Which of the following is a key control for an activated sludge basin?

A key control for an activated sludge basin is alkalinity. In the activated sludge process, alkalinity plays an essential role in maintaining the proper pH balance for microbial activity. Microorganisms require a suitable environment for optimal growth and metabolism, which is significantly affected by the concentration of alkalinity in the system. Alkalinity helps to neutralize acids that may be produced during microbial metabolism and aids in buffering the system against changes in pH. Maintaining adequate alkalinity ensures that the pH remains within a range conducive to effective nitrification and overall system performance.

While nitrogen concentration, temperature regulation, and pH balance are also important factors in the operation of an activated sludge basin, they do not directly influence the buffering capacity and stability of the pH level in the same foundational way that alkalinity does. Keeping an eye on alkalinity helps in maintaining overall system health and can prevent issues related to acidic conditions that might hinder the treatment process.