The ammonia nitrogen level in the effluent is above the standard
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CAST process: Influent COD 60, BOD 50. The ammonia nitrogen level in the incoming water is around 15. The sludge concentration in the three tanks is just over 1,000, with an SV percentage of around 2%. In one tank, the sludge concentration was over 4000, with an SV value of 10%. While the ammonia nitrogen level in the effluent from that tank with high sludge concentration was within the acceptable limits, it exceeded the limits in the other three tanks. The aeration time is one and a half hours. How can the three tanks with excessive ammonia nitrogen levels in the effluent be brought back within acceptable limits? Also, as for how to cultivate the sludge, glucose has been added, and sludge from tanks with high concentrations has been transferred to tanks with lower concentrations. Everyone, please help think of a solution.
The method to reduce ammonia nitrogen in the effluent is to increase aeration in the presence of nitrifying bacteria, which allows the ammonia nitrogen level to be reduced to near 0. The optimal environment for nitrifying bacteria is one with a long sludge age (over 20 days) and water temperatures between 15–30°C. Increasing the amount of sludge will prolong the sludge age; your approach is correct ； Increasing dissolved oxygen is also a necessary condition; moreover, raising dissolved oxygen simultaneously reduces the concentration of organic substrates, which is also an essential means to enhance nitrification.
In this case, whether the CAST process is appropriate becomes a question. With low COD and high sludge concentration, sludge aging becomes a problem; increasing aeration levels will lead to a significant reduction in sludge volume, and it becomes even more difficult to cultivate nitrifying bacteria. It’s not very economical to add large amounts of glucose in order to feed enough sludge. It is recommended to consider other nitrogen removal methods, such as chemical dosing or aerated filters. Personal opinion, for reference only.