Ozonation in sequencing batch reactors for reduction of waste solids.

The objective of this research was to study a process modification for reducing the mass of waste sludge from sequencing batch reactors (SBRs) by promoting the use of intracellular products released by ozonation of the biomass. For this purpose, biomass generated in laboratory-scale SBRs was exposed to ozone (O3) as a cell-lysing agent to partially solubilize intracellular material. The results indicated that the application of low doses of ozone reduced the mass of waste sludge production by an average of 29%. This positive aspect of the process was achieved using an average daily ozonation rate of 0.0106 mg O3/mg TSS x h, with slightly less than 2 hours of ozonation per cycle with 3 cycles per day. In addition, the short-term settling characteristics of the ozonated biomass were observed to have improved. A negative aspect of the ozonation process resulted in decreased effluent quality, as determined by measured increases in the soluble chemical oxygen demand, total Kjeldahl nitrogen, and total phosphorus concentrations of reactor effluent.