The ultimate disposal of biosolids has been and continues to be one of the most expensive problems faced by wastewater utilities. Previous work has shown that the waste sludge generation in an activated sludge plant can be reduced by promoting cryptic growth conditions (i.e., biomass growth on intracellular products). For this purpose, excess biosolids from a continuous flow activated sludge system were solubilized using ozone as the cell lysing agent, and then returned to the aeration tank. The results of these preliminary studies indicate that the proposed process configuration has the potential to reduce the waste sludge production by 40% to 60%. In the present research, the details of the ozonation process is further investigated to determine the maximum solubilization efficiency. For this purpose, a number of variables such as the solids concentration in the excess sludge, ozonation time, and ozonation dosage rate are studied.

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