01
To determine the cause of sludge poisoning after a poisoning event occurs in the biological treatment system, in order to avoid further escalation of the situation, we can learn from the observation of traditional Chinese medicine and observe the "clinical manifestations" of traditional Chinese medicine when determining whether the biological system is poisoned. Sensory, physical, chemical, and special methods are used to analyze and determine their 'causes'. 1. Sensory index analysis: Aeration tanks and final sedimentation tanks are the treatment structures of sewage treatment plants, and their operation can reflect the microbial characteristics of biological treatment systems. In the aeration tank, a large number of flocculent sludge particles can be observed with the naked eye, which are called activated sludge flocs. Each flocculent substance contains thousands of active microorganisms. During on-site inspections, operational inspectors can regularly observe the "surface" of activated sludge. Just like in traditional Chinese medicine, we should start with "seeing and smelling". First, the observation and analysis of the aeration tank from the aspects of color, smell, foam, flow pattern, transparency and other major items can quickly determine whether the biochemical system is poisoned with the shortest time, which is conducive to the management and technical personnel to quickly take measures to avoid further expansion and change of the situation. 2. Normal state When the aeration tank operates normally, the activated sludge is generally yellowish brown with a slight unfashionable smell. In the process of oxygenation, the normal aeration foam is dispersed in the aeration tank in a small amount. The total area is about 1/10. You can hear the rustling sound of the aeration tank. Foam is milky white. The final liquid level state of the pool is also closely related to the normal operation of the entire system. Attention should be paid to observing the level of the mud surface, the transparency of the upper clearance, the presence of mud, and the size of mud particles. When the final sink is running normally, the upper liquid is clear and transparent, and the activated sludge settles well. 3. Poisoning state At the initial stage of microbial poisoning in the biological treatment system, the operator found that the activated sludge in the aeration tank generally changed from yellow to soil, foam turned yellow, and the number of individuals increased, accounting for 30%~50% of the pool surface area. The clear liquid on the final sedimentation tank is turbid, the concentration of mud and water increases, and a small amount of SS is discharged from the effluent. In the middle and later period, the operators found that the activated sludge in the aeration tank generally changed from brown to black, and the number of foam increased sharply, accounting for more than 90% of the tank surface area. There are a lot of flocs in the effluent of the final sedimentation tank, the sludge structure is loose, the volume expands, and a lot of mud blocks formed by foam are floating on the surface, so the sedimentation performance of the sludge is poor. After receiving the abnormal water quality report from the operator, technicians should also compare it with the COD, ammonia nitrogen, total nitrogen and other data from online instruments. In general, the water quality indicators of the effluent after poisoning will undergo abnormal changes and show a linear relationship. 4. After receiving an abnormal situation report from the operation inspector, the management personnel of the sewage treatment plant usually immediately request the technical personnel of the water quality laboratory to conduct laboratory analysis on the frequency of the biological system water and mud samples, observe the biological phase of the activated sludge, and monitor the activated pollution. Mud oxygen consumption rate, DO, Further physical and chemical analysis of measures such as sludge settling rate, sludge volume index and density index, and sludge settling rate can roughly determine whether the microorganisms in the biological system are poisoned, the degree of poisoning, and the process of microbial changes in activated sludge. This analysis takes a long time, usually 2-3 hours, but the reliability of the data is high. Generally, the degree of purification of wastewater and the state of activated sludge can be determined. It is the foundation of emergency control for the biochemical system of sewage treatment plants. 5. Special analysis of heavy metal indicators
5. Special analysis of heavy metal indicators: Heavy metal analysis equipment is relatively expensive and generally not equipped in sewage treatment plants. When necessary, sewage treatment plants can extract sewage and sludge samples and send them to national standardization laboratories (urban drainage monitoring stations) for special analysis of heavy metal indicators, similar to doctors in general hospitals requiring special patients to undergo special examinations in large hospitals. The final data is used to confirm the authenticity and reliability of sensory examination and physicochemical analysis results. After microbial poisoning occurs in the biological system of sewage treatment plants, heavy metal specific analysis can be performed on water and mud samples to obtain accurate data. This process usually takes the longest time, 1-2 days, but data is the most accurate to determine whether the biochemical system is poisoned, what types of heavy metals enter, how much and to what extent. At the same time, it is also used to verify the accuracy of the above two-step analysis. Usually, such monitoring data is reported to higher-level departments and environmental protection supervision departments as the basis for biochemical system poisoning.
02
After the occurrence of poisoning symptoms in the biological treatment system, the first step is to observe the phenomenon and use physical and chemical analysis methods to determine that the cause of poisoning is due to excessive heavy metals in the influent. To deal with the disease, emergency plans should be quickly activated and effective control measures should be taken to prevent the situation from further expanding. Wastewater treatment plants typically adopt external and internal measures to treat them, as described below. 1. External measures: 1. Report abnormal water quality to superiors. When the sewage treatment plant discovers abnormal inflow, it shall activate the emergency plan for abnormal water quality and immediately report the relevant situation to the higher-level competent department and environmental protection department in the jurisdiction. 2. Investigation of pollution sources in the jurisdiction: After the sewage treatment plant reports abnormal water quality to the higher authorities, personnel should be arranged to conduct 24-hour sampling of the inlet and outlet of the pump station outside the plant. Organize pipeline personnel to sample the sewage from the external pipeline network multiple times, and based on the characteristics of abnormal inflow, focus on investigating and sampling the pollution sources, especially the sewage from large polluting enterprises, to determine the specific pollution sources, grasp first-hand information, and provide a basis for factory production regulation. 3. Cooperate with the Environmental Protection Bureau to supervise the sewage treatment plant, actively seek the support of the environmental protection bureau under its jurisdiction, provide strength to cooperate in carrying out supervision and inspection work, stop enterprises from exceeding discharge standards, and restore the inflow of water to the sewage treatment plant as soon as possible, in compliance with relevant standards. This has laid a solid foundation for the internal process control of sewage treatment plants. 2. Internal measures: While taking external measures, sewage treatment plants should develop corresponding emergency plans based on abnormal inflow water quality, and make targeted adjustments and controls to the biological treatment process of sewage to prevent the situation from further expanding. 1. After an abnormal water inflow event occurs, control the water inflow of the inlet pump room, and use smaller or intermittent water inflow according to the degree of abnormality. While ensuring that the sewage in the pipeline does not overflow, try to reduce the water inflow as much as possible to prevent high concentrations of toxic and harmful substances from entering. The microorganisms in the biochemical system are further poisoned by toxic pollutants, which prolongs the recovery process of the biological system. 2. Increase the frequency of water quality testing. After abnormal water intake incidents occur, the frequency of water quality testing should be 1-3 times a day. We should strengthen the observation of the biological stage of the air exposure pool to provide more data on the water quality of the entire process, thereby promoting the adoption of more scientific processes. Control measures. In water quality testing, attention should be paid to observing the amoebas, flagella, and rotifers inside the rotifers, which indicate activated sludge poisoning, biological disintegration, recombinant insects, nematodes, and other protozoa that show normal and good organisms with activated sludge. Change. 3. Reduce reflux and increase sludge discharge. After the occurrence of abnormal inflow events, while reducing inflow, the sludge reflux rate should be reduced, and the discharge time of inert sludge in the final sedimentation tank should be increased to further reduce the residual toxic sludge in the final sedimentation tank returning to the aeration tank. Properly reduce the sludge concentration in the aeration tank, separate or discharge pollutants from wastewater, control sludge expansion and floating, and minimize the risk of poisoning. 4. Microbial domestication and cultivation of activated sludge
After implementing the above measures, in cases where the degree of poisoning is not severe, the aeration tank can be controlled by intermittent inflow and intermittent aeration, and the DO of the aerobic tank can be maintained at 2-3 mg/l to promote the growth of activated sludge microorganisms. After the formation of obvious activated sludge flocs by microorganisms, the operation mode of the aeration tank can adopt continuous inflow and continuous aeration, and the opening of the blower can be changed to maintain the DO of the aerobic tank at 2-3 mg/l. By increasing the reflux rate and reducing sludge discharge, the MLSS of the aeration tank can be increased to 2500-3500 mg/l, and the SVI of the mixed gas can be increased to 60-100 mg/l. If a large number of protozoa (such as nematodes) and a small number of post protozoa (such as rotifers) are observed in the activated sludge, the domestication and cultivation of activated sludge are basically successful, and the biochemical system returns to normal.
5. If the same type of sludge is severely poisoned, some activated sludge extracted from the nearest activated sludge treatment plant can be introduced and cultivated in the aeration tank to accelerate the recovery of the plant biochemical treatment system. After microbial recovery and water quality characterization, the inflow gradually opened up, but the inflow was slow. After the environmental protection department provided feedback on the pollution source, sampling analysis and monitoring continued. After the microbial system returns to normal and the water quality characteristics are restored, normal operation will resume.
6. After the situation is under control and the emergency task is completed, the sewage treatment plant should promptly summarize the accident, analyze the cause of the accident, prepare an accident analysis report, identify weak links and make improvements to prevent similar accidents from happening again.
7. Preventive measures: Although sludge poisoning in sewage treatment plants is rare, due to its suddenness, high harm, and difficulty in detection, it should be highly valued by sewage treatment plant management personnel, technical personnel, and operators. Regular drills should be conducted for such accidents to familiarize all personnel with the measures for handling them.
