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Process detail management (VIII) in the treatment flow of the sewage plant-Operation details of the desanding tank

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Process detail management (VIII) in the treatment flow of the sewage plant-Operation details of the desanding tank

Sewage plantIn the pretreatment section, after the coarse and fine grille and the sewage lift pump are lifted, the inorganic particles in the sewage are removed in the grit chamber, so that the inorganic substances in the sewage entering the subsequent treatment structures are reduced to a lower level. The low inorganic substances entering the biological tank can increase the organic proportion in the activated sludge concentration in the biochemical tank, and the sludge concentration can be controlled within a reasonable range, the loss and wear of the equipment are well controlled. At the same time, the reduced inorganic substances can reduce the concentration of activated sludge, reduce the absolute number of residual sludge discharge, reduce the pressure of sludge dewatering, and reduce the drug consumption, energy consumption and transportation cost of the sludge workshop. ThereforeSand removal tankThe operation management of the sewage plant is also an important link to improve the overall management.

The main function of the sand removal tank is to remove inorganic sand particles with a particle size greater than 0.2mm. At this stage, the common forms of the grit chamber of the sewage plant are cyclone grit chamber, advote grit chamber, aerated grit chamber, etc. These types of grit basins use different methods to remove sand from sewage. The cyclone grit chamber mainly uses the different densities of water and sand particles in the rotation process. The high density sand particles (the relative density of 0.2mm sand particles is about 2.65mm) will be rotated to the bottom of the cyclone grit chamber, and the sewage will flow out from the upper part of the cyclone grit chamber, thus achieving the function of removing sand particles, set a longer grit chamber and keep a low flow rate to make the sand particles settle to the bottom of the grit chamber in the flow of water to achieve the purpose of removing sand particles; the aeration grit chamber is an improvement on the stratosphonic grit chamber, and aerates the precipitated sand particles by adding the perforated pipe aeration mode at the bottom, so as to make the sand particles rub against each other and clean the organic matter on the surface of the sand particles, in order to improve the concentration of organic matter in the influent, it also has a certain cleaning effect on the sedimentation sand, and the sand after aeration cleaning enters the sedimentation tank through the aeration turbulence plate for removal.

The removal principle of the grit chamber is relatively not very complicated, but how to remove the sand particles deposited at the bottom of the chamber has become a headache in the operation and management of the sewage plant. The above-mentioned several modes of grit chamber have their own different sand discharge problems, and these sand discharge problems are often the main factors that the operation and management of the grit chamber by the employees of the sewage plant is not in place.

The first is the cyclone grit chamber. The inorganic sand particles are precipitated into the central sand cylinder of the cyclone grit chamber by the centrifugal action of the rotating water flow, and then the sand is loosened by compressed air, and then the sand is switched to the sand lifting pipeline to carry out sand-water separation in the sand-water separator. In actual operation, loose sand and sand lifting are a compressed air pipeline, and then they are controlled to enter different pipelines through solenoid valves before entering the central sand cylinder. Most cyclone grit basins of sewage plants are exposed to the outside. The solenoid valves lack protective measures, resulting in failure of the solenoid valves due to sun and rain and cannot be switched. Operators often set to the automatic position and leave without carefully observing whether switching is implemented and whether sand is raised. Often because the solenoid valve is damaged, the valve for loosening sand or lifting sand cannot be opened, and only one step is completed, only loosening sand but not lifting sand or only lifting sand but not loosening sand, resulting in continuous accumulation of sand particles. Eventually, the sand particles silt up the central sand cylinder, unable to effectively lift the sand particles, and only water can be drained for artificial sand cleaning. Even the cyclone grit chamber of some sewage plants completely silt up, or no sand particles finally becomes a decoration. A recent 600000 environmental penalty for the long-term failure of the cyclone grit chamber to operate normally isSewage treatmentFrequent brush frequency in the industry, but also reflects this phenomenon is widespread.

However, the sand discharge method of the advection grit chamber and the explosion grit chamber is the same, and the sand suction pump placed on the sand suction crane sucks sand from the sand sink at the bottom of the tank. This way of sand discharge has a great influence on the debris interception effect of the coarse and fine grille of the front treatment structure. The debris that the coarse and fine grille fails to intercept, especially some debris containing flocculent, will weave a growing flocculent rope under the action of water flow. After the water flow enters the advection/aeration grit chamber, it will be sucked into the impeller by the sand suction pump, and the impeller will be wound, as a result, the sand suction pump cannot lift the sand grains at the bottom to the sand discharge tank, which will seriously burn the sand suction pump. Some sand suction pumps even use the blade structure of the impeller, but with the wear of the blade, it will eventually be wound and blocked. The reason here is not the choice of the form of the sand suction pump or the adjustment of the installation height of the suction port of the sand suction pump from the bottom of the pool, but more the influence of the interception effect of the front equipment (coarse and fine grille). Therefore, in the sewage plant, the systematic consideration of each link is the way to solve the abnormal problems in the operation of the process. It is often not the best solution to find the problems on the failed structures.

In addition to the above problems, the grit chamber in some areas cannot intercept sand at all, but the MLVSS proportion in the sludge concentration in the biological tank is extremely low. This is mainly because the grit chamber with standard design at this stage mainly removes 0.2mm sand. If the inlet inorganic sand particle size is less than 0.2mm and the relative density is less than 2.5mm, it cannot be effectively removed by the grit chamber, the inorganic components of the activated sludge in the biochemical section increased.

As a control treatment structure for the organic proportion of activated sludge, the grit chamber is very necessary for its good management. In daily management, the following aspects should be paid attention:

1, according to the water quality of the inlet water, regularly open the sand discharge system. The proportion of sand particles is relatively large, and excessive accumulation of sand particles will cause siltation, resulting in the sand discharge system can not effectively discharge sand particles, so it is necessary to discharge sand in time, so that excessive accumulation of sand particles can not be discharged, resulting in more serious consequences. Especially in areas with relatively large wind and sand, during the rainy season in areas where rain and sewage confluence, the sewage plant with construction drainage shall adjust the operation of the grit chamber in time according to the water inflow situation to ensure that the inorganic sand particles in the water inflow are removed in time.

2. Maintenance of equipment. Most of the equipment in the grit chamber is in the open air, and some electrical components exposed to the outside are easily eroded by the weather, resulting in damage to the electrical components. Patrol personnel should find and repair them in time. The untimely maintenance and repair of the equipment should not cause the poor function of the facilities and eventually cause the loss of the functions of the facilities. In some sewage plants, this kind of situation is still quite common. If the equipment is damaged, it is no problem to repair it a few days later. It has been seriously delayed for several months, so the process problems caused are still strange.

3, from the system point of view to consider the function of facilities and equipment. The blockage of the sand suction pump cannot be considered only from the perspective of the sand suction pump. It is necessary to consider whether the interception effect of the grille is in place. Systematic solution to the monomer problem is the way to solve the root of the problem. The role of the coarse and fine grille should be carefully inspected on a daily basis to comprehensively improve the operation effect of the pretreatment system.

4. Reasonable selection or transformation of facilities and equipment should be carried out according to the size of inorganic particles in the actual water inflow. For the equipment that cannot produce sand for a long time, the transformation and upgrading of sand removal mechanism should be carried out. In particular, in some urban sewage plants with serious desertification, there are a large number of sand particles below 0.2mm, but they cannot be effectively removed. Therefore, it is necessary to optimize and transform the grit chamber. Now there are also optimization facilities, the removal effect of small particle size sand is improved.

Generally speaking, the importance of the grit chamber in the sewage plant is beyond doubt, but its role is often unsatisfactory. The daily operation management of the grit chamber needs to be improved and strengthened by the operators to ensure the stable performance of the process function of the grit chamber.