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6.
4.
1 Nitrogen and Phosphorus Removal Process in Newly-built Wastewater Treatment Plant
(1) The nitrogen and phosphorus removal effect of Kunming Lanhuagou Wastewater Treatment Plant is shown in Table 6-3
.
Table 6-3 Concentrations of total nitrogen and total phosphorus in the inlet and outlet water of Kunming Lanhuagou Wastewater Treatment Plant
(2) The process parameters and treatment effects of Guangzhou Datansha Wastewater Treatment Plant are shown in Table 6-4 and Table 6-5
.
Table 6-4 Process parameters of Guangzhou Datansha Wastewater Treatment Plant
Table 6-5 Operation effect of Guangzhou Datansha Wastewater Treatment Plant
6.
4.
2 Modification process for nitrogen and phosphorus removal in traditional sewage treatment plants
According to the mechanism of urban sewage denitrification and phosphorus removal, three conditions must be met to transform a traditional plug-flow sewage plant into a sewage plant with the function of nitrogen and phosphorus removal:
①Sufficient carbon source necessary for the denitrification and phosphorus removal reaction process shall be provided;
②To provide the necessary reaction volume for the denitrification and dephosphorization reaction process;
③Provide anoxic, anaerobic and aerobic environment necessary for the reaction process of ammonia and phosphorus removal
.
Transform the existing urban secondary sewage treatment plant into a sewage plant with the function of nitrogen and phosphorus removal, which can be expanded by land acquisition, that is, new structures are added, and the traditional activated sludge method push-flow aeration tank is changed to the A 2 /O method , A / O method, MSBR the like
.
However, as the urbanization process becomes faster and faster, there is no land available for requisition near the wastewater treatment plant, or the land requisition fee is too expensive, so land acquisition and expansion are too expensive or unrealistic for most wastewater treatment plants
6.
4.
2.
1 Adjust process parameters
Increasing the concentration of activated sludge in the mixed liquor can be achieved by increasing the reflux ratio of activated sludge
.
That is, the organic load is reduced, the age of the sludge is prolonged, and it is beneficial to the growth of nitrifying bacteria
In response to the problems of overloading of the secondary sedimentation tank and excessive suspended solids in the effluent after increasing the sludge concentration, the Shanghai Drainage Company and Tongji University proposed a high-concentration multi-stage activated sludge method improvement process, which was implemented in Shanghai Sitang Sewage Plant Pilot test of one and a half years
.
The traditional plug-flow aeration tank is divided into multiple areas, each area is connected in series, and baffles are set to make each area have a certain function of intercepting and thickening the sludge, which significantly increases the average sludge concentration in the reactor without increasing The hydraulic load and solid load of the secondary settling tank have been tested to achieve good denitrification and phosphorus removal effects
In addition, a composite activated sludge treatment system composed of a certain amount of suspended fillers added to the aeration tank of the traditional activated sludge method can increase the sludge concentration in the aeration tank, thereby enhancing the system’s ability to treat COD and ammonia nitrogen.
The removal ability
.
In the suspended filler activated sludge system, nitrifying bacteria with a long generation time adhere to the suspended filler and are not easy to lose.
6.
4.
2.
2 Adjust operation mode
Domestic scholars have proposed the "inverted A/A/O process", "synchronized A/A/O process", and "sequential A/A/O process" for the transformation of traditional wastewater treatment plants for nitrogen and phosphorus removal.
Tried a productive experimental study, and achieved a better effect of denitrification and dephosphorization
.
The inverted A/A/O process is to reverse the anaerobic zone and anoxic zone of the traditional A 2 /O process, that is, anoxic zone, anaerobic zone, and aerobic zone.
The internal return flow of sludge is cancelled and the external return flow ratio is controlled.
Between 100% and 200%
.
The technological process is simpler and more energy-saving
6.
The addition of iron salt , aluminum salt and other coagulants and organic polymer coagulants can strengthen the primary treatment system, which can further remove organic matter, total phosphorus, and SS in the sewage, but the removal of nitrogen is not obvious and the operation and management are troublesome.
6.
For example, the scale of part of the treatment is reduced, the hydraulic retention time is appropriately extended, and the treatment structure is appropriately modified to achieve the goal of nitrogen and phosphorus removal
Related links: New technologies and new processes for biological nitrogen and phosphorus removal from sewage (2)