抄録
A mathematical model simulating the extended aeration activated sludge process was presented.According to the model, the production rate of the sludge and the content of active biomass in the sludge, which depend on operation conditions, are quantitatively analyzed through illustrative calculations.
The concentration of active biomass in the aeration tank decreases abruptly with increase of the apparent mean retention time of liquid in the tank under a constant discharge rate of excess sludge from the system. While the discharge rate of excess sludge does not affect much on the fraction of active biomass in total suspended solids in the tank operating as the standard activated sludge process with of around 0.1 day, the high discharge rate of sludge increases considerably the fraction of active biomass under the extended aeration condition with of around a day.
Although a constant concentration of the active biomass in the tank can be maintained without discharge of the sludge, the mass of total suspended solids increases continuously in such operation.The accumulated suspended solids consist mostly of nonbiodegradable solids in the influent and those produced from the self-oxidation of the active biomass.
