In the activated sludge process, we "activate" the sludge by accumulating a
high concentration of biomass through sludge settling and recycle. You analyze
the biomass in an activated sludge process and find that its total biomass
concentration is 3,000 mg/1 as volatile suspended solids, which is the same
as organic dry weight. Your bacteria are well represented by cocci having a
diameter of 0.8 J,lm, 80 percent water content, and 90 percent organic matter
in the dry weight. If the total number of metabolically active bacteria is
4 . 1013/1, what fraction of the total biomass is active bacteria?