The growth rate of slime bacteria is limited when the attaching surface becomes completely covered with one layer of cells. At this point, the increase in mass of organisms shifts from logarithmic to linear with respect to time. A second growth limiting factor occurs when the thickness of the slime mass exceeds the limiting thickness for the diffusion of oxygen. From this point on, the rate of oxygen consumption will remain constant with respect to time. The maximum rate of nutrient removal from the substrate will occur when the slime thickness equals the limiting thickness for the diffusion of oxygen.