How long can the activated sludge remain at rest in the aerobic activated sludge process
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Hello, experts. I am currently working in operations. The wastewater treatment plant uses a three-effect evaporation + MBR process, with the units operating for 15 days before being shut down for a month, and this cycle repeats continuously. When the system is running, aeration in the MBR tank is active 24 hours a day. When the system is shut down, aeration operates for 2 hours and then stops for 2 hours, in this cycle. I’ve done some research, and it turns out that aerobic activated sludge can survive without aeration for over 2 weeks. I would like to ask whether, during the 1-month period when the system is not in use, it’s possible, with proper operation, to run the aeration system just twice in order to prevent too much loss of activity in the activated sludge
No, I think it’s necessary to aerate at least once a day. A small amount of water should also be added to supply nutrients, and the water quality needs to be changed as well. Aeration should be carried out every half month; once the water inside becomes dark and smelly, it becomes difficult to restart the process
Your goal is to ensure that the wastewater treatment facilities can quickly meet the requirements for treating wastewater once they are restarted, and to reduce energy consumption and labor costs when no wastewater is incoming； Suggestions: 1. It is still necessary to aerate once a day; otherwise, anaerobic conditions will arise, which is not conducive to the operating conditions required for the next startup ； 2. To ensure the survival of bacteria, it is necessary to meet their survival conditions, namely dissolved oxygen and food; nutrients (C/N/P) need to be replenished regularly ； It is also possible to discharge a portion (1/3) of the wastewater in the biological tank before shutting it down, and then fill the tank with raw water again; this can reduce the costs associated with adding nutrients ； 3. Dissolved oxygen can also be replenished using reflux.