A method for efficient short-range denitrification of sewage and coordinated high-quality carbon recovery

Abstract

The present invention discloses a method for efficient short-range denitrification of sewage and coordinated high-quality carbon recovery. The method uses Thauera-dominated short-range denitrification sludge to quickly capture volatile acid-type organic carbon in sewage, efficiently convert nitrate into nitrite, accumulate extracellular polysaccharides, intracellular polysaccharides and intracellular polyhydroxyalkanoates, and realize the recovery of high-quality carbon from biomass sources through intelligent sludge discharge based on pH and ORP inflection points. The method established by the present invention is aimed at low carbon-nitrogen ratio wastewater. Under the condition of 15-25°C, it can remove more than 90% of soluble volatile acids in sewage, achieve a nitrite accumulation rate of more than 70%, and recover high-quality carbon products accounting for 20-50% of the dry weight of biomass. It has the advantages of flexible operation, high efficiency and stability, energy saving and low consumption, and a wide range of applications.

Description

(I) Technical field

[0001] The invention relates to a method for efficient short-range denitrification of sewage and coordinated high-quality carbon recovery. (II) Background technology

[0002] Anaerobic ammonium oxidation is a new and economical and efficient technology in the field of biological denitrification. It has attracted widespread attention due to its outstanding advantages such as saving aeration energy consumption and reducing the amount of external carbon source added. However, the main bottleneck of anaerobic ammonium oxidation process in the field of mainstream urban sewage denitrification is the insufficient and unstable acquisition of substrate nitrite. The accumulation of nitrite in the short-term denitrification process provides a new idea for the acquisition of substrates for anaerobic ammonium oxidation. Controlling denitrification in the nitrite stage greatly shortens the carbon source demand and aeration energy consumption required for the sewage biological denitrification unit. In addition, short-term denitrifying bacteria can store soluble volatile acid-type organic matter to form intracellular polyhydroxyalkanoates, extracellular polysaccharides and other biomass-derived carbon. Polyhydroxyalkanoates are one of the raw materials for biodegradable plastics and have broad application prospects in biodegradable packaging materials and biomedicine. Polysaccharides / polysaccharides are a class of natural polymers that play a key role in biological metabolism. They have anti-inflammatory, antioxidant, anticoagulant, antiviral and other biological activity characteristics and are considered to be high-value resources in residual sludge. In recent years, achieving standard discharge of sewage treatment is no longer the only goal of sewage treatment plants. Recycling nutrients and energy while achieving high-quality reuse of water resources has gradually become the upgrading goal of sewage treatment plants for sustainable development. However, without affecting the accumulation rate of nitrite nitrogen, how to maximize the potential of short-term denitrification sludge to synthesize high-quality carbon and achieve its effective recovery is the difficulty in constructing a new resource recovery short-term denitrification process. (III) Summary of the invention

[0003] The purpose of the present invention is to provide a method for efficient short-range denitrification of sewage and coordinated high-quality carbon recovery. For low carbon-nitrogen ratio wastewater, under the condition of 15-25°C, more than 90% of the soluble volatile acids in the sewage can be removed, and a nitrite accumulation rate of more than 70% can be achieved. At the same time, high-quality carbon products accounting for 20-50% of the dry weight of biomass can be recovered. The method has the advantages of flexible operation, high efficiency and stability, energy saving and low consumption, and a wide range of applications.

[0004] The technical solution adopted by the present invention is:

[0005] The invention provides a method for high-efficiency short-range denitrification of sewage and coordinated high-quality carbon recovery. The method comprises the following steps: inoculating activated sludge in a sequencing batch reactor, taking low carbon-nitrogen ratio wastewater as influent, operating in a long-term anoxic circulation stirring mode under the condition of 15-25°C, wherein each cycle comprises influent, stirring, standing and draining, adjusting the single-day circulation stirring time according to the effluent nitrate nitrogen removal rate and nitrite nitrogen accumulation rate, gradually shortening the sludge age until the effluent nitrate nitrogen removal rate is more than 70% and the nitrite nitrogen accumulation rate is more than 70%; then gradually increasing the influent organic load and continuing to reduce the sludge age, operating until the effluent nitrate nitrogen removal rate is more than 90% and the nitrite nitrogen accumulation rate is more than 85%; and at a time point at which the angle between pH and ORP increases with time suddenly changes by more than 15 degrees, opening the reactor discharge valve, recovering the sludge rich in extracellular polysaccharides, intracellular polysaccharides and intracellular polyhydroxyalkanoates, and realizing high-efficiency short-range denitrification of sewage and coordinated high-quality carbon recovery.

[0006] Furthermore, the inoculation amount of activated sludge in the sequencing batch reactor is 2.0-4.0 gSS / L.

[0007] Furthermore, the concentration of volatile organic carbon in the low carbon-nitrogen ratio wastewater is 150-180 mgCOD / L, the concentration of nitrate nitrogen is 55-65 mgN / L, and the ratio of volatile acid organic carbon to nitrate nitrogen in the influent is 2.3-3.3:1 (COD / NO 3 - -N mass meter).

[0008] Furthermore, the long-term anoxic circulation stirring mode means that the reactor circulation stirring time is 3.5 to 11.5 hours, and the number of daily cycles is 2 to 6. Gradually shortening the sludge age means that the sludge age is 20 to 40 days by controlling the sludge discharge amount.

[0009] Furthermore, the stepwise increase of the influent organic load and the continued reduction of the sludge age refers to first increasing the reactor daily cycle number to 6 to 12 and shortening the sludge age to 2.5 to 5.0 days, so that the sludge concentration in the reactor is stably maintained at 0.2 to 0.4 gVSS / L, and the specific sludge organic load is in the range of 1.13 to 5.40 gCOD / gVSS / d.

[0010] The method for efficient short-range denitrification of sewage and coordinated high-quality carbon recovery of the present invention comprises the following steps:

[0011] The activated sludge was inoculated into a sequencing batch reactor with an inoculation amount of 2.0 g SS / L. Low carbon-nitrogen ratio wastewater was used as the influent, in which the concentration of volatile organic carbon was 150-180 mg COD / L, the concentration of nitrate nitrogen was 55-65 mg N / L, and the ratio of volatile acid organic carbon to nitrate nitrogen was 2.3-3.3:1 (COD / NO 3 --N mass meter);

[0012] At 15-25℃, the reactor was operated in a long-term anoxic circulation stirring mode. Each cycle included water inlet, stirring, standing and drainage. According to the nitrate nitrogen removal rate and nitrite nitrogen accumulation rate of the effluent, the reactor circulation stirring time was adjusted to 3.5h, the reactor daily cycle number was 6, and the sludge age was gradually shortened to 20 days. The reactor was operated until the nitrate nitrogen removal rate of the effluent reached more than 70% and the nitrite nitrogen accumulation rate reached more than 70%. The inlet carbon-nitrogen ratio was adjusted to 2.6:1, the reactor circulation stirring time was adjusted to 2.5h, and the daily cycle number was 8, and the sludge age was further shortened to 2.5-5 days. The sludge concentration in the reactor was stably maintained at 0.2gSS / L, and the specific sludge organic load was 3.10gCOD / gVSS / d. When the angle between pH and ORP (redox potential) increased with time suddenly changed by more than 15 degrees, the reactor sludge valve was opened to recover the sludge containing high-quality carbon, so as to achieve efficient short-range denitrification of sewage and coordinated recovery of high-quality carbon.

[0013] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: the method established by the present invention utilizes the short-term denitrification sludge dominated by Thauera to quickly capture volatile acid organic carbon in sewage, efficiently convert nitrate into nitrite, accumulate extracellular polysaccharides, intracellular polysaccharides and intracellular polyhydroxyalkanoates, and realize the recovery of high-quality carbon from biomass sources through intelligent sludge discharge based on pH and ORP inflection points. Under the condition of 15-25°C, the efficiency and stability of the short-term denitrification process in low carbon-nitrogen ratio sewage treatment can be maintained, more than 90% of soluble volatile acids in sewage can be removed, more than 70% of nitrite accumulation rate can be achieved, and high-quality carbon products accounting for 20-50% of the dry weight of biomass can be recovered. The high-quality carbon product is rich in extracellular polysaccharides, intracellular polysaccharides and intracellular polyhydroxyalkanoates, and the contents of the three are 34.0-113.0 mg / gVSS, 58.2-74.2 mg / gVSS, and 102.1-283.6 mg / gVSS, respectively. The method of the invention has the advantages of flexible operation, high efficiency and stability, energy saving and low consumption, wide application range, etc. (IV) Description of the drawings

[0014] Figure 1 , Example 1 Short-range denitrification performance and high-quality carbon content in residual sludge.

[0015] Figure 2 , Example 2 Short-range denitrification performance and high-quality carbon content in residual sludge.

[0016] Figure 3 , Example 3 Short-range denitrification performance and high-quality carbon content in residual sludge. (V) Specific implementation methods

[0017] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0018] The present invention inoculates activated sludge taken from the secondary sedimentation tank of a sewage treatment plant, and the inoculation amount of the activated sludge in the sequencing batch reactor is 2.0-4.0 gSS / L.

[0019] Example 1: A method for efficient short-range denitrification of wastewater and coordinated high-quality carbon recovery

[0020] The activated sludge was inoculated into a sequencing batch reactor (effective volume 5.3 L) with an inoculation amount of 2.0 g SS / L. Low carbon-nitrogen ratio wastewater was used as the influent, in which the concentration of volatile organic carbon was 150-180 mg COD / L, the concentration of nitrate nitrogen was 55-65 mg N / L, and the ratio of volatile acid organic carbon to nitrate nitrogen was 2.3-3.3:1 (COD / NO 3 - -N mass meter).

[0021] At 25℃, the reactor was operated in a long-term anoxic stirring mode. One cycle included water inlet, stirring, standing, and drainage. The reactor cycle stirring time was adjusted to 3.5h according to the nitrate nitrogen removal rate and nitrite nitrogen accumulation rate of the effluent, and the reactor daily cycle number was 6. The sludge age was gradually shortened to 20 days, and the nitrate nitrogen removal rate and nitrite nitrogen accumulation rate of the effluent were above 70%, and the nitrite nitrogen accumulation rate reached above 70%. The inlet carbon-nitrogen ratio was adjusted to 2.6, the reactor cycle stirring time was adjusted to 2.5h, and the daily cycle number was 8, and the sludge age was further shortened to 2.5 days. The sludge concentration in the reactor was stably maintained at 0.2gSS / L, and the specific sludge organic load was 3.10gCOD / gVSS / d. When the angle between pH and ORP (redox potential) increased with time suddenly changed by more than 15 degrees, the nitrate removal rate and nitrite accumulation rate were sampled and tested, the reactor sludge valve was opened, and the sludge containing high-quality carbon was recovered, so as to achieve efficient short-range denitrification of sewage and the recovery of high-quality carbon.

[0022] Results Figure 1 As shown in Figure 1, a shows that the nitrate (NaRE) removal rate reaches about 90%, the nitrite (NiAE) accumulation rate also reaches more than 85%, and more than 90% of the soluble volatile acids in the sewage are removed. b shows that the extracellular polysaccharides, intracellular polysaccharides (i.e., glycogen), and intracellular polyhydroxyalkanoates (PHA) in the residual sludge can be recovered at a maximum of 78.6 mg / gVSS, 68.5 mg / gVSS, and 262.3 mg / gVSS, respectively. The recovery of high-quality carbon in the residual sludge accounts for 41% of the dry weight of biomass.

[0023] Example 2: A method for efficient short-range denitrification of wastewater and high-quality carbon recovery

[0024] The sludge age of Example 1 was changed from 2.5 days to 5 days, and other operations were the same. The results are shown in Figure 2 .

[0025] a shows that the nitrate removal rate reaches about 90%, the nitrite accumulation rate is about 75%, and more than 90% of the soluble volatile acids in the sewage are removed.

[0026] b shows that the maximum contents of extracellular polysaccharide, intracellular polysaccharide and intracellular polyhydroxyalkanoate in the residual sludge can be recovered at 34.0 mg / g VSS, 58.2 mg / g VSS and 102.1 mg / g VSS respectively. The amount of high-quality carbon recovered from the residual sludge accounts for 20% of the dry weight of biomass.

[0027] Example 3: A method for efficient short-range denitrification of wastewater and high-quality carbon recovery

[0028] The 25°C in Example 1 was changed to 15°C, and other operations were the same. The results are shown in Figure 3 .

[0029] a shows that the nitrate removal rate reaches more than 90%, the nitrite accumulation rate reaches more than 80%, and more than 90% of the soluble volatile acids in the sewage are removed.

[0030] b shows that the maximum contents of extracellular polysaccharide, intracellular polysaccharide and intracellular polyhydroxyalkanoate in the residual sludge can be recovered at 113.0 mg / gVSS, 74.2 mg / gVSS and 283.6 mg / gVSS respectively. The amount of high-quality carbon recovered from the residual sludge accounts for 47% of the dry weight of biomass.

Claims

1. A method for efficient short-range denitrification of sewage and coordinated high-quality carbon recovery, characterized in that: The method comprises the following steps: inoculating activated sludge in a sequencing batch reactor, using low carbon-nitrogen ratio wastewater as influent, operating in a long-term anoxic circulation stirring mode at 15-25°C, adjusting the single-day circulation stirring time according to the effluent nitrate nitrogen removal rate and nitrite nitrogen accumulation rate, and gradually shortening the sludge age until the effluent nitrate nitrogen removal rate is more than 70% and the nitrite nitrogen accumulation rate is more than 70%; then gradually increasing the influent organic load and continuing to reduce the sludge age, operating until the effluent nitrate nitrogen removal rate is more than 90% and the nitrite nitrogen accumulation rate is more than 85%; when the angle between the pH and ORP rising with time suddenly changes by more than 15 degrees, opening the reactor discharge valve, recovering the sludge rich in extracellular polysaccharides, intracellular polysaccharides and intracellular polyhydroxyalkanoates, and realizing efficient short-range denitrification of sewage and coordinated high-quality carbon recovery.

2. The method according to claim 1, characterized in that The inoculation amount of the activated sludge in the sequencing batch reactor is 2.0-4.0 gSS / L.

3. The method according to claim 1, characterized in that The concentration of volatile organic carbon in the low carbon-nitrogen ratio wastewater is 150-180 mgCOD / L, the concentration of nitrate nitrogen is 55-65 mgN / L, and the influent COD / NO3 - The mass ratio of _N is 2.3~3.3:

1.

4. The method according to claim 1, characterized in that The long-term anoxic circulation stirring mode means that the reactor circulation stirring time is 3.5 to 11.5 hours, and the number of cycles per day is 2 to 6; gradually shortening the sludge age means that the sludge age is 20 to 40 days by controlling the sludge discharge volume.

5. The method according to claim 1, characterized in that The stepwise increase in the influent organic load and continued reduction in the sludge age refers to increasing the reactor daily cycle number to 6 to 12 and shortening the sludge age to 2.5 to 5.0 days, so that the sludge concentration in the reactor is stably maintained at 0.2 to 0.4 gVSS / L, and the specific sludge organic load is in the range of 1.13 to 5.40 gCOD / gVSS / d.

6. The method according to claim 1, characterized in that The method comprises the following steps: The activated sludge was inoculated into the sequencing batch reactor with an inoculation amount of 2.0 g SS / L. Low carbon-nitrogen ratio wastewater was used as the influent, in which the concentration of volatile organic carbon was 150-180 mg COD / L, the concentration of nitrate nitrogen was 55-65 mg N / L, and the COD / NO3 - The mass ratio of _N is 2.3-3.3:1; at 15-25℃, it is operated in a long-term anoxic circulation stirring mode. Each cycle includes water intake, stirring, standing, and drainage. According to the nitrate nitrogen removal rate and nitrite nitrogen accumulation rate of the effluent, the reactor circulation stirring time is adjusted to 3.5h, the number of reactor cycles per day is 6, and the sludge age is gradually shortened to 20 days. It is operated until the nitrate nitrogen removal rate of the effluent reaches more than 70% and the nitrite nitrogen accumulation rate reaches more than 70%; then the inlet COD / NO3 - The mass ratio of _N was 2.6:1, the reactor circulation stirring time was adjusted to 2.5h, the number of cycles per day was 8, the sludge age was further shortened to 2.5-5 days, the sludge concentration in the reactor was stably maintained at 0.2gSS / L, and the specific sludge organic load was at 3.10gCOD / gVSS / d; when the angle between the increase of pH and ORP over time suddenly changed by more than 15 degrees, the reactor discharge valve was opened to recover the sludge containing high-quality carbon, so as to realize the efficient short-range denitrification of sewage and the coordinated recovery of high-quality carbon.

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