ammonium nitrogen produced by urea hydrolysis into nitrate nitrogen, significantly inhibiting ammonia volatilization and odor release during storage. The resulting nitrified urine is widely recognized as a high-quality liquid fertilizer. However, research shows that approximately 64% ± 27% of active pharmaceutical compounds are excreted in urine after being metabolized by the human body. Anaerobic storage and biological nitrification processes have limited capacity to remove pharmaceutical contaminants, leading to their continuous accumulation in nitrified urine, directly threatening the safe application of urine-based fertilizers. Farmer surveys indicate that about one-third of users are concerned about the environmental risks posed by residual pharmaceutical contaminants and pathogens in urine fertilizers. Therefore, efficient removal of pharmaceutical contaminants from nitrified urine is a core prerequisite for the large-scale promotion of urine source separation and resource utilization technology.

[0004] Current technologies for removing pharmaceutical contaminants from nitrified urine primarily rely on adsorption. For example, the biological nitrification-powdered activated carbon adsorption process can achieve a removal rate of over 90% for 12 target drugs. However, this technology has two inherent drawbacks: first, nutrients compete for adsorption, leading to a loss of approximately 21% of total nitrogen and 14% of phosphate, thus diminishing the fertilizer's value; second, the high cost of activated carbon regeneration limits the technology's large-scale application.

[0005] Advanced UV oxidation processes (UV-AOPs) have shown significant potential in the degradation of micropollutants. Conventional processes such as UV / hydrogen peroxide and UV / persulfate can efficiently degrade pharmaceutical pollutants by generating hydroxyl radicals and sulfate radicals. However, these processes require the addition of exogenous oxidants, which not only increases operating costs but also may affect the agricultural safety of urine fertilizers due to residual oxidants. Furthermore, due to the high-salt and complex matrix of nitrified urine, high concentrations of nitrates, ammonium ions, bicarbonates, and other components can affect the degradation effect through multiple mechanisms, including light shielding, competition among active species, and the generation of secondary free radicals.

[0006] Currently, there is a lack of systematic process research on nitrified urine systems. Insufficient understanding of the influence of the matrix, the contribution mechanism of bioactive species, the ecotoxicity of conversion products, and operational energy consumption severely restricts the engineering application of the technology. Therefore, providing a treatment technology that does not require external oxidants, is compatible with the complex matrix of nitrified urine, efficiently removes drug contaminants, and retains nutrients to the maximum extent is a pressing technical problem that needs to be solved in this field, and has significant practical implications for promoting the resource utilization of urine. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a method for degrading pharmaceutical contaminants in nitrified urine using endogenous nitrates activated by ultraviolet light. This method relies on naturally occurring nitrates in nitrified urine as oxidant precursors, generating active species in situ through 254nm ultraviolet light excitation, efficiently degrading pharmaceutical contaminants of various structural types. It eliminates the need for additional exogenous oxidants, avoids nutrient loss, reduces operating costs, and simultaneously ensures the safety and resource value of urine-based fertilizers.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for degrading drug contaminants in nitrated urine using ultraviolet light activation of endogenous nitrates, comprising the following steps:

[0010] Nitrified urine obtained through biological nitrification is irradiated with an ultraviolet light source. The ultraviolet light photolyzes the nitrates in the nitrified urine to generate reactive oxygen species and reactive nitrogen species in situ, thereby oxidatively degrading the drug contaminants in the nitrified urine.

[0011] In this invention, the endogenously present nitrates in nitrified urine can serve as precursors for natural photosensitizing oxidants: 254nm ultraviolet light photolysis of nitrates can generate reactive oxygen species (hydroxyl radicals (·OH), superoxide anions, triplet oxygen, etc.) and reactive nitrogen species (RNS, including nitric oxide radicals, nitrogen dioxide radicals, peroxynitrite, etc.) in situ, achieving the oxidative degradation of organic pollutants. This method requires no addition of exogenous oxidants such as hydrogen peroxide or persulfate throughout the entire process, relying entirely on the endogenous nitrates in nitrified urine as precursors for reactive species. The specific principle is as follows:

[0012] NO3 - +hv→NO2·+O· - ;

[0013] O· - +H₂O→·OH⁺OH - ;

[0014] NO3 - +H + +hv→ONOO - +H+ ↔ONOOH↔NO2·+·OH.

[0015] Preferably, the nitrified urine is a liquid product obtained by aerobic biological nitrification treatment of source-separated urine; wherein the concentration of ammonium nitrate is in the range of 0.01-0.25 mol / L.

[0016] Preferably, the nitrated urine also includes at least one of phosphate, sulfate, and bicarbonate.

[0017] Preferably, the bicarbonate ions naturally present in the nitrated urine can react with hydroxyl radicals to generate carbonate radicals (CO3·). - It has a enhancing effect on the degradation of pharmaceutical contaminants containing electron-rich structures (such as aniline groups and phenolic hydroxyl groups), without the need for prior removal of bicarbonate.

[0018] Preferably, the pH value of the nitrated urine is 7.0-9.0.

[0019] Preferably, the pH value is 7.0-7.5 to reduce the quenching effect of free ammonia on hydroxyl radicals under alkaline conditions and ensure degradation efficiency.

[0020] Preferably, the pH value is adjusted using a phosphate buffer system.

[0021] Preferably, the main emission wavelength of the ultraviolet light source is 254nm.

[0022] Preferably, the drug contaminant includes at least one of carbamazepine (CBZ), ibuprofen (IBU), trimethoprim (TMP), caffeine (CAF), and sulfamethoxazole (SMX).

[0023] Preferably, the concentration of the drug contaminant is 10 μmol / L.

[0024] Preferably, the irradiation time is 120-900s.

[0025] Preferably, the method is used as a deep processing unit, coupled after the urine biological nitrification process and before the fertilizer utilization process (such as distillation concentration and nutrient solidification), forming a complete process chain of source separation and collection - biological nitrification - ultraviolet deep treatment - fertilizer reuse.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) Utilization of endogenous matrix, low operating cost: The method of this invention relies entirely on the nitrates naturally present in nitrified urine as oxidant precursors, without the need to purchase or add any exogenous oxidants, which greatly reduces the cost of the agents; at the same time, no residual oxidants are introduced, which will not affect the agricultural safety of urine fertilizer;

[0028] (2) Excellent degradation efficiency and strong applicability to pollutants: The method of this invention can efficiently degrade drug pollutants with various chemical structures. For pollutants such as carbamazepine, trimethoprim, and caffeine that are difficult to remove by direct photolysis, the degradation rate is significantly improved. It can also treat a variety of drug pollutants with different structures and has a certain broad spectrum applicability.

[0029] (3) High nutrient retention and no loss of fertilizer value: The method of this invention has no significant impact on the degradation process of nutrient-related ions such as phosphate and sulfate (rate fluctuation <5%). The treatment process will not cause significant loss of core nutrients such as nitrogen, phosphorus and potassium, and retains the fertilizer value of nitrified urine to the greatest extent.

[0030] (4) Good matrix compatibility and low pretreatment requirements: The method of this invention clarifies the influence law of key water quality parameters of nitrified urine, and the degradation efficiency is optimal under neutral conditions; bicarbonate has no inhibitory effect on most drug pollutants and even has a strengthening effect; phosphate and sulfate have no interference, and no complicated pretreatment is required in practical applications, which is suitable for urine water quality with different degrees of nitrification.

[0031] (5) The process is simple and easy to couple, and has outstanding engineering potential: The core processing unit of the method of the present invention is only the ultraviolet reactor, which can be directly connected in series with the existing urine nitrification-distillation recovery process. It occupies a small area, is easy to operate and maintain, and is easy to promote and apply in decentralized urine treatment facilities. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings in this description are merely embodiments of the present invention.

[0033] Figure 1 The degradation kinetics curves of carbamazepine (CBZ), ibuprofen (IBU), trimethoprim (TMP), and caffeine (CAF) under different treatment conditions in Example 1 of the present invention are shown.

[0034] Figure 2 This is a graph showing the degradation kinetics of sulfamethoxazole (SMX) under different treatment conditions in Example 1 of the present invention.

[0035] Figure 3 This is a graph showing the effect of different nitrate concentrations on the apparent degradation rate constant of carbamazepine in Example 2 of the present invention.

[0036] Figure 4 This is a bar chart showing the degradation rate of drug contaminants under different pH conditions in Example 3 of the present invention.

[0037] Figure 5The graph shows the degradation rate of drug contaminants by different anions (phosphate, sulfate, and bicarbonate) in Example 4 of this invention, where (a) represents the control, phosphate, and sulfate; and (b) represents bicarbonate.

[0038] Figure 6 This is a schematic flowchart of the ultraviolet removal method for drug contaminants in nitrified urine according to Embodiment 5 of the present invention;

[0039] Figure 7 This is a graph showing the degradation kinetics of carbamazepine (CBZ), ibuprofen (IBU), trimethoprim (TMP), and caffeine (CAF) in nitrated urine in Example 5 of the present invention.

[0040] Figure 8 This is a degradation kinetic curve of sulfamethoxazole (SMX) in nitrified urine in Example 5 of the present invention. Detailed Implementation

[0041] Embodiments of the present invention are described below, examples of which are shown in the accompanying drawings. The embodiments described with reference to the drawings are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0042] In this embodiment of the invention, the ultraviolet light source is a 10W low-pressure mercury lamp (main wavelength 254nm), and the light intensity is measured to be 2.79 × 10⁻⁶ using a potassium ferric oxalate chemical probometer. -6 Einstein·L -1 ·s -1 The volume of a single batch reaction system is 50 mL, and a rotary photochemical reactor is used to ensure uniform light exposure.

[0043] Example 1

[0044] This invention provides a method for degrading drug contaminants in nitrated urine using ultraviolet activation with nitrates, specifically comprising the following steps:

[0045] Prepare synthetic nitrated urine containing 0.25 mol / L ammonium nitrate, and adjust the pH of the solution to 7.2 using a phosphate buffer system; add carbamazepine, ibuprofen, trimethoprim, caffeine and sulfamethoxazole to the synthetic nitrated urine respectively, so that the initial concentration of each target drug contaminant is 10 μmol / L;

[0046] The prepared solution was added to a quartz ultraviolet reactor and irradiated with an ultraviolet light source with a main emission wavelength of 254 nm under stirring conditions. During the ultraviolet irradiation, samples were taken at predetermined time intervals, and the concentrations of each drug contaminant were determined by high performance liquid chromatography or liquid chromatography-mass spectrometry. The treatments without irradiation and without the addition of ammonium nitrate served as control examples.

[0047] See results Figure 1 and2 As shown in the figure, all five drug contaminants can be degraded in the UV / nitrate system, and their apparent degradation rate order is: sulfamethoxazole > carbamazepine ≈ caffeine > ibuprofen > trimethoprim. Under dark reaction conditions, ammonium nitrate and the buffer system themselves cannot cause significant degradation of the target drug. Under UV irradiation conditions, hydroxyl radicals and reactive nitrogen species generated by nitrate photoactivation are the main causes of drug contaminant degradation.

[0048] Example 2

[0049] This invention provides a method for the ultraviolet activation and degradation of carbamazepine in nitrated urine using nitrates of different concentrations, specifically including the following steps:

[0050] Reaction solutions with ammonium nitrate concentrations of 0, 0.01, 0.05, 0.10, 0.20, and 0.25 mol / L were prepared. Carbamazepine was added to each solution to achieve an initial concentration of 10 μmol / L, and the pH was adjusted to 7.2 using a phosphate buffer system. Under the same experimental conditions, ultraviolet irradiation was performed, and the change in carbamazepine concentration over time was measured. The apparent degradation rate constant was calculated using the pseudo-first-order reaction kinetic equation.

[0051] ln(c t / c0)=-k obs ·t;

[0052] In the formula:

[0053] c0 is the initial concentration of carbamazepine;

[0054] c t The concentration of carbamazepine at irradiation time t;

[0055] k obs The apparent degradation rate constant;

[0056] See results Figure 3 As shown in the figure, the apparent degradation rate of carbamazepine significantly increased with the increase of ammonium nitrate concentration from 0 to 0.25 mol / L. This is because the number of ultraviolet photons absorbed per unit time increases with the increase of nitrate concentration, resulting in an increase in the generation of hydroxyl radicals and reactive nitrogen species. When the nitrate concentration reaches a high level, the increase in degradation rate gradually decreases, indicating that at high nitrate concentrations, there may be light shielding, self-reaction of reactive species, and competitive reactions of conversion products. Therefore, in practical engineering, the nitrate concentration and reactor size should be determined by combining the optical path length and ultraviolet absorption characteristics of nitrified urine.

[0057] Example 3

[0058] This invention provides a method for degrading drug contaminants in urine at different pH values ​​using ultraviolet nitrate activation, specifically including the following steps:

[0059] Prepare synthetic nitrated urine containing 0.25 mol / L ammonium nitrate, and adjust the pH of the reaction system to 7.2, 8.5 and 9.0 (5 for each) using a phosphate buffer system; add 5 target drug contaminants to each reaction system to an initial concentration of 10 μmol / L, and irradiate under the same ultraviolet conditions;

[0060] See results Figure 4 As shown in the figure, the apparent degradation rate of most target drug contaminants decreased as the pH increased from 7.2 to 8.5 and 9.0. This may be due to several factors: first, at higher pH conditions, the reaction between ammonia nitrogen and hydroxyl radicals is enhanced, consuming hydroxyl radicals available for degrading drug contaminants; second, pH changes alter the morphology and reactivity of reactive nitrogen species; and third, the dissociation state of drug contaminants changes with pH, ​​leading to variations in their reaction rate with reactive species. Therefore, when treating high-ammonia nitrogen nitrified urine, UV treatment under near-neutral conditions is preferred.

[0061] Example 4

[0062] This invention provides a method for the degradation of carbamazepine in nitrated urine containing different anions using ultraviolet nitrate activation, specifically including the following steps:

[0063] Five reaction solutions with an ammonium nitrate concentration of 0.25 mol / L were prepared. Carbamazepine was added to the reaction solutions to achieve an initial concentration of 10 μmol / L. The pH of the reaction system was adjusted using a phosphate buffer system. Phosphate, sulfate, and bicarbonate were added, with phosphate concentrations of 13.6 mmol / L and sulfate concentrations of 15 mmol / L, respectively, resulting in a pH of 7.2. Bicarbonate concentrations were added at concentrations of 1, 10, and 100 mmol / L, resulting in a pH of 8.5. All phosphate, sulfate, and bicarbonate were sodium salts of their respective compounds. The apparent degradation rate of carbamazepine was measured under the same UV irradiation conditions, with a control group not containing the relevant anions.

[0064] See results Figure 5 As can be seen from the figure, phosphates and sulfates have little effect on the degradation rate of carbamazepine, indicating that the present invention has good adaptability to common phosphates and sulfates in nitrified urine; bicarbonate can promote the degradation of carbamazepine, indicating that bicarbonate in the nitrified urine matrix promotes the removal of drug contaminants.

[0065] Example 5

[0066] like Figure 6 This invention provides a method for degrading drug contaminants in nitrified urine using ultraviolet activation of endogenous nitrates, specifically including the following steps:

[0067] Real nitrated urine (ammonia nitrogen 404 ppm, nitrate nitrogen 410 ppm, nitrite nitrogen 0.08 ppm, sulfate 216.3 ppm, phosphate 5 ppm) obtained by biological nitrification of source urine was collected and stored in a nitrated urine storage tank for later use. Five target drug contaminants were added to five groups of real nitrated urine to an initial concentration of 10 μmol / L, and the pH was adjusted to 7.2. The urine was then irradiated with a 254 nm ultraviolet light reactor. During the process, samples were taken at predetermined time intervals, and the concentrations of each drug contaminant were determined by high performance liquid chromatography or liquid chromatography-mass spectrometry. The samples were compared with synthetic nitrated urine with the same nitrate and ammonia nitrogen concentrations.

[0068] After the reaction is complete, the solution is placed in a processing liquid storage tank, and then concentrated to prepare fertilizer products.

[0069] The results can be found in the test results. Figure 7 and 8 As can be seen from the figure, drug contaminants in real nitrified urine still have a high degradation effect.

[0070] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for degrading drug contaminants in nitrated urine using ultraviolet activation of endogenous nitrates, characterized in that, The specific steps are as follows: Nitrified urine obtained through biological nitrification is irradiated with an ultraviolet light source. The ultraviolet light photolyzes the nitrates in the nitrified urine to generate reactive oxygen species and reactive nitrogen species in situ, thereby oxidatively degrading the drug contaminants in the nitrified urine.

2. The method for degrading drug contaminants in nitrated urine using ultraviolet activation with endogenous nitrates according to claim 1, characterized in that, The nitrified urine is a liquid product obtained by aerobic biological nitrification of source separated urine; wherein the concentration of ammonium nitrate ranges from 0.01 to 0.25 mol / L.

3. The method for degrading drug contaminants in nitrated urine using ultraviolet activation with endogenous nitrates according to claim 1, characterized in that, The nitrated urine also includes at least one of phosphate, sulfate, and bicarbonate.

4. The method for utilizing endogenous nitrates to activate and degrade drug contaminants in nitrified urine using ultraviolet light, as described in claim 1, is characterized in that... The pH value of the nitrated urine is 7.0-9.

0.

5. The method for degrading drug contaminants in nitrated urine using ultraviolet activation of endogenous nitrates according to claim 4, characterized in that, The pH value is adjusted using a phosphate buffer system.

6. The method for degrading drug contaminants in nitrated urine using ultraviolet activation with endogenous nitrates according to claim 1, characterized in that, The main emission wavelength of the ultraviolet light source is 254nm.

7. The method for utilizing endogenous nitrates to activate and degrade drug contaminants in nitrified urine using ultraviolet light according to claim 1, characterized in that, The drug contaminants include at least one of carbamazepine, ibuprofen, trimethoprim, caffeine, and sulfamethoxazole.

8. The method for utilizing endogenous nitrates to activate and degrade drug contaminants in nitrified urine using ultraviolet light according to claim 1, characterized in that, The concentration of the drug contaminant is 10 μmol / L.

9. The method for utilizing endogenous nitrates to activate and degrade drug contaminants in nitrified urine using ultraviolet light according to claim 1, characterized in that, The irradiation time is 120-900s.

10. The method for degrading drug contaminants in nitrated urine using ultraviolet activation of endogenous nitrates according to claim 1, characterized in that, The method is used as a deep processing unit, coupled after the urine bionitrification process and before the fertilizer utilization process.

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