To evaluate the active of activated sludge by ATP (adenosine triphosphate)

Dear all, 1.The active of activated sludge could evaluate by OUR (oxygen uptake rate), or to the level of microorganism, by evaluate the change of ATP value, or the gene mapping by NGS (next gen sequencing ). 2. If we choose the value of ATP,  to evaluate the active of activated sludge ,and investigate the reasons, such as operation parameters, DO, pH value, or the inflows,  and to do something in advance, any view or experiencecan offer? 3.thank a lot.