Method for improving stability of anaerobic ammonia oxidation process in treating strong acidic wastewater

Abstract

The application discloses a method for improving the stability of an anaerobic ammonia oxidation process for treating strong acid wastewater, and belongs to the field of water treatment. The method comprises the following steps: (1) enhanced cultivation of anaerobic digestion sludge (ADS); (2) centrifugal filtration to obtain enhanced anaerobic digestion sludge internal EPS (ADS pH -EPS); and (3) addition of the ADS pH -EPS during treatment of strong acid wastewater by an anaerobic ammonia oxidation reactor. The method is suitable for various types of Aanmmox or coupled processes for denitrification treatment of strong acid wastewater, and has strong application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wastewater treatment, and particularly relates to a method for improving the stability of an anaerobic ammonia oxidation process in treating strong acidic wastewater. BACKGROUND

[0002] As a new type of efficient and energy-saving biological denitrification process, the anaerobic ammonia oxidation (Anammox) process technology is currently the fastest biological denitrification route, which does not require aeration and does not require additional carbon source, thus having significant economic advantages and being worthy of large-scale popularization and application. However, the biggest problem in applying the Anammox process is that the Anammox bacteria grow slowly and are sensitive to environmental changes such as pH. As one of the important environmental factors affecting bacterial growth and metabolism, the influent pH has an important influence on the denitrification performance and operation stability of the Anammox process. In recent years, with the substantial increase in the amount of wastewater discharged by the industries such as metallurgy and electroplating in some regions of China, the pH of the influent of some end-of-pipe wastewater treatment plants or the pH of the landfill leachate in some areas has decreased sharply, which brings great challenges to the stable operation of the Anammox process or its coupled process. However, so far, there is still a lack of effective methods for improving the treatment performance and operation stability of the Anammox process under the impact of strong acidic pH. As a cell communication mechanism commonly existing among Gram-negative bacteria, the quorum sensing (QS) mediated by acyl homoserine lactone (AHL) gradually reveals its regulation effect on the biological metabolic behavior of the Anammox mixed culture. However, the cost of purified exogenous AHLs is high, which makes it difficult to apply to the operation and regulation of actual projects. How to successfully develop AHLs substitutes and reduce the cost of AHLs regulation technology is an important direction worthy of exploration. The present application uses an intermittent low-pH shock strategy to strengthen the cultivation of anaerobic digestion sludge (ADS), and adds the extracellular polymeric substance (EPS) of the strengthened anaerobic digestion sludge (ADS pH -EPS) as an AHLs substitute to the Anammox system to improve the resistance of the Anammox process to strong acidic wastewater shock. The present application helps to improve the treatment performance and operation stability of the Anammox process under the impact of strong acidic wastewater, and is conducive to promoting the wide application of the Anammox process in the field of biological denitrification treatment of wastewater, and has important significance for reducing the cost of wastewater denitrification treatment. SUMMARY

[0003] Anammox bacteria are sensitive to environmental pH changes, and the discharge of strong acidic wastewater will cause serious deterioration of Anammox process treatment performance and operation stability, a method and strategy for improving the strong acid wastewater impact performance of Anammox process by using anaerobic digestion sludge EPS are provided. The main innovation lies in the use of intermittent pH shock strategy to strengthen the cultivation of anaerobic digestion sludge, which improves the content of AHLs in the EPS of anaerobic digestion sludge and its flocculation performance. Then, the EPS of anaerobic digestion sludge (ADS-EPS pH ) after the strengthened cultivation is added to the Anammox system, which improves the denitrification efficiency and long-term operation stability of the Anammox process in treating strong acidic wastewater. By using the present application, the denitrification efficiency of the Anammox process in treating strong acidic wastewater with pH 3.0-4.5 can be improved to 82%-93% during a running period of up to 160 days, and the treatment effect is at a stable level. The present application can significantly improve the treatment effect of the Anammox process on strong acidic wastewater without causing secondary pollution and with low cost, and is suitable for Anammox processes of different forms and sludge morphologies.

[0004] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme, and the specific implementation steps are as follows:

[0005] (1) Strengthened cultivation of anaerobic digestion sludge (ADS): the ADS seed sludge is taken from the primary sludge digestion tank of the sludge treatment unit of a sewage treatment plant; the seed sludge is inoculated into an anaerobic sequencing batch reactor (ASBR), and the suspended solid concentration in the reactor is maintained at 3.0-4.5 g VSS / L, and the reactor operating temperature is maintained at 31-37℃; an appropriate amount of ethanol (C2H6O) is added to the influent to maintain the influent chemical oxygen demand (COD) at 4000-4500 mg / L, and an appropriate amount of sodium hydrogen phosphate (Na2HPO4) and potassium bicarbonate (KHCO3) is added to maintain the influent alkalinity as CaCO3 at 1000 mg / L; the ratio of influent COD to phosphorus (P) (COD:P) is maintained at about 200:1; the reactor has a cycle period of 12 h, including 11 h of stirring reaction time (including 6 min of influent), 54 min of sedimentation, and 6 min of effluent, with 2 cycles per day; the ADS is strengthened by intermittent low pH shock: the strengthening cultivation period is 16 d, and the pH 5.5 shock is performed for one cycle duration at the 5th cycle period (3rd day), the 11th cycle period (6th day), the pH 5.0 shock is performed for one cycle duration at the 17th cycle period (9th day), the pH 4.0 shock is performed for one cycle duration at the 23rd cycle period (12th day), and the pH 3.0 shock is performed for one cycle duration at the 31st cycle period (16th day), and the strengthened anaerobic digestion sludge (ADS pH ) is obtained after the 16 d cultivation period.

[0006] (2) Strengthening anaerobic digestion sludge EPS (ADS pH -EPS) extraction:

[0007] Take the appropriate amount of ADS pH obtained in step (1) and use a homogenizer to form a homogenized mixture. Pour the mixture into a centrifuge tube, add 0.9% physiological saline, centrifuge at 7000 rpm for 20 min, filter through a 0.45 μm filter, and take the supernatant to obtain the loose binding type EPS (LB-EPS) extract of ADS pH , namely ADS pH -EPS.

[0008] (3) ADS pH -EPS addition during Anammox reactor treatment of strong acid wastewater:

[0009] An Anammox process was run using an upflow anaerobic sludge bed (UASB) reactor; the influent was artificially prepared water, and HCl solution was used to adjust the influent pH to 3.0-4.5, and the long-term experiment was conducted for 160 days; an appropriate amount of ADS-EPS pH was input to the bottom of the reactor every day through a chemical pump, the UASB reactor was operated at a temperature of 30-35°C, the hydraulic retention time (HRT) was controlled at 10-20 h, and internal reflux was set (the reflux ratio was 2.0).

[0010] The shock described in step (1) is to adjust the pH value in the anaerobic sequencing batch reactor (ASBR) reaction system to the corresponding shock pH value using acid, preferably hydrochloric acid, and after the shock, the water is discharged to continue the next cycle.

[0011] The influent in step (3) mainly contains ammonium chloride and sodium nitrite, which respectively provide 140-180 mg / L of ammonia nitrogen and 160-237 mg / L of nitrite nitrogen; further containing KH2PO4 (21 mg / L), MgSO4·7H2O

[0012] (130 mg / L), CaCl2·2H2O (69 mg / L), and NaHCO3 (0.91 g / L).

[0013] The ADS pH -EPS described in the present application is a loose binding type EPS (LB-EPS) in anaerobic digestion sludge that is intermittently and low-pH shocked and strengthened; the specific strengthening culture process is shown in step (1);

[0014] The anaerobic digestion sludge is taken from a primary sludge digestion tank of a sludge treatment unit of a sewage treatment plant;

[0015] The ADSpH EPS is added to the reactor daily at a rate of 0.5 mg / L to 1.5 mg / L ADS during reactor operation. pH -EPS, until the run ends;

[0016] The reactor influent has an acidic pH of 3.0–4.5;

[0017] The inoculated sludge for the Aanmmox reactor can be Aanmmox flocculent sludge, granular sludge, biofilm, or sludge-film mixture (the relative abundance of Aanmmox bacteria should be higher than 5%).

[0018] The working principle of this invention: Anaerobic digested sludge (ADS) secretes a higher concentration of AHLs compared to other sludge types (such as aerobic activated sludge, denitrification sludge, and Aanmmox sludge), and the proportion of AHLs secreted by ADS in LB-EPS is as high as 92%. Furthermore, LB-EPS (ADS secreted by ADS after intermittent low-pH shock intensive culture) pH -EPS) AHLs signal content within the ADS has been further significantly improved, ADS pH - EPS itself exhibits significantly improved flocculation efficiency, and the low pH shock also enhances the stability of AHL signals secreted by ADS under strongly acidic conditions. Adding ADS pH -EPS to the Aanmmox system allows the system to maintain high and stable nitrogen removal efficiency even at strongly acidic pH levels of 3.0–4.5. This is because ADS pH -Multiple types and high concentrations of AHLs signaling within EPS effectively stimulated the aggregation behavior, active expression, and electron transport performance of Anammox organisms under strongly acidic conditions; in addition, some AHLs signaling could also inhibit the excessive proliferation of acidophilic bacteria in Anammox mixed cultures, preventing the inhibition of Anammox by acidophilic bacteria. ADS... pH EPS can also be used as a bioflocculant to further enhance the settling performance of Aanmmox bioaggregates and improve the retention capacity of effective biomass under the impact of highly acidic wastewater.

[0019] Compared with the prior art, the present invention has the following advantages and effects:

[0020] (1) It can significantly improve the denitrification efficiency and operational stability of Aanmmox or related processes for strongly acidic wastewater.

[0021] (2) Anaerobic digestion sludge comes from the sludge treatment system of the sewage treatment plant, which reduces the burden of sludge treatment and disposal in the sewage treatment plant and provides a way for the resource utilization of the remaining sludge.

[0022] (3) It is applicable to various types of Aanmmox or its coupled processes for denitrification treatment of strongly acidic wastewater, and has strong applicability.

[0023] (4) The operation and implementation process is simple and easy to implement. Attached Figure Description

[0024] Figure 1 Add ADS to Example 1 pH - Changes in total nitrogen removal rate and biomass-to-Aanmmox activity in different Aanmmox systems (flocculent sludge, granular sludge, and biofilm) after EPS; (A) is total nitrogen removal rate, (B) is biomass, and (C) is specific Aanmmox activity.

[0025] Figure 2 Add ADS to Example 2 pH - Changes in total nitrogen removal rate, sludge-to-Aanmmox activity, and sludge settling performance of the Aanmmox system after EPS under influent pH conditions of 3.0, 3.5, 4.0, and 4.5; (A) is total nitrogen removal rate, (B) sludge-to-Aanmmox activity, and (C) sludge settling velocity.

[0026] Figure 3 ADS at different concentrations pH - The effect of EPS on the total nitrogen removal rate of strongly acidic wastewater treated by the Anmmox process with different reactor types. Detailed Implementation

[0027] Maintaining high denitrification efficiency and operational stability of the Anammox process for strongly acidic wastewater is challenging, and effective improvement strategies are currently lacking. This invention employs an intermittent low-pH shock strategy to stimulate anaerobic digestion sludge to secrete multiple types of high-concentration AHLs signals that maintain high stability under strongly acidic conditions. These high-concentration AHLs signals enhance the flocculation performance and activity of Anammox co-cultures under strongly acidic conditions, thereby improving the denitrification efficiency and operational stability of the Anammox process for treating strongly acidic wastewater.

[0028] The following provides specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention. The present invention will be further described in detail below with reference to the embodiments.

[0029] Example 1: Adding ADS pH - The impact of EPS on total nitrogen removal rate, biomass, and specific Aanmmox activity in different Aanmmox systems (flocculated sludge, granular sludge, and biofilm).

[0030] Six UASB reactors (effective volume 10 L each) were set up and inoculated with Anammox flocculent sludge (R1 and R2), Anammox granular sludge (R3 and R4), and Anammox biofilm (R5 and R6), respectively, for continuous flow experiments with an influent pH of 4.5. The initial biomass concentration was the same for all reactors. Reactors R2, R4, and R6 did not contain ADS. pH -EPS; ADS added to reactors R1, R3 and R5 pH -EPS, add 1.0 mg / L of ADS to reactors R1, R3 and R5 daily via a reagent pump. pH -EPS, ADS pH - The source of EPS is detailed in the specific implementation steps (1) and (2) of the invention. The influent is artificially prepared, and the water quality is as follows (g / L): ammonia nitrogen (NH4+) + The concentration of nitrite nitrogen (NO2) was 160 mg / L (provided via ammonium chloride), and the concentration of nitrite nitrogen (NO2) was... - The nitrogen (N) concentration was 192 mg / L (provided via sodium nitrite); it also contained KH₂PO₄ (21 mg / L), MgSO₄·7H₂O (130 mg / L), CaCl₂·2H₂O (69 mg / L), and NaHCO₃ (0.91 g / L). Nitrogen gas was used to flush out dissolved oxygen from the influent. The reactor operating temperature was set to approximately 33°C, the HRT was set to 10 h, and the internal reflux ratio was set to 2.0. The differences in denitrification efficiency and sludge characteristics among the reactor groups after 160 days were compared to evaluate the Adaptive Discharge System (ADS). pH -The effect of EPS on improving the performance of different forms of Anammox mixed cultures in treating highly acidic wastewater.

[0031] Example 2: Adding ADS at different influent pH levels (3.0, 3.5, 4.0, and 4.5) pH -The impact of EPS on the nitrogen removal performance and sludge characteristics of the Anammox system

[0032] Eight UASB reactors (effective volume same as in Example 1) were set up, with influent pH values ​​of 3.0 (T1 and T2), 3.5 (T3 and T4), 4.0 (T5 and T6), and 4.5 (T7 and T8), respectively, for continuous flow experiments. No ADS was added to reactors T2, T4, T6, and T8. pH -EPS; 1.0 mg / L of ADS is added daily to reactors T1, T3, T5, and T7 via a reagent pump. pH -EPS, ADS pH - The source of EPS is detailed in the specific implementation steps (1) and (2) of the invention description. The influent water quality, reactor operating temperature and time, HRT, and internal reflux ratio are set as in Example 1. The ADS is evaluated under different influent acidity pH levels. pH- The impact of EPS on the denitrification performance of the Anammox process.

[0033] Example 3: ADS with different concentrations pH - The impact of EPS on the total nitrogen removal performance of Aanmmox systems with different reactor types in treating strongly acidic wastewater.

[0034] Four UASB reactors (U1, U2, U3, U4, and U5) and four sequencing batch reactors (S1, S2, S3, S4, and S5) were set up. The effective volume of each reactor was the same as in Example 1, and the influent pH was set to 3.5. Reactors U1 and S1 did not contain ADS. pH -EPS, U2 and S2 added at 0.1 mg / LADS pH -EPS, U3 and S3 added with 0.5 mg / L ADS pH -EPS, U4 and S4 added 1.5mg / LADS pH -EPS, U5 and S5 added with 2.0 mg / L ADS pH -EPS. ADS pH - The source of EPS is detailed in the specific implementation steps (1) and (2) of the invention description. The influent water quality, UASB and SBR reactor operating temperatures, and HRT settings are the same as in Example 1; in this example, the reactors are not equipped with a reflux system. Each cycle of the SBR reactor is 11 hours, including 10 hours of stirring reaction time (including 20 minutes of influent), 45 minutes of settling, and 15 minutes of effluent discharge. The experiment lasted for 160 days, and the total nitrogen removal performance of each group of reactors was evaluated at the end of the experiment.

[0035] Testing and analysis methods:

[0036] Ammonia nitrogen was determined using Nessler's reagent spectrophotometry, nitrite nitrogen using N-(1-naphthyl)-ethylenediamine spectrophotometry, nitrate nitrogen using thymol spectrophotometry, and total nitrogen using a total nitrogen analyzer (Shimadzu, Japan). DO, pH, and temperature were measured using a WTW / Multi3420 analyzer. Sludge particle strength was determined using a particle strength meter. 15 In N stable isotope tracing experiments 29 The rate of N2 production is used to characterize the specific Anammox activity of biomass. The method for determining the settling velocity of sludge particles involves allowing sludge particles to pass freely through a water column of 1 m in height and measuring their velocity.

[0037] Results and Analysis:

[0038] 1. Example 1:

[0039] As attached Figure 1 As shown in A, add ADS pH- The total nitrogen removal rates of the EPS reactors R1 (flocs), R2 (granules), and R3 (biofilm) reached 82%, 91%, and 93%, respectively, significantly higher than those without ADS. pH - EPS reactors R2 (flocs, 33%), R4 (granules, 36%), and R6 (biofilm, 37%). These results illustrate the effects of adding ADS. pH EPS can significantly improve the nitrogen removal performance of Anammox processes (in various forms such as flocs, granules, or biofilms) for treating strongly acidic wastewater. Meanwhile, the biomass and specific Anammox activity analysis results in each reactor group are attached. Figure 1 B and C) indicate that the biomass concentrations retained in reactors R1, R2, and R3 were 3.4, 5.1, and 5.8 g / L, respectively, while those retained in reactors R2, R4, and R6 were only 1.0, 1.7, and 2.0 g / L. The bio-specific Anammox activities in reactors R1, R2, and R3 were as high as 3.4, 5.1, and 5.8 μmol / gVSS·h, respectively, while those in reactors R2, R4, and R6 were only 1.0, 0.96, and 0.98 μmol / gVSS·h. pH The addition of EPS can significantly increase the biomass concentration and specific Anammox activity in Anammox flocculent, granular, or biofilm processes, which is due to the addition of ADS. pH -EPS is a key reason why the Anammox process significantly improves the denitrification performance of highly acidic wastewater with different sludge types.

[0040] 2. Example 2

[0041] The influent pH for reactors T1 and T2 is 3.0, for T3 and T4 it is 3.5, for T5 and T6 it is 4.0, and for T7 and T8 it is 4.5. (See attached diagram) Figure 2 As shown in A, add ADS pH - The total nitrogen removal rates of the EPS reactors T1, T3, T5, and T7 reached 71%, 81%, 87%, and 91%, respectively, significantly higher than those without ADS. pH - EPS reactors T2, T4, T6, and T8 (24%, 29%, 32%, and 36%). These experimental results illustrate the effects of adding ADS. pH EPS can significantly improve the denitrification performance of the Anammox process for strongly acidic wastewater with a pH of 3.0–4.5. Analysis results of sludge-to-Anammox activity and settling performance in each reactor group are attached. Figure 1B and C) indicate that the specific Anammox activity of the sludge in reactors T1, T3, T5, and T7 was as high as 2.11, 2.89, 3.24, and 3.68 μmol / gVSS·h, respectively, significantly higher than that in reactors T2, T4, T6, and T8 (0.58, 0.72, 0.88, and 0.96 μmol / gVSS·h). Furthermore, the settling velocities of the sludge in reactors T1, T3, T5, and T7 were as high as 44, 51, 57, and 62 m / h, respectively, while the settling velocities in reactors T2, T4, T6, and T8 were only 23, 27, 29, and 33 m / h. This demonstrates that ADS... pH The addition of EPS significantly improved the specific Anammox activity and settling velocity of Anammox sludge particles in highly acidic wastewater environments ranging from 3.0 to 4.5. Therefore, the addition of ADS... pH EPS can significantly improve the denitrification performance of the Anammox process in treating highly acidic wastewater with different pH values.

[0042] 3. Example 3

[0043] As attached Figure 3 As shown, compared to not adding ADS pH - The total nitrogen removal rates of the EPS's UASB reactor (U1) and SBR reactor (S1) were only 29% and 23%, respectively, after the addition of 0.5 mg / L ADS. pH - The total nitrogen removal rates in reactors U3 and S3 of the EPS system were increased to 90% and 86%, respectively, with the addition of 1.5 mg / L ADS. pH -The total nitrogen removal rates in reactors U4 and S4 of the EPS system were also improved to 93% and 90%, respectively. However, the addition of 0.1 mg / L ADS... pH The total nitrogen removal rates in reactors U3 and S3 of EPS showed little change compared to reactors U1 and S1; 2.0 mg / LADS was added. pH -The total nitrogen removal rates of reactors U4 and S4 in EPS were also lower compared to U3 and S3, and U4 and S4. Based on the above experimental results, ADS pH The optimal concentration of EPS for addition is 0.5–1.5 mg / L, and ADS should be added at this concentration. pH EPS can effectively improve the denitrification performance and operational stability of different types of Anammox reactors, such as UASB or SBR, for strongly acidic wastewater.

Claims

1. A method for improving the stability of anaerobic ammonia oxidation process for treating strongly acidic wastewater, characterized in that, Includes the following steps: (1) Enhanced cultivation of anaerobic digestion sludge: The seed sludge for anaerobic digestion was taken from the primary sludge digestion tank of the sludge treatment unit of the sewage treatment plant; the seed sludge was inoculated into the anaerobic sequencing batch reactor to maintain the suspended solids concentration in it at 3.0~4.5 gVSS / L, and the reactor operating temperature was maintained at 31~37℃; an appropriate amount of ethanol was added to the reactor influent to maintain the influent chemical oxygen demand at 4000~4500 mg / L, and an appropriate amount of sodium hydrogen phosphate and potassium bicarbonate were added to maintain the influent alkalinity (calculated as CaCO3) at 1000 mg / L; the ratio of influent COD to phosphorus was maintained at 200:1; each cycle of the reactor was 12 h, including 11 h of stirring reaction time, 54 min of settling, and 6 min of drainage, of which the 11 h of stirring reaction time included 6 min of influent, and there were 2 cycles per day; the anaerobic digestion sludge was enhanced by intermittent low pH shock method: the enhanced cultivation period was 16 The sludge was subjected to a pH shock of 5.5 for one cycle at the 3rd day of the 5th cycle and the 6th day of the 11th cycle; a pH shock of 5.0 for one cycle at the 9th day of the 17th cycle; a pH shock of 4.0 for one cycle at the 12th day of the 23rd cycle; and a pH shock of 3.0 for one cycle at the 16th day of the 31st cycle. After the 16-day incubation period, enhanced anaerobic digestion sludge was obtained. (2) Extraction of EPS from enhanced anaerobic digestion sludge: Take an appropriate amount of enhanced anaerobic digestion sludge obtained in step (1) and use a homogenizer to form a homogenized mixture; pour the mixture into a centrifuge tube, add 0.9% physiological saline, centrifuge at 7000 rpm for 20 min, filter through a 0.45 μm filter membrane and take the supernatant to obtain the loosely bound EPS extract of enhanced anaerobic digestion sludge; (3) Addition of EPS during the treatment of strongly acidic wastewater in the Anammox reactor: The Anammox process was operated using an upflow anaerobic sludge bed reactor. The influent was artificially prepared, and the pH of the influent was adjusted to acidic using HCl solution. The long-term experiment lasted for 160 days. Every day, an appropriate amount of EPS described in step (2) was pumped into the bottom of the reactor. The operating temperature of the upflow anaerobic sludge bed reactor was controlled at 30~35 ℃, the hydraulic retention time was controlled at 10~20 h, and internal reflux was set with a reflux ratio of 2.

0. Step (1) The influent mainly contains ammonium chloride and sodium nitrite, providing 140~180 mg / L ammonia nitrogen and 160~237 mg / L nitrite nitrogen respectively; it also contains 21 mg / L KH2PO4, 130 mg / L MgSO4·7H2O, 69 mg / L CaCl2·2H2O and 0.91 g / L NaHCO3; In step (3), the EPS mentioned in step (2) is added to the reactor daily at a rate of 0.5 mg / L to 1.5 mg / L until the operation ends.

2. The method for improving the stability of anaerobic ammonia oxidation process for treating strongly acidic wastewater according to claim 1, characterized in that, The shock described in step (1) is to use hydrochloric acid to adjust the pH value in the anaerobic sequencing batch reactor reaction system to the corresponding shock pH value, and then drain the water to continue to the next cycle.

3. A method for improving the stability of anaerobic ammonia oxidation process for treating strongly acidic wastewater according to claim 1, characterized in that, Step (3) The acidic pH of the reactor influent is 3.0~4.

5.

4. A method for improving the stability of anaerobic ammonia oxidation process for treating strongly acidic wastewater according to claim 1, characterized in that, The Anammox reactor inoculation sludge in step (3) is Anammox flocculent sludge, granular sludge, biofilm, or sludge-film mixture, with a relative abundance of Anammox bacteria higher than 5%.

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