What is the relationship between organic matter degradation by activated sludge process and nutrients? What should I do if I am undernourished?

Activated sludge process, also known as sbr process and sequencing batch activated sludge process, is easy to treat sewage with complex water quality, and the values of cod and bod should not be too low, which is not conducive to the reproduction and growth of microorganisms. The author has encountered sewage with cod lower than 80 and sewage with COD lower than 150(mg/l), but the treatment effect is poor because microorganisms cannot be cultivated (the organic content is too low to maintain the basic nutritional reproduction needs of microorganisms). Of course, there are other factors, such as c/n ratio, sludge concentration, water temperature, aeration time and so on, which cannot be generalized.