An emerging application for ozone use in wastewater treatment is the reduction of sludge generation from the activated
sludge plants. Sewage plants must dispose of their excess sludge. To do so, additional processing of the sludge is
required including filtration and dewatering. In some cases, the sludge must be disposed of in landfills where the plant
operator must pay for hauling and disposal costs. Eliminating this excess sludge can be economically interesting
depending if the amount of ozone per ton of sludge removed is low enough.
In this process ozone is fed into a side stream of sludge that is be recycled back to the activated sludge tanks.
The ozone attacks the cell walls of the bacteria that make up the activated sludge causing the cells to undergo lysis.
Lysis is a process where the cellular wall is breached and the internal materials leak out of the cell.