A rapid recovery method for inhibiting nitrification activity in a town sewage treatment plant with AAO process after being impacted by toxic wastewater

Abstract

A method for rapid recovery after toxic wastewater impacts an AAO process urban sewage treatment plant to inhibit nitrification activity, belonging to the technical field of urban sewage treatment. When an urban sewage treatment plant is impacted by toxic wastewater during operation, the biochemical system will be damaged or collapsed. Among them, the main functional bacteria in the aerobic biochemical pool are nitrifying bacteria, most of which are autotrophic bacteria, which are more susceptible to the impact load, and the recovery of the activity of nitrifying bacteria is also more difficult. The present invention can quickly and effectively restore the activity of the aerobic biochemical pool, and through the zoning control strategy and chemical agent coordinated treatment during the debugging process, the effluent can still meet the discharge standards. The treatment method is simply described as: incoming water quality analysis (step 1), biochemical reaction pool zoning control (step 2), chemical agent emergency control of effluent to meet the standards (step 3). This method was applied to a sewage treatment plant in the Northeast region where the aerobic biochemical pool failed, and normal operation was restored in a short time, and the effluent during the debugging process could still meet the discharge standards.

Description

Technical Field

[0001] The invention belongs to the technical field of urban sewage treatment, and in particular relates to a method for quickly recovering nitrification activity of an urban sewage treatment plant subjected to an AAO process impact by toxic wastewater. Background Art

[0002] AAO (anaerobic-anoxic-aerobic) activated sludge process is widely used in urban sewage treatment plants in my country. Usually 2 or 4 groups of AAO units are used to facilitate single tank maintenance or optimization regulation. Under the designed influent water quality, the design parameters of "Outdoor Drainage Design Code GB50014-2006" are followed, and the effluent ammonia nitrogen can meet the effluent requirements of Level B in "Urban Sewage Discharge Standard GB18918-2002".

[0003] During the operation of urban sewage treatment plants, the impact of toxic wastewater will cause damage or collapse of the biochemical system. The main functional bacteria in the aerobic biochemical pool are nitrifying bacteria, which are mostly autotrophic bacteria and are more susceptible to shock loads. At the same time, it is more difficult to restore the activity of nitrifying bacteria. At present, after the performance of the aerobic pool of the sewage treatment plant decreases, there is no effective method to achieve the rapid recovery of the activity of the aerobic zone. At the same time, due to the continuous flow characteristics of the AAO process, the sludge return cannot be separated, and the influent is not easy to separate. It cannot be debugged in a single group like the CASS process. There is no effective way to simultaneously achieve the regulation of aerobic pool activity and effluent discharge standards. Conventional treatment methods such as aerobic zone suffocation and exogenous sludge addition have long recovery time and effluent does not meet the standards during the regulation period. There is an urgent need to develop a method that can quickly restore the nitrification activity of the aerobic pool of the sewage treatment plant and achieve effluent standards simultaneously. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of long activity recovery time of aerobic pools and substandard effluent during the recovery period, and to provide a method for quickly recovering nitrification activity after toxic wastewater impacts an AAO process urban sewage treatment plant.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for quickly recovering nitrification activity after toxic wastewater impacts an AAO process urban sewage treatment plant, the method comprising:

[0007] Step 1: Incoming water quality analysis: Detect the COD, ammonia nitrogen, total nitrogen, total phosphorus indicators, pH, ORP, and heavy metal content of the incoming water to determine whether the incoming water quality is still toxic. Only after the incoming water is non-toxic can the zoning regulation begin; the simple method is to take the activated sludge from the aerobic pool of a normally operating urban sewage plant to treat the influent of the accident sewage plant. If the ammonia nitrogen removal rate is greater than 80% within 12 hours, it is determined that the influent of the accident sewage plant is no longer toxic and can be treated with this method; if the ammonia nitrogen removal rate is less than 80%, it indicates that the incoming water continues to be toxic and needs to be reported immediately to take corresponding emergency treatment measures. This method is not suitable for the regulation of accident sewage plants where the incoming water is still toxic;

[0008] Step 2: Zoning and regulation of the biochemical reaction pool: Divide the biochemical reaction pool into a regulation group and a non-regulation group. First, stop the water inlet and aeration of the regulation group, close the external sludge return and sedimentation of the regulation group, and discharge part of the sludge from the regulation group to reduce the liquid level of the biochemical pool of the regulation group to 1 / 4 to 1 / 3 of the original pool capacity; start short-term aeration of the regulation group, and when the sludge concentration of the regulation group is lower than 1000 mg / L, add sludge until the sludge concentration is higher than 3500 mg / L; intermittent water inlet and then aeration of the regulation group, each water inlet is 1 / 4 to 1 / 3 of the original pool capacity. 1 / 3, high-quality carbon source needs to be added to make the influent COD 200-300 mg / L, at this time the control group operation mode is batch mode; after each intermittent water inflow to the control group, the ammonia nitrogen concentration of the biochemical pool is detected along the way, and when the ammonia nitrogen concentration of the control group drops below 1 mg / L, water is intermittently inflowed again, and repeated several times, the control group is fully loaded; after the last water inflow, the control group is close to full pool, the sludge concentration returns to normal level and the nitrification activity is good, at this time the daily processing capacity of the control group is close to the full load state of the control group;

[0009] During the debugging process of the entire control group, the sludge external reflow of the non-control group was closed, the sludge discharge of the non-control group was increased, and the sludge without nitrification activity was discharged to reduce the sludge concentration of the non-control group to below 3000mg / L; in the last cycle of intermittent water inflow of the control group, exogenous sludge was added to the non-control group, and the sludge concentration of the non-control group was increased to above 6000mg / L, and the batch operation was carried out; before the last cycle of batch water inflow of the control group, the water volume treated by the non-control group was the difference between the total water volume and the daily water inflow of the control group. The treated water volume is greater than its designed water volume, and its treatment target is to meet the COD standard; in the last cycle of the sequential batch water inflow of the control group, the treated water volume of the non-control group is 100% of the designed water volume, and its treatment target is to meet the COD and ammonia nitrogen standards; after the last sequential batch water inflow of the control group is completed and the full load state is restored, the non-control group also reaches its full load state, and the sludge external reflow is turned on. The operation mode of the control group and the non-control group is changed to continuous flow, and then the control group and the non-control group work together to achieve continuous full-load treatment;

[0010] Step 3: In the above zoning control process, if there is a problem of excessive total phosphorus and ammonia nitrogen in the effluent, the effluent is treated with breakpoint chlorination to remove ammonia nitrogen, and total phosphorus is removed by adding phosphorus removal agents.

[0011] Furthermore, in step 1, the judgment method is specifically to mix the activated sludge with the influent, and the treatment conditions are: continuous aeration is required to maintain a dissolved oxygen concentration of 2 to 5 mg / L, the mixing ratio should be close to the sludge-wastewater ratio of a normal sewage plant biochemical pool, that is, 2:3 to 8, the temperature is room temperature, and the effluent ammonia nitrogen is detected.

[0012] Furthermore, in step 2, for the biochemical reaction pools with 4 or more groups operating together, half of the groups are selected as control groups, and the remaining groups are debugged as non-control groups, and the debugging method is the same as step 2.

[0013] Furthermore, in step 2, the high-quality carbon source is methanol, sodium acetate or glucose, and fuel by-products should be avoided because such carbon sources contain high ammonia nitrogen and are not suitable for such application scenarios.

[0014] Furthermore, in step 2, after the commissioning group starts to continuously flow water, nitrifying bacteria are added to enhance the nitrification activity of the aerobic pool, which is helpful for activity recovery and long-term operation. The amount of bacteria added is 100-400g / m 3 .

[0015] Furthermore, in step 2, the exogenous sludge comes from dewatered sludge (water content 80%) from other urban sewage treatment plants.

[0016] Furthermore, in step 3, the agent of the breakpoint chlorination method is chlorine gas or sodium hypochlorite; the phosphorus removal agent is one of aluminum sulfate, aluminum chloride, polyaluminum chloride, ferrous sulfate, polyferric chloride sulfate, ferric chloride, polyferric chloride or calcium hydroxide, and organic phosphorus removal agents cannot be added.

[0017] The beneficial effects of the present invention compared with the prior art are as follows: the sewage treatment technology targets the failed biochemical pools in sewage treatment plants, and is mainly a technology for rapidly restoring the nitrification activity of aerobic pools. Specifically, a strategy for zoning regulation of aerobic biochemical pools and coordinated treatment with chemical agents is constructed, which can achieve rapid recovery of nitrification activity in aerobic pools and compliance of effluent from sewage treatment plants during the regulation period. The invention can provide an effective new technology for restoring nitrification activity in aerobic pools for the operation of sewage treatment plants impacted by toxic wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a specific debugging flow chart of step 2 of the present invention.

[0019] Figure 2 This is a schematic diagram of emergency agent addition.

[0020] Figure 3 This is the ammonia nitrogen concentration diagram of group A.

[0021] Figure 4 This is the ammonia nitrogen concentration diagram of Group B after startup. DETAILED DESCRIPTION

[0022] The technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the protection scope of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0023] Embodiment 1:

[0024] A method for quickly recovering nitrification activity after toxic wastewater impacts an AAO process urban sewage treatment plant, the method comprising:

[0025] Step 1: Incoming water quality analysis: Detect the COD, ammonia nitrogen, total nitrogen, total phosphorus indicators, pH, ORP, and heavy metal content of the incoming water to determine whether the incoming water quality is still toxic. Only after the incoming water is non-toxic can the zoning regulation begin; the simple method is to take the activated sludge from the aerobic pool of the normal operating urban sewage plant to treat the influent of the accident sewage plant. The treatment conditions are: continuous aeration is required to maintain the dissolved oxygen concentration of 4-5 mg / L, the mixing ratio should be close to the sludge sewage ratio of the biochemical pool of the normal sewage plant, that is, 2:3-5, and the temperature is room temperature. If the ammonia nitrogen removal rate is greater than 80% within 12 hours, it is determined that the influent of the accident sewage plant is no longer toxic and can be treated with this method; if the ammonia nitrogen removal rate is less than 80%, it indicates that the incoming water continues to be toxic and needs to be reported immediately to take corresponding emergency treatment measures. This method is not suitable for the regulation of accident sewage plants whose incoming water is still toxic;

[0026] Step 2: Zoning regulation of biochemical reaction tanks: Generally, sewage treatment plants are operated in two or even groups, and biochemical reaction tanks are commonly operated in 2 or 4 groups. The main strategy of zoning regulation is to define half of the groups as Group A and the other half as Group B, with Group A being regulated first and Group B operating as usual. Generally, after the aerobic pool ammonia nitrogen treatment collapses, the entire biochemical pool still has a certain COD removal capacity, and zoning regulation can still retain the COD removal capacity of the non-regulated group, ensuring that the COD of the sewage plant meets or is close to the standard.

[0027] First, stop the water inlet and aeration of group A, close the external sludge reflow of group A and let it settle, and use an external pump to discharge the high-concentration sludge at the bottom of group A into group B nearby. The liquid level of group A biochemical pool will be reduced as a whole, and the liquid level will be reduced to 1 / 4-1 / 3 of the original pool capacity; start group A for short-term aeration, measure the sludge concentration of group A, and add sludge from an external source when the sludge concentration of group A is lower than 1000mg / L to increase the sludge concentration of group A to higher than 3500mg / L; after intermittent water inlet, group A is exposed to air, and the water inlet volume each time is 1 / 4-1 / 3 of the original pool capacity. High-quality carbon source needs to be added to make the COD of the inlet water 200-300mg / L. At this time, the operation mode of group A is batch type; after each intermittent water inlet of group A, The ammonia nitrogen concentration in the biochemical pool was tested. When the ammonia nitrogen concentration in group A dropped below 1 mg / L (this process generally requires 24 to 30 hours of exposure), water could be intermittently added again. Repeating this process 3 to 4 times, group A could be fully loaded. After the last water inflow, pool A was nearly full, the sludge concentration in pool A returned to normal (sludge concentration was greater than 4000 mg / L) and the nitrification activity was good. At this time, the daily processing capacity of group A was close to the full load state of group A. The high-quality carbon source was methanol, sodium acetate or glucose. After the commissioning group began to continuously flow water in, nitrifying bacteria were added to further enhance the nitrification activity of the aerobic pool, which was helpful for activity recovery and long-term operation. The amount of bacteria added was 200 g / m 3 .

[0028] During the entire debugging process of Group A, the external sludge recirculation of Group B was closed, the sludge discharge of Group B was increased, the sludge without nitrification activity was discharged, and the sludge concentration of Group B was reduced to below 3000mg / L; in the last cycle of intermittent water inflow of Group A, exogenous sludge was added to Group B, and the concentration of the added sludge was increased to make the sludge concentration of Group B above 6000mg / L, and the batch operation was carried out; before the last cycle of the batch water inflow of Group A, the water volume treated by Group B was the difference between the total water volume and the daily water inflow of Group A, and the treated water volume was greater than its designed water volume, and its treatment target was COD compliance; in the last cycle of the batch water inflow of Group A, the water volume treated by Group B was 100% of the designed water volume, and its treatment target was COD and ammonia nitrogen compliance; after the last batch water inflow of Group A was completed and the full load state was restored, Group B also reached its full load state, the external sludge recirculation was turned on, and the operation mode of Group A and Group B was changed to continuous flow, and then Group A and Group B worked in coordination and complementation to achieve continuous full load treatment;

[0029] The exogenous sludge comes from the dewatered sludge (water content 80%) from other urban sewage treatment plants. When the actual operating water volume of the sewage treatment plant is less than 50% to 70% of the designed water volume, the sludge from Group B can be returned from Group A to Group B for replenishment, thereby reducing the commissioning cost.

[0030] Step 3: Emergency regulation of chemical agents to ensure that the effluent meets the standards: During the debugging process, by zoning and debugging each group of biochemical pools and utilizing the treatment capacity of the undebugged group of biochemical pools, it is possible to ensure that the effluent COD meets the standards. However, there will be problems with excessive total phosphorus and ammonia nitrogen in the effluent. The phosphorus removal agent is added to the original deep phosphorus removal process unit, and the oxidant is added to the disinfection pool to achieve the removal of ammonia nitrogen and total phosphorus. Ammonia nitrogen can be removed by the breakpoint chlorination method, and the agent for the breakpoint chlorination method is sodium hypochlorite. The phosphorus removal agent can be specifically one of aluminum sulfate, aluminum chloride, polyaluminum chloride, ferrous sulfate, polyferric chloride sulfate, ferric chloride, polyferric chloride or calcium hydroxide, but organic phosphorus removal agents should not be selected.

[0031] The above method was applied to a wastewater treatment plant in Northeast China where the aerobic biochemical system failed. The plant was able to resume normal operation in a short period of time, and the effluent during the commissioning process still met the discharge standards. The total treatment capacity of the wastewater treatment plant is 2.5×10 4 m 3 / d, the actual operating water volume is about 1.6×10 4 m 3 / d, the main process of the biochemical unit is A 2 O process, there are two groups of biochemical treatment pools (Group A and Group B), the water retention time of the biochemical pool is 19.49h (2.19h in anaerobic section, 6.54h in anoxic section, 1.62h in anoxic-aerobic section, 9.14h in aerobic section). The changes of ammonia nitrogen removal in Group A during the debugging process are as follows Figure 3 shown.

[0032] After 74 hours of commissioning and the addition of auxiliary nitrifying agents, the aerobic sludge properties of Group A were good, the sludge settling ratio SV reached 35%, and it had excellent removal ability for ammonia nitrogen, and the effluent ammonia nitrogen concentration was less than 5 mg / L. Four days after the start-up of Group B, the ammonia nitrogen in the sewage effluent was less than 5 mg / L. Figure 4 shown.

Claims

1. A method for rapid recovery of nitrification activity after toxic wastewater impact in an AAO process urban sewage treatment plant is inhibited, characterized in that: The method is: Step 1: Incoming water quality analysis: Detect the COD, ammonia nitrogen, total nitrogen, total phosphorus indicators, pH, ORP, and heavy metal content of the incoming water to determine whether the incoming water quality is still toxic. Only after the incoming water is non-toxic can the zoning regulation begin; a simple method is to take the activated sludge from the aerobic pool of a normally operating urban sewage plant to treat the influent of the accident sewage plant. If the ammonia nitrogen removal rate is greater than 80% within 12 hours, it is determined that the influent of the accident sewage plant is currently non-toxic; Step 2: Zoning and regulation of the biochemical reaction pool: The biochemical reaction pool is divided into a regulation group and a non-regulation group. First, the water inlet and aeration of the regulation group are stopped, the sludge external reflow and sedimentation of the regulation group are closed, and part of the sludge of the regulation group is discharged to reduce the liquid level of the biochemical pool of the regulation group to 1 / 4 to 1 / 3 of the original pool capacity; Start short-term aeration of the control group. When the sludge concentration of the control group is lower than 1000mg / L, add sludge until the sludge concentration is higher than 3500mg / L. After intermittent water inflow, the control group is aerated. The water inflow each time is 1 / 4 to 1 / 3 of the original pool capacity. High-quality carbon source needs to be added to make the influent COD 200 to 300mg / L. At this time, the operation mode of the control group is batch mode. After each intermittent water inflow of the control group, the ammonia nitrogen concentration of the biochemical pool is tested along the way. When the ammonia nitrogen concentration of the control group drops below 1mg / L, water is intermittently inflowed again. Repeat several times to achieve full-load operation of the control group. After the last water inflow, the control group is close to full, the sludge concentration returns to normal level and the nitrification activity is good. At this time, the daily processing capacity of the control group is close to the full-load state of the control group. During the debugging process of the entire control group, the sludge external reflow of the non-control group was closed, the sludge discharge of the non-control group was increased, and the sludge without nitrification activity was discharged to reduce the sludge concentration of the non-control group to below 3000mg / L; in the last cycle of intermittent water inflow of the control group, exogenous sludge was added to the non-control group, and the sludge concentration of the non-control group was increased to above 6000mg / L, and the batch operation was carried out; before the last cycle of batch water inflow of the control group, the water volume treated by the non-control group was the difference between the total water volume and the daily water inflow of the control group. The treated water volume is greater than its designed water volume, and its treatment target is to meet the COD standard; in the last cycle of the sequential batch water inflow of the control group, the treated water volume of the non-control group is 100% of the designed water volume, and its treatment target is to meet the COD and ammonia nitrogen standards; after the last sequential batch water inflow of the control group is completed and the full load state is restored, the non-control group also reaches its full load state, and the sludge external reflow is turned on. The operation mode of the control group and the non-control group is changed to continuous flow, and then the control group and the non-control group work together to achieve continuous full-load treatment; Step 3: In the above zoning control process, if there is a problem of excessive total phosphorus and ammonia nitrogen in the effluent, the effluent is treated with breakpoint chlorination to remove ammonia nitrogen, and total phosphorus is removed by adding phosphorus removal agents.

2. The method for rapidly recovering the nitrification activity of a town sewage treatment plant after being subjected to toxic wastewater impact by an AAO process according to claim 1, characterized in that: In step 1, the judgment method is specifically to mix the activated sludge with the influent, and the treatment conditions are: continuous aeration is required to maintain the dissolved oxygen concentration of 2-5 mg / L, the mixing ratio should be close to the sludge-wastewater ratio of the normal sewage plant biochemical pool, that is, 2:3-8, the temperature is room temperature, and the effluent ammonia nitrogen is detected.

3. The method for rapid recovery of nitrification activity after toxic wastewater impact AAO process urban sewage treatment plant is inhibited according to claim 1, characterized in that: In step 2, for the biochemical reaction pools with 4 or more groups operating together, half of the groups are selected as control groups, and the remaining groups are debugged as non-control groups. The debugging method is the same as step 2.

4. The method for rapid recovery of nitrification activity after toxic wastewater impact AAO process urban sewage treatment plant is inhibited according to claim 1, characterized in that: In step 2, the high-quality carbon source is methanol, sodium acetate or glucose.

5. The method for rapid recovery of nitrification activity after toxic wastewater impact AAO process urban sewage treatment plant is inhibited according to claim 1, characterized in that: In step 2, after the commissioning group starts to continuously flow water, nitrifying bacteria are added at a dosage of 100-400 g / m 3 .

6. The method for rapid recovery of nitrification activity after toxic wastewater impact AAO process urban sewage treatment plant is inhibited according to claim 1, characterized in that: In step 2, the moisture content of the exogenous sludge is greater than 80%.

7. The method for rapid recovery of nitrification activity after toxic wastewater impact AAO process urban sewage treatment plant is inhibited according to claim 1, characterized in that: In step 3, the agent of the breakpoint chlorination method is chlorine gas or sodium hypochlorite; the phosphorus removal agent is one of aluminum sulfate, aluminum chloride, polyaluminum chloride, ferrous sulfate, polyferric chloride sulfate, ferric chloride, polyferric chloride or calcium hydroxide.

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