The sewage treatment process adopts China's more advanced CAST (CAST) process technology, the operating system adopts the centralized control of the computer, remote operation, monitoring and alarming of the entire process. After the formal operation of the sewage treatment plant, the city's 20 square kilometers of sewage within the scope of all can be recycled. CAST process is a kind of "filling and draining" activated sludge method, wastewater treatment according to a certain cycle cycle, CAST process is an improved type of SBR process, each cycle has the following segments: filling/aeration, filling/sedimentation, skimming, idle. Each stage consists of a cycle, and constantly repeat the cycle, at the beginning, due to water filling, the water level in the pool from a minimum water level began to rise, after a certain period of time aeration and mixing, stop aeration, so that the activated sludge for flocculation and precipitation in a static environment, in the completion of the precipitation stage, a mobile skimming weir discharge has been dealt with supernatant, so that the water level down to the pool set the minimum water level The whole process is then repeated.
The purpose of the commissioning of the sewage treatment plant project is to ensure that the treatment structures, mechanical and electrical equipment, pipeline network in the state of load can run normally, a comprehensive test of the entire system process performance to meet the design requirements, optimize the operating parameters, and find problems in time for the sewage treatment plant to put into operation to make full preparations for the formal operation of the plant. The activated sludge culture adopts the continuous bacterial cultivation method. Continuous bacterial cultivation method can be closely integrated with the normal operation of the system, to achieve the activated sludge culture and domestication and startup operation synchronization, a high degree of automation, in the activated sludge culture at the same time can be further combined with the automatic control of the trial run, but the activated sludge cultivation period is a little longer. The CAST process tank was filled with sewage, and then the water inlet was stopped, the aeration equipment was turned on for aeration, the aeration time was 6 h~8 h, sedimentation was 1 h, and the water was discharged for 40 min. 3 days later, the aeration time was changed to 2.5 h, and the rest of the tank was operated in accordance with the normal design operation process. The sludge was found to be cultivated in the tank in about 2~3 weeks. The results of biomicroscopy: ciliates were dominant and the structure of the floc was relatively loose. At this time, the sludge mass concentration in the mixture reached about 4,000 mg/L. The sludge was then continuously fed and aerated. After that, continuous water intake and aeration were carried out, and normal sludge discharge was started. in the middle of May, the process cycle was adjusted: aeration was carried out at 0.5 h of water intake, 2.5 h, sedimentation was carried out for 1 h, decantation was carried out for 1 h. At this time, the sludge mass concentration was already more than 5 000 mg/L. The sludge was successfully cultured in late June, and the results of microscopic examination showed that the floc was enlarged with a compact structure, and there were a large number of ciliated worms and ciliated worms. Water quality test: the COD, SS and phosphate of the effluent reached the design standard of effluent (Class B standard of GB 8978-1996 Comprehensive Sewage Discharge Standard), and the SV30 was about 28%. The graph on the right shows the removal rate of organic matter (the design requires the removal rate of organic matter to be above 85%). During the activated sludge incubation period, the dissolved oxygen was controlled at 2 mg/L, the temperature was around 15℃, and the pH was around 7.