Holistic sludge management through ozonation: a critical review

This paper critically reviews the multidimensional benefits of ozonation in wastewater treatment plants. These benefits include sludge reduction, removal of emerging trace organic contaminants (TrOC) from wastewater and sludge, and resource recovery from sludge. Literature shows that ozonation leads to sludge solubilisation, reducing overall biomass yield. Sludge solubilisation is primarily influenced by ozone dosage, which, in turn, depends on the fraction of ozonated sludge, ozone concentration, and sludge concentration. Additionally, sludge ozonation facilitates the removal of TrOCs from wastewater. On the other hand, by inducing cell lysis, ozonation increases the chemical oxygen demand (COD) and nutrient concentration of the sludge supernatant, which deteriorates effluent quality. This issue can be resolved by implementing resource recovery. Thus far, successful retrieval of phosphorous from ozonated sludge supernatant has been performed. The recovery of phosphorous and other resources from sludge could help offset the operation cost of ozonation, and give greater incentive for wastewater treatment plants to adapt this approach.