: One of the most effective methods used in the biological treatment of a wastewater is the activated sludge process. The importance of the biological kinetic parameters determination is clearly illustrated by the fact that it is usually used in designing such systems. The present study aims to depict the problems faced during the experimental work of determining the bio-kinetics and their causes with an attempt to find proper solutions for them. A completely mixed continuous flow bench scale reactor was operated to determine the biological kinetic for municipal wastewater, during which the generated problems were depicted and solved. It was found that the most common affecting problems were sludge bulking in the final clarifier, followed by rising sludge, filamentous bacteria, settlement of biomass at the bottom of the aeration tank, and finally low biomass activity either immediately after acclimation or after steady state was reached. Solutions were recommended for each problem having continuous monitoring of several parameters at the reactor as their base. Despite the fact that different problems and their solutions have been introduced in this paper, there is no guarantee that all problems are covered. However, one can benefit from what is available.